Maximum mains line voltage by law

[bigmouk]

At one of our offices we constantly have over-voltage warnings going upto as much as 258v from our UPS. We have been plagued by power cuts etc aswell over the last 9 months. The power company came out and logged voltages but said there is nothing wrong. We have just had 3 more power cuts in the last 5 days. This may well have nothing to do with the over-voltage problem but we want to kick off with the power company now.

The threshold on the UPS is set to 253v. Does anyone know what the max is by law ? I've had a look round the net but cant seem to find anything.

 

[McBunny]

iirc its 230 +- 10%

 

[Paul J]

What UPS do you have? Are you going by the screen reading or taking a measurment with a calibrated meter?

Prior to 1995 the nominal mains voltage was 240v +/- 6%. So in theory the supply companies could provide anything between 226v and 254v (ignoring the decimals for clarity). Europe was operating at 220v +/- 10% (198v to 242v). The powers that be decided to increase the European voltage and reduce the UK voltage so that by the year 2003 we would share common voltage of 230v +/- (207V to 253v). The UK is now in a transition period with our supply being a nominal 230v, but the tolerance is currently +10% -6%, so we can expect to get anything from 216v to 253v out of our sockets.

 

[bigmouk]

APC 3000 Rackmount, so its a decent bit of kit although not calibrated, just taking reading from its logs. I get warning emails whenever there is a spike above 253v

The elecy co came out about 6 month back and put a meter/logger in there. Came back a week later but it hadnt worked so they came again and then said there isnt a problem.

 

[Paul J]

One of our UPS's with a calibrated reading taken from the same point, extreme example but they are not to be trusted.

Dont want to teach you to suck eggs but just incase you dont realise, its best to make sure the UPS output voltage is set suitably, if its set at 230v when your supply is never near that, then on transfer form inverter to raw mains you will get current spikes.

 

[bigmouk]

^ Cheers mate. Spoken to the elecy company again yesterday and i think they are coming checking it over again with a meter/logger. Supposedly there was a crack in some wiring and its taken them weeks too find it thats why we have had power problems.

 

[182fastblue]

217 is the lowest it can go i think 253 is the highest