Power with a mind of its own...

[tomed101]

I'm not sure whether this is the right place for this but anyway...

So this morning Im in a choir rehearsal running a few mics and suddenly all the light go out, an almighty bang comes from the PA and the emergency lights cut in. A few seconds later the lights come back on and everything is normal... For some reason power went out to the entire building and came back by itself. Nowhere else in the school was affected and no equipment was damaged. The weird thing is that the power came back. I thought it could have been a problem with the AC when the compressor cut in, tripping the breakers.

As far as I know, breakers don't trip and come back do they??? Anyway I checked all three main power boards for the building and nothing has tripped and all the surge divertors were still operating. I checked with Admin and there were no sparkeys working in the school, and the only other way power could be cut to only the one building is to get into the Pad mounted sub-station and trip a breaker in there and reset it, but admin assures me no-one was there...

Does anyone have any ideas why this would have happened? If so I want to work on having it fixed.

Tom

 

[JD]

Breakers on the panels don't reset themselves, but the ones on the poles do (3 times.) Probably a traffic accident tripped one on one phase leg but there was no sustained short so it reset. (may not have been local)

EDIT: Oh, could also have been a grid switch. Sometimes when lines are being worked on, they will reroute. When they do, they will often drop the one route before engaging the new route. This can be local, street, neighborhood, or area. Your other buildings may be on a different loop.

 

[tomed101]

That's interesting about the pole breakers resetting. But if that was the case, the whole school would have gone down. The entire school runs off its own substation on school grounds, so my understanding is that if anything goes out further up the line to the individual breaker panels, everything goes...

 

[JD]

Not necessarily. Often, only one phase leg will drop. If the house lighting (or control for it) and sound were on that leg, that is the effect you would get.

 

[TimMiller]

The power company is really bad about dropping a leg, then reconnecting it without any warning. I really wish they would give you a heads up, computers, CNC's, etc dont like it when a leg goes down. And the power company his this great clause that even if they totally hook your power up wrong they are not responsible. At a show i had a neutral leg out on the pole completely melt and they were like we arent responsible for your $25k repair bill.

 

[tomed101]

We were running a small 12 channel dimmer pack in the booth which uses three phase, to run a few temporary lights and the entire thing went out as well. I dont know that all works, but if one phase is dropped in a dimmer, do only same of the lights go or all of them? This was an old basic dimmer and not one of those complicated computer controlled ones.

We had the incident officially reported with admin so that later if we discover anything damaged, the school will pay for it.

Semi-related story:

Last year we had a sparkey who couldnt figure out a circuit so instead of taking out one of the larger breakers up the line, he dropped the entire building (without warning anyone). When he was finished he just flipped the 1200A breaker again. As a result the projector and fire alarm got blown up (which the electrician refused to pay for repairs) This added up to several thousand dollars, which were sorely needed for other areas of the department...

 

[TimMiller]

i bet your schools main breaker is more than 1200A. There is one school i go to tie in at, and they have a 1200A breaker for their kitchen. Thats where i tie in at, b/c plays are never at the same time as their kitchen.

 

[tomed101]

i bet your schools main breaker is more than 1200A. There is one school i go to tie in at, and they have a 1200A breaker for their kitchen. Thats where i tie in at, b/c plays are never at the same time as their kitchen.

Yeah it is, but the breaker for the building which contains out auditorium is 1200A. He was only working on the one building. I have no idea what teh entire school has but I think the substation out the front is something like 800KVA.. not sure on that.