For maintenance of circuit breaker or circuit breaker maintenance, it must be first switched off and then isolated from both sides by opening concerned electrical isolator.
At this no isolated condition the circuit breaker must be operated for local and remote condition yearly and when required. The circuit breaker should be operated electrically from local and remote then mechanically from local. This type of operation makes the breaker more reliable by removing any coating developed between sliding surfaces.
Bulk Oil Circuit Breaker Maintenance
For bulk oil circuit breaker, we should check contact burning. If burning is very light, remove the burn beads and polish the surface. If burning is quite heavy, replace the tips and arcing ring by new set. We should loose and tight the tips few times before final tightening is done.
In addition to that we should also check the extinguishing chamber. It must be removed from the breaker unit and after washing the chamber by insulating oil it is kept as upside down. If the condition of any part indicates severe burning, we should dismantle the chamber and replace the burned/damaged parts.
Next point is cleaning and lubricating CB mechanism. The rust on the mechanism and also from metal mechanism box surface should be removed by non fluffy cotton cloths. The mechanism including gear wheel should be lubricated by high grade grease. But it should be remembered that the friction clutch must be lubricated. In case of minimum oil circuit breaker MOCB, insulator must be cleaned and carbon deposition if any should be removed by Trichloro Ethylene or Acetone. The manual provided by manufacturer for greasing and lubricating should also be followed beside this general instruction.
The locking pins of tie rods should be checked half yearly. All the foundation bolts electrical terminal connections at CB power circuit must be tighten properly after removing oxide coating if nay. This must be done half yearly.
The proper adjustment of auxiliary switch by ensuring correct NO NC contacts at breaker OFF and ON condition must be checked half yearly and in addition to that the auxiliary switch’s contacts should be cleaned properly with help of hard brushes.
The spring charging motor and mechanism should also be cleaned and associated bearing should also be lubricated half yearly.
Minimum Oil Circuit Breaker Maintenance
In case of MOCB, the breaker should be checked monthly for oil leakage and oil level. If oil leakage is found it must be attended and for low oil level top up oil up to desire level.
Visual inspection of circuit breaker and its operating mechanism along with quality of painting, mechanism kiosk door gasket should be carried out quarterly if any damaged found take proper action.
The oil dash pot in operating mechanism must be checked for oil leakage quarterly if leakage is found, replace the defective and damaged O – rings.
It is also highly recommended to ensure the prescribed duty cycle of operation of the breaker including reclosing annually.
Maintenance of Air Blast Circuit Breaker
For air blast circuit breaker there are some special cares to be taken in addition to general instruction for maintenance of operating mechanism. Actually for operating mechanisms and for other some features the maintenance processes and schedules are same for all oil circuit breaker, air circuit breaker, SF6 circuit breaker and vacuum circuit breaker.
In air circuit breaker, the air leakage should be checked as and when it is required. If leakage is found, plug the leakage.
The grading capacitors must be checked for oil leakage monthly. If leakage found plug it.
Yearly, dew point of the operating air at the outlet of the air dryer should be measured with the help of Dew Point Meter or Hygro Meters.
SF6 Circuit Breaker Maintenance
As we said earlier for operating mechanisms and for some other features the maintenance processes and schedules are same for all oil circuit breaker, air circuit breaker, SF6 circuit breaker and vacuum circuit breaker.
In addition to that in SF6 CB some extra care to be taken.
SF6 circuit breaker must be checked for SF6 gas leakage, if unwanted SF6 low gas pressure alarm comes. This is efficiently done by gas leakage detector.
If the circuit breaker is provided with gradient capacitors, these must be checked for oil leakage monthly. If leakage found plug it.
Dew point of SF6 should be checked with the help of dew point meter or hygro meters in every 3 to 4 years interval.