What is the supply voltage in my house please?

[pappyon]

I have just had an energy monitor delivered from npower and one of the settings I have to set on the display unit requires the domestic supply voltage to be entered

Would I be right in saying it is 250V. If not, how do I find out?

Another question. Are these monitors very accurate as regards recording electricity used? This one is an efergy elite rebadged for npower.

 

[Lectrician]

240v would be the best setting as this is typically what you will see.

The actuall UK voltage is 230v, but with tolerrences is actually like to be 240v ish.

you cannot say for sure - it depends which end of the supply run you are, and what loads are on at the time - the voltage will fluctuate.

Unfortunately thats what makes these energy monitors just a guide - they calculate the energy using the current measurement and the voltage you select - a fixed data point so to speak, when in reality the voltage will change and will not be exactly 230/240/250.

 

[pappyon]

I thank you for your prompt reply to my post.

It is much appreciated!

 

[ban-all-sheds]

For many years the supply voltage for single-phase supplies in the UK was 240V +/- 6%, giving a possible spread of voltage from 226V to 254 V. For three-phase supplies the voltage was 415 V +/- 6%, the spread being from 390 V to 440V. Most continental voltage levels were 220/380V.

In 1988 an agreement was reached (CENELEC Harmonisation Document HD472) that voltage levels across Europe should be unified at 230V single phase and 400V three-phase with effect from January 1st, 1995. Those countries with a nominal voltage of 240V (like the UK) were obliged to move to 230V +10% -6%, and those on 220V moved to 230V +6% -10%.

It was proposed that on January 1st, 2003 the tolerance levels would be widened to ±10%, and then that was pushed back to 2005, and then in July 2001 the CENELEC Technical Board decided to continue with the existing tolerances until 2008.

I've no idea whether this change did finally get implemented, or delayed again, or if it will ever happen, but in any event European-wide harmonisation is not being done by having common supply voltages, but by requiring manufacturers to make products which operate over a much wider range. Not too much of an issue apart from incandescent lamps.

 

[Dazz0i]

At college now they're teaching +10% -6% for both single phase at 230Vac and three phase at 400Vac.

With a 1%+- of 50Hz in 24hrs for frequency.

 

[securespark]

According to UU, it's 230 +/- 10%, ie 207-253V.

 

[efiste2]

When Switching secondary substations out for maintenance/refurb and local Transformer isolated, anything less than 220V (At the sub) and it usually gets cancelled and re-scheduled , or in some cases generators are used to hold it up....When energising a new sub, we usually have a open terminal voltage of 248V before switching it onto the system, but local load soon drags it down. Usually these are interconnected subs, but lectrician is spot on it all depends how far from the sub(s) you are......for an energy monitor 240v setting will be fine.....BTW they are a handy thing, for showing how much power your home uses!!!

 

[JohnD]

as well as the voltage fluctuating with demand, the AC Hz varies a bit as well. When the generators are under heavy load they slow down a bit. I used to have access to a website that showed when this was happening. Can't find it now.

 

[flameport]

This website?
http://www.dynamicdemand.co.uk/grid.htm

or more detail here:
http://www.nationalgrid.com/uk/Electricity/Data/Realtime/Frequency/Freq60.htm

 

[JohnD]

that's great, thanks

 

[ricicle]

Notice the use of the logarithmic scale on the meter though, so the needle looks as if we are heading for total blackout....