We have two 600 kw Detroit generators with asco t switches.During our monthly load test on occasion the 800 amp main breaker will trip.This only happens on the transfer back to standard power.It's a known fact that the asco's switch too fast resulting in a short.The generators can be anywhere from 0 to 180 degrees out of phase with the utility.The building motors basically dynamically break and feed back into the busses as they spin down.Other strange things have started to happen as well.For instance in one area of the building up to 50% of the electronic ballasts in the fluorescent lights will fail and have to be replaced.I would think that this is due to either the basic input rating or the K rating the xformer that services that particular area.Has anyone seen this before?It's a new system and the electrical engineers have been out twice in the last year to monitor and solve the problem to no avail.Why not install an in phase monitor to delay the transfer?That breakers going to fail sooner or later at this rate.
Frank, just so I can picture what is happening, are the generators suppose to be in sync with the utility prior to the transfer switch opening. Or do the generators shut down prior to the transfer switch moving back into the utility supply condition. In other words is there suppose to be a blackout prior to the return of utility power? Just trying to learn.
Ok, let me get this straight. Utility, and the gennies are NOT ever linked, but the out of phase load inertia as you go back to the utility trips the breaker? Sounds like some massive motor loads? Darn straight the breaker might not survive the next time you do it. Can't be good for the motors, or anything else either.
Mark Heller "Well - I oughta....." -Jackie Gleason