Electrical fault mystery

[EricP]

Yesterday the local primary school had all their electrical equipment junked. Copiers, computers, everything that was plugged in. Sockets that were unloaded "sparked and smoked" .All the neons lights went "very white and bright"

They are on triple phase mains. There were builders in but not doing anything directly with the electrics.

The first informed comment was that at least 400 volts must have passed through the place. Nothing can be found as a cause, it just happened

Everybody denies liability including the suppliers. :))

Anybody come across this sort of thing before?

[Owain]

Heard about it, when there was a failure at a substation.

Don't know any more details.

The electricity supplier will have a hard job denying liability especially if neighbours were also affected.

Owain

[Chris J Dixon]

Once had a photocopier go up in smoke in the office, overnight. Apparently some work was being done elsewhere which upset the neutral point. Luckily it was seen before the place went up.

Chris

[avocado]

I'm sure the suppliers main fuse would have blown on whichever phase caused the problem. You say there were builders on site at the time - sounds too much of a coincidence to me. Could it be that they shorted two of the phases sending 415V down on of them?

[Tom Woods]

yes. builders in schools are very good at denying all knowledge of problems they have caused! The ones round here are very good at breaking fibre links!

It is a shame that they didnt have a UPS on the main server in the place. They generally log voltage fluctuations (and protect stuff from them!).

[Colin Wilson]

This sounds like a lost neutral, although i'm no expert on the full effects of same.

If the schools' own spark has checked out the possibility of a lost neutral on "their" side of the wiring, it may be a joint breaking down under load on the supply side.

If you're in a Scottish Power area, can I suggest you call the emergency number on 0845 272 2424 to get it investigated ASAP

Failing that, call whichever the local electricity company is, and get them to come out in a hurry !!!

AFAIK you would have a valid claim if the fault was on the mains network, but the common tale is to tell you to claim off your own insurers.

[Bill]

In message , EricP writes

?????????

Builders will deny anything and everything, the VERY large dent that appeared in my sink directly below where one had been using a club hammer appeared miraculously one day. He never saw it happen though.

Any way as to your problem, although I'm no electrical expert, I've seen similar twice but both times from 3 phase generators where the neutral was missing. Once at a golf tournament when the sparky lifted the neutral connection with the genny running and powering a number of portacabins, loss of PCs and copiers etc. Secondly at a factory in Cambridge, Pye Telecom', we had only occupied it for about a week when they decided to do the first generator check in the evening and for whatever reason again the neutral wasn't connected and everything was overvolted, it took days to test all the test gear etc. before we could use it.

I'd grill the builders again, not literally of course, HSE might have something to say about that.

Please do let us know if you find the cause.

[Andrew Gabriel]

Did it happen on every phase or just one (or two)?

If every phase was hit, I don't see how it could be anyone other than the supplier's fault.

What about other premises nearby?

Yes, got hit by a surge about 5 years ago. The only harm it did me was to destroy the ethernet port on Sun Ultra 5. It belonged to my employer and they claimed (I went for a plug-in ethernet card, so I didn't have to lose the system to have the M/B replaced). Lots of people got hit, and the supplier had to switch the area feed due to a network fault, so there wasn't really any question of denying it. I don't know what the voltage surge went up to. It also caused all my X10 switches to take on random settings, but they didn't suffer any long term damage. It was in the middle of the night, so most things were switched off (the Ultra 5 was on though).

[Harry Bloomfield]

avocado has brought this to us :

You cannot actually 'send' 415v down one cable or wire.

[Tim..]

Shorting 2 phase wires together would create one-helluva-bang, not 400+v at the other end.

Tim.

[John]

Had a similar thing a few years ago, fax melted down. Electrician traced it to a brass socket behind a boardroom sofa, vigorous movement of the sofa had chafed the wires. The cause of the chafing was the office cleaner and her boyfriend.......you couldn't make it up!

[w_tom]

230 volt electronic appliances are expected to withstand spikes of up 1000 volts without damage. If the spike were longer, then that maximum number would be lower and the event would be more obvious in lighting.

A ballpark idea of how large a spike would be to do so much damage.