FKA Oil Circuit Breaker
1200amp— 72.2kv Breaker

Internal Inspection and test – Found several in one location with bad bushings and cracked upper adapter clamps. Also had a similar unit, 34.5kv at a steel mill with 3 cracked upper adapters (picture below right).

The upper adapter is a component that makes up the stationary contact assembly and is a current carrying piece that attaches the contact mount to the bushing stud. In both cases no parts were available quickly, a repair procedure was developed and the cracked components were TIG welded and put back in service. The utility has had parts repaired in this manner in service for numerous years. The steel mill purchased re-placement components and had us change them out the following year on shutdown.

The type U bushing used on this circuit breaker and also used on trans-formers are documented to have problems with high power factors.

As these units have well documented problems, if you are an owner, it is essential that routine internal inspections be done as well as testing. The bushings need to be tested using the C1 power factor test on the power factor tap and compared to the nameplate.

Close-up of crack in upper adapter.