UK Mains Expectations.... - Page 1
Forum section: electronics / beginners

author: CM800
author_rank: Frequent Contributor
timestamp: June 25, 2017, 09:08:05 pm
content: I changed my florescent bulb back in for an incandescent one (the florescent ones are SHIT at lighting my room)and I noticed that it keeps dimming and then brightening up randomly....I put a multimeter on the mains, it seems to be changing by as much as 30V at some points, depending on load (of other houses, not mine)For a gauge I plugged my hair-dryer in, if I turn my 2000W hair-dryer on to max, it drops down by 10V from whatever voltage it was previously, we are usually at 230V, but I've measured it going down to 200V at some points.At what point is it worth complaining about to whoever does the grid in our area? (southern electrical or whatnot) I suspect the transformer is overloaded locally, heck, we had a brownout about a month back too.

author: Gyro
author_rank: Super Contributor
timestamp: June 25, 2017, 09:25:00 pm
content: It depends heavily on your location - if you're out in the country on a pole transformer then maybe you would maybe expect that from the tranformer. If you're in a suburban street then a 2kW load causing a 10V drop is nothing to do with the transformer - it has to do with the resistance in your domestic wiring.

author: Monkeh
author_rank: Super Contributor
timestamp: June 25, 2017, 09:30:08 pm
content: A 10V drop under such a small load suggests a bad joint. I suggest investigating before it gets worse.

author: electr_peter
author_rank: Unknown
timestamp: June 25, 2017, 09:35:35 pm
content: Quote from: CM800 on June 25, 2017, 09:08:05 pmBetter LED lamps also may provide good CRI (color rendering index) if you are interested. But that is beside the point.QuoteIncandescent light bulb's brightness is very sensitive to supply voltage variation. DMM measurements add quantitative data about variation. 30V is a bit much.Can you describe "randomness" in more detail? Is it periodic? Does it repeat in minutes/hours?Locally we have 230 VAC +/- 10% supply regulation meaning 207-253V is allowed. However, supply is stable at ~230V and 30V variation would be very unusual.I would be concerned with info that you provided. Sounds like local supply is overloaded or there is massive leakage or cables/connections are damaged.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 25, 2017, 09:35:47 pm
content: Nominal supply is 230V +/- 10% so if it is lower than 207V or higher than 253V you have a problem, 200V is out of spec.Quote from: Monkeh on June 25, 2017, 09:30:08 pmMeasure as close as you can (electrically) to the meter, if it is dropping there you can complain. If not then it would, indeed, be wise to check the house wiring.Edit: Nominal voltage above is for the EU. I thought that you were in the UK but now realise that the Union Jack belonged to Gyro. Mentioning whereabouts you are might help in this case.

author: CM800
author_rank: Frequent Contributor
timestamp: June 25, 2017, 09:46:30 pm
content: Plot thickens.Just measured it again, now it's 240V at socket and at the distribution board.Turning the hairdryer on and off does very little, only 3-4 V drop at plug beside it.

author: Zero999
author_rank: Super Contributor
timestamp: June 26, 2017, 07:56:12 am
content: Quote from: grumpydoc on June 25, 2017, 09:35:47 pmIt's actually 230V +10% -6%. There is a proposal to change it to +10% -10% but that will never happen now because of brexit.http://www.twothirtyvolts.org.uk/pdfs/site-info/Explanation_230Volts.pdfQuote from: CM800 on June 25, 2017, 09:46:30 pmThat's a significant voltage drop.What's the power rating of the hair dryer?

author: grumpydoc
author_rank: Super Contributor
timestamp: June 26, 2017, 08:17:43 am
content: Quote from: Hero999 on June 26, 2017, 07:56:12 amI must admit I thought that changehadbeen made.If not I agree it is unlikely now.QuoteI think the OP already said 2kWSo, about 9A @ 230VImplying a loop resistance of 0.33\$ \small \Omega\$25mm2has a resistance of 1.55mOhm per metre per conductor so 110m or so is needed for that resistance - not implausible for an overhead run in a rural location.

author: tggzzz
author_rank: Super Contributor
timestamp: June 26, 2017, 09:01:10 am
content: Quote from: CM800 on June 25, 2017, 09:08:05 pmWas it windy? Do you have overhead cables? If so it is entirely possible that some screws have become loose, cables were flapping and contacts were varying.When that happened to me, they sent a man with a (fibreglass) ladder to fix it

author: Zero999
author_rank: Super Contributor
timestamp: June 26, 2017, 09:20:28 am
content: Quote from: grumpydoc on June 26, 2017, 08:17:43 amOh yes, he said 2000W in the first post when he also mentioned a voltage drop of 10V, which would be an impedance of 1Ohm at 10A, then he tested later and the voltage drop was 3V to 4V. Unless there was a measurement error, it indicates there's a loose connection somewhere.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 26, 2017, 09:28:01 am
content: Quote from: Hero999 on June 26, 2017, 09:20:28 amOr other loads appearing coincidentally.Either way if the OP has good evidence of the supply voltage going to 200V (as he said) that is out of spec whether we are at +/- 10% or +10/-6 % so should report it as a fault.

author: Gyro
author_rank: Super Contributor
timestamp: June 26, 2017, 09:34:16 am
content: Quote from: Hero999 on June 26, 2017, 07:56:12 amActually that reference doesn't quite tell the full story. Previously 230V countries stayed at 230V +/-10% (the harmonised European standard). Previously 220V countries adopted 230V +6%/-10%. The UK, previously 240V, adopted 230V +10%/-6%. In other words, no one changed a damn thing, they all fall within the 230V+/-10% standard already, it was just a paper exercise.The UK is still nominally 240V (+/-6%, unless they've taken the oportunity to relax the low end a bit). A typical European compromise (EDIT: Nothing to do with Brexit, it already happened years ago).

author: Jeroen3
author_rank: Super Contributor
timestamp: June 26, 2017, 09:48:48 am
content: Quote from: CM800 on June 25, 2017, 09:08:05 pmBefore you start complaining to the utility, make sure your own installation does not have bad connections or poor wiring.It's not only an inconvenience because of the voltage drop and light flickering, but also a fire hazard.

author: Ian.M
author_rank: Super Contributor
timestamp: June 26, 2017, 09:52:13 am
content: You need to determine whether the drop is due to a fault in your building's wiring, or is due to a fault on the utility's wiring, probably outside your property. Unless you have the correct instruments, PPE and knowledge and experience (not likely if you are asking about mains supply issues here), measurements at the feed to your consumer unit should, for your own safety, be done by a licenced electrician.Get a quote from a licensed electrician to check for excessive supply voltage variation, and check with the utility if they will charge you for the callout if no fault is found with their wiring, then decide who to book first! As previously mentioned, in rural areas fed by overhead lines, the odds are its a problem with the utilitiies wiring, but in urban areas its far more likely to be your wiring. In urban areas, as they try to keep the phases balanced by distributing properties on any street evenly between them, the odds are your immediate neighbours aren't on the same phase, but if you can, ask three neighbours either side if they are having similar problems - if anyone else is, it increases the probability that its the utility company at fault.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 26, 2017, 09:58:02 am
content: Quote from: Gyro on June 26, 2017, 09:34:16 amTo be fair the harmonisation was never about anyone changing their nominal supply voltage.It was about defining what voltages equipment had to work at/withstand to be sold into the common market.It is relevant here though as it changes the margins of acceptable - 240V +/- 6% is 225V to 254V, 230 +10/-6 is 216 to 253V and 230 +/-10% is 207 to 253V. Having a lower low-side value also probably helps the supply companies as it means dropping lower under load is acceptable which, in turn, will reduce demand a bit.So whichever way you slice it, it would be reasonable for the OP to ask his supply company to look at the cabling if he has good evidence that it is going down to 200V a the point that the supply enters the property.

author: Gyro
author_rank: Super Contributor
timestamp: June 26, 2017, 10:36:50 am
content: QuoteYes, sure, I should have included that - you would expect the electicity company to aim to stay well within the tolerance margin. Whichever spec you use, 200V is clearly well outside it. Cost-wise it's hard to say whether it would be better to get a licenced electrician to to a resistance check of the domestic wiring or to call Southern Electric and face the (admittedly remote) chance of them disconnecting an unsafe installation. If they suspect a supply issue then their first step will probably be to put in a logger for a few days.We still don't know anything about the OP's location - rural versus typical town street has abigimpact on possible scenarios.@CM800maybe you can fill us in on this if you want the best help out of us?P.S. Just an aside. When I was designing volume consumer stuff, we always designed (non universal input) stuff to operate correctly at 198V (220-10%) to 264V (240+10%). Natural caution and EN..something or other.