Circuit Breaker

CIRCUIT BREAKERS

•

CIRCUIT BREAKER- FUNCTIONS  CARRIES CURRENT WHEN CLOSED  WITHSTANDS VOLTAGE WHEN OPEN  WITHSTANDS FAULT CURRENTS FOR SHORT TIME  CAN WITHSTANDS CLOSING THE FAULT CURRENT  CAN INTTERUPT LOAD CURRENTS  CAN INTERRUPT FUALT CURRENTS  CAN INTERRUPT SMALL INDUCTIVE & CAPACITIVE CURRENTS WITHOUT CREATING EXCESSIVE OVERVOLTAGES

CIRCUIT BREAKERS CIRCUIT BREAKERS

Interrupting Unit

Mechanism

TYPES OF CIRCUIT BREAKERS

AIR BLAST CIRCUIT BREAKERS

BULK OIL CIRCUIT BREAKERS

MINIMUM OIL CIRCUIT BREAKERS

SF6 CIRCUIT BREAKERS

DIELECTRIC STRENGTH OF SF6 GAS

SINGLE POLE OPERATED OPERATED

GANG

11

LIVE TANK CBS DEAD TANK CBS

INTERRUPTER S

Interrupter

Open position

Interrupting Principle

Closed Position

SF6 CIRCUIT BREAKERS CONTACTS

DIAGRAMMATIC VIEW OF SF6 CB POLE

MECHANISM

Closed Position

Opened Position

Closed Position

Mechanism Housing – 145 / 72 kV SP/SP

Spring Mechanisms 72 / 145 kV - Closing Spring

Spring Mechanism 72/145 kV - Opening Spring (Rear View)

TRIP & CLOSE COIL POSITION

CLOSING MECHANISM- CLOSED VIEW

PHOTOGRAPHS OF DIFFERENT RATING’S CIRCUIT BREAKERS

33 KV CIRCUIT BREAKERS

132 KV CIRCUIT BREAKERS

220 KV CIRCUIT BREAKERS

400 KV CIRCUIT BREAKERS

800 KV CIRCUIT BREAKERS

COMMISSIONING OF CIRCUIT BREAKERS

Gas System

CIRCUIT BREAKER SPECIFICATION S

SOME IMPORTANT TERMS  Transient  Rate

Recovery Voltage

of Rise of Restriking Voltage

 Recovery

Voltage

 Reignition/

Restrike

 Capacitive/Inductive/Resistive  Current  Various

Chopping Timings

Breaking

TYPICAL SYSTEM LUMPED PARAMETER MODEL

CURRENT, TRV AND RECOVERY VOLTAGE

CURRENT AND TRV WAVEFORMS DURING INTERRUPTION OF RESISTIVE CURRENT

CURRENT AND TRV WAVEFORMS DURING INTERRUPTION OF INDUCTIVE CURRENT

RECOVERY VOLTAGE IN CASE OF A CAPACITIVE LOAD

EVOLUTION OF VOLTAGES WITH RESTRIKE OCCURRING A HALF CYCLE AFTER CURRENT INTERRUPTION, IN THE CASE OF SINGLE-PHASE CAPACITIVE CURRENT SWITCHING

CIRCUIT BREAKER WITH MULTIPLE REIGNITIONS

TRV DURING CURRENT CHOPPING

VARIOUS TIMINGS

STANDARD SPECIFICATIONS FOR 145 KV CIRCUIT BREAKER 

Rated Voltage

: 145 kV



Rated Lightning Impulse Voltage

: 650 kVp



Rated Power Frequency Voltage

: 275 kV



Creepage Distance (Total)

: 3625 mm



Applicable Standards

: IEC-62271-100/ IS 13118



Type of Mechanism

: Spring-Spring



Rated Normal Current

: 3150 Amps



Rated Operating Sequence

: O- 0.3 Sec.-CO-3 min.-CO



Rated Frequency

: 50 Hz

STANDARD SPECIFICATIONS FOR 145 KV CIRCUIT BREAKER 

Rated Closing /Tripping Voltage

: 110 VDC



Current of Closing / Tripping Coil

: 6 Amps Max.



Rated Break Time

: 60 mSec.



Rated Closing Time

: 130 mSec.



Rated Short Circuit Making Current

: 80 kA



Rated Short Circuit Breaking Current

: 40 kA



Rated Line Charging Breaking Current

: 50 Amps

STANDARD SPECIFICATIONS FOR 145 KV CIRCUIT BREAKER 

Rated Line Charging Breaking Voltage

: 2.5 Times



Rated Cable Charging Breaking Current

: 160 Amps



Rated Cable Charging Breaking Voltage

: 2.5 Times



Rated Single Capacitor Bank Breaking Current

: 400 Amps



Rated Single Capacitor Bank Breaking Voltage

: 2.5 Times



Rated Out of Phase Breaking Current

: 7.9 kA

STANDARD SPECIFICATIONS FOR 145 KV CIRCUIT BREAKER 

First Pole to Clear Factor

: 1.5



Auxiliary Contacts

: 8 NO + 8 NC



SF6 Gas Pressure at 200C: Normal

: 6 Kg/cm2



SF6 Gas Pressure at 200C: Alarm

: 5.5 Kg/cm2



SF6 Gas Pressure at 200C: Lock Out

: 5 Kg/cm2



Weight

: 1450 Kg.



Seismic Acceleration

: 0.3 g

CONTROL CIRCUITS

VARIOUS CONTROL CIRCUITS 

CB Auxiliary Contacts



Common Ferrules & CB Changing Activity



Semaphore Circuit



ON/OFF Indication Circuit



Spring Charge Control & Indication Circuit



SF6 Alarm & Lockout Circuit



Remote Closing



Antipumping Circuit



Remote Tripping



Post Close & Pre Close Supervision Circuit



PDR Circuit

TEMPERATURE COMPENSATED PRESSURE SWITCH

SERIES RESISTORS FOR REDUCING THE COIL OPERATING VOLTAGE

CB LOCAL/REMOTE & ON/OFF SWITCH

CB OPERATIONAL INDICATORS

TB IN CB MB

AUXILIARY DRUM TB

CB AUXILIARY DRUM

CB Auxiliary Drum

CB MB FRONT VIEW

NUMBERS & SPECIFICATIONS OF VARIOUS ITEMS

Item No.

Nomenclature

52C

Closing Coil

52 T1

Trip Coil

52 T2

Trip Coil

ACTUAL CONTROL CIRCUIT

CLOSING CIRCUIT WITH ANTIPUMPING

SPRING CHARGING CIRCUIT

SF6 CIRCUITS

TROUBLESHOOTI NG

OF CIRCUIT BREAKE RS

CIRCUIT BREAKER TESTING

INSULATION RESISTANCE MEASUREMENT

INSULATION RESISTANCE MEASUREMENT 1. 2. 3. 4. 5.

TOP – EARTH BOTTOM - EARTH TOP – BOTTOM (CB OPEN) TOP – BOTTOM (CB CLOSE) TOP, BOTTOM – EARTH (CB CLOSE)

ACCEPTABLE LIMITS • PHASE TO EARTH : 1000 MΩ • ACROSS OPEN CONTACTS : 1000 MΩ (5/10 kV MEGGER)

DEW POINT MEASUREMEN T

DEW POINT MEASUREMENT SET UP

Sr. No. Make of CB

Dew point Dew point at at rated Atmospheric pressure (Min. º C)

1

2

4

BHEL

CGL

ABB

Pressure

Remarks

(limit) (Min º C)

-15

-36

At the time of commissioning

-7

-29

During O&M

-5

-27

Critical

-15

-35

At the time of commissioning

-10

-31

During O&M

-15

-35

At the time of commissioning

-5

-26

During O&M

OPERATIONAL CIRCUIT AND OTHER CHECKS



POLE DISCREPENCY CHECK



ANTI HUNTING/ PUMPING FEATURE



BREAKER POSITION INDICATOR



REMOTE TRIPPING WITH TC1 & TC2



REMOTE CLOSING



ILLUMINATION IN CB MB



SPACE HEATER IN CONTROL/SWITCH CUBICLE

OTHER CHECKS  COIL

RESISTANCE MEASUREMENT.

 LEAKAGE CHECK OF SF6 GAS.  IR VALUE OF CONTROL CIRCUIT  CB OPERATION COUNTER HEALTHINESS.  OIL/AIR PRESSURE DROP TEST.  OIL/AIR PRESSURE LEAKAGE IN 24 HRS.  SPRING CHARGING TIME.

CIRCUIT BREAKER TIMING TEST

TIMING TEST KIT

TEST LIMITS  Close

(C-operation)

<=150ms

 Open

(O-operation)

<=60ms

 Close-Open

(C-O operation)

<=160ms

CONTACT RESISTANCE MEASUREMENT

STATIC CONTACT RESISTANCE – ACCEPTABLE VALUES: 150

µΩ

DYNAMIC CONTACT RESISTANCE MEASUREMENT

MOVING CONTACT PROBLEMS

ARCING CONTACT PROBLEMS

DCRM CAN DETECT  Erosion of Arcing Contact  Contact

misalignments

 Wipe

of main and arcing contact

 Main

& arcing contact resistance

 Healthiness  Contact

of damping system

travel & speed

DCRM CONNECTION ARRANGEMENT

DCRM KIT

TYPICAL DCRM SIGNATURE

CASE STUDY-1

400 kV GCB AT at Hosur WITH SPRING-PNEUMATIC MECHANISM COMMISIONED IN 2003.

420 kV SF6 GCB With SP/Pneumatic Mechanism

DCRM SIGNATURES OF B PHASE

DCRM SIGNATURES OF R PHASE

DCRM SIGNATURE OF Y PHASE

 Static contact CONTACT RESISTANCE VALUES resistance reported to be about

53 micro-ohm at the time of commissioning  Static

Contact resistance has found to be

87 micro-ohm

Y PHASE DCRM AFTER ADJUSTMENT OF TRAVEL/WIPE

CASE STUDY 2 

CB 952 inspected in March,2006 at Hyderabad s/s.



DCRM of B pole was not alright. The problem is rectified & DCRM taken but found abnormal again.



The Test kit was changed but same problem was indicated in DCRM.



New spare pole was erected but same problem was again indicated.



M/s Scope was called with new kit but problem continued



ABB then brought Contact Assembly from factory and then rectified the problem.

952-B PHASE

952-B PHASE- NEW KIT

AFTER POLE REPLACEMENT BY SCOPE KIT

CONTACT ASSEMBLY CHANGED

AFTER RECTIFICATION ON 30.03.2006

CONCLUSIONS Test for CBs proved useful in indicating

 DCRM

condition of main/ arcing contacts for erosion, misalignment and looseness etc. misalignment and looseness etc.  Prevention  Major

of Major failures by timely diagnosis

overhauling

of

Interrupters/

chamber can be decided based on DCRM

Arcing

MAINTENANCE OF CIRCUIT BREAKERS

QUARTERLY MAINTENANCE OF CIRCUIT BREAKERS

PORCELAIN

1

Clean all porcelain thoroughly

2

Check for cracks.

3

Check for flash over marks. OPERATING MECHANISM BOX

1

Check connection for tightness.

2

Check and clean for auxiliary contacts.

3

Check cubic heater.

QUARTERLY MAINTENANCE OF CIRCUIT BREAKERS

MARSHALLING BOX

1

Clean the connection by CTC/Equivalent.

2

Check connection for tightness.

3

Check L.T. Plug point.

4

Clean switch contacts.

5

Check the fuses.

6

Clean the M.B.

7

Check MK box for vermin proofing.

QUARTERLY MAINTENANCE OF CIRCUIT BREAKERS

RESISTANCE MEASUREMENT

1 Closing Coil 2 Tripping Coil - I 3 Tripping Coil - II LOCAL/REMOTE BREAKER OPERATIONS

1

Closing Operations

2

Tripping Operations through TC-I & TC-II

3

Trip Trial through Protection

ANNUAL MAINTENANCE OF CIRCUIT BREAKERS

1

Breaker Timing

a Closing Time b Tripping Time c

CO Time

2

Checking of operation counter

3

Check pole discrepancy

4

Check of interlocks

ANNUAL MAINTENANCE OF CIRCUIT BREAKERS

5

Static Contacts resistance

6

Checking of tightness of all the termination in the MB.

7

Checking of door sealing gaskets and replacement there of if necessary

8

General cleaning of MB and repainting of metallic surface if required.

9

Check functioning of space heater / illumination.

ANNUAL MAINTENANCE OF CIRCUIT BREAKERS

10

Record the Winding Resistance of the Spring Charging Motor

11

Record the Current drawn by the Spring Charging Motor

12

Record the Time Taken to charge the spring by the Spring Charging Motor

13

Check the operation of Limit Switch

14

Check for Gas Leakage if any

MAJOR REPLACEMENTS/OVERHAULINGS Operating Inspection Item

Inspection & Renewal of Main Contacts

Renewal of Parts of Operating Mechanism

Condition

/Renewal Period

Small Current Interruptions

After @ 4000 Operations

Rated Continuous Current Interruptions

After @ 2000 Operations

Rated Short Circuit Current Interruptions

After @ 20 Operations

Total Number of Operations

After @ 5000 Operations