A Square D/ Schneider 2000 ampere main circuit breaker in the service entrance switchboard trips every time there is a power outage, not when power is restored, but when utility power is interrupted. A 2000 amp service entrance rated automatic transfer switch, open transition, with a main breaker has been installed ahead of the 2000 amp main circuit breaker in the SE switchboard. The main circuit breaker in the ATS never trips on power outage but the switchboard breaker does. In testing, the ground fault protection was disabled and the instantaneous trip setting was dialed up to maximum but the switchboard circuit breaker continues to trip on interruption of power. Any ideas on what is causing this other than a defective breaker or trip unit?
2000 amp main circuit breaker trips on power outage.
- Thread starter Jackeroo
- Start date
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texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
I think a lot more details will be needed to help. With GFPE equipment and generator involved there could be all kinds of reasons for this including design and/or installation errors. SDS vs non-SDS may play a roll and how it is all configured.
Understand SDS and non SDS application problems with GF protection systems however the generator and ATS are recent additions and the problem was occurring long before they were added. The MCB in the ATS provides a convenient means of turning off power to the SWBD. The only time the main in the SE swbd trips is when power is interrupted either by the utility or at the SE ATS. This problem occurs even when swbd loads are off. First thought was a ground fault problem, that is why GF was disabled but that made no difference.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Is the breaker tripping or simply turning off?
By chance is there an under voltage trip unit in the breaker?
By chance is there an under voltage trip unit in the breaker?
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
This is a great suggestion. Also look for a shunt trip module to see if there is something installed to open it based on a protective relay
ATSman
ATSman
- Location
- San Francisco Bay Area
- Occupation
- Electrical Engineer/ Electrical Testing & Controls
As others have mentioned, we need more info to determine if there is a UV device inside breaker causing it to trip (very common on air frame breakers.) It would help to remove the panel cover and take many CLEAR pics of bkr front and side views, esp of the labels next to the control wires that come out of the side(s) of bkr. Also if there is a display/ LEDs on the trip unit to indicate what caused the breaker to trip on a OL or GF condition.
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