GE AK breaker intermittent nuisance tripping of bell alarm lockout

[jdk0082]

Has anyone out there experienced intermittent nuisance tripping of the bell alarm lockout on a GE AK type breaker used a generator paralleling breaker? It will occasionally deploy the bell alarm without registering a fault indicator on the trip unit and with no apparent fault. Seems to only happen with the breaker racked onto the bus and not when operating the breaker out on the rails. My theory is that it is due to excessive vibration reverberating through the switchgear and breakers when multiple paralleling breakers are closing in quick succession onto the common bus.

[SecondGen]

What type of AK breaker specifically? It's not uncommon to find these lockouts loose if that helps affirm your theory. Does the breaker trip or just the bell alarm? If you can pull the breaker out, get underneath it check to make sure everything is tight. If you can provide more info on the breaker I might be able to help out some more.

[SecondGen]

By the way, here is an AK breaker maintenance manual that goes into detail on how to adjust the bell alarm. Check out Page 26, Section 7.11 http://apps.geindustrial.com/publibrary/checkout/GEK-64459D?TNR=Application%20and%20Technical|GEK-64459D|generic

101

[SecondGen]

I was recently called out to help troubleshoot an AK circuit breaker that was tripping free, and for some reason this old thread came to mind. After doing some investigating, we found that vibration from the breaker closing was triggering the bell alarm, which was causing it to trip free.

It was pretty easy to narrow down to the bell alarm because after the breaker would trip free, you had to reset it. The only time the bell alarm should fire is after a trip, not a manual operation, so it was obvious something was up.

That was the moment when I remembered this thread and the note about the adjustment. We found the bracket that's attached to the trip button shaft right up against the side latch on the bell alarm module, instead of a small gap as spelled out in the manual.

The adjustment wasn't actually on the bell alarm itself but rather the bracket attached to the trip button shaft. You can adjust this bracket by loosening the two 5/16" nuts holding the bracket to the shaft.

We loosened the nuts and moved the bracket back 0.030" inches (with the breaker closed) as stated in the manual and viola! The breaker no longer tripped free.

This particular breaker was a utility main (1600A) at a data center for a major wireless carrier. As you can imagine, this one minor adjustment caused the customer a lot of panic as they were running off a single main breaker with the switchgear bus tied.

I was glad we could get them back to 100%, and I was happy that I remembered this thread because it definitely helped save some time troubleshooting. Sorry I don't have any photos, it was a secure area that doesn't allow phones.