Sudden tripping of 1200amps, 460v, 3ph, impact type circuit breakers
Sudden tripping of 1200amps, 460v, 3ph, impact type circuit breakers
(OP)
I'm wondering why our 1200Amps, 460v, 3ph impact type circuit breakers always trips from the main switchgear when there is a ground fault on its load side. The thing here is that the main breaker from where the sorce ground fault originated did not trip instantly eventhough its the nearest disconnecting means. The loads connected are Air condition handling units (AHU).






RE: Sudden tripping of 1200amps, 460v, 3ph, impact type circuit breakers
RE: Sudden tripping of 1200amps, 460v, 3ph, impact type circuit breakers
The NEC requires ground fault on 1000 A breaker and above, so smaller breakers often do not have ground fault.
To improve coordination (but decrease protection), you can increase the pickup and time delay on the 1200 A breaker's ground fault element (if you haven't already done this
RE: Sudden tripping of 1200amps, 460v, 3ph, impact type circuit breakers