Mains in UK can go up to 292VAC for periods of several minutes  - Page 1
Forum section: electronics / beginners

author: ocset
author_rank: Super Contributor
timestamp: December 12, 2017, 10:00:31 pm
content: 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?

author: Gyro
author_rank: Super Contributor
timestamp: December 12, 2017, 10:28:16 pm
content: QuoteNo, 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/madeEdit: You should put a question mark at the end of your thread title as it is amost certainly not the case!

author: rstofer
author_rank: Super Contributor
timestamp: December 12, 2017, 10:30:29 pm
content: 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 4https://www.pge.com/tariffs/tm2/pdf/ELEC_RULES_2.pdfIf this was a real problem, everybody would be screaming. You need data, not conjecture. So, go get some...

author: james_s
author_rank: Super Contributor
timestamp: December 12, 2017, 10:31:05 pm
content: 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.

author: chris_leyson
author_rank: Super Contributor
timestamp: December 12, 2017, 11:44:58 pm
content: 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.QuoteIn 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.

author: Delta
author_rank: Super Contributor
timestamp: December 13, 2017, 12:52:41 am
content: No, I do not agree. Frankly, that is nonsense.

author: coppice
author_rank: Super Contributor
timestamp: December 13, 2017, 01:01:47 am
content: 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.

author: IanB
author_rank: Super Contributor
timestamp: December 13, 2017, 01:07:19 am
content: 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?

author: coppice
author_rank: Super Contributor
timestamp: December 13, 2017, 01:18:22 am
content: Quote from: IanB on December 13, 2017, 01:07:19 amPower 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.

author: tggzzz
author_rank: Super Contributor
timestamp: December 13, 2017, 08:51:38 am
content: Quote from: treez on December 12, 2017, 10:00:31 pmWhat 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?

author: capt bullshot
author_rank: Super Contributor
timestamp: December 13, 2017, 11:00:55 am
content: 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.

author: Jeroen3
author_rank: Super Contributor
timestamp: December 13, 2017, 11:02:08 am
content: Quote from: treez on December 12, 2017, 10:00:31 pmThis 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 equipmentI 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.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: December 13, 2017, 11:24:13 am
content: No. 6% over 240 is the upper limit. If it goes above that you can claim for damaged equipment.

author: capt bullshot
author_rank: Super Contributor
timestamp: December 13, 2017, 11:39:21 am
content: 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 unitOther 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 ...

author: amyk
author_rank: Super Contributor
timestamp: December 13, 2017, 12:00:49 pm
content: Quote from: capt bullshot on December 13, 2017, 11:00:55 amI thought solar inverters had voltage regulators? Or do the cheapest ones have completely unregulated output?

author: CJay
author_rank: Super Contributor
timestamp: December 13, 2017, 12:27:05 pm
content: Quote from: treez on December 12, 2017, 10:00:31 pmNah, 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.

author: capt bullshot
author_rank: Super Contributor
timestamp: December 13, 2017, 12:43:23 pm
content: Quote from: amyk on December 13, 2017, 12:00:49 pmAt 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.

author: dmills
author_rank: Super Contributor
timestamp: December 13, 2017, 01:38:27 pm
content: Quote from: capt bullshot on December 13, 2017, 11:39:21 amThe 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.

author: ocset
author_rank: Super Contributor
timestamp: December 13, 2017, 02:01:11 pm
content: QuoteThanks, do you mean the Neutral was not earthed at any point?

author: CJay
author_rank: Super Contributor
timestamp: December 13, 2017, 03:00:10 pm
content: Quote from: dmills on December 13, 2017, 01:38:27 pmFunny, 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.

author: dmills
author_rank: Super Contributor
timestamp: December 13, 2017, 03:52:26 pm
content: 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.

author: ocset
author_rank: Super Contributor
timestamp: December 13, 2017, 04:01:31 pm
content: QuoteThanks, 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?

author: weirdgeordie
author_rank: Newbie
timestamp: December 13, 2017, 04:05:22 pm
content: 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

author: BrianHG
author_rank: Super Contributor
timestamp: December 13, 2017, 04:07:50 pm
content: 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.

author: ocset
author_rank: Super Contributor
timestamp: December 13, 2017, 04:14:43 pm
content: 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.?

author: Monkeh
author_rank: Super Contributor
timestamp: December 13, 2017, 04:32:32 pm
content: Of course faults can occur. No need for truth to spill out about that, it's no secret.Also, as far as 'line-line' sockets go.. you can't inadvertantly do that. If you can: That's a faulty installation or a faulty idiot with a screwdriver.

author: grumpydoc
author_rank: Super Contributor
timestamp: December 13, 2017, 04:39:24 pm
content: Quote from: treez on December 13, 2017, 04:14:43 pmYes,faultscan cause voltages to increase - but that wasn't the thrust of your initial post was it? You implied in that that it was almostnormalfor UK mains voltage to ride at 292V for sustained periods because, well, we "don't care about regulation".How much fault voltage you want to design your products to withstand is, of course, your own choice but the UK tolerance is (IIRC) 230 V +10%/-6%. Anything persistently outside that is a fault and can be reported as such (and will get fixed with luck).

author: dmills
author_rank: Super Contributor
timestamp: December 13, 2017, 04:41:41 pm
content: Neutral faults on three phase systems are notable and memorable when they happen to you, but are a long way from being commonplace, they are for the most part one of those things that you might know somebody it happened to (or somebody who knows somebody), but it is not something you really expect to ever experience.PME/MEN style distribution wiring makes the things even less commonplace, albeit somewhat more dangerous when they happen.Nobody designs single phase product to survive lost neutral or 400V line to line, and for the most part nobodies stuff blows up when you plug it in (And when it does, it is seldom because of a major mains brewup), generally a lost neutral causes you MUCH bigger issues then a few blown light fittings.Failures due to gross sustained over voltage are a zebra, you have hoofprints and in the first instance should be thinking of something far more common like say a horse or a product design cockup.You will also find that if you track down the standards for electrical supply to street furniture (And the ones for grounding of same) that they are quite detailed.Old theatre air handlers are a law unto themselves, but the motor would almost certainly have been three phase, probably with no neutral, so not particularly relevant, but with old nightclub wiring who knows?Line to line is usually a RED CEE connector, not something that it is easy to mistake for anything else.Regards, Dan.

author: wraper
author_rank: Unknown
timestamp: December 13, 2017, 05:06:49 pm
content: No, you have failures because of crap products. A bunch of other treads you started brilliantly show how your products are designed. Overall it seems you try to find justifications to all issues rather than fix the mess your company is which is the root cause of most problems.

author: wraper
author_rank: Unknown
timestamp: December 13, 2017, 05:44:44 pm
content: In addition to that, IMO your products have so "big" design margin that cannot survive additional 10 volts of mains voltage UK has compared to the rest of Europe. Although it's supposed to be 230V, it's still good old 240V in most cases.

author: coppice
author_rank: Super Contributor
timestamp: December 13, 2017, 05:55:41 pm
content: Quote from: wraper on December 13, 2017, 05:06:49 pmFrom the other threads he started about his product failures you have to wonder if they did any EMI/EMC/ESD testing at all.

author: dmills
author_rank: Super Contributor
timestamp: December 13, 2017, 06:09:28 pm
content: Treez does seem to have more EMC/EMI/ESD and general reliability pain then any other three engineers I know of.I think part of it may be excessive focus on BOM cost to the detriment of doing it right for reliability, make it as simple as possible **but no simpler**, there is an art to that.Now I don't play in highly cost constrained markets, but I cannot but think that improving design and testing to cut customer returns is something that pays big dividends until the return rate is very, very low, and that this is probably more true as margins reduce.Regards, Dan.

author: wraper
author_rank: Unknown
timestamp: December 13, 2017, 06:47:11 pm
content: Quote from: dmills on December 13, 2017, 06:09:28 pmBOM cost may be very cheap if design is well thought. One of my designs has around 4-5 times lower component cost compared to competitor. Yet it does not have any of noise immunity, ESD susceptibility, overall reliability issues that competitor device is plagued with. And even has better performance. Making things expensive does not give any guarantee they will be any good.

author: jc101
author_rank: Frequent Contributor
timestamp: December 13, 2017, 06:59:35 pm
content: I had a couple of years worth of logs from my UPS until recently (disk failure), with the min, max, and average of the voltage at 1min intervals. Only once did I get up to 254v on the incoming supply and the power network people turned out to take a look. They called a short while later to ask if things were normal, which they were, and muttered something about the HV boys trying out some new gear that was running a bit high. As I'm close to the local substation my voltage was just over the limits. All sorted in a couple of hours.I have seen faults internally to an install kill all sorts of kit, I remember seeing a neon switch from a power strip fly horizontally in front of me before the smoke from the kit led me to leg it out the room. That was a 4 pole switch on the incoming supply, the neutral contact was iffy. It was replaced with a 3 pole and a solid bolted neutral connection and the problems all went away.

author: Gyro
author_rank: Super Contributor
timestamp: December 13, 2017, 07:24:02 pm
content: Quote from: treez on December 13, 2017, 04:01:31 pmNo, sorry - you're really clutching at straws now!A 3-phase Neutral fault can happen in any country. How many of your outside lights are installed in tower blocks?A Neutral fault in a normal domestic street is an extremely rare event, it would affect many other pieces of consumer equipment and would not show up as a significant product failure rate.You have a product problem that you need to investigate. Making wild assumptions about massively out of legal spec mains voltages is distracting you from focusing on this!P.S. There are a very large number (majority now I think) of LED streetlights in the UK, there is no reason why they would have to adopt Leafnut though.

author: chris_leyson
author_rank: Super Contributor
timestamp: December 13, 2017, 07:55:59 pm
content: QuoteNo guarantee at all. However, I was once the unfortunate owner of an Ariston washing machine and after four replacement controller boards in three years I bought a Bosch and haven't had a problem. One of the guys who fitted one of the controllers said they were crap and you need to fit a surge protector. At the time the house was supplied by overhead lines and I think brown outs were more of a problem and I even needed a call out one winter to fix a dodgy connection, nothing else failed only the crappy washing machine.

author: dmills
author_rank: Super Contributor
timestamp: December 13, 2017, 08:26:55 pm
content: Oh indeed, no argument there, but there is a point at which BOM squeezing starts to do bad things, the point can be lowered with clever architecture, but it is always there.Regards, Dan.

author: coppice
author_rank: Super Contributor
timestamp: December 13, 2017, 08:35:22 pm
content: Quote from: dmills on December 13, 2017, 08:26:55 pmSpending on the BOM to achieve EMI/EMC/ESD goals is largely a substitute for NRE. Spending is no guarantee of success in EMI/EMC/ESD tests, but a little competent engineering effort and some additions to the BOM will usually get you through. From there you spend on stripping the BOM to an extent that is appropriate to the production volume. If the volume justifies some serious effort, you can usually get the BOM quite close to its value before the EMI/EMC/ESD began.

author: rstofer
author_rank: Super Contributor
timestamp: December 13, 2017, 08:37:46 pm
content: There can always be a LOCAL problem like a floating neutral. But it certainly won't be nationwide. Further, it would be easy to find with a DMM or perhaps a logging (min/max) DMM. And other stuff would be burning out as well. If that were the case, I would expect someone to have called the electric company. That's kind of what they do for a living.

author: chris_leyson
author_rank: Super Contributor
timestamp: December 13, 2017, 09:58:00 pm
content: I don't know, stick the bloddy thing on a bench connect a scope to it and wind the variac up, testing is part of development. You must know what failed in the units in the field that went pop and that would be a good place to start. Did something overheat, is it overvolts on a switching device, something went short because of a transient spike or maybe a control loop went ape shit. You've got to test for ALL of these things and a hell of a lot more before you put it on the market, otherwise it will only come back and bite you on the arse. I've just got a teeny tiny little flyback converter working as it should thanks to some good silicon and a lot of hard work and good advice from a lot of other engineers. It will work quite happily at 300V maybe even 320V but not yet tested to 320V. My next job is to kick the electrical shit out of it and then it can go into a product and that's what engineers do.

author: tggzzz
author_rank: Super Contributor
timestamp: December 13, 2017, 10:28:22 pm
content: At aguess, it feels like treez' development team has drunk too deeply of the XP Kool Aid that is prevalent in the software world: TDD, or test driven development. While there is some validity to thatin limited and controlled circumstances, unthinking application of the XP dogma often causes problems akin to building castles on sand.Whereas TDD can work within a solid well thought out foundation, simply rushing into the simple "happy daze" functional tests often leads to running foul of subtle "corner case" requirements at a very late stage in the development. The software solution often involves large scale refactoring.Now large-scale refactoring at a late stage is sometimes practical with modern strongly statically typed languages, but that doesn't work with hardware at a smaller scale than the minimum replaceable unit (usually a PCB).Given the questions and statements from treez in this and other threads, it tells like they have a long slow path ahead of them.

author: IanB
author_rank: Super Contributor
timestamp: December 13, 2017, 11:50:17 pm
content: Quote from: tggzzz on December 13, 2017, 10:28:22 pmI think I would like react to this view with a slightly different perspective.One shouldn't follow a process because it is dogma, one should follow it with a view to how it can help you get better results.I think part of the TDD process is to start by asking the question, "What the heck is this thing supposed to do, and how would I test that?"Then with the answers to that question, you would figure out what test methods, processes or test jigs you will need to verify that it does the right things. And you use that knowledge to inform the design, and test early as you go along, rather than thinking about the testing at the end. This is the "test driven" part of test driven design.If you leave testing to the end, you may find a test case that you didn't account for in the design, which would force you to go back and do rework.

author: tggzzz
author_rank: Super Contributor
timestamp: December 14, 2017, 12:04:12 am
content: Quote from: IanB on December 13, 2017, 11:50:17 pmAll very rational, and it is how I developon top of a sound foundation. The sound foundation implies and ensures that the awkward scenarios have already been dealt with in the fundamental structure.Never ever forget the oldengineering(cf amateur hacking) maxim: "you can'ttestquality into a product". (It has to bedesignedin!)Unfortunately XP and TDD zealots often get too enthusiastic and dogmatic, to the exclusion of common sense and using the appropriate combination of techniques.When confronted with someone that believes too much in TDD, I ask them how they willtestACID transaction properties, both selection of the correct subset, and that it is correct for their application.cross-clock domain synchronisationdistributed FSM behaviour (think telecom systems) in the presence of missing and duplicated eventsresilience to and recovery from ESD eventsand so on. Too often I simply get a blank look indicating such considerations are beyond their comprehension.

author: David Hess
author_rank: Super Contributor
timestamp: December 14, 2017, 12:11:48 am
content: Quote from: amyk on December 13, 2017, 12:00:49 pmIt is not that simple. The grid tied inverter can regulate the voltage where it is located but by removing the load which would normally be present, the voltage between the grid tied inverter and the power plant rises. The result is poorer regulation in general no matter what the grid tied inverter does. Solutions include lowering the resistance of the distribution system which the power company is obviously not going to look favorably on since it costs them money to invest in infrastructure just so customers can purchase less power from them.Quote from: weirdgeordie on December 13, 2017, 04:05:22 pmThis happened to me earlier this year. My UPS started reporting power faults a couple times an hour leading me to do a general inspection and discover that a tree had knocked the line between the house and the pole down breaking the neutral. My temporary solution was to connect my whole house 240 volt AC phase splitter shown below until the power company could come out and fix the line.

author: coppice
author_rank: Super Contributor
timestamp: December 14, 2017, 12:19:53 am
content: Quote from: David Hess on December 14, 2017, 12:11:48 amIt is fairly simple. Any grid tied inverter has to track the grid voltage, to be able to feed into the grid. Many older inverters did this in a fairly dumb way, and could track upwards a long way. The latest ones just stop feeding the grid if the measured grid voltage rises above a safe threshold. If the voltage rises too far you might find a lot of solar inverters suddenly drop off the grid, and the reduction in capacity might then lead to a blackout. You won't see a dangerously high voltage, though.

author: BrianHG
author_rank: Super Contributor
timestamp: December 14, 2017, 12:24:32 am
content: Quote from: David Hess on December 14, 2017, 12:11:48 amAfter a severe summer storm about a decade ago, on of the main phases wired into my house slowly became more and more iffy as well... If I weren't an electrical engineer, I would have not realized what was truly going on and would have not known to call the power company risking a fee if the problem was determined to be inside my house instead of outside with the connection to the pole transformer.Small world....

author: Jr460
author_rank: Regular Contributor
timestamp: December 14, 2017, 12:38:19 am
content: Had dropped phase once in the underground service to the house.From the looks of things the wires had been nicked 20+ years ago when the phone company ran too close to them. It was just a matter of time for the ground settle just right and heavy rain the day before and to problem was in a low lying area.What we saw was some light not working, then some were fine and others were dim.Within an hour or so they came out, fund the area of the fault, dug down a few feet and spliced the blown apart wire.

author: David Hess
author_rank: Super Contributor
timestamp: December 14, 2017, 01:11:00 am
content: Quote from: coppice on December 14, 2017, 12:19:53 am*You* will not see a dangerously high voltage but someone between you and the power station may. Your grid tied inverter supplies power which you otherwise would draw from the power line and in addition, may feed power back consistent with the local conditions it measures which is usually only voltage. I suppose in theory it could double the variability without overloading the circuit but I assume other limits like local voltage and line resistance would limit the power driven back into the power distribution system.The power distribution network may be modeled as a series of resistors between power sources and power sinks. The voltage drop across the non-zero resistances degrades the load regulation. Previously there were only loads but if the various loads become opportunistic sources, it increases the variability of the loads so the regulation must become worse. Whether it becomes dangerously worse depends on how much impedance margin (conductance margin?) exists in the power distribution network.

author: ocset
author_rank: Super Contributor
timestamp: December 14, 2017, 06:19:51 am
content: Thanks, from the above it definetely seems that disconnected neutral faults, and mains voltage rise due to all the grid tied inverters could possibly be a real issue causing damaging overvoltage...eg , up to 292vac.

author: wraper
author_rank: Unknown
timestamp: December 14, 2017, 08:45:18 am
content: Quote from: treez on December 14, 2017, 06:19:51 amThere is no widespread damaging overvoltage. And how solar power in UK is supposed to be so different from other countries?

author: jc101
author_rank: Frequent Contributor
timestamp: December 14, 2017, 09:10:26 am
content: Further to my post above, we have Solar PV fitted and I an use Air Source Heat Pump to run my office, with a larger one in the house to heat/cool a conservatory and ground floor - no surges, spikes, transients recorded.Even when the Power Networks chap pulled the main supply fuse with the Solar PV knocking out 2kW, no voltage spike was recorded - the UPS just cut on running some essential bits but it didn't show a large over voltage.I know my normal mains is around 248v to 250v just because I'm close to the substation, they couldn't drop the tap down as those at the end of the run would be too low. The only time it was out of limits UK Power Networks attended in an hour or so, and it was resolved a couple of hours after that. They have also left loggers in the meter box outside for a week before to look for anything odd. If the mains is out of spec, call your local network provider, they will *always* come and look as it's a basic safety issue and a sign of problem or impending problem (faulty cable).

author: wraper
author_rank: Unknown
timestamp: December 14, 2017, 09:24:44 am
content: Quote from: blueskull on December 14, 2017, 09:04:35 amTo me it appears he pulled that 292 VAC figure out of his ass to justify problem with their crap products. Not from some real measurements.

author: Zero999
author_rank: Super Contributor
timestamp: December 15, 2017, 07:07:43 pm
content: Most mains switched mode power supplies should be able to withstand 283V, for a decent length of time, as the input components: rectifier, smoothing capacitor and switching transistor are usually rated to 400V. It isn't hard to design something capable of withstanding 292VAC but it shouldn't be necessary, as the mains voltage shouldn't get that high.

author: floobydust
author_rank: Super Contributor
timestamp: December 15, 2017, 11:01:54 pm
content: OP's topic also posted atEDA board'sforums

author: capt bullshot
author_rank: Super Contributor
timestamp: December 16, 2017, 10:56:30 am
content: I've got another suspicion:treez didn't tell which component failed, maybe it was a MOV. If so: they usually don't fail from mains overvoltage (mostly because such overvoltage is rare), but from accumulated degradation by transients or surges. It's their "normal" end of life, they can only stand a certain amount of absorbed energy, if this is exceeded, they fail at nominal voltage with a nice boom if not otherwise protected.

author: hermit
author_rank: Frequent Contributor
timestamp: December 16, 2017, 04:08:29 pm
content: Quote from: capt bullshot on December 16, 2017, 10:56:30 amI asked for that in another of his threads but pretty much got crickets. I get the impression though he may be a tech trying to look good to his boss by coming up with an answer to a problem to prove he can 'punch above his weight'. That or someone that read enough to get a product out the door and now doesn't understand why it keeps failing. When in the repair industry if I replaced a part and the machine still exhibited the same symptoms my first thought was I replaced the wrong part. I seem to have been rare in that case. I've seen instances where the same part got replaced 10 friggin times because the tech was sure they couldn't be wrong. I see the same thinking here with the over voltage.

author: BrianHG
author_rank: Super Contributor
timestamp: December 16, 2017, 05:18:59 pm
content: I just re-read the op's opening post and saw this line:Quote from: treez on December 12, 2017, 10:00:31 pmHe has no actual proof that the AC mains voltage hasn't even gone above 260Vac RMS.

author: 2N3055
author_rank: Super Contributor
timestamp: December 16, 2017, 06:01:57 pm
content: Maybe light reading for OP...https://www.electronicsweekly.com/news/products/led/led-street-lights-need-better-lightning-protection-says-osram-2015-08/https://obo-bettermann.com/media/LED-Leitfaden_en.pdfhttp://www.ledsmagazine.com/articles/print/volume-14/issue-2/features/lightning-protection/implement-overvoltage-protection-for-safe-operation-of-led-street-lighting.htmlhttps://library.e.abb.com/public/2dd9f97fa1916c3983257d11004f829b/1TXH000312B0202_Lightning%20and%20overvoltage%20protection.pdfStreet lights work in very hostile environment... That is one of places where you want to use CAT IV multimeter, for instance, just in case..I have lots of products made to be supplied from that network, and you need to do it right..

author: Brumby
author_rank: Unknown
timestamp: December 17, 2017, 01:30:20 am
content: Quote from: wraper on December 14, 2017, 09:24:44 amIndeed!This is something that has beenscreamingat me from the outset. BrianHG has just had the penny drop:Quote from: BrianHG on December 16, 2017, 05:18:59 pmI have added to his highlighting on the key phrase. Suspicion is NOT evidence! It's a thought experiment - and the basis of that experiment is built on guessing. A successful outcome in this framework is in the same region as a million monkeys on a million typewriters.This guessing game is the absolute wrong way of dealing with the issue. You should know your product well enough so if anyone asks what the failure rate is for any condition, such as overvoltage, you can TELL them.And this is the sort of thing youneedto be doing:Quote from: chris_leyson on December 13, 2017, 09:58:00 pmGuessing, suspicion, supposition, assumption and crossing fingers is not what engineering is about - but if you want to keep travelling down that road, I have a spare typewriter you can have.Does anyone have a spare monkey?

author: Monkeh
author_rank: Super Contributor
timestamp: December 17, 2017, 02:35:41 am
content: Quote from: Brumby on December 17, 2017, 01:30:20 amWell that depends on the pay.

author: Brumby
author_rank: Unknown
timestamp: December 17, 2017, 05:55:56 am
content: I get the feeling that the budget isn't just low ... it's subterranean.If they bring out a milligram scale with the bag of peanuts, I wouldn't be too hopeful.

author: SeanB
author_rank: Super Contributor
timestamp: December 17, 2017, 11:54:26 am
content: Street lighting in general is going to be a 3 phase supply, with a control photocell in the cabinet doing the group switching, and this then allows you to have either shorting photocells or regular light switches in the individual street light luminaires.I would guess all the failed lights are group switched, and do not have a local photocontrol, as those also include as part of the unit a really big, really beefy VDR, and a built in thermal disconnect to allow it to fail safe when subject to overvoltage events of long duration. Shorting caps ( here they are yellow, to tell them apart easily from the ground) do not have the VDR and thermal fuse, just a 30A fusible link inside ( actually just the brass strip, which will blow at around that), and the luminaire has to provide it's own overvoltage protection.Thus a filed neutral, or an intermittently open one, will result in a segment having a floating neutral, and this will be an issue at stub ends or split sections, as they will likely have a non multiple of 3 luminiares on them, so one phase will be dragged down, one will be slightly high and one will be very high, just from the imbalance. Made worse if the install team did not do a correct phase rotation, as they might have more lamps in one phase than the other 2, and you will find the lost neutral made the lowest load phase the loser in the voltage stakes.Lost neutrals are very common, as they generally do not show up easily as failed sections, just long term short lamp life, or well cooked ballasts in magnetic fixtures. Remember the ballast in a regular MV, MH or HPS fixture is designed to operate long term without failure into a shorted lamp, as the failure mode of the lamp is either to be open circuit for MV, or for MH and HPS to have the starter fail short circuit trying to start an EOL lamp without success. Thus the design is to allow up to 130C above ambient of 50C for the insulation, while in normal use they typically run at 130C alone. I have seen regular lost neutral events with the lights mostly working, just either large segments cycling for a half hour after sunset before the lot is running stably, or with a regular sequence of cyclers showing the low phase.Treez, that your lamps are failing from overvoltage says you need to look at either increasing input voltage allowed range to include running phase to phase ( 400VAC input range) ot having an overvoltage trip out that is resettable, and which indicated that input line voltage is poor. Something like a replaceable VDR and thermal fuse unit like a regular HPS starter unit, or a fuse or circuit breaker that can be tripped on overvoltage with a label saying overvoltage tripped this, though the replaceable MOV probably is cheaper than having 1500V rated silicon and 800V rated caps in the supply, along with making the startup supply be capable of long term running on 600VDC main bus rails. however making a fitting that runs phase to phase will be a marketing advantage, as you save in using a 3 core plus PE cable over a 4 core plus PE cable, and only need to make the units group only or supply a matching NEMA twistlock standard photocell that will operate perfectly from 150VAC to 440VAC supplies.

author: rstofer
author_rank: Super Contributor
timestamp: December 17, 2017, 03:37:55 pm
content: Quote from: SeanB on December 17, 2017, 11:54:26 amI don't think this has been proven. In fact, there are no facts other than a failure has occurred. No chart recordings, no DMM logging, no post mortem, it's just a guess. There is a parallel thread trying to prove that air conditioning units are causing line transients. Again, no real data.I wouldn't expect to see 277V (one phase of 480Y/277 plus a neutral) used for street lighting. The distance between source and load tends to be longer and voltage drop is a serious consideration. Back in the day of 1000W Mercury Vapor lamps, the conductors had to be quite large, even at 480V.I have never worked for a public agency. I had read somewhere that they used series wired fixtures at a much higher voltage - this article talks about 2000V.http://www.kbrhorse.net/streetlights/understanding_series.htmlMy experience is limited to parking lot lighting.

author: Monkeh
author_rank: Super Contributor
timestamp: December 17, 2017, 03:46:38 pm
content: Quote from: rstofer on December 17, 2017, 03:37:55 pmI should hope not - like most peculiar voltages, that's a US (and colony hat) specific thing.

author: Unknown
author_rank: Unknown
timestamp: December 17, 2017, 09:26:18 pm
content: Quote from: Brumby on December 17, 2017, 01:30:20 amThat assumes there's actually an issue to deal with, rather than a ... well, I'll just keep my opinion to myself and see how it ends.Quote from: rstofer on December 17, 2017, 03:37:55 pmNo facts, full stop - just claims, and a tendency to ignore any requests for further info.Oh, and occasional obtuse 'misreadings' of responses so far, and thanking of every other comment - relevant or not - in the thread. With suggestions that get sillier and siller with each thread started - noise, mains transients, sustained gross overvoltage, industrial sabotage with directed-energy weaponsI'm guessing the next one will posit that HAARP or sylphs or aliens are to blame...edit: nah, lightning. It's gonna be lightning. A tazer has already been suggested, hasn't it?

author: rstofer
author_rank: Super Contributor
timestamp: December 17, 2017, 09:57:43 pm
content: Quote from: Monkeh on December 17, 2017, 03:46:38 pmIt's not a lot different than 240Y/415 or 230Y/400. 480Y/277V is typically used for industrial service. AFAIK, it is never used for residential and seldom used for commercial.

author: chris_leyson
author_rank: Super Contributor
timestamp: December 17, 2017, 10:29:12 pm
content: Off topic but I lived in a street where every third house lost its supply one night but I don't remember the incadescent light bulbs being any brighter and we didn't have go round and renew them a week later, so one phase failed but it didn't cause any upset apart the homes that lost their supply for a few hours. It's funny isn't it back when we all had incandescent light bulbs you could "see" changes in line voltage, mostly when the weather was bad, but now it's all smoothed out by tiny inverters.

author: stj
author_rank: Super Contributor
timestamp: December 19, 2017, 02:06:30 pm
content: in the u.k. the streetlamps are fed single phase 240v with 100A cable.all lamps are in parallel from a cable running along the street and T'ing off into each lamp.the reason for the 100A cable is to match the feeder when it's spliced and potted, but this is often exploited with 16A outlets up the post for use by x-mas lights or government bullshit like mobile camera pods that look like small trashcans with wifi antenna's on the top.

author: CJay
author_rank: Super Contributor
timestamp: December 19, 2017, 03:26:46 pm
content: Quote from: chris_leyson on December 17, 2017, 10:29:12 pmThat happened to a friend, the pavement lifted quite spectacularly as well but when the cable went it took out every house on the road and there was some sort of short which stuffed enough voltage into fifty or so houses that the electricity company had a team of people going door to door offering immediate payments for faulty appliances so householders could buy replacements.

author: tggzzz
author_rank: Super Contributor
timestamp: December 19, 2017, 04:44:17 pm
content: Quote from: CJay on December 19, 2017, 03:26:46 pmOuch. That would be rather expensive for people suffering from TEA/GAS. "I'll have one 8-digit DMM, three scopes, an 800MHz LA, a 7-decade KVD, an aged calibrated voltage source, a...".

author: Jeroen3
author_rank: Super Contributor
timestamp: December 19, 2017, 05:33:00 pm
content: Don’t accept a direct settlement! You’ll waive further compensation.

author: tggzzz
author_rank: Super Contributor
timestamp: December 20, 2017, 10:00:22 am
content: Quote from: blueskull on December 20, 2017, 09:21:24 amSuch repairsmightbe possible, or not. The problem with metrology equipment isprovingthat's the only damage. Such recalibration and testing is notably expensive.

author: CJay
author_rank: Super Contributor
timestamp: December 20, 2017, 10:21:31 am
content: Quote from: Jeroen3 on December 19, 2017, 05:33:00 pmThey didn't waive anything, the electricity company was obliged under law to compensate them as well as pay for repairs/replacements on damaged appliances and equipment, they also spliced in a shipping container sized generator until the whole run of cable was replaced as well as paying for accommodation for the families who were in houses that were badly affected (damaged wiring/distribution boards)I don't think it could have been handled better

author: ocset
author_rank: Super Contributor
timestamp: January 08, 2018, 08:15:09 pm
content: QuoteThanks,By the way, we spoke to an apps guy from a very well known company which sells MOVs.....and he told us...Quote...so that means that normal mains can go up to 287Vac, ie, 404vpk.

author: tggzzz
author_rank: Super Contributor
timestamp: January 08, 2018, 08:21:50 pm
content: Quote from: treez on January 08, 2018, 08:15:09 pmAre you suggesting thatiswhat happened inyourcase? Do you have any measurements or other evidence that did occur?BTW, your statement of probability is woefully inadequate, to the point of being meaningless.

author: fourtytwo42
author_rank: Super Contributor
timestamp: January 08, 2018, 08:22:01 pm
content: Speechless treez I thought that dead horse was well and truly flogged!!

author: ocset
author_rank: Super Contributor
timestamp: January 09, 2018, 06:11:56 am
content: Thanks,The statement that mains can go up to 287VAC was by a very reputable mov (etc) company apps guy.Im not getting angry about it, if i was angry i would be said to have a short fuse, and i wouldnt be giving you cryptic clues or anything, but it was a very reputable company's apps guy that told us this.

author: Monkeh
author_rank: Super Contributor
timestamp: January 09, 2018, 06:20:36 am
content: Yes, extremely infrequent excursions occur. Note he did not say 'yes, the mains regularly hits 400Vpk-pk and sits there for an hour'.Your devices are failing. Your theories so far include 'UK mains voltages are hugely unregulated', which is plainly bullshit, and 'our competitors are using microwave guns to kill our products', which is tinfoil hat worthy. Do some actual investigation, invest in data loggers, and hire some engineers with a clue.

author: tggzzz
author_rank: Super Contributor
timestamp: January 09, 2018, 09:46:25 am
content: Quote from: Monkeh on January 09, 2018, 06:20:36 amIndeed.It appears I was being too subtle for the OP when I wrote "BTW, your statement of probability is woefully inadequate, to the point of being meaningless"! Memo to self: sometimes politeness isn't effective.

author: jc101
author_rank: Frequent Contributor
timestamp: January 09, 2018, 10:06:28 am
content: Just found some of my old UPS logging data that I must have copied off before the drive failed, not much just 21 April 2016 to 2 July 2016, but a reasonable summary of a couple of months. The records are minute intervals, with min, max, and average over the minute. We also have Solar PV fitted not that you can see it in the data.I've not looked through them but I suspect it is all horribly normal.Note the .zip will expand into a directory, each 24 hours worth is in a separate file.

author: iwtommo
author_rank: Contributor
timestamp: January 21, 2018, 12:32:08 pm
content: I quite enjoyed reading this thread - any updates op?

author: Gyro
author_rank: Super Contributor
timestamp: January 21, 2018, 12:39:30 pm
content: There's nothing to see here, there are many other threads by the OP with unsubstantiated assumptions. No point in dragging this one up again for enjoyment purposes.

author: iwtommo
author_rank: Contributor
timestamp: January 21, 2018, 12:49:31 pm
content: Dangit. Ill keep my eye out!

author: chris_leyson
author_rank: Super Contributor
timestamp: January 21, 2018, 01:25:48 pm
content: I was testing a linkswitch flyback design last week and wondered why it had shut down at 240VAC, is it getting power ? Checked the primary side, 240VAC going in but when I measured 540V DC across the primary smoothing cap, oops turn it off quick. Seems the inverter I was driving it with was putting out 240VAC PLUS 220VDC, oops finger trouble, no wonder the inverter alarmed. But hey everything survived and it's still working, quite impressive, at least the overvolts protect works.

author: ocset
author_rank: Super Contributor
timestamp: January 21, 2018, 03:35:39 pm
content: Thanks, it would be even more impressive if you had a 450V el cap there which survived that(?)And i know your x2 caps would likely have been rated to withstand 1700V for a second or two, but for longer, ....and i reckon they would have gone(?)Your MOV survivied it too(?)

author: chris_leyson
author_rank: Super Contributor
timestamp: January 21, 2018, 04:05:03 pm
content: The primary electrolytic, 450V, and the X caps, 275VAC, survived, I changed the electrolytic however. The MOVs are 510V, clamp at 840V so they might have just started to get warm maybe. Linkswitch max drain voltage is 750V. I'm driving the supply from a 1kW inverter, non isolated, it's more convenient than a variac. The inverter keeps alarming because of the high inrush current into the X caps and my power supply is just a tiny part of a bigger system hence the big X caps.

author: Zero999
author_rank: Super Contributor
timestamp: January 21, 2018, 06:33:19 pm
content: Quote from: chris_leyson on January 21, 2018, 04:05:03 pmYes, electrolytic capacitors can withstand much higher voltages, for quite liong periods of time, without being damaged. I believe they're often formed at a higher voltage, than the maximum rating anyway.If was a good idea to replace the capacitor but perhaps you should replaced the MOVs too?