I am sure that some of you have had dealings with these breakers. The one I am referring to is something like a 2000 amp GFI.
Anyhow I had a trouble call because the breaker kept tripping when they would fire up a large motor. Forget exactly what size motor but it was big. The breaker would trip on (ground fault) but one time it tripped on instantaneous(?) My first suggestion was that the motor or the circuit feeding the motor was bad or going bad. The electrician said they had meggered the motor and the circuit and was OK. They wanted to blame it on the PoCo. They said that the breaker would read line and load as far as the GFI was concerned. Just being a lineman I thought surely this thing could not read the line side but what do I know. Without the motor or hardly anything running they were pulling around 300 amps per leg(277/480). I told them that if there were a problem with the trans bank then at 300 amps it would be showing something pretty visible that would be seen from standing on the ground. Arcing or melted insulation or something.
They replaced the "brain" for the breaker but still had the problem. THey had steady voltage the whole time even when the breaker tripped. The equipment they had would record the voltage and load and who knows what else.
I haven't been back to find out what the problem was or if they had resolved it. I know they had called for a temp disconnect to replace something else to do with the breaker but don't know what the outcome was.
Any ideas what the trouble could've been?
Oh and they had mentioned that they did not have this problem until we had a severe lightning storm the day before.
????
