19 Ret 670 Ied.pdf

Gunnar Stranne

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ABB Power Technologies AB, 2005

Rio de Janeiro April 23-25, 2006

2006-04-20 PTSX Gunnar Stranne

Transformer protection IED RET 670

Transformer protection IED RET670 Introduction – features and applications Differential protection functions Restricted Earth Fault protection function High Impedance Differential protection function Some additional functions and application examples

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ABB Power Technologies AB, 2005

Preconfigured ready-made packages Summary and conclusions

2006-04-20 PTSX Gunnar Stranne 2

Benefits of RET670 – outstanding features Half cycle operating time – a new performance standard! One or two differential functions Differential function compensated automatically for tap changer position for improved sensitivity An additional sensitive and fast differential function based on negative sequence current - ~1% sensitivity High impedance or low impedance restricted earth-fault differential protection for each winding Possibility to use multi - CT arrangements for increased differential protection stability Tap changer control

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ABB Power Technologies AB, 2005

Breaker control , measuring, monitoring and recording

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Applications Power transformers, including autotransformers, reactors and generator transformer blocks Two or three vector group (or winding) transformers Single- or multi circuit breaker arrangements

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ABB Power Technologies AB, 2005

Up to six stabilized 3-phase current inputs

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Three-winding Transformer Three-winding variant up to 6 restraint three-phase CT inputs Ensures enhanced throughfault stability for multibreaker arrangements

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ABB Power Technologies AB, 2005

Tap changer control

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Auto Transformer Phased segregated biased differential protection for Autotransformers in 1½ CB applications Serial and common windings

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ABB Power Technologies AB, 2005

Up to 4 three-phase CT inputs

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Phase Shifting Transformer Transformer key data 1400 MVA 400/ 400 kV +-25° 1200 tons 32 MUSD contract

Project aspects Cooperation between End User, Relay Manufacturer & PST Manufacturer is of outmost importance

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ABB Power Technologies AB, 2005

Cooperation required in the very early design stage of the project

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Shunt Reactor Protection And Control Protection Phase segregated biased differential protection High-impedance differential protection Over/under-voltage protection

Switching control for lines and busses

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ABB Power Technologies AB, 2005

RET 670 is optimized for each application with maximum reliability and short operating time 2006-04-20 PTSX Gunnar Stranne 8

Step-up Transformer In Power Stations Overall differential protection of a generator – transformer unit Differential protection for the step-up transformer and/or the auxiliary transformer

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ABB Power Technologies AB, 2005

Back-up protection functionality

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Complementary Protection Functions Full scheme distance Overcurrent – 19 inverse Thermal overload Breaker failure Voltage functions with high reset ratio

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ABB Power Technologies AB, 2005

RET 670 fits all power system elements that require unit and additional protection functionality

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Differential Protection Two-winding or three-winding functions Two-winding variant up to 4 three-phase CT inputs Enhanced through-fault stability for multi-breaker arrangements

Three-winding variant up to 6 three-phase CT inputs

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ABB Power Technologies AB, 2005

Enhanced through-fault stability for multi-breaker arrangements

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Transformer Protection Terminal Differential Protection of 2- winding Power Transformers 2- winding power transformer 2- winding power transformer with unconnected delta tertiary winding 2- winding power transformer with 2 circuit breakers on primary side 2- winding power transformer with 2 circuit breakers on secondary side

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ABB Power Technologies AB, 2005

- winding power transformer with 2 circuit breakers on both sides 2006-04-20 PTSX Gunnar Stranne 12

Transformer Protection Terminal Differential Protection of 3- winding Power Transformers 3- winding power transformer with all 3 windings connected 3- winding power transformer with 2 circuit breakers on (any) one side, (e.g. 2 parallel power lines on one side)

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ABB Power Technologies AB, 2005

3- winding power transformer with 2 circuit breakers on 2 out of 3 sides, (e.g. a meshed power network) Note! Also 3-out of 3 with 2 breakers is possible. 2006-04-20 PTSX Gunnar Stranne 13

Differential Protection A differential current does not always mean there is a fault in the transformer Inrush current in power transformers Saturation of current transformers Overexcitation Tap changer position etc.

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ABB Power Technologies AB, 2005

Means of coping with these situations must be included in the design

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Differential Protection Ability is included to handle two tap changers, i.e. one tap changer per winding on any two windings Functionality Three-section settable restrain characteristic High set unrestrained operation Idiff Idunre

Unrestrained operation

operate

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ABB Power Technologies AB, 2005

1.0 pu restrain

Idmin 1.25 pu 2006-04-20 PTSX Gunnar Stranne 15

Ibias

Transformer Inrush Current Stabilization Second harmonic stabilisation Wave form stabilisation wave block

CT saturation cause a second harmonic component in the secondary current

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ABB Power Technologies AB, 2005

Transformer inrush currents contain a percentage of second harmonic current. This is used for discrimination but second harmonic blocking normally causes delayed operation in case of CT saturation. It is also possible to monitor the shape of the differential current signal. The low-current gap measurement indicates inrush. 2006-04-20 PTSX Gunnar Stranne 16

Transformer Inrush Current Stabilisation Internal fault followed by CT saturation

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ABB Power Technologies AB, 2005

Delayed trip of the restrained differential function due to the traditional use of second harmonic blocking (Set level 15 %)

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Overvoltage Stabilization The fifth harmonic component is used for stabilization

Magnetizing current at system overvoltage

3

iL1

2

iL2

1

iL3 0

-1 -2 -3

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ABB Power Technologies AB, 2005

The fifth harmonic component appears as a characteristic quantity in the transformer magnetizing current during overvoltage.

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Differential Protection DIFP- application

Two- and three winding applications Stabilization of up to 6 inputs Inrush current stabilization Second harmonic Waveform Phase segregated Selectable ”Cross-blocking” 5th harmonic stabilization at overvoltage

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ABB Power Technologies AB, 2005

Sensitivity influenced by tap changer position (selectable) Selectable subtraction of zero sequence currents 2006-04-20 PTSX Gunnar Stranne 19

Differential Protection Blocking condition: 2nd harmonic, 5th harmonic waveblock, cross block Neg Seq Int / internal Ext Fault Discriminator sensitive

restrained

&

&

≥1

TRIP

unrestrained

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ABB Power Technologies AB, 2005

START

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Differential Protection

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ABB Power Technologies AB, 2005

Testing RET670 for maximum performance Fault detection in 7 ms!

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Negative sequence current differential function Internal / external fault discriminator

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ABB Power Technologies AB, 2005

Based on the measurement of negative sequence current

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Negative sequence current differential function Before comparison, all negative sequence currents are compensated for turns ratio and vector group phase displacement External fault: 180°relative phase displacement Internal fault: 0°relative phase displacement

IminNegSeq 2% - 20% Default 4%

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ABB Power Technologies AB, 2005

NegSeqROA 30°– 120° Default 60°

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Negative sequence current differential function An internal fault with heavy CT saturation Directional Comparison Criterion: Internal fault as seen from the HV side 90

excursion from 0 degrees due to CT saturation

60

120 35 ms

30

150

180 external fault region

0

0.5 kA

210

330 1.0 kA

ABB Power Technologies AB, 2005

©

definitely an internal fault

240

300 1.5 kA

trip command in 12 ms Internal fault declared 7 ms after internal fault occurred

270 HV side contribution to the total negative sequence differential current in kA Directional limit (within the region delimited by ± 60 degrees is internal fault) 2006-04-20 PTSX Gunnar Stranne 24

Negative Sequence Differential Protection An internal small transformer interturn fault was cleared by Buckholz relay and existing differential protection failed to detect fault Test of RET 670 with recorded signals proved successful Directional Comparison Criterion: Internal fault as seen from the HV side 90

If one or the other of currents is too low, then no measurement is done

60 (negSeqROA = ± 60 deg)

120

150

30

8

180 External fault region

20 A

210

10

19

0

330

steady-state position for this internal fault Internal fault declared 12 ms after fault

30 A 40 A

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ABB Power Technologies AB, 2005

240

50 A

300 270 Contribution to total neg. seq. diff. current from HV side (in A) Directional limit (within ± negSeqROA degrees is internal fault)

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Negative sequence current function - summary Fast operating times – half cycle Start from ordinary differential protection required, but blocking conditions are bypassed Sensitive negative sequence protection Gives sensitive turn-to-turn fault protection The trip request must be confirmed several times in succession before the final trip request is placed – this security feature causes an increase in the operating time

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ABB Power Technologies AB, 2005

The operating time is about 30ms for very lowlevel turn-to-turn faults This sensitive negative sequence protection is blocked for high fault current conditions 2006-04-20 PTSX Gunnar Stranne 26

Restricted Earth Fault Protection Operate characteristic diff current in pu

minimum base sensitivity 50 % default base sensitivity 30 % maximum base sensitivity 5 %

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ABB Power Technologies AB, 2005

Step : 1 % transformer rated current

0 6

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1

2

1.25 pu

3

4

5

bias current in per unit

Restricted Earth Fault Protection Internal fault

External fault

zone of protection

IL1

IL1

IL2

IL2

IL3

IL3

3I0

IN

IFAULT

IN

IFAULT

zone of protection

IN

3I0

internal fault 3I0

external fault ROA

MTA ABB Power Technologies AB, 2005

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reference is neutral current -IN

operate for internal fault

IN

ROA

restrain for external fault

3I0

ROA

MTA

operate for internal fault

ROA

-IN restrain for external fault reference is neutral current

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Differential Protection Switch-on-to-fault Built-in logic to improve operating speed for switch-on-to-fault condition Possible to record the differential currents and/or bias current by the disturbance recorder channels 31-40 Differential currents Instantaneous or RMS Bias current

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ABB Power Technologies AB, 2005

RMS

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Restricted Earth Fault Protection

3I0 < 3% of Ibase IN > 50% of Idset Directional check

≥1

≥1

TRIP

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ABB Power Technologies AB, 2005

START

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Restricted Earth Fault Protection Up to 4 three-phase CT inputs makes it possible to handle autotransformers in 1½ CB applications Enhanced function for autotransformer applications I1 I2 I3

I3P

I1 I2 I3

I3P

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ABB Power Technologies AB, 2005

I1 I2 I3

I

2006-04-20 PTSX Gunnar Stranne 31

I3P

I1N

REFx I1 I3PRI1 I3PRI2 I3SEC1 I3SEC2

Restricted Earth Fault Protection Switch-on-to-fault Built-in logic to improve operating speed for switch-on-to-fault condition Possible to record differential currents and/or bias current by the disturbance recorder Differential currents Instantaneous or RMS Bias current

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ABB Power Technologies AB, 2005

RMS

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High Impedance Differential Protection Three instances → 1 or 3 high impedance differential External stabilizing resistors & metrosils are used Typical applications High impedance REF – Restricted Earth Fault protection Tee - feeder differential protection

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ABB Power Technologies AB, 2005

Bus differential

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Overexcitation Protection V/Hz measurement Positive sequence or single phase-to-phase voltage Transformer magnetic core cooling time constant setting IEEE inverse time and User defined trip curves available

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ABB Power Technologies AB, 2005

Alarm level as percentage of trip level

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Thermal Overload protection function

49-1 Ith

86/94 I->O

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ABB Power Technologies AB, 2005

49-1 Ith

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•Two thermal overload functions •Tripping of load will give cooling chance to restore normal temperatures. •Settable thermal time constants for short circuits and low overloads •Measures RMS current •Lockout reset level (in % of heat content trip value)

86/94 I->O

Alarm levels 1 and 2 (each in % of heat content trip value)

TOF/TUF/RVF(df/dt) – Frequency Protection Over-frequency and under-frequency Six steps OF & UF – settable frequency and time delay Measures Ph-Ph or Positive sequence voltage Under-voltage blocking Df/dt with positive or negative derivative setting High accuracy Short operating time Accuracy 2 mHz for three phase

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ABB Power Technologies AB, 2005

Accuracy 10 mHz for single phase

Voltage dependent tripping time possible! 2006-04-20 PTSX Gunnar Stranne 36

Frequency Protection - Applications Under frequency Load shedding systems Remedial action schemes

Over frequency Generation shedding Remedial action schemes

Rate-of-change of frequency Generation shedding Load shedding

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ABB Power Technologies AB, 2005

Remedial action schemes

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Six Pre-configured RET 670 - Ready To Use RET 670-A30 Two winding transformer, single circuit breaker RET 670-B30 Two winding transformer, multi circuit breaker (1½ CB or double CB on either, or both, sides of the transformer) RET 670-A20 Three winding transformer, single circuit breaker RET 670-A31 Three winding transformer, single circuit breaker, current and voltage inputs RET 670-A40 Three winding transformer, single circuit breaker (1½ CB or double CB on any, or all, sides of the transformer)

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ABB Power Technologies AB, 2005

RET670 –B40 Three winding transformer, multi circuit breaker (1½ CB or double CB on any, or all, sides of the transformer)

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Two Winding Transformer – Single Circuit Breaker RET 670-A30

DR 50BF 3I>BF 50/51-1 3I> 51N-1

I

86/94 I->O

87N-1 Ind> 87T 3Id/I>

52PD PD

87N-2 Ind>

59N UN

24 U/f>

59N UN

59 3U>

51N-2

50BF 3I>BF

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ABB Power Technologies AB, 2005

25/27 SC/VC

90 VCTR 50/51-2 3I> 59 3U> 27 3U<

60 FF

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DR

O5

O4

O2

27 3U<

I

60 FF

81O/81U f

86/94

21 Z<

I->O Contr Interl

O1

O3

Two Winding Transformer – Multi Circuit Breaker RET 670-B30 25/27

50BF 3I>BF

2* SC/VC

DR 50BF 3I>BF

Σ 51N-1

I

50/51-1 3I>

86/94 I->O

87N-1 Ind> 87T 3Id/I>

ABB Power Technologies AB, 2005

©

SC/VC

2006-04-20 PTSX Gunnar Stranne 40

O6 O4 O5

O2

27 3U<

50/51-2 3I>

86/94 I->O

21 Z<

59 3U> 27 3U<

60 FF

52PD 2* PD

59 3U>

I

25/27

O8

59N UN

51N-2

50BF 3I>BF

2* f

50BF 3I>BF

59N UN

60 FF

81O/81U

24 U/f>

87N-2 Ind>

O7

DR

Contr Interl

O1

O3

Three Winding Transformer – Single Circuit Breaker DR 50BF 3I>BF 50/51-1 3I>

RET 670-A20 86/94 I->O

60 FF 25/27

O6

SC/VC 24 U/f>

O4

51N-3 51N-1

I

50BF 3I>BF

I

87N-1 Ind> 87T 3Id/I>

87N-3 INd>

87N-2 Ind>

59N UN

59N UN

50/51-3 3I>

59 3U>

51N-2

50BF 3I>BF 25/27

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ABB Power Technologies AB, 2005

SC/VC

60 FF 2006-04-20 PTSX Gunnar Stranne 41

50/51-2 3I> 59 3U> 27 3U<

DR

O2

27 3U<

I

60 FF

O5

86/94 I->O 86/94 I->O

21 Z< O1 Contr Interl 81O/81U f 52PD PD

O3

O7

Three Winding Transformer – Multi Circuit Breaker 81O/81U

RET670 –B40 DR

50BF 3I>BF

Σ 51N-1

I

50BF 3I>BF 50/51-1 3I>

86/94 I->O

24 U/f>

87N-1 Ind> 87T 3Id/I>

ABB Power Technologies AB, 2005

©

25/27 SC/VC

59 3U>

42

60 FF

DR

O4

O5

59N UN 59 3U>

27 3U<

2006-04-20 PTSX Gunnar Stranne

87N-3 INd>

I

50/51-2 3I>

O6

I

51N-2

50BF 3I>BF

O8

51N-3

59N UN

60 FF

52PD PD 60 FF 25/27

O7

SC/VC

87N-2 Ind>

50BF 50/51-3 3I>BF 3I>

f

86/94 I->O 86/94 I->O

O2

27 3U< 21 Z<

Contr Interl

O1

O3

Benefits of RET670

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ABB Power Technologies AB, 2005

Functional flexibility Configuration flexibility High performance User friendly Pre-defined packages IED 670 series member means;

Every step you take - ABB has the solution 2006-04-20 PTSX Gunnar Stranne 43

Less spare parts needed Simplified engineering and maintenance Common look and feel and common tools Extensive Self-supervision Remote communication flexibility Easy integration in Substation Automation Systems

Benefits of RET670 – outstanding features Fast, sensitive and secure differential function – tap-changer compensated Fast and sensitive negative sequence differential function -> half cycle operation Multi-CT inputs increases security and functionality High or low impedance restricted earthfault winding differential funcions Extensive function library and options Up to 12 general I -V functions; distance and extra differential functions High reset voltage functions

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ABB Power Technologies AB, 2005

Extendable analog and digital I/O Full control functionality Large HMI option 2006-04-20 PTSX Gunnar Stranne 44