Mains voltage poll (UK)

[IanB]

I often read about the European harmonization of mains voltage and I wonder if in reality it has changed anything. Could we do a quick poll around UK residents? If you have a (safe) DMM, could you make a quick measurement of your mains voltage and post the result below? Is it still generally 240 V, or has anything changed in recent years?

[Bashstreet]

241.7

[BNElecEng]

Measured this morning, 242V at the wall at home. 420V line to line at work.

[Bashstreet]

I often read about the European harmonization of mains voltage and I wonder if in reality it has changed anything. Could we do a quick poll around UK residents? If you have a (safe) DMM, could you make a quick measurement of your mains voltage and post the result below? Is it still generally 240 V, or has anything changed in recent years?

To be accurate Britain takes part in the European mains voltage harmonization.
As In U.K voltage is to be 230 +-10% the old standard sits inside the tolerances.
I am not sure if any work has been done to upgrade old transformers to the new standard as they reach end of their service life.

It is process that might take decades if ever and is related to political will and needs rather than any other requirement.

[Avacee]

For the OP:  243.7V @ 49.7Hz at 20:32 UK time in the North-west

UK National Grid data ... http://www2.nationalgrid.com/uk/industry-information/electricity-transmission-operational-data/
http://www2.nationalgrid.com/UK/Industry-information/Electricity-transmission-operational-data/Data-explorer/

There are a couple of sites that show such data which appear to refresh every 5th minute and I dare say some others will show historic voltage trends but my google-fu is weak tonight
http://gridwatch.co.uk/

Another site: http://nationalgrid.stephenmorley.org/

And  http://www.gridwatch.templar.co.uk/

Edit: Next time an enviromentalist tells me we should close all nuclear plants and build more solar I'm going to give them a link to the sites above and ask them how much solar has produced in the last week (the weather has been pretty shitty).

[IanB]

Cool, it is still 240 V then. Apropos of nothing, I just measured 242.3 V @ 59.99 Hz here in California. Just a couple of volts off the nominal value.

[richard.cs]

239.9 V here. Nothing has changed or is intended to change, except that at some point in the indeterminate future everyone is supposed to widen their asymmetric tolerances out to 230 V +/-10%.

[mariush]

Romania ... 1:22 am , 246v AC (using a kill-a-watt type device) 

Typical for this hour...

AFAIK it's 230v +10%, -6% ... so still within acceptable limits.

[IanB]

Romania ... 1:22 am , 246v AC (using a kill-a-watt type device) 

Typical for this hour...

AFAIK it's 230v +10%, -6% ... so still within acceptable limits.

Do you know what your local voltage is supposed to be (nominal value)? Even though 246 V is within +10% of 230 V, I think voltage regulation at the point of distribution is usually better than that (see above for examples of voltage regulation in the UK). I suspect voltage regulation is better in the center of towns and cities, but may be worse in rural areas especially at the end of a long spur.

[Brumby]

Well, it's the middle of the day here in western Sydney and I just checked at a power point.  It varied between 233.7V and 236.1 V over a period of a minute.

Edit: There are a few things switched on here - so I expect the building voltage will have sagged slightly.  There were no obvious signs of anything being switched on or off in the building during my measurement - so I expect the fluctuations came from load variations in the area.

I know I've said this before - but I always get amused when people talk about mains standards.  Back in 2000, Australia went from a 240V standard to a 230V standard - but the amusing bit was the tolerances that were included....  240V +6%/-10% went to 230V +10%/-6%.  Do the math.

Somebody was an administrative genius.

[IanB]

Well, it's the middle of the day here in western Sydney and I just checked at a power point.  It varied between 233.7V and 236.1 V over a period of a minute.

Wow, that's some variation. Do you live in a third world country? 

[Brumby]

Think I just found a dicky power point socket.

Tried another one and got 235.9V to 236.7V over a period of 3 minutes.

[Artlav]

Middle of the night here in Moscow (technically Europe too), the sockets show 225V, which is a bit above the nominal 220V we should have here. During the day i remember measuring about 215V.
Does not sound like our grid is getting harmonized to anything so far...

[HKJ]

We had 220VAC before the harmonization, now it is 230VAC in most places (Denmark).
I have 230V within a volt or two most of the time.

[Ampera]

It's a funny story in the US, at least from my perspective.

We are officially supposed to be 120VAC, 60hz, but depending on who you ask, some people will say the US is 115V, 110V. There are all tolerances, and these numbers are still within them, but all my meters (on a UPS for example) stay right around 120VAC.

It gets even crazier in Japan. They have 100VAC power at either 50 or 60hz depending on what half of the country you are on. They also use essentially the same NEMA standard the US does, just with a different name, and from what I can tell they have some plugs that look like they come from the 50s (small housing, thin wire), no meat to any of it). Grounding also seems to be a bit up in the air with some places having it, some places not, some places having ungrounded sockets with a grounding post on some socket? I don't live in Japan, so I can't confirm any of this to be a thing on a large scale, but I know it exists.

We have so many standards for all of this, but nobody can standardize the standards. We even have over 20 different organizations across the world that do standards, like DIN, ISO, IEEE, IEC/CEE, NEMA, BS/BSI, JIS, the list could go on and on.

Anyways, sorry for being a random Yankee passing through, carry on.

[BradC]

Well, it's the middle of the day here in western Sydney and I just checked at a power point.  It varied between 233.7V and 236.1 V over a period of a minute.

WA was always a bit of an outlier. When I was a kid it was 250V.
Anyway, here's 2 phases at my place Red & Green are on the same phase. One is a vaguely accurate power meter, the other is an APC UPS. They mostly agree, but the meter is more accurate (as you'd imagine).
Blue is another UPS on a separate phase.

[Delta]

I normally see high 240s.

The "harmonisation" was purely political, not a single voltage regulator or transformer tap was changed.

All countries used to have tolerances od +/- 6%. 240v countries "harmonised" to 230 +10% / -6%. 220v countries "harmonised" to 230 -10% / +6%.

Do the maths, and you will see that to allowable voltage ranges are (almost) completely unchanged.

Genius!

[Berni]

It can varry quite a lot.

I happened to test it yesterday:

L1: 237V
L2: 246V
L3: 215V

Third phase is low due to a 4kW heat pump running from it.

[Karel]

For the OP:  243.7V @ 49.7Hz at 20:32 UK time in the North-west

Wow, that frequency has a huge deviation from the nominal frequency.
What kind of instrument did you use?

Because according to this website that shows the actual powergrid frequency, it is generally much more accurate:

http://www.mainsfrequency.com/

[Moshly]

Well, it's the middle of the day here in western Sydney and I just checked at a power point.  It varied between 233.7V and 236.1 V over a period of a minute.

Wow, that's some variation. Do you live in a third world country? 

If you are on a farm in Australia then you probably have ->
https://en.wikipedia.org/wiki/Single-wire_earth_return

[wraper]

Hmm, I measured 229V in Riga, Latvia. Last time I measured it was good old 220V. I also don't recall ever measuring voltage going this high here unlike in rural areas. So probably 230V harmonization at work.

[Dubbie]

239.8V here in NZ. I'm just across the street from the pole transformer which probably helps.

[AndyC_772]

242.3V this morning here in Hampshire, measured using a Fluke 289 on the end of a lightly loaded IEC distribution block.

This is pretty typical, it's usually a little above 240V here.

[IanMacdonald]

248.5 here in Scotland. Which is not unusual. Prior to EU dictatorship conquering us it used to be 240 +- 6% so that's still within limits. 

[tszaboo]

You know, it matters how far down the feeder you are measuring. Also during the day, solar power will raise the voltage. And other stuff, about a dozen other factor.

[bd139]

245.0 here in London 10:00. Calibrated Keysight U1241C. Residential ring main. Unloaded.

[NivagSwerdna]

Isn't this all a bit pointless?  Doesn't it depend on the load across the wire when you measure it?  For me wouldn't that be dependent on the resistance of the wire back to substation and all loads down my street in parallel with that phase?

[bd139]

Yes and no. Sometimes there are persistent drops and peaks. We get up to 300v here occasionally which causes some problems (I've lost about 20 wall warts in the last few years)

[Bashstreet]

Quite few countries in U.K 

[IanB]

Isn't this all a bit pointless?  Doesn't it depend on the load across the wire when you measure it?  For me wouldn't that be dependent on the resistance of the wire back to substation and all loads down my street in parallel with that phase?

It's interesting actually to see what kind of variation in the nominal service voltage might be seen at different places and times.

But mostly for me it does confirm that the nominal voltage in the UK is still 240 as it always has been.

[Avacee]

For the OP:  243.7V @ 49.7Hz at 20:32 UK time in the North-west

Wow, that frequency has a huge deviation from the nominal frequency.
What kind of instrument did you use?

Because according to this website that shows the actual powergrid frequency, it is generally much more accurate:

http://www.mainsfrequency.com/

UT139C - freq spec is 10Hz-10MHz ±(0.1%+4)   .. Obviously I'll take the official figure over a cheapo UT any day
Currently it's 243.9V at 49.97Hz.

Though it's not uncommon for the network to sag across the UK on the hour or half-hour in the evening due to https://en.wikipedia.org/wiki/TV_pickup

[mariush]

Romania ... 1:22 am , 246v AC (using a kill-a-watt type device) 

Typical for this hour...

AFAIK it's 230v +10%, -6% ... so still within acceptable limits.

Do you know what your local voltage is supposed to be (nominal value)? Even though 246 V is within +10% of 230 V, I think voltage regulation at the point of distribution is usually better than that (see above for examples of voltage regulation in the UK). I suspect voltage regulation is better in the center of towns and cities, but may be worse in rural areas especially at the end of a long spur.

It's 234v AC now at 14:00 

Yes, I live relatively far from the center of the town but it's a populated area, so it's not like the quality would be worse due to lower population density.

The voltage is just not as regulated here... i had an cheap atx power supply without power factor correction die on me a couple months ago when the voltage got up to 249v AC
The frequency however is pretty much rock solid... 50 Hz or maybe 49.9 Hz for a few seconds  at most.

[Zero999]

Bedford, UK: 240.4V, 50.06Hz.

[Mr. Scram]

Wow, that's some variation. Do you live in a third world country? 

In regard to anything networked, it almost seems those down under are.

[Cyberdragon]

Now everyone measure their distortion!

[Simon]

Sure YOUR mains voltage will be determined by whatever your local substation supplies you (mine is in my back garden - well ok that bit of land is not mine but it cuts into my land). It's more relevant for the range devices can work in. Uk is 240, europe is 220, 230 is in the middle and well within a 5% tolerance of both (208.5/241.5V)

[SeanB]

South Africa earlier the week measured 238VAC, typical for the area, as I can see the 500kVA transformer across the park, though the PISWA cable does follow the street down and back, making it 200m or so of the Victorian era copper ( and 20m of more modern cable scotchcast to it where the cable thieves nicked it) that used to power trolley bus power. End of the line by me, there is a power monitor in the meter room, power line info sent from the PLC, that does monitoring for the Metro. Highest voltage I saw was 278VAC, when the neutral and PE cores were nicked by the thieves, quickly went down and pulled the big red switch on the meter room to keep the block safe, then got on the phone to tell Metro the cable had been nicked again. Too bad for the corner coffee shop, his brewing equipment and IT stuff, plus all the lighting, were on the phases not connected to the heaviest load from the stoves, and they all lost that battle in a blaze of glory.

[Berni]

Now everyone measure their distortion!

Queue the exploding scope probes!

Nah i got a Keithley 2015 DMM here so it can give me THD directly.

[Retep]

230VAC +10%/-6% 50Hz is imposed by the bureaucrats in Brussels, however in little over a year from now the UK is no longer part of the EU and is finally free to choose its own mains voltage and frequency.

[bd139]

We’ll be going back to 230/415V three wire DC then.

[IanB]

Sure YOUR mains voltage will be determined by whatever your local substation supplies you (mine is in my back garden - well ok that bit of land is not mine but it cuts into my land).

That's the whole point of the survey actually. It's possible some people might have seen 230 V and some people 240 V depending on the age of their property. But everyone's answers seem to indicate that the UK is still on 240 V.

[rstofer]

It's a funny story in the US, at least from my perspective.

We are officially supposed to be 120VAC, 60hz, but depending on who you ask, some people will say the US is 115V, 110V. There are all tolerances, and these numbers are still within them, but all my meters (on a UPS for example) stay right around 120VAC.

A long time ago, the standard was 110V.  Then it was raised to 115 then 117 and finally 120V.  You can find schematics with each of these values depending on when they were published.  This article doesn't mention 117V but apparently 120V was standardized in 1984 (fairly recent).

https://www.quora.com/Is-the-power-system-in-the-US-technically-110-115-or-120VAC-How-about-220-or-is-it-240-or-235VAC

The line-to-line voltage will be double or 240V.

[Retep]

We’ll be going back to 230/415V three wire DC then.

Sounds like an excellent choice to me.

[tooki]

I normally see high 240s.

The "harmonisation" was purely political, not a single voltage regulator or transformer tap was changed.

All countries used to have tolerances od +/- 6%. 240v countries "harmonised" to 230 +10% / -6%. 220v countries "harmonised" to 230 -10% / +6%.

Do the maths, and you will see that to allowable voltage ranges are (almost) completely unchanged.

Genius!

Sure YOUR mains voltage will be determined by whatever your local substation supplies you (mine is in my back garden - well ok that bit of land is not mine but it cuts into my land). It's more relevant for the range devices can work in. Uk is 240, europe is 220, 230 is in the middle and well within a 5% tolerance of both (208.5/241.5V)

No, Europe is not nominal 220V, and hasn’t been since 1983! It’s nominal 230V, with stepwise change in the acceptable tolerances. Given the actual voltages reported (and the ease with which a power generator’s output voltage can be changed, given that it must be adjusted constantly during use to adapt to load), I don’t think there’s a shred of evidence that the actual voltages in Europe have remained unchanged, by virtue of simply still falling within tolerance.

[A Hellene]

Last year I personally calibrated my APC SURT 1000 XLi UPS:


APC SURT 1000 XLi report.png

And, no, I do not think that this kind of everyday mains voltage fluctuations is an exclusive Hellenic consumer's privilege!


-George

<EDIT>: Damn the browser auto-correction feature!...

[Delta]

I normally see high 240s.

The "harmonisation" was purely political, not a single voltage regulator or transformer tap was changed.

All countries used to have tolerances od +/- 6%. 240v countries "harmonised" to 230 +10% / -6%. 220v countries "harmonised" to 230 -10% / +6%.

Do the maths, and you will see that to allowable voltage ranges are (almost) completely unchanged.

Genius!

Sure YOUR mains voltage will be determined by whatever your local substation supplies you (mine is in my back garden - well ok that bit of land is not mine but it cuts into my land). It's more relevant for the range devices can work in. Uk is 240, europe is 220, 230 is in the middle and well within a 5% tolerance of both (208.5/241.5V)

No, Europe is not nominal 220V, and hasn’t been since 1983! It’s nominal 230V, with stepwise change in the acceptable tolerances. Given the actual voltages reported (and the ease with which a power generator’s output voltage can be changed, given that it must be adjusted constantly during use to adapt to load), I don’t think there’s a shred of evidence that the actual voltages in Europe have remained unchanged, by virtue of simply still falling within tolerance.

Fair enough, I should have been clearer, no voltage control changes were made to the generation or distribution network here in the UK.  We are still on 240 nominal in practice.

I have never measured less than 238v at peak demand time.  If the grid operators were consciously trying to aim for 230 nominal, they are doing a bloody bad job of it.


I cannot speak about other countries.

[IanB]

Fair enough, I should have been clearer, no voltage control changes were made to the generation or distribution network here in the UK.  We are still on 240 nominal in practice.

I have never measured less than 238v at peak demand time.  If the grid operators were consciously trying to aim for 230 nominal, they are doing a bloody bad job of it.

Which is why I wanted to do a quick straw poll, to confirm this. Simon didn't actually post his local mains voltage, in spite of being just a few feet away from the substation. It would be interesting to see what allowance they make for voltage drop in the low voltage cable to the most remote consumers. Simon is presumably going to get a voltage pretty close to what comes out of the substation.

[HKJ]

I got a bit interested in how exactly the mains voltage varies around here and not just a quick glance on my power analyzer now and then. This means I put my DMM7510 on it for a bit over a day.


First curve is logged with one second intervals, the voltage has a lot of fast changes.


Calculating a rolling 1 minute average gets rid of some of the changes.


10 minute average


1 hour average

I live in a apartment in Copenhagen Denmark, i.e. in a big city.

[Rerouter]

Sydney Aus, at 20:20 late evening, 243.6V AC, at 13:00 It was holding steady at 264V from all the nearby solar installations.

[tggzzz]

Edit: Next time an enviromentalist tells me we should close all nuclear plants and build more solar I'm going to give them a link to the sites above and ask them how much solar has produced in the last week (the weather has been pretty shitty).

Indeed, but the wind is always blowing somewhere, isn't it?

No. Not when there is a high pressure blocking zone sat over the UK for days at a time.

Using a year's worth of gridwatch data, a rule of thumb was that if the UK peak wind power output is P, then it is less that x*P (0 in range 0..100%) for x% of the time. For example, 10% of the time it is less than 10% of peak.

You need reliable baseload power stations active and ready to generate when, not if, they are needed. The cost of keeping those stations available should be included in the wind/solar costs.

[Freelander]

Edit: Next time an enviromentalist tells me we should close all nuclear plants and build more solar I'm going to give them a link to the sites above and ask them how much solar has produced in the last week (the weather has been pretty shitty).

Indeed, but the wind is always blowing somewhere, isn't it?

No. Not when there is a high pressure blocking zone sat over the UK for days at a time.

Using a year's worth of gridwatch data, a rule of thumb was that if the UK peak wind power output is P, then it is less that x*P (0 in range 0..100%) for x% of the time. For example, 10% of the time it is less than 10% of peak.

You need reliable baseload power stations active and ready to generate when, not if, they are needed. The cost of keeping those stations available should be included in the wind/solar costs.

I always thought they turned those windmills off at night ?..............................................