Client has problems with normally open bypass breaker that tripped free when closed. There was no fault or overload on the system, and the same source was on both sides of the breaker when closed. Breaker is electrically-operated, drawout-mounted, and is less than 1 year old. Trip unit flags gave no clue as to trip cause. Square D has done forensic testing and has said that the trip unit has a problem.
Anyone else experienced this or something similar?
Regards, Chris Johnston
Yeah but with Siemens breakers. Loose screws from the factory were the cause of the problem.
Anyone else experienced this or something similar?
Regards, Chris Johnston
I have seen this with a similar transfer scheme with SQD.
Did it ever work? What changed? Primary injection test or secondary? Sounds like secondary injection on the trip unit.
Telling you that the trip unit is ok is sorta like telling you the engine runs when the car will not move. It would be impossible to trouble shoot this in text. Get the boys from SQD back out and put the breaker in the cell connected to the bus and then test it. Flatly refuse to pay for their service if you had to. Call someone else out, Emerson and Eaton both have service groups, NEITHER is cheap.
Breaker was tested by both primary and secondary injection. Breaker had performed correctly on 15 previous operations within the last 6 months.
Are you 100% sure that the ground is intact? Continuous at all points?
Are you familiar with testing breakers? Did they take the breaker away or did you have the tests done on site? Where I worked before we would never do both tests on the same breaker. Primary injection would prove the point and secondary injection would have been a waste of time.
I would look at something mechanical with the breaker. I used to do PM's at a facility yearly near the ocean. We had to go through the breakers mechanical systems before we could test. The environment was causing most of the problems.
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Yes, I am familiar withe breaker testing to NETA standards. The breaker was primary injection tested on site as part of the site acceptance and commissioning process. The breaker later was secondary injection tested on site as part of routine PM. The breaker is less than 1 year old.
Thanks, Chris
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Time to look at the mechanics of the breaker.
Something has happened to cause the "trip free". Do you have "people that like to tweak?" on site
I once had a Westinghouse breaker out of the cell that we could not make work. I installed in back in the cell and then it worked fine. Seems someone had changed the wiring in that cell and the breakers were not interchangeable any more. Do you or the customer have another breaker that can be substituted in that location as a test?
No tweakers on site. The breaker is part of a system that has an automatic resume generator attched to it - the system goes down and all associated get pink slips. The malfunctioning breaker was replaced and sent to Square D for forensic testing. I'm trying to find whether others have had similar problems. Chris
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