Mains in UK can go up to 292VAC for periods of several minutes

[ocset]

Hello,
Sorry to discuss UK, but i think the mains is more badly deviant in UK than some other countries.

Some time ago, a very kind person sent me some data of the second-by-second mains voltage level in Bavaria , Germany. This was extremely interesting since the mains voltage was never seen to go above 235VAC, and that over 3 days. 
We are suffering failures in our UK based products which appear to correspond to persistently high mains voltage     ….ie not short switching induced transients or lightning induced transients. We suspect that the mains is simply going up to around 413Vpk (292VAC) , or more, for sustained periods. 
We believe that this is entirely possible since the UK mains voltage is not strictly regulated.   The UK mains is in fact regulated mostly by probability which says that at any given time of day the amount of loading will be roughly equal to the previous days. As such, the power stations adjust their output throughout the day to kind of give feed-forward regualtion.    There are also tap changers in the transformer sub-stations which roughly adjust the turns ratio of the mains transformers to kind-of regulate the mains to a degree.
However, these don’t operate quickly, so therefore the mains in certain areas of UK can easily go up to 292VAC for sustained periods of minutes…do you agree?   

 

[Gyro]

so therefore the mains in certain areas of UK can easily go up to 292VAC for sustained periods of minutes…do you agree?   

No, not really.

UK mains voltage is specified to reach the consumers' premises at 230V -6%/+10% under European Harmonisation. In practice it is normally 240V -10%/+6%, the same result... 254V rms maximum. It may rise above that in the case of a supply equipment fault but that would be in very isolated cases, not something you would see turning up as a significant product failure rate. There may wall be spikes, but anything sustained at 292V would cause failure of multiple appliances within the home, not just your product. The energy supplier would be liable for damage caused.

The official source: http://www.legislation.gov.uk/uksi/2002/2665/regulation/27/made


Edit: You should put a question mark at the end of your thread title as it is amost certainly not the case!

[rstofer]

I live in the US and know little about the UK power system but...

Are any other products failing, or just yours?  Do you have a recording of voltage versus time.  The utility companies around here will install recorders temporarily (on demand) if you suggest a problem but this is usually related to undervoltage.

Our residential voltage will be regulated to +- 5% - see page 4
https://www.pge.com/tariffs/tm2/pdf/ELEC_RULES_2.pdf

If this was a real problem, everybody would be screaming.  You need data, not conjecture.  So, go get some...

[james_s]

My friend in Manchester monitored his mains for several months a few years ago and found a surprisingly wide range, something like a low of 230V to a high of a bit over 250V. Mine on the other hand was found to be considerably more stable, I think I measured a low of 118.5V and a high of 121.something. A place I used to live was a bit more lively and it was typically 123-125V.

[chris_leyson]

Hi Treez, just been finishing a design for a small universal input flyback 85V to 265V nominal. It also has to work safely at 300V in order to monitor the incoming line voltage and shut down or disable other line connected devices if the line voltage goes above say 290V.

We are suffering failures in our UK based products which appear to correspond to persistently high mains voltage

In that case redesign it for 300V or 310V maximum, it may cost a little bit more but in the long run it's cheaper than replacing an under rated design. I'm not implying that the UK mains voltage would ever reach 290V but it could happen.

[Delta]

No, I do not agree.  Frankly, that is nonsense.

[coppice]

The mains in the UK usually varies very little. Its generally one of the better regulated networks. Changes from the mean are generally dips under extremely high load, not an overvoltage situation. None of the appliances in the UK have been tested above 264VAC (240V + 10%) during their approvals. If the mains rises above that and damages something, you can claim against the supply company. At 292VAC a lot of MOVs, and other protection devices designed to absorb impulses, would be getting rather hot. A lot of equipment would be failing.

Have all the failed units failed with a particular customer? Were they all in remote locations (e.g. extreme rural conditions), where mains regulation is often a little looser? Even there, if someone sees 292VAC at an outlet the supply company will normally treat that as an emergency repair situation.

[IanB]

At 292 V incandescent bulbs would get extremely bright and have a very short life. There are still many of these around especially the energy efficient halogen ones and the small decorative bulbs.

That said, I have read that wind power may produce much greater voltage fluctuations than traditional power generators. Any chance these observations come from an area with wind farms?

[coppice]

I have read that wind power may produce much greater voltage fluctuations than traditional power generators. Any chance these observations come from an area with wind farms?

Power networks were designed to feed power only from the backbone to the tributaries. Wind power generally feeds into the backbone, and should be fairly harmless, even though its much more variable than traditional generation. It is solar power which has been seen deregulating the voltage in some parts of the world. When power is fed into a tributary from too many domestic solar generators, they can sometimes supply more power than the tributary is using. Now the excess power needs to go up stream, and most networks aren't designed for that. The tributary separates itself from the main network, and with excess power available the voltage can rise. Its called the islanding effect, and its a serious problem which has lead to changes in the requirements for grid feed inverters. Many blindly follow what the network is doing. New regulations demand that they cap the maximum voltage at which they will feed power to the grid.

[tggzzz]

We are suffering failures in our UK based products which appear to correspond to persistently high mains voltage 

What is the evidence for that? You have provided only conjecture.

What fails and what are the failure modes?

What other equipment (including lights) has failed in the same locations?

What is the evidence that your equipment isn't faulty?

Might you have used underspecified mains components?

Might you have a faulty design?

[capt bullshot]

In case the line voltage sustains 290V for minutes (in a nominal 230V/240V environment), this is to be considered a major fault. It's way out of specs. As someone else pointed out, this could be caused by solar grid tied inverters and weak infrastructure - in this case, the power supplying company should have had rejected the installation of the solar inverters. Here in Germany, each grid tied inverter must be approved by the responsible power company. If it's a typical household (single phase) inverter, they give you instructions how to hook it up (which phase you must use), to spread the load evenly across the distribution network.

Another cause for such overvoltage might be a neutral fault.

Otherwise, the line voltage here is expected to be quite stable and regulated. I've attached a one years recording of line voltage and frequency that I made some years ago - the voltage and frequency stays well within the limits.

[Jeroen3]

Some time ago, a very kind person sent me some data of the second-by-second mains voltage level in Bavaria , Germany. This was extremely interesting since the mains voltage was never seen to go above 235VAC, and that over 3 days. 

This depends highly on the last stage distribution. Some areas have a weak LV transformer or long wires, some areas have highly variable load.
I occasionally have these graphs as well. From last week for example, at a co-generation site that occasionally goes in hard shutdown. And nobody knows why.
The demo effect made sure it did not happen again after installation of the measurement equipment

_{I have no idea what happened to Monday. Sometimes these PSL devices just give up. You can't afford them, but they're not very robust.}

[IanMacdonald]

No. 6% over 240 is the upper limit. If it goes above that you can claim for damaged equipment.

[capt bullshot]

There's a story I remember, related to overvoltage:

Once upon a time, I used to work for a small company making power quality analyzers, transient recorders for mains fault analysis and the like. Every now and then, a customer came up with a difficult case and asked for help. One of these cases:

I a larger town in northern Germany, there was a landlord (rather a housing society than a landlord), that was accused by a tenant for all kind of electrical stuff failing due to problems with the power line. Lights sometimes went very bright and burned out (smells like a ground fault, but was checked by the local electrician). It's been a house with many flats, and only this particular one had this issue. We (my former boss and I) went there at least twice and installed one of our analyzers to record line surges etc. - nothing, except the analyzer failed at some point with a broken power supply unit  Other damages still happened. The housing society agreed to install a big line filter and surge suppressor for this flat - no improvement. We got a broken wall wart type battery charger (and a good one as reference) to analyze for the fault's reason (they ran the TV set off a lead acid battery charged by this charger to prevent damage to the TV set  ). The charger was clearly damaged by applying mains power to its output (we tested this with the good charger and got similar damage) 

Somewhat later, we got notice the issues were all gone - the tenant (a single mother with a juvenile son) moved somewhere else ... now it's up to you to guess what or who caused all the issues, we were never told officially.

Another story was about a failing telecom system in a large coal power plant - turned out to be sabotage by a bored employee ...

[amyk]

In case the line voltage sustains 290V for minutes (in a nominal 230V/240V environment), this is to be considered a major fault. It's way out of specs. As someone else pointed out, this could be caused by solar grid tied inverters and weak infrastructure - in this case, the power supplying company should have had rejected the installation of the solar inverters. Here in Germany, each grid tied inverter must be approved by the responsible power company. If it's a typical household (single phase) inverter, they give you instructions how to hook it up (which phase you must use), to spread the load evenly across the distribution network.

I thought solar inverters had voltage regulators? Or do the cheapest ones have completely unregulated output?

[CJay]

Hello,
Sorry to discuss UK, but i think the mains is more badly deviant in UK than some other countries.

Nah, not the case at all, it may be problematic in your local area but that's indicative of a fault, not the general state of the UK grid.

The mains supply in the UK is very well regulated and rarely breaches the specified tolerances, if you've recorded voltages outside that range you need to speak to your electricity supplier and request they do something to first validate your findings and then fix the problem, they are also liable for damages caused as a result of those out of tolerance voltages so you've got some leverage if it's their fault, your insurance company may even be willing to help you apply pressure if you speak to them about claiming for the damage on your home policy.

[capt bullshot]

I thought solar inverters had voltage regulators? Or do the cheapest ones have completely unregulated output?

At least the ones conforming to the regulations and installed correctly will shut down if the line voltage or frequency exceeds the given (locally regulated) limits. The upper voltage limit is well below 292V (253V afaik).

But you can still experience overvoltages at remote power line endpoints due to resonance issues - the inverter cannot sense the line voltage at the remote end of your distribution line.

Don't now about the stuff you can buy elsewhere at the bay, never tried one.

[dmills]

Somewhat later, we got notice the issues were all gone - the tenant (a single mother with a juvenile son) moved somewhere else ...

The kid was running a pot growing operation and running all his grow lights off one phase, and the neutral is high impedance (The real fault).

The tell for a neutral fault is lights going very bright and burning out, as the neutral gets dragged towards a different heavily loaded phase.

Regards, Dan.

[ocset]

The kid was running a pot growing operation and running all his grow lights off one phase, and the neutral is high impedance (The real fault).
The tell for a neutral fault is lights going very bright and burning out, as the neutral gets dragged towards a different heavily loaded phase.

Thanks, do you mean the Neutral was not earthed at any point?

[CJay]

Somewhat later, we got notice the issues were all gone - the tenant (a single mother with a juvenile son) moved somewhere else ...

The kid was running a pot growing operation and running all his grow lights off one phase, and the neutral is high impedance (The real fault).

The tell for a neutral fault is lights going very bright and burning out, as the neutral gets dragged towards a different heavily loaded phase.

Regards, Dan.

Funny, I've seen very similar things happen in an office block where the neutral connection had worked loose and was arcing, I watched PC after PC fail with a mushroom cloud of smoke pouring out the back of them, finally managed to convince the office manager to get everyone to unplug their machines.

[dmills]

Lost neutral on three phase is a fairly popular party trick in data centres (Also at live gigs) largely because people forget that the triplen hamonics sum in the neutral instead of cancelling.

You can easily hit neutral currents 150% of RMS phase current on a fully loaded system with an unfortunate combination of harmonics.

Regards, Dan.

[ocset]

Funny, I've seen very similar things happen in an office block where the neutral connection had worked loose and was arcing, I watched PC after PC fail with a mushroom cloud of smoke pouring out the back of them, finally managed to convince the office manager to get everyone to unplug their machines.

Thanks, this says it all….terribly high overvoltages can after all happen on the UK mains…    .all it takes is a badly wired neutral.    I wonder who is going to pay much money for eg a load of streetlights if this sort of shenanigans can  kill them in no time. 

There’s also the fact that some customers might inadvertently plug eg a  load of streetlights into a line-line outlet, which , as you know, is 415VAC. 

Maybe this is the reason that Harvard lighting never roled out their leafnut streetlighting system as far as was predicted? 
http://www.harvardtechnology.com/solutions/leafnut/
…some 10 years ago, Leafnut hit the UK market and was supposed to dominate the entire UK streetlighting market, but then  it all seemed to go very quiet for Leafnut....the role out was never anywhere near as big as predicted.....maybe  the mentioned power system faults keep companies from wanting too much exposure to LED streetlights? 
 

[weirdgeordie]

The last house I lived in, had constantly high voltage of around 249v, also my UPS was reporting an "overloaded neutral", called the supplier out, they left a monitor for a week, but they said it was all within tolerance, if on the high side.

When I asked what they thought of the UPS reporting the overload on the neutral, they had no idea what I was on about!

Moved out before I got a real answer to what was wrong, but we had a lot of bulbs go early and appliances with motors die.

James

[BrianHG]

20 years ago, at my parents house, actually 4 entire small suburbia blocks (almost 20 houses, rich area), a faulty transformer center tap left every one with half the items/lights in the house dim and the other half way too bright.  It went up and down with load and the weather, but eventually one day got so bad that instead of 120v, half of items in all of the houses went above 175v and the power company had to pay out a few 100K$ for repairs in all the houses.  If it were apartment complexes instead of houses, the damages could have been over 10x.

[ocset]

Thanks,
I think the truth is spilling out now all over the place!....the UK mains (and other country’s) can go well high…certainly up to 292VAC….and all because of power system faults!
I myself remember working at Carling academy nightclub in Birmingham UK back in 2002, and we were constantly replacing 10’s of lightbulbs in the  bars every week…..very often, (in fact, more often than not) ..you would  fit  a replacement lightbulb in to  a  ceiling fitting, and it would immediately die on you.

We all thought the gaffer was buying dodgy lightbulbs, …but now I wonder. Though at the time we were suspicious that the problem might have been caused by the double decker bus sized fan which blew through the vent system. (maybe such a big and old fan put loads of noise and spikes on the electrical system? -The fan was so powerful,  and used to suck air from open air vents in a room in the side of the building....if you lost grip of the door as you tried to enter/exit that fan room, your arm would get trapped in the door by the fan suction and your arm would be broken for sure) Another point was that it was a very old building..in fact, a converted old  theatre…so maybe the neutral wire had corroded away.?