Power Tranformer Standarization Manual

POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 1 Technical Specification & Parameters

Working Group Members Mr. P. Ramachandran - ABB Ltd. Mr. M. L. Jain

- EMCO Ltd.

1

2

POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

CHAPTER - 1 TECHNICAL SPECIFICATION & PARAMETERS INTRODUCTION: 1.

Ratings, Voltage Ratio, Tapping range, Impedance and other technical parameters may be selected as per CBIP Publication No. 295, Manual on Transformers, 2012.

2.

This Manual gives the recommended losses for the standardised ratings of power transformers (Annexure - 1.1). Two ranges of losses are given - High Losses (for maximum specific loadings of current density 3A/mm2 and flux density 1.7 T at rated tap) and Low Losses (for maximum specific loadings of 2.3 A/mm2 and flux density of 1.6 T at rated tap). Current Density refers to all taps and flux density refers to at rated tap and voltage. Low losses may be adopted where the capitalization rates are high (say ` 2 lakhs per no-load loss kW and ` 1 lakh per load loss kW) and high losses where low capitalization rates are applicable (say ` 1 lakh per no-load loss kW and ` 0.5 lakh per load loss kW). When fixed maximum losses are specified, transformer buyers need not capitalize the losses for bid comparison. With fixed losses and using standardised GTP, buyers can compare various bids effectively and expeditiously. They can compare quoted weights of active materials with standardised losses. Indicated stray losses and type of conductors (rectangular conductor Vs continuously transposed cable – CTC) can be compared. Hardness of conductor and epoxy coated CTC gives an indication of short circuit withstand strength of winding.

3. Where the buyer wants losses different from the above standardised losses, he may get losses from reliable vendors after indicating the loss capitalization rates or maximum specific loadings. After evaluating the market losses, fixed losses for the special duty transformers may be decided and bids may be invited for the fixed losses. 4. The GTPs are prepared in two parts. One is to be specified by buyer and other by vendor. The tick mark ‘ √ ’ is shown in the column indicate by whom the data is to be filled in. 5. Ratings are also standardised covering 132 kV and above and up to 765 kV class transformers and accordingly considered in this manual (Annexure - 1.2). 6.

List of applicable standards for transformer is enclosed for ready reference (Annexure - 1.3).

Guaranteed Technical Particulars for Power Transformers A. GENERAL Item

Description

1

General Information i) Supplier ii) Manufacturer iii) Place of Manufacture iv) Type of Transformer (Core/Shell)

2

3

 Unit

Specified (by Buyer)

Offered (by Vendor)

√

Applications i) Indoor/Outdoor ii) 2Wdg/3Wdg/Auto iii) GT/Step down/ICT/Station Start up/Auxiliary/Rail Trackside Supply

 

Corrosion Level at Site i) Light ii) Medium iii) Heavy iv) Very Heavy

 

√

√

3

4

POWER TRANSFORMER - STANDARDISATION MANUAL

Item

Description

 Unit

4

Applicable Standards i) IEC: 60076 ii) IS : 2026 iii) ANSI C57.12.00

 

Type i) Liquid Immersed ii) Dry

 

6

Full Load Rating (HV/IV/LV)

MVA

√

7

3 Phase/Bank of Three Phase/Single Phase ( A,B,C)

 

√

8

Rated No Load Voltages (HV/IV/LV) Currents (HV/IV/LV)

kV Amp

√

9

Rated Frequency

Hz

√

10

Connections and phase displacement symbols (Vector Group)

 

√

11

Weight Schedules (Maximum) / (Minimum with no negative tolerance)

 

           

i) Active part

kg

√

ii) Oil

kg

√

iii) Tank and Fittings

kg

√

iv) Total Weight

kg

√

v) Overall dimensions L x B x H

mm

√

vi) Size of heaviest package L x B x H

mm

√

vii) Weight of heaviest package

kg

√

5

11.a 12  

Specified (by Buyer)

√

√

√

Transport Limitation LV Winding i) Stabilizing tertiary (Yes/No)

Offered (by Vendor)

   

√ √

ii) Loaded (Yes/No) 13

Tappings

 

         

i) OLTC/OCTC

 

√

ii) Tappings on

 

√

iii) Variation on

 

√

iv) Range of variation

%

√

v) No of Steps

 

√

vi) Parallel Operation Requirements

√

14

Impedance and Losses

 

 

i) Calculated I2R Loss at rated tap and 75 0C

kW

√

 

ii) Eddy current and stray loss at rated tap and 75 0C (indicative)

kW

√

 

iii) Calculated Load Loss(I2R+Eddy and Stray)at rated tap and 75 0C

kW

√

 

iv) Guaranteed Load loss at rated tap and 75 0C (Max)

kW

√

POWER TRANSFORMER - STANDARDISATION MANUAL

Item                    

Description

 Unit

Specified (by Buyer)

Offered (by Vendor)

HVIV √

HVLV √

IVLV √

√

√

√

v) Guaranteed Impedance (Base MVA at Principal tap) Tolerance

% %

vi) Impedance at extreme tappings a) Max. Voltage tap b) Min. Voltage tap Tolerance

% % %

√ √ √

vii) Regulation at full load 0.8 pf at 75 0C winding temperature

%

√

viii) Guaranteed No Load Loss (Max)

kW

ix) Calculated Fan Loss

kW

√

x) Calculated Pump Loss

kW

√

xi) Guaranteed Auxiliary Loss (Max)

kW

xii) Guaranteed maximum Magnetizing Current at rated Voltage

%

√

xiii) Efficiency at rated load, unity PF

%

√

xiv) Load for Maximum efficiency

%

√

√

√

15

Any limitations in the performance of the required test? If Yes, State limitations

√

16

Deviations from specifications (if any)

√

B. MAGNETIC SYSTEM Item

Description

 Unit

Specified (by Buyer)

Offered (by Vendor)

1

Core Type

 

√

         

i) 3 Phase 3 Limb (3 wound Limbs)

√

ii) 3 Phase 5 Limb (3 wound Limbs) iii) 1 Phase 2 Limb (2 wound Limbs) iv) 1 Phase 3 Limb (1 wound Limb) v) 1 Phase 4 Limb (2 wound Limbs) vi) 1 Phase 5 Limb (3 wound Limbs)

2

Type of Core Joint

 

   

i) Mitred

 

3

CRGO a) Thickness b) Max. Specific loss at 1.7 T, 50Hz.

ii) Step Lap mm W/kg Yes/No

√ √ √

4

Core bolts in Limb/Yoke

5

Minimum Gross Area of Core/Limb/Yoke/Unwound Limb (May be verified during manufacturing stage)

cm2

√

6

Stacking Factor

%

√

5

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POWER TRANSFORMER - STANDARDISATION MANUAL

Item

Description

 Unit

Specified (by Buyer)

Offered (by Vendor)

7

Voltage per Turn

V

√

8

Apparent Core Density for Weight Calculation

 

√

9

Minimum Net Weight of Silicon Steel Lamination CRGO (may be verified during manufacturing stage by calculation using input from item -5)

kg

√

10

 Max Flux density at Rated Voltage and Frequency (may be verified during manufacturing stage by calculation)

T

√

12

W/kg at working flux density

 w

√

13

Building Factor considered

 

√

14

Calculated No Load Loss at rated voltage and Frequency (Net Weight x W/kg x Building factor)

 kW

√

15

Maximum Sound Level

dB

√

17

Core Isolation test

kV

√

C. CONDUCTING SYSTEM Item

Description

 Unit

Offered (by Vendor) HV

IV

LV

Reg

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

 1

Type of Winding Helical/Disc/Layer/interwound

 2

Type of Conductor PICC/CTC/CTCE/CTCEN/BPICC

 

 3

Minimum Yield Strength of Conductor (0.2% elongation)

N/mm2

4

Maximum Current density at any tap

A/mm2

5

Bare Weight of copper without paper insulation and lead (Minimum)

kg

6

Per Phase Maximum resistance of winding at rated tap @ 75OC

Ohm

√

√

√

√

7

Number of Turns/Phase

 

√

√

√

√

9  

Dielectric Shielding used

 

√

√

√

√

i) Interleaved winding ii) Wound in Shield iii) Others

 

10

Magnetic Shielding Used

 

√

√

√

√

       

i) Yoke Shunt on core clamp ii) Magnetic shunt on tank iii) Electromagnetic (Copper/Aluminum) shield on tank iv) Others

 

POWER TRANSFORMER - STANDARDISATION MANUAL

D. COOLING SYSTEM Item

Description

 Unit

Specified (by Buyer)

1

Type of Cooling i) ONAN ii) ONAN/ONAF iii) ONAN/ONAF/OFAF iv) ONAN/ONAF1/ONAF2 v) ONAN/ONAF/ODAF vi) OFAF vii) ODAF viii) OFWF ix) ODWF

 

√

2

Percentage Rating Corresponding to Cooling Stages (HV/IV/LV)

 

√

3

Guaranteed Maximum Temperature rise at 1000m altitude

 

 

i) Top Oil by Thermometer

0

C

√

 

ii) Average Winding by resistance

0

C

√

 

iii) Winding Hot Spot

0

C

√

4

Type of Cooler

 

 

i) Radiator Bank

 

Offered (by vendor)

ii) Oil to Air Heat Exchanger  

iii) Oil to Water Cooler (Single Tube)

 

 

iv) Oil to Water Cooler (Double Tube)

 

 

v) Tank Mounted

 

 

vi) Header Mounted

 

 

vii) Separately Mounted

 

5

Cooling Fans

 

 

i) Type

 

 

ii) Size

mm 

 

iii) Rating (kW)

 kW

 

iv) Supply Voltage

 

v) Quantity (Running + Standby)

6

Oil Pumps

 

i) Type

 

ii) Size

 

iii) Rating (lpm and kW)

 

iv) Supply voltage

 

v) Quantity (Running + Standby)

7

Coolers (Oil to Air)

 

i) Quantity (Running + Standby)

 

ii) Type iii) Rating

√

√

V  No.   

lpm kW

√

V  No.    No.

√

 

√ √

7

8

POWER TRANSFORMER - STANDARDISATION MANUAL

8

Coolers (Oil to Water)

 

           

i) Quantity (Running + Standby)

 

ii) Type and Rating

 

iii) Oil flow rate

lpm

iv) Water flow rate

lpm

v) Nominal Cooling rate

kW

vi) Material of tube 9

√

 

Radiators: Width of elements

mm

Thickness

mm

Length

mm

Numbers

No.

√

E. DIELECTRIC SYSTEM Item

Description

Unit

1

Geometric Arrangement of winding with respect to core e.g.: Core-LV-IV-HV-Reg Coarse-Reg Fine

 

2

Regulating Winding

 

 

i) Body Tap

Specified (by Buyer)

Offered (by Vendor) √

√

ii) Separate

 

3

HV Line Exit point in winding

 

 

i) Top

√

√

ii) Center

 

√

4

Varistors used across Windings

Yes/No

√

 

If yes, give details

 

√ Offered (by Vendor)

5

Insulation Levels

 

         

i) 1.2/50 μs Impulse

kVp

ii) Chopped Impulse

kVp

iii) Switching Impulse

kVp

iv) AC (Short duration / Long duration)

kVrms

v) Max PD level at 1.5 PU

PC

HV

IV

LV

HVN

IVN

√

√

√

√

√

POWER TRANSFORMER - STANDARDISATION MANUAL

F. ACCESSORIES Item

Description

 Unit

Specified (by Buyer)

Offered (by Vendor)

1

 Tap Changers

 

 

i) Control a-Manual b-Automatic c-Remote d-Local

 

 

ii) Voltage Class and Current Rating of Tap Changers

 

√

 

iii) Make and Model

 

√

 

iv) Make and Type of AVR

 

√

 

v) Power Supply for control motor (No of Phase/Voltage/Frequency)

 

√

 

vi) Rated Voltage for control circuit (No of Phase/Voltage/Frequency)

 

√

2

 Tank

 

 

i) Tank Cover : Conventional/Bell/Bottom Plate Tank cover : Bolted /Welded

√

√ √

ii) Plate thickness : side, bottom, cover

mm

 

iii) Rail Gauge AXB

mm

 

iv) Minimum Clearance height from rail for lifting Active Part

mm

√

 

v) Wheels : Numbers/Plane/Flanged/Uni-Directional/ Bi-Directional/Locking Details

 

√

 

vi) Vacuum withstand Capability

mm of Hg

√

√

√

vii) Tank/Radiators/Conservator/Accessories  

viii) Radiator fins / conservator plate thickness

√

 mm Offered (by Vendor)

3

 

 Bushings

 

i) Termination Type a - Outdoor b - Cable Box (oil/Air/SF6) c - Plug in Type

 

ii) Type of Bushing : Porcelain/OIP/RIP

 

HV

IV

LV

√

√

√

HVN/IVN

iii) Bushing housing - Porcelain / polymer  

iv) Rated Voltage Class

kV

 

v) Rated Current

A

 

vi) Rated 1.2/50 us Impulse Withstand

kVp

 

vii) Rated One minute AC withstand, Dry

kVrms

 

viii) Minimum Creepage Distance

mm

ix) Make and Model x) Terminal Pad details xi) BCT Requirements

√

9

10

POWER TRANSFORMER - STANDARDISATION MANUAL

Item

Description

 Unit

4

 Indicative

 

 

i) Winding temperature thermometer

 

 

ii) Oil temperature thermometer

 

Offered (by Vendor)

iii) Temperature sensors by Fibre optic  

iv) Oil actuated/gas operated relay

 

 

v) Pressure Relief Device

 

 

vi) Dehydrating Breathers

 

 

vii) Conservator Bag(air cell)

 

 

viii) Oil level Indicators

 

 

Main Conservator

 

 

OLTC Conservator

 

 

ix) Oil Sight Window

 

Main Tank

√

   

Main Conservator  

OLTC Conservator

 

x) Tap Changer protective device  

xi) Bushing CTs

 

5

 Transformer Oil

 

 

i) Grade as per IEEMA spec (see Chapter 6 of this Manual) / IEC60296 Inhibited / Uninhibited

  √

ii) Spare oil as percentage of first filling iii) Manufacturer 6

7

Press Board i) Make ii) Type Conductor Insulating Paper (Kraft paper, thermally upgraded Kraft paper, Nomex)

√

√

POWER TRANSFORMER - STANDARDISATION MANUAL

ANNEXURE 1.1 Legend: NLL - No Load Loss in kW; FLL - Full Load Loss in kW; AL - Auxiliary Loss in kW STANDARDISED LOSSES FOR POWER TRANSFORMERS 145kV CLASS TRANSFORMER Sl.No

MVA

IMPEDANCE %

HIGH LOSS NLL/FLL/AL

LOW LOSS NLL/FLL/AL

1

7.5

8.35

8.5/45/-

7/35/-

2

10

10

12/80/-

8.5/70/-

3

12.5

10

14/100/-

10/80/-

4

16

10

15/110/-

11/100/-

5

20

10

17/130/-

12/110/-

6

25

10

18/140/-

14/115/-

7

31.5

12.5

20/150/-

18/125/-

8

40

12.5

25/185/-

20/140/-

9

50

12.5

30/200/-

25/160/-

10

63

12.5

32/240/5

27/190/4

11

80

12.5

40/275/6

32/230/5

245kV CLASS TRANSFORMERS Sl.No

MVA

IMPEDANCE %

HIGH LOSS NLL/FLL/AL

LOW LOSS NLL/FLL/AL

1

50

12.5

33/215/-

26/160/-

2

80

12.5

44/280/6

35/235/5

3

100

12.5

55/320/8

45/270/7

4

125

15

60/370/9

55/300/8

5

160

15

74/445/11

64/365/10

245kV CLASS TRANSFORMERS(GT) Sl.No

MVA

IMPEDANCE %

HIGH LOSS NLL/FLL/AL

LOW LOSS NLL/FLL/AL

1

140

12.5

80/400/10

65/340/10

2

250

14

130/600/13

110/500/12

3

315

14

140/750/16

130/650/15

4

600(3*200)

14

100/450/14

80/380/12

245kV CLASS TRANSFORMERS (AUTO) Sl.No

MVA

IMPEDANCE %

HIGH LOSS NLL/FLL/AL

LOW LOSS NLL/FLL/AL

1

100

12.5

30/240/6

25/210/6

2

160

12.5

38/350/8

35/300/8

3

200

15

45/430/12

40/330/12

11

12

POWER TRANSFORMER - STANDARDISATION MANUAL

400kV CLASS AUTO - TRANSFORMERS Sl.No

MVA

IMPEDANCE %

HIGH LOSS NLL/FLL/AL

LOW LOSS NLL/FLL/AL

1

100(400/132/33)

12.5

60/300/8

50/250/8

2

200(400/132/33)

12.5

80/400/10

65/325/10

3

315(400/220/33)

12.5

95/565/15

75/520/15

4

500(400/220/33)

12.5

150/700/18

120/650/16

5

3*105

12.5

50/175/7

40/165/8

6

3*166.67

12.5

60/250/12

50/210/12

7

3*200

12.5

65/300/13

60/260/13

8

3*250

12.5

78/360/15

70/310/15

9

100

12.5

45/300/8

40/270/8

10

200

12.5

76/400/10

65/350/10

11

315

12.5

95/550/13

78/440/13

12

500

12.5

140/600/16

115/600/16

13

3*105

12.5

37/195/6

33/185/6

14

3*166.7

12.5

48/270/11

42/250/11

15

3*200

12.5

60/350/12

55/320/12

16

3*250

12.5

70/420/15

60/380/15

420kV CLASS TRANSFORMERS (GT) Sl.No

MVA

IMPEDANCE %

HIGH LOSS NLL/FLL/AL

LOW LOSS NLL/FLL/AL

1

250

14.5

150/600/14

140/550/12

2

315

14.5

175/650/16

160/600/14

3

3*200

14

120/410/12

110/380/12

4

3*260

14.5

135/500/14

125/460/14

5

3*333

15

157/615/6

140/580/16

800kV CLASS TRANSFORMERS (AUTO) Sl.No

MVA

IMPEDANCE %

HIGH LOSS NLL/FLL/AL

LOW LOSS NLL/FLL/AL

1

3*333

14

74/510/15

55/400/8

2

3*500

14

83/660/16

62/510/10

800kV CLASS TRANSFORMERS(GT) Sl.No

MVA

IMPEDANCE %

HIGH LOSS NLL/FLL/AL

LOW LOSS NLL/FLL/AL

1

3*200

15

75/464/35

70/280/10

2

3*260

15

92/565/40

92/340/12

3

3*333

15

125/650/40

115/495/12

POWER TRANSFORMER - STANDARDISATION MANUAL

ANNEXURE 1.2

LIST OF TRANSFORMER RATINGS CONSIDERED IN STANDARDISATION MANUAL Type

132KV

220KV

400KV

765KV

Two Winding Transformers

132/33 kV, 40/50 MVA

220/66 kV, 100 MVA

-

-

Auto Transformers

132/66 kV, 40/50 MVA

220/132 kV, 100 MVA, 3Ø

400/220/33 kV, 315 MVA, 3Ø & 500 MVA, 3Ø

765/√3 // 400/√3 333 MVA, 1 Ø 500 MVA, 1 Ø

132/33 kV, 25/31.5 MVA

220/132 kV, 160 MVA, 3Ø

400/220/33 kV 167 MVA, 1 Ø

-

15.75/235 kV, 3Ø 315 MVA

15.75/420 kV, 315 MVA, 3Ø

21/765 kV, 260 MVA, 1Ø

21/420 kV, 200 MVA, 1Ø

21/765 kV, 333 MVA, 1Ø

Generating Transformers

21/420 kV, 260 MVA, 1Ø 21/420 kV, 333 MVA, 1Ø

13

14

POWER TRANSFORMER - STANDARDISATION MANUAL

ANNEXURE 1.3 List of applicable Standards for Transformers 1. APPLICATION GUIDES Particulars

IEC

ANSI/IEEE

60076-8 ed1.0

-

Converter Transformers

61378-3

-

Tap Changers

60214-2

-

60076-14 ed1.0-2013

IEEE 1276-1997

Transformers connected to Generators

-

C57.116-1989

Transformers for non-sinusoidal currents (loads with Harmonics)

-

C57.110-2008

Loss Evaluation Guide

-

C57.120-1991

62032 ed2.0

C57.135-2012

TR 60616-1978

C57.105-1978 (Connections) C57.12.70-2000 (Terminal markings)

-

C57.19.100-1995

60050-421

C57.12.80-2010

-

C57.12.59-2001 C57.12.109-1993

60071-1,2,3 60664-1 (Low voltage)

1313.1-1993 (Definition & principles) 1313.2-1999 (Application guide)

60038-2009

1312-1993

Transformers for Nuclear Generating station

-

638-1992

Bar coding of Distribution transformers

-

C57.12.35-2007

TS 60815-2008

-

60943-1998

-

TS 61463-2000

-

Seismic Guide for Transformers & Reactors

-

C57.114-1990 (withdrawn in 1996)

Recommended Practice for Seismic design of substations

-

693-2005

61639-1996

-

Transformers

Transformers using High Temp. Insulation Materials

Phase shifting transformer (Application, Specification, Testing Guide) Terminal Marking & Connections

Apparatus Bushings Standard Terminology Through fault current duration(Equipment damage curves) Dry Oil filled Insulation co-ordination

Preferred Voltage Ratings

Selection of insulators for polluted environments Permissible temperature rise for terminal Bushings - Seismic Qualification

Direct connection details between transformers & GIS

POWER TRANSFORMER - STANDARDISATION MANUAL

Particulars

IEC

ANSI/IEEE

60076-10-1 (2005)ed1.0

C57.136-2000 C57.12.58-1991

Cleaning of Insulators

-

957-2005

Occurrence and Mitigation of Switching transients induced by transformers

-

C 57.142/ 2010

60050-421-1990

C57.12.80-2010

Metric conversion of transformer standards

-

C57.144-2004

Transient Voltage Analysis of Dry type transformer Coil

-

C57.12.58-1991

Determination of maximum winding temperature rise in liquid filled transformers

-

IEEE Std 1538-2000

Electrical Power System Device Function Numbers, Acronyms, Contact designations

61850-7-4

C37.2-2008

Recommended electrical clearances in air insulated electrical power substations

-

IEEE Std 1427-2006

Guide for protecting Transformers Guide for protection of network Transformers Guide for Protection of Shunt Reactors Application of CTs used for Protective Relays

-

C37.91-2008

Determination of sound level Guide for sound abatement

Standard Terminology

C37.108-2002 C37.109-2006 C37.110-2007

Safety of Transformers - EMC requirements

62041 ed2.0-2010

-

IEC

ANSI/IEEE

60076-1 ed3.0-2011

C57.12.00-2006

-Dry

60076-11 ed1.0

C57.12.01-2005

-Self protected liquid filled transformer

60076-13 ed1.0

-

60076-15

-

61378-1 ed 2.0 (2011-07)

C57.18.10-1998

61378-2

C57.129- 2007

2.

Specifications

Particulars -Oil filled

-SF-6 filled -Converter transformer -HVDC transformer -Traction transformer

60310-2004

-Phase shifting transformer

62032-2005

C57.135-2005

Transformers < 230 kV, 1~10 MVA single phase, 0.8~100 MVA 3 Phase

-

C57.12.10-1997

Overhead distribution transformers < 500 kVA, 34.5/13.8 kV

-

C57.12.20-2005

15

16

POWER TRANSFORMER - STANDARDISATION MANUAL

Particulars

IEC

ANSI/IEEE

Pad mounted 3 Phase DT < 2.5MVA 34.5/0.48kV

-

C57.12.22-1993

Pad mounted single Phase DT < 167 kVA 34.5/0.48kV With separable HV Connector

-

C57.12.25-1990

Pad mounted 3 Phase DT - with insulated HV connectors < 2.5MVA 34.5/­­­­____kV with separable HV connector

-

C57.12.26-1992

Pad Mounted Compartmental type Single Phase Distribution Transformers (HV 34.5 kV / LV 240-120 V ≤167 kVA)

-

C57.12.21-1992

Pad mounted 3 Phase DT < 5 MVA 34.5/0.48kV

-

C57.12.34-2004

Enclosure Integrity-Pad mounted

-

C57.12.28-2005

Enclosure Integrity-Pad mounted for coastal environments

-

C57.12.29-2005

Enclosure Integrity-Pole mounted

-

C57.12.31-2002

Enclosure Integrity-Submersible equipment

-

C57.12.32-2002

Electronics Power Transformers

-

IEEE Std 295-1969

Liquid immersed distribution substation transformers

-

C57.12.36-2007

Secondary network transformers – subway and vault type

-

C57.12.40-2006

Secondary network protectors

-

C57.12.44-2005

Ventilated, Dry type power transformers 1~500 kVA single phase 15~500 kVA 3 phase

-

C57.12.51-1981

Sealed, dry power transformers > 0.5 MVA 3 phase 34.5 kV

-

C57.12.52-1981

Dry type transformers used in unit substations

-

C57-12.55-1987

60076-16 ed1.0(2011-06)

-

Step Voltage Regulators_standard requirements ,terminology and test code

60076-21 ed1.0 (2011-12)

-

Design, testing and application of liquid immersed transformers using high temperature insulation

60076-4 ed1.0 (2013)

PC57.154/D9.1-2012-06

Transformers for Wind Turbine applications

POWER TRANSFORMER - STANDARDISATION MANUAL

3.

Testing

Particulars Testing -General, Dry transformer -General, oil filled -HVDC transformer

IEC

ANSI

60076-1 ed2.1 C57.12.91-2001 C57.12.90-2010 C57.129-2007

Dielectric tests

60076-3 ed3.0-2013

Temperature rise test -Oil filled -Dry transformer -Determination of hot spot temperature of dry type transformer

60076-2 ed3.0 -2011

Impulse/ switching surge test Recommended practice for impulse test of distribution transformer

60076-4 ed1.0

C57.98-1993 C57.138-1998

Short circuit withstand requirements & testing

60076-5 ed3.0

C57.12.90-2006

Loss measurement

-

C57.123-2010

Temperature rise test for Overload

-

C57.119-2001

PD testing -Oil filled -Acoustic -Dry Transformer

C57.12.90-2006

C57.12.90-2006, IEEE 1538-2000 C57.134-2000

60270-2000 / 60076-3-2000 C57.113-1991 C57.127-2007 C57.124-1991

Test for thermal evaluation of dry type transformers (Cast resin & Resin encapsulated)

-

C57.12.60-1998

Test for thermal evaluation of dry type transformers (Ventilated dry type)

-

C57.12.56-1986

Test for thermal evaluation of dry type transformers (Dry type specialty and general purpose)

-

IEEE 259-2004

Guide for determination of maximum winding temperature rise in liquid filled transformers

-

IEEE 1538-2000

Test procedure for thermal evaluation of insulation systems for liquid immersed transformers

-

C57.100-2011

Measurement of frequency response

60076-18 ed1.0(2012-07)

C57.149 -2012

Determination of uncertainties in loss measurement

60076-19 ed1.0(2013)

-

17

18

POWER TRANSFORMER - STANDARDISATION MANUAL

4.

Transformer Oil

Particulars

IEC

ANSI / IEEE / ASTM

Mineral Oil Specifications

60296-2012

ASTM D3487-08

Mineral Oil- Recycled Oil

62701 ed1.0-2013

-

Silicone Oil Specifications

60836-2005

ASTM D4652-1987

62770 ed1.0- 2013

-

Organic Ester Oil Specifications

61099-1992

-

Synthetic Aromatic oil specifications

60867-1993

-

Mineral oil Maintenance

60422-2005

C57.106-2013

-

C57.147-2008

Silicon oil maintenance

60944-1988

C57.111-1989

Synthetic Organic Ester Maintenance

61203-1992

-

-

C57.121-1998

Sampling

60475-1974 60567-2005

ASTM D923-97 ASTM D3613-98

BDV

60156-1995

ASTM D1816-97 ASTM D 877-00

Oxidation stability

61125

ASTM D2440 ASTM D2112-01

Water content

60814

ASTM D1533-05

60599-1999

C57.104-2008

TS 61464-1998

-

-

C57.139-2012

DGA –During factory test

61181-2007

PC57.130/D17-2006

DGA – Sampling

60567-2005

-

DGA – Test method

-

ASTM D 3612-01

DGA – Silicone oil filled transformers

-

C57.146-2005

Reclamation of Oil

-

IEEE 637-1985 (R2007)

DGA –Ester Fluids

-

PC57.155D4

Natural Ester Oils

Natural Ester oil maintenance

Hydrocarbon fluid maintenance

DGA - Interpretation of results DGA - Bushings DGA – OLTC

POWER TRANSFORMER - STANDARDISATION MANUAL

5.

Accessories

Particulars Tap changers Bushing -General -HVDC Bushings -Dimensions -Terminals Bushing Application Guide Bushings - Seismic Qualification Reactors -Specifications -Testing -Dry type series -Smoothing reactors for HVDC

IEC

ANSI

60214-1

C57.131-2012

60137-2008 60518-1975 -

C57.19.00-2000 C57.19.03-1996 C57.19.01-2000 C57.19.100-1995 TS 61463-2000

60076-6

C57.21-2008 (Shunt) C57.16-1996

-

IEEE 1277-2000

Induction voltage regulator

C57.15-1999

Control Cabinet

C 57.148-2011

6. Raw Materials Particulars Winding Wires: Paper tape covered Rectangular Wire Magnetic Materials Part 8-7-Specifications for individual materials (Cold-rolled grainoriented electrical steel strip and sheet delivered in the fully processed state). Non-impregnated densified ,laminated wood for electrical purposes : Part 1 Definitions Part 2-Methods of Test Part 3-1 Specifications for Sheets Part 3-2 Specifications for rings Electrical Papers Part 1 Definitions Part 2 Methods Of Test Part 3-1General Purpose Paper Part 3-2Capacitor Paper Part 3-3 Crepe Paper Part 3-4 Electrolytic capacitor paper Part 3-5 Special Papers Non cellulosic Electrical Paper Part3-3 Unfilled aramide(aromatic polyamide)

IEC

ANSI

60317 ed4.0- 2013

-

61061-3-1

60404-8-7 ed3.0—2008

60554-1 60554-2 60554-3-1 60554-3-2 60554-3-3 60554-3-4 60554-3-5 60819-3-3 ed3.0-2011

-

-

-

19

20

POWER TRANSFORMER - STANDARDISATION MANUAL

Particulars Pressboard and press paper for electrical purposes Part 1 Specifications Part 2 Methods of Test Part 3 -1 Press Board Part 3-2 Press Paper

IEC

ANSI

60641-1 60641-2 60641-3-1ed2.0-2008 60641-3-2 -

Laminated Press Board Part 1Definitions Part 2 Methods of Test Part 3-1 Laminated pre compressed Press Board

60763-1 ed2.0-2010 61628-2 ed1.1-2007 60763-3-1 ed2.0-2010

7. Installation, Operation & Maintenance

Particulars

IEC

Guide for Transportation of Transformers &Reactors Installation & maintenance -Oil filled Transformer -Dry type Transformer

ANSI/ IEEE

57.150-2012

-

C57.93-2007 C57.94-1982

60076-7 ed1.0(2005-12) 60076-12 ed1.0(2008-11)

C57.91-2011 C57.96-1999

Failure investigation

-

C57.125-1991

Reporting failure data

-

C57.117-1986

Evaluation and Reconditioning of oil filled transformers

-

C57.140-2006

Diagnostic field testing

-

C57.152-2013

Monitoring of transformers & accessories

-

C57.143-2012

Substation-Fire protection Containment &control of oil spills in substations

-

979-1994(R2004) 980-1994(R2001)

Guide for the design, construction and operation of Electric Power substations for community acceptance and environmental compatibility

-

1127-1998

Loading guide - Oil filled Transformer - Dry type transformer

POWER TRANSFORMER - STANDARDISATION MANUAL

8. Operation & Maintenance:

Item

CIGRE Brochures

IEEE Standard

IEC Standard

Operational Problems

170-2000 Static Electrification 228-2002 Ageing Process 323-2007 Ageing of Cellulose 349-2008 Moisture Equilibrium and migration in insulation system 378-2009 Copper sulfide in insulation 393-2009 Thermal performance of Transformers 445-2012 Maintenance

C57.91-2011 Loading Guide for Oil Immersed Transformers C57.96-1999 Loading Guide for Dry Type Transformers

60076-7:2005 Loading Guide for Oil Immersed Transformers 60905-1987 Loading Guide for Dry type Transformers

Life Assessment

227-2003 Life Management Techniques 248-2004 Economics of Management 298-2006 Life time Data Management 413-2010 Oil regeneration and Dehalogenation

C57.93-2007 Installation & Maintenance of Transformers C57.106-2002 Maintenance of Oil C57.140-2006 Evaluation & Reconditioning 637-1985(R2007) Reclamation of Oil

60422-2005 Maintenance of Oil

Diagnostics

254-2002 Dielectric Response 296-2006 Recent developments in the interpretation of DGA 342-2008 SFRA 343-2008 Recommendations for Condition Monitoring and condition assessment facilities for transformer 414-2010 Dielectric response methods for transformer windings 420-2010 Life Time Condition Assessment 436-2010 Experiences in service with new Insulating Liquids 443-2010 DGA on non-mineral oil and OLTC oil. 444-2010 Guide lines on unconventional PD measurements 494-2012 Furanic Compounds for Diagnosis

62-1995 (R2005) Diagnostic Field Testing of Transformers & Reactors C57.104-2008 DGA of Oil C57.117-1986 Guide for reporting failure data of transformers C57.125-1991 Guide for Site failure investigation of Transformers C57.146-2005 DGA of Silicon Oil filled Transformers C57.200-2000 PD detection by Accoustics PC 57.139 D12-2009 DGA of OLTC Oil PC 57.143 D21-2010 Transformer Monitoring

60076-18-2012 SFRA 60567-2011 Sampling of gases for DGA 60599-1999 DGA interpretation

21

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POWER TRANSFORMER - STANDARDISATION MANUAL

9.

CIGRE Brochures for Asset Management of T&D equipment:

Standing Committee/ Product

A2 Transformer

A3 HV Equipments

B1 Cables

B2 Lines

B3 Substations

C1 Asset Management

D1 Material

Other SC’s

Condition Assessment & Monitoring

393 436

083 259 WG A3.06

-

-

300 380 381 400

-

226

SC A1: 437, 386

End of Life Issues

227

165 368

358

353

252

422

296 409 414

-

Risk Management and AM Decision Making

248

-

-

-

300 472

309 327 422

420

SC C3 : 340,383

Grid Development

-

335 336

-

385

-

176

-

-

Maintenance Processes & Decision Making

445

259 319

279

230

380

-

-

-

Collection of Asset Data and Information

298

-

-

-

-

-

-

SC B5: 329 SC D2: 341

POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 2 Design and Engineering features

(1) Architectural Features, General Arrangement Drawings & Accessories

Working Group Members Mr. M. Vijayakumaran – ALSTOM Ltd Mr. P. Ramachandran – ABB Ltd Mr. Y. V. Joshi

– GETCO

Mr. M.M. Goswami – POWERGRID Mr. T. Vijayan

– T&R Ltd

23

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POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

CHAPTER - 2 DESIGN AND ENGINEERING FEATURES

Part 1 - Architectural Features, General Arrangement Drawings & Accessories INTRODUCTION In a process of standardisation of transformer from procurement to commissioning, architectural features do have major role. At present, same rating/class transformers are being designed differently even for same user. Even for same specifications, manufacturer reviews design for successive tender considering prevailing market condition and thereby make changes in transformer architectural features and general arrangements. This reviewing activity not even leads to increase in design & manufacturing cycle time, cost, human efforts and inventories but also keep user away from preparing for footprint in his switch-yard. To resolve all these issues and to define standard architectural features and accessories, this Working Group had 5 rounds of meetings and discussions in the subject matter. However, standardisation refers to limit the variation in terms of layout, general arrangements, interchangeability, accessories selection guide including data sheet, drawings, schematic, mounting arrangement/interface with tank, critical check points for installation and commissioning, etc. Interchangeability has been referred here mainly to transformers of similar rating, voltage and other technical characteristics, even when they are being purchased from different suppliers under different contracts so as to arrive at common dimensions and layout, to allow physical interchangeability with minimum of adaptation and optimize spare holding inventory. It is possible for transformers purchased earlier to be replaced later by more modern designs, even with larger ratings but designed to accommodate in the same space. Utilities purchase transformers to meet requirements of this kind in order to increase availability and reduce costs by minimising the outage time in the event of a transformer having to be removed from service and replaced by spare/new transformer available. The concept may apply for separately cooler bank mounted transformer in which case the requirement of interchangeability can be even made applicable to the main transformer excluding cooler bank. This policy will reduce the complexity of the purchaser’s stock of transformers, bushings, fittings, tap changer components, etc and will minimize maintenance practice and costs. ŸŸ

Aesthetic (Appearance) of Transformer: Mounting of fittings to be same as far as possible, mounting & location of Cooler bank, Conservator etc. shall be at standard position. A typical plan & section drawing showing accessories like Bushings, Tap changer, conservator, OLTC Drive Mechanism, Neutral Earthing arrangement, Marshalling box, etc. are enclosed in this Manual. Tank mounted radiators are recommended, for ratings up to 100 MVA and they can be separate for higher than 100 MVA.

ŸŸ

Tank Type: Bell type, Bolted /Welded construction, Conventional & Form Fit type

ŸŸ

Cooler: The Fin thickness of radiator will be minimum 1.0 mm. Only 4 heights are proposed (2.0 M, 2.5 M, 3.0 M & 4.5 M) with number of elements to be 20, 24 & 26. Radiator (external) shall be hot dip galvanized or painted as per Data Sheet of Radiator given in this Manual. For internal surface galvanizing is not recommended. Corrosion resistant paints may be applied on galvanized surface for better appearance.

ŸŸ

Rail, Roller & Roller Assembly: It is proposed to remove provision of rail as nowadays transformers are not transported by railway but rails are required for transformers to achieve center line of transformer, provision may be provided for rail. However, Transformers are recommended to put directly on plinth without rollers & roller assembly will be standardised. Only one set of roller is recommended for each substation. Since Roller is casted, hence only Roller assembly is needed to be galvanized.

ŸŸ

Valve Schedule: Valve specification, type & application shall be standardised. This will be reviewed with experts and finalized.

ŸŸ

Conservator: Main conservator should be with Aircell. OLTC conservator shall be separate to avoid intermixing of oil. Maintenance free type dehydrating silica gel breather may be provided in remote operation substation.

25

26

POWER TRANSFORMER - STANDARDISATION MANUAL

ŸŸ

Internal Earthing of Metal Parts: Earthing point shall be robust and made accessible for the inspection to the extent possible.

ŸŸ

Painting: Tank, Radiator & Fittings may be of different shades. Epoxy coating to be avoided for outermost layer. It should be PU only. Casting parts not necessarily painted for matching shade. Any fabricated accessory should be either galvanized or outer side PU. Powder coating may be accepted provided it should be sun light / outdoor / UV ray resistant. Being not Eco-friendly, Zinc Chromate is not to be used. Bottom plate of tank may be accepted with water based paint. Internal paint shall be oil resistive with thickness of 25 to 40 micron only.

ŸŸ

Hardware / Bolts: Material will be MS with grade 8. To avoid bending High Tensile Steel (HTS) is also recommended. Stainless Steel should not be used in the main tank joint.

ŸŸ

Gasket: Since one side of gasket is exposed to the transformer oil of different quality (old, new, inhibited, un-inhibited, Paraffin base oil, Naphthenic base oil & vegetable oil etc.) & other side is water, moisture, humidity, air, oxygen, pollution, saline etc., hence gasket to be reliable & suitable for these applications. Chord (Nitrile Chord) for all flange joints are recommended. Top cover of tap changer to be suitable for O-Ring or chord with interchangeable with older one.

ŸŸ

Marshalling Box / Common Marshalling Box: The enclosure (shell) shall be made of cold rolled sheet and galvanized / painted. Stainless steel and Aluminum may also be considered for Marshalling Box.

ŸŸ

OTI & WTI: Switches shall be Mercury-free.

ŸŸ

Breather: Cobalt is a banned material, hence not recommended to use. Size of silica gel is to be standardised, either it can be one of 100% or two of 100% in parallel. Valve over breather is not recommended.

ŸŸ

Pressure Release Device (PRD): PRD shall be mounted on top cover. One PRD is recommended per every 40 KL oil quantity. The oil discharge chamber and terminal box of the PRD shall be water tight with Protection class IP 56 or better as per IEC 60529.

ŸŸ

Ladder: Ladder (Fixed type) with safety locking device to be provided. Provision for fixing safety barriers shall be provided on top tank cover. Ladder for conservator may be provided considering safety for working at height.

ŸŸ

Fire Protection System (FPS): Provision of FPS is recommended in line with CEA regulation, i.e. for 10 MVA & above. It is recommended to keep provision in each transformer.

ŸŸ

Health, Safety and Environment (HSE): All the HSE aspects shall be covered while preparing standard GA drawing. Adequate working space on top of transformer with suitable railing for safety shall be provided.

ŸŸ

Ratings of Transformer: Standard ratings considered are as per Annexure 1.2.

ŸŸ

Rail gauge shall be standard (1676 mm). Plinth mounted tank design may be adapted, as a specific requirement. Rating wise rail gauge are standardised as below: 1.

765 kV & 400 kV, 1-Phase Generator Transformer (having two rails or three rails)

2.

765 kV & 400 kV, 1-Phase Auto Transformer (having four rails) Note: 3-Phase ratings for above also to be considered depending on size and transportability. 3. 400 kV, 3-Phase Auto Transformer (having four rails) 4. 400 kV & 220 kV, 3-Phase Generator Transformer (having two rails) 5. 220 kV & 132 kV, Power Transformer (having two rails)



ŸŸ

Location of OLTC: The number and location will be as per OLTC type & its specification.

ŸŸ

Interchangeability & Common Architecture: The OGA is prepared in the form of block diagram & all important fittings positions are shown (Annexure 2.1). Marshaling Box, Cooler control cabinet and any other cabinet required for any monitoring devices will be tank mounted. Grounding inter phase is considered to minimize.

ŸŸ

Jacking: 4 nos. of jacks shall be provided.

ŸŸ

Cooler bank foundation: Modular block foundation is to house any make radiator in the standard foundation.

ŸŸ

Maximum Height of Conservator to be standardised to make the firewall uniform.

ŸŸ

The tertiary and neutral bushing shall be provided on top of the tank cover. The provision on side wall of the tank is not recommended in view to avoid lowering of oil level in case of bushing replacement which is time consuming.

ŸŸ

Due to winding capacitances, the tertiary winding faces transferred surge voltages during impulse application on HV/IV winding. Therefore, the bushings of 52 kV rating are provided for 33 kV tertiary winding.

POWER TRANSFORMER - STANDARDISATION MANUAL

Cooler Bank Design:



ŸŸ

Provision for connecting cooling bank on both sides shall be provided. Pipe work on main tank to be designed in such a way that position of the cooler bank, conservator etc. can be changed at site by simple reconnection.

ŸŸ

Specification for separately mounted radiator bank distance (for oil pipe connection) from main tank to be kept standard or minimum. Position of cooling fan to be bottom of radiator bank but cooler fan support from ground is not recommended.

ŸŸ

Modular block foundation will be explored to house any make of radiator in the standard foundation.

ŸŸ

Tank mounted Unit cooler option for Generating / Large transformers can be considered.

ŸŸ

If more than one unit is provided, the breather for main tank shall be in parallel.

ŸŸ

No. of OLTC and its location will be as per OLTC type & its specification.

ŸŸ

Jacking: 4 - jacks shall be provided and their locations to be decided by the manufacturer such that it will not foul rail, rollers or other accessories.

ŸŸ

Height of Conservator & HV bushing shall be same.

ŸŸ

Hot dip galvanized with a minimum thickness of 70 µm and painting as per the following specification. Surface preparation

Primer coat

Intermediate undercoat

Finish coat

Total dry film thickness (DFT)

Colour shade

Main tank, pipes, conservator tank, oil storage tank etc. (external surfaces)

Shot Blast cleaning Sa 2½*

Epoxy base Zinc primer (30-40 μm)

Epoxy high build Micaceous iron oxide (HB MIO) (75 μm)

Aliphatic polyurethane (PU) (Minimum 50 μm)

Minimum 155 μm

RAL 7035

Main tank, pipes (above 80 NB), conservator tank, oil storage tank etc. (internal surfaces)

Shot Blast cleaning Sa 2½*

Hot oil resistant, non-corrosive varnish or paint or epoxy

-

-

Minimum 30 μm Max 40 µm

Glossy white for paint

Radiator (external surfaces)

Chemical/ Shot Blast cleaning Sa 2½*

Epoxy base Zinc primer (30-40 μm)

Epoxy base Zinc primer (30-40 μm)

PU paint (minimum 50 μm)

Minimum 100 μm

Matching shade of tank/differrent shade aesthetically matching to tank

Radiator and pipes up to 80NB (internal surfaces)

Chemical cleaning, if required

Hot oil proof, low viscosity varnish

-

-

-

-

Control cabinet/ marshalling box

Seven tank process as per IS:3618 & IS:6005

Zinc chromate primer (two coats)

-

EPOXY paint with PU top coat

Minimum 80 μm

RAL 7035 shade for exterior and interior

ITEM

Note : * indicates Sa 2½ as per Swedish Standard SIS 055900 of ISO 8501 Part-1.

ŸŸ

The quality of paint should be such that its colour should not fade during vapor phase drying process and shall be able to withstand temperature up to 120 0C.

ŸŸ

Transformer shall be put on plinth but provision of roller shall be provided. The nos. of jacking points / pads and lifting bollards / hooks / devices shall be 4 only. Location shall be such that it should not interfere with loading and unloading from trailer.

27

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POWER TRANSFORMER - STANDARDISATION MANUAL

ŸŸ

Internal arrangement drawing of the active part and lead exit to be provided in the Instruction Manual by manufacturer for better assessment of probable fault location when reflected in abnormal DGA results.

ŸŸ

Line diagram for core, core clamp and tank earthing diagram shall be provided in the Instruction Manual.

ŸŸ

Location of OLTC Driving mechanism box, Marshalling box, and optical fiber termination shall be on the same side.

ŸŸ

The main and OLTC conservator shall be integrated type with separate compartments so that they are at same height with no pressure difference. In the case of separate cooler bank or if there is difficulty, OLTC conservator can be separate.

POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 2 Design and Engineering features

(2) Power Transformer Fittings and Accessories - OLTC

Working Group Members Mr. V. K. Lakhiani

- T&R Ltd.

Mr. R. V. Talegaonkar

- CTR Mfg. Ind. Ltd.

Mr. S. Rajan

- CTR Mfg. Ind. Ltd.

Mr. R. Prakash

- Easun, MR

Mr. Vijayakumaran

- ALSTOM Ltd.

Mr. R. K. Shukla

- On Load Gears

Mr. M. M. Goswami

- POWERGRID

29

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POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

Part 2 - Standard On-Load-Tap Changers for Power Transformers INTRODUCTION On Load Tap changers (OLTC) are the most important equipment used in the power transformers for changing the tap of a winding (to vary effective transformation ratio of the transformer) whilst, the transformer is energized or is on load. Performance requirements of these OLTCs for use in transformers and their routine and type tests are described in IEC 60214-1. Selection criteria of the OLTC, their various types, fittings and accessories etc. are covered in the IEC 60214-2 “Application Guide”. CBIP Manual on transformers (Publication 317) in ‘Section GG’ gives guidelines for voltage control of Power Transformers employing OLTC. As a general practice, end user of the transformer gives the requirement of voltage regulation (on HV or LV side), range of percent voltage variation (from maximum voltage to minimum voltage, expressed as % of rated voltage), number of steps, % impedance of transformer at maximum voltage and minimum voltage tap positions in case of parallel operation with existing transformer and other control schematic requirements. Transformer manufacturer, meeting the above requirement, decides the location of tapping winding (physical as well as electrical), based on his design philosophy and experience and estimates the current and voltages seen by the tapping winding (across range, between steps, to earth and between phases). Based on this data, OLTC supplier provides a suitable tap changer from his available range. This IEEMA standard on OLTC purports to define the specification requirements and selection criteria of OLTC and recommends the standard parameters of OLTC to be used in transformers of prevalent standard ratings in the country standardised by CBIP. SCOPE This standard covers specification requirements and selection of On Load tap changers for Power Transformers in the country. 1.0. General requirements for selection of OLTC parameters: 1.1. Standards Applicable

The tap changer shall conform to latest edition of IEC 60214 Part1: Performance Requirements & Test Methods; and IEC 60214 Part 2: Application Guide.

1.2. Tap Changer Specification

For comprehensive specification of OLTCs, certain data need be specified by the transformer manufacturers depending upon the transformer design & construction, apart from the specifications provided by the end users. These specification requirements are therefore divided in to two parts. 1.2.1. Specification requirements from end users (Utilities) 1.2.1.1 Transformer Details §§

Number of Phases: Single phase or three phase

§§

Rated Power: MVA

§§

Rated Voltage: HV kV / LV kV

§§

Winding Connection: HV / LV (e.g. Star, Delta, Star Auto)

§§

% Tapping range of rated winding voltage: (+)……% to (-) ……% for HV (or LV) variation.

§§

Number of tapping positions (No. of steps and % step voltage)

§§

Direction of Power flow: Unidirectional/Bidirectional

§§

Over Loading requirements (if different from IEC 60076-7).

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POWER TRANSFORMER - STANDARDISATION MANUAL

1.2.1.2 Drive Mechanism and control scheme §§

Local electrical independent control

§§

Local automatic independent control

§§

Remote electrical independent control

§§

Remote automatic independent control

§§

Parallel electrical control of two or more transformers

§§

Parallel automatic control of two or more transformers

§§

Supervisory control

1.2.1.3 Auxiliary Supply voltage §§

For Motor

§§

For control circuitry

1.2.1.4 Site Operating Conditions §§

Maximum & Minimum ambient temperatures

1.2.2. Specification requirements from Transformer Manufacturer 1.2.2.1 Type of construction of On Load Tap Changer §§

External - out of tank

§§

Internal - in tank

1.2.2.2 Tap winding arrangement §§

Linear, Reversing or Coarse / Fine

1.2.2.3 Position of taps in the winding §§

Line end, Middle, Neutral point

1.2.2.4 Highest tap current of the winding §§

…………..Amps

1.2.2.5 Highest step voltage §§

………….Volts

1.2.2.6 Insulation levels of On Load Tap Changers §§

Tap-Changer to earth (Highest voltage between any tap and earth)

§§

Between phases (Where applicable)

§§

Across Tap Range and between change-over selector contacts (Highest voltage between the extreme taps)

§§

Between adjacent contacts of tap selector and selector switch (Highest step voltage)

§§

Between diverter switch contacts (Highest step voltage)

1.2.2.7 Short Circuit Current §§

Maximum value …..kA; and duration 2 Sec

1.2.2.8 Change-over selector Recovery voltage §§

The power frequency voltage appearing between opening and closing contacts of changeover selector shall be specified. (Note: OLTC supplier shall also verify / calculate recovery voltage based on winding capacitance furnished by transformer manufacturer).

POWER TRANSFORMER - STANDARDISATION MANUAL

1.2.2.9 Mounting Arrangements for In-tank OLTCS §§

Standard flange or Bell type for OLTC

§§

Motor drive and shaft arrangements

1.2.2.10 Protective Devices §§

Oil Surge Relay

§§

Rupture disc / Diaphragm with or without trip contact

§§

Pressure relief device (optional)

§§

Over pressure Relay (optional)

1.2.2.11 Paint Type and shade 1.3. On Load Tap Changer Ratings and Selection Criteria 1.3.1 Type of construction of On Load Tap Changers 1.3.1.1 Externally mounted - out of tank, oil environment On Load Tap changers §§

These OLTCs are available up to 66 kV, 300 Amps, star / delta connected winding, and for 132 kV neutral end applications. Depending on overall economy of the transformer design, this type of OLTC is used.

1.3.1.2 Internally mounted - in tank Oil environment Tap Changers §§

These OLTCs are available for all the transformer ratings up to 220 kV line end application, up to 700 Amps neutral end and upto 2100 Amps line end applications. These tap-changers are suitable for high voltage application up to 765 kV Class of transformers.

1.3.2 Operating Principle

The OLTCs covered in this standard are of high speed transition resistor type. On-load tap-changer shall be according to selector switch principle or shall consist of a tap selector and a diverter switch with spring operated mechanism. The diverter /selector switch which arcs during tap change operation shall be so designed to ensure that its operation once commenced shall be completed independently of the control relays or switches, failure of auxiliary supplies etc. The current diverting contacts shall be housed in a separate oil chamber not communicating with the oil in main tank of the transformer.

1.3.3 Rated Through-Current of OLTCs

Rated through current of the OLTC should be more than or equal to the highest value of tap current at the assigned rated power of the transformer. This ensures meeting the overload requirements of transformers as per IEC 60076-7.

1.3.4 Rated Step Voltage of OLTCs

The rated step voltage of the tap-changer is more than or equal to the highest step voltage of the tapped winding.

1.3.5 Breaking Capacity of OLTCs

The breaking capacity requirements are met if the highest tap current and the highest step voltage of the transformer are within the declared values of rated through-current and relevant rated step voltage.

1.3.6 Insulation level of OLTCs

The rated insulation level of the OLTC is checked for Power frequency and Lightning Impulse voltages and switching impulse voltages (if specified) appearing during tests on the transformer. These insulation levels are checked at following points:

33

34

POWER TRANSFORMER - STANDARDISATION MANUAL

§§ §§ §§ §§ §§ §§

Tap-Changer to earth Between phases Across Range (Between first and last contact of tap selector or selector switch) Between change-over selector contacts. Between two adjacent contacts Between Open contacts of diverter contact

1.3.7 Number of tap positions

The Tap-changers are available up to 21 positions (20 steps) in linear and up to 35 positions (34 steps) in coarse-fine/ reversing arrangement of the tapping winding.

1.3.8 Winding connection and position of taps in the winding §§

OLTC in star connected winding:



For transformers having star connected tapping winding, the tappings are provided at the neutral end of the high voltage winding.

§§

OLTC in delta connected windings:



In delta connected windings, 3 pole middle of the winding arrangements is used up to 110 kV Class of transformers. 33 kV windings are mostly used in delta configuration by all utilities. 66 kV windings are also used in delta by some utilities like Gujarat and Karnataka. In some states like Tamil Nadu and Karnataka 110 kV delta systems are also in vogue. Tap-changers are available up to 66 kV class delta arrangement as external out-of-tank construction and up to 110 kV class in in-tank construction.

§§

Position of OLTC in auto transformer

§§

Scheme, as shown in (a) in above figure, is used for autotransformer with a ratio 2:1 and for moderate regulating range of say 15%. The advantage of this scheme is that the tap winding is at the neutral end and be designed for graded insulation and a three phase neutral end tap changer can be used. This arrangement is ideally suitable for 765 / 400 kV auto transformers. In this case, VFVV (variable flux and variable voltage) type regulation is foreseen with change in tertiary voltage which is accepted since tertiary is a stabilizing winding in most cases.

POWER TRANSFORMER - STANDARDISATION MANUAL

§§

For auto transformers on systems where the medium voltage is regulated, schemes as shown in (b) & (d) are used. For tapping range of approximately 20% and with linear tapings scheme (b) is generally used. Higher regulating range may be achieved with scheme (d).

§§

For auto transformers where regulation is required in HV voltage, scheme (c) is used. It has the advantage that the through current of the OLTC is lower and allows the use of an OLTC with a lower current rating. It may be noted that in case of arrangement (d) tapings carry IV line current and in case of (b) tapings carry series or common current and in case of (c) tapings carry series current.

1.3.9 Change-over Selector recovery voltage

During change-over operation of reversing switch or coarse tap selector, the tap winding is disconnected temporarily from the main winding. The tap winding receives a potential determined by the winding capacitances. The difference in voltage will therefore, appear during contact operation of the changeover selector as a recovery voltage. The tap-changer manufacturer declares the safe limit for the allowed recovery voltage across change-over contacts. It is ensured that the recovery voltage appearing during change-over operation is within the declared allowed recovery voltage by the tap-changer supplier. In case the recovery voltage exceeds the allowed voltage, the same is specified by the transformer designer. The tap-changer manufacturer then provides additional devices like tie-in resistors or two way change-over selectors to limit the recovery voltage to a safe level.

1.4 Motor Drive Mechanism

The motor drive unit has following features as specified in IEC 60214. 1.4.1 Operation

OLTC gear shall be motor operated for local as well as remote electrical operation. An external handle shall be provided for local manual operation. Interlock shall be provided to prevent electric drive when the manual operating gear is in use.

1.4.2 Housing

Drive mechanism cubicle is mounted as integral part on tap-changer tank in case of external out-of-tank construction or suitable for mounting on transformer tank in case of an In-Tank construction. The motor drive cubicle is in accessible position. It is adequately ventilated and provided with anti-condensation heaters. All contactors, relay coils and other parts are protected against corrosion, deterioration due to condensation, fungi etc. The motor drive cubicle shall meet protection requirement of IP 55 as per IEC 60529.

1.4.3 Step-by-Step Control

This control feature ensures operation of OLTC by one voltage step only even in the case of continuous or repeat signals.

1.4.4 Tap Position Indication

The position of OLTC is indicated locally on motor drive unit preferably by a mechanical device, however, if any electrical or electronic device is used, it is ensured that the tap position is indicated correctly even in the event of a power failure. The tap position is visible clearly even when the motor drive door is closed.

1.4.5 Limiting Devices

There are both electrical and mechanical limiting devices to prevent operations beyond end positions.

1.4.6 Operation Counter

A minimum five-digit non-resettable counter is provided to record the number of operations completed by the tap-changer. In case of electrical / electronic counter it shall be ensured that the counter, is capable of recording local manual operations also.

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POWER TRANSFORMER - STANDARDISATION MANUAL

1.5 Test Requirements 1.5.1 Type tests

The OLTCs and motor drive units are fully type tested in accordance with cl. 5.2 and 6.2 of IEC 60214-1. These tests are as below: 1.5.1.1 Temperature rise of contacts

This test is conducted at 1.2 times the maximum rated through current of OLTC.

1.5.1.2 Switching tests

This includes 50000 test operations at maximum rated through current as service duty and 40 operations at double the maximum rated through current as breaking capacity tests.

1.5.1.3 Short circuit current test

This test is conducted at 20 times the maximum rated through current up to 100 amps and 10 times the maximum rated through current of 400 amps and more. The test current should be interpolated between these two ratings using the slope as per IEC 60214-1. The test duration should be 2 seconds.

1.5.1.4 Transition Resistor test

This test is conducted at 1.5 times the maximum rated through current of OLTC for continuous operation of half cycle (equal to number of tap positions). This ensures suitability of transition resistor design for continuous operations of OLTC under over loading condition of transformers.

1.5.1.5 Mechanical Endurance Test

The tap-changer shall be tested for 5,00,000 operations using complete tap range as per cl.5.2.5.1 of IEC 60214-1.

1.5.1.6 Pressure Test

The diverter switch/ selector switch compartment shall be tested for hot oil pressure test by filling oil inside the cylinder and heating up to 80° C. The cylinder shall be pressurized for a minimum pressure of 10 psi (0.7 kg/cm²) for 1 hour. All joints of the compartment are thoroughly checked for leakages.

1.5.1.7 Dielectric Tests

The tap-changer should be tested across all points as per cl. 1.3.6 of this chapter and insulation levels shall be declared. The tests shall be conducted in line with cl. 5.2.6 of IEC 60214-1.

1.5.2 Routine Tests

OLTC manufacturers shall conduct all the routine tests as specified in cl. 5.3 and 6.3 of IEC 60214-1 on every unit, before dispatch to assure the quality of the product

2.0 Standard ratings of OLTCs §§

Standard parameters of OLTC based on standard transformer ratings as per CBIP are recommended as given in the attached Annexure 2.2.

§§

In case the transformer ratings are not conforming to CBIP standard, customers shall specify OLTC requirements as per cl.1.2 of this standard.

3.0 Installation of in-tank tap changers §§

Precautions to be taken while installing In-tank tap changer at site are given in Annexure2.4

220kV, 100 MVA AUTO TRANSFORMER ( COOLING MOUNTED SEPARATELY )

ANNEXURE 2.1

POWER TRANSFORMER - STANDARDISATION MANUAL

37

1N

2n

1U

2u

1V

2v

2w

1W

220kV, 100 MVA AUTO TRANSFORMER ( COOLING MOUNTED ON TANK )

38 POWER TRANSFORMER - STANDARDISATION MANUAL

ROLLER CENTER = 1743

400kV, 315 MVA TRANSFORMER ( COOLING MOUNTED SEPARATELY )

RAIL GAUGE=1676 ROLLER CENTER=1743

1079

1079

RAIL GAUGE=1676 ROLLER CENTER=1743

POWER TRANSFORMER - STANDARDISATION MANUAL

39

40

POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

41

42

POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

43

44

POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

45

46

POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

47

48

POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

49

132/11

132/66

132/66

11/138

13.8/138

50

63

140

140

(-) 10 to (+) 5 of HV

(-) 10 to (+) 5 of HV

(-) 5 to (+) 15 of HV

(-) 5 to (+) 15 of HV

(+) 5 to (-) 15 of HV

17

17

17

17

17

650.8

650.8

290

230.2

162.1

128.6

800

800

300

300

200

200

996

996

953

953

953

953

31.5

(+) 5 to (-) 15 of HV

17

132/11

25

100

953

82.33

17

132/33

16

(+) 5 to (-) 15 of HV

Step Voltage (Transformer requirement)

Number Highest tap Max. of tapping current of rated positions winding through current of OLTC

Trans- Voltage Ratio (kV) Tapping former range MVA

1200

1200

1200

1200

1200

1200

1200

Rated Step Voltage of OLTC

Star

Star

Star

Star

Star

Star

Star

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

Linear/ Coarse-Fine/ Reversing

Linear/ Coarse-Fine/ Reversing

Linear/ Coarse-Fine/ Reversing

Linear/ Coarse-Fine/ Reversing

Linear/ Coarse-Fine/ Reversing

140/325

140/325

140/325

140/325

140/325

140/325

140/325

45/265

45/265

45/200

45/200

45/200

45/200

45/200

Across tapping range

15/90

15/90

15/90

15/90

15/90

15/90

15/90

Between adjacent Taps

Tap changer voltage to earth

Star / Delta

Linear / Reversing / Coarse-Fine

Rated Insulation Levels of OLTC Impulse kVrms / kVp

Winding Tapping Connection arrangement

Annexure 2.2: Standard Parameters of OLTC for Standard Transformer Ratings

Neutral End of HV Winding

Location of Tapping Winding

8kA for 2 sec.

8kA for 2 sec.

4KA for 2 sec.

4KA for 2 sec.

Neutral End of HV Winding

Neutral End of HV Winding

Neutral End of HV Winding

Neutral End of HV Winding

3.5KA for 2 Neutral sec. End of HV Winding

3.5KA for 2 Neutral sec. End of HV Winding

2 KA for 2 sec.

Max. Value of duration of short circuit current

50 POWER TRANSFORMER - STANDARDISATION MANUAL

15.75/138

220/66

220/66

220/33

220/33

220/132

220/132

220/132

11/235

13.8/235

250

50

100

50

100

100

160

200

140

140

17

(-) 10 to (+) 5 of HV

(-) 10 to (+) 5 of HV

13

13

(-5) to (+) 17 15 of LV

(-5) to (+) 17 15 of LV

382.2

382.2

921

736.65

460.5

291.6

145.8

291.6

17

17

145.8

1162.14

17

17

(-5) to (+) 17 15 of LV

(-) 10 to (+) 10 of HV

(-) 10 to (+) 10 of HV

(-) 10 to (+) 10 of HV

(-) 10 to (+) 10 of HV

(-) 10 to (+) 5 of HV

500

500

1000

800

500

350

200

350

200

1200

1696

1696

953

953

953

1588

1588

1588

1588

996

1800

1800

1200

1200

1200

1600

1600

1600

1600

1200

Star

Star

Star

Star

Star

Star

Star

Star

Star

Star

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

Linear/ Reversing

Linear/ Reversing

Linear/ Reversing

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

230/550

230/550

325/750

325/750

325/750

230/550

230/550

230/550

230/550

140/325

80/350

80/350

80/350

80/350

80/350

80/350

80/350

80/350

80/350

45/265

15/90

15/90

15/90

15/90

15/90

15/90

15/90

15/90

15/90

15/90

Neutral End Of HV Winding

Neutral End Of HV Winding

8kA for 2 sec.

8kA for 2 sec.

16KA for 2 sec

15KA for 2 sec

8kA for 2 sec.

5kA for 2 sec.

Neutral End Of HV Winding

Neutral End Of HV Winding

Line End of IV Winding

Line End of IV Winding

Line End of IV Winding

Neutral End Of HV Winding

3.5kA for 2 Neutral sec. End Of HV Winding

5kA for 2 sec.

3.5kA for 2 Neutral sec. End Of HV Winding

16KA for 2 sec

POWER TRANSFORMER - STANDARDISATION MANUAL

51

24/420/√3 (1ph)

15.75/420

15.75/420

“21/420 (1 ph)”

400/132/33

400/132/33

260

250

315

200

100

200

(-) 10 to (+) 10 of HV

(-) 10 to (+) 10 of HV

(-) 5 to (+) 10 of HV

(-) 5 to (+) 10 of HV

(-) 5 to (+) 10 of HV

(-) 10 to (+) 5 of HV

(-) 10 to (+) 5 of HV

17

17

13

13

13

13

13

15.75/235

320.75

160.4

868.2

456

361.75

1191.35

860

400

200

1000

600

500

1500

1000

800

315

682.5

13

15.75/235

250

(-) 10 to (+) 5 of HV

Number Highest tap Max. of tapping current of rated positions winding through current of OLTC

Trans- Voltage Ratio (kV) Tapping former range MVA

2886

2886

3031

3031

3031

3031

1696

1696

Step Voltage (Transformer requirement)

3000

3000

3100

3100

3100

3100

1800

1800

Rated Step Voltage of OLTC

Star

Star

Star

Star

Star

star

Star

Star

Reversing

Reversing

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

Reversing/ Coarse-Fine

325/750

325/750

325/750

325/750

325/750

325/750

230/550

230/550

80/350

80/350

80/350

80/350

80/350

80/350

80/350

80/350

Across tapping range

15/90

15/90

15/90

15/90

15/90

15/90

15/90

15/90

Between adjacent Taps

Tap changer voltage to earth

Star / Delta

Linear / Reversing / Coarse-Fine

Rated Insulation Levels of OLTC Impulse kVrms / kVp

Winding Tapping Connection arrangement

Neutral End of HV Winding

Neutral End of HV Winding

Neutral End of HV Winding

Neutral End of HV Winding

Neutral End of HV Winding

Neutral End of HV Winding

Location of Tapping Winding

6KA for 2 sec.

220 kV End of Series Winding

3.5KA for 2 220 kV sec. End of Series Winding

16KA for 2 sec

8kA for 2 sec.

8kA for 2 sec.

24KA for 2 sec

16KA for 2 sec

15kA for 2 sec.

Max. Value of duration of short circuit current

52 POWER TRANSFORMER - STANDARDISATION MANUAL

(-) 5.5 to 23 (+) 5.5 of HV

(-) 5.5 to 23 (+) 5.5 of HV

400/220/33 (1 ph)

400/220/33 (1 ph)

765/√3/ 400/√3/33

167

210

210

333.3 765/√3/ 400/√3/33

500

765/√3/ 400/√3/33

(-) 5.5 to 23 (+) 5.5 of HV

400/220/33

(-) 10 to (+) 10 of HV

(-) 10 to (+) 10 of HV

(-) 10 to (+) 10 of HV

17

17

17

1191.64

794.34

500.5

1010.4

795

1010

802

630

(-) 10 to (+) 10 of HV

17

400/220/33

505.2

401

17

500

(-) 10 to (+) 10 of HV

400/220/33

17

315

(-) 10 to (+) 10 of HV

400/220/33

250

1200

1000

600

1200

1000

1200

1000

600

500

2760

2760

2760

2886

2886

2886

2886

2886

2886

3000

3000

3000

3000

3000

3000

3000

3000

3000

Star

Star

Star

Star

Star

Star

Star

Star

Star

Reversing

Reversing

Reversing

Reversing

Reversing

Reversing

Reversing

Reversing

Reversing

230/550

230/550

230/550

460/1050

460/1050

460/1050

460/1050

460/1050

460/1050

100/460

100/460

100/460

100/460

100/460

100/460

100/460

100/460

100/460

15/90

15/90

15/90

15/90

15/90

15/90

15/90

15/90

15/90

16KA/2 sec

16KA/2 sec

8KA/2 sec

16KA/2 sec

16KA/2 sec

16KA for 2 sec.

16KA for 2 sec.

8kA for 2 sec.

8kA for 2 sec.

Neutral End of HV Winding

Neutral End of HV Winding

Neutral End of HV Winding

220 kV End of Series Winding

220 kV End of Series Winding

220 kV End of Series Winding

220 kV End of Series Winding

220 kV End of Series Winding

220 kV End of Series Winding

POWER TRANSFORMER - STANDARDISATION MANUAL

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POWER TRANSFORMER - STANDARDISATION MANUAL

ANNEXURE 2.3 Precautions required to be taken during installing tank tap-changer at site 1.

Check that the unit serial number of drive mechanism, gear boxes are identical to that of tap changer

2.

Check that the tap changer and drive mechanism are at same tap position

3. Ensure proper coupling of drive mechanism and tap changer without disturbing gearbox setting to avoid any misalignment. Refer OLTC Manual 4.

Connect earth screw of tap changer head and its
cover to transformer cover using earth conductor

5.

Connect earth screw of motor drive housing to transformer tank using earth conductor

6.

Apply vacuum to transformer and diverter chamber

7.

Fill diverter compartment with new filtered mineral oil and vent air from compartment and suction pipe

8. Check, if all stop valves between the oil conservator and driving unit (head) of the OLTC are open 9.

Check the oil tightness of the seals on the driving unit (head), protective relay and piping

10. Avoid dropping of any parts or objects into the diverter switch oil compartment 11. Operate manually tap changer for one full cycle. Check end limit stops 12. Operate one cycle electrically and ensure motor drive direction of rotation and continuity 13. Check the protective relay mounting and ensure its contacts are connected in tripping circuit of the main circuit breaker

POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 2 Design and Engineering features

(3) Standard Bushings for Power Transformers

Working Group Members Ms. Elizabeth Johnson - ALSTOM Ltd Mr. M. Vijayakumaran - ALSTOM Ltd Mr. Manish Jain

- ABB Ltd

Mr. Shailesh Mahajan - CGL Mr. Aseem Dhamija

- BHEL

Mr. Sai Prasad

- T&R

55

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POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

Part 3 - Standard Bushings for Power Transformers INTRODUCTION Standard Specifications of bushings used in Transformers up to 1200 kV class are given in Section II of CBIP Manual on Transformers (Publication No. 317). The Section also purports to standardise dimensions of condensers bushings from 52 kV to 1200 kV with a view to enable interchangeability with different makes of bushings. These recommendations have also been adopted in IS: 12676. The dimensional parameters of the bushings up to and including 36 kV voltage class (solid porcelain bushings) have already been standardised in IS: 3347. Beside standard dimensions, CBIP Manual also recommends standard values of BILs & test levels, creepage distances, current ratings, BCT, top and bottom terminations etc. This IEEMA Standard on bushings addresses selection criteria for bushings for transformers and suggests standard bushings to be used for popular rating transformers standardised by CBIP working group. These guidelines are prepared to enable user / manufacturer of the transformer to specify / use standard bushings for the transformers. If a non-standard bushing is specified / used, the same shall be subject to mutual agreement. SCOPE This standard covers Outdoor type Standard Bushings comprising outdoor Oil Impregnated Paper (OIP) bushings with values of highest system voltage for equipment (Um) from 52 kV up to 1200 kV voltage class and solid porcelain and oil communicating type bushings for voltage class up to 36 kV for use in oil filled Power Transformers popularly used in the country. 1. General Requirements and Selection Criteria of Standard Bushings §§

The condenser bushings shall conform to IEC 60137 / IS: 2099 / IS: 12676 and porcelain bushings shall conform to IS: 3347.

§§

Unless otherwise specified, the glaze of porcelain shall be brown in colour.

§§

All exposed ferrous metal parts shall be hot dip galvanized, wherever possible.

§§

No arcing horns shall be provided on bushings unless otherwise specified.

§§

Any stress shield shall be considered as an integral part of the bushing assembly for external clearances and field plotting.

§§

Preferred lead arrangements for condenser bushings upto 800 Amps shall be draw lead type, upto 1250 Amps, shall be draw rod and 2000 Amps and above, in all cases shall be stem type. However, 52 kV and 72.5 kV condenser bushings shall be solid stem type for all current ratings as standardised by CBIP .

§§

For 100 kV and 110 kV class transformers also, 145 kV class bushing is recommended for the purpose of variety reduction.

§§

Make of the condenser bushings shall be approved by customer. However, dimensionally they shall conform to CBIP Manual section II. Porcelain bushings are generally assembled by Transformer Manufacturers (porcelain and copper parts are purchased separately and assembled, porcelain conforming to IS:3347).

§§

The standard current ratings have been adopted. Minimum current rating of bushing is greater than or equal to the maximum winding current × 1.2 or as mutually agreed.

§§

The neutral bushing not intended to carry load between phase and neutral is dimensioned for earth fault current (except single phase transformer) unless otherwise specified by the customer.

§§

The lead joint in case of draw-lead or draw-rod type condenser bushings shall be as per fig 2 (a) & (b) of CBIP Manual (section II). The bottom portion of the joint shall be in flush with the bottom of the flange of the bushing. The top portion of the lead shall be transported with the bushings. The winding end of the lead joint shall be suitably anchored while transporting the transformer.

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POWER TRANSFORMER - STANDARDISATION MANUAL

2.

§§

The minimum value of creepage distance specified is 25 mm/kV of the rated voltage of bushing up to 1200 kV class.

§§

For areas with very heavy or extremely heavy pollution, the minimum creepage distance shall be 31mm/kV or as specified by the user.

§§

Bushing Current Transformer (BCT): To accommodate the bushing current transformers, space provided on various voltage class bushings shall be as under: Voltage class (kV)

BCT length (mm)

52

100 300

72.5

100 300

145

300 600

245

300 600

420

400

800

600

1200

300

§§

Altitude:



Bushings corresponding to this standard are suitable for operation at any altitude not exceeding 1000 M. In order to ensure that the external withstand voltages of the bushings are sufficient at altitudes exceeding 1000 M, the arcing distance normally required shall be increased by a suitable amount. The arcing distance correction shall be done as per clause No. 5.2 of IEC 60317.

§§

Short time current rating of the bushings shall be 25 times of the rated current of the bushings for 2 seconds.

Standard Bushings and their Application a.

Condenser Bushings for line terminals:



The basic insulation level, rated voltage, rated current and creepage distances for various voltage class condenser bushings are as under:

Voltage rating (kV) 72.5

Insulation Level LI / SI / AC (kV)

350 / NA / 155

Current rating (A)

Type of lead

Creepage distance (mm)

Remarks

800

Solid Stem

1815

1250

Solid Stem

66 kV winding of 100 MVA, 220/66 kV transformer

3150

Solid Stem

66 kV winding of high rating transformers above 100 MVA e.g. 160 MVA, 220/66kV

66 kV winding of 20 MVA, 66kV class transformer (also used for neutral of 220 kV class for the purpose of IOV test).

POWER TRANSFORMER - STANDARDISATION MANUAL

Voltage rating (kV) 145

245

420

Insulation Level LI / SI / AC (kV) 650 / NA / 305

1050 / 850 / 505

1425 / 1050 / 695

Current rating (A)

Type of lead

Creepage distance (mm)

800

Draw lead

3625

1250

Draw Rod

132 kV class transformers up to 200 MVA, 3 phase. (e.g. 200 MVA, 220 / 132 kV auto transformer and 160 MVA 220 / 132 kV auto transformer)

2000

Solid Stem

132 kV winding of Higher rating (e.g. 250 MVA, 220 / 132 kV auto transformer)

1250

Draw rod

2000

Solid stem

1250

Draw Rod

2000

Solid Stem

400 kV single phase generator transformers of 260 and 315 MVA

2500

Solid stem

400 kV winding of 500 MVA, single phase, 765/√3 / 400/√3 / 33 kV, auto transformer

6125

Remarks

132 kV winding of transformers up to 100 MVA, 3 phase. (e.g. 100 MVA, 220/132/11 kV auto transformer and 50 MVA, 132/33 kV two winding transformer)

220 kV class transformers up to 315 MVA, 3 phase. (e.g. 315 MVA, 220 kV GSU or 315 MVA, 400 / 220 kV auto transformers) 400 / 220 kV class transformers of 500 and 630 MVA, 3 phase.

10500

315 MVA and 500 MVA, 400 kV class, 3 phase, auto transformers

800

2100 / 1550 / 970

2500

Solid Stem

20000

500 MVA, single phase, 765/√3 / 400/√3 / 33 kV auto transformer and 260 & 333 MVA, 1 phase, 765 kV class, GSU

1200

2400 / 1950 / 1320 2500

Solid Stem

30000

1000 MVA, single Phase, 1150/√3 / 400/√3 / 33 kV auto transformer

b) Condenser bushings for tertiary winding: §§

33 kV tertiary in 400 kV & above kV class transformer is designed for 250 kVp transferred surges. Hence, 52 kV class bushings shall be used in such cases. The standard 52 kV bushings are as follows: Voltage rating (kV) 52

Insulation Level LI / AC (kV) 250 / 105

Current rating (A)

Type of lead

3150

Solid stem

5000

Solid stem

Creepage distance (mm) 1300

Remarks

a) 33 kV tertiary winding of 315 MVA and 500 MVA, 3 phase, 400 / 220 / 33 kV auto transformer. b) 167 MVA, 1 phase, 400/√3 / 220/√3 / 33 kV, auto transformer. a) 33 kV tertiary winding of 500 MVA, 1 phase, 765/√3 / 400/√3 / 33 kV auto transformer b) 33 kV tertiary winding of 1000 MVA, 1 phase, 1150/√3 / 400/√3 / 33 kV auto transformer (2 Nos. per phase)

59

60

POWER TRANSFORMER - STANDARDISATION MANUAL

c) Porcelain bushings for tertiary winding §§

11 kV as well as 33 kV class tertiary windings of 220 kV & below class, auto transformers are designed for 170 kVp transferred surges. Hence, 36 kV class porcelain bushing shall be used in such cases.

§§

In case of stabilizing winding of auto transformer, 1/3rd of equivalent 2 winding rating shall be considered for calculation of bushing current.

§§

These porcelain bushings are also to be used for 33 kV winding of double wound transformer with and without tertiary winding.

§§

For 11 kV and 22 kV class, 36 kV bushings only are standardised of current ratings 1000 amps, 2000 amps and 3150 amps.

§§

In case of stabilizing winding of auto transformer, 4 bushings shall be used for testing. After testing only 2 bushings, forming the corners of the delta, shall be provided. They will be externally shorted and earthed to the tank.

§§

In case of loaded tertiary only 3 bushings shall be provided for testing as well as for site use. Voltage rating (kV) 36

d)

Type of lead

Creepage distance (mm) 900

Remarks

1000

Solid Stem

25 / 31.5 MVA, 132/22 kV, 132/33 kV, double wound transformers.

2000

Solid stem

11 & 33 kV stabilizing windings of auto transformers up to 200 MVA. e.g. i) 200 MVA, 220/132/11 or 33 kV, 3 phase, auto transformers ii) 160 MVA 220/132/11 or 33 kV, 3 phase, auto transformers iii) 100 MVA, 220/132/11 kV 3 phase, auto transformers iv) 25 MVA 132/11 kV double wound transformer

3150

Solid stem

3 phase auto transformers of 160 MVA and above, using 11 kV tertiary. (e.g. 160 & 200 MVA, 220/132/11 kV auto transformer and 50 MVA, 132/11 kV 3 phase, double wound transformer).

Bushings for neutral end terminal Voltage rating (kV)

Current rating (A)

Type of lead

Creepage distance (mm)

Remarks

36

1000

Solid stem

900

Up to 315 MVA, 3 phase, transformers (auto as well as double winding)

2000

Solid stem

§§

e)

Current rating (A)

3 phase, auto transformers of 500 MVA and above (auto and double winding).

During testing, 72.5 kV, 800 Amp condenser bushing can be used where neutral receives 1/3rd voltage during IOV test. e.g. 132 and 220 kV class transformers. However, after testing 72.5 kV test bushing is to be replaced by 36 kV neutral bushing. For 400 kV transformer, where ACSD test is specified, neutral test bushing shall be 145 kV, 800 Amp.

Bushings for LV of generator transformers §§

LV voltages of GTs are typically 11 kV, 13.8 kV, 15.75 kV and 21 kV.

§§

For all these voltages, 24 kV porcelain bushings, oil communicating type have been standardised. The standard current bushings selected are 8, 12.5, 16 & 20 kA. In case of non availability of 16/20 kA bushings, 8/12.5 kA bushings, 2 in parallel can be used.

POWER TRANSFORMER - STANDARDISATION MANUAL

§§

In certain cases, high current 36 kV condenser bushings can also be used, subject to mutual agreement.

§§

When LV bushings are housed in busduct, suitable derating factor to be considered for current rating. Voltage rating (kV)

24

24

Current rating (kA)

Type of lead

Creepage distance (mm)

8

Solid stem

600

12.5

Solid stem

16

Solid stem

20

Solid stem

Remarks

i) 100 MVA, 3 phase, GT with LV winding of 11 kV. ii) 150 MVA, 3 phase, GT with LV winding of 13.8 kV. iii) 82 MVA, 1 phase, GT with LV winding of 15 kV. i) 150, 200 and 250/260 MVA 3 phase, GT with LV winding of 11, 13.8 and 15.75 kV respectively. ii) 200 MVA 1 phase, GT with LV winding of 21 kV. iii) 105 MVA 1 phase, GT with LV winding of 11 kV.

600

i) 250 MVA 3 phase, GT with LV winding of 11 kV ii) 260 MVA 1 phase, GT with LV winding of 21 kV iii) 315 MVA 3 phase, GT with LV winding of 13.8 kV and 15.75 kV. iv) 400 MVA 3 phase, GT with LV winding of 21 kV i) 315 MVA 1 phase, GT with LV winding of 21 kV ii) 600 MVA 3 phase, GT with LV winding of 21 kV iii) 315/333 MVA 1 phase, GT with LV winding of 21 kV

3.

Standard ratings of Bushings for transformers



Standard ratings of bushings for the transformers are as given in Table No.2.1.

61

kV ratio

132/33

132/11

132/11

132/66

132/66

11/138

13.8/138

15.75/138

220/66

220/66

220/33

220/33

220/132

220/132

220/132

11/235

MVA

16

25

31.5

50

63

140

140

250

50

100

50

100

100

160

200

140

(-) 10, (+) 15

(-) 5, (+) 15

(-) 5, (+) 15

(-) 5, (+) 15

(-) 10, (+) 10

(-) 10, (+) 10

(-) 10, (+) 10

(-) 10, (+) 10

(-) 10, (+) 5

(-) 10 , (+) 5

(-) 10 , (+) 5

(-) 5 , (+) 15

(-) 5 , (+) 15

(-) 15, (+) 5

(-) 15, (+) 5

(-) 15, (+) 5

Tapping range

351.43

524.86

419.9

262.43

291.6

145.8

291.6

145.8

1162.14

650.8

650.8

290

230.2

162.1

128.6

82.33

HV current Ihv

702.86

629.832

503.88

314.916

349.92

174.96

349.92

174.96

1394.57

780.96

780.96

348

276.24

194.52

154.32

98.796

1.2 × Ihv

245/1250A

245/1250A

245/1250A

245/1250A

245/1250A

245/1250A

245/1250A

245/1250A

145/1600A

145/800A

145/800A

145/800A

145/800A

145/800A

145/800A

145/800A

HV Bushing

NA

920.8

736.65

460.4

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

IV current IIV

NA

1104.96

883.98

552.48

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

1.2 × IIV

Table No. 2.1 Standard Bushings for Transformers

NA

145/1250A

145/1250A

145/800A

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

IV Bushing

7348.1

NA

NA

NA

1749.54

874.77

874.77

437.38

5291.21

3381.65

4242.42

551.01

437.38

1653.31

1312.15

279.92

LV current ILV

8817.72

NA

NA

NA

2099.448

1049.724

1049.724

524.856

6349.452

4057.98

5090.904

661.212

524.856

1983.972

1574.58

335.904

1.2 × ILV

36/12500A

NA

NA

NA

36/3150

36/1000A

72.5/1250A

72.5/800A

24/8000A

24/8000A

29/8000A

72.5/800A

72.5/800A

26/2000A

36/2000

36/1000

LV Bushing

62 POWER TRANSFORMER - STANDARDISATION MANUAL

kV ratio

15.75/235

15.75/235

24/420/√3

15.75/420

15.75/420

21/420/√3

400/132/33

400/132/33

400/220/33

400/220/33

400/√3/220/√3/33

400/√3/220/√3/33

21/765/√3

24/765/√3

765/√3/400/√3/33

765/√3/400/√3/33

765/√3/400/√3/33

MVA

250

315

260

250

315

200

100

200

250

315

167

210

200

260

210

333.3

500

(-) 5, (+) 5

(-) 5, (+) 5

(-) 5, (+) 5

(-) 5, (+) 5

(-) 5, (+) 5

(-)10, (+) 10

(-)10, (+) 10

(-)10, (+) 10

(-)10, (+) 10

(-)10, (+) 10

(-) 10, (+) 10

(-) 5, (+) 10

(-) 5, (+) 10

(-) 5, (+) 10

(-) 10, (+) 15

(-) 10, (+) 15

(-) 10, (+) 15

Tapping range

1191.64

794.35

500.5

619.6

476.65

1010.36

803.5

505.18

401

320.75

160.4

868.2

455.8

361.75

1191.35

859.8

682.4

HV current Ihv

1429.97

953.22

600.6

743.52

571.98

1212.432

964.2

606.216

481.2

385

192.48

1041.84

546.96

434.1

1429.62

1031.76

818.88

1.2 × Ihv

800/2500A

800/2500A

800/2500A

800/2500A

800/2500A

420/1250A

420/1250A

420/1250A

420/1250A

420/1250A

420/1250A

420/1250A

420/1250A

420/1250A

420/2000A

245/1250A

245/1250A

HV Bushing

2165.06

1443.36

909.32

NA

NA

1653.32

1314.78

826.66

656.08

874.77

437.38

NA

NA

NA

NA

NA

NA

IV current IIV

2598.072

1732.032

1091.184

NA

NA

1983.98

1577.74

991.992

787.3

1049.724

524.856

NA

NA

NA

NA

NA

NA

1.2 × IIV

420/2500A

420/2000A

420/1250A

NA

NA

245/2000A

245/2000A

245/1250A

245/1250A

145/1250A

145/800A

NA

NA

NA

NA

NA

NA

IV Bushing

5081

3366.66

2121.21

10833.3

9523.8

2121.2

1686.86

3181.8

2525.15

2020

1009.09

9523.8

11547

9164.29

10833.33

11547

9164.3

LV current ILV

6097.2

4039.992

2545.45

12999.96

11428.6

254544

2024.232

3818.16

3030.18

2424

1210.91

11428.56

13856.4

10997.15

13000

13856.4

10997.16

1.2 × ILV

52/5000A

52/5000A

52/3150A

36/16000

36/12500

52/5000A

52/3150A

52/5000A

52/5000A

52/3150A

52/3150A

24/12500A

24/16000A

36/12500

36/16000A

36/16000A

36/12500A

LV Bushing

POWER TRANSFORMER - STANDARDISATION MANUAL

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POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 2 Design and Engineering features

(4) Power Transformer Fittings and Accessories

Working Group Members Mr. M. L. Jain

- EMCO Ltd.

Mr. Rabindranath Mahapatro - EMCO Ltd. Mr. Bharat Panchal

- EMCO Ltd.

Mr. V. Janardhanan

- Precimeasure

Mr. S. R. Doraiswamy

- Perfect Controls

Mr. Vishal Shah

- Scientific Controls

Mr. Himanshu Choudhary

- Jadhao Engineers

Mr. K. Y. Daftary

- Hi-Tech Radiators

Mr. Jitendra Palnitkar

- Tarang Engg

Mr. Sujit Gupta

- Pradeep Sales & Service

Mrs. J. J. Patel

- EMCO Electronics

Mr. Vinay Gupta

- Atvus Industries

Mr. Atul Bapat

- Sukrut Udyog

Mr. D. M. Jadhav

- CTR

Mr. Rajesh Khanna

- SERGI

Mr. Mahendra Sule

- Lumasense

Mr. Jagdish Sandhanshiv

- Consultant

Mr. S. Paulraj

- Klemmen Engineering

65

66

POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

Part 4 - Power Transformer Fittings and Accessories INTRODUCTION All external components & fittings provided on the transformer tank form an integral part of the transformer and are essential for its satisfactory performance in service. Some essential fittings, which are mandatorily provided on a wide range of transformers, are listed in IS 2026 Part I. However, depending on the rating, some additional fittings and accessories are also provided on large rating transformers as per the specified requirement. This section covers various fittings & accessories that are generally provided on the 132 kV & above class of Power Transformers. As components with varying features are available commercially, in the absence of any authoritative guidelines, the users are often unable to clearly specify the items that would address their long term requirements. This section briefly covers some vital fittings and accessories as listed below, describing broadly the purpose of each fitting, its working principle, the data sheet, the selection criteria, the care to be taken during installation & commissioning, etc. While presently no single Standard comprehensively covers all the fittings and accessories, the British Standard BSEN 50216, which is divided in several parts, covers some of the vital components. Therefore, efforts have been made to broadly align details of the items covered herein with these standards and some other available references. However, for the users a list of some references is appended under ‘Bibliography’ for further details. Doc. No.

Type of Accessory

Purpose

Reference Standard

1

Temperature Indicators

BS EN 50216-11

1.1

Oil Temperature Indicator (OTI)

These instruments are installed in the marshaling box (in transformer yard) measurement of top oil temperature & winding hot spot indication

1.2

Winding Temperature Indicator (WTI)

1.3

Remote Temperature Indicator (ROTI/RWTI)

This is a repeater dial installed in the Control Room for remote indication of top oil temperature & winding hot spot temperature

BS EN 5021.6-11

1.4

RTD (PT 100) Scheme for ROTI / RWTI

RTD scheme, comprises RTD sensor, transducer and indicator is used for measurement of oil and winding temperatures of the transformers

BS EN 5021.6-11

2

Fiber Optic Temperature Sensor (FOS)

For real time measurement of winding hotspot temperatures

IEC 60076-2

3

Gas & Oil Actuated Relay (Buchholz Relay)

Fitted in the pipe between tank and the conservator to actuate alarm & trip relays in the event of accumulation of gas generated due to fault inside the transformer

BS EN 50216-2

4

Pressure Relief Valve (PRV)

Fitted on the tank cover to limit the tank over pressure on an internal fault, thereby reducing risk of tank rupture or uncontrolled spillage of oil

BS EN 50216-5

5

Magnetic Oil Level Gauge (MOG)

Fitted on the main tank conservator and OLTC conservator for indication of oil level

BS EN 50216-5

6

Oil / Water Flow Indicators (FI)

Fitted in the oil/water cooling pipe line for the control of the oil/ water flow out of the pumps on transformer with forced oil/ water cooling equipment

BS EN 50216-5

7

Air Cell / Flexi-Separator

Installed inside the conservator as a barrier to prevent contact between atmospheric air and the transformer oil

-

8

Conservator Protection Relay (CPR)

Also called ‘air cell puncture detection relay’, is externally installed on the top of conservator to give alarm in the event of lowering of oil in the conservator due to puncture of air cell in service

-

67

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POWER TRANSFORMER - STANDARDISATION MANUAL

9

Removable Radiators for oilimmersed transformers

These are directly/separately mounted on the tank to permit flow of hot oil through it for cooling and returning to tank

BS EN 50216-6

10

Automatic Voltage Regulating Relay (AVR)

Provided in the RTCC (Remote tap changers control cubicle) & connected to OLTC to maintain a constant secondary voltage at all times

-

11

Fire Fighting Systems

11.1

Nitrogen Injection Fire Prevention System (NIFPS)

Installed in the vicinity of main transformer to protect it against catching of fire/spread of fire in the event of internal failure of transformer or external fire in the close vicinity

CEA -The Gazette of India, 2010

11.2

Automatic Water Mulsifier System

12

Terminal Connector

Used for connection of transformer to the overhead power line.

IS: 5561

Attempts have been made to standardise some vital fittings & accessories used for power transformers to facilitate interchangeability & to rationalize their use such as would be commonly acceptable to manufacturers & users. It may be noted that the above list is not exhaustive. Some items, like cooing fans, oil/water pumps, pressure gauges, RTD, valves, breathers, rollers, earthing terminals, heat exchangers, unit coolers, etc. are presently not covered here and could be considered in the subsequent revisions in future.

1

Temperature Indicators 1.1 Oil Temperature Indicator (OTI) 1.1.1 Description

This is used to measure the temperature of top oil in transformer.

1.1.2 Principle of Operation

The top oil temperature of oil immersed power transformer is sensed by mMeasuring system based on volumetric expansion of liquid proportional to rise in temperature. A sensing bulb, measuring bellow and a small bore capillary connecting the two form the measuring system which is filled with liquid. When the sensing bulb is exposed to rise in temperature, the liquid inside expands proportionately causing the bellows to expand and drive the linkages for indication and separately, linkages & disc for switch operation. This system is self contained and does not depend on any outside power source for its operation.



Complete ambient temperature compensation on sensing bulb & line / capillary is provided with a second bellow / compensating bellow and a capillary that terminates at head of the sensing bulb. The liquid filled inside this responds to ambient temperature changes. The measuring and compensating bellows are linked in such a way that they cancel out. Thus, the net measuring bellow output is dependent only on the sensing bulb temperature and not on ambient temperature.

1.1.3 Data Sheet Technical Parameters Parameter

Variant - 1

Variant – 2

Dial Range

0 to 150 °

0 to 150 °

Dial angular sweep

270 °

270 °

Case shape

Rectangular

Rectangular

Paint detail of case

Powder coated, RAL7032

Powder coated, RAL7032

Graduation

2 °C

2 °C

POWER TRANSFORMER - STANDARDISATION MANUAL

Parameter

Variant - 1

Variant – 2

Accuracy class

±1.5 % FSD

±1.5 % FSD

No. of micro switches

2 Nos. Change over

2 Nos. Change over

Contact rating

15A, 250V AC & 0.25A at 250V DC

15A, 250V AC & 0.25A at 250V DC

Switch differential

6°C to 8°C (Fixed)

6°C to 8°C (Fixed)

Switching accuracy

±4°C of Set Value

±4°C of Set Value

Switch adjustable range

Independently adjustable to close between 30-150°C

Independently adjustable to close between 30-150°C

With built-in RTD (PT100) and CCU

Not Available

Available

External PSU with 2Nos. of 4-20mA DC outputs

Not Available

Available

Bulb

1” BSP with male type union (Fig.2.1)

1” BSP with male type union (Fig.2.2)

Material

Case - Cast Aluminum; Bulb - Brass with silver joint, natural finish; Bellows - Phosphor Bronze, natural finish; Capillary - Stainless Steel Armour sheathed copper capillary; Window - clear and transparent Polycarbonate

Case -Cast Aluminum; Bulb - Brass with silver joint, natural finish; Bellows - Phosphor Bronze, natural finish; Capillary - Stainless Steel Armour sheathed copper capillary; Window - clear and transparent Polycarbonate

Capillary & electrical entry

From the bottom of OTI

From the bottom of OTI

Dial marking

Black with white back ground

Black with white back ground

Resettable maximum reading pointer

Red in colour

Red in colour

Degree of protection

IP:55

IP:55

Immune to vibration of switches

Yes

Yes

Notes:

1) 4 to 20mA correspond to 0 to 150 °C respectively. 2) In case of failure of analog type indicator (Variant-2), PSU will give continuous 4 to 20mA output.

Fig. 2.1: Bulb fitting arrangement for Variant 1

Fig. 2.2: Bulb fitting arrangement for Variant 2

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POWER TRANSFORMER - STANDARDISATION MANUAL

1.1.4 Standard Wiring Diagram

Any one of the following terminal configurations can be selected as per requirement. The contact position shown below is under normal operating condition of OTI.

Variant - 1

Variant - 2

1.1.5 Selection criteria

4 to 20 mA output required or not for remote/SCADA indication

1.1.6 Routine Tests a)

Mount the temperature Indicator on Test Stand Vertically,

b)

Connect as per scheme diagram.

c)

Micro switch terminals with multimeter / Buzzer (Continuity test).

d)

“Thermal image” bellow heater terminal (CT Terminal) with current source

e)

Close the Top cover

f)

Set oil bath temperature at 40°C, with reference to the standard Thermometer.

g) Loosen union screw and remove the union (Ensure minimum immersion length of 140 mm). Immerse sensing bulb in hot oil bath. h)

Record the instrument temperature after 5 minutes, the bath reaches the steady temperature.

i)

Increase the oil bath temperature in steps of 20°C and record the temperature of the instrument after 5 minutes when the bath reaches the steady state temperature.

j)

Simultaneously observe and record the switch operation (ON) as instrument temperature rises.

k)

Remove the sensing bulb from oil bath and keep in ambient temperature till the instrument reading reaches the ambient temperature.

l)

Simultaneously observe and record the switch operation (OFF) as instrument temperature decreases (To check switch differential)

m) Insulation Test (2 kV between contact and earth) 1.1.7 Installation and Pre-commissioning checks i.

Before installation, check for possible damages from transport handling.

ii.

Do not carry the instrument by holding the capillary line.

iii. Ensure not to twist the capillary line while unpacking, storage or installation. iv. Avoid sharp bends of capillary line and allow minimum of 50 mm bending radius. v.

Keep the instrument on mounting surface and fix it.

vi. Make sure that instrument is mounted in a vertical position. vii. Clamp the capillary line along its entire length at approximately 500 mm intervals. The excess length can be wound in spiral with minimum diameter of 100 mm.

POWER TRANSFORMER - STANDARDISATION MANUAL

viii. Oil is to be filled in the pocket. Insert the sensing bulb through union/ pocket/ flange (insert fully), tighten nut to optimum level. Ensure min. immersion length 140 mm. ix. Care must be taken that, Sensing bulb is not damaged while tightening. x.

In case of further transport or storage, wind the armor and pack the instrument in the same way as received from the supplier.

xi. Check the connection as per wiring diagram before commissioning. xii. Cable entry should be through cable gland to avoid dust entering xiii. Top cover should be put in place and tighten properly to avoid dust. Ensure that the maximum pointer is positioned after the indicating pointer. xiv. Make sure there are no loose connections. xv. Test knob, if provided externally, shall be locked properly after testing.

1.2 Winding Temperature Indicator (WTI) 1.2.1 Description

This is used to measure the hotspot temperature of the winding.

1.2.2 Principle of Operation

The top oil temperature of Oil Immersed Power transformer is sensed by measuring system based on volumetric expansion of liquid proportional to rise in temperature. A Sensing bulb, measuring bellow and a small bore capillary connecting the two form the measuring system which is filled with liquid. When the sensing bulb is exposed to rise in temperature, the liquid inside expands proportionately causing the bellows to expand and drive the linkages for indication and separately, linkages & disc for switch operation. This system is self contained and does not depend on any outside power source for its operation.



Complete ambient temperature compensation on sensing bulb & line/capillary is provided with a second bellow/compensating bellow and a capillary that terminates at head of the sensing bulb. The liquid filled inside this responds to ambient temperature changes. The measuring and compensating bellows are linked in such a way that they cancel out. Thus, the net measuring bellow output is dependent only on the sensing bulb temperature and not on ambient temperature.



The winding temperature is simulated by passing CT secondary current (from the transformer line) to an electrical heater coil fitted around the measuring bellows. This simulates the winding to top oil temperature differential which is added to the top oil temperature, being measured by the instrument bulb. The temperature in the hottest part of the winding or hotspot temperature is displayed directly by the instrument. Thus, the instrument functions as a winding temperature indicator. The time constant of the temperature rise will be 63.7% of final temperature rise within 7-8 minutes.



Since the thermal time constant of the heater coil is nearly the same as the transformer winding, the instrument simulates closely the actual temperature of the winding in relation to time.



The primary current of CT feeding the thermal image of WTI shall be of rated transformer current corresponding to lowest tap and secondary nominal output of 2A. The heating system of WTI shall be designed for a winding gradient of 35°C at CT current input of 2A. It shall be designed to operate continuously at 150% of the rated current and shall not suffer injurious overheating with 200% of rated current for a period of 15 minutes. Based on the heat run test data, the parallel shunt resistor to heater coil shall be adjusted by transformer manufacturer such that the current through heater coil will correspond to the winding hotspot gradient as per the heat run test result.

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POWER TRANSFORMER - STANDARDISATION MANUAL

1.2.3 Data Sheet Technical Parameters





Parameter

Variant - 1

Variant - 2

Dial Range

0 to 150 °

0 to 150 °

Dial angular sweep

270 °

270 °

Case shape

Rectangular

Rectangular

Paint detail of case

Powder coated, RAL7032

Powder coated, RAL7032

Graduation

2 °C

2 °C

Accuracy class

±1.5% FSD

±1.5% FSD

No. of micro switches

4 Nos. change over

4 Nos. change over

Contact rating

15A, 250V AC & 0.25A @ 250V DC

15A, 250V AC & 0.25A @ 250V DC

Switch differential

6°C to 8°C (Fixed)

6°C to 8°C (Fixed)

Switching accuracy

±4°C of Set Value

±4°C of Set Value

Switch adjustable range

Independently adjustable to close between 30-150°C

Independently adjustable to close between 30-150°C

With built-in RTD (PT100) and CCU

Not Available

Available

External PSU with 2 Nos. of 4-20 mA DC outputs

Not Available

Available

Bulb

1” BSP with Male type union (Fig.2.3)

1” BSP with Male type union (Fig.2.4)

Material

Case - Cast Aluminium; Bulb - Brass with silver joint, natural finish; Bellows - Phosphor Bronze, natural finish; Capillary - Stainless Steel Armour sheathed copper capillary; Window - clear and transparent polycarbonate

Case - Cast Aluminium; Bulb - Brass with silver joint, natural finish; Bellows - Phosphor Bronze, natural finish; Capillary - Stainless Steel Armour sheathed copper capillary; Window - clear and transparent polycarbonate

Capillary & electrical entry

From the bottom of OTI

From the bottom of OTI

Dial marking

Black with white back ground

Black with white back ground

Resettable maximum reading pointer

Red in colour

Red in colour

Degree of protection

IP:55

IP:55

Immune to vibration of switches

Yes

Yes

Notes:

1) 4 to 20 mA correspond to 0 to 150 °C respectively. 2) In case of failure of analog type indicator (Variant-2), PSU will give continuous 4 to 20 mA output.

POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 2.3: Bulb fitting arrangement for Variant 1

Fig. 2.4: Bulb fitting arrangement for Variant 2

1.2.4 Standard Wiring Diagram

Any one of the following terminal configurations can be selected as per requirement.



The contact position shown below is under normal operating condition of WTI.

Variant - 1:

Variant - 2:

1.2.5 Selection criteria

4 to 20 mA output for remote/SCADA indication - Yes / No.

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1.2.6 Routine Tests a)

Mount the temperature indicator on test stand vertically,

b)

Connect as per scheme diagram. §§ Micro switch terminals with multimeter / Buzzer (Continuity test). §§ “Thermal image” bellow heater terminal (CT Terminal) with current source

c)

Close the Top cover.

d)

Set oil bath temperature at 40°C, with reference to the standard Thermometer.

e) Loosen union screw and remove the union (Ensure minimum immersion length of 140 mm). Immerse sensing bulb in hot oil bath. f)

Record the instrument temperature after 5 minutes, the bath reaches the steady temperature.

g)

Increase the oil bath temperature in steps of 20°C and record the temperature of the instrument after 5 minutes when the bath reaches the steady state temperature.

h)

Simultaneously observe and record the switch operation (ON) as instrument temperature rises.

i)

Remove the sensing bulb from oil bath and keep in ambient temperature till the instrument reading reaches the ambient temperature.

j)

Simultaneously observe and record the switch operation (OFF) as instrument temperature decreases (To check switch differential).

k)

Insulation test (2 kV between contact and earth).

1.2.7 Installation and Pre-commissioning Checks a)

Before installation, check for possible damages from transport handling.

b)

Do not carry the instrument by holding the capillary line.

c)

Ensure not to twist the capillary line while unpacking, storage or installation.

d)

Avoid sharp bends of capillary line and allow minimum of 50 mm bending radius.

e)

Keep the instrument on mounting surface and fix it.

f)

Make sure that instrument is mounted in a vertical position.

g)

Clamp the capillary line along its entire (3/4) length at approximately 500 mm intervals. The excess length can be wound in a spiral with a min diameter of 100 mm.

h)

Oil is to be filled in the pocket. Insert the sensing bulb through union / pocket / flange (insert fully), tighten nut to optimum level.

i)

Care must be taken that sensing bulb is not damaged while tightening.

j)

In case of further transport or storage, wind the armor and pack the instrument in the same way as received from the supplier.

k)

Check the connection as per wiring diagram before commissioning.

l)

Cable entry should be through cable gland to avoid dust entering

m) Top cover should be put in place and tighten properly to avoid dust. Ensure that the maximum pointer is positioned after the indicating pointer. n)

Make sure there are no loose connections.

o)

Set the Hot oil bath temperature at 60°C/75°C, Immerse the sensing bulb.

p)

Inject the rated current as per requirement or graph for 40 minutes, and check the temperature rise of winding temperature over oil temperature.

q)

Test knob, if provided externally, shall be locked properly after testing.

POWER TRANSFORMER - STANDARDISATION MANUAL

1.3 Remote Oil / Winding Temperature Indicator (ROTI/RWTI) 1.3.1 Description

This is used to measure the temperature of oil / winding at the remote control panel.

1.3.2 Principle of Operation

This system takes 4 to 20 mA, DC analog input from the local OTI / WTI and caliberate the same in terms of degrees C to repeat the temperature of local OTI / WTI on the remote control panel

1.3.3 Data Sheet

The different types of Remote Temperature indicators are as follows: Technical Parameters Parameter

Variant - 1

Variant - 2

Variant - 3

Type

Digital (96 sq mm)

Digital (96 sq mm)

Digital (96 sq mm)

Auxiliary Supply

90 – 260V AC/DC

90 – 260V AC/DC

90 – 260V AC/DC

Temperature Range

0 – 150 °C

0 – 150 °C

0 – 150 °C

Temperature Indicator

3½ digits 7-segement LED display red in colour

3½ digits 7-segement LED display red in colour

3½ digits 7-segement LED display red in colour

Accuracy of the system

± 1% FSD (of local OTI / WTI)

± 1% FSD (of local OTI / WTI)

± 1% FSD (of local OTI / WTI)

Warm up time after switching ‘ON’

15 Minutes (Minimum)

15 Minutes (Minimum)

15 Minutes (Minimum)

Input

4 to 20 mA DC

4 to 20 mA DC

4 to 20 mA DC

No. of 4 - 20 mA Output

4

1

1

Alarm & Trip Contacts

Not Available

Available (1 No. each)

Not Available

RS485 port module

Not Available

Not Available

Available

Degree of Protection of enclosure

IP 20

IP 20

IP 20

Note: 4 to 20 mA corresponds to 0 to 150 °C respectively.

1.3.4 Standard Wiring Diagram

Any one of the following terminal configurations can be selected as per requirement. The contact position shown below is under normal operating condition.

Variant 1

Variant 2

Variant 2

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1.3.5 Selection criteria §§

No. of 4 to 20 mA output - Yes / No

§§

Alarm & trip contacts - Yes / No

§§

RS485 port module - Yes / No

1.3.6 Tests a)

HV Test: All mA terminals shall be tested for 500V AC, 50Hz for one minute. All other terminals shall be tested for 2kV AC, 50Hz for one minute.

b) I.R. Test: Insulation resistance shall be ≥ 20 Meg. Ohms when checked by 500V DC Insulation Tester. 1.3.7 Installation and pre-commissioning checks a)

Check the proper electrical earthing.

b) Use shielded cable for input signals c) Ensure that input signal and power cables are isolated. d) Make sure the proper supply voltage is applied. e) Switch off the power supply while wiring. f) Ensure tightness of all the contacts. 1.4 RTD (PT100) Scheme for ROTI / RWTI 1.4.1 Description

This scope covers the standard specifications of the PT100 Resistance Temperature Detector (RTD) Oil Temperature indicator (OTI) and Winding Temperature indicator (WTI) for use with liquid immersed power transformers and reactors for indoor or outdoor installation.

1.4.2 Oil Temperature Indicator

The system measures the top oil temperature of oil immersed transformer with the PT100 RTD sensor and transmits the measured values to a remote point by dc current mode signal.

1.4.3 Principle of Operation

The PT100 sensor is mounted in an oil filled pocket located in the hottest oil zone of the transformer. The PT100 resistance in the sensor changes with the change in the top oil temperature. The Transducer (Resistance to Current Converter Unit) measures the variations in the Sensor Resistance (corresponding to the top oil temperature) and produces two independent channels of 4-20 mA dc current output signals directly proportional to the PT100 sensor resistance.

Fig. 2.5: Block Diagram of PT100 ROTI – Dual Output Channel

POWER TRANSFORMER - STANDARDISATION MANUAL

1.4.4 Winding Temperature Indicator

The system measures the Top Oil temperature of oil immersed transformer with the PT100 RTD sensor, simulates the Winding hot-spot temperature with a thermal imaging device & transmits the measured value to a remote point by dc current mode signal.

1.4.5 Principle of Operation

Thermal Imaging method:



The PT100 Sensor assembly is mounted in an oil-filled pocket located in the hottest oil of the transformer. A Heater Coil (H) and Shunt (RS) assembly either mounted in the PT100 sensor assembly (as shown in Fig. 2.6) or in the Transducer (as shown in Fig. 2.7) is fed with current from a CT placed in the transformer load circuit. The Heater simulates the hot-spot Temperature rise of the winding over the top oil temperature corresponding to the transformer load current. The PT100 Sensor assembly reacts to this simulated temperature rise in addition to the top oil temperature. To obtain precise thermal image, a portion of the current through the Heater is shunted through a calibrating Shunt Resistor. The thermal time constant of the Heater is nearly the same as that of the transformer winding. Hence, the Sensor assembly simulates closely the actual hot-spot temperature of winding in relation to time.



The Resistance to Current Converter Unit (Transducer) measures the variations in the Sensor Resistance corresponding to top oil plus simulated windings hot spot temperature and produces a directly proportionate two independent channels of 4-20 mA dc current output signals.

Fig. 2.6: Block diagram of PT100 RWTI – Dual Output Channel Thermal Sensing Method - Scheme 1.

Fig. 2.7: Block diagram of PT100 RWTI – Dual Output Channel Thermal Sensing Method - Scheme 2.

1.4.6 Data sheet & selection criteria Sl No

Description

Specification

1

Sensor

PT100 3-Wire Sensor (Simplex/Duplex)

2

Union

1” BSP Male type union (Fig. 2.8)

3

Sensor

As per figures 2.9 & 2.10

4

Sensing for Winding Hot spot temperature

Thermal Sensing

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Sl No

Description

Specification

5

Transducer

Resistance to Current Converter Unit

6

Power Supply

90-260V, ac/dc

7

Analog output

4-20 mA (single / dual optional)

8

Burdon on output

≥ 500 Ω

9

CT input

2 Amp

10

Temperature Rise/Gradient

The standard temperature gradient must be adjustable up to 35°C

11

Accuracy

±0.2 mA at any point of 4-20 mA suitable for 500 Ω burden including loop resistance.

12

Insulation Resistance

≥20MΩ Between Earth to all terminal when measured with 500 V DC Insulation tester

13

Isolation

2500Vrms, AC between Power all terminals to earth for 60 Sec

14

Warm Up time

15 minutes (minimum)

15

Ambient Temperature

0 to 50°C , 45 to 80% RH

16

Storing Temperature

-10°C to 60°C, 25 to 85% RH

17

Range

0-150°C

18

Panel Protection Level

IP40

19

Mounting

DIN Rail / Panel Mounting

Fig. 2.8

Fig. 2.9 Simplex Type Sensor

Fig. 2.10 Duplex Type Sensor

POWER TRANSFORMER - STANDARDISATION MANUAL

1.4.7 Tests 1.4.7.1 Routine Tests

a)

Temperature Vs Resistance: It is checked across PT100 sensor leads from 0-150°C using the test equipment and test procedure as per resistance table Annexed as Annexure 2.4.

b)

Temperature Vs Output Signal: Sensor, heater & shunt connected to Transducer and calibrated to Oil temperature Transmitter to the temperature range 0-150°C Output Signal 4-20 mA DC as per Annexure 2.5. Accuracy of each channel output signal ± 0.2 mA. Minimum settling time 40 minutes allowed before taking each step reading.



The same system calibrated as Winding Temperature transmitter by passing specified input current through heater & shunt network maintaining bath oil temperature at 80°C constant and allowing 40 minutes settling time as per CT Current Vs Gradient Graph. In the test reports for the system, the bath oil temperature 80°C plus simulated temperature rise for specified input current will be recorded. Accuracy of each channel output signal is ± 0.2 mA.

1.4.7.2 Type Tests a)

High Voltage Test: Test at 2500 Vrms, 50Hz for 60s. All Terminals to earth (case) Power Supply terminals to signal input/output terminals.

b) Insulation Resistance Test:

Measured at 500V dc under normal ambient temperature between all terminals and earth (enclosure) ≥ 20 Mega Ohms.

c) Soak test: Transducer Unit energized for a period of 72 hrs to simulate normal operating conditions for determining the input and output conditions and the functions performed during this period. 1.4.8 Transportation care

Instruments are to be properly packed with necessary buffers to prevent from any mechanical damage to the Thermal pocket, Transducer enclosure, Terminal block etc Utmost care to be taken to prevent the instrument from coming in contact with moisture, high temperature and sharp edges.

1.4.9 Storage care

Instrument should be stored in a dry and moisture-free place. Sensor, Transducer and Digital Indicators should be handled carefully so that they are not subjected to excessive mechanical force / falling down. Electronic Transducer and digital Indicator are to be stored in cool and dry place away from moisture and heat.

1.4.10 Installation care PT100 RTD sensor is to be installed in the thermometer pocket of the transformer after filling the pocket with transformer oil in the Pocket up to ¾ level. Transducer is to be fitted inside the control panel in the DIN rail / Panel mounting. Digital Indicator is to be fitted on the control panel by inserting it from the front and at the back using the screw fixing clamps.

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2

All the wiring is to be done as per the terminal marking on the instruments. Recheck the wiring before energizing the transformer specially the power supply connections. Ensure that the Loop resistance of the interconnecting cables does not exceed the specified burden of the Transducer analog output. Use independent 2.5 sq. mm cable between PT100 Sensor to Transducer and Digital Indicator. The 4-20 mA cable from Transducer to Remote indicator/SCADA should not run along with a power cable. No calibration required to be done at site. Calibration by user not to be attempted as it may damage the instrument.

Fibre Optic Sensors 2.1 Description

Fibre Optic Temperature Monitoring System comprising : §§ Fibre optic probes (Installed inside the transformer). §§ Tank wall plate. §§ External fibre optic extension cable §§ Measuring Instrument. §§ Instruction Manual.

2.2 Purpose Direct real time hotspot temperature measurement of windings, oil, and other parts of the core-coil assembly of power transformer. 2.3 Working Principle

Light signal, sent from the FOT instrument excites the sensor mounted at the tip of fibre optic cable (probe). Depending on the temperature at that point, the sensor sends a return signal which is correlated with the corresponding temperature by the FOT instrument and the same is displayed.

2.4 Installations of Sensors Sensors are placed in direct contact with the insulation of the winding conductors in the regions where the hot-spots are to be measured. The location for fixing the probes shall be decided by the transformer manufacturer based on the expected location of hotspots and shall be finalized by agreement with the Purchaser. 2.5 Temperature Range Temperature range of the system should be -30°C to +200°C & accuracy of ± 2°C with no need for recalibration for the entire life time of the FOT system. 2.6 Selection Criteria for number of sensors to be installed Reference: IEC Standard 60076-2: 2011 (Annex E) Minimum recommended number of sensors for three-phase transformers Rated power MVA

Cooling system

Number and phases of installation Total

On central phase

On each lateral phase

HV winding

LV winding

HV winding

LV winding

≥ 100

All system

8

2

2

1

1

From ≥ 20 to < 100

ON - OFF

6

1

1

1

1

OD

8

2

2

1

1

POWER TRANSFORMER - STANDARDISATION MANUAL



For single-phase transformers, the minimum recommended number of sensors for each wound column should be those indicated in the table below: Minimum recommended number of sensors for single-phase transformers



Rated power MVA

Cooling system

≥ 50

All system

Number of sensors Total

HV winding

LV winding

4

2

2

Besides the above, installation of at least one sensor is recommended for Top Oil temperature measurement. 2.7 Selection Criteria for Probes §§ The temperature sensing tip along with the fiber optic cable shall be of proven/type tested design. §§ They shall withstand exposure to hot kerosene vapour during the transformer insulation drying process (VPD). §§ Probes shall be compatible with hot transformer oil. §§ The probes shall be partial-discharge-free in the high electrical stress areas inside the transformer. §§ Probes shall be all silica, teflon jacketed fibre with perforations / slits in the outer jacket to allow complete oil filling.  The fibre with Teflon jacket shall be strong enough to withstand the severe conditions prevailing inside an EHV transformer. §§ The Fibre optic cables are to be brought out of the main tank through tank wall plate. The plate shall be welded / bolted on to the tank such that no oil leakage / moisture ingress will occur. §§ The tank wall plate shall be covered with a protection-hood to avoid accumulation of dust and water ingress. §§ The external fibre optic cable shall then be run to main control cabinet, routed through suitable conduits with large bend radius. 2.8 Selection Criteria for FOT Measuring Instruments. i. Analog Outputs 4 - 20 mA output for remote Indication or SCADA. ii. Relay Outputs Provision of min 6 programmable relays for Alarm/Trip and Cooling Control. iii. Communication Suitable computer interface and SCADA interface on IEC 61850 iv. Memory / Data Storage Suitable for recording of 3 months data at 1 reading / minute interval. 2.9 Tests

a) At FOS Supplier’s Works The FOS supplier shall provide the transformer manufacturers with the following test certificates: Type tests: §§ Dielectric tests on probes §§ Surge test for FOT measuring instrument as per IEEE C37.90.1-1989 Routine tests: §§ Calibration



b) At Transformer manufacturer’s Works during transformer manufacturing §§ Temperature rise (Heat Run) testing if specified by end customer: Measurements shall be made with the FOT measurement system.  The equipment shall be operational during temperature rise test and the data shall be recorded.  §§ Before dispatching the transformer, all probes shall be checked with the same measuring instrument going along with that particular transformer and the temperature data should be recorded.



c) Inspection and pre-commissioning tests at Site: §§ §§

Check for any physical damage for the entire system. Check all probes for functional healthiness and record the temperature readings.

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3

Gas & Oil Actuated Relay (Buchholz Relay) 3.1. Description This is a gas and oil actuated relay for liquid immersed power transformers and reactors with conservator. The device is intended to detect: §§ Gas release from the unit to be protected §§ Oil surge from the tank to the conservator §§ Complete loss of oil in the conservator 3.2 Principle of Operation

Buchholz relay is completely filled with oil under normal operation of the transformer. In the event of an internal fault in the transformer, gas bubbles are produced in oil, which accumulate in the Buchholz relay. This leads to drop in oil level in the BR, thereby causing operation of the alarm switch contact.



In case the oil continues to drop due to excess gas accumulation, it triggers operation of the trip contact.

3.3 Data sheet Technical Parameters Parameter

Buchholz Relay 80 NB

Mounting arrangement

Ref Fig. 2.12

Liquid in tank

Transformer oil

Operating temperature

-20o to +110o C of oil

Contact system

Magnetic Reed Switch

Type of contact

Ref Fig. 2.11

Contact rating

- a.c.

240 V, 2 A

- d.c.

240 V, 2 A

Breaking capacity

400 VA a.c. or 250 W d.c.

Gas volume for alarm

200 to 300 cc

Surge velocity test

120 to 160 cm/s for trip contact

Vibration test

Vibration test at the frequency of 5 to 35 Hz with acceleration up to 6g in all directions.

3.4. Standard wiring diagram Any one of the following terminal configurations can be selected as per requirement. The contact position shown below is under normal operating condition of buchholz relay. 3.4.1 Wiring Diagram for Model with 2 NO Contacts Alarm

1 NO Contact

1 No.

Trip

1 NO Contact

1No.

Fig. 2.11

3.4.2 Wiring Diagram for Model with 3 NO Contacts Alarm

1 NO Contact

1 No.

Trip

1 NO Contact

2 Nos.

Fig. 2.11

POWER TRANSFORMER - STANDARDISATION MANUAL

3.4.3 Wiring Diagram for Model with 2 Change-over Contacts Alarm

1 Change-over Contact

1 No.

Trip

1 Change-over Contact

1 No.

Fig. 2.11

3.4.4 Wiring Diagram for Model with 2 NC Contacts Alarm

1 NC Contact

1 No.

Trip

1 NC Contact

1 No.

Fig. 2.11

3.5 Selection criteria §§

Quantity of oil inside the transformer to be protected

Normally 80 NB size BR is used for power transformers ≥10 MVA rating as per CBIP Publication No. 317.

3.6 Mounting details BILL OF MATERIAL 14

Plaster Plug

13

Plug & Socket Assembly

12

Cap for Pneumatic Testing Device

11

Pneumatic Test Device

10

Electric Testing Device

9

Cap for Electric Testing Device

8

Connector 1/8“ x 1/8“ BSP

7

Plug D83

6

1/4” BSP Cap for Petcock with chain

5

1/4” BSP MX1/4”BSP F Petcock

4

1/4” BSP Petcock

3

Aluminium Terminal Box Cover

2

Aluminium Cover

1

Aluminium Relay Body

Sr. No.

Description

Reference

Pipe Size A

B

C

D

E

F

1

80 NB

312

215

185

145

18

Fig. 2.12: Mounting details

3.7 Tests 3.7.1 Type tests a)

Tests as per IS: 3637

b)

Vibration Test at 5 to 35 Hz at 6g acceleration in all directions

c)

Degree of protection - IP:67

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3.7.2 Routine tests Test

Test Parameter

Testing Procedure

Pass Criteria

Alarm Test

200 to 300 CC

Gas collection by draining the oil to match reading on scale

As per testing parameters

Trip Test

120 to 160 cm/s

Create the surge to check velocity

As per testing parameters

High Voltage Test

2 kV

a) Applied between terminal to terminal for 1 min b) All terminal shorted with BR for 1 min

No breakdown

Leakage Test / Loss of Oil

Test of Housing with compressed air

To check housing for leakage with compressed air at 2.5 kg/cm2

No leakage from any point

Test of assembled Buchholz Relay with Transformer Oil

To check assembled Buchholz Relay for leakage with Transformer Oil at 2.5 kg/cm2 for 140 hrs

No leakage from any point

3.8 Installation and pre-commissioning checks a)

Transit damage.

b)

Dimensional check for installation suitability.

c)

Electric contact by operating lever/Push rod provided on the BR.

d)

Get all fasteners, gaskets and other tools before taking out BR for the fitment.

e)

Check pipe line alignment, gap between pipe line flanges to put BR in position.

f)

Hold BR in position with positive inclination of 3° to 7° (see Fig. 2.13 below) to the horizontal axis in the direction of arrow marked on the BR body, provide suitable gaskets and fit the BR with fasteners in the pipe line.

g)

Ensure tightness of all the contacts.

h)

Connect electrical contacts with battery and check the operation.

i)

Fill BR with oil and check tightness of bolted joint for any oil leakage.

Fig. 2.13: Mounting of Buchholz Relay

POWER TRANSFORMER - STANDARDISATION MANUAL

4

Pressure Relief Valve (PRV) 4.1 Description

The PRV is suitable for oil filled power transformer. It operates when Pressure in the tank rises above predetermined safe limit and performs the following functions. No.

Function

Description

1

Relieve Excess Pressure

The PRV instantaneously relieves the oil pressure built inside the transformer tank by lifting the diaphragm resting on the port of about 150 mm diameter and discharges the oil from tank, thus relieving pressure. To avoid oozing of oil, the diaphragm is spring loaded to close the port as soon as the pressure in the tank is relieved.

2

Visual Indication

The PRV gives visual indication of valve operation by raising a flag. Flag remains in operated condition till it is manually reset.

3

Switch Operation

As soon as the PRV is operated it operates an electrical switch (Micro/Limit switch). Switch contacts can be used to give audible alarm or isolate the transformer from circuit. Switch should remain in operated condition till it is manually reset.

4.2 Principle of Operation

A Spring Loaded Stainless Steel diaphragm is used to keep the port opening of about 150 mm diameter of PRV in closed condition. The diaphragm gets lifted from its position as soon as the oil pressure in the tank rises above predetermined operating pressure and releases the oil / vapour to relieve pressure in tank. The lifting of diaphragm operates electrical switch & flag. The Switch & Flag remain in operated condition till they are manually reset.

4.3 Data Sheet Parameters

Values

Liquid in Tank

Transformer Oil

Mounting

On Tank cover or side wall i.e. Horizontal or Vertical On 6 Studs of M12 Equally spaced on 235 PCD

Port Opening

Nominal 150 mm Diameter with spring loaded Diaphragm.

Operating Pressure

0.42, 0.49, 0.56, 0.7 kg/cm2 (any one value, shall be specified by the transformer manufacturer)

Operating Tolerance

± 0.07 kg/cm2

Operating Time

Instantaneous

Valve Resetting

Automatic

Visual Indication

By flag

Visual Indicator Resetting

Visual Indicator Resetting Manually

Operating Temperature

0 to 100 °C (of Liquid on Tank)

Duty

Outdoor / Indoor

Contact system

Micro switch

Type of Switch

2 NO + 2 NC

Rating of Switch

Micro Switch – 5A, 240V AC / 0.2 A , 240V DC

Switch Resetting

Manual

Mounting Gaskets

Nitrile Rubber Gasket of suitable size to fit on PRV Groove

Cable Entry

Hole with 3/4” Conduit threads for cable gland

Degree of Protection

IP 67

Hardware

Stainless Steel

Rain Protection Cover

Metallic Type

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4.3.1 Shroud Shroud with pipe connecting flange can be used to avoid spilling of discharge from PRV. Flange of shroud can be connected through 360 degrees orientation in horizontal plane. This arrangement can avoid injury to person and also avoids pollution.

Fig. 2.14: PRV with shroud

4.3.2 Weather proof plug & socket arrangement for connecting cable :

Fig. 2.15: PRV with shroud with weather proof plug and socket arrangement for connecting cable

4.4 Standard wiring diagram

Any one of the following terminal configurations can be selected as per requirement.



The contact position shown below is under normal operating condition of PRV.

Fig. 2.16: Wiring diagram for Model with 2 NO + 2 NC Contacts

POWER TRANSFORMER - STANDARDISATION MANUAL

4.5 Selection criteria §§

Operating Pressure

4.6 Tests 4.6.1 Routine tests TEST

DESCRIPTION

Operation of PRV

Operation of PRV at specified Pressure with compressed air

Power Frequency Test

Power frequency test at 2.5 kV, 50 Hz for one minute from switch terminals to other parts of PRV

Insulation Resistance

Test between Terminal to Body –Should not be less than 100 MΩ at 500V

Leakage Test

Leakage test at 75 % of operating pressure with air for 24 hours

4.6.2 Type test

PRV to be tested for IP:67.

4.7 Installation and pre-commissioning checks Check transit damage Dimensional check for installation suitability. Get all fasteners, gaskets and other tools before taking out PRV for the fitment. Take gasket with 6 holes, 14 diameter on 235 mm PCD Ensure tightness of all the contacts Connect electrical contacts with battery and check the operation 5

Magnetic Oil Level Gauge (MOG) 5.1 Description

A magnetic oil level gauge (MOG) is provided on the transformer conservator for indication of oil level in the transformer. A float is used as a device for indication of oil level inside the conservator on a calibrated dial gauge. The dial is marked as “EMPTY”, “¼”, “½ (or 35°C)”, “3/4” and “FULL”. Calibration of marks “EMPTY” and “FULL” (Fig. 2.17) is done after leaving 65 mm from the bottom and the top of the conservator to avoid striking of the float to the conservator oil.

Fig. 2.17

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5.2 Principle of Operation

Magnetic Coupling: The float touches the oil surface level and it moves up and down with change in the level of oil. Transfer of float movement to the pointer provided on the dial gauge by use of pair of permanent magnets (Fig. 2.18).

Fig. 2.18

5.3 Data sheet Technical Parameters Parameter

Liquid in tank Dial size Operating temperature

MOG (For Main / OLTC Conservator) Transformer oil 100mm/150mm/250mm -30o to +120oC of oil

Pressure

0 to 1kg/cm2

Contact system

Micro switch

Type of contact

Normally open

Contact rating

240 V, 5 A AC 240 V, 0.2 A DC

No of contacts

1No. (for LOLA)/ 2 Nos. (for LOLA, HOLA)

Contact Position

Normally Open at Filling Level

Colour of marking

Black markings on white background

Pointer

Black

Material

Float - Brass, Float arm - SS

POWER TRANSFORMER - STANDARDISATION MANUAL

5.3.1 Mounting:

MOG for conservator with aircell

Fig. 2.19

MOG for conservator without aircell

Fig. 2.20

Variable Parameters (to be provided by Transformer manufacturer) 1. Diameter of conservator (in mm) 2. Application : for main / OLTC conservator 3. Average ambient temperature.

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4.

Float Arm Length (FAL) FAL to be selected from table below Sr. No.

Conservator diameter Ø

F.A.L. for 30 degree inclined mounting

F.A.L. for vertical mounting

1

350

N/A

156

2

750

707

438

3

800

778

474

4

900

919

545

5

1000

1060

615

6

1200

1343

757

7

1300

1485

827

8

1400

1626

898

9

1600

1909

1040

5.3.2 Method of Cable Termination Weatherproof Plug & Socket arrangement for cable

Fig. 2.21

5.4 Standard wiring diagram

Any one of the following terminal configurations (Fig. 2.22 and Fig. 2.23) can be selected as per requirement. The contact position shown below is for normal operating condition of MOG.

Fig. 2.22: Wiring Diagram for Model with 2 NO Contacts

Fig. 2.23: Wiring Diagram for Model with 1 NO Contact

POWER TRANSFORMER - STANDARDISATION MANUAL

5.5 Selection criteria §§ Type of conservator (for Main or OLTC conservator) §§ Diameter of conservator §§ No. of contacts required §§ Dial size of MOG 5.6 Tests 5.6.1 Routine tests a) Leak test at 2 kg / sq cm for 2 min. at ambient temperature. b) Float position shall be calibrated to the diameter of conservator and the dial of MOG. c) Position of low oil level alarm to be checked. d) Power frequency test at 2.5 kV, 50 Hz for 1 minute from switch terminals to other parts of MOG. e) Insulation Resistance Test between Terminal and Body; it should not be less than 100MΩ at 500V. f) Micro switch at 5 amps, 240 V AC. 5.6.2 Type tests

Degree of Protection - IP67.

5.7 Installation and pre-commissioning checks a) Take 8 studs of M10 with nuts & washers. b) Take gasket with 8 holes, 12 mm dia on 225 mm PCD. c) Mount the MOG as shown in Mounting arrangement diagram (Fig. 2.19 and Fig. 2.20). d) Handle the MOG float & float-arm carefully being delicate items. e) Ensure tightness of all the contacts f) Connect electrical contacts with battery and check the operation 6

Oil / Water Flow Indicators (FI) 6.1. Function

The function of Flow indicator is: §§

To indicate the flow of oil / water in pipeline in required direction.

§§

To operate two switches, first, when the rate of flow drops to 80% & second, when the rate of flow further drops to 70%.

Fig. 2.24

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6.2 Principle of Operation

Magnetic Coupling



A metallic spring loaded vane is kept suspended in the pipe (Fig. 2.24). The vane deflects, when the flow of liquid strikes. The vane & return spring remain inside the liquid. A pointer is linked to vane with the help of a pair of permanent magnet. Thus, the pointer follows the deflection of vane. Pointer & vane mechanism are separated by a non magnetic metallic solid wall to avoid leakage of liquid in pipe. Two switches are provided which operate at 80% & 70% respectively when rate of flow starts dropping.

6.3 Data Sheet Parameter

Specification

Liquid in pipe

Oil or Water

Rate of full flow

Of liquid in pipe in LPM

Pipe size

Nominal Bore in mm

Direction of flow

Any one from the following - Left to Right - Right to Left - Vertically Up - Vertically Down

No of contacts

Two

Type of contacts

NC (Open at full flow)

Contact rating

5 A, 240 V AC & 0.25 A, 240 V DC

Two micro switches for operation at

80% & 70% of full flow

First and second contacts get closed when flow drops at 80% & 70% of full flow respectively. 6.4. Dial Parameters - 100 mm round - Back markings on white dial - Black Pointer Markings on dial - Indication markings: FULL FLOW, NO FLOW (Fig. 2.25) - Other markings - Pipe size, Value of Full Flow, Liquid in pipe & Direction indicating arrow.

Fig. 2.25

POWER TRANSFORMER - STANDARDISATION MANUAL

6.5 Standard wiring diagram Any one of the following terminal configurations can be selected as per requirement. The contact position shown below is under normal operating condition of flow indicator.

Fig. 2.26: Wiring Diagram for Model with 2 NC Contacts

6.6 Tests 6.6.1 Routine tests - Leakage test at 7 kg / cm2 - Flow: Full Flow test as specified by buyer. - Switch operation at 80% & 70% when rate of flow is dropping - Power frequency test between live terminals to body at 2 kV for 2 minutes 6.6.2 Type tests Degree of Protection - IP 67. 6.7 Mounting 6.7.1 “T” Mounting

When a flange matching with holes of FI & projecting from the pipeline, “T” Mounting is provided. The FI is installed on the T mounting. After mounting, the vane of FI is positioned in Centre of pipe.

Fig. 2.27

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6.7.2 Weatherproof Plug & Socket arrangement for cable

Fig. 2.28

6.8 Installation and pre-commissioning checks

7

a)

Take FI with suitable gasket, 4 bolts with nuts & washers of M12

b)

Install the FI so that dial is in erect position.

c)

Make electric connection with a cable gland

d)

Ensure tightness of all the contacts.

Air Cell or Flexi-separator 7.1 Description

The flexible separator is a sealed envelope made from nylon fabric coated with synthetic elastomer nitrile and hot vulcanized. The separator is installed inside the conservator and fitted to it through the flange connected to the plate of the manhole. 7.1.1 Schematic diagram of Air Cell

Fig. 2.29: Schematic Diagram of Aircell

POWER TRANSFORMER - STANDARDISATION MANUAL

7.1.2 Drawing of Air Cell

Fig. 2.30: Drawing of Air Cell

7.1.3 Selection of Air Cell Requirement can be specified by giving dimension of X, Y & G (calculated as per formula given below) Formula: Y = (3.142 x D)/2 + 40 mm, X = L - D + Y, G = X - Y - 200 Example: For Conservator of 700 dia x 2000 long Values will be X = 2240, Y = 1140, G = 1100 7.1.4 Connecting Flange

Fig. 2.31: Connecting Flange

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7.2 Standard sizes of Air Cell Standard Sizes of Air Cell Sr. No.

F S P - Size

1

500 - 500

2

Expansion Volume (litres)

Conservator Dia (mm)

Length (mm)

Volume (litres)

Length

Width

“G”

500

500

2710

530

3035

825

2010

500 - 600

500

600

1970

560

2352

982

1170

3

750 - 600

750

600

2850

810

3232

982

2050

4

750 - 700

750

700

2180

840

2620

1140

1280

5

1000 - 700

1000

700

2830

1090

3270

1140

1930

6

1000 - 800

1000

800

2260

1130

2757

1297

1260

7

1500 - 800

1500

800

3250

1630

3747

1297

2250

8

1500 - 900

1500

900

2660

1690

3214

1454

1560

9

2000 - 900

2000

900

3440

2190

3994

1454

2340

10

2000 - 1000

2000

1000

2880

2260

3491

1611

1680

11

2500 - 1000

2500

1000

3520

2760

4131

1611

2320

12

2500 - 1100

2500

1100

3000

2850

3668

1768

1700

13

3000 - 1100

3000

1100

3520

3350

4188

1768

2220

14

3000 - 1200

3000

1200

3050

3450

3775

1925

1650

15

4000 - 1200

4000

1200

3940

4450

4665

1925

2540

16

4000 - 1300

4000

1300

3450

4580

4232

2082

1950

17

5000 - 1300

5000

1300

4200

5580

4982

2082

2700

18

5000 - 1400

5000

1400

3710

5720

4549

2239

2110

19

6000 - 1400

6000

1400

4360

6720

5199

2239

2760

20

6000 - 1500

6000

1500

3900

6880

4796

2396

2200

7.3 Tests 7.3.1 Routine tests

Coated fabric - Mass surface - Tearing strength - Breaking strength - Elongation - Adhesion



Basic fabric - Breaking strength - Elongation



Aircell Size (mm)

Finished Product - Pressure testing by compressed air - Leakage testing

POWER TRANSFORMER - STANDARDISATION MANUAL

7.3.2 Type tests

Coated fabrics - Heat ageing - Compression test - Low temperature, flexibility - Sludge content - Acidity - Ozone resistance - Air permeability - Bursting strength

7.4 Installation care 7.4.1 Assembly of Air Cell inside conservator

Fig. 2.32: Aircell inside the conservator

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Refer Fig. 2.32 for general arrangement of Conservator and Aircell. Valve No. 1, 2, 3, 4 & 5 are fitted with direction marked next to the valve.



Remove the detachable end cover of the conservator as shown in Figure 2.32.

Fig. 2.33: Loops on the Aircell with the hooks inside the conservator



Assemble the Oil Level Indicator (MOG) as shown at location shown in Figure 2.32. Terminal box of the MOG should be vertically below the indicator dial. Carefully attach the float and float arm to MOG. Air cell, MOG, float and float arm are delicate, utmost care should be taken while assembly to avoid even slightest damage.



After the assembly of air cell and MOG are over, clean the conservator inside surface with clean cloth. Do not use cotton waste. Refit the detachable end cover.



Now the conservator is ready for installation in position and also for oil filling.



Before installing in position, check the air cell for any leakage as under.



It is to be noted that pipes, valves, pressure gauge shown in dotted line and N2 cylinder and vacuum pump are not supplied by manufacturer of these instruments. These should be made available at site, keeping in mind that oil filling of the conservator is to be done after installing the same in proper position.

POWER TRANSFORMER - STANDARDISATION MANUAL

7.4.3 Leakage Test of Air Cell

Inflate (fill) the air cell at a max, of 2 psig through valve 6 (use N2 gas) while leaving a vent hole i.e. valve 4 open.



Adjust the pressure after 6 hours (i.e. pressure to be retained at 1 psig). Check the temperature and maintain the air cell at that temperature for 24 hours. Watch the possible loss of pressure during that period. If there is no loss of pressure during 24 hours, this means the setting of air cell inside the conservator and also the air cell is considered leak tight. This also ensures that all gaskets joints are leak tight. Assemble the conservator at proper position.

7.5 Oil filling under Vacuum

Use transformer oil for filling. This oil should be same as used for transformer filling.



Fill oil into the conservator upto Filling Level on MOG via ‘B’ relay pipe, valve 5 by pumping the oil from bottom of the transformers.



Keep air cell open to atmosphere by opening valve 6 & 7 to atmosphere. Open also valve No.2 so that pressure inside the conservator and air cell will be same. Connect valve 7 to vacuum pump. (Valves 6 & 2 open) Valves 3 & 1 closed.



Pull the vacuum up to 760 mm Hg simultaneously to air ell and conservator. When 760 mm vacuum is achieved close valve 2



Push oil through valve No.5 till the MOG shows Full oil level.



Close valve 6, 2, & 3 and connect N2 cylinder to valve 7.



Maintain conservator under vacuum and admit N2 into air cell at a max, of 1 PSIG through valve 6. Then the air cell inflate by itself and takes all the free space due to the fact that the conservator was not completely full. Fill the conservator till the moment the oil is going to rise to the top of conservator. Continue to admit nitrogen into air cell at one psig and simultaneously drain oil from valve 3.



Drain the oil up to filling level. Immediately close Valve 3 and check that all the valves and openings on conservator except valve 5 are closed.



Connect air cell to silica gel breather.



Caution When the assembly is ready to work, it is important not to open vent holes / valves on upper part. Plain oil gauges are usually provided on the opposite end of MOG on conservator. These gauges might show full irrespective of oil level in conservator. Hence refer MOG reading for checking the oil level in the conservator.

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8

Conservator Protection Relay (CPR) / Aircell Puncture Detection Relay 8.1 Description

Conservator protection relay (CPR), also called Air cell puncture detection relay, is a single-float type relay to provide a signal in case of puncturing of air cell. 8.1.1 Schematic diagram of Conservator Protection Relay

Fig. 2.34: Schematic Diagram of CPR

8.1.2 Drawing of Conservator Protection Relay

Fig. 2.35: Drawing of Conservator Protection Relay

POWER TRANSFORMER - STANDARDISATION MANUAL

8.1.3 Standard wiring diagrams Choose any one model out of the following options. Contact position is shown in healthy condition. 8.1.3.1 Model with 1 NO contact

8.1.3.2 Model with 1 change over contact

Fig. 2.36: Standard wiring diagram

8.1.4 Mounting details

Fig. 2.37: Mounting details of CPR

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8.2 Data sheet

Parameter

Specification

Model

Refer Fig. 2.36 Standard wiring diagrams

Mounting arrangement

Refer Fig. 2.37

Liquid in tank

Transformer oil

Operating temperature

-20 oC to +110 oC of oil

Environment

Indoor or Outdoor

Contact system

Magnetic Reed Switch

Type of contact

As per wiring diagram (Figure 2.36)

Contact rating

- a.c.

240 V, 2A for point 1.3.1 240V, 1A for point 1.3.2



- d.c.

240 V, 2 A for point 1.3.1 240 V, 1 A for point 1.3.2

Breaking capacity

400 VA a.c. or 250 W d.c.

Gas volume for Alarm

400 +/- 50 cc

Ingress protection

IP 67

Vibration test

Vibration test at the frequency of 5 to 35 Hz with acceleration up to 6g in all directions

8.3 Tests 8.3.1 Routine tests Test

Testing Parameter

Testing Procedure

Observations

Trip Test

400 +/- 50 cc

Gas collection by draining the oil to match reading on scale

As per testing parameters

High Voltage Test

2 kV

a) Applied between terminal to terminal for 1 minute b) All terminals shorted with body for 1 minute

No breakdown

Leakage Test / Loss of Oil

Test of Housing with compressed air

To check housing for leakage with compressed air at 2.5 kg/cm2

No leakage from any point

Test of assembled CPR with transformer oil

To check assembled CPR for leakage with transformer oil at 2.5 kg/cm2

No leakage from any point

8.3.2 Type tests To be carried out at third party laboratory at an interval of 5 years. i)

Vibration Test.

ii) Ingress Protection Test - IP 67 8.4 Pre-commissioning tests Following checks/test to be carried out on delivery at site. i.

Transit damage.

ii.

Dimensional check for installation suitability.

iii. Terminal connections as per order specification. iv. Electric contact by operating provided device. (Lever / Push rod)

POWER TRANSFORMER - STANDARDISATION MANUAL

8.5 Installation care i. Get all fasteners, gaskets and other tools before taking out CPR for the fitment. ii. Check mounting flange dimensions to put CPR in position. iii. Mount CPR in such a way that the Glass Window is visible from outer side and fix it with the fasteners. iv. Connect electrical contacts with battery and check the operation. 9

Removable Radiators for Oil-immersed Transformers 9.1 Description



Radiators, i.e. the thermal exchangers, are used for cooling of transformer oil with natural ambient air circulation. Such radiators are made of several elements with cooling channels connected in parallel. This specification defines the overall dimensions and ensures the mechanical interchangeability achieving the same thermal performances.

9.2 Reference Standard BS EN 50216-1:2002 & IEEMA 9 9.3 Data sheet Material and other general construction shall be as follows: No.

Technical Parameter

Specification

1.

Section Width / Channels / Flutes

520mm / 21 to 28.

2.

Centre distance between top and bottom header pipes (CC)

- 2000 mm to 4500 mm in step of 100 mm. - Tolerance : ±3 mm - Pipe size : Up to 3000 mm : 80 NB Above 3000 mm : 100 NB

3.

Number of Sections

4 to 40

4.

Pitch

Minimum 45 mm with a tolerance of ±1 mm.

5.

Flanges

STEP Flange of 18 mm thickness.

6.

Bracing Straps/Rods:

- Size : 8/10 mm - Material : Bright round mild steel - No of pairs : 5 pairs for CC 2800 mm to 3500 mm 6 pairs for CC above 3500 mm

7.

Lifting lug

- Up to 3000 mm :50x65x12, φ 25 mm - Above 3000 mm :100x85x12; φ 50 mm - 60x40x8 mm, φ14 mm

Tying lug 8.

Materials

a) Radiator Sections: CRCA sheet conforming to Gr D of IS 513 - Up to 3000 mm : 1.0 mm (Tol. ± 0.05 mm) - Above 3000 mm : 1.2 mm (Tol. ± 0.05 mm) b) Header Pipe (Top & Bottom): 90 mm OD pipes of ERW/ CRCA tubes of 2.5 mm thickness (as per IS 1239) c) End Cap : 60x40x8 mm; φ 14 mm d) Air Release and Drain plug: 1/2 inch BSP e) Sealing for plug: Teflon washer / Nitrile ‘O’ ring f) Bracing Bar: 8/10 mm dia weldable structural steel round bars conforming to Fe410WA of IS 2062.

9.

Width-wise top & bottom edge sealing of fin

TIG Welding / GTAW

10.

Header pipe to fin throat sealing

TIG Welding / GMAW

11.

Assembly weld tacking

TIG Welding / GMAW

12.

Leak repairs

Oxy Acetylene gas welding

13.

Surface preparation for painting

SA 2 ½

14.

Painting

a) Internal surface: Flush coated with phenolic-based hot oil- resistant varnish b) External surface: Epoxy Zinc primer – DFT 60 microns PU Finish paint – DFT 40 microns Total (minimum) - DFT 100 microns Note: Zinc chromate is not recommended as it is carcinogenic.

Abbreviations: MIG – Metal Inert Gas, GMAW – Gas Metal Arc Welding, TIG – Tungsten Inert Gas, GTAW – Gas tungsten Arc Welding, MMAW – Manual Metal Arc Welding.

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9.4 Tests Description

Test Type

Standard Specification

Type Test

a) Vacuum Test - Vacuum - Deflection

10 Torr Deflection not to exceed +0.5 mm.

b) Pressure Test

At 200 kPa for 3 hours at 60 °C (± 5 °C) oil temperature

a) Dimensional

-

b) Leakage

At air pressure of 2kg/cm2 for a minimum period of 30 minutes

Routine Test

10 Automatic Voltage Regulating Relay (AVR) 10.1 Description

AVR is used for regulating the secondary voltage of power transformer with on-load tap changer. The required dead-band settings are set by setting the nominal value and L & R levels independently. The Time Delay setting on the front panel eliminates the relay operations for momentary fluctuations of the regulated voltage, thus reducing the number of operations of the tap changer.



When the regulated voltage falls below the specified Under Voltage limit, the control relays are automatically blocked i.e. there is no voltage correction, and a pair of relay contacts is made available for alarm.

10.2 Principle of Operation

The dead-band (bandwidth) can be set by setting the nominal value (NVA) to the required value and then setting the L & R limits around the NVA.



The desired time delay can be set on the front panel and the control action will take place only if the voltage continues to remain outside the dead-band after the time delay has elapsed. For voltage corrections requiring more than one tap change, time delay is initiated again before further tap change. The relay is reset automatically after the voltage is brought within the selected dead band. The time delay is effectively reduced to provide a voltage time integral response of the regulator for repeated short duration voltage fluctuations on the same side of the dead-band.



Operation of the Raise Control Relay is automatically inhibited when the voltage falls below the specified under voltage limit or it fails. One pair of normally open relay contacts are provided to effect the tap change during Raise and Lower operation and to trigger an alarm in case of Under Voltage / P.T. fail conditions.

10.3 Data Sheet 10.3.1 Option 1: Standard AVR without communication ports S. No.

Feature

Standard

1

Aux. Supply

90-260V AC/DC

2

PT Supply

110V AC, 2.5VA

3

Nominal Voltage adjustment

+/-10% of PT supply (continuous)

4

Sensitivity (Dead Band)

1 V to 9.9 V (continuous)

5

Time delay setting

Voltage independent, 10 to 120s in steps of 1s

6

Time delay resetting

Instantaneous resetting with voltage deviation in opposite direction

7

Under voltage blocking

Internal blocking at 80% and restoration at 85% of nominal voltage

POWER TRANSFORMER - STANDARDISATION MANUAL

8

Control relays

One pair of NO potential free contact 5A at 230V AC

9

Control operation

Single pulse operation with 2s (approx.) on-time.

10

Terminal block numbers

Terminal block nos. as shown in Cl. No. 10.4

11

Type of terminal block numbers

Combicon type terminal blocks suitable for 2.5 Sqmm cable (external).

12

Cut-out dimensions

185 (W) x 90(H) mm

13

Optional Features 13.1

Line drop compensation (optional)

With CT current input of 1A; %R & %X setting to be set in ‘%’

13.2

AVR control fail relay

One pair of NO potential free contact 5A at 230V AC

13.3

Under voltage relay

One pair of NO potential free contact 5A at 230V AC

13.4

Aux. supply fail relay

One pair of NO potential free contact 5A at 230V AC

13.5

PT supply fail relay

To be incorporated in control scheme

13.6

AVR fail **

One pair of NO potential free contact 5A at 230V AC

** One LED shall be provided for “AVR HEALTHY” display

10.3.2 Option 2: AVR with communication ports

In addition to the features covered in Option-1, following additional features are to be provided: a)

Communication Interface for SAS (Substation Automation System) - through both RJ45 (Ethernet) & FO Cable with IEC 61850 Protocol.

b)

Tap Position No. Display with inputs of both 4-20 mA & Resistance of 1 kilo ohm per step

c)

1 no. 4-20 mA output for TPI.

d)

OLTC Operation Counter for each tap at the remote.

e)

Real Time Voltage Display (kV) as per the PT input at the remote.

10.4 Termination details S. No.

Function

Connection Pins

1.

Auxiliary Input

1-2

2.

PT Input

3-4

3.

CT Input

5-6

4.

Auxiliary supply Fail Relay (AFR) (NC)

7-8

5.

Lower Relay (NO)

9-10

6.

Raise Relay (NO)

11-12

7.

Under Voltage (UV) / PT Fail (PTF)

13-14

8.

Control Fail Relay (CFR) (NO)

15-16

9.

1 Kilo Ohms per step input for TPI

17-18

10.

4-20 mA Input for TPI

19-20

11.

4-20 mA Output for TPI

19-20

10.5 Tests 10.5.1 Routine tests a)

Contactor (Raise / Lower) Operation

b)

Time Delay Calibration

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c)

Functional Check of AVR fail / Aux. supply fail relays

d)

LDC Module Calibration

e)

Burn-in test

f)

2kV Test

10.5.2 Type tests a)

Dry Heat test at 50°C for 3 hours.

b)

Cold test at -20°C for 3 hours.

c)

Vibration test at 10-55 Hz, displacement +/- 0.75 mm (p-p), duration 15 min./axis (X, Y, Z).

d)

Bump test (packed condition): Acceleration 40g, Pulse duration 6ms, Normal axis, 1000 bumps.

e)

EMI / EMC Test specifications : BS EN61326 : 1998 Set up as per i. EMI / EMC Test specifications : BS EN61326 : 1998 ii. EMI / EMC Test specifications : BS EN61326 : 1998 iii. EFT : As per BS EN61000-4-4, 1995 iv. Radiated Susceptibility : As per BS EN61000-4-3, 1995

10.6 Installation and pre-commissioning checks a)

Check the proper electrical earthing.

b)

Use shielded cable for input signals.

c)

Ensure that input signal and power cables are isolated.

d)

Make sure the proper supply voltage is applied.

e)

Switch off the power supply while wiring.

f)

Ensure tightness of all the contacts.

11 Transformer Fire Protection System 11.1 Nitrogen Injection Fire Prevention System (NIFPS) 11.1.1 Description



This standard lays down the specification for Nitrogen Injection Explosion prevention and Fire Extinguishing system for oil cooled transformer/ reactor. Dedicated Nitrogen injection system is used to : §§

Prevent transformer tank explosion and possible fire, in the event of internal fault and as such it acts as fire preventer.

§§

Also act as firefighting system

System comprises Cubicle (installed near the transformer), Control Box ( installed in control room), Conservator isolation valve (installed in conservator pipe line), Fire detectors (on transformer top cover), Piping for oil and nitrogen, Copper Cables. 11.2 Reference Standards a)

Central Electricity Authority, The Gazette of India, Extraordinary 2010

b)

Technical standards for constructions of sub-stations and switchyards

c)

Technical standards for construction of Thermal Generating Stations

d)

Safety provisions for electrical installations and apparatus of voltage exceeding 650 volts

e)

CBIP Manual on Transformers - Publication no. 317

POWER TRANSFORMER - STANDARDISATION MANUAL

11.1.3 Principle of Operation

Depressurization process commences through oil drain and simultaneously nitrogen is injected at a predetermined flow rate to create stirring action and to bring down temperature of top oil below ignition point, evacuates gases formed thereby preventing explosion of tank and in case of fire, it extinguishes fire within minimum 30 seconds. During fault condition, system operates and conservator isolation valve blocks oil flow to isolate conservator tank oil. Also in case of fire, it prevents escalation of fire.



The system comes in to operation automatically / remotely / manually under following conditions. Auto Mode a)

b)

For Prevention of Fire, signals in series : §§

Differential Relay Operation,

§§

Buchholz Relay paralleled with Pressure Relief Valve or RPRR (Rapid Pressure Release Relay)

§§

Tripping of all connected breakers (HV & LV side) is a pre-requisite for initiation of system activation.

For Extinguishing Fire, signals in series : §§

Fire Detector,

§§

Buchholz Relay paralleled with Pressure Relief Valve or RPRR.

§§

Tripping of all connected breakers (HV & LV/IV side) is a pre-requisite for initiation of system activation.

Manual Mode (Remote) §§

Tripping of all connected breakers (HV & LV/IV side) is a pre-requisite for initiation of system activation.

Manual Mode (Mechanical) §§

Tripping of all connected breakers (HV & LV/IV side) is a pre-requisite for initiation of system activation.

The system shall be designed to be operated manually (oil draining and N2 injection) in case of failure of power supply to the system.

11.1.4 Sequence of Operation After receipt of operating signals, sequence of operation will be as shown in figure 2.38. 11.1.5 System features §§

System shall have interlock to ensure operation of system only after transformer electrical isolation to avoid nitrogen injection in energized transformer.

§§

Pressure monitoring switch for back-up protection for nitrogen release as redundancy to first signal of oil draining commencement for Nitrogen release shall be provided.

§§

Nitrogen release scheme shall be designed in such a way that the nitrogen gas shall not enter the energised transformer/reactor tank even in case of passing/leakage of valve.

§§

System shall have provision of testing during commissioning, during annual maintenance and on live transformers to ensure healthiness at all times.

11.1.6 Selection Criteria Transformer Rating

Capacity of Nitrogen Cylinder

Above 10 MVA & below 100 MVA

6/10 m gas at pressure of 150 kg/cm

100 MVA and below 250 MVA

10 m3 gas at pressure of 150 kg/cm2

Oil drain pipe size 125mm

250 MVA and above

20 m3 gas at pressure of 150 kg/cm2

Oil drain pipe size 125mm

3

Depressurization Scheme 2

Oil drain pipe size 80mm

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Fig. 2.38: Flowchart showing sequence of operation

11.1.6 Provisions on Transformer tank for Fitting N2 System Sr. no.

Transformer rating

Oil Drain Gate Valve

N2 Injection Valve

Quartz Fire detector on top cover

Conservator isolation valve arrangement between buchholz and conservator.

1

Above 10 MVA and below 100 MVA

Size 80 mm : 1No.

Size 25 mm: 4 to 6 Nos, Maximum

8 to 12 nos.

Dummy pipe 80/50 mm

2

100 MVA and below 250 MVA

Size 125 mm : 1No.

Size 25 mm: 6Nos, Maximum

12 to 16 nos.

Dummy pipe 80 mm

3

250 MVA and above

Size 125 mm : 1No.

Size 25 mm: 6 to 8Nos, Maximum

16 to 20 nos.

Dummy pipe 80 mm

Mounting support/ frame on any tank side wall for signal box shall be provided.

POWER TRANSFORMER - STANDARDISATION MANUAL

11.1.7 Data Sheet Sr. No.

Description

Specifications

1.

Type and Model

Nitrogen Injection Explosion Prevention and Extinguishing System for transformer rating a) Above 10 MVA & below 100 MVA b) 100 MVA and below 250 MVA c) 250 MVA and above

2

Details of system equipments

Cubicle, Control Box, Conservator Isolation Valve, Signal Box and Fire Detectors.

3

Cubicle, split door  

3.1

Dimensions (LXBXH) mm

3.2

Weight

a) & b) 500 kg (Approx.) c) 600 kg (Approx.)

3.3

Capacity and quantity of Nitrogen cylinder

a) & b) Above 10 MVA & below 250 MVA : Minimum 1 no. 10 m3 gas at pressure of 150 kg/cm2 c) 250 MVA and above : Minimum 2 no. 10 m3 gas at pressure of 150 kg/cm2

3.4

Pressure of Nitrogen filing

Maximum 150 kg/cm2

3.5

Minimum distance of FE cubicle from the transformer

 5 M or beside fire / safety wall

3.6

Method of mounting

 Floor / Plinth

3.7

Items provided in the cubicle 

3.7.1

Contact manometer

For showing nitrogen cylinder pressure. Falling pressure, Electrical contact, dual indicator for actual pressure as well as level for low pressure signal.

3.7.2

Pressure Regulator With safety relief valve to increased temperature variation compensation.

Inlet pressure : 150 kg/cm2 (+/- 10%) Outlet pressure range : 8 to 12 kg/cm2

3.7.3

Pressure gauge

For showing nitrogen injection pressure.

3.7.4

Oil Release Unit and suitable to operate without power

Electro- mechanical type, operating on substation DC supply as well with provision for operation using manual lever in case of DC supplier loss. It shall have mechanical locking arrangement to ease in maintenance and avoid unnecessary operation during maintenance test.

3.7.5

Gas release unit and suitable to operate without power

Electro- mechanical type, operating on substation DC supply as well with provision for operation using manual lever in case of DC supplier loss. It shall have mechanical locking arrangement to ease in maintenance and avoid unnecessary operation during maintenance test.

3.7.6

Oil drain assembly

Electro- mechanical type, operating on substation DC supply as well with provision for operation using manual lever in case of DC supplier loss.

a) For above 10 MVA & below 100 MVA 1200 x 500 x 1900/1700 b) For 100 MVA and below 250 MVA 1200 x 500 x 1900 c) For 250 MVA and above 1600 x 600 x 1900

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Sr. No.

Description

Specifications

3.7.7

Pressure monitoring switch as backup in addition to signal from limit switch to initiate nitrogen release simultaneously with oil drain commencement.

Provisions of Limit switch with Pressure Switch (Back up)

3.7.8

Limit switches with No of contacts & spare contacts (NO&NC)

1. Oil drain Valve closed. (G02), 2 NO 2. Oil drain Valve open.(G03), 2 NO 3. Gas valve closed.(G04), 1NO+ 1NC 4. Gas injection started.(G04), 1NO+ 1NC 5. Oil drain unit locked mechanically. (G05) 2NO/1NC+1NO 6. N2 release unit locked mechanically.(G06) 2NO/1NC+1NO

3.8

Oil drain Valve (above cubicle) for system isolation from transformer  

3.8.1

Material and Type

Mild steel, Butterfly valve

3.8.2

Size

a) Above 10 MVA & below 100 MVA : 80 mm b) 100 MVA and below 250 MVA : 125 mm c) 250 MVA and above : 125 mm

3.9

Nitrogen Injection Valve (above Cubicle) for system isolation from transformer

3.9.1

Material and Type

Gun metal, Lockable, Stem rising

3.9.2

Size

 25 NB

3.10

Oil drain pipe size

a) Above 10 MVA & below 100 MVA : 80 mm b) 100 MVA and below 250 MVA : 125 mm c) 250 MVA and above : 125 mm 

3.10.1

Length and Number of openings in the transformer tank

As per site location, Transformer to cubicle & cubicle to oil pit, 1 no.

3.10.2

Material

MS, ERW, Heavy duty for TRS to cubicle & GI, Medium for cubicle to oil pit.

3.11

Degree of protection

IP 55

4

Control Box 

4.1

Dimensions (LXBXH) mm

500 x 270 x 700

4.2

Weight

45 kg maximum

4.3

Type & Thickness of sheet steel

CRCA, 16/14 SWG

4.4

Details of components provided in the control box

MCB, Relays, Hooters, Contactors, Indicating lamps, Operating switches.

4.5

Control voltage

 110 / 220 VDC / Substation voltage. AC-DC / DC-DC converter, timer shall not be used for reliable operation.

4.6

Method of mounting

Wall / Frame

4.7

Whether audio and visual alarms provided?

Yes with different volume (dB) levels

4.8

Degree of protection

IP 42

5

Conservator Isolation Valve  

5.1

Type

Operating mechanically on Transformer oil flow rate with visual position indicator.

5.2

Location

Horizontally in the conservator pipe line between Conservator and Buchholz relay.

POWER TRANSFORMER - STANDARDISATION MANUAL

Sr. No.

Description

Specifications

5.3

Whether suitable for pipe of size 80mm dia

 As per transformer conservator pipe size i.e. 80 mm or 50 mm.

5.4

No of contacts & spare contacts (NO & NC)

Normally Open contact shall be provided.

5.5

Padlocking provision for service, filtration / refilling / filling

Required.

5.6

Visual position indicator similar to Buchholz relay for inspection

For physical close indication.

5.7

Transformer Conservator Isolation valve setting for normal operation (valve should not close) to ensure no obstacle for transformer breathing.

40 ltr / minute for 50 mm conservator pipe.

5.8

Transformer Conservator Isolation valve setting for operation during abnormal flow of oil due to rupture / explosion of tank or bushing / oil drain during system operation.

60 L / minute (minimum) for 80 mm conservator pipe.

6

Fire Detectors 

6.1

Type

Quartz bulb, Heat sensing.

6.2

Quantity required

Depending upon Transformer top cover area.

6.3

Method of fixing

Bolting on Fire Detector bracket on Transformer top cover using fire survival, copper cables (capable to withstand 750 °C.)

6.4

Temperature for heat sensing

 141 °C

6.5

Number of contacts

 2 NO

6.6

Necessity and condition of refilling

 After operation.

7

Power Supply

7.1

For Control Box

For operation :  110 / 220 VDC / substation DC voltage For DC fail alarm : 230 VAC

7.2

For Cubicle

For illumination and heating : 230 VAC

8

Extinction period  

8.1

On commencement of Nitrogen injection

 Maximum 30 Seconds

8.2

On system activation

 Maximum 3 minutes

9

Other technical details

On line supervision of operating signals, DC supply monitoring, Test facility (excluding CIV, FD) on live transformer, Anti condensation heater for Cubicle, Manual operation in DC supply fail, Separate oil drain and Nitrogen release mechanism.

11.1.9 Tests Functional test of following equipment is to be carried out during inspection and / or prior to dispatch: a)

Cubicle, showing oil drain and nitrogen injection.

b)

Conservator isolation valve.

c)

Control box.

d)

Fire Extinguishing Performance test.

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11.1.10 Typical site layout of Nitrogen Injection Fire Prevention System

Fig. 2.39

POWER TRANSFORMER - STANDARDISATION MANUAL

11.1.11 Ordering Information Project / Enduser details : Transformer details and Quantity : Manufacturer :

Serial number. :

MVA Rating :

Voltage ratio :

Oil Qty in tank : Oil Qty in Conservator :

Litres Litres

Power Supply (Pl tick √ ): Substation/ Control room D.C. Supply : 220V 110V A.C. Supply available : Control room Marshaling box Conservator pipe diameter :

48V 24V Other : Single phase, 240V, 50 Hz

mm Conservator pipe angle :

degree

Spare contacts in relay panel : Differential relay trip 1 number NO potential free

RPRR Trip 1 number NO potential Free

Buchholz Trip 1 number NO potential Free

Restricted Earth-fault Relay 1 number NO potential Free

OLTC oil surge relay trip 1 number NO potential free

Master relay Trip 1 number NO Potential free

PRV Trip 1 number NO potential Free

HV & LV circuit breaker trip, 1 number each NC potential free

NO : Normally Open, NC : Normally Close, RPRR : Rapid Pressure Rise Relay Main Dimensions of tank : L= mm B= mm H= mm A= mm

Bevelled cover

Yes

No

Built-in On load Tap Changer : Yes No Oil Filled Cable Box : Yes No If Yes : Provide general arrangement drawings Cooling details : If OF type Number of pumps : KW/HP : Installation :

New

Head : Back Flow when Pump Switch off :

LPM

Post

Distance from Transformer to control room through cable trench : Distance from Control room to Relay Panel through cable trench : Additional information :

Flow :

mtrs mtrs

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11.1.12 Erection Flow Chart

POWER TRANSFORMER - STANDARDISATION MANUAL

11.1.13 Erection Check List PROJECT : CUBICLE NO :

SIGNAL BOX NO. :

CONTROL BOX NO:

FIRE DETECTOR NO.

CONSERVATOR ISOLATION VALVE NO. :

 

PARTICULARS

PARTICULARS

1.0 Erection

Oil drain pipe slope 2 to 3 degree Towards cubicle

1.1 Civil work

Tightness of flange and bolts

CUBICLE plinth as per approved drawing.

External cleaning Painting red oxide and P.O. red

1.2 Oil pit / Tank

2.2 Pipe connection from cubicle to Oil pit

Sealing of top cover.

Weld joint

Termination arrangement of pipe to CUBICLE

Aluminium paint at weld joints

Capacity suitable for transformer

Fitment of drain pipe to CUBICLE collar Pipe slope 5 to 10 deg .towards oil pit

1.3 Cubicle

2.3 Conservator Isolation Valve

Check oil drain isolation valve above

Mounting as per position marked on

Closed

CIV as per Drg. No.

Check N2 isolation valve above CUBICLE

Tightness of flanges and bolts

Closed

Pump test with one pump

Door opening as per approved

Pump test with two pumps

Alignment

2.4 Fire Detector

Tightness of foundation bolts 1.4 Control Box (CB)

Mounting of fire detectors Mounting of fire detectors rain guards.

Wall mounting/Frame mounting, alignment Mounting at eye level

2.5 Earthing Signal box, CUBICLE, Control box & FD

1.5 Signal box (SB)

2.6 Cable Laying

Mounting at working height

Control box to signal box FRLS 12 core

Fitment

Control box to relay panel FRLS 12 core

1.6 Fire detector (FD)

Control box to CUBICLE FRLS 12 core

FD mounting as per drawing 1.7 Conservator Isolation Valve

Control box to DC-DC convertor 4 core CIV to signal box FRLS 4 core

Visual crack/damage

Control box to DC source FRLS 4 core

Space availability

Control box to AC source FRLS 4 core

Valve availability for isolation

CUBICLE to AC source FRLS 4 core FD to signal box FS 4 core

2.0 Installation 2.1 Pipe connection from Transformer to Cubicle

2.7 Cable Termination

Weld joint & weld joint fitup

Continuity of cable

Internal cleaning, varnishing & coating

Crimping quality of lugs

No leakage at 3.5 kg/cm for 1 hour

No excess length of cables

Alignment

Dressing and glanding

Pipe support at minimum 5 mtrs interval

Termination as per

Pipe support alignment

Interconnection Drg. No.

2

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11.1.14 Commissioning Check / Site Test Procedure

SR. N0.

DETAILS OF CHECKS/TESTS AND DESIRED RESULTS

1.0 1.1 1.2

READINESS FOR TESTS Transformer is out of service and de-energized. Test equipments available for simulation of Differential relay, RPRR, Pressure Relief Valve, Buchholz, Transformer isolation. All cables are properly connected as per interconnection drawing No.___________________ operation scheme diagram No._______________________ and terminal screws are tightened. Close the isolation valve on oil drain pipe connected above Cubicle. SWITCH ON main power supply 220V DC/110V DC and 230V to control box. SWITCH ON main power supply 230V AC to cubicle

1.3 1.4 1.5 1.6

2.0 2.1 2.2

3.0 3.1 3.2

4.0 4.1 4.2 4.3 4.4 4.5 4.6

4.7 4.8

5.0 5.1 5.2 5.3 5.4 5.5

CONSERVATOR ISOLATION VALVE(CIV) Unlock the lever, functional test of Limit Switch by moving lever clock-wise. Alarm ‘CIV closed’ must be activated on control box. Re-establish original operating conditions by resetting lever.

FIRE DETECTORS Un- screw the heat sensor, alarm ‘Fire detector trip’ must be activated on control box. Test all fire detectors individually. Re-establish original operating conditions.

CONTROL BOX Functional test “Lamp Test” Functional test “Differential relay Trip” (COMMAND TO BE GIVEN BY OPERATING DIFFERENTIAL RELAY FROM RELAY PANEL.). Signal shall appear on control box. Functional test “PRV/RPRR Trip (COMMAND TO BE GIVEN BY OPERATING PRV/RPRR RELAY FROM RELAY PANEL.). Signal shall appear on control box. Functional test “BUCHHOLZ TRIP (COMMAND TO BE GIVEN BY OPERATING BUCHHOLZ RELAY FROM RELAY PANEL.) Signal shall appear on control box. Functional test “TRANSFORMER TRIP (COMMAND TO BE GIVEN BY OPERATING HVCB&LVCB/ MASTER TRIP RELAY FROM RELAY PANEL).Signal shall appear on control box. Confirm by operating Transformer protection used in para 4.2, 4.3, 4.4 not interconnected with any other protection Viz. REF, WTI, OTI etc. expect Transformer Trip protection. Lamp indication for “Oil Drain Valve Closed” available. Lamp indication for “Gas Inlet Valve Closed” available. Functional test for “Visual/Audio alarm”. Functional test for “DC SUPPLY FAIL” visual/audio alarm by isolating DC supply to control box.

CUBICLE Insert locking pin to lock oil drain mechanically. Alarm for “Out of service” must be activated. Insert locking pin to lock Nitrogen injection mechanically Alarm for “Out of service” must be activated. Nitrogen Cylinder pressure greater than 135Kg/cm2. Adjustment Nitrogen injection pressure as per manufacturer standard setting. Tightness test of nitrogen injection valves, hoses, main gas valve, 2 and 3 way ball valves.

PLEASE √ AFTER TEST

POWER TRANSFORMER - STANDARDISATION MANUAL

SR. N0.

DETAILS OF CHECKS/TESTS AND DESIRED RESULTS

5.6 5.7

Check sealing of Gas Flow Control Unit is not disturbed. Perform ‘Differential relay trip’, ‘Buchholz/PRV/RPRR trip, and ‘Transformer trip, By OPERATING THE DIFFERENTIAL, Buchholz/PRV/RPRR, HVCB & LVCB/MASTER TRIP RELAY FROM RELAY PANEL (AUTO PREVENTION MODE). Lifting magnet Y01 must be activated. Remove the above connections. Lifting magnet Y01 must be de-energized. Perform ‘Fire Detector trip’, ‘Buchholz/PRV/RPRR trip, and ‘Transformer trip, By OPERATING Buchholz/PRV/RPRR, HVCB & LVCB/MASTER TRIP RELAY FROM RELAY PANEL (AUTO PREVENTION MODE).Lifting magnet Y01 must be activated. Press limit switch G03. Lifting magnet Y02 must be energized. Release limit switch G03. Lifting magnet Y02 must be de-energized. Turn 3 way ball valve in horizontal position (Inspection position. Lifting magnet Y02 must be energized. Remove wire connections mentioned in 5.8. Lifting magnet Y01 must be deenergized. Turn 3 way ball valve in “In service” position (vertical). Perform ‘Transformer trip’ (BY OPERATING THE HVCB AND LVCB/MASTER TRIP RELAY FROM RELAY PANEL and operate S02 for ‘ON’ position, Y01 must energize. Keep S02 in ‘OFF’ position (REMOTE ELECTRICAL MODE). Push lever A for operation of Y01 and push lever B for operation of Y02 (LOCAL MECHANICAL, MANUAL MODE). Unscrew the end of the flexible hose clamps of the gas supply fastened to throttle valve and withdraw the hose. Activate the extinction release device by withdrawing locking pin 2 and lifting magnet Y02 manually – gas will blow out of hose. Alarm for ‘Extinction in progress’ must be activated. Re- set extinction release device and insert locking pin 2 in test position. Fasten the end of flexible hose of gas supply to Gas Flow Control unit and check tightness again. Adjust contact on manometer to the actual pressure line. Alarm for “Cylinder pressure low” must be activated. Reset electrical contact in manometer at______kg/cm2 (as per manufacturer standard setting). Visual check of tightness of quick oil drain valve by unscrewing the transparent inspection cover of oil drain pipe in cubicle. Fix inspection cover. Functional test of heater and thermostat operation. Set thermostat operation contact at _ _ _ ºc (as per manufacturer standard setting).

5.8

5.9 5.10 5.11 5.12 5.13

5.14

5.15 5.16 5.17 5.18 5.19

6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8

GENERAL CHECKS Cables are well supported at various cable clamps All cable glands are properly tightened. All screws/bolts of piping are properly tightened. Painting of oil drain and Nitrogen pipe line. The embedded oil drain pipe from oil pit fits well into the pipe connection collar of cubicle. Transformer oil drain valves and Nitrogen Injection valves and Isolation valve above cubicle are open. Main Nitrogen cylinder valve is open. Locking pin for oil drain and locking pin for nitrogen release are in operation position.

PLEASE √ AFTER TEST

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11.2 Automatic Mulsifire System 11.2.1 Description

This system is widely used for fire fighting of outdoor transformers. Spray type fire protection essentially consists of a network of projectors and an array of heat detectors used to sense high temperature near the transformer / reactor to be protected. If the temperature exceeds the set value, the automatic mulsifire system sprays water at high pressure through a Deluge valve from the pipe network laid for this system. Fire detectors located at various strategic points are on the surface of the transformer to control fire on any burning oil spilled over.

11.2.2 Subsystems used to make a complete mulsifire system a) Main Hydrant

This is used to carry the water to various parts of the switchyard or transformer substation and forms the backbone of the system. Sturdy corrosion-free pipes and valves are used for this purpose. The materials should be able to withstand fire for a reasonable duration.

b) Fire Detector

Fire detectors can either be thermocouples or specially designed bulbs which burst when they experience a high temperature and release any valves or checking device to start the water supply.

c) Ring Mains and Nozzles

Ring mains, which surround the transformer are provided to feed the water to the nozzles at various levels. Since the water pressure is high, the ring mains should be designed to withstand this pressure. Nozzles should be located such that the water spray, in the event of a fire, envelopes the entire surface of the transformer. The whole system should be periodically checked to detect any leakages. .

d) Pumps

Pumps are provided to fill the hydrants initially and to maintain its pressure. Pumps driven by electrical motors are a standard provision; however, the standby pumps should preferably be diesel engine driven. It is recommended that the main and standby pumps in a pump house be segregated.

11.2.3 Electrical Safety

As per Powergrid specification, from safety considerations, the following electrical clearances are recommended between the mulsifier system pipe work and live parts of the transformer to be protected. §§

420 kV bushing

3500 mm

§§

245 kV bushing

2150 mm

§§

145 kV bushing

1300 mm

§§

52 kV bushing

630 mm

§§

36 kV bushing

320 mm

11.2.4 Installation Care §§

Deluge Valve shall be water pressure operated manual reset type.

§§

Each Deluge valve shall be provided with a local panel from which will enable manual electrical operation of the valve.

§§

In addition to this, each valve shall be provided with local operation latch.

§§

Test valves shall simulate the operation of Deluge valves and shall be of quick opening type

POWER TRANSFORMER - STANDARDISATION MANUAL

12 Terminal Connector 12.1 Selection Criteria

Type of Connector (Construction) a)

Bolted type

b)

Crimping type

c)

Wedge type

d)

Welded type

Type of Connector (Functional) a)

Horizontal / Vertical / Through type

b)

Rigid / Flexible type (for Tubular Bus)

12.2 Technical Data Required for Design of Connector a)

System Voltage

b)

Continuous current rating

c)

Short time rating

d)

Ambient temperature & limit of maximum temperature rise

e)

Visual corona withstand voltage (for connectors of 220 kV and above)

f)

Maximum permissible RIV level at a specified voltage (for connectors of 220 kV and above)

g)

Size of Busbar & direction of approach

12.3 Design Criteria a)

To carry the desired current safely

b)

To withstand the mechanical loads imposed during erection / during short circuit

c)

To offer lowest resistance in the current path

d)

To limit the visual corona & RIV within permissible level

e)

To avoid sharp edges so that busbar does not get damaged during erection / in service

12.4 Tests on Connectors 12.4.1 Type Tests a)

Carried out on three samples of each type

b)

Dimensional check & visual examination

c)

Short time current test

d)

Visual corona withstand test & RIV measurement (for connectors of 220 kV and above)

e)

Temperature rise test

f)

Resistance Test

g)

Tensile test (Slip test)

h)

Galvanizing test on bolts & nuts

12.4.2 Acceptance Tests

Carried out on random selected samples during inspection & to be witnessed by customer’s representative (on 0.5% of quantity) a)

Dimensional check & visual examination

b)

Tensile Test (Slip test)

c)

Resistance test

d)

Galvanizing test on bolts & nuts

12.4.3 Routine Tests: Carried out on 100% quantity by manufacturers a)

Dimensional Check

b)

Visual Examination

12.5 Applicable Standard: IS: 5561

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ANNEXURE 2.4 PT 100 Resistance Temerature Vs Resistance (BS 1904: 1984 & IEC 751: 1985)

POWER TRANSFORMER - STANDARDISATION MANUAL

ANNEXURE 2.5 PT 100 Temerature Vs Output Signal Temperature Range: 0 - 150 oC Signal Range: 4 - 20 mA

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POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 3 Contract Drawings for Power Transformers

Working Group Members Mr. V. M. Varkey

- SIEMENS Ltd.

Mr. P. Ramachandran

- ABB Ltd.

Mr. Anilkumar Bhatia

- CGL

Mr. Shekhar Vora

- CGL

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POWER TRANSFORMER - STANDARDISATION MANUAL

CHAPTER - 3

CONTRACT DRAWINGS FOR POWER TRANSFORMERS 1. INTRODUCTION

This part of Manual lists the typical drawings submitted by manufacturer to the customer for approval and reference. The purpose of these drawings is to ensure that transformers being planned for manufacture meet the guaranteed technical particulars as per order, functional requirements as per customer specifications and interfaces at site. The Manual lists up the minimum details required in drawings and can be used as a check list for manufacturers, customers and consultants while preparing, verifying and approving these contract drawings.

2. LIST OF CONTRACT DRAWINGS Drawings list should have the revision status and date of submission / approval. 1.

Rating & Diagram Plate

2.

General Arrangement drawing for Transformer

3.

List of Accessories

4. Bill of Materials 5.

Foundation Plan

6.

Bushing Details

7.

Transport Dimensions

8. General Arrangement Drawing of Marshalling Box/ Cooler Control Cubicle 9.

General Arrangement Drawing of RTCC panel

10. General Arrangement Drawing of Junction box (if applicable) 11. Tap Changer Control Scheme 12. Cooler Control Scheme 13. Alarm / Trip Indication Scheme 14. Interconnection between DM and RTCC 15. General Arrangement Drawing for Cable Box (If applicable) 16. General Arrangement Drawing for bus duct termination (if applicable) 17. Valve Schedule Plate 3.

GENERAL GUIDELINES a.

All drawings shall be “to scale”

b. Drawings can be either in first angle or third angle projection. Angle of projection shall be mentioned in drawing. Preferred projection is First Angle Projection. c.

Title block shall contain customer reference (Customer name, PO/LOI number), Transformer MVA rating and voltage.

d.

All drawings may be either in A3 or A4 size for easier up-keeping.

e.

Drawings shall also be submitted in soft form.

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4.

MINIMUM DETAILS REQUIRED IN DRAWINGS 4.1 Rating & Diagram Plate §§

Rating & Diagram Plate drawing shall be in line with the guide lines in CBIP Transformer Manual.

§§

Plate can be made in one part or two. In case of two plates, cross reference shall be given in both sheets.

§§

Keep blank columns to fill after testing for % Impedance, measured losses, weight schedule and oil volume for first filling at site. Weight schedule shall contain (a) Core - coil assembly weight (b) Tank & fittings weight (c) Oil weight (d) Total Weight, (e) Transport weight (f) Net copper weight (g) Net silicon steel weight (h) Net mild steel weight (i) Type, grade and standard of oil

§§

Transport weight can be either oil filled or gas filled (Dry Air or Nitrogen) depending on transport limitations & road route survey. Hence, it shall be indicated as Transport Weight (with oil / without oil)

§§

Material of rating plate shall be stainless steel of minimum 1.0 mm thickness.

§§

Location and terminal markings of BCTs.

§§

Diagram plate shall indicate actual physical connections of windings (e.g. line entry of HV, with two halves in parallel, set of parallel / series windings in two limbs of core etc.)

§§

Provision of special accessories connected to windings, zinc oxide elements across regulating winding, tie-in-resistor in tap changer, external neutral grounding resistors etc.

§§

In case air cell is provided in conservator, add a note “Conservator is fitted with an air cell”.

§§

CT details like ratio, accuracy class, burden, Knee point etc.

§§

Rating Plate Drawing shall be in English language. In second language on request.

4.2 General Arrangement Drawing §§

All accessories & fittings can be numbered with standard logic in line with DIN 42513 so that same number can be used for identical items. (Annexure 3.1).

§§

Approximate Weight & Oil quantity schedule (Weight of core-coil assembly, tank & fittings, weight & volume of oil for first filling, total weight of completely assembled transformer and transport weight (gas or oil filled) as per final design.

§§

Minimum electrical clearances (Phase – Phase & Phase – Earth) as per CBIP guidelines / customer specifications.

§§

Minimum four views (Plan, Elevation, Right hand side & Left hand side view looking from HV side). 3D views can also be given for additional clarity.

§§

View showing maximum lifting weight / height of core – coil assembly or upper tank as the case may be and maximum clearance over tank top required for taking out the bushing.

§§

Tank Earth pad details.

§§

Core grounding details through terminal board or bushings suitable for 2 kV AC (one minute) isolation test. In case of large transformers (100 MVA and above) the core, core clamp connections shall be brought out independently at tank cover in a terminal box and earthed to ground.

§§

OLTC diverter switch to main tank equalizing details (applicable in case of OLTC only)

§§

Transformer center line (reference line) shall be the center line of rail gauge.

§§

Overall dimensions and maximum dimensions on either side of Transformer center line shall be indicated.

§§

Show dimensions up to bushing top terminals from rail level for interface between Transformer and station equipments.

§§

Show the height and other co-ordinates upto bus duct/SF6 duct and cable pot head mounting with a tolerance of ±10mm

§§

All dimensions to show the height shall be from rail level, until and unless specified in technical requirement.

POWER TRANSFORMER - STANDARDISATION MANUAL

§§

Transformer pull out direction shall be marked and make sure that there are no obstructions for pulling out transformer from the foundation.

§§

Make sure the jacking pad position is not fouling with the rail line.

§§

OLTC conservator shall preferably be at same level as main conservator level.

§§

Buchholz relay shall be accessible for inspection, preferably from tank top.

§§

Accessibility to ladder and from ladder to tank top shall be clear from other accessories and pipelines. Ladder shall be provided with anti-climbing device.

§§

Positioning of cable box shall not be in the path of transformer dragging out path.

§§

It is preferable to mount the coolers on the transformer tank instead of separate mounting.

§§

Dial of magnetic oil level indicator shall be visible from the ground.

§§

Provision shall be made on tank cover for fixing safety barriers.

§§

If air cell is provided in the conservator, air cell failure indication (by air operated relay or oil sight window) shall be provided.

§§

Upper filter and sampling valves shall be accessible from ground level. All valves shall be provided with identification labels.

§§

Rating and diagram plate shall be visible and near to OLTC driving mechanism. Marshalling box with indicators shall be near to it. Dials of all indicating and protection meters shall be visible clearly when viewed from the front of transformers.

§§

Following notes and cross reference document numbers shall be given. §§

Tolerance on weights and dimensions will be ± 5% unless marked separately.

§§

External painting system and shade number e.g. shade number (631 of IS:5), epoxy zinc primer + epoxy intermediate + polyurethane paint (preferred system)

§§

Document number of Bill of Material for cross reference, if accessories are listed up in a separate drawing

§§

Drawing numbers of Rating & diagram plate, Valve schedule plate, Foundation plan, Transport dimension and bushings.

§§

Design features generally meet the statutory, regulatory and safety requirements in terms of earthing arrangement, danger / warning labels, air clearances and provision of pressure relief device, gas operated relay and earthquake withstand clamping to foundation.

§§

Terminal Connector shall be arranged by Customer.

4.3 List of Accessories §§

List of Accessories can be on separate sheets. GA drawing number shall be given as a cross reference.

§§

Description, Make and quantity of all accessories shall be given.

§§

Items disassembled for transport shall be indicated clearly.

§§

Mercury filled actuating switches shall be avoided in all accessories.

4.4 Bill of Materials §§

Bill of materials shall be on separate sheets. One or more A4 / A3 sheets can be used. GA drawing number shall be given as a cross reference.

§§

Description, Make and quantity of all accessories shall be given.

4.5 Foundation Plan §§

Constructional and fixing details of foundation bolt.

§§

Foundation bolts shall be under the scope of transformer supplier. Grouting of bolt shall be done at the time of transformer erection for matching purpose.

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POWER TRANSFORMER - STANDARDISATION MANUAL

§§

Load on each support shall be clearly stated.

§§

Transformer Pull out direction shall be marked in line with GA

§§

Foundation bolt shall be part of BOM.

§§

Rail gauge shall be marked in foundation drawing.

§§

Anti-earthquake features in foundation/clamping (in case of transformers for seismic zones).

4.6 Bushings §§

Bushing shall be as per latest relevant IS/IEC/CBIP specifications

§§

Short time current rating shall be 25 times rated current for 2 second up to 4000 A bushing and 100 kA for 2 second for bushings above 4000 A as per IS/IEC, or as specified by Purchaser.

§§

Maximum angle of inclination and cantilever strength shall be indicated.

§§

Arcing horns are not recommended for the bushings.

§§

Material of components shall be indicated.

§§

Weight of oil and bushing shall be indicated.

§§

Bushing top terminals shall be marked.

§§

Test tap details shall be shown in bushing drawing.

§§

Creep distance shall be 31 mm / kV for all bushing upto 420 kV in open air. Creep distance is not applicable for oil to oil to SF6 bushing. Creep distance for bushing inside cable box / bus duct shall be 20 kV / mm minimum.

4.7 Transport Dimensions §§

Center of Gravity during Transport condition must be clearly marked.

§§

Transport condition (oil filled /gas filled) shall be indicated. In case of gas filled, clearly identify whether it is Dry air or Nitrogen. Gas filled transport shall be with a positive gas pressure.

§§

Transport weight shall be clearly indicated.

§§

Lifting bollards / Jacking Pads / Lashing lugs and Pulling eyes shall be identified.

§§

Impact recorder location (if applicable)

§§

Direction of transport movement shall be indicated.

4.8 General arrangement Drawing of Marshalling box / Cooler Control Cubicle §§

Cubicle shall be according to guide lines in CBIP Transformer Manual.

§§

Degree of protection shall be IP:55

§§

Glass window shall be at a level to view the temperature indicators.

§§

Undrilled gland plate for use by customers shall be provided.

§§

External & internal Paint type and colour shade shall be indicated.

§§

Cable and lug size shall be specified along with gland sizes.

4.9 General Arrangement Drawing of RTCC Panel §§

RTCC panel shall be suitable for IP:41 degree of protection.

§§

External & internal Paint type and colour shade to be furnished.

§§

Not more than two wires shall be taken from any terminal

4.10 General Arrangement Drawing of Junction Box (if applicable) §§

In case of floor mounted M/Box, a separate junction box shall be mounted on transformer to terminate all wirings.

§§

Interconnection between junction box to M/Box to be done at site.

§§

Junction box shall be suitable for IP:55 degree of protection

POWER TRANSFORMER - STANDARDISATION MANUAL

4.11 Tap changer control scheme

Tapchanger 4.11.1 Besides the local and remote electrical control, on-load tap changers, when specified, should be suitable for remote electrical parallel control as in clause 4.11.2. 4.11.2 Remote Electrical Parallel Control (Figure 3.1) §§

In addition to the methods of control as in clause 2, the following additional provision shall be made.

§§

Suitable selector switch be provided, so that anyone transformer of the group can at a time be selected as ‘Master’, ‘Follower’ or ‘Independent’.

§§

Necessary interlock blocking independent control when the units are in parallel, shall be provided.

§§

The scheme will be such that only one transformer of a group can be selected as ‘Master’.

§§

An out-of-step device shall be provided for each transformer which shall be arranged to prevent further tap changing when transformers in a group operating in ‘Parallel control’ are one tap outof-step.

4.11.3 On-load Tapchanger Control Scheme A. The control scheme for tap changer can be as under: §§

Non-automatic independent - The scheme used for independent control from local or remote panel.

§§

Non-auto / automatic independent - The scheme used for independent control with automatic voltage control relay and line drop compensation as optional. If required, non-auto condition can be availed.

§§

Non-automatic simultaneous parallel operation - The scheme used for non-automatic simultaneous parallel operation.

§§

Non-automatic / automatic simultaneous parallel operation - The scheme used for simultaneous parallel operation with automatic voltage control relay and line drop compensation as optional. If required, non-auto condition can be availed.

B. General §§

Local control items shall be mounted inside the on-load tap changer driving mechanism or marshalling box. Remote control items are to be mounted on remote control cubicle installed in the control room. All the control items are to be mounted in easily accessible position and clearly labeled. All control item shall be of best quality and or class most suitable for working under the conditions specified and shall withstand the variation of temperatures and atmospheric condition arising under working conditions so also withstand vibrations. All control items shall be wired and connected as per ‘Schematic Diagram of tap changer control equipment given in Scheme .

4.11.4 Motor

On-load tap changer driving gear Motor shall be of squirrel cage totally enclosed type and shall comply with Indian Standard IS: 325. It shall be suitable for direct starting and continuous running from 415 volts 3-phase 50 Hz supply. Motor shall be capable of continuous operation at any frequency between 48 and 51.5 Hz together with any voltage within 10 per cent of nominal value. Motor shall have ball or roller bearing and vertical spindle motor shall have bearing capable of withstanding thrust due to the weight of the moving parts. The stator windings shall be adequately braced and suitably impregnated to render them non-hygroscopic.

4.11.5 Overload Protection Relay

The overload protection relay shall be of robust, adjustable triple-pole construction. It should provide accurate and reliable protection against overload, single phasing, overheating and short circuit. The relay should be provided with temperature compensating device to off-set the effect of ambient temperature variation. For single phase motor, over-load protection device with feature similar to those of the three-phase motor as far as these are applicable shall be provided.

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4.11.6 Contactors / Relays

Contactors / Relays shall be of robust and compact construction and shall comply with Indian Standard IS : 2959. The electromagnetically operated air break type contactor with sufficient number of contacts shall be suitable for mounting on a vertical supporting structure. The contactors shall be suitable for operation at 110 Volts A.C.-15 per cent to + 10 per cent 50 Hz. Main and auxiliary contacts of contactor shall be suitably rated. For sufficient long life, these contacts shall be break type and shall make contacts practically bounce-free.

4.11.7 Control Supply Transformer

The control supply transformer shall be single phase having ratio 415/55-0-55V. It’s insulation shall be suitably impregnated to render it non-hygroscopic.

4.11.8 Control Selector Switches

All the control selector switches shall be of robust and compact construction and shall comply with Indian Standard IS : 4064 and 4047. The control switches shall be suitable for on-load switching of resistive and inductive loads. The switches shall incorporate multi air break type wiping contacts housed in an assembly of packets moulded from anti tracking material. The knob of the handle of the switch shall be suitably designed so that while operating a firm grip is obtained.

4.11.9 Remote Tap Position Indicator

Remote tap position indicator mounted on remote control panel shall show accurately same tap position as indicated by local tap position indicator on on-load tap changer. The remote indication can be by means of a digital indicator. Transmitter switch in the driving gear shall be make before break type. This switch in the driving gear shall be mounted in accessible position so that it can be cleaned and maintained regularly. The remote indicator mounted on control panel shall not be affected by normal auxiliary voltages supply variation.

4.11.10 Indicating Lamp and Indication Circuit Diagram

Necessary indicating lamps provided shall be of low watt consumption and of filament type or Neon or LED type. Lamps shall be of such construction so that these can be replaced very easily. Typical Indication Circuit diagram for RTCC panel is attached as Fig. 3.2.

4.11.11 Space Heater

Space heater of adequate capacity and robust construction shall be provided inside each control cabinet to prevent moisture condensation. Space heaters shall be rated for 240 volts 1 phase, 50 Hz supply. Heater shall be complete with miniature circuit breaker. Mounting of the heater and its location shall not cause localized intensive heating of control equipment and wiring.

4.11.12 Wiring

All the wiring shall be carried out for motor circuit with 1100 volts grade PVC insulated stranded copper conductors of size 2.5 sq mm and for control circuit with 650 volts grade PVC insulated copper conductor of size 1.5 sq mm suitable for tropical atmosphere. All wiring shall be in accordance with relevant IS. Engraved core identification ferrules, marked to correspond with the wiring diagram shall be fitted at both ends of each wire. Ferrules shall fit tightly on the wires and shall not fall off when the wire is removed. All wiring shall be terminated on terminal blocks through suitable lugs. Insulated sleeves shall be provided at all the wire terminations. All wiring shall be neatly bunched and cleated without affecting access to equipment mounted within the cabinet. One piece moulded 600 V grade terminal blocks complete with insulation barriers, terminal studs, washers, nuts and lock nuts shall be used. Terminal blocks shall be numbered for identification and grouped according to function. 10 per cent spare terminal blocks for control wire termination shall be provided on each panel. Terminal board rows should be spaced adequately apart to permit convenient access to wires and terminations. Terminal boards shall be so placed with respect to the cable gland plate (at a minimum distance of 70 mm) as to permit satisfactory arrangement of multi core cable tails without undue stress or bends. Opening of door should not disturb or stress the wire termination.

4.11.13 Voltage Regulating Relay (i)

Introduction: Voltage Regulating Relay is used for regulating the secondary voltage of power

POWER TRANSFORMER - STANDARDISATION MANUAL

transformers with on-load tap changers. The required dead band settings are set by setting the nominal value, and lower and upper levels independently. The time delay setting on the front panel eliminates the relay operations for momentary fluctuations of the regulated voltage thus reducing the number of operations of the tap changer. “ When the regulated voltage falls below the specified under voltage limit, the control relays are automatically blocked, i.e., there is no voltage correction, and a pair of contacts is made available for alarm. (ii) General Description: Voltage regulating relay should be designed for maximum operational simplicity for regulating the secondary voltage of power transformer with on load tap changers. The dead band (band width) can be set by setting the nominal value adjustment (NVA) to the required value “110 V + 10 per cent”.

The desired time delay can be set on the front panel and the control action will take place only if the voltage continues to remain outside the dead band after the time delay has elapsed. For voltage corrections requiring more than one tap change, time delay is initiated again before further tap change. The relay is reset automatically after the voltage is brought within the selected dead band. For repeated short duration voltage fluctuations on the same side of the dead band, the time delay is effectively reduced to provide a voltage time integral response of the regulator. Operation of the Raise Control relay is automatically inhibited when the voltage falls below the specified undervoltage limit. One pair of normally open relay contacts are provided to effect the tap changer, Raise and Lower operation and to trigger an alarm in case of under voltage conditions.

(iii) Specifications

Auxiliary Supply : -15% / + 10% 50 Hz



PT Supply (regulated Voltage) : 110 V ± 10 per cent 50 Hz



Sensitivity (Dead Band) : Nominal value adjustable (NVA)



and Nominal Value Range between + 0.75 to + 2.5 per cent



Time Delay Setting: Fixed, i.e., (Voltage independent) time delay continuously adjustable from 10 to 110 secs.



Time Delay Resetting: Instantaneous resetting with voltage deviation occurring in opposite direction.



Under Voltage Blocking: Internal blocking at 80 per cent of regulated value. Restoration at 85 per cent of regulated value.



Control Relays: One pair of normally open potential free contacts of suitable rating.



Control Operation: Single pulsed operation of sufficient duration to initiate tap changer.



Operating Temperature : – 5° to + 50°C



Option: Line drop compensator with resistive and reactive compensation of either polarity up to 20 per cent adjustable in steps or continuously and suitable for operation with 1 Amp. current transformer. If required suitable interposing current transformer to be used to get 1 Amp. Secondary current.



1 pair of NC (UV) contacts provided.

4.11.14 Line Drop Compensator (LDC) : Description i.

The Line Drop Compensator is an optional unit designed to match with the Automatic Voltage Regulator Relay. The unit is housed in the same enclosure or separately mounted.



The voltages at the generating end and at the receiving end are not the same due to the drop across the line. The LDC is used to compensate for this line drop, and the amount of compensation required is calculated as a per cent of the nominal voltage knowing the length of the line, its resistance/unit length, its reactance/unit length and the rated current, and set on the front panel.



The line current is stepped down to 1 Amp. & fed to the LDC. The resistive and reactive drops are simulated by having 90° phase shifted voltage and their polarity selected by polarity switches. The net compensation is then fed to the stepped down PT voltage.

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POWER TRANSFORMER - STANDARDISATION MANUAL

ii. Specifications

Resistive Compensation: 0-20 per cent of the regulating value continuously adjustable.



Reactive Compensation: 0-20 per cent of the regulating value continuously adjustable.



Input Rated Current: 1 Amp. 50 Hz.



Power Consumption: As required (CT burden will depend on power consumption).



Accuracy : 10 per cent.



Max. Overcurrent : 50 per cent of rated current (1.5 Amp.)



Polarity Selection : Both positive and negative compensation.

iii. Operating and Connection Requirements

Connection to the LDC unit are made through the rear panel terminals. The line current is stepped down to 1 Amp. 50 Hz and fed to the LDC. The net compensation is fed to the AVR circuit internal or external connections.



The required amount of percent R and per cent X compensation can be set on the front panel of the LDC. The polarity selector switches provide both positive and negative compensation. The per cent R and per cent X settings can be calculated from the following formulae:



√ 3*IL*RL



Per cent R = x 100 per cent



Per cent X = x 100 per cent



Where, IL = the primary rated current of the line.



VL = the voltage between lines of the power transformer.



XL = the line reactance in ohms/phase.



RL = the line resistance in ohms/phase.



Note : When LDC unit is not to be used, keep per cent R and per cent X settings to Zero, i.e., on minimum position.

4.11.15 Local Electrical Operation

This is possible only in the independent position. Set the switch ‘S32’ to Local position in D.M. Box. When switch ‘S32’ is kept on Local Mode, the control supply is made available to the Raise/ Lower switch in D.M. Using the Raise/Lower switch, Local Electrical Operation can be carried out.

4.11.16 Remote Electrical Operation

Remote Electrical Operation is carried out as follows :



Select one Transformer as “Master’ and others as its ‘Followers’. Then control supply will be tapped from D.M. Box to RTCC panel. Through the S/W S5 in RTCC1, which is set at ‘Master’ mode the Control supply is passed on to S/W S40 in D.M.1 which is an Odd/Even type of S/W. Its every 2nd position is linked e.g. 1, 3. 5. 7. 9. 11. 13. 15, 17 etc. This is to reduce number of interconnecting wires between RTCC panels. Suppose, Transformer 1, which is set as a “Master’, is at Tap 1, then through its odd/Even S/W in D.M.1, the Control Supply now goes to RTCC2 and from there it goes to Odd/Even S/W S40 of D.M.2. If the D.M.2 is also at Tap 1, then the control supply will be returned to RTCC2 set at “Follower’ mode and energizes Contactor K11 in RTCC2. Normally Open Contact of this K11 is wired up in RTCC1 and once it becomes closed, supply is available at Auto/Manual S/W S9, in RTCC1.



If the S/W S9 is set at Manual mode, then thro’ Push Button S1 or S2 Raise/ Lower operation is carried out. S1 will energize Contactor K4 for Raise tap and S2 will energize K5 for Lower contactor. Once the Raise or Lower Contactor in Master RTCC is picked up, it will extend the command to Follower RTCC to Raise or Lower Contactor and hence tap will be changed in both Transformers

POWER TRANSFORMER - STANDARDISATION MANUAL

simultaneously. If the Tap change operation is not completed within prescribed time duration, then the Timer is energized in D.M. Box which indicates Tap Change incomplete indication and D.M. MCB is tripped. Contactor K6 in RTCC will act as a Blocking relay which will block the Tap Change operation in case both RTCC’ s are not at same Tap position. In that case the timer K29 is picked up and will indicate Tap change Out of step indication.

Remote Auto Operation:



Remote Auto Operation is carried out as follows:



Set Auto/Manual S/W S9 on Auto Mode. The Raise/Lower Tap position decision is taken care by Automatic Voltage Regulator. As per its instruction either K4 or K5 is energized and then it gives command to Follower RTCC accordingly.

4.12 Cooler Control Scheme

Cooler control systems follow different practices and vary depending upon customer specs, manufacturers standard practices, however, standard control schematic will allow end customer to operate cooler control with more ease and similar representation of schemes and ease of maintenance. For cooler control schematics, standardisation of schemes will lead only to way of representation and mode of control like Auto/ Manual or Local/Remote. Typical Cooler Control Circuit is attached as Fig. 3.3.



The standard methods for drawing are as follows: 4.12.1 Index

Fig. 3.1: Type of symbols

A. Device Designation

Terminals to be defined in the following way:



All terminal number strips will start with letter “ X” and prefixed by “ –“. Individual terminal number will follow with “: “.



e.g. –X1: 12.



All contactors and Timers to be designated starting from letter “K” and prefixed by “-“.

e.g.-K5.

All MCBs and Phase failure relays to be designated with letter “F” and prefixed by “-“.

e.g.–F1.

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All control switches, sequence selector switches and push buttons to be designated with letter “S” and prefixed by “-“.

e.g.–S2.

AVR and annunciators to be designated with letter “A” and prefixed by “-“.



e.g. -A1.



Indicating Lamps to be designated with letter “H” and prefixed by “-“.



e.g. –H1.



Instruments like signal converter or Transducers, power supply module etc to be designated by letter “U” and prefixed by “-“.



e.g. –U2.



MPCB (Motor Protection Circuit Breaker) to be designated by letter “Q” and prefixed by “-“.



e.g. –Q10.

B. Ferruling and Signal linking

Where ever ferruling is required, it should be cross ferruling, indicating connection point near connection and originating point after it for easy tracing in the event of fault finding.

e.g.

Fig. 3.2



Where control schematic drawings are prepared in A3 or A4 size sheets, signal linking has to be done in following fashion:



Signal designation to start with letter “L” followed by signal number followed by the destination sheet and column in which destination is located. e. g.. --|L1/5.2. In this example, signal L1 is terminated on 5th sheet and in 2nd column.

POWER TRANSFORMER - STANDARDISATION MANUAL

C. Designation of Devices used in proposed scheme

Devices used in the attached drawings are: Sr. No.

Instrument

Purpose

Location

1

K4

Impulse relay for Raise Tap command

RTCC

2

K5

Impulse relay for Lower Tap command

RTCC

3

K6

Blocking Relay

RTCC

4

K11

Parallel Operation ready relay

RTCC

5

K29

Timer for Out of step indication

RTCC

6

S1

Push button for Raise Tap

RTCC

7

S2

Push button for Lower Tap

RTCC

8

S3

Push button for Emergency stop command

RTCC

9

S5

Master/Follower/Independent Selection Switch

RTCC

10

S9

Auto/Manual Selection Switch

RTCC

11

S40

Odd/Even Switch

D.M.

4.13 Alarm and Tripping Scheme

As per drawing (Figure 3.4).

4.14 Interconnection between DM & RTCC

As per drawing (Figure 3.5).

4.15 General Arrangement Drawing for Air filled Cable Box (If applicable) §§

Number & size of cables/phase as per customer specification shall be indicated.

§§

Cable box shall be provided with silica gel breather.

§§

Provision shall be made to move the transformer without disturbance keeping cable box in position.

§§

Earthing links shall be provided between cable box, disconnecting chamber and cable gland plate.

§§

Minimum one meter distance shall be provided from gland plate to bus bar.

§§

External Painting procedure of tank shall be applicable for both inside and outside of cable box.

§§

In case of ground mounted cable box support, same shall be in line with foundation plan.

§§

Cable Lugs and glands are not part of transformer supply.

§§

All bus bars and flexible inside the cable box shall be tin plated.

§§

Epoxy or porcelain insulator shall be used inside the cable box for bus bar support with minimum creepage distance of 20mm/kV

4.16 General Arrangement Drawing for Bus Duct termination (if applicable) §§

Position of bus duct mounting flange shall be dimensioned from transformer center line and from rail level with a tolerance of ± 5mm.

§§

Electrical clearance boundary shall be indicated so that bus duct (supplier scope) should not enter into the minimum clearance zone.

§§

Bushing top terminal details shall be clearly indicated for further connection by bus duct supplier.

§§

Drain plug shall be provided at the bottom most point of bus duct fixing flange on transformer.

4.17 Valve Schedule Plate §§

All valves, air vents and drain plugs shall be shown in valve schedule plate.

§§

Table shall contain, type, size, material and quantity of valves.

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POWER TRANSFORMER - STANDARDISATION MANUAL

5.

§§

Open and close indication of each valve at service, transport and oil filling should be marked.

§§

In case of water cooled Transformers, a heat exchanger single line diagram is required.

Typical Cable Schedule is enclosed for reference (Annexure 3.2).

6. Over and above, following drawings may also be generated if required: 1.

Cooler Diagram plate

2.

GA of common marshalling box (for 1-phase transformers)

3.

GTP (Technical data)

4.

Neutral formation Drawing (for 1-phase transformers)

5.

Combined foundation Drawing (for 1-phase transformers)

6.

Test plan/procedure.

7.

Others – Oil filling instruction, nitrogen fire protection system etc. if applicable.

8. QAP, FQP, TTR, Erection manual shall be submitted. 9.

Disposal plate

10. Roller Drawing 11. Terminal Connector details (if applicable)

POWER TRANSFORMER - STANDARDISATION MANUAL

ANNEXURE 3.1 Code for Transformer Accessories in line with DIN42513 1. AA001~XXX Valves 2. AB001~XXX

Drain plugs

3. AC001~XXX

Radiators, Oil to water heat exchangers, oil to air heat exchangers

4. AE001~XXX

Rollers, skid base, foundation bolts, anti-earthquake locking arrangements, refilling device for dry air

5. AN001~XXX

Cooling fans

6. AP001~XXX

Cooling pumps

7. AT001~XXX

Dehydrating breather, Air cell

8. BB001~XXX

Lower tank, upper tank, cover, conservator for main tank, conservator for tap changer

9. BQ001~XXX

Thermometer pockets, detachable ladders, jacking pad, lifting lugs, lashing lugs, pulling eyes, hook for safety belt, bracket for conservator, cooler pipe

10. BR001~XXX

Pipes

11. BZ001~XXX

Manholes, hand holes, inspection windows, terminal for tank earthing, rating plate, labels, valve schedule plate, caution plate, air cell installation notice

12. CF001~XXX

Accessories (protective, monitoring) bushings, tap changer, control cubicle, motor for tap changer, impact recorder, terminal connectors.

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ANNEXURE 3.2 Typical Cable Schedule M.BOX

Page

Ter.Strip

Terminal

X4

9

X4

To

MOTOR DRIVE(DM) Ter.Strip

Terminal

--

X1

2

10

--

X1

3

X4

11

--

X1

4

X4

5

--

X1

6

X4

6

--

X1

7

To

RTCC1

M.BOX

Page

Ter.Strip

Terminal

X5

1

X5

2

Ter.Strip

Terminal

--

X2

8

--

X2

9

X5

3

--

X2

10

4

--

X2

11

X5

5

--

X2

12

X5

6

--

X2

13

X5

7

--

X2

14

X5

8

--

X2

15

X5

9

--

X2

16

X5

10

--

X2

17

X5

11

--

X2

18

X5

12

--

X2

19

X5

64

--

X2

20

To

RTCC1

Page

Details

4Sq.mm,4core cable

3 Ph supply for OLTC Motor

2.5Sq.mm,2 core Cable

1 Ph AC Supply for Heater ckt

2.5Sq.mm,19 core cable for indication

TO RTCC Panel For LED Indicators

2.5Sq.mm,16 core cable for Annunciation

To RTCC Annunciator Window

Page

X5

M.BOX

Page CABLE DETAIL

Page

Ter.Strip

Terminal

Ter.Strip

Terminal

X5

13

--

X2

27

X5

14

--

X2

28

X5

15

--

X2

29

X5

16

--

X2

30

X5

17

--

X2

31

X5

18

--

X2

32

X5

19

--

X2

33

X5

20

--

X2

34

X5

21

--

X2

35

X5

22

--

X2

36

X5

23

--

X2

37

X5

24

--

X2

38

POWER TRANSFORMER - STANDARDISATION MANUAL

TJB

Page

To

RTCC1

Page

Ter.Strip

Terminal

Ter.Strip

Terminal

X5

33

--

X5

14

X5

34

--

X5

15

X5

36

--

X1

24

X5

37

--

X1

23

X5

11

--

X1

40

X5

12

--

X1

26

X5

19

--

X1

41

X5

20

--

X1

27

X5

27

--

X1

42

X5

28

--

X1

28

X5

66

--

X1

38

X5

67

--

X1

39

X5

8

--

X5

7

X5

9

--

X5

8

X5

16

--

X5

9

X5

17

--

X5

10

X5

24

--

X5

11

X5

25

--

X5

12

X5

64

--

X5

13

X5

65

--

X5

13A

To

RTCC1

M box

Page

X5

65

--

X5

42

66

--

X5

18

X5

67

--

X5

20

X5

68

--

X5

19

X5

69

--

X5

21

X5

70

--

X5

22

X5

71

--

X5

23

To

RTCC1

Page 123

X5

1

X2

124

X5

2

Page

To

4-20 mA i/p to TPI indicator 4-20 mA i/p to OTI/WTI indicator

4-20mA i/p HV-WTI to A-Eberle from Lumacense 4-20mA i/p LV-WTI to A-Eberle from Lumacense 4-20mA i/p TV-WTI to A-Eberle from Lumacense 4-20mA i/p OIL to A-Eberle from Lumacense

2.5Sq.mm,12 core cable for A-Eberle RELAY

Binary I/p to A-Eberle

2.5Sq.mm, 2 core cable for A-Eberle RELAY

CT i/p from LDC CT to A-Eberle

2.5Sq.mm,4core cable for A-Eberle relay

Fan & Pump start from A-Eberle

Page

X2 TJB

4-20mA i/p TPI to A-Eberle

Page

X5

TJB

2.5Sq.mm,24 core cable for A-Eberle RELAY

RTCC1

Page

X61

3

--

X5

38

X61

6

--

X5

39

X61

12

--

X5

38

X61

9

--

X5

40

139

140

POWER TRANSFORMER - STANDARDISATION MANUAL

DM

Page

To

RTCC1

Page

X1

9

--

X1

1

X1

10

--

X1

2

X1

12

--

X1

3

X1

13

--

X1

4

X1

14

--

X1

5

X1

16

--

X1

30

Emergency stop

X1

33

--

X5

41

X1

34

--

X5

28

Binary i/p to A-Eberle OLTC Loc /rem

X1

35

--

X5

29

X1

36

--

X5

27

To

RTCC1

CRP

Page

M.BOX

Page

Ter.Strip

Terminal

X5

25

X5

To

X4

15

X4

16

TJB

--

X5

1

26

--

X5

2

--

X5

3

X5

4

X5

27

X5

28

X5

53

--

X1

41

X5

54

--

X1

42

X5

55

--

X1

43

X5

56

--

X1

44

X5

57

--

X1

45

X5

58

--

X1

46

X5

59

--

X1

47

X5

60

--

X1

48

X4

7

--

X4

3

X4

8

--

X4

4

X4

1

--

X4

5

X4

2

--

X4

6

X4

1

--

X4

1

X4

2

--

X4

2

To

RTCC1

--

X2

X1

17

2.5Sq.mm,2 core cable for A-Eberle relay

PT supply Y-B to A-Eberle

2.5Sq.mm,24 core cable for M.BOX to TJB interconnection

Cooler control interconnection M.Box & RTCC

Page Terminal

Page

TAP RAISE & LOWER FROM a-Eberle

Page

Ter.Strip

DM

2.5Sq.mm,19 core cable for A-Eberle relay

Buchholz,PRD,PNRV & Fire detector signals

1 Ph. 240V ac supply 220V DC supply Lumesense 220V DC Supply RTD

Page 1

2.5Sq.mm,12 core cable from DM to RTCC interconnection

common

X1

18

--

X2

7

X1

19

--

X2

6

OLTC motor Trip TC Supply healthy

X1

20

--

X2

2

Tap changer In progress

X1

21

--

X2

4

OLTC in Local

X1

22

--

X2

5

OLTC in Remote

X1

24

--

X2

3

Tap changer incomplete

Fig. 3.1 (a): Typical Parallelling Circuit Diagram - Master Unit

POWER TRANSFORMER - STANDARDISATION MANUAL

141

Fig. 3.1 (b): Typical Parallelling Circuit Diagram - Follower Unit

142 POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.2 (a): Typical RTCC Indication Signals

POWER TRANSFORMER - STANDARDISATION MANUAL

143

Fig. 3.2 (b): Typical Indication Signals for Customer Panels

144 POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.2 (c): Typical Indication Signals to RTCC

POWER TRANSFORMER - STANDARDISATION MANUAL

145

Fig. 3.3 (a): Typical Supply Changeover Circuit

146 POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.3 (b): Typical Control Circuit for Fan and Pump Group – 1

POWER TRANSFORMER - STANDARDISATION MANUAL

147

Fig. 3.3 (c): Typical Power Circuit for Fan and Pump Group – 2

148 POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.3 (d): Typical Control Circuit for Fan Group – 1

POWER TRANSFORMER - STANDARDISATION MANUAL

149

Fig. 3.3 (e): Typical Control Circuit for Fan Group – 2

150 POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.3 (f): Typical Control Circuit for Fan Group 1 & 2

POWER TRANSFORMER - STANDARDISATION MANUAL

151

Fig. 3.3 (g): Typical Control Circuit for Pumps

152 POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.3 (h): Typical Indication Signals

POWER TRANSFORMER - STANDARDISATION MANUAL

153

POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.3 (i): Typical Indication Signals

154

Fig. 3.3 (j): Typical Heater and Lighting Circuit

POWER TRANSFORMER - STANDARDISATION MANUAL

155

POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.3 (k): Typical Device Configuration

156

Fig. 3.3 (l): Typical Device Configuration

POWER TRANSFORMER - STANDARDISATION MANUAL

157

POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.4 (a): Typical Alarm and WTI Circuit

158

Fig. 3.4 (b): Typical Trip Circuit

POWER TRANSFORMER - STANDARDISATION MANUAL

159

Fig. 3.4 (c): Typical Winding and Oil Temperature Signals

160 POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.4 (d): Typical Tap Position Signals

POWER TRANSFORMER - STANDARDISATION MANUAL

161

POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 3.5 : Typical OLTC Schematic Diagram

162

POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 4 STANDARD MANUFACTURING QUALITY PLAN (MQP)

Working Group Members Mr. S. K. Negi

- GETCO

Mr. M. M. Goswami

- POWERGRID

Mr. Y. V. Joshi

- GECO

Mr. Krishnan

- Mahindra Intertrade

Mr. Gautam Bhatia

- ENPAY

Mr. Baghel

- ATSA Conductors

Mr. Bharat Tolia

- Bharat Corrub

Mr. R S Thakkar

- GETCO

163

164

POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

CHAPTER - 4 STANDARD MANUFACTURING QUALITY PLAN (MQP)

It is a contract document between customer and supplier to express commitment for delivery of transformer as per agreed technical specification and match the type tested design. Over a period of time as the transmission grid has grown leaps and bounds, with HVDC and 765 kV AC network, this commitment document is gaining importance, because of rise in transformer failure rate and causing anxiety to maintain uninterrupted supply for consumer and industry. Customer always wishes that transformer manufactured and delivered must perform defect free service for its “specified design life”. It is always a challenge for supplier (manufacturer) to keep consistency in material used and manufacturing process, which are the main cause for variation in quality of transformer. While customer practically cannot monitor them and not expected to do so, manufacturers are on their toes to offer cost competitive and cost effective product. The cost of material plays an important role, considering the fact that majority of parts and components like bushing, OLTC, tank body, radiators, insulation, copper, core material etc. are outsourced. The selection of material, its grades / type and design philosophy ultimately decide the loss capitalization figures of final product. On the manufacturing process front, seamless integration of parts / components through mechanical and electrical design is the prerequisite. The change in sub-venders and skilled manpower time to time at factory also require due diligence to control and maintain the consistency of manufacturing process. Therefore a “balanced view“ is needed to manufacture and deliver ideal Transformer meeting contract specification and match type tested design. It is evident from above background that there is need of mutually agreed manufacturing quality plan (MQP). Apart from primary objective to have ideal transformer as per customer wish as explained above, the major benefit of MQP would be timely delivery and any conflict shall be address upfront, so that manufacturing could take place uninterrupted in a faithful manner. The role of design review is important to provide all necessary inputs for structuring the MQP. It is proposed in this power transformer standardisation manual to have MQP covering following elements: 1.

Material quality and characteristics.

2.

Stage inspection of material.

3.

Stage inspection and manufacturing process.

4.

Routine and Acceptance tests.

5.

To capture “Signature values “.

6.

Product dimension and physical condition before dispatch.

It is equally very important that Transformer is manufactured in a dust free clean environment with humidity control. Any compromise on this aspect will have adverse effect in expected design life of Transformer, however good is the quality of material used. Standard Manufacturing Quality Plan (MQP) has been designed in a manner to share the responsibility depending upon the source of supply, testing, location and criticality of test for the performance of Transformer. Responsibility of subvendor is important for testing of raw material and components (P), but manufacturer has to play a role of verification (V) as they have to integrate them for actual design of transformer. Similarly, responsibility of manufacturer is crucial for routine tests (P) but customer has to actively witness (W) these tests to ensure that results are complying the contract requirements and design review data.

165

Winding Conductor (PICC)/ (CTC)/ Lead wires

1

elongation % 30 min 32 min

As per design requirement

Max hardness should be RF 65, when measured in Rockwell ‘F” scale

Thickness tensile stregth (mm) (Nm/m2) Up to 2.5 205-265 >2.5-5.6 205-255

As per approved drawing

For annealed conductor 0.01727 ohm/mm2 / m(max) at 20 deg For half hard conductor 0.01777 ohm-mm2 / m (max)

Bare conductor Width /thick (mm) Tolerance (in ± mm) Up to 3.15 0.03 3.16 to 6.30 0.05 6.31 to 12.5 0.07 12.51 to 16 0.10 > 16 mm 0.10 Insulated conductor Covering thick(mm) Tolerance (%) 0.25 to 0.5 -10 0.51 to 1.25 -7.5 Over 1.25 -5

Acceptable Value

W - Witness Actual testing, verify and accept

IS 7404 IS 13730

6. 0.2% Proof strength of work hardened conductor

V - Verify and Accept

IS 7404 IS 13730

5. Hardness test

Performance

IS 7404 IS 13730

4.Tesile strength and elongation test

* Category of Responsibility: P - Actual Test

IS 13730

3. Insulation for bunched conductor a). No. of conductors. b). Thickness & width of bare conductor, Covered width & thickness c). Voltage test between strands

IS 1897 IS 13730 IS 7401

Reference / Standard

IS 13730

One sample per type per lot

Sampling rate

2. Resistivity at 20 deg.C

1. Visual & Dimensional check of Bare Conductor. Thickness & width of bare conductor, Covered width & thickness

Raw Material & Components

A

List of Tests

Item/Components

Sr. No.

P

P

P

P

P

P

Sub Vendor

V

V

V

V

V

V

Manufacturer

--

--

--

W

--

W

Customer

Category of Reponsibility*

166 POWER TRANSFORMER - STANDARDISATION MANUAL

Kraft Insulating Paper

2

Performance

IEC 605543-1 IEC 605543-5 IEC 60554-2, Methods of Test

IS 7404 IS 13730

Reference / Standard

17. Type test report

13. 0.5 to 1.0 µm/Pa.s 14. 5 mN m2 /g (min) 15. 6 mN m2 /g (min) 16. 10 %

1. Paper to be smooth, unglazed surface & free from dust particles 2. 0.8 ±0.05 gm/ cm3 3. Thick (µm) Sub (g/cm3) Tolerence 50 40 10 65 52 05 75 60 05 90 72 05 4. 8 % max 5. 93 NM/gm (min) 6. 34 NM/gm (min) 7. NA 8. NA 9. NA 10. 1 % max 11. 6 to 8 12. 10 mS/m (max)

Thikness (mm) Over/Upto Corner Radius(mm) Up to 1.0 0.50 1.01 to 1.60 0.50 1.61 to 2.24 0.65 2.25 to 3.55 0.80 3.56 to 5.60 1.00

Acceptable Value

W - Witness Actual testing, verify and accept

One sample per type per lot

Sampling rate

V - Verify and Accept

4. Moisture Content 5. Tensile Index MD 6. Tensile Index CD 7. Elongation at Break MD 8. Elongation at Break CD 9. Electric Strength in Air 10. Ash Content 11. PH of Aqueous extract 12. Conductivity of Aqueous extract 13.Air Permeability 14.Tear Index MD 15.Tear Index CMD 16. Water Absorption (Klemn Method) 17.Heat Stability a.) Reduction of Degree of Polymerization b.) Reduction of Bursting Strength c.) Increase of Conductivity of Aqueous extract.

1. Visual check & Measurement of Thickness 2. Density 3. Substance (grammage)

7. Radius of corner of bare conductor

List of Tests

* Category of Responsibility: P - Actual Test

Item/Components

Sr. No.

V

V

P

P

Manufacturer

Sub Vendor

--

W

Customer

Category of Reponsibility*

POWER TRANSFORMER - STANDARDISATION MANUAL

167

CRGO Laminations

3

Performance

IS 3024

Losses as per grade of CRGO lamination used

W - Witness Actual testing, verify and accept

One sample from offered lot

1. Visually defect free, as per design requirement 2. Less than 2 micron burr 3. As per IS 649 4. 10 Ω cm2 min average 05 Ω cm2 min individual 5. 4 % max increase in specific measured loss 6. As per table no. 4 of IS 3024

As per approved design

IS 3024 IEC 60404 ASTM 4343

Each Lot

One sample per lot

Acceptable Value

Reference / Standard

Sampling rate

V - Verify and Accept

7. Test for specific Watt loss test

5 Aging test (type test) 6. Test on stacking factor

2. Cutting Burr 3. Bend / Ductility test 4. Surface insulation resistivity check

Check following documents (a) Invoice of Supplier (b) Mill’s Test certificate (c) Packing List (d) Bill of Lading (e) Bill of Entry Check points: 1. Visual, Dimension & Thickness

List of Tests

* Category of Responsibility: P - Actual Test

Item/Components

Sr. No.

P

V

P

--

Manufacturer

Sub Vendor

V

--

Customer

Category of Reponsibility*

168 POWER TRANSFORMER - STANDARDISATION MANUAL

Pre-compressed Press Board

4

Performance

PD--> Perpendicular Direction

One sample of each size per lot

Sampling rate

V - Verify and Accept

IEC 606413-1 IEC 60641-2, Methods of Test

Reference / Standard

(2) Up to 1.6 mm TK -1.0-1.2 >1.6-3 mm TK -1.1-1.25 >3-3.6 mm TK -1.15-1.30 >6-8 mm TK -1.2-1.3 (3) Up to 1.6 -10 %; >1.6-3 mm - 7.5 % >3-3.6 mm - 5 %; >6-8 mm TK -4 % (4) Up to 1.6 -45 %; >1.6-3 mm - 50 % >3-3.6 mm - 50 %; >6-8 mm TK -50 % (5) Up to 1.6 mm TK -11 min > 1.6-3 mm TK - 9 min > 3 - 3.6 mm TK -7 min > 6-8 mm TK - 7 min (6) 6 % max (7) MD - 0.5 % max, CD- 0.7 % max, Thick -5 % max (8) 6-9 for solid boards (9) Up to 1.6 - 5 max (mS/m) > 1.6-3 mm - 6 max, > 3-3.6 mm - 8 max > 6-8 mm TK - 8-10 max (10) Up to 1.6 - 12 kV/ mm > 1.6-3 mm - 11 kV/mm > 3-3.6 mm - 10 kV / mm > 6-8 mm TK - 9 kV/mm (11) Up to 1.6 - 40 kV/ mm > 1.6-3 mm - 35 kV/mm > 3-3.6 mm - 30 kV / mm > 6-8 mm TK - 30 kV/mm (12) 1 % maximum MD CD (13) Up to 1.6 - 3 % 4 % >1.6-3 mm - 3 % 4 % >3-3.6 mm - 3 % 4 % >6-8 mm TK -3 % 4 %

(1) No surface defects

Acceptable Value

W - Witness Actual testing, verify and accept

CD--> Cross Direction

14. Tensile strength MD, CD 15. Ply Bond Resistance 16. Flexural strength MD, CD (Laminated Boards)

13. Elongation MD, CD

12. Ash Content

11.Electric Strength in Oil

10. Electric Strength in Air

8. pH of aqueous extract 9.conductivity of aqueous extract

6. Mositure Content 7. Shrinkage MD, CD & PD

5. Oil Absorption

4. Reversible part Compressibility

3. Compressibility C

1. Visual & dimensional check, thickness, width & length/. 2. Apparent Density

List of Tests

* Category of Responsibility: P - Actual Test

***TC --- Test Certificate

Item/Components

Sr. No.

P

Sub Vendor V

Manufacturer V

Customer

Category of Reponsibility*

POWER TRANSFORMER - STANDARDISATION MANUAL

169

Permawood

Porcelain Bushings (Hollow)

Polyster Resin Impregnated Glass Fibre Tape

Synthetic Rubber Bonded Cork sheet (SRBC)

5

6

7

8

Performance

IS 4253

IS 15208

1. Free from surface deffect 2. 70 ± 10 IRHD 3. 85 % max 4. NA 5.1550 kpa (min) 6. Should be satifactory when bent though 1800 round the material of diameter three times the thickness of specimen. 7. 25-35 % 8. 80 % min 9. Change in volume 15 % max for 70 hours at 100 deg c in oil 10. 5-8.5

1. Free from visual defect 2. 12 months 3. 0.25 to 0.35 mm (± 0.07) 4. 20 to 50 mm (± 2) 5. Min 200 N/mm 6. 27 (± 3%) 7. Max 200 °C

1. As per approved drawing. 2. As per IS 2099

2. 0.8 to 1.3 gm/cc 3. Max 7% 4. Min 5% 5. Min 60 KV 6. Min for LD - 700 KV /cm2 7. Min for LD - 1400 KV /cm2 8. Min for LD - 450 KV /cm2 9. Thikness (mm) Tolerance (+/- mm) 10 to 25 1.2 26 to 50 1.4 51 to 150 2.0

1. Shall be free from surface defect

Acceptable Value

W - Witness Actual testing, verify and accept

One sample per lot

Each lot

As per IS/ IEC

IS 2099

IS 3513 IS 1708 IS 1736 IS 1998

One sample of each size per lot

100%

Reference / Standard

Sampling rate

V - Verify and Accept

7. Compressibility 8. Recovery 9. Aging in Oil-Finish, Flexibility & change in volume 10. Ph value

1. Visual check, thickness, length, width 2. Hardness 3. Compression set 4. Side flow under compression 5. Tensile strength 6. Flexibility

1. Visual Check 2. Verification of shelf life 3. Thickness 4. Width 5. Tensile Strength 6. Resin Content 7. Softening point of resin

1. Visual & dimensional check. 2. Power frequency voltage withstand test

1. Visual & dimensional check, thickness, width & length. 2. Density 3. Moisture content 4. Oil Absorption at 90 °C 5. Electric Strength at 90 °C 6. Tensile strength 7. Compressive strength test 8. Shear strength age-wise 9. Thickness

List of Tests

* Category of Responsibility: P - Actual Test

Item/Components

Sr. No.

P

P

P

P

Sub Vendor

V

V

V

V

Manufacturer

--

--

--

--

Customer

Category of Reponsibility*

170 POWER TRANSFORMER - STANDARDISATION MANUAL

Condenser Bushing

Buchholz Relay

Bimetallic Terminal Connector

Marshalling Box

Remote Tap Changer Control Cabinet

9

10

11

12

13

Performance

1. Dimension & Visual Check 2. 2kV test for Auxillary wiring 3. Paint shade & Thickness 4. Wiring routing check 5. Functional Check 6. Verification of BoQ

1. Dimension & Visual check 2. 2kV test for Auxillary wiring 3. Paint shade & Thickness 4. Wiring routing check 5. Functional Check

1. Dimensional 2. Visual check 3. Tensile strength 4. Resistance

7. Loss of oil & Surge test

IS 3637

100%

100%

100%

1. As per approved drawing 2. 1 min withstand 3. As per approved drawing 4. Firm and aesthetic 5. As per approved drawing 6. As per approved drawing

1. As per approved drawing 2. 1 min withstand 3. As per approved drawing 4. Firm and aesthetic 5. As per approved drawing

1. As per approved drawing 2. Free form defects 3. As per type test report 4. As per type test report

1. As per approved drawing 2. No leakage 3. 2 KV for 1 min. withstand 4. Min 10 MΩ by 500 V DC megger 5. No leakage at 1.75 Kg/cm2 oil pressure for 15 mins 6. GOR - 1: 90 to 165 CC GOR - 2: 175 to 225 CC GOR - 3: 200 to 300 CC 7. GOR - 1: 70 to 130 CC GOR - 2: 75 to 140 CC GOR - 3: 90 to 160 CC

3. As per IEC - No flash-over/ puncture 4. No leakage 5. No leakage 6. As per approved GTP 7. As per approved drawing

1. Tan Delta - 66 kV - 0.7% Above 66 kV - 0.4% 2. As per approved GTP

Acceptable Value

W - Witness Actual testing, verify and accept

Approved drawing and specification

Approved drawing and specification

IS 5561

IS 2099 IEC 60137

100%

100%

Reference / Standard

Sampling rate

V - Verify and Accept

6. Gas volume test at 5° ascending towards conservator

1. Type & make 2. Porosity 3. High voltage 4. Insulation resistance 5. Element test

Routine Test (1) Measurement of dilectric dissipation factor and capacitance (2) Dry power frequency voltage withstand test (3) Measurement of partial discharge (4) Pressure test (5) Tightness test (6) Creepage distance (7) Visual & dimensional check

List of Tests

* Category of Responsibility: P - Actual Test

Item/Components

Sr. No.

V

P

P

V

--

--

--

--

W ----W W P V V V V V V

V

Customer

Manufacturer

P

P

P

P

Sub Vendor

Category of Reponsibility*

POWER TRANSFORMER - STANDARDISATION MANUAL

171

Air cell (Flexi Air Separator)

Roller Assembly

Oil & winding Temperature Indicator

Pressure Relief Device

Magnetic Oil Level Gauge (MOG)

Valves

Transformer Oil

14

15

16

17

18

19

20

Performance

Routine Test as per IS 335

1. Type, make & Visual 2. Leakage test/ Seepage test 100%

100%

As per IEEMA specification (see Chapter 6)

1. As per approved drawing & free from defect 2. No leakage

1. As per approved drawing & free from defect 2. Check pointer position for Max, Min and center level 3. Withstand for 1 minute 4. No leakage at 4 kg/cm2 5. Operate at Min level indication

1. As per approved drawing & free from defect 2. No leakage 3. Satisfactory operation at pressure release 4. 2 kV withstand for 1 min

W - Witness Actual testing, verify and accept

IS 335 IEC 60296

IS 778

--

IS 2500

100%

100%

--

100%

1. As per approved drawing 2. ± 1.5% of FSD 3. Withstand for 1 min 4. operation within ± 2° C of setting

1. Free from surface defect 2. For shaft as per MS EN8, BS 970-1 For roller wheel of cast iron IS 210 For roller wheel of Cast steel IS 1030

IS 8500

One sample per melt/ heat treatment batch

Acceptable Value

1. As per approved deawing 2. No leakage for 24 hours 3. No deformation

Reference / Standard

IS 3400

100%

Sampling rate

V - Verify and Accept

1. Type & make 2. Dial Calibration for level 3. 2kV HV test for 1 min between all terminal & earth 4. Leak test 5. Switch/contact operation test

1. Type & Make 2. Operating air pressure 3. Switch/contact testing 4. HV test

1. Type & make 2. Calibration 3. 2kV HV test for 1 min between all terminals & earth 3. Switch contact operation test

1. Visual & Dimensions. 2. Mech. Properties & Chemical composition of raw material used for shaft & roller forging

1. Make, Visual & Dimensions 2. Pressure test at 0.105 Kg/cm2 3. 10 times inflation and deflation test at 0.105 Kg/cm2

List of Tests

* Category of Responsibility: P - Actual Test

Item/Components

Sr. No.

P

P

V

P

P

P

P

P

P

V

P

Manufacturer

P

P

P

Sub Vendor

V

--

--

--

--

--

--

Customer

Category of Reponsibility*

172 POWER TRANSFORMER - STANDARDISATION MANUAL

Tank & Accessories

Radiators

OLTC

21

22

23

Performance

100%

V - Verify and Accept

3. Pressure test on divertor switch oil compartment 4. Mech. Operation test 5. Sequence test 6. Visual & Dimentional check 7. Operational test on Surge relay

1. Auxiliary circuit insulation test at 2kV for 1min. 2. Function test on OLTC

100%

one per design

6. Tank 6.1 Presseure test 6.2 Vaccum test

1. DP test on lifting lugs 2. Surface cleaning of header support and bracing details by sand/shot blasting 3. Air pressure test on elements 4. Dimensional check after final welding 5. Air pressure test on radiator assembly 6. Visual check of paint shade, paint film thickness & film adhesion

CBIP manual 2013

100%

1. Check for a fit up for butt welds on tank walls, base & cover 2. DP test on Butt welds after fit up & load bearing welds 3. Visual & Dimensional check after final welding 4. Air leakage test on assembled tank with turrets & on conservator 5. Visual check of paint shade, paint film thickness & film adhesion

4. Satisfactory operation for 1 complete cycle 5. Switching time within permissible limit 6. Free from defects 7. Satisfactory working of trip & reset

2. Satisfactory working as per drawing approved 3. No leakage

1. To Withstand for 1 min

6. As per tech spec, coating thickness more than 70 micron

5. 2 kg/cm2 for 30 minutes - no leakage

3. As per relevent standards /CBIP 4. As per approved drawing

1. No welding defect 2. Free from surface defect

6.1) Twice the normal head + 30 KN/m2 for 1 hr. Withstand 6.2) 760 mm of Hg for 1 hr. withstand

5. Paint thickness Outside: 155 micron Inside : 30 micron No peel-off

4. No leakage

3. Free from defect

2. Check for proper welding

1. Check for proper welding

Acceptable Value

W - Witness Actual testing, verify and accept

IEC 60214

IEEMA standard

CBIP manual 2013

Reference / Standard

Sampling rate

List of Tests

* Category of Responsibility: P - Actual Test

Item/Components

Sr. No.

P

P

P

W

W

P

P

P

Manufacturer

Sub Vendor

V

W

W

--

Customer

Category of Reponsibility*

POWER TRANSFORMER - STANDARDISATION MANUAL

173

Cooling Fans

Nitrile Rubber Gasket

Bushing CT

Remote Temperature detector

Oil pump

24

25

26

27

28

Performance

2. HV test 3. Oil pressure test 4. Locked rotor test

1. No load test

IS 2705

100%

100%

1. Satisfactory performance & no load losses within limit 2. 2 kV AC for 1 min withstand 3. 5 Kg/cm2 at 90° C for 30 mins withstand 4. Statisfactory operation of protection

1. 500 V AC for 1 min withstand 2. ± 1% of FSD 3. 10 MΩ min with 500 V DC megger

3. Rated current withstand for 1 min 4. As per IS 2705 5. 3 kV AC for 1 min withstand

1. As per approved drawing 2. As per IS 2705

1. Within tolerance 2. 70 ± 5 IRHD 3. 12.5 N/mm2 min 4. 20% max 5. 250% min 6. Max change in harness - 10 IRHD 7. Change in weight - 5 to 8.5% Change in thickness - 4% max Change in width & length - 0.2% max

1. As per approved drawing 2. As per approved drawing 3. 1.3 kV for 1 min or 1.8 kV for 5 sec 4. 10 MΩ min with 500 V DC megger

Acceptable Value

W - Witness Actual testing, verify and accept

--

--

BS 2751

1 sample/ Lot

100%

IS 2312

Reference / Standard

100%

Sampling rate

V - Verify and Accept

1. HV test 2. Calliberation accuracy check 3. IR value

1. Dimensions 2. Verification of terminal marking & polarity 3. Overvoltage inter-turn test 4. Determination of error 5. HV Test

1.Dimensions 2.Shore Hardness 3.Tensile Strength 4.Compression set test 5. Elongation at break 6. Accelerated aging in air 7. Accelerated aging in oil

1. Type & Make 2. Power consumption, rating test 3. HV test 4. Insulation resistance value

List of Tests

* Category of Responsibility: P - Actual Test

Item/Components

Sr. No.

P

P

P

P

P

P

P

P

P

Manufacturer

P

Sub Vendor

--

--

--

--

V

Customer

Category of Reponsibility*

174 POWER TRANSFORMER - STANDARDISATION MANUAL

3

2

One sample of each type

One sample of each type

One sample of each type

Dimensional check

Check for burr

Edge bow

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

Core Diameter

Leg Centre & Leg length

Assembly of limb Insulation & plates

Rectangularity of Core Assembly

Check for Overlaps & air gap at joints

Leaning of Core

Earthing of Core

Limb Clamping & Binding

Insulation test between core & core clamp / frame

Loss measurement on built up core assembly.

Visual check for drum lable and Conductor Size

100%

100%

Total stack height

Winding

100%

Visual check

Core Building

One sample of each type

Lamination for core

1

Visual check

In Process Inspection No of turns / disc

B

Sampling rate

Item/Process

Sr. No.

As per design drawings

As per specification / GTP

As per specification

Design drawing

Design drawing

Design drawing

Design drawing

Design drawing

Design drawing

As per design drawings

As per design drawings

As per design drawings

--

IS 3024

--

--

--

Reference / Standard

Within limit as per design

Within limit as per GTP

shall withstand 2 kV for 1 min

As per design drawings

Proper connection

No leaning

As per design

As per design

As per design

within specified tolerence of design

within specified tolerence of design

within specified tolerence of design

Free from defect

As per IS 3024

Less than 20μn

As per design drawings

Prime CRGO and Free from defect

Acceptable Value

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

Sub Vendor

P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

Manufacturer

V

W

W

V

V

V

V

V

V

W

W

W

W

V

V

V

V

Customer

Category of Reponsibility*

POWER TRANSFORMER - STANDARDISATION MANUAL

175

100%

100%

Continuity test

Inter-turn Insulation

100%

100%

100%

100%

100%

100%

100%

100%

Lead & coil indentification & marking

Brazing / Crimping of Joints

Visual chek for completeness and cleanliness

Ratio test

Magnetic balance test

Magnetizing current test

Alignment of Spacers/Blocks

HV test

Performance

100%

Visual check for intercoil insulation

Core Coil Assembly

100%

V - Verify and Accept

Mfgrs standard

--

2 kv for 1 min withstand

Aligned

Tolerance as per standards

Tolerance as per standards

Tolerance as per standards

Complete assembly shall be free from dust/ particles

Shall be smooth and no sharped age

As per design

As per design

As per design

No breaking of continuity

As per design

As per design

As per design

As per approval

As per approval

As per Factory drawing

As per Factory drawing

Acceptable Value

W - Witness Actual testing, verify and accept

As per IS 2026 / IEC 60076

As per IS 2026 / IEC 60076

As per IS 2026 / IEC 60076

--

--

--

--

As per design drawings

--

As per design drawings

As per design drawings

100%

Lead & coil indentification & marking

As per brazing procedure

Insulation arrangement

100%

Visual inspection of brazed joints

Customer approval

As per design drawings

--

Brazing procedure and brazer's qualification

As per approved drawings / Factory drawing

As per approved drawings / Factory drawing

Reference / Standard

Visual check for transposition 100%

100%

Dimensional checks i) Outer diameter ii) Inner diameter iii) Unshrunk height iv) Radial thickness

100%

Sampling rate

* Category of Responsibility: P - Actual Test

4

Nos of discs

3

No of turns / disc

Item/Process

Sr. No.

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

Sub Vendor

P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

Manufacturer

W

V

V

V

V

V

W

W

W

V

V

V

V

V

V

V

V

V

Customer

Category of Reponsibility*

176 POWER TRANSFORMER - STANDARDISATION MANUAL

100%

100%

100%

100%

Check for clearance from tank walls

Visual checks for crimped joint

Visual checks for bushing CT assembly tightness

Ratio test

100%

100%

100%

Dimensions

Pressure test

Vacuum test

100%

Checks for complete tightness before tanking a) Tightness of all joints / screws b) Application of thread locking adhesive c) Padding of top yoke d) Pressing of active parts e) Fitting of wall shunts & packing

Performance

100%

Drying

Ovening, Tanking and Oil filling

100%

Thickness of walls

Tank

100%

Check for cable sizes

* Category of Responsibility: P - Actual Test

7

6

100%

OLTC fitting & connections

Connections and checks before tanking

5

Sampling rate

Item/Process

Sr. No.

V - Verify and Accept

Manufacturer standard

Manufacturer standard

As per CBIP

As per CBIP

As per design

Low voltage tan delta and PI values shall be checked periodically and after achieving the satisfactory values the process will be declared complete

To withstand, permenat deflection shall not exceed as per specification

To withstand, permenat deflection shall not exceed as per specification

As per approved drawings

As per approved drawings

Tolerance as per standards

Assembly tightness

Shall be smooth and no sharped age

As per design

As per design

Manufacturer standard

Acceptable Value

W - Witness Actual testing, verify and accept

As per approved drawings

As per approved drawings

As per IS 2026 / IEC 60076

--

--

As per design drawings

As per design drawings

Manufacturer standard

Reference / Standard

--

--

--

--

--

--

--

--

--

--

--

--

Sub Vendor

P

P

P

P

P

P

P

P

P

P

P

P

Manufacturer

V

V

W

W

V

V

V

V

V

V

V

---

Customer

Category of Reponsibility*

POWER TRANSFORMER - STANDARDISATION MANUAL

177

100%

100%

100%

Check for oil qualtity before impregnation

Oil filling & Air release

Impregnation process

Performance

As per specification

100%

2 kV HV test between (i) Core & end frame (ii) Core & yoke bolts (iii) End frame and yoke bolts

* Category of Responsibility: P - Actual Test

As per design drawings

100%

Tanking of active parts and check for clearance from tank walls

V - Verify and Accept

Manufacturer standard

Manufacturer standard

As per specification

Manufacturer standard

100%

Cleanliness of tank before tanking

Reference / Standard

7

Sampling rate

Item/Process

Sr. No.

W - Witness Actual testing, verify and accept

Sufficient impregnation time shall be given before conducting the electrical test on the transformer

Manufacturer standard

As per specification

To withstand 2 kV for 1 min

As per design

Shall be clean.

Acceptable Value

--

--

--

--

--

--

Sub Vendor

P

P

P

P

P

P

Manufacturer

---

---

V

V

V

---

Customer

Category of Reponsibility*

178 POWER TRANSFORMER - STANDARDISATION MANUAL

Impedance between each pair of winding / Impedence Voltage

Excitation losses at 90, 100 and 110 % rated voltage measured by the average voltmeter method

Positive phase sequences impedance measurement on three phase transformers

Regulation at rated load and unity, 0.9, 0.8 lagging P.F.

Load losses, measured at rated frequency, by applying a primary voltage sufficient to produce rated current in the windings with secondary windings short circuited

Separate source voltage with stand test.

Induced over voltage with stand test

Auxiliary losses (fans. Pumps etc.)

SFRA test

Zero Sequence impedance test

Tests on tap-changer (IEC:214)

Tan delta & capacitance measurement test for bushings and windings

Tests on transformer oil including DGA on selected sample as per IS:9434/IEC:567, before and after temp rise test and at final stage before dispatch. Corrosive sulphur detection test as per ASTM D1275 subjecting oil for 150oC for 48 hrs.

4

5

6

7

8

9

10

11

12

13

14

15

16

Acceptable Value

IS:2026 / IEC 60076 As per applicable / specification standard

Reference / Standard

W - Witness Actual testing, verify and accept

100%

Sampling rate

V - Verify and Accept

Polarity and phase relationship (Vector group)

3

Performance

Turn ratio for all sets of windings on each tap, with percentage error / Voltage

2

* Category of Responsibility: P - Actual Test

Resistance of each winding.

1

Routine Tests

C

Description of Test

IS:2026 / IEC 60076 / specification

Test

As per applicable standard

Sr. No.

W W W

W

P P P

P

P

P

P

P

P

P

P

P

P

W

W

W

W

W

W

W

W

W

W

W

P

P

W

Customer

P

Manufacturer

Category of Reponsibility*

POWER TRANSFORMER - STANDARDISATION MANUAL

179

HV withstand test on auxiliary equipments and wiring

Measurement of Insulation Resistance

Measurement of acoustic noise level

Measurement of harmonics of no load current

Measurement of Partial Discharges of transformer

Measurement of no load current with 415 V AC supply on LV side.

Tests on air cell

ACLD test (For 220 kV class transformer)

Moisture content in active part measurement test

20

21

22

23

24

25

26

27

28

Short circuit withstand capability test (Optional)

Tests on OLTC

4

5

Reference / Standard

IEC 60214

IS:2026 / IEC 60076

CBIP manual

IS:2026 / IEC 60076

IS:2026 / IEC 60076

Acceptable Value

As per standards

As per standards

Permanent deflection within limit as per length of plate used.

As per standards

As per standards

0.5 % max

W - Witness Actual testing, verify and accept

One from Lot or as agreed between Manufacturer and Purchaser.

V - Verify and Accept

Vacuum and pressure test on tank

3

Performance

Lightning Impulse Voltage withstand test with chopped wave Switching Impulse Voltage withstand test

2

* Category of Responsibility: P - Actual Test

Temperature rise test

1

Type Tests

Magnetic Balance & current test on all winding

19

D

Tank leak test at 5 psi (35 kN/m2) for 12 hrs with oil & 1 hr with air.

18

C

Sampling rate

IS:2026 / IEC 60076 / specification

Description of Test

Test

Sr. No.

As per applicable standard

W

P

P

W

P

P

P

P

P

W

W

W

W

W

W

W

W

W

P

P

Customer

Manufacturer

Category of Reponsibility*

180 POWER TRANSFORMER - STANDARDISATION MANUAL

Short Time Current withstand test on offered HV and LV terminal connectors for 40 kA for 3 Sec for 220 kV & 132 kV Class and 25 kA for 3 sec for 66 kV & below class

3

Verification of completeness of accessories

Bushings

Conservator tank

Transformer oil

Check Nitrogen / dry air pressure after filling

Mesurement of dew point of nitrogen or dry air before and after filling in tank before dispatch

Check proper blanking of all openings and leakage, 100% if any

Provision of Impact recorder / tracking system

Check for soundness of packing

3

4

5

6

7

8

9

10

11

Performance

Radiators

2

V - Verify and Accept

Acceptable Value

IS:5561

IS:2026 / IEC 60076

0.15 to 0.2 kg/ cmsq above ATM Pr

--

--

IS 13947/IEC 60529: -2001

Reference / Standard

W - Witness Actual testing, verify and accept

100%

100%

100%

100%

100%

100%

100%

100%

100%

Pipes and headers

100%

Sampling rate

1

Packing & Dispatch - Main tank

Measurement of transferred surge in LV due to Lightning impulse on HV & LV

2

* Category of Responsibility: P - Actual Test

F

Degree of protection (IP55) for control cabinets & RTCC panel, OLTC driving mechanism, terminal boxes of PRV, MOG, Buchholz Relay, pump motors, fans etc

1

Special Tests (Optional)

E

Description of Test

Manufacturer’s Standard

Test

Manufacturer’s Standard Manufacturer’s Standard

Sr. No.

--------

P P P P P P P

P

P

P

--

--

--

--

W

P

P

W

P

--

W

P

P

Customer

Manufacturer

Category of Reponsibility*

POWER TRANSFORMER - STANDARDISATION MANUAL

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182

POWER TRANSFORMER - STANDARDISATION MANUAL

POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 5 Transportation, Erection, Testing and Commissioning

Working Group Members Mr. S. K. Negi

- GETCO

Mr. Gautam Mazumdar - CGL Mr. Umapathi

- Voltech

Mr. Y. V. Joshi

- GETCO

Mr. D. C. Patel

- J. H. Parabia

Mr. N. G. Patel

- GETCO

Ms. Asha Agravatt

- GETCO

183

184

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POWER TRANSFORMER - STANDARDISATION MANUAL

CHAPTER - 5 TRANSPORTATION, ERECTION, TESTING AND COMMISSIONING INTRODUCTION Considering main objectives of standardisation Manual, this chapter will cover important procedures, check points, flow charts, suggestive tools-tackles, testing formats, etc. which are required for transport, storage, installation & erection, testing and commissioning of power transformer for its good performance during operation.

Transportation and Unloading at site Power transformers are usually very reliable, but it requires lot of care during all stages of its life & particularly during transportation. If a transformer experiences any mechanical shocks more than suggested “g” level, damage that may occur covers §§

Displacement / distortion of windings or core

§§

Inter turn insulation damage due to movement of active part

§§

Loosening of winding clamps due to vibration

§§

Compromise safe clearances between tank & active parts

It is therefore required that transporter should take note of following transport restrictions. §§

Axial load distribution

§§

Brake force distribution between tractor & trailer as per trailer manufacturer’s guide.

§§

Maintain proper ratio between the gross mass of the trailer and tractor

§§

Adhere to designated route.

§§

Avoid travelling during foggy, heavy rain, etc restricting ambient visibility to less than 500 meters.

§§

Actual survey & planned route

§§

Permissions

1] Modes of Transport According to weight of Transformer to be transported, the size & capacity of Trailer, plinth size and mode of transport can be standardised as below. Sr. No.

Standard Ratings

Approx. Weight in MT

Trailer size (No. of axles)

Mode of Transport

A

Two Winding Transformers

1

132/33 kV, 40/50 MVA

70

6

ROAD

2

220/66 kV, 100 MVA

107

9

ROAD

B

Auto Transformers

1

132/66 kV, 40/50 MVA

60

5

ROAD

2

132/33 kV, 25/31.5 MVA

50

4

ROAD

3

220/132 kV, 100 MVA,

84

7

ROAD

4

220/132 kV, 160 MVA,

83 - 130

7 - 10

ROAD

185

186

POWER TRANSFORMER - STANDARDISATION MANUAL

5

400/220/33 kV, 315 MVA, 3Ø

185 - 230

14 - 18

ROAD

6

400/220/33 kV, 500 MVA, 3Ø

250

19

ROAD / RAIL

7

400/220 kV 167 MVA, 1 Ø

85 - 104

7-8

ROAD

8

765/√3 // 400/√3, 333 MVA, 1 Ø

160

13

ROAD / RAIL

9

765/√3 // 400/√3, 500 MVA, 1 Ø

192

15

ROAD / RAIL

C

Generating Transformers

1

15.75/235 kV, 315 MVA 3Ø

190

15

ROAD

2

15.75/420 kV, 315 MVA, 3Ø

230

18

ROAD

3

21/420 kV, 200 MVA, 1Ø

155

12

ROAD

4

21/420 kV, 260 MVA, 1Ø

180

14

ROAD

5

21/420 kV, 333 MVA, 1Ø

220

17

ROAD

6

21/765 kV, 260 MVA, 1Ø

175

14

ROAD / RAIL

7

21/765 kV, 333 MVA, 1Ø

205

16

ROAD / RAIL

* Note: Weights are approximate and may vary from manufacturer to manufacturer

Mode of transportation may be rail, road or water. Depending on size of transformer, destination, delivery time & route limitations the mode of transportation can be decided. a)

Rail Transport



Where the weight and dimension of main body exceed limits, special well wagons are employed. Detached parts are packed/crated and normally dispatched along with main body of transformer so that all the parts are received at the destination with unit. If the siding facility is not available either at loading or unloading end, mobile cranes or railway cranes can be used for loading into wagons.

b)

Road Transport



Multi axle tractor driven, low platform trailers are used for transporting transformers on roads. Transformers may be transported by road, where well developed roads exist & the route conditions permit.

2] Selection of Trailer

Multi axle tractor driven low platform trailers are used for road transport. The tractors are to have adequate hauling capacity and the trailers should have adequate loading capacity. There are two types of trailers available.



i) Low bed Mechanical Articulated Trailer



This is useful for concentrated load like Transformer. The maximum Gross load permissible in Mechanical Articulated trailer is 49 MT (Gross load = Weight of consignment + weight of trailer + weight of pulling unit, tractor)

ii) Hydraulic axle Trailer

Useful for all types of loads including transformers. The maximum Gross load permissible in Hydraulic axle trailer is 18 MT Per axle. Depending upon the weight, the number of axles can be attached one after another. Normally Hydraulic axle unit are available in the combination as a unit of 2 axle, 3 axle, 4 axle, 6 axle and 8 axle (weight of each axle is approx.: 3.5 to 4.5 MT) depending upon Manufacturer. The axle width is generally 3 Mtrs. 1 ½ side axle can also be joined if the width of the consignment is exceeding 4 Mtrs. Total width of the axle in this case will be 4.5 Mtrs.

POWER TRANSFORMER - STANDARDISATION MANUAL

3] Capacity of Puller

Presently Pullers (figure 5.1) are available to pull loads from 1 to 240 MT.

Fig. 5.1

4] No. of Axles

No. of hydraulic axles of any transportable consignment can be determined in the following manner. One puller carried load of the consignment on two hydraulic axles.



Weight of tractor (ra) + trailer (rb)

= X (say, 10 MT)



Weight of Transformer

: (a) e.g. 70 MT



Gross weight permissible per axle

: (b) e.g. 18 MT



Weight of each axle

: (c) e.g. 4.5 MT (standard weight)



Weight of Goods that can be loaded (d)

: (b-c) = (18 MT – 4.5 MT) = 13.5



Hence, for 70 MT Transformer axles to deploy = {X+(a)}/(d) = {10+70}/13.5 = 5.92



Therefore number of axles which need to be deployed are 6.



In the up gradient of hills or roads extra puller of same rating shall be provided.



In down gradient of ghat section use power brake attached to the hydraulic modular trailer.

5] Route Survey

The route Survey Report is for safe and speedy transport of over dimensional / sophisticated consignments by deployment of well suitable equipment, driver and escorts (both) with professional & technical expertise and their rich experience is the answer of safe and speedy transport.



Based on the dimension and weight of the consignment extensive study is being carried out, first calligraphically wherein most feasible routes for the transportation to the destination site is selected and there after exhaustive field verification are carried out. After collection and compilation of massive data that was collected during the route surveys, only the most feasible route is being selected and detailed report of Survey is being prepared. Efforts to be made for best alternative solution while highlighting the problems that are anticipated for safe and speedy transportation of over dimension / sophisticated consignment

187

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POWER TRANSFORMER - STANDARDISATION MANUAL



a) Elements of route survey



The road system is examined in detail on the following points: i.

Normally width of the road should be more than 5 m.

ii. Bridges and culverts should have sufficient strength to take the moving load (in this regard, consultation with highway department is necessary) iii. Hindrance on route like telephone, telegraph, traction and HT/LT wires, avenue trees, sub ways etc are to be assessed. iv. Sharp bends & road worthiness (i.e. sandy stretches, waterlogged areas, crowded localities like market places, schools and public places)

6] Speed

For the normal running uniform speed of 10 to 20 kmph shall be maintained on good roads. For bad roads it is desirable to run the vehicle at much lower speeds. However, while crossing bridge it shall be 5 kmph. No breaks should be applied during bridge cross over. Movement of other vehicle should be stopped while crossing bridge. Long before the approach to the bridge, the speed should be brought down and the vehicle allowed proceeding over the bridge without creating any impact.



The brake system on the tractor-trailer has to be carefully operated whenever the vehicle is running with load.

7] Night Travel & Halt

Normally night travel is avoided except where it is restricted for heavy vehicles to travel in day time i.e. cities, towns & small villages. Transportation should be avoided during heavy rains also. In the case of night halt or stoppage of the loaded trailer for a fairly long duration the trailer should be supported either by sleepers or providing supporting jacks on all sides thus releasing the load from the tyres. Danger lights should be displayed in the front and rear of the vehicle.

8] Safe movement under O/H lines

The Supervisor should ensure that sufficient line clearance from line conductor to the top most part of transformer and trailer is available as per IE Rules and as per the rating of transmission lines. The transportation during monsoon period should be avoided as far as possible if sufficient clearances are not available. If it is found that the clearances are critical, the hydraulic axle platform can be lowered by 250 to 300 MM as per the provision made in hydraulic axle to avoid any danger of electrical faults.

9] Special spares / tools to be carried during transport 1.

Insulated LT wire lifting device

2.

Extra tyres

3.

Hydraulic Jacks

4.

Tools Box

5.

Crow bar

6. Tarpaulin 7.

Slings for fastening

8. First Aid kit 9.

Small Spares

10. Torch 11. Baton sticks 12. Red & Green Flags

POWER TRANSFORMER - STANDARDISATION MANUAL

10] Crew Size 1.

Supervisor

- 1 Person

2.

Driver

- 1 Person

3.

Axle operator

- 1 Person

4.

Helpers

- 3 Persons

5.

Wire lifting

- 3 / 4 Persons.

All above should be equipped with helmet, safety shoes & hand gloves and Supervisor, Axle operator and Driver are with suitable communication facility.

11] Document verification for puller capacity

Registration book issued by RTO department to know the horse power of puller.

12] Movement

A pilot vehicle with all tools and tackles, jacks, sleepers, chequered plates, crowbars, etc., and sufficient trained staff should run in front of the vehicle. Red flags and danger lamps should be exhibited at prominent places to warn traffic on the route.



The branches of avenue trees that are likely to foul the equipment should be cleared while the load is moved. Electric utility power lines likely to foul should be switched off and lifted temporarily / dismantled while the load is moved.



After moving the load for a short distance, tightness of the lashing should be checked.

13] Check Points during Transportation a)

Provide suitable impact recorder which give waveform data and frequency analysis. As per IEEE guide line PC57.150, it is recommended to provide two recorders per transformer to eliminate chances of loss of data due to failure of recorder.

b)

Place both the recorders as low as possible and in diagonally opposite positions for best results.

c)

Check pressure of dry air or nitrogen as shown below on daily basis. Any loss in pressure shall be made up. For this, Transformer shall be supplied with filled gas cylinder to maintain positive pressure during transportation (figure 5.2).

d)

The purity shall be 99.9% for nitrogen gas or dry air conforming to DIN 3188.

e)

Weak bridges, if any should be strengthened with the help of highway department.

f)

Red flags and danger lamps should be exhibited on the unit.

g)

Check tightness of lashing at regular intervals during movement.

Fig. 5.2:

189

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POWER TRANSFORMER - STANDARDISATION MANUAL

14] Receipt of Transformer at Site i.

When a transformer arrives at site a careful external inspection must be made of the unit, its cooling system and all sealed components, referring to the general arrangement drawing and the shipping list.

ii.

Inspect all packing cases and loose components for damage or missing items.

iii. Check whether the transformer has arrived at site with a positive gas pressure in case of dispatch without oil. In case of dispatch of main body in oil filled condition, check oil level and leakages if any. iv. Should the transformer arrive at site without pressure (owing to gas leakage), it must be assumed that moisture has entered the tank and that the moisture will have to be driven out. In such cases, the manufacturer’s advice must be sought. v.

In case of any oil leakage or damage is discovered, the transportation company, the transport insurer and manufacturer shall be informed immediately.

vi. A record of damage must be prepared in conjunction with other participants and supplier representative. Minor damage which may appear unimportant should also be recorded. vii. Confirm that case numbers match with the packing list. Check their contents tally with the packing list if the packing case is damaged. viii. Fill in the check list for external as well as internal inspections. ix. For oil filled transformers a sample of oil should be taken from the bottom of the tank and tested for BDV and moisture content. If the values do not meet the relevant standards the matter should be taken up with the manufacturer. x.

Down load impacts recorded by impact recorder and analyze the same in consultation with supplier.

15] Unloading of Transformer

All the transformer unloading and handling work should be carried out and supervised by specialized people, following all safety rules and using supporting points indicated on drawing. The use of any other points will result in severe damages to the transformer. a)



The following should be avoided during the unloading process §§

The transformer imbalance (Maximum 10 degree)

§§

Abrupt movements

§§

Impact against the ground

§§

Side Impact

The transformer should be unloaded from trailer by using wooden sleepers and rails for dragging the transformer to its plinth. b)

c)

Considerations before unloading §§

Availability of access road between unloading point and plinth.

§§

Ensure overhead crane capacity for weight of main unit.

§§

Readiness of foundation

§§

Keep under base of main unit at least 300 – 400 mm above ground level by providing wooden slippers to facilitate jacking.

§§

Remove lashing before unloading.

Unloading from Trailer i.

Unload main unit only on wooden slippers

ii.

Jack the transformer at jacking pad only.

iii. Ensure simultaneous operation of all 4 jacks. iv. Use only haulage lugs for hauling. v.

Ensure capacity of winches and wire ropes to be used for haulage.

vi. Do not use chain pulley block in place of winches.

POWER TRANSFORMER - STANDARDISATION MANUAL

d)

After checking of exact position of transformer, the following sequence should be followed i

Install all wheels to transformer using hydraulic jacks sized for at least 50% of the units weight.

ii

Before resting the wheels into groove, make sure all of them properly adjusted.

iii

Lower the transformer with the help of the hydraulic jacks until it remains resting on the bottom of the groove. Never allow the transformer to remain inclined.

Fig. 5.3:

e)

List of major tools for unloading Sr. No.

Item

Capacity

1

Mobile crane

Min. 110% of weight of transformer

2

Hydraulic Jack

1.5 times weight of transformer

3

Lifting slings

Size of slings to be selected according to weight and angle of lifting

4

Winch machine

115% of weight of transformer divided by 4

5

Wooden sleepers

300 to 400 mm thick

6

Greased steel plates

Adequate numbers

7

Pulleys

115% of weight of transformer divided by 2

8

Oil storage tank

25 kL with motor pump.

9

Oil filter machine /oil purifier

5000 lph

10

Vacuum pump

760 mm of Hg

11

Water proof tarpaulins

30 to 40 M2

12

Flexible hoses for vacuum and oil

10 M long – 4 nos 3 M long – 2 nos

13

Oil test kit

– 100 kV

ERECTION, TESTING AND COMMISSIONING The complete process of erection from point of dispatch from factory to commissioning is illustrated in the form of flow diagram to follow sequence of activities scrupulously with check points. 1

Erection



Erection of power transformer requires great deal of planning and arrangement of resources. It is essential to have erection agency with skilled manpower having experience of EHV class power transformer. Each and every

191

192

POWER TRANSFORMER - STANDARDISATION MANUAL

unit is to be treated like a project, so that cost, quality and time are controlled and monitored through a process (Flow chart - see Fig. 5.4). It will ensure that erection activities are carried uninterrupted with safety and without any damage to transformer parts / items. It is suggested to have kick off meeting (KoM) with following main agenda: 1.

Competency of erection agency and their manpower skills.

2.

To confirm receipt of transformer as per BOQ in full shape

3.

To confirm availability of T&P as per requirement of unit, size and rating. (Refer list as per this manual)

4.

To confirm readiness of plinth and radiator foundation as per requirement (Physical check of dimensions)

5.

To confirm over head conductor take off or power cable terminations arrangement as the case may be.

6.

To confirm safety measures adopted and location hazards, if any.

7.

Organization reporting structure, data recording, responsibility and clearances.

8. To confirm insurance, workmen compensation and labor related statutory requirements. 9. 2

Comply to specific requirements agreed in Design Review.

Minimum Tools & Plants and Other Items a)

General T&P The following tools and plants can be arranged during erection, overhauling activity at site. Sr. No.

Item

Optimum Quantity Recommended

1

Spanners : a) Double end (size -32) b) Ring (size -32) c) Box/socket type (size 6-36) with a/2” drive complete with ratchet, universal, ordinary handle and extension bar of size 75mm and 150mm

2 Set 2 Set 2 Set

2

Single end spanners (36,41,46,50,55)

5 Nos.

3

Slugging wrench (32,36,41)

3 Nos.

4

Tubular spanner (size 6-32)

1 Set.

5

Torque wrench (1/2” drive) 5 to 22 kgm

1 No.

6

Adjustable spanner 8” - do 12” - do 18” - do 24”

2 Nos. 2 Nos. 1 No. 1 No.

7

Pipe wrench 12” - do - 18” - do - 24”

1 No. 1 No. 1 No.

8

Spanner for opening transformer butterfly valves (squre)

9

Spanner for opening oil drum

2 Nos.

10

Screw Driver a) 10mm (D0 x 400mm (L) b) 10mm (D0 x 300mm (L) c) 8mm x 300mm (L) d) 8mm x 200mm (L) e) 6mm x 250mm (L) Insulated f) 6mm x 200mm (L) Insulated

2 2 4 4 4 4

1 No. for each type of valve

POWER TRANSFORMER - STANDARDISATION MANUAL

193

194

POWER TRANSFORMER - STANDARDISATION MANUAL

Sr. No.

Item

Optimum Quantity Recommended

11

Star screw driver (size 1mm to 6mm)

1 Set.

12

Nut driver stet (up to 10 mm)

1 Set.

13

Allen Keys (size 1 mm to 16mm)

1 Set.

14

Cutting pliers insulated - 8” 10”

2 Nos. 2 Nos.

15

Nose pliers insulated - 6” 8” 10”

2 Nos. 2 Nos. 2 Nos.

16

Cir-clip pliers – Internal External

1 No. 1 No.

17

Wire stripper for 2.5 sq. mm

2 Nos.

18

Hammer - ½ kg 2 kg 5 kg

1 No. 1 No. 1 No.

19

a) Teflon mallet (medium size) b) Wooden mallet (medium size)

1 No. 1 No.

20

a) Dot punch b) Hole punch kit up to 32mm

1 No. 1 Set

21

Brass rod (300mm L x 20mm D)

1 No.

22

Files. a) Needle file b) Flat file 12” (rough & smooth) each one c) Half round 8” d) -do- 10” e) Round file 8” f) -do- 10” g) Triangular file 8” (rough & smooth) each one

1 Set 2 Nos. 1 No. 1 No. 1 No. 1 No. 2 Nos.

23

a) Hacksaw frame - 12” b) Wood saw - 12”

1 No. 1 No.

24

Sheet cutter

1 No.

25

Scissors - 8”

1 no.

26

Flat Chisel - 8” Round Chisel - 10”

1 No. 1 No.

27

Industrial knife high carbon sheet

1 No.

28

Knife for wire cutting

2 Nos.

29

Measuring tape a) 3 meter (flexi-measure) b) 15 meter (plastic) c) 30 meter (plastic)

2 Nos. 1 No. 1 No.

- 12“

30

Steel rule – 30 mm

1 no.

31

Varnier Caliper - 300mm

1 No.

32

Filler gauge - 100mm - 24 blade (metric)

1 No.

33

Tri square 10”

1 No.

POWER TRANSFORMER - STANDARDISATION MANUAL

Sr. No.

Item

34

Plumb

1 No.

35

Sprit level

1 No.

36

Bench vice - 8”

1 No.

37

Pipe vice for pipe up to - 2”

1 No.

38

Pipe die set up to -2”

1 Set.

39

Crimping tool a) Hand operated up to 16 sq. mm b) Hydraulic

1 No. 1 No.

40

Bearing puller - 3 leg (size 300mm)

1 No.

41

Hand operated oil can

1 No.

42

Grease gun ( medium size)

1 No.

43

Hand operated oil pump (for oil drums)

1 No.

44

Drilling machine portable (0-13mm) Model WD 34C, Make : Wolf

1 No.

45

Drilling machine heavy duty along with drill chuck, sleeves and arbor Model NW 10, Make : Wolf

1 No.

46

Drill bits : a) size upto 10mm straight shank b) size 12 to 25mm tapper shank

47

Hand Grinder (AG-7) Make : Wolf

48

Bench Grinder, Model TG6-E wheel dia. 150mm

1 No.

49

Vacuum cleaner cum blower with hot air attachment

1 Set

50

Hydraulic jacks (100 t. capacity)

4 Nos.

51

Pulling and lifting machine (Tirfor 5 t. capacity)

2 Nos.

52

Chain pulley block a) 10 T b)1 T

1 No. 1 No.

53

C-clamps (12”)

6 Nos.

54

D Shackle a) 2 T capacity b) 5 T capacity c) 10 T d) 20 T

6 Nos. 4 Nos. 4 Nos. 4 Nos.

55

Bull dog clamp heavy duty suitable for 10mm, 12mm wire sling

56

Single sheave pulley (a) 1.5 ton (12 mm) (b) 2.5 ton (12 mm)

57

Slings. (a) 12mm dia. with standard loop on both ends having 6 mtr. length (b) 12mm dia. with standard loop on both ends having 10 mtr. length (c) 10mm wire rope length (d) 32mm dia. with standard loop on both ends having 10 mtr. length (e) Wire rope slings double legged with ring at one end and hook at other end with 12mm roper of 4 mtr. length

Optimum Quantity Recommended

10 Nos. 13 Nos.

5 Nos. each 1 No. 1 No. 4 Nos. 2 Nos. 100 mtr 2 Nos. 2 Nos.

195

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POWER TRANSFORMER - STANDARDISATION MANUAL

b)

Sr. No.

Item

58

Polypropylene rope a) 6 mm b) 12 mm c) 16 mm

Optimum Quantity Recommended 50 mtr 100 mtr 100 mtr

59

Welding machine with flexible welding cable, insulated electrode holder, protective masc., chisel, chipping hammer, wire brush and leather gloves (model RED-301 of Advani oerlicon Ltd)

1 Set.

60

Brazing, soldering and gas cutting kit

1 Set.

61

Pipe GI or Iron – 25mm and 40mm 50mm dia (1 mtr length each)

3 Nos.

Miscellaneous Items Sr. No.

Item

1

Torch light (large size)

2 Nos.

2

Emergency light

5 Nos.

3

Flood lights fittings : - Sodium vapor (70 W) - Halogen (500 W)

5 Nos. 5 Nos.

4

Tarpaulins (large size)

10 Nos.

5

Ladder (Aluminum) (a) Self supporting ladder 1.8 mtr (b) -do3.6 mtr (c) extension ladder 4.8 mtr

2 Nos. 1 No. 2 Nos.

7

Heaters (2.0 kW x 40 Nos.)

2 Sets.

8

Wooden sleepers

50 Nos.

9

U-clamp for connecting OLTC chamber to main tank at the time of vacuum pulling

10

Oil sampling bottle

10 Nos.

11

Oil sample flange

2 Nos.

12

Switch boards for extending supply having 15A/5Amp socket, bulb, holder & switch

3 Nos.

13

Earth rods

5 Nos.

14

Fire extinguisher CO2 (22.5kg) Foam ( 9kg) Halon (3 kg)

2 Nos. 2 Nos. 2 Nos.

Dry air cylinders

30 Nos.

15

Optimum quantity recommended

1 No.

POWER TRANSFORMER - STANDARDISATION MANUAL

c)

3

Special T&P and Instruments Sr. No.

ITEM

Quantity.

1

Filter machine 6000 L

1 No.

2

Oil tanks (30 KL capacity)

1 No.

3

Oil hose

4

Vacuum pump

1

5

Vacuum hose

20 mtr

7

400A switch board for power supply to Filter machine

2 Nos.

8

BDV kit

1 No.

9

5KV/10KV megger

1 No.

10

Tan delta & capacitance kit

1 Set.

11

SFRA kit

1 Set.

12

Ratio meter

1 No.

13

Winding resistance measurement meter with leads

1 No.

14

Multi meter

3 Nos.

15

Clip on meter

1 No.

16

Primary injection kit with leads

1 Set.

17

Variac for 3-phase supply (15 Amp)

1 No.

18

Online PPM Meter

1 No.

19

Dew Point Meter

1 No.

20

Pressure Gauge

2 Nos.

21

Vacuum Gauge

2 Nos.

22

Mobile Crane Hydra

1 No.

100 mtr.

Safety Measures & Precautions 1.

Keep recommended fire extinguishers at site.

2.

During hot oil circulation, keep fire extinguisher ready near transformer.

3. Carry out all pre-commissioning Test and final commissioning check as elaborated in this Manual before energizing transformer. 4. Take precaution while handling PRV devices having heavy springs in compression to safeguard person and system. 5.

Replace N2 filled tank by breathable dry air of dew point less than (-40 oC) at least for 24 hours.

6.

Provide adequately rated cables & fuses.

7.

Never apply voltage when transformer is under vacuum.

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POWER TRANSFORMER - STANDARDISATION MANUAL

8. Oil spillage shall be inspected regularly and attended if any. Oil shall not be allowed to fall on ground. 9.

Keep all combustible items away at safe distance to reduce risk of fire.

10. Welding on oil filled transformer may be avoided or done as per instruction of manufacturer only. 11. All erection personnel must use Personal Protective Equipments like, helmet, safety shoe, boiler suit, etc. 12. No welding work shall be taken up near transformer. 13. Electrical equipment like filter machine, dry air generator etc., must be earthed. 14. First Aid box shall be kept ready at site. 15. Adequate lighting must be available for clear visibility 16. Cordon off the working area, particularly when transformer augmentation work in a switchyard is taken up. 17. All major erection activity like bushing, conservator and radiators must be carried out with crane of adequate capacity and boom size. 18. Never carry out work with unskilled workers. 19. Safety posters, like “No Smoking”, “Wear Helmet”, etc., must be displayed. 20. Testing circuit and procedures are important to follow as per manual to avoid any induction effect before and after the Test. Approved and tested Earth rods are essential for this purpose. 21. Safety Nodal Officer to make sure that site is cleared on daily basis to prevent fire hazards.

4

Precomissioning Tests:

4.1 Preparation for SAT (Site Acceptance Tests) §§

Site study

§§

Collection of Factory Acceptance Test reports

§§

Finalization of action plan for carrying out SAT

§§

Prepare testing program schedule.

§§

Check whether the transformer under Test had been isolated from other electrical equipments and from induction using earth switch or local earthing arrangement.

§§

Make the Test procedure

§§

Make the Test formats

§§

Get the guidance of Dos and Don’ts from the experts in the field

§§

Ensure for all safety assessments of Helmets, Gloves and Safety shoes.

§§

Execute the tests according to the program schedule.

§§

Compile the Test reports.

§§

Do analysis of the Test results and ensure for healthiness of transformer.

POWER TRANSFORMER - STANDARDISATION MANUAL

4.2 Following checks should be carried out before commencing the pre-commissioning Test of the Power Transformer. §§

Ensure that Power Transformer and its auxiliaries should be free from visible defects on physical inspection

§§

Ensure that all fittings should be as per out line General Arrangement Drawing

§§

Ensure that bushings should be clean and free from physical damages

§§

Ensure that oil level is correct in all bushings

§§

Ensure that oil level in Main / OLTC Conservator tank in MOG is as desired.

§§

Ensure gear box oil level in OLTC

§§

Ensure that OTI and WTI pockets are filled with transformer oil

§§

Ensure that cap in the tan delta measurement point in the bushing is grounded

§§

Ensure unused secondary cores of Bushing CT’s, if any, has been shorted

§§

Ensure CT secondary star point has been formed properly and grounded at one end only as per scheme

§§

Ensure that Buchholz Relay is correctly mounted with arrow pointing towards conservator

§§

Ensure all power and control cable terminals are tightened

§§

Ensure all cables and ferrules are provided with number as per cable schedule

§§

Ensure that external cabling from junction box to relay / control panel is completed

§§

Ensure operation of OLTC manually, electrically at local and electrically by RTCC

§§

Ensure indication of tap position on Diverter switch, Drive mechanism & RTCC are same.

§§

Ensure working of numerical AVR

4.3 List of Site Acceptance Tests

Following pre-commissioning Tests / checks should be carried out: Sr. No

Test / Checks Name

Testing Equipments

1

SFRA Test

Automatic SFRA kit

2

Capacitance and Tan delta measurement Test

Automatic Capacitance & Tan delta measurement kit

3

Transformer turns ratio Test

Digital Ratio meter

4

Magnetizing current Test

Digital multi meter

5

Magnetic balance Test

Digital multi meter

6

Verification of vector group and polarity test

Digital multi meter

7

Short circuit impedance test

Digital multi meter

8

Measurement of winding resistance test

Digital winding resistance meter

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POWER TRANSFORMER - STANDARDISATION MANUAL

Sr. No

Test / Checks Name

Testing Equipments

9

Winding Insulation Resistance measurement

Digital insulation resistance meter

10

Core Insulation Resistance measurement

Digital insulation resistance meter

11

Oil characteristic test

Oil BDV test kit

12

Tests on bushing CT s

Digital multi meter, CT primary current injection kit, Knee point voltage measurement kit, Insulation resistance tester

13

Operational tests and checks on other equipments

--

14

Measurement of earthing pit resistance

Earth resistance measurement kit

15

Protection and alarms

As per scheme

16

Contact resistance measurement

Contact resistance measurement kit

17

Clearances

Measurement tape/ Automatic Infra red gun

18

Protection relay settings

As per scheme

19

Final documentation review

As per requirement

4.3.1 SFRA Test

(a) Purpose of the test



The transformer is considered to be a complex network of RLC components. The contribution to this complex mesh of RLC circuit are from the resistance of the copper winding, inductance of the winding coils and capacitance from the insulation layers between coils, between winding, between winding and core, between core and tank, between tank and winding etc. (figure 5.5).

(b) Principle of the test

Any form of physical damage to the transformer results in the changes of the RLC network. These changes are looking for and employ frequency response to highlight these small changes in the RLC within the transformer.

Fig. 5.5:

POWER TRANSFORMER - STANDARDISATION MANUAL





The test involves measuring the frequency response of each individual winding. The frequency is measured by injecting a sine wave signal with respect to earth at one end of winding to be tested and measuring the signal amplitude there and at other end of winding. The attenuation (in db) of the transmitted signal relative to reference signal at the input terminal is measured over a frequency range from 20 Hz to 2 MHz. SFRA is used to check the eventual change in the internal geometry of the active part of the transformer whether displacement of deformation i.e. the mechanical integrity of the transformer.



Transformers while experiencing severity of short circuit current looses its mechanical property by way of deformation of the winding or core. During pre-commissioning, this test is required to ascertain that Transformer active part has not suffered any severe impact/ jerk during transportation.

(c) Equipments for the test



Automatic SFRA test kit with application software

(d) Circuit for the test (figure 5.6)

SFRA Kit

Fig. 5.6:



(e) Procedure for the test §§

This test is carried out after completion of all commissioning activities.

§§

Factory FRA test report in soft form should be available at site.

§§

FRA signatures will be taken after assembly and oil filling and compared with factory testing to ensure the healthiness of core /coil assembly during transportation.

§§

Interpretation of test results carried out

§§

Test results matching with the factory results

§§

10 V AC is applied at variable frequency (20Hz to 2 MHz) to the winding for all possible connections of the winding

§§

These signatures will be the benchmark for future reference.

§§

The FRA signatures should be analyzed in conjunction with Impact Recorder readings.

§§

Report of Impact recorder readings is to be obtained from manufacturer.

§§

It is recommended to follow the standard procedure for the SFRA measurement as per the standard test procedure recommended by the manufacturer.

§§

It should be done on maximum, normal and minimum tap of the transformer.

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POWER TRANSFORMER - STANDARDISATION MANUAL



Type of connections for the test (figure 5.7) and typical waveform (figure 5.8). A. HV Phase to Neutral with LV open

Fig. 5.7:

Fig. 5.8:

1. Feed the frequency signal from 20 Hz -2 MHz in the transformer R ph of the HV winding with respect to the neutral (for star winding) and R ph of HV winding with Y ph of HV winding (for delta winding). 2.

Both the reference leads should be earthed properly.

3.

Keep LV open ( including core)

4.

Kit will receive the response of the impedance characteristic in the transformer.

5.

Response will be plotted in logarithmic scaled graph.

6.

Repeat the all procedures for other phases

B. HV Phase to Neutral with LV shorted (Connection see figure 5.9 and typical waveform figure 5.10) 1. Feed the frequency signal from 20 Hz -2 MHz in the transformer R ph of the HV winding with respect to the neutral (for star winding) and R ph of HV winding with Y ph of HV winding (for delta winding). 2.

Both the reference leads should be earthed properly.

POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 5.9:

Fig. 5.10:



3.

Keep LV winding shorted (core is avoided)

4.

Kit will receive the response of the impedance characteristic in the transformer.

5.

Response will be plotted in logarithmic scaled graph.

6.

Repeat all the procedures for other phases

C. LV Phase to Neutral with HV open (Connection see figure 5.11 and typical waveform figure 5.12) 1. Feed the frequency signal from 20 Hz -2 MHz in the transformer R ph of the LV winding with respect to the neutral (for star winding) and R ph of HV winding with Y ph of LV winding (for delta winding). 2.

Both the reference leads should be earthed properly.

3.

Keep LV winding open

4.

Kit will receive the response of the impedance characteristic in the transformer.

5.

Response will be plotted in logarithmic scaled graph.

6.

Repeat all the procedures for other phases

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POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 5.11:

Fig. 5.12:

D. Between HV and LV winding (Connection see figure 5.13 and typical waveform figure 5.14)

Fig. 5.13:

POWER TRANSFORMER - STANDARDISATION MANUAL

Fig. 5.14:

1. Feed the frequency signal from 20 Hz -2 MHz in the transformer R ph of the HV winding with respect to the LV winding 2. Both the reference leads should be earthed properly. 3. Keep LV winding open 4. Kit will receive the response of the impedance characteristic in the transformer. 5. Response will be plotted in logarithmic scaled graph. 6. Repeat all the procedures for other phases Maximum possible combinations of connections for SFRA test Test Type Series winding (OC) All other terminals floating

Common winding (OC) All other terminals floating

Tertiary winding (OC) All other terminals floating

Short circuit (SC) High (H) to Low (L) Short (X1-X2-X3)

Short circuit (SC) High(H) to tertiary (Y) Short (Y1-Y2-Y3)

Short circuit (SC) Low(L) to tertiary (Y) Short (Y1-Y2-Y3)

Test

3 phase

1 phase

Test 1

H1-X1

H1-X1

Test 2

H2-X2

Test 3

H3-X3

Test 4

X1-H0X0

Test 5

X2-H0X0

Test 6

X3-H0X0

Test 7

Y1-Y3

Test 8

Y2-Y1

Test 9

Y3-Y2

Test 10

H1-H0X0

Test 11

H2-H0X0

Test 12

H3-H0X0

Test 13

H1-H0X0

Test 14

H2-H0X0

Test 15

H3-H0X0

Test 16

X1-H0X0

Test 17

X2-H0X0

Test 18

X3-H0X0

X1-H0X0

Y1-Y2 (Y1-Y0)

H1-H0X0 Short (X1-H0X0)

H1-H0X0 Short (Y1-Y2)

X1-H0X0 Short (Y1-Y2)

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POWER TRANSFORMER - STANDARDISATION MANUAL

e)

Acceptance Criteria Test results should match with the factory results (In general changes of +/- 3dB) If changes are more than limit, it may indicate following faults:

f)

Frequency Range

Probable Fault

5 Hz to 2 KHz

Shorted turns, open circuit, residual magnetism or core movement

50 Hz to 20 KHz

Bulk movement of winding relative to each other

500 Hz to 2 MHz

Deformation within a winding

5 Hz to 10 MHz

Problem with winding leads and/or test lead problem

Format for the test report Equipment Detail: Make

Type

Sr. No.

Range

Cal. Due Date

Close

 

 

 

 

1.1 Low frequency region (20 Hz<1 kHz) HV-N side Tap position

Resonance value in dB (Site)  1U-1N

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

 1V-1N

 1W-1N

Resonance value in dB(Factory) 1U-1N

 1V-1N

 1W-1N

Remarks  

POWER TRANSFORMER - STANDARDISATION MANUAL

IV-N side Tap position

Resonance value in dB (Site)

Resonance value in dB(Factory)

 2U-2N

2U-2N

 2V-2N

 2W-2N

 2V-2N

 2W-2N

Remarks  

Normal

LV side Tap position

Resonance value in dB (Site)

Resonance value in dB (Factory)

 3U-3V

 3U-3V

 3V-3W

 3W-3U

 3V-3W

 3W-3U

Remarks  

Normal

1.2 Medium frequency region (>1 kHz - 100 kHz) HV-N side Tap position

Resonance value in dB (Site)  1U-1N

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

 1V-1N

 1W-1N

Resonance value in dB (Factory) 1U-1N

 1V-1N

 1W-1N

Remarks  

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POWER TRANSFORMER - STANDARDISATION MANUAL

IV-N side Tap position

Resonance value in dB (Site)

Resonance value in dB (Factory)

 2U-2N

2U-2N

 2V-2N

 2W-2N

 2V-2N

 2W-2N

Remarks  

Normal

LV side Tap position

Resonance value in dB (Site)

Resonance value in dB (Factory)

 3U-3V

 3U-3V

 3V-3W

 3W-3U

 3V-3W

 3W-3U

Remarks  

Normal

1.3 High frequency region (>101 kHz – 2MHz) HV-N side Tap position

Resonance value in dB (Site)  1U-1N

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

 1V-1N

 1W-1N

Resonance value in dB (Factory) 1U-1N

 1V-1N

 1W-1N

Remarks  

POWER TRANSFORMER - STANDARDISATION MANUAL

IV-N side Tap position

Resonance value in dB (Site)

Resonance value in dB (Factory)

 2U-2N

2U-2N

 2V-2N

 2W-2N

 2V-2N

 2W-2N

Remarks  

Normal

LV side Tap position

Resonance value in dB (Site)

Resonance value in dB (Factory)

 3U-3V

 3U-3V

 3V-3W

 3W-3U

 3V-3W

 3W-3U

Remarks  

Normal

4.3.2 Capacitance and Tan Delta Measurement Test a)

Purpose of the test



Dissipation factor / loss factor/ Tan delta is defined as the ratio of resistive components to that of capacitive current flowing in an insulating material. Dissipation factor (tan delta) and capacitance measurement of bushing/winding provides an indication of the quality and soundness of the insulation in the bushing/winding.



Changes in the normal capacitance of an insulator indicate abnormal conditions such as the presence of moisture layer, short -circuits or open circuits in the capacitance network.

b)

Principle of the test



The capacitance and dissipation/loss factor (Tan δ / Cos φ) measurement are made to determine the insulating condition of the transformer’s both winding to earth and between the windings, and to form a reference for future measurements during operating the transformer.



There is a small amount of insulating loss in all insulators used in transformer applications at normal operating voltage and frequency. In appropriate insulators, this loss is very small. This loss changes in direct proportion with the “square “of the applied voltage. The insulator and equivalent diagrams are given in figure 5.15.

a)

b)

c)

Fig. 5.15:



As seen in figure, the angle delta ’between the total current “Ir” and capacitive current “IC” allows to make evaluation about the loss properties of the insulator.



The loss angle delta, depends heavily on the thick ness of the insulating material and surface condition, structural property of the insulator, type of the material, (humidity, foreign materials/ particles, air gaps, etc. which cause ionization the insulating material).

209

210

POWER TRANSFORMER - STANDARDISATION MANUAL



The conditions which increase the power losses of the insulator also decrease the insulation strength. For this reason, loss angle measurement is a very valuable criterion for evaluating the insulation material at a defined operating frequency. Periodical measurements made during operating are also important to show the general condition of the insulating material. In this way, it is possible to gather information about aging of the solid insulating materials and degradation of the oil.



The active loss of the measurement circuit can be calculated according to below equation:



P= U. I. Cos delta = U 2. C. ω. tan delta



(It is accepted that in very small angles, Cos delta will be equal to tan delta)



Capacitance, tan delta, active loss and Cos delta can be measured by bridge methods at defined voltages or by a “power factor” (Cos delta) measuring instrument.



The measurement is made between windings and between the windings and the tank. During the test, the temperature of the transformer should also be recorded and corrected in accordance with the reference temperature.



The loss factor depends heavily on temperature. For this reason, in order to make comparisons later, it has to be converted to reference temperature (for example 20 deg reference temperature) by a coefficient.



Correction equation:



F20 = Ft / K



F20: loss factor at 20 oC temperature



Ft: loss factor value at t measuring temperature



K: correction factor is given in the table



Correction factor for transformer with mineral oil: Measurement temperature Deg. C

Correction factor K

10

0.8

15

0.9

20

1

25

1.12

30

1.25

35

1.4

40

1.55

45

1.75

50

1.95

55

2.18

60

2.42

65

2.70

70

3.0

POWER TRANSFORMER - STANDARDISATION MANUAL

c)

Equipment for the test:



10 KV or 12 KV fully automatic Capacitance and Tan delta test kit to be used for accurate measurement and repeatability of test results

4.3.2.1 Transformer winding insulation tests a)

Procedure for the test 1.

In a two winding transformer, there are three measurements of capacitance



i.

HV to ground



ii.

LV to ground



iii.

HV to LV

2. These values of capacitance and their respective values of insulation factor (tan delta) are to be measured. 3.

All HV line terminals connected together and labeled (H); all LV line terminals connected together and labeled (L); and a connection to a ground terminal, usually connected to transformer tank labeled (G).

4. Leads from the instrument or bridge are connected to one or both terminals and ground. 5. Either grounded specimen measurement of guarded measurements are possible, so that all capacitance values and dissipation factor values can be determined. 6. b)

These measurements are usually made at voltage of 10 kV or less, at power frequency.

Connection diagram

Fig. 5.16:



For tan delta of bushings, connections are to be carried out in UST mode.



For tan delta between windings, connections are to be carried out in UST mode.



For tan delta of windings with earth, connections are to be carried out in GST mode.

(i) HV winding measurement 1. Short all the three phases of HV winding and make the zero sequence impedance. In other words, make the current flow only in capacitance region (Omit inductance) in the impedance network of the transformer.

211

212

POWER TRANSFORMER - STANDARDISATION MANUAL

2. Make HV cable connection at HV terminals and LV cable at neutral (ground should be isolated). If it is delta connection then LV cable connection to be made in next phase. 3.

Select the test mode GST-G for capacitance measurement in between windings and GST-YG for capacitance measurement in between windings.

3.

Apply 10 kV voltage in the stepwise manner and cross check the values in all step voltages.

4. Note the measurement values of applied voltage, leakage current, power factor and dissipation factor, capacitance, humidity and ambient temperature.

Fig. 5.17:



(ii)

HV-LV connection

Fig. 5.18:

1. Short all the three phases of HV and LV winding and make the zero sequence impedance. In other words, make the current flow only in capacitance region (Omit inductance) in the impedance network of the transformer. 2.

Make HV cable connection at HV terminals and LV cable at LV terminals.

POWER TRANSFORMER - STANDARDISATION MANUAL

3.

Select the test mode UST-YG for capacitance measurement in between tank and winding.

4.

Apply 10 kV voltage in the stepwise manner and cross check the values in all step voltages.

5.

Connections of the leads to be carried out as per diagram.

6. Note the measurement values of applied voltage, leakage current, power factor and dissipation factor, capacitance, humidity and ambient temperature.

(iii) LV- Earth connection

Fig. 5.19:

1. Short all the three phases of LV winding and make the zero sequence impedance. In other words, make the current flow only in capacitance region (Omit inductance) in the impedance network of the transformer. 2.

Make HV cable connection at LV terminals and LV cable at Neutral terminals. (Ground should be isolated). If it is delta connection then LV cable connection to be made in next phase.

3.

Select the test mode GST-G for capacitance measurement in between windings and GST-YG for capacitance measurement in between windings.

4.

Apply 10 kV voltage in the stepwise manner and cross check the values in all step voltages.

5.

Connections of the leads to be carried out as per diagram

6. Note the measurement values of applied voltage, leakage current, power factor and dissipation factor, capacitance, humidity and ambient temperature. (iv) LV-HV connection

Fig. 5.20:

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214

POWER TRANSFORMER - STANDARDISATION MANUAL

1. Short the all three phases of LV and HV winding and make the zero sequence impedance. In other words, make the current flow only in capacitance region (Omit inductance) in the impedance network of the transformer. 2.

Make HV cable connection at LV terminals and LV cable at HV terminals.

3.

Select the test mode UST-YG for capacitance measurement in between tank and windings.

4.

Apply 10 kV in the stepwise manner and cross check the values in all step voltages.

5.

Connections of the leads to be carried out as per diagram

6. Note the measurement values of applied voltage, leakage current, power factor and dissipation factor, capacitance, humidity and ambient temperature. 4.3.2.2 Transformer bushing insulation test a)

Procedure for the test

Measurement of C1 Capacitance and Tan delta 1. Connect the crocodile clip of the HV cable to the top terminal of the shorted HV/IV bushings. 2.

Unscrew the test tap cover, Insert a pin in the hole of the central test tap stud by pressing the surrounding contact plug in case of 245 kV OIP Bushing and remove the earthing strip from the flange by unscrewing the screw (holding earth strip to the flange body) in case of 420 kV OIP Bushing.

3. Connect the LV cable to the test tap (strip/central stud) of the bushing under test to the kit through a screened cable and earth the flange body. 4. Repeat the test for all Bushings by changing only LV lead connection of the kit to test tap of the Bushing which is to be tested Measurement of C2 Capacitance and Tan delta 1. HV lead to be connected to the test tap of the bushing under test (if required additional crocodile type clip may be used) and LV of the kit to be connected to the ground. HV of the bushing is to be connected to the Guard terminal of the test kit. 2.

Test to be carried out in GSTg mode at 1.0kV.

3. Repeat the test for all Bushings by changing only LV lead connection of the kit to test tap of the Bushing which is to be tested

Fig. 5.21:

POWER TRANSFORMER - STANDARDISATION MANUAL

b)

Format of the Test Report



Test equipment Make

c)

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report for Windings VOLTAGE

2 KV 10 KV 2 KV 10 KV 2 KV 10 KV 2 KV 10 KV 2 KV 10 KV 2 KV 10 KV

d)

Type

WINDING COMBINATION

TEST MODE

HV-IV/ LV

UST

HV-IV/ LV+G

GST

HV-IV/ LV with Guard

GSTg

LV/ HV-IV

UST

LV/ HV-IV+G

GST

LV/ HV-IV with Guard

GSTg

TAN δ

CAPACITANCE

REMARK

SITE

FACTORY

SITE

FACTORY

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Format of the Test Report for Bushings (C1) VOLTAGE

2 KV 10 KV 2 KV 10 KV 2 KV 10 KV 2 KV 10 KV 2 KV 10 KV 2 KV 10 KV

Bushings/ Make/ Sr. no

TEST MODE

1U

UST

1V

UST

1W

UST

2U

UST

2V

UST

2W

UST

TAN δ

Capacitance C1

REMARK

SITE

FACTORY

SITE

FACTORY

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

215

216

POWER TRANSFORMER - STANDARDISATION MANUAL

e)

Format of the Test Report for Bushings (C2) VOLTAGE

0.5 KV 1.0 KV 0.5 KV 1.0 KV 0.5 KV 1.0 KV 0.5 KV 1.0 KV 0.5 KV 1.0 KV 0.5 KV 1.0 KV

Bushings/ Make/ Sr. no.

TEST MODE

1U

GST

1V

GST

1W

GST

2U

GST

2V

GST

2W

GST

TAN δ

Capacitance C2

REMARK

SITE

FACTORY

SITE

FACTORY

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.5 KV 1.0 KV

3U

GST

0.5 KV 1.0 KV

3V

GST

3W

GST

0.5 KV 1.0 KV

f)

Acceptance Criteria

Tan δ for bushing (C1): Tan δ (C1)

Type of bushing

Capacitance

 % Limit

 % Change/annum

 % Change/annum

Resin impregnated paper insulated

0.85

+0.04 / -0.04

+1.0 / -1.0

Oil impregnated paper insulated

0.40

+0.02 / -0.06

+1.0 / -1.0

Tan δ for winding – Limit 0.01 (1.0%) 4.3.3 Voltage and Turns Ratio Measurement 4.3.3.1 Voltage Ratio Measurement a)

Purpose of the test



To determine a. Any abnormality in tapings in the winding b. Any abnormality in the winding c. Result ensures the inductance property of the transformer

b)

Equipment for the test



Digital multi meter

POWER TRANSFORMER - STANDARDISATION MANUAL

c)

Principle for the Test

Fig. 5.22:



The total voltage induced into the secondary winding of a transformer is proportional to the number of turns in the primary to the number of turns in the secondary, and by the amount of voltage applied to the primary.

d)

Procedure for the Test 1. Keep the tap position of the transformer in lowest position and LV in open 2. The voltage should be applied in the high voltage winding in order to avoid unsafe voltage 3. Apply 3 phase 415 V on HV terminals 4. Measure the voltage on each phase (ph-ph) on HV and LV terminals simultaneously. 5. Ratio measurement must be made on all the taps to confirm the proper alignment and operation of the tap changer. 6. Calculate the turns ratio in each tap position of tap: Vp/Vs

e)

Test Equipment Make

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

f)

Format of the Test Report



Ratio HV/IV Tap no.

Applied HV voltage 1U1N

1V1N

1W1N

Measured LV voltage 2U2N

2V2N

2W2N

Ratio calculated 1U-1N/ 2U-2N

Ratio actual

1V-1N/ 2V-2N

1W-1N/ 2W-2N

1

 

 

 

2

 

 

 

3

 

 

 

4

 

 

 

5

 

 

 

6

 

 

 

7

 

 

 

217

218

POWER TRANSFORMER - STANDARDISATION MANUAL

Tap no.

Applied HV voltage 1U1N



1V1N

1W1N

Measured LV voltage 2U2N

2V2N

2W2N

Ratio calculated 1U-1N/ 2U-2N

1V-1N/ 2V-2N

1W-1N/ 2W-2N

8

 

 

 

9

 

 

 

10

 

 

 

11

 

 

 

12

 

 

 

13

 

 

 

14

 

 

 

15

 

 

 

16

 

 

 

17

 

 

 

Ratio HV/LV Tap no.

Applied HV voltage 1U1N

1V1N

1W1N

Measured LV voltage 3W3U

3U3V

3V3W

Ratio calculated 1U-1N/ 3W-3U

N



1V-1N/ 3U-3V

1W-1N/ 3V-3W

 

 

Ratio actual

 

Ratio IV/LV Tap no.

Applied HV voltage 2U2N

2V2N

2W2N

Measured LV voltage 3W3U

3U3V

3V3W

N

g)

Ratio actual

Ratio calculated 2U-2N/ 3W-3U

2V-2N/ 3U-3V

2W-2N/ 3V-3W

 

 

Ratio actual

 

Acceptance Criteria The variation of result should be within ± 0.5 % from specified values.

4.3.3.2 Transformer Turns Ratio Test a)

Purpose of the test



To determine the turns ratio of transformers to identify any abnormality in tap changers/ shorted or open turns etc.

b)

Equipment for the test



Automatic Transformer turns ratio (TTR) meter

c)

Principle for the test



The total voltage induced into the secondary winding of a transformer is proportional to the number of turns in the primary to the number of turns in the secondary, and by the amount of voltage applied to the primary.

POWER TRANSFORMER - STANDARDISATION MANUAL

d)

e)

Procedure for the Test 1.

Connect H1 and H2 leads on HV winding and X1 and X2 leads on LV winding.

2.

Apply 110 V AC from the kit.

3.

Adjust the phase angle error on zero.

4.

Adjust % error knob such that null detector shows zero.

5.

Carry out the test for all taps.

Equipment Test equipment Make

f)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report HV/IV Tap no.

HV Voltage KV

LV Voltage KV

Theoretical ratio

Obtained Ratio Error in % R Ph

Y Ph

B Ph

1

 

 

 

2

 

 

 

3

 

 

 

4

 

 

 

5

 

 

 

6

 

 

 

7

 

 

 

8

 

 

 

9

 

 

 

10

 

 

 

11

 

 

 

12

 

 

 

13

 

 

 

14

 

 

 

15

 

 

 

16

 

 

 

17

 

 

 

219

220

POWER TRANSFORMER - STANDARDISATION MANUAL

(b) HV/LV Tap no.

HV Voltage KV

LV Voltage KV

Theoretical ratio

Obtained Ratio Error in % R Ph

N

 

Y Ph  

B Ph  

(c) IV/LV Tap no.

HV Voltage KV

LV Voltage KV

Theoretical ratio

Obtained Ratio Error in % R Ph

N

g)

 

Y Ph  

B Ph  

Acceptance Criteria The variation of result should be within ± 0.5 % from specified values.

4.3.4 Magnetizing Current Test a)

Purpose of the Test



Excitation/ Magnetizing current test is performed to locate defect in magnetic core structure, shifting of windings, failure in turn to turn insulation or problem in tap changer.

b)

Principle of the Test



Excitation/ Magnetizing current is the current required to force a given flux through the core. It is the RMS value of the current flowing through a line terminal of a winding when voltage is applied at rated frequency, the other winding being open circuited.

c)

Equipments for the Test



Digital multi meter

d)

Circuit for the Test

Fig. 5.23:

POWER TRANSFORMER - STANDARDISATION MANUAL

e)

f)

Procedure for the Test 1.

Apply 3 phase 440 V AC supply on HV terminals and keep LV open.

2.

Measure current in all the three phases.

3.

Carry out the test on max., normal and min. tap position.

4.

Repeat the test for LV side.

Test Equipment Make

g)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report Magnetizing current from HV Voltage applied in volts

Current measured in mA Tap 1

Current measured in mA Tap 13

Current measured in mA Tap 17

1U-1N

 

1U

 

1U

 

1U

 

1V-1N

 

1V

 

1V

 

1V

 

1W-1N

 

1W

 

1W

 

1W

 

Magnetizing current from LV Voltage applied in volts

h)

Current measured in mA Tap 1

Current measured in mA Tap 13

Current measured in mA Tap 17

2U-2N

 

2U

 

2U

 

2U

 

2V-2N

 

2V

 

2V

 

2V

 

2W-2N

 

2W

 

2W

 

2W

 

Acceptance Criteria §§

Excitation current < 50 mili-Amperes, then difference between two higher currents should be less than 10%.

§§

Excitation current > 50 mili-Amperes, then difference between two higher currents should be less than 15 %.

§§

Value of center leg should not be more than either outside for a three phase reactor.

§§

Results between similar single phase units should not vary more than 10%.

4.3.5 Magnetic Balance Test a)

Purpose of the Test



To check the balance in the magnetic circuit (core balance) in three phase transformers. It verifies core balance.

b)

Principle of the Test



The voltage should be applied in one phase and measured in the other two phase of the winding. The sharing of the voltage will be maximum in the next phase of the winding (clock wise) more than 60% of the injected voltage and minimum voltage appear in another phase of the winding (clock wise) less than 40% of the injected voltage.

221

222

POWER TRANSFORMER - STANDARDISATION MANUAL

c)

Equipments for the Test



Digital multi meter

d)

Circuit for the Test

Fig. 5.24:

e)

Procedure for the Test 1. For delta connected winding, apply 3 phase 440 V between phase to phase of a winding and measure the voltage induced in other two phases of the same winding. 2. For star winding, apply 1 phase 230 V between phase and neutral and measure the voltage induced in other two phases of the same winding. 3.

f)

Similarly all the phase should be checked with reference to other two phases

Test Equipment Make

g)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report HV side (Tap 1) Voltage applied in volts

Voltage measured at H.V. side 1U-1N

1V-1N

1W-1N

1U-1N

 

 

 

 

1V-1N

 

 

 

 

1W-1N

 

 

 

 

HV side (Tap 13) Voltage applied in volts

Voltage measured at H.V. side 1U-1N

1V-1N

1W-1N

1U-1N

 

 

 

 

1V-1N

 

 

 

 

1W-1N

 

 

 

 

POWER TRANSFORMER - STANDARDISATION MANUAL

HV side (Tap 17) Voltage applied in volts

Voltage measured at H.V. side 1U-1N

1V-1N

1W-1N

1U-1N

 

 

 

 

1V-1N

 

 

 

 

1W-1N

 

 

 

 

IV side (Tap N) Voltage applied in volts

Voltage measured at H.V. side 2U-2N

2V-2N

2W-2N

2U-21N

 

 

 

 

21V-2N

 

 

 

 

2W-2N

 

 

 

 

LV side (Tap N) Voltage applied in volts

h)

Voltage measured at H.V. side 3U-3V

3V-3W

3W-3U

3U-3V

 

 

 

 

3V-3W

 

 

 

 

3W-3U

 

 

 

 

Acceptance Criteria §§

The identical results confirm no damage due to transposition.

§§

Zero voltage or very negligible voltage induced in any of the other two phases shall be investigated.

§§

The applied voltage may be expressed as 100% voltage and the induced voltage may be expressed as percentage of the applied voltage. This will help in comparison of the two results when the applied voltages are different.

§§

The voltage induced in the centre phase shall be 50 to 90% of the applied voltage.

§§

However, when the centre phase is excited then the voltage induced in the outer phases shall be 30 to 70% of the applied voltage.

§§

Zero voltage or very negligible voltage induced in the other two windings should be investigated.

4.3.6 Verification of Vector Group and Polarity a)

Purpose of the Test To verify the phase angle relationship in the winding and polarity of transformer

b)

Principle of the Test



By shorting the R phase of HV and LV terminals, the magnitude of the phases by using the phase angle relationship is obtained

c)

Equipment for the Test Digital multi meter

223

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POWER TRANSFORMER - STANDARDISATION MANUAL

d)

Procedure for the Test 1.

Keep the tap position of transformer at normal

2.

Short 1U of HV and 2U of LV

3.

Apply 440 V 3 phase supply to HV terminals

4.

Measure the voltage across the following terminals as below

5.

Make conditions in the way of arithmetical and logical for verifying the phase angle difference

For Yy0 transformer Rn+Nn=RN Bb=Yy By=Yb For Yna0d11 transformer

Fig. 5.25:

2R1-N=2Y1-N=2B1-N=Constant 2R1-1B1=3R1-N>3Y1-N>3B1-N 3Y1-1B1>3Y1-1Y1 e)

Test Equipment Make

f)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report For star /star Terminal

Voltage measured

Rn

 

Nn RN

POWER TRANSFORMER - STANDARDISATION MANUAL

Terminal

Voltage measured

Bb Yy By bY

g)

Acceptance Criteria



Verify that all arithmetical relations are maintained as in the above formula as per the vector group of transformer

4.3.7 Short Circuit Impedance Test a)

Purpose of the Test



This test is used to detect winding movement that usually occurs due to heavy fault current or mechanical damage during transportation or installation since dispatch from the factory. It is expressed as a percentage of the rated voltage of former winding. In this case current flowing through secondary is the full load current and is indicative of copper losses.

b)

Principle of the Test



Rated full load current to flow through this winding when secondary winding is shorted, is known as impedance voltage

c)

Equipment for the Test



Digital ampere meter

d)

Circuit for the Test

Fig. 5.26:

e)

Procedure for the Test 1.

Connect the 3 ph 440 V supply to the HV winding and short the 3 phase of LV winding.

2.

Measure primary voltage and current on HV and LV.

3.

Carry out the test on min., normal and max. Tap positions.

225

226

POWER TRANSFORMER - STANDARDISATION MANUAL

f)

Test Equipment Make

g)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report HV/IV (Tap 1) Voltage applied

Current measured in Amp H.V. side

1U-1V 1V-1W 1W-1U

     

L.V. side

1U

 

2U

 

1V

 

2V

 

1W

 

2W

 

IN-n  

HV/IV (Tap 13) Voltage applied

Current measured in Amp H.V. side

L.V. side

1U-1V

 

1U

 

2U

 

1V-1W

 

1V

 

2V

 

1W-1U

 

1W

 

2W

 

IN-n  

HV/IV (Tap 17) Voltage applied

Current measured in Amp H.V. side

L.V. side

1U-1V

 

1U

 

2U

 

1V-1W

 

1V

 

2V

 

1W-1U

 

1W

 

2W

 

IN-n  

HV/LV (Tap N) Voltage applied

Current measured in Amp H.V. side

L.V. side

1U-1V

 

1U

 

3U

 

1V-1W

 

1V

 

3V

 

1W-1U

 

1W

 

3W

 

IN-n  

IV/LV (Tap N) Voltage applied

Current measured in Amp H.V. side

L.V. side

2U-2V

 

2U

 

3U

 

2V-2W

 

2V

 

3V

 

2W-2U

 

2W

 

3W

 

IN-n  

POWER TRANSFORMER - STANDARDISATION MANUAL

Impedance Verification (HV/IV) Tap no.

Average S/C current on LV side

Average Voltage measured for S/C current on HV side

Impedance voltage

% Impedance voltage

1

 

 

 

 

13

 

 

 

 

17

 

 

 

 

Impedance Verification (HV/LV) Tap no. N

Average S/C current on LV side  

Average Voltage measured for S/C current on HV side  

Impedance voltage  

% Impedance voltage  

Impedance Verification (IV/LV) Tap no.

Average S/C current on LV side

N

 

Average Voltage measured for S/C current on HV side  

Impedance voltage  

% Impedance voltage  

h)

Acceptable Criteria



The measured impedance voltage should be within 3 percent of impedance specified in rating and diagram nameplate of the transformer.



Variation in impedance voltage of more than 3% should be considered significant and further investigated

4.3.8 Measurement of Winding Resistance a)

Purpose of the Test



To check for any abnormalities like loose connections, broken strands and high contact resistance in tap changers due to vibrations, fault occurred due to poor design, assembly, handling, poor environment, over loading or poor maintenance and gross difference between the windings and for openness in the connections.

b)

Principle of the Test



Kelvin bridge technique was adopted in the way of modern digital micro processor method for measuring the winding resistance. Voltage drop is proportional to the winding resistance by injecting the DC current. Voltage drop across the winding terminal in the phase is in the following manner



U= R*I + (d0/dt); 0-flux



L= 0/t



When DC current is applied, (d0/dt) =0



So, U=R*I

c)

Equipment for the Test



Automatic winding resistance measurement kit which work on the principle of Kelvin Bridge.

227

228

POWER TRANSFORMER - STANDARDISATION MANUAL

d)

Circuit for the Test

Fig. 5.27:

e)

Procedure for the Test 1.

Connect the current and potential leads to the transformer winding.

2.

The potential leads must be connected between the current leads.

3.

Do not clip the potential leads to the current leads.

4.

Do not use additional extension cable leads.

5.

Observe the polarity.

6.

Select the test current range, which should be more than 1 % of rated current.

7.

Test current should not be more than 10% of rated current.

8. If less than 1%, measured resistance is not consistent. 9.

If more than 10%, it could cause erroneous readings due to over heating of the winding.

10. If possible, always inject test current to HV and LV simultaneously (two channel measurement). 11. This will magnetize the core more efficiently and shorten the time to get stable readings. 12. Measure the readings in both positive and negative polarities (tap position in ascending and descending position) 13. During tap changing operation, continuity checks between HV to neutral to be carried out by analog multi meter while changing tap. 14. For delta connected windings, such as tertiary winding of auto-transformers, measurement shall be done between pairs of line terminals and resistance per winding shall be calculated as per the following formula a.

Resistance per winding = 1.5 x Measured value

15. Take the winding temperature reading while doing the resistance measurement. 16. Calculate the resistance at 75°C as per the following formula 17. R = R (235+75)/(235+t ),Where R = Resistance measured at winding temperature t

POWER TRANSFORMER - STANDARDISATION MANUAL

f)

Test Equipment Make

g)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report Temperature reading Temp.- deg C OTI

 

WTI

 

(a) HV-N Tap no.

Winding resistance in mili ohm 1U-1N

1V-1N

1W-1N

1

 

 

 

2

 

 

 

3

 

 

 

4

 

 

 

5

 

 

 

6

 

 

 

7

 

 

 

8

 

 

 

9

 

 

 

10

 

 

 

11

 

 

 

12

 

 

 

13

 

 

 

14

 

 

 

15

 

 

 

16

 

 

 

17

 

 

 

229

230

POWER TRANSFORMER - STANDARDISATION MANUAL

(b) IV-N Tap no.

Winding resistance in mili ohm 2U-N

N

 

2V-N  

2W-N  

(c) LV Tap no.

Winding resistance in mili ohm 3U-3V

N

h)

 

3V-3W  

3W-3U  

Acceptance criteria All readings should be within +/- 1% of each other.



There should be even increase or decrease of resistance value for the winding having tapping winding for all three phase

4.3.9 Winding Insulation Resistance Measurement a)

Purpose of the Test



This test reveals the condition of voids in the dielectric insulations like solid insulation in the winding due to heat or moisture, any dampness solubility in the oil, presence of any foreign objects which is having the corrosive characteristic present in the bushing.

b)

Principle of the Test



If a test voltage ids applied across a piece of insulation, then by measuring the resultant current and applying ohm’s law (R=E/I), the resistance of the insulation can be calculated. Effect of temperature in measurement.



For every 10 deg increase in temperature, half the resistance; or for every 10 deg increase in temperature, double the resistance. For example, a 100 Gohm resistance at 20 deg becomes 25 Gohm at 40 deg. Cen.

c)

Equipment for the Test Motorized or battery operated insulation tester (0-5 KV range)

d)

Circuit for the Test a. HV/E+LV Shorted

Fig. 5.28:

POWER TRANSFORMER - STANDARDISATION MANUAL

b. LV/E + HV Shorted

Fig. 5.29:

c. HV /LV + Ground Open

Fig. 5.30:

e)

Procedure for the Test 1. Connect leads to HV winding and LV winding to measure IR between windings. 2. Apply 5 KV and take measurement at interval of 15 sec, 60 sec and 600 sec 3. Connect leads between winding and earth to measure IR between winding and earth. 4. Keep the other windings shorted and earthed. 5. Repeat the test.

f)

Test Equipment Make

g)

Format of the Test Report Temp.- deg C OTI

 

WTI

 

Amb.

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

231

232

POWER TRANSFORMER - STANDARDISATION MANUAL

Conn.

IR value in Mohm 15 Sec

h)

60 Sec

PI=IR at 600 sec/IR at 60 sec 600 Sec

HV to E

 

 

 

 

LV to E

 

 

 

 

HV to LV

 

 

 

 

Acceptance Criteria Min. insulation values for one minute resistance for transformer

R=C*E/ (KVA) ^0.5. Where, C=1.5 for oil filled Tr at 20oC. E= Voltage rating in V (Ph-Ph for delta and Ph-n for Y) KVA= Rated capacity of the Tr. As per CBIP guideline, acceptable value is 2 Mega Ohm per KV at 60 oC Rated voltage

Recommended accepted limit as a thumb rule as per CBIP guideline Min IR Value for 1 min. at 30 deg

11 KV

300 M Ohm

33 KV

550 M Ohm

66 KV

625 M Ohm

132 KV

700 M Ohm

220 KV

750 M Ohm

400 KV

900 M Ohm

Polarization index insulation condition PI value

Insulation condition

Less than 1

Wet, Dangerous

1.0-1.1

Poor

1.1-1.25

Fair

1.25-2.0

Good

>2.0

Dry

>3

Not good (Poor impregnation of oil in insulation paper, charging current is still increasing and not steady state)

POWER TRANSFORMER - STANDARDISATION MANUAL

4.3.10 Core Insulation Test a)

Purpose of the Test



To check that core is not earthed other than the specific earth point.

b)

Principle of the Test



The ground connection terminals for the transformer core are located at top plate of transformer in a box. The terminals are protected by a cover. The terminal box contains a terminal block with three terminals 1.

Terminal marked CL is connected to core lamination

2.

Terminal marked CC is connected to core clamps

3.

Terminal marked G is connected to ground

c)

Equipment for the Test:



Motorized or battery operated insulation tester (0-5 KV range)

d)

Procedure for the Test:

e)

1.

Shorting link between Core, frame and earth to be removed

2.

Apply 2.5 KV and take measurement at interval of 60 sec

3.

After completion of Test, provide shorting link between core, frame and earth

Test Equipment Make

f)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format for the Test Conn.

IR value in Mohm 60 Sec

g)

CC-CL

 

CL-G

 

CC-G

 

Acceptance Criteria IR should be > 1000 MΩ

4.3.11 Oil Characteristisc Test a)

Purpose of the Test



To check the electrical, mechanical & chemical property of the oil.



The dielectric break down voltage Test is an important Test to determine the withstanding capacity of any insulating oil. There is a degradation of transformer oil or ingress of moisture and it is necessary to Test the insulating oil periodically.

b)

Equipment for the Test



Motorized oil BDV Test kit

233

234

POWER TRANSFORMER - STANDARDISATION MANUAL

c)

Procedure for the Test: 1. Take oil sample from the bottom of the main tank in the oil cup. Always flush drain valve before taking sample 2.

Also flush the oil cup

3.

Let the bubbles be settled down

4.

Carry out the Test and take reading at which oil insulation break down

5.

Take 6 readings at time interval of 10 min.

6.

Average of the 6 readings is final BDV of oil

7.

Oil sample to be collected from bottom of the main tank and to be sent to ERDA to carry out tests as per IS 1866

8. Oil sample to be collected from bottom of the main tank and to be sent to ERDA to carry out tests for DGA d)

Test Equipment Make

e)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report BDV Make

BDV -1

BDV -2

BDV -3

BDV -4

BDV -5

BDV -6

Average

Main tank top

 

 

 

 

 

 

 

Main tank bottom OLTC tank

f)

Acceptance Criteria Sr. no.

Particular

Accepted norms at the time of first charging

As per Standard

A

Appearance

Clear, free from sediment and suspended matter

Visual

B

BDV (2.5 mm gap)  

70 KV for < 72.5 KV

IEC 60156

80 KV for 72.5 KV to 170 KV

IEC 60156

90 KV for >170 KV

IEC 60156

20 ppm for <72.5 KV

IEC 60814

15 ppm for 72.5 KV to 170 KV

IEC 60814

10 ppm for >170 KV

IEC 60814

C

Water content

D

Acidity

1.2 KOH/g, maximum

IS-1866-2000 IEC 61125 (method C)

E

PCB content

not detectable (less than 2 ppm)

IEC 61619

Sr. no.

Particular

Accepted norms at the time of first charging

As per Standard

POWER TRANSFORMER - STANDARDISATION MANUAL

F



Resistivity Resistivity at 90 OC

6x1012 Ohm-Cm

IS-1866-2000

G

Tan delta at 90 OC

0.02 maximum

IEC 60247

H

Interfacial Tension at 27 OC

0.04 N/m

ISO 6295

I

Flash point

135 OC

ISO 2719

J

Density at 29.5 OC

0.89 g/cm3

ISO 3104

K

Kinetic viscosity at 27OC

27 cSt

IS-1866-2000

L

Pour point

-30 OC

IS-1448-P10 ISO 3016

M

Oxidation stability of uninhibited oil 1) Neutralization value (Max)

0.1 mg KOH/g

IEC 62021-1/2

2) Sludge (max)

0.8% by weight

IS-1866-2000

Additional requirement for inhibited oil

minimum 0.25% maximum 0.40 %

IEC 60666

If BDV value is very low and unacceptable (<30 KV/2.5 mm gap), then it is necessary to dry out & clean the oil till the insulation reaches the satisfactory value.

4.3.12 Tests on Bushing CTs a)

Purpose of the Test



These tests are carried out to identify the healthiness of bushing CT s and verifying the measuring and protection systems

b)

Equipment for the Test Digital multi meter Insulation tester Knee point measurement kit Current injection kit

c)

Procedure for the Test



While testing, the other windings on the same phase of the transformer may have to short circuited in order to obtain a stable reading. It is better to demagnetize any CT that is tested by impressing DC voltage across winding. Rated parameters CORE Core - I Core - II Core - III Core - IV

RATIO

CLASS

BURDEN

kpV

PROTECTION / METERING

235

236

POWER TRANSFORMER - STANDARDISATION MANUAL

A. Polarity Test a)

Purpose of the Test



The polarity should show in accordance with the terminal markings

b)

Procedure for the Test 1.

The polarity test can be done by inductive kick of direct current

2. In this test, a 1.5 V battery is connected to the primary P1-P2 of CT in such a manner that +ve terminal of batter to be connected to P1 and –ve terminal to be connected to P2.

c)

3

Connect +ve lead of voltmeter in S1 and –ve terminal in S2

4.

Close the switch and apply 1.5 V DC, check the deflection

5.

It should be in +ve deflection

Test Equipment Make

d)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report CORE

BETWEEN

HV R-Ø

Core I

Core II

Core III

Core IV

CORE

 1S1 (+ve)

 1S2 (-ve)

 1S1 (+ve)

 1S3 (-ve)

 2S1 (+ve)

 2S2 (-ve)

 2S1 (+ve)

 2S3 (-ve)

 3S1 (+ve)

 3S2 (-ve)

 3S1 (+ve)

 3S3 (-ve)

 4S1 (+ve)

 4S2 (-ve)

 4S1 (+ve)

 4S3 (-ve)

BETWEEN

Core II

Core III

Core IV

B-Ø

N-Ø

LV R-Ø

Core I

Y-Ø

 1S1 (+ve)

 1S2 (-ve)

 1S1 (+ve)

 1S3 (-ve)

 2S1 (+ve)

 2S2 (-ve)

 2S1 (+ve)

 2S3 (-ve)

 3S1 (+ve)

 3S2 (-ve)

 3S1 (+ve)

 3S3 (-ve)

 4S1 (+ve)

 4S2 (-ve)

 4S1 (+ve)

 4S3 (-ve)

Y-Ø

B-Ø

N-Ø

POWER TRANSFORMER - STANDARDISATION MANUAL

e)

Acceptance Criteria All CT secondary polarity should be as per name plate

B. Current ratio Test a)

Purpose of the Test



To measure the ratio of a primary to secondary current in the bushing CT and find the current ratio error

b)

Procedure for the Test

c)

1.

Connect the current injection kit to the primary of the bushing CT and measure the current through tong tester having the range of 300A

2.

Measure the current through tong tester having the range of 300mA in secondary CT

3.

Apply 20% of rated current to he primary side

4.

Measure the corresponding primary and secondary current.

5.

% error of CT ratio = (Measured current ratio- Theoretical ratio)/Theoretical ratio

Test Equipment Make

d)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report (a) HV R Core

Terminals

Primary %

Core I

(1S1 – 1S2)

20%

(1S1-1S3)

20%

(2S1 – 2S2)

20%

(2S1-2S3)

20%

(3S1 – 3S2)

20%

(3S1-3S3)

20%

(4S1 – 4S2)

20%

(4S1-4S3)

20%

Core II

Core III

Core IV

Current Actual

Secondary Current

Theoretical Ratio

Actual Ratio

% of Error

(b) HV Y Core

Terminals

Core I

(1S1 – 1S2)

20%

(1S1-1S3)

20%

(2S1 – 2S2)

20%

(2S1-2S3)

20%

(3S1 – 3S2)

20%

(3S1-3S3)

20%

(4S1 – 4S2)

20%

(4S1-4S3)

20%

Core II

Core III

Core IV

Primary %

Current Actual

Secondary Current

Theoretical Ratio

Actual Ratio

% of Error

237

238

POWER TRANSFORMER - STANDARDISATION MANUAL

(c) HV B Core

Terminals

Core I

(1S1 – 1S2)

20%

(1S1-1S3)

20%

(2S1 – 2S2)

20%

(2S1-2S3)

20%

(3S1 – 3S2)

20%

(3S1-3S3)

20%

(4S1 – 4S2)

20%

(4S1-4S3)

20%

Core

Terminals

Primary %

Core I

(1S1 – 1S2)

20%

(1S1-1S3)

20%

(2S1 – 2S2)

20%

(2S1-2S3)

20%

(3S1 – 3S2)

20%

(3S1-3S3)

20%

(4S1 – 4S2)

20%

(4S1-4S3)

20%

Core

Terminals

Primary %

Core I

(1S1 – 1S2)

20%

(1S1-1S3)

20%

(2S1 – 2S2)

20%

(2S1-2S3)

20%

(3S1 – 3S2)

20%

(3S1-3S3)

20%

(4S1 – 4S2)

20%

(4S1-4S3)

20%

Core II

Core III

Core IV

Primary %

Current Actual

Secondary Current

Theoretical Ratio

Actual Ratio

% of Error

Current Actual

Secondary Current

Theoretical Ratio

Actual Ratio

% of Error

Current Actual

Secondary Current

Theoretical Ratio

Actual Ratio

% of Error

(d) HV N

Core II

Core III

Core IV

(e) IV R

Core II

Core III

Core IV

POWER TRANSFORMER - STANDARDISATION MANUAL

(f) IV Y Core

Terminals

Core I

(1S1 – 1S2)

20%

(1S1-1S3)

20%

(2S1 – 2S2)

20%

(2S1-2S3)

20%

(3S1 – 3S2)

20%

(3S1-3S3)

20%

(4S1 – 4S2)

20%

(4S1-4S3)

20%

Core

Terminals

Primary %

Core I

(1S1 – 1S2)

20%

(1S1-1S3)

20%

(2S1 – 2S2)

20%

(2S1-2S3)

20%

(3S1 – 3S2)

20%

(3S1-3S3)

20%

(4S1 – 4S2)

20%

(4S1-4S3)

20%

Core

Terminals

Primary %

Core I

(1S1 – 1S2)

20%

(1S1-1S3)

20%

(2S1 – 2S2)

20%

(2S1-2S3)

20%

(3S1 – 3S2)

20%

(3S1-3S3)

20%

(4S1 – 4S2)

20%

(4S1-4S3)

20%

Core II

Core III

Core IV

Primary %

Current Actual

Secondary Current

Theoretical Ratio

Actual Ratio

% of Error

Current Actual

Secondary Current

Theoretical Ratio

Actual Ratio

% of Error

Current Actual

Secondary Current

Theoretical Ratio

Actual Ratio

% of Error

(g) IV B

Core II

Core III

Core IV

(h) IV N

Core II

Core III

Core IV

e)

Acceptance Criteria



Ratio error should match with factory results

239

240

POWER TRANSFORMER - STANDARDISATION MANUAL

C. Excitation Current a)

Purpose of the Test



The magnetization test is conducted in order to see the condition of the turns of the secondary. This test gives the indications regarding the shorting of turns CT secondary winding and to establish CT characteristics as well as capability of CT.

b)

Procedure of the test

c)

1.

Apply AC voltage to the secondary winding of the CT with primary open circuit

2.

Vary the applied voltage from 25% of Vk to 110 % of Vk

3.

Measure the current drawn by the winding at each selected value is recorded

4.

Verify that, exciting current is less than specified at Vk/2

5.

This test should not be performed for metering core

6.

If Knee Point Voltage is not mentioned then Knee Point Current may be taken into consideration.

Test Equipment Make

d)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report i.

HV R Voltage To Be Applied

ii.

Actual Value

Excitation current

0.25 x KVp

mA

0.50 x KVp

mA

0.75 x KVp

mA

1.00 x KVp

mA

1.10 x KVp

mA

Current Measurement Core – I 1S1-1S3

Core – II 2S1-2S3

Core – III 3S1-3S3

Core – IV 4S1-4S3

HV Y Voltage To Be Applied

Actual Value

Excitation current

0.25 x KVp

mA

0.50 x KVp

mA

0.75 x KVp

mA

1.00 x KVp

mA

1.10 x KVp

mA

Current Measurement Core – I 1S1-1S3

Core – II 2S1-2S3

Core – III 3S1-3S3

Core – IV 4S1-4S3

POWER TRANSFORMER - STANDARDISATION MANUAL

iii. HV B Voltage To Be Applied

Actual Value

Excitation current

0.25 x KVp

mA

0.50 x KVp

mA

0.75 x KVp

mA

1.00 x KVp

mA

1.10 x KVp

mA

Current Measurement Core – I 1S1-1S3

Core – II 2S1-2S3

Core – III 3S1-3S3

Core – IV 4S1-4S3

iv. HV N Voltage To Be Applied

v.

Actual Value

Excitation current

0.25 x KVp

mA

0.50 x KVp

mA

0.75 x KVp

mA

1.00 x KVp

mA

1.10 x KVp

mA

Current Measurement Core – I 1S1-1S3

Core – II 2S1-2S3

Core – III 3S1-3S3

Core – IV 4S1-4S3

IV R Voltage To Be Applied

Actual Value

Excitation current

0.25 x KVp

mA

0.50 x KVp

mA

0.75 x KVp

mA

1.00 x KVp

mA

1.10 x KVp

mA

Current Measurement Core – I 1S1-1S3

Core – II 2S1-2S3

Core – III 3S1-3S3

Core – IV 4S1-4S3

vi. IV Y Voltage To Be Applied

Actual Value

Excitation current

0.25 x KVp

mA

0.50 x KVp

mA

0.75 x KVp

mA

1.00 x KVp

mA

1.10 x KVp

mA

Current Measurement Core – I 1S1-1S3

Core – II 2S1-2S3

Core – III 3S1-3S3

Core – IV 4S1-4S3

241

242

POWER TRANSFORMER - STANDARDISATION MANUAL

vii. IV B Voltage To Be Applied

Excitation current

Actual Value

0.25 x KVp

mA

0.50 x KVp

mA

0.75 x KVp

mA

1.00 x KVp

mA

1.10 x KVp

mA

Current Measurement Core – I 1S1-1S3

Core – II 2S1-2S3

Core – III 3S1-3S3

Core – IV 4S1-4S3

viii. IV N Voltage To Be Applied

e)

Excitation current

Actual Value

0.25 x KVp

mA

0.50 x KVp

mA

0.75 x KVp

mA

1.00 x KVp

mA

1.10 x KVp

mA

Current Measurement Core – I 1S1-1S3

Core – II 2S1-2S3

Core – III 3S1-3S3

Core – IV 4S1-4S3

Acceptance Criteria Excitation current should not be more than specified on name plate. 10 % increase in the voltage from 100 % to 110 %, increase in current should not be more than 50%

D. Insulation Resistance Measurement a)

Purpose of the Test



To check any shorting of any CT secondary core with earth or between cores

b)

Procedure for the Test 1.

IR measurement secondary core to earth

2.

Connect insulation tester leads between CT secondary and earth

3.

Apply 500 V DC and measure IR value

4.

Carry out test for all cores of all HV and IV CTs

5.

IR measurement secondary core to core

6.

Connect insulation tester leads between CT secondary cores

7.

Apply 500 V DC and measure IR value

8. Carry out test for all combinations of core to core for all HV and IV CTs c)

Test Equipment Make

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

POWER TRANSFORMER - STANDARDISATION MANUAL

d)

Format of the Test Report Measurement Between

Unit

HV R–Ø

Earth - Core I

MΩ

Earth - Core II

MΩ

Earth - Core III

MΩ

Earth - Core IV

MΩ

Measurement Between

Unit

MΩ

Earth - Core II

MΩ

Earth - Core III

MΩ

Earth - Core IV

MΩ

Measurement Between

Unit

MΩ

Core I - Core III

MΩ

Core I - Core IV

MΩ

Core II - Core III

MΩ

Core II - Core IV

MΩ

Core III - Core IV

MΩ

Measurement Between

Unit

MΩ

Core I - Core III

MΩ

Core I - Core IV

MΩ

Core II - Core III

MΩ

Core II - Core IV

MΩ

Core III - Core IV

MΩ

Y-Ø

B-Ø

N-Ø

Y-Ø

B-Ø

N-Ø

IV R–Ø

Core I - Core II

N-Ø

HV R–Ø

Core I - Core II

B-Ø

IV R–Ø

Earth - Core I

Y-Ø

Y-Ø

e)

Acceptance Criteria



Insulation resistance should be more than 50 Mega ohm

B-Ø

N-Ø

243

244

POWER TRANSFORMER - STANDARDISATION MANUAL

E. Continuity test of Bushing CT secondary winding a)

Purpose of the Test



To check any open of any CT secondary core including pilot wires up to C & R panel

b)

Procedure for the Test 1. Connect multi meter across each core and check continuity up to Tr MK box and up to remote protection panel end. 2.

c)

Carry out test for all cores of all HV and IV CTs

Test Equipment Make

d)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report Measurement Between Core - I

Between Terminal

HV R–Ø

Y-Ø

B-Ø

N-Ø

1S1-1S2 1S1-1S3

Core - II

2S1-2S2 2S1-2S3

Core - III

3S1-3S2 3S1-3S3

Core - IV

4S1-4S2 4S1-4S3

Measurement Between Core - I

Between Terminal R–Ø 1S1-1S2 1S1-1S3

Core - II

2S1-2S2 2S1-2S3

Core - III

3S1-3S2 3S1-3S3

Core - IV

LV

4S1-4S2 4S1-4S3

e)

Acceptance Criteria



Continuity test should be OK

Y-Ø

B-Ø

N-Ø

POWER TRANSFORMER - STANDARDISATION MANUAL

F. Winding resistance measurement of bushing CT secondary winding a)

Purpose of the Test



To check healthiness of winding of CT secondary up to MK Box of Transformer

b)

Procedure for the Test

c)

1.

Connect multi meter across each core and measure winding resistance up to Tr MK box.

2.

Carry out test for all cores of all HV and IV CTs

Test Equipment Make

d)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report

Measurement Between

Between Terminal

Unit

HV R–Ø

1S1-1S2

Ω

1S1-1S3

Ω

2S1-2S2

Ω

2S1-2S3

Ω

3S1-3S2

Ω

3S1-3S3

Ω

4S1-4S2

Ω

4S1-4S3

Ω

Measurement Between

Between Terminal

Unit

Core - I

1S1-1S2

Ω

1S1-1S3

Ω

2S1-2S2

Ω

2S1-2S3

Ω

3S1-3S2

Ω

3S1-3S3

Ω

4S1-4S2

Ω

4S1-4S3

Ω

Core - I

Core - II

Core - III

Core - IV

Core - II

Core - III

Core - IV

Y-Ø

B-Ø

N-Ø

LV R–Ø

Y-Ø

e)

Acceptance Criteria



Winding resistance should be comparable with factory results

B-Ø

N-Ø

245

246

POWER TRANSFORMER - STANDARDISATION MANUAL

4.3.13 Operational Tests and Checks on other Equipments A. Temperature Indicators

The function of temperature indicator is to monitor and control the temperature of oil and winding in the transformer. There are two types of temperature indicators. 1.

Winding temperature indicator in each winding

2.

Oil temperature indicator

B. Winding Temperature Indicator In WTI the first to check the working of cooler control, alarm and trip signal a)

Procedure for the Test 1.

Access the local winding temperature indicator and rotate the temperature indicator pointer slowly to the first stage cooling value (65 deg C). Check that the fans of those coolers are working.

2. Continue rotating pointer to second stage cooling value (80 deg C). Check that the fans of those coolers are working 3. Rotating the pointer to alarm value (110 deg C). Check in control room to ensure that alarm signal 4. Rotate the pointer to (125 deg C) trip value. Check in control room to ensure that trip signal has been received. b)

Procedure calibration of WTI with hot oil 1.

Remove the winding temperature indicator bulb from transformer pocket.

2. Insert the bulb in to calibrated temperature controlled bath. Raise the temperature of the bath in 5 deg C steps and check the response of winding temperature indicator after 10 minutes. 3.

This continue up to 30 deg C. Allowable tolerance is =/- 3 deg C.

4. Reduce the temperature of the bath in 5 deg C steps and check corresponding temperature in the indicator after 10 minutes. Allowable tolerance is +/-3 deg C 5.

WTI OFAF rating check by using calibrated temperature controlled bath procedure:

6. Remove WTI sensor from transformer lid and put in to calibrated temperature controlled ol bath. 7.

Increase temperature of oil bath in 20 deg C steps from 30 deg C up to maximum temperature of 150 deg C.

8. Check and record WTI output readings in milliamps DC against temperature in accordance with table below. Temperature

mili amps

30

4.0

40

5.3

60

8.0

80

10.7

100

13.3

120

16.0

140

18.7

POWER TRANSFORMER - STANDARDISATION MANUAL

c)

Procedure for Secondary Injection Test for WTI 1.

First isolate all cooler supplies from WTI

2. Then replace WTI bulb in to calibrated temperature controlled bath and maintain constant temperature of 50 deg C 3.

Inject the rated current (4.9A) in to appropriate terminals on winding temperature indication test panel

C. Oil Temperature Indicators a)

Procedure for the Test 1.

Access the local winding temperature indicator and rotate the temperature indicator pointer slowly to the alarm value (95 deg C). Check in control room to ensure that alarm signal.

2. Continue rotating pointer to (110 deg C) trip value. Check in control room to ensure that trip signal has been received. b)

Procedure for calibration of OTI with hot oil 1.

Remove the oil temperature indicator bulb from transformer pocket.

2.

Insert the bulb in to calibrated temperature controlled oil bath.

3.

Raise the temperature of the bath in 20 deg C steps and check the response of oil temperature indicator after 10 minutes.

4.

This continue up to 120 deg C. Allowable tolerance is =/- 3 deg C.

D. Operational checks of Magnetic Oil Gauge

The function of MOG is to indicate the continuous level of oil inside the transformer on a calibrated dial.



The calibrated scale having three markings: Low, 35 deg fill level and High.



It should show 35 deg (normal level) of oil in the tank

E.

Operational checks of Pressure Relief Valve Procedure Check the normality open and normality close contacts by lifting the pressure valve

F.

Tests on OLTC 1.

Conduct the visual inspection of equipment

2.

Check the manual operation of all taps (Local)

3.

Check complete wiring of the circuit

4.

Check the limit switch

5.

Check the over load device of driving motor by measuring the current

6.

Check the local electrical operation of OLTC

7.

Check the remote electrical operation of OLTC

8. Check the status of tap position indicator 9.

Check operation of master and follower scheme (Parallel operation)

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Sr. no

Description  

Status OK

1

Visual inspection of equipment

2

Manual operation of all taps (Local)

3

Overload device of driving motor

4

Local operation (Electrical)

5

Remote operation (Electrical)

6

Tap position indicator

7

Check operation with master follower scheme

Not OK

G. Test on Buchholz Relay 1.

Check the normality open and normality close contact by following steps

2.

Close the conservator flow valve and tank flow valve which is present in the conservator pipe line

3.

Drain the oil which is present in between the two valves

4.

Ensure the contact change by using the multi meter in two steps alarm and trip

5.

After closing the drain knob in buchholz relay then close the conservator valve first and close tank valve

H. Cooling System Check 1.

Check all radiator valves are open

2.

To check the motor insulation healthiness by doing the IR test

3.

To check the excitation current measurement in the motor winding

4.

To check the direction of rotation in motor

5.

To verify the cooling interlocks

4.3.14 Measurement of Earthing Pit Resistance a)

Purpose of the Test



To measure value of earthing pit resistance and verify that, fault current has minimum resistance to ground

b)

Principle of the Test



There is hand operated D.C.generator. While feeding current to spike, D.C. current is converted into A.C. current by the converter and A.C. current received from spike is again converted in D.C. current by the help of rectifier, while going to generator. A.C. current is fed to the spike driven in earth because there should not be electrolytic effect.

c)

Equipment for the Test Earth tester

POWER TRANSFORMER - STANDARDISATION MANUAL

d)

Circuit for the Test

Fig. 5.31:

e)

Procedure for the Test 1.

Earth tester is used for measurement of Earth resistance.

2. For measurement of earth pit resistance, pit earthing connection should be disconnected from main grid. 3. Earth tester terminals C1 & P1 are shorted to each other and connected to the earth electrode (pipe) under test. 4.

Terminals P2 & C2 are connected to the two separate spikes driven in earth.

5. These two spikes are kept in same line at the distance of 25 meters and 50 meters due to which there will not be mutual interference in the field of individual spikes.

f)

6.

If we rotate generator handle with specific speed we get directly earth resistance on scale.

7.

If earth resistance is more, proper treatment is to be given.

Test Equipment Make

g)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report Earthing Pit Resistance Pit no

Resistance in ohm

Body earth 1

 

Body earth 2 HV Neutral earth 1 HV Neutral earth 2 LV Neutral earth 1 LV Neutral earth 2

h)

Acceptance Criteria Value of earth pit resistance should be less than or equal to 1 ohm.

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4.3.15 Protection and Alarms Sr. no

Device

Set for Alarm

1

Winding temperature high

2

Oil temperature high

3

Oil flow failure

4

Pressure relief valve

5

Main tank buchholz relay

6

OLTC buchholz relay

7

Fan failure

8

OTI main Tank

9

WTI main tank

10

Low oil level

11

Differential relay

12

Over load rely

13

Earth fault relay

14

Directional over current

15

Inter trip relay operated

16

Trip free check

17

Backup over current

18

Restricted earth fault

19

Over flux

Actual Trip

Alarm

Trip

a)

Acceptance Criteria



Prove the tripping of associated breakers by actual operation of the various devices and relays as per the schemes

4.3.16 Contact Resistance Measurement a)

Purpose of the Test



To determine the firmness of torque level in between the bushing jumper and transmission line If torque level is more than or less then the standard position, the heat will dissipated in the joints.



It leads to corrosion in the joints.

b)

Principle of the Test



Voltage drop is proportional to the contact resistance by injecting the DC current. It depends on the voltage drop across the contact terminal in between the transmission line and the jumper of the bushing.

c)

Procedure Direct measurement of resistance by using micro ohm meter

POWER TRANSFORMER - STANDARDISATION MANUAL

d)

Test Equipment Make

e)

Type

Sr. no.

Range

Cal. Due date

 

 

 

 

Format of the Test Report Contact resistance Across HV bushing terminal joints

R ph

Y ph

B ph

 

 

 

Across IV bushing terminal joints Across LV bushing terminal joints Across Neutral connection point Across surge arrestor connection

f)

Acceptance Criteria The value of contact resistance should not be more than 5 micro ohm per joint/ connector

4.3.17 Clearances Check the clearances for live parts a)

Format of the Test Report Particular

Clearance

HV phase to phase

 

HV phase to earth IV phase to phase IV phase to earth LV phase to phase LV phase to earth

4.3.18 Protection Relay Settings Particular

Value

Settings of OTI alarm

 

Settings of OTI trip Settings of WTI alarm Settings of WTI trip Settings of start & stop of cooling fan set -1 Settings of start & stop of cooling fans set-2

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4.3.19 Final Documentation Review 1

Final document of pre commissioning checks reviewed and approved.

YES 

NO

2

Documents regarding spares, equipment, O & M manuals etc are available at site for O & M purpose.

YES

NO

3

After modification, if any, as built drawings are available at site

5

FINAL COMMISSIONING CHECKS



It is important to ensure seamless, full and final integration of power transformer in a substation after commissioning tests specified above. These checks are related to functional and operational conditions within transformer elements as well as external interfaces so that transformer can perform successfully in a transmission system. 1.

All the test results of unit are verified and compared with factory results before commissioning.

2.

No leakage of oil in any part of unit.

3

Ensure external electrical clearance of conductor jumpers in the switchyard with transformer body, gantry, column, jumpers, fire wall etc.

4.

Ensure that tertiary winding terminals are insulated, when they are not used / connected to any system.

5.

Ensure earthing of Neutral, main tank body, radiator frame structure, fans and motor.

6. Neutral earthing flat of suitable size must run through support insulator and connected to two separate earthing pits which are in turn connected to main earth mat of switchyard. 7.

Ensure that conductor jumpers connected to HV, LV and tertiary terminals are not tight and should have the allowance for contraction. Also ensure that connectors are properly erected with tightness at bushing terminal.

8. Ensure that R.Y.B designated terminals of transformer are matching with R,Y,B buses of switchyards on HV and LV side. 9.

Ensure oil level in the Bushings.

10. Ensure continuity of OLTC operation at all taps. 11. In a transformer bank of three single phase units, ensure master- slave OLTC scheme. 12. In a transformer bank of three single phase units, ensure tertiary connection and protection scheme. 13. Ensure oil filling in conservator tank according to temperature scale in MOG and also ensure oil level in prismatic glass. 14. Ensure that all valves between main tank and radiator banks are opened. 15. Ensure those radiator valves connected to header are open. 16. Ensure that valve to conservator tank via Buchholz relay is open. 17. Ensure physical operation of local protections like Buchholz, PRV, Surge relay of OLTC etc. 18. Ensure OTI and WTI settings of fan & pumps operation, Alarm and Trip as per approved drawings. Fan and pump operation shall be ensured locally and remotely.

POWER TRANSFORMER - STANDARDISATION MANUAL

19. Review and ensure protection scheme of power transformer with over all protection scheme at remote end in control room. §§

Differential Protection

§§

Restricted Earth Fault Protection.

§§

Over current and Earth fault protection.

§§

Over fluxing Protection.

§§

OTI & WTI- alarm and trap

§§

RTCC panel interface with protection system

§§

Local protection like Buchholz, PRV etc.

§§

Integration of on-line condition monitoring equipments.

20. Ensure the common earthing of tank, frame and core provided in transformer. 21. Ensure the shorting of spare cores of bushing CT’s. 22. Ensure that cap in the tan delta measurement point in the bushing is put back. 23. Ensure Fire Protection System and oil drain valve operation before charging and commissioning. 24. Oil test results after filtration must be within specified limit. 25. Spares like bushings shall be tested and kept ready before charging and commissioning. 26. Allow minimum period of 24 hrs after filtration for oil temperature to settle down. 27. Ensure release of air from plugs provided on top of main tank, conservator and radiator headers. 28. Take charging clearance certificate from all erection agencies for removal of man, material and T&P from site. 29. Ensure healthiness of Air Cell. 30. Ensure availability of oil in the breather cup in main tank/ OLTC tank. 31. Ensure all rollers are locked with rails. 32. Ensure door seals of Marshalling Box are intact and all cable gland plate’s unused holes are sealed. 33. Ensure change over operation of AC supply from source- I to source-II in local master control cubicle.

6

ENERGISATION OF UNIT AND SITE CLOSING Commissioning of transformer is not complete unless it is put into regular service. Following activities to follow:1.

Initially charge the transformer under no load and keep it energize for 24 hrs.

2.

Gradually load the transformer observing the noise, vibration, temperature rise, oil leakage etc.

3.

Check OLTC operation.

4.

Carry out Thermo vision scanning of HV/LV terminals and tank body.

5.

Carry out DGA test of oil as per schedule given in flow chart of this manual

6.

Hand over testing and commissioning records to operation staff along with O&M manual of OEM.

7.

Ensure closure of project by clearing site in all respect particularly removal of temporary sheds, T&P, Oil and handing over spares to customer as per contract.

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POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 6 Transformer Oil

Working Group Members Mr. S. K. Negi

- GETCO

Mr. Atul Shah

- Raj Petro Specialties

Dr. C. Narasimhan

- Savita Oil Technologies Ltd.

Mr. Vinod K. Rishi

- Savita Oil Technologies Ltd.

Mr. Sanjay Abhyankar - Apar Industries Ltd. Mr. Arjun Lad

- Nynas Naphthenic Pvt. Ltd.

Mr. Abhijit Sen Roy

- Indian Oil Corporation

Mr. Nalin Nanavati

- Raj Petro Specialties

Mr. D. V. Jagannathan - Apar Industries Ltd.

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POWER TRANSFORMER - STANDARDISATION MANUAL

CHAPTER - 6

TRANSFORMER OIL INTRODUCTION Transformer oil is like a blood in human body. Once power transformer is charged and commissioned, transformer oil becomes a key element to monitor the healthiness of unit and DGA is one of the important tools to predict probable fault developing in unit as well as analyse insipient trippings. In service, it is continuously performing the role of insulation under electric stress and cooling medium. In India, the production technology, sourcing of petroleum crude and chemistry have undergone drastic changes in last 5 decades and today we have fairly good understanding of our requirement based on field experience. Standardisation Committee thoroughly deliberated on various aspects and has come out with universally acceptable data-sheet of transformer oil specification, which could be easily produced and will perform in Indian weather conditions. It is nevertheless, important to note that transformer oil alone can’t perform unless designer takes care of following key points: 1.

Design of cooling system to keep temperature rise under control.

2.

Correct quantum of oil depending upon voltage and MVA rating of transformer.

3.

To plug all probabilities of moisture ingress in transformer – Air-cell/ silica-gel breather/ Sealing System.

4.

To confirm that oil does not react with any insulation material used in transformer.

5. Characteristics of oil for ageing must be studied in advance depending upon application of transformer in a system. 6.

To take feedback from users on similar oil provided to other units in past for similar application.

The above key points must be covered in design review exercise.

Data Sheet As per Annexure - 6.I and testing of oil as per specified standard is mandatory.

Pre-Commissioning Checks 1.

Mode of transport and method of supply is important. Manufacturers and customers have to mutually agree on this. In case of bulk supply in tankers, due care is required to ensure that tanker is chemically neutral inside and sealed firmly for final inspection at its destination. In case, it is supplied in drums, it is to be ensured during usage that drum seal is intact.

2.

Transformer oil received at site in tanker must be unloaded to another tank through filter machine only. Its BDV and PPM value for water content must be verified to ascertain that there was no infringement during transportation.

3. Transformer oil received in drums must be stored on an elevated platform. Drums are to be horizontally placed with its opening cap in middle. 4.

Before filling oil in transformer through filter machine, it has to be filtered separately in oil tanks and ensure BDV and PPM value.

5.

During filtration, temperature of oil must remain within 60°C.

6.

Excessive filtration of oil must be avoided. In case BDV and PPM values are not achieved within 7 days, check the entire process thoroughly.

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ANNEXURE 6.1 IEEMA STANDARD SPECIFICATION FOR TRANSFORMER OIL (for 132 KV & ABOVE CLASS UP TO 765 KV) Sr. No.

Characteristics of Transformer Oil

Requirement

1

Appearance

The oil shall be clear transparent & free from suspended matter of sediments.

2

Density, gm/cm3 - at 29.5 0C maximum - at 20 0C

0.89 0.895

Kinematic Viscosity, in CST (sqmm/sec) - at 40 0C, maximum - at -20 0C, maximum

12 1800

3

4

Flash Point, 0C minimum Penskey-Marten (Closed)

135

5

Interfacial Tension at 27 0C Newton/M, minimum

0.04

6

Pour point, maximum

- 30 0C

7

Neutralization Value Total acidity mg KOH/gm, maximum

0.01

8

Corrosive Sulphur (In terms of classification of copper strip+paper)

Not corrosive

9

Total Sulphur Content % w/w

< 0.15

10

Electric Strength (Break down voltage) New Untreated Oil After treatment

30 kV minimum (rms) 70 kV minimum (rms)

Dielectric Dissipation Factor (Tan delta) at 90 0C

0.002 maximum

Oxidation Stability1 after 500 Hrs. @ 120 0C, Max Total Acidity in mg KOH/gm maximum Total sludge % by weight maximum DDF at 90 0C

0.3 0.05 0.02

Presence of Anti Oxidation Inhibitor (Additive), Minimum Maximum

0.25 % 0.4 %

Water Content PPM (maximum) As delivered

< 30 (in bulk); < 40 (in drum)

11 12

13

14

Method of Test

Visual. (A representative sample of the oil shall be examined in a 100 mm thick layer, at ambient temperature.)

IS: 1448 P16 ISO 3675 / ISO 12185

ISO 3104

ISO 2719 ISO 6295 IS: 1448 P:10 / ISO 3016 IEC:62021-1 or 2

IEC 62535 (1500C for 72 hrs) BS 2000 Part 373 or ISO 14596

IEC 60156

IEC:60247

IEC 61125 (method C)

IEC:60666

IEC 60814

POWER TRANSFORMER - STANDARDISATION MANUAL

Sr. No.

Characteristics of Transformer Oil

Requirement

Method of Test

15

Poly Chlorinated Biphenyls (PCB) Content

Not detectable (< 2 PPM)

16

Poly Cyclic (PCA) content, maximum

3%

17

2 FAL/ Furans, ppm

< 0.1

18

Impulse Breakdown Voltage Test

> 145 kVp

IEC 61619 BS 2000 part 346 IEC 61198 ASTM method D 3300

Note:

1) In case utility decides to adopt uninhibited oil, only following change shall be applicable. Sr. No.

Characteristics of Transformer Oil

Requirement

12

Oxidation Stability after 164 Hrs. @ 120 0C, maximum a) Total Acidity in mg KOH/gm maximum b) Total sludge % by weight maximum c) DDF at 90 0C

1.2 0.8 0.05

2)

Method of Test IEC 61125 (method C)

In case of inhibited oil, content of additives shall be monitored by user at regular intervals and if depletion is observed below specified limit, corrective action shall be taken to prevent transformer risk in future.

3) P N A content shall be taken as finger print value by oil supplier and shown in acceptance test report. 4) When pour point (maximum) has been decided as (-30 0C), Lowest Cold Start Energizing Temperature shall be (-20 0C).

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POWER TRANSFORMER - STANDARDISATION MANUAL

Chapter - 7 Design Review

Working Group Members Mr. M. Vijayakumaran – ALSTOM Ltd Mr. S. K. Negi

– GETCO

Mr. Y. V. Joshi

– GETCO

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CHAPTER - 7

DESIGN REVIEW 1. INTRODUCTION

A design review is a planned exercise to ensure that both parties understand the application and the requirements of the applicable standards and specification. It is the opportunity for both parties to scrutinize the proposed design to ensure that the requirements will be met not only technical requirements but also those relating to other aspects of the contract, like quality. The whole emphasis of a design review is directed at establishing what is being provided is fit for purpose in all respects for the intended performance in service and that the manufacturer uses proven materials, design tools, methodology and experience to assure the product will meet this requirement, also in all respects.



Design reviews implies also to strengthen the relationship between the purchaser and manufacturer and a good opportunity for the purchaser to better understand the technical capabilities of the manufacturer and for the manufacturer to understand the need of their customers for the sake to have products adapted to their needs. Hence the design review is a good opportunity to interchange experiences that can be used to propose enhancements or betterments. For these reasons it is strongly advisable for the purchaser to have expert transformer engineer(s) with them during the meeting.



A design review, initiated and chaired by the purchaser should be held for the purpose of conducting an indepth review of the ordered Power Transformer and to allow the purchaser to have a clear understanding of the transformers design, manufacture and test including the likelihood of operating in service as intended.



The following are the pre-requisites for carrying out the design review: 1.

It is desirable to have vendor assessment of the manufacturer before placement of order.

2. Design review should be part of the tender inquiry and it becomes obligatory on the part of the customer and manufacturer to ensure compliances with the contract specifications. 3. It is to be ensured that all stake holders are involved in the design review. The designer both mechanical and electrical, ultimate user, production head and if possible, sub vendor also could be invited for the design review. Agenda is to be prepared by customer and sent to manufacturer well in advance. 4. Review may include certain informations which are of proprietary nature. It is, therefore, desirable to have mutual agreement between the purchaser and the manufacturer for the confidentiality of information. 5. It is important for the success of design review that both the purchaser and manufacturer are clear on the requirements and well prepared to have open and frank sharing of information. 2.

OBJECTIVES OF DESIGN REVIEW



Both the purchaser and manufacturer must understand that following objectives are met during the design review: 1.

To ensure that there is a clear and mutual understanding of the transformer technical requirements according to purchaser specification and applicable industry standards.

2. To understand the application and verify the system and project requirements and to indicate areas where special attention may be required.

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3.

To verify that the design complies with the technical requirements.

4.

To identify any prototype features and evaluate their reliability and risks.

5. To interchange experiences that can be used to identify eventual betterments in the design and / or improvements and changes in the specification. 6.

To better understand the technical capabilities of the manufacturer.

7.

To strengthen the technical relationship between purchaser and manufacturer and eventually to improve and go deep in the transformers design knowledge by some participant on the purchasers side.

3.

ELEMENTS OF DESIGN REVIEW



Having understood the purpose of design review and objectives, it is important to know the various elements of design review which will clear all the doubts about the functionality (application), soundness of designs with margins, selection of material and components and also specific operating requirements for its designed life. They are broadly as follows:

S. No.

Elements

1.

System data

2.

Environmental data

3.

Transformer parameters

4.

Transformer design

5.

Transformer ancillaries and accessories.

6.

Transformer oil

7.

Fabrication

8.

Testing

9.

Name plate

10.

Transportation

11.

Site erection, testing & commissioning

12.

Health and safety equipments

13.

Contract documents and drawings

14.

Document submission time scale

POWER TRANSFORMER - STANDARDISATION MANUAL



Design review guidelines of Cigre WGA2.36 (Technical brochure 204) have elaborated above elements in detail as under: Sr. No.

Elements of design review

Check Points

1.

System data

System Voltage Variations Tap changers System Frequency Variation System Short Circuit Capacity System Switching and Transformer Protection High Frequency Transients (HFT) Voltage Transients Current Harmonics Geomagnetic Induced Currents

2.

Environmental data

Ambient temperature range, rate of change of temperature and effect on the overload capability Lowest Cold Load Start-up (LCLS) Solar radiation Site altitude Humidity Pollution Seismic zone and response spectra Geomagnetic currents Ultraviolet (UV) radiation Isoceraunic level

3.

Transformer parameters

Alternating Current Terminal Voltages Insulation Levels – line to line and line to ground Winding Impedances Cooling Provisions Temperature Limits Short Circuit Withstand Capability Cable Connection Bushings and Isolated Phase Bus Bar Connections Sound Levels Losses – No load and load losses Excitation High Temperature Design

4.

Transformer design

Core Windings Thermal design The short circuit capability Core, Winding Assembly and Drying Leads and Cleats Insulation Design Leakage Flux Control Drying and Processing Sound Level Seismic

5.

Transformer ancillaries and accessories.

Bushings Bushing and Internal Current Transformers Tap Changers Internal Surge Arresters Control Cabinet and External Cabling Online Monitoring Equipment

6.

Transformer oil

Review as per exclusive Chapter 6 of this Manual.

7.

Fabrication

General Construction External Cooling Equipment Conservators/Preservation Systems Fabrication Drawings Gas Collection System Design Surface Preparation and Planning

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Sr. No.

Elements of design review

Check Points

8.

Testing

As per Annexure - 7.1

9.

Rating Plate

As per figure 7.1

10.

Transportation

Transportation Plan and Handling Design for Transport Transportation Shipping Profile Transportation Routing Transportation Shipping Impact Withstand Fixtures on Transformer Marking of Center of Gravity Ship and Barge Issues Rail Car Issues Road Transport Issues Transportation monitoring management of transformer Transportation of transformer accessories, components removed from the transformer Acceptance criteria for receiving transformer Transformer Unloading to Foundation

11.

Site erection, testing & commissioning

As per the exclusive Chapter 5 of this Manual.

12.

Health and safety

As per guideline and policy of customer. Also refer Chapter - 5 on Erection, Testing and commissioning of this Manual.

13.

Contract documents and drawings

As per Annexure - 7.2.

14.

Document submission time scale

As agreed between purchaser and manufacturer.

Design review does not absolve or substitute manufacturer’s ultimate responsibility for the adequacy of transformer design and construction, including design limits and margins, quality, performance on test and in service.

POWER TRANSFORMER - STANDARDISATION MANUAL

REFERENCES The following list may be referred, but this is not a limitation on referring to other standards and codes as long as it serves the purpose for effective design review. IEC 60044: Current Transformers. IEC 60050: International Electrotechnical Vocabulary – Chapter 421: Power Transformers and Reactors. IEC 60060-1: General Definitions and Test Requirements. IEC 60071-1: Insulation Coordination - Part 1: Definitions, Principles and Rules. IEC 60071-2: Insulation Coordination - Part 2: Application Guide IEC 60076-1: Power Transformers - Part 1: General. IEC 60076-2: Power Transformers - Part 2: Temperature Rise. IEC 60076-3: Power Transformers - Part 3: Insulation Levels and Dielectric Tests. IEC 60076-5: Power Transformers - Part 5: Ability to withstand Short-Circuit. IEC 60076-6: Power Transformers - Part 6: Reactors IEC 60076-7: Power Transformers - Part 7: Loading guide for oil- immersed Power Transformers. IEC 60076-8: Power Transformers - Part 8: Application Guide for Power Transformers. IEC 60076-10: Power Transformers - Part 10: Determination of Transformer and Reactor Sound Levels. IEC 60076-11: Power transformers - Part 11: Dry-type transformers IEC 60076-18: Power transformers - Part 18: Measurement of frequency response IEC 60076-16: Power transformers - Part 16: Transformers for wind turbine applications IEC 60137: Bushings for Alternating Voltage Above 1000 V. IEC 60214-1: Tap-Changers - Part 1: Performance requirements and Test Methods. IEC 60214-2: Tap-Changers - Part 2: Application guide. IEC 60270: High-voltage test techniques - Partial discharge measurements IEC 60296: Fluids for Electro-technical applications - Unused mineral insulating oils for transformers and switchgear IEC 60815-1: Selection and dimensioning of high-voltage insulators intended for use in polluted conditions - Part 1: Definitions, information and general principles IEC 60815-2: Selection and dimensioning of high-voltage insulators intended for use in polluted conditions - Part 2: Ceramic and glass insulators for a.c. systems IEC 62032: Guide for the Application, Specification and Testing of Phase-Shifting Transformers Other documents of relevance are: ISO 9001: Quality System – Model for Quality Assurance in Design/Development. CIGRÉ TB 209: Short Circuit Performance of Power Transformers CIGRÉ TB 528: Guide for Preparation of Specifications for Power Transformers CIGRÉ TB 530: Guide for Conducting Factory Capability Assessment for Power Transformers.

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A

B

C

D

E

10

400 10

1

1

XXX Transformer Pvt. Ltd. 315 MVA 400/220KV AUTO TRANSFORMER REF. STANDARDS

ONAN/ONAF/OFAF

COOLING RATING

(HV-MV)

MVA 189/252/315

FREQUENCY

(LV)

MVA 63/84/105

PHASES.

FULL LOAD CURRENT

BASIC INSU. LEVEL LI/SI/P.F.

HV

V

400000

MV

V

220000

IMPEDANCE VOLTAGE. HV-MV(315MVA BASE)

33000

V

HV

A 272.79/363.73/454.66

VECTOR GROUP REF.

MV

A 495.99/661.32/826.66

CORE MASS

LV

A 1102.21/1469.61/1837.02 kV 1300/1050/630

MV

kV 1050/-/460

LV

kV

250/-/ 95

Neutral

kV

95/-/ 38

OIL

°C

50°C at ONAN 55°C at ONAF/OFAF

°C

55°C at ONAN 60°C at ONAF/OFAF

VECTOR GROUP YNa0d11

2U 3U 3V

N

1V

2

2

MV

2V 3W

1W

1

2

1

1

MV WTI

2V1S1 2V1S2 2V1S3 2V1S4 2V2S1 2V2S2 2V2S3 2V2S4

CT1W

1V1S1 1V1S2 1V1S3 1V1S4 1V2S1 1V2S2 1V2S3 1V2S4

3W1S2

1W

CT2V

CT1V

CT2U

CT1U

2U1S1 2U1S2 2U1S3 2U1S4 2U2S1 2U2S2 2U2S3 2U2S4

3W1S1

1

1W1S1 1W1S2 1W1S3 1W1S4 1W2S1 1W2S2 1W2S3 1W2S4

2W1S1 2W1S2 2W1S3 2W1S4 2W2S1 2W2S2 2W2S3 2W2S4

kg.

MASS OF TOTAL OIL (WITHOUT 10% EXTRA OIL)

kg.

10% EXTRA OIL

kg. kg.

QUANTITY OF OIL IN OLTC

Ltrs.

TRANSFORMER OIL QUANTITY (WITHOUT 10% EXTRA OIL)

Ltrs. CUSTOMER CHOICE

3 4 5 6 7 8 9 10 11 12

12

3 4 5 6 7 8 9 10 11 12

4 3

12

CTNBF

VN1S4 VN1S3 VN1S2 VN1S1 VN2S4 VN2S3 VN2S2 VN2S1

OFAF 315 MVA

440000

330.66

413.33

2

13 - 11

435000

250.84

334.46

418.08

3

13 - 10

430000

253.76

338.35

422.94

4

13 - 9

425000

256.75

342.33

427.91

5

13 - 8

420000

259.80

346.41

433.01

6

13 - 7

415000

262.93

350.68

438.22

7

13 - 6

410000

266.14

354.85

443.57

8

13 - 5

405000

269.43

359.24

449.05

9a

13 - 4

400000

272.79

363.73

454.66

9b

13 - 3

400000

272.79

363.73

454.66

9c

13 - 12

400000

272.79

363.73

454.66

10

13 - 11

395000

276.25

368.33

460.41

11

13 - 10

390000

279.79

373.05

466.32

12

13 - 9

385000

283.42

377.90

472.37

13

13 - 8

380000

287.15

382.87

478.59

14

13 - 7

375000

290.98

387.97

484.97

15

13 - 6

370000

294.91

393.22

491.52

16

13 - 5

365000

298.95

398.60

17

13 - 4

360000

303.10

404.14

3-4

3-12

VOLTAGE

L.V

CURRENT VOLTAGE

(V)

220000

(A)

ONAN 495.99 ONAF 661.32 OFAF 826.66

(V)

33000

CURRENT

(A)

ONAN 1102.21 (@63MVA) ONAF 1469.61 (@84MVA) OFAF 1837.02 (@105MVA)

498.26

RATIO AMP.

CORE NO.

ACC. CLASS

BURDEN (VA)

505.18

kpV (Volt)

Imag at Vk/2

@2000/1ATap

(in mA)

>

MAX SEC.RES.

(OHM) @2000/1ATap

1

500-1000-2000/1

PS

-

2000

30

10

CT1W

2

500-1000-2000/1

PS

-

2000

30

10

CT2U

1

500-1000-2000/1

PS

-

2000

30

10

2000

30

10

CT2V

CTNBF

WN1S4 WN1S3 WN1S2 WN1S1 WN2S4 WN2S3 WN2S2 WN2S1

CT2W

2

500-1000-2000/1

PS

-

CTNBF BEFORE NEUTRAL FORMATION

1

500-1000-2000/1

PS

-

2000

30

10

2

500-1000-2000/1

PS

-

2000

30

10

1

500-1000-2000/1

MEASURED (KW)

TERMINAL MARKING 1U1S1-1U1S2-1U1S3-1U1S4 1V1S1-1V1S2-1V1S3-1V1S4 1W1S1-1W1S2-1W1S3-1W1S4 1U2S1-1U2S2-1U2S3-1U2S4 1V2S1-1V2S2-1V2S3-1V2S4 1W2S1-1W2S2-1W2S3-1W2S4 2U1S1-2U1S2-2U1S3-2U1S4 2V1S1-2V1S2-2V1S3-2V1S4 2W1S1-2W1S2-2W1S3-2W1S4 2U2S1-2U2S2-2U2S3-2U2S4 2V2S1-2V2S2-2V2S3-2V2S4 2W2S1-2W2S2-2W2S3-2W2S4 UN1S1-UN1S2-UN1S3-UN1S4 VN1S1-VN1S2-VN1S3-VN1S4 WN1S1-WN1S2-WN1S3-WN1S4 UN2S1-UN2S2-UN2S3-UN2S4 VN2S1-VN2S2-VN2S3-VN2S4 WN2S1-WN2S2-WN2S3-WN2S4

Application

REF.

Differential

REF.

Differential

REF.

Differential

PS

-

2000

30

10

2

500-1000-2000/1

PS

-

2000

30

10

HV WTI

1

506/2

5

15

-

-

-

1U3S1-1U3S2

MEASURING

MV WTI

1

827/2

5

15

-

-

-

2V3S1-2V3S2

MEASURING

TV WTI

1

1837/2

5

15

-

-

-

3W1S1-3W1S2

MEASURING

TMS CT

1

827/1

5

5

-

-

-

2U3S1-2U3S2

MEASURING

CTN

TYPE OF OIL : VACUUM WITHSTAND CAPABILITY 760 Hg OLTC RATING & MAKE: GTD.(KW)

ONAF 252 MVA

247.99

N1S1-N1S2-N1S3-N1S4 N2S1-N2S2-N2S3-N2S4

6

6

UN1S4 UN1S3 UN1S2 UN1S1 UN2S4 UN2S3 UN2S2 UN2S1

ONAN 189 MVA

2

2

2

M.V.

(V)

CT1V

13

13

13

VOLTAGE

1

3 4 5 6 7 8 9 10 11 12

4 3

H.V. CURRENT(A)

13 - 12

CT1U

TO OLTC

1

CTNBF

TANK & FITTINGS MASS

1

CT

1W3S1

4

kg.

2V3S2

1V

CT2W

2U3S2

1W3S2

HV

3U 3V 3W

2V3S1

1U

TV WTI

2W

2U3S1

12

kg.

TRANSPORTATION MASS

5

5 2V

2U

3

CORE & COIL MASS

PRE OLTC TAP CONECTION SELEPOSN. IN EACH CTOR NO. POSI. PHASE

2W

HV WTI

kg.

4

4

600

1U

CTN

kg.

MV

PAINT SHADE

PO . NO. & DATE

1U1S1 1U1S2 1U1S3 1U1S4 1U2S1 1U2S2 1U2S3 1U2S4

HV

3

WORK ORDER NO.

N1S1 N1S2 N1S3 N1S4 N2S1 N2S2 N2S3 N2S4

YNa0d11 kg.

TOTAL MASS

YEAR OF MANUFACTURE

TMS CT

%

REG kg.

MAKER'S SR. NO.

1N

%

COPPER MASS (BARE)

HV

WDG

TAP.NO.1 TAP NO.9

TAP NO.17 %

LV

3

GTD. TEMP. RISE

50 3/3

2

2

RATED VOLTAGE

IS:2026

Hz

>

268

REF. REF.

NOISE LEVEL: ________dB

NO LOAD LOSS LOAD LOSS STRAY LOSS AUXILLIARY LOSS

TAN DELTA OF WINDING : ________% MOISTURE CONTENT IN ACTIVE PART : ________% of wt.

PROPERTY OF CUSTOMER NAME 7

7

6-Ø6 Holes. TYPICAL RATING PLATE FOR POWER TRANSFORMER A

B

C

D

E J

Fig. 7.1: Typical Rating Plate

POWER TRANSFORMER - STANDARDISATION MANUAL

ANNEXURE 7.1 TESTING Sr. no.

Tests, measurements & checks

1

Dimensions, fittings and equipment

2

Turns ratio

3

Polarity & phase relationship

4

Insulation resistances

5

Winding resistances

6

Insulation power factor

7

Capacitances

8

Load loss & impedance voltage

9

Impedance characteristic across tap range

10

Zero-phase-sequence impedance

11

No-load loss & magnetizing current

12

Audible sound

13

Temperature rise

14

Gas in oil analyses

15

Lightning impulse voltage tests

16

Switching impulse voltage tests

17

Applied voltage tests

18

Induced voltage test & partial discharge

19

Single-phase magnetizing current test

20

Oil pressure

21

Control system, components, instruments

22

Ancillary equipment power losses

23

CT checks

24

RSO

25

Frequency Response Analysis (FRA)

26

Tap changer

27

Secondary wiring insulation resistances

28

Oil samples

29

Inventory

30

Contract documents

31

QA records

269

270

POWER TRANSFORMER - STANDARDISATION MANUAL

ANNEXURE 7.2 Contract Documents and Drawings for approval

Sr. No.

Documents

1

Contract drawings Certificates a. ISO Quality Assurance b. ISO Environmental c. OHSAS

2

Product Source Schedule

3

Production Plan & Reporting Programme

4

Design Review Minutes

5

Quality System

6

Quality Plan

7

Test Plan

8

Factory Acceptance Test (FAT) Reports

9

Transport Plan

10

Transformer Site Commissioning Plan

11

Method Statements

12

Risk Assessments

13

Training

14

Site Works

15

Site Contractor(s) & Supervision.

16

Site Tests

17

Operation & Maintenance Manuals