Tuesday, January 23, 2007

Wall of sound

No, nothing to do with Phil Spector, but an interesting experience at work yesterday.

I have a fascination with large scale engineering. You can tell I'm a bit sad because I took a photo of the Leeds Grand Theatre Mains Intake which I noticed was 3 phase 2000 Amps, a somewhat substantial 1.4 Megawatts.

Our building has a large standby generator that cuts in if the mains fails. However, last November, it didn't start during a night-time failure and 30 minutes or so later the batteries were pancaked on the Computer Room power supplies. Needless to say, total power loss in a data centre is a long-winded process to recover from.

(Apparently, if the National grid shut down for some reason, it would take a week to get it all back online which is a rather un-nerving prospect).

After the incident, we had a couple of generator tests but they were somewhat contrived as they were manual transfers onto partial load. Since then, I have been waiting for a real power cut to get confidence in the system.

Anyway, yesterday the mains dipped then went out. Our IT department held its collective breath and five seconds later, the lights came back on again. A quick look out of the window and we could see that the Generator was running- a large cloud of white smoke was billowing out of the exhaust, the new Pope had been chosen. The white smoke then turned into black soot and it eventually cleared once the engine warmed up. Indeed, someone from IT was walking across the car park as it started and had been engulfed in fug...

However, the mains appeared to have come on again in surrounding buildings but our generator was still running. I asked our maintenance people what load it was pulling but they said they couldn't make any sense of the readings. I persuaded them to let me have a look so armed with torch and ear defenders, we ventured into the generator house. The Genny is containerised and wasn't particularly noisy- until they opened the inspection door. That was when the wall of sound hit me, the roar of a large diesel running the building power.

I could see why they were confused as the voltmeter showed 0 volts. However, the Ammeter showed 700 Amps. There were various knobs to read different settings of voltage and current but I didn't really want to tinker with it as a little knowledge is a dangerous thing. I pronounced that it was certainly running the building and they alerted the maintainer to check out whether there was a problem.

Later that day, the power flicked again and then the generator turned itself off a couple of minutes later. The maintainers offered the opinion that when the power recovered the first time, it was out of specification (probably by being supplied from another zone) but when it was switched back again the system correctly went back to normal.

I was interested to know what load the system was actually providing but it appeared to be a two phase generator (the ammeter controls were only labelled L1 and L2) and with a reading of zero volts it was hard to speculate. I made a token attempt to look at the rating plate on the alternator but the cacophany of noise kept me away. I am relieved, though, that the system can switch full load as we have a UPS test coming up next month.

Finally, as a treat to technophiles, I attach photos of the Leeds Grand mains intake panel and their emergency sprinkler system pump. Because I can!


Liz said...

"took a photo of the Leeds Grand Theatre Mains Intake which I noticed was 3 phase 2000 Amps, a somewhat substantial 1.4 Megawatts"

You can get help, you know.

Groovy word verifier 'eadlzlzk' - perhaps I should seek help too?

Welshcakes Limoncello said...

"Because I can" - like it! I need you here, IG, 'cos we are limited to 3 kw of electricity per household and so we have to keep checking how many appliances we have got on at a time - and because you understand this stuff.

Ian Grey said...

A friend of mine who lived in France was also capped to 20 Amps or so (4,400 Watts).

Just about OK if you don't have electric heaters...