MAINTENANCE AND INSTALLATIONOF

CIRCUIT BREAKER

By,Rohini Haridas

Assistant Professor,Dept of Electrical Engineering,

SSGM College of Engineering,Shegaon

Lack of maintenance may results in failure in operation

Maintenance

Breakdown or corrective

maintenance

Preventive maintenance

Breakdown or corrective maintenance

� activities are undertaken after failure of anequipment

�Such a maintenance results in outage of circuit�Such a maintenance results in outage of circuitbreaker and supply

�In general, it consist of locating the trouble ,repair and recommissioning

Preventive maintenance � is undertaken to ensure smooth and efficient

working of a system, equipment.

�This type of maintenance is undertaken as perschedule before breakdown of a system orequipment

�Repair or replacements are made to ensure that nobreakdown occurs at any time during the service

For switchgear and protective equipment,preventive maintenance is recommendedpreventive maintenance is recommendedbecause failure of a switchgear can not bepermitted

General Maintenance Activities

Inspection Servicing Examination Overhaul

Steps in maintenance of CB

1. General Inspection

o Observe the Circuit Breaker visually .

o Note the cleanliness, terminals, earth connections, reading of counters, level of quenching medium and pressure of quenching medium

2. Cleaning and drying

o Use clean cloths which does not leave fibers orparticles on the surface

o Use air pressure jet for cleaningo Use air pressure jet for cleaning

o Other cleansing agents recommended bymanufacturer

3. Insulation surface

o Inspect visually, carefully for the signs of cracksor any other defects

o Clean the internal surfaces and external insulatingsurfacessurfaces

o Insulation should be free from electrical ormechanical defects

o Perform insulation resistance test, it givesindication about the health of insulation

4. Drying

Circuit breaker pole can be internally dried by circulating dry hot air.circulating dry hot air.

5. Interrupter o Observation, cleaning, replacement of main/arching

contacts .

o Cleaning of other parts as well

o Removal of carbon decomposed product

o Cleaning terminals and sliding contact surface

o Cleaning of venting systems to ensure free passage ofoil/gas

6. Mechanism

• Check operation open and close

• Checking simultaneous opening and closing ofthree poles

• Check operation counter

• If the mechanism has operated more than 1000times, it needs very close operation and may needoverhaul

7. Main connections

Ensure that good contact is maintained and connections are right and secure

8. Earth connections

9. Auxiliary devices

10. Isolating contacts

11. Overload devices and protective relays11. Overload devices and protective relays

12. CT and PT

13.Final verification

INSTALLATION

1) Check the readiness of foundations and theirdimensions as per the drawing

2) Check the level of foundation surface2) Check the level of foundation surface

3) Place the base frame of circuit breaker in position

4) Assemble operating mechanism in its position

5) Give auxiliary supply

6)Tighten all bolts and other hardware

7) If provision available, operate slow opening and closing

8) Measure insulation resistance

9)Fill quenching medium after drying

10) Check leakage and ensure leakage free assembly

11) Check its opening and closing operation

12) Measure timing and check simultaneousoperation of three polesoperation of three poles

13) Operate the CB by operating relevant relays