Capacitor used in Generator circuit breakers compartment 2

[npower0073]

Dear all. On site we have generator circuit breaker of ABB where between the generator circuit breaker and the step-up transforemr winding we have capacitor from each winding to earth. Is it possible to tell me what is the use of this capacitor? Thank you in advance.

 

[GTstartup]

Pretty sure thats a lightning/surge arrestor. I remember some fun we had with a 13.8kV ABB breaker while DC hipoting the connected bus. Didn't realize it was there and while grounding the bus to investigate why the hipot result was no good, it drew out an arc about a foot long.

One of those "pucker" moments

 

[npower0073]

GT Start up, the lightning arrestor is a separate equipment on the generator circuit breaker compartment. Type of GCB is ABB HECS 100L 15,75kV 12kA SF6 insulated.

 

[GTstartup]

OK then a surge capacitor only, slightly different function than the lightning arrestor, takes care of day to day surges and works in conjunction with the ligtning arrestor. Of course a quick call to ABB would confirm this.

 

[cuky2000]

The ABB GCB could be provided with both surge arrester and surge capacitor.

Surge arrester can be fitted on the transformer side, to provide protection for transformer and generator against overvoltages particularly reducing the peak of the surge.

Surge capacitors are fitted on both sides of the breaker system, to provide additional protection against overvoltages and to support arc extinction in the circuit breaker by transient Recovery Voltage (TRV) limitation. This also reduce the slope of the wave impulse.