Uhoh local electric board have screwed up - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: August 27, 2020, 01:54:24 pm
content: So my power went out Sunday night, was back on an hour later. Suspected flooding at a sub station.However today while installing a little smart meter thing it came up and said the voltage was 204V.I immediately suspected the meter was faulty, so I measured the mains with the DMU. 206V. Tried a plug socket, 206V.... tried another plug socket, 207V.it's supposed to be 240V (or 230V +/- 10%). So 207V would possibly be in spec, but very unusual.I reported it as a fault, because if it's dropping something like 34V somewhere due to a dodgy cable it could cause a fire in the sub-station.They could have just hooked out street into a heavily loaded phase because the other phase was broken somehow.

author: paulca
author_rank: Super Contributor
timestamp: August 27, 2020, 03:20:08 pm
content: Emmm.... it's now 196VI feel like I'm slowly moving towards the USA's 110V.At some point things that need 240V will start failing.

author: paulca
author_rank: Super Contributor
timestamp: August 27, 2020, 03:31:36 pm
content: 191VLooks like I should get the candles out.

author: Ian.M
author_rank: Super Contributor
timestamp: August 27, 2020, 03:34:54 pm
content: Smells like a lost neutral. Imbalanced load causes the neutral potential to wander and some phase voltages go up while others decrease.CAUTION: If it is a lost neutral, if the phase you are on sheds load, your supply could go as high as 415V. This may cause a fire hazard.DANGER: Depending on your grounding arrangements lethal voltages may develop between supposedly grounded metalwork and the real earth ground. DO NOT TOUCH OR APPROACH GARDEN TAPS etc.IMHO you should isolate everything you can immediately and call the UK power networks emergency line (0800 31 63 105) 0r just 105 from landline or UK mobile to report your situation and seek advice.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 27, 2020, 04:23:15 pm
content: Check voltage live to earth and neutral to earth

author: wraper
author_rank: Unknown
timestamp: August 27, 2020, 04:28:40 pm
content: Unplug everything you can. Because there is possibility something will fail. Not simply due to under-voltage. But because voltage might jump up as well, not to say electricians playing with neutral wire is potentially deadly for equipment. I know several precedents.

author: Cerebus
author_rank: Super Contributor
timestamp: August 27, 2020, 04:36:10 pm
content: Well, we've heard nout for an hour so I think we must presume that paulca is sitting in 'darkness and silence' at the moment, or trying to find his way around a chunk of live, steaming ground.

author: wraper
author_rank: Unknown
timestamp: August 27, 2020, 04:36:16 pm
content: Quote from: CJay on August 27, 2020, 04:30:19 pmDid that office manager at least get a slap on his/her ass for being an idiot?

author: paulca
author_rank: Super Contributor
timestamp: August 27, 2020, 05:09:42 pm
content: Nah, I'm still here. 194V at the moment. Went as low as 183V.Measured a plug socket...E-N = 1.3VE-L = 195VSo all that means is it's not "my" neutral that's fecked?Anyway, I have already phoned the power network provider (NIE Networks) when it was 204V, they logged it. I sent them a message on facebook when it hit 190V. They said "Thank you, I'll pass that on"

author: paulca
author_rank: Super Contributor
timestamp: August 27, 2020, 05:29:19 pm
content: Update: Power company sent an engineer out who turned the power off, pulled the main fuse and tested the supply coming in... it was low at point of entry.So... phew. If it had turned out to the consumer side that little visit would have cost me about £200.He said he would let them know, but couldn't say what they would do about it.

author: Gyro
author_rank: Super Contributor
timestamp: August 27, 2020, 05:37:52 pm
content: Quote from: paulca on August 27, 2020, 05:09:42 pmIt's unlikely that you would see anything significant onyourE-N as you are probably on a TNS-C-S (PME) system where E and N are joined at the input supply termination (it might be a different situation with a fork stuck into the garden though - don't try it!They accidentally lifted the Neutral while doing an underground cable repair around here a couple of years ago. The supply company had a whole bunch of contractors going door to door very quickly, turning off everyone's consumer unit, doing basic checks and handing out leaflets and phone numbers to call if any appliances went faulty over the next 4 weeks. They were quite good actually, and did the rounds again a month later to double check for any issues.Luckily, our phase must have gone low. I initially thought it had killed an outdoor PIR light but when I looked closer, it had water in it.A bit of a shame as we could have got a few free appliance upgrades, a new TV or something.

author: Gyro
author_rank: Super Contributor
timestamp: August 27, 2020, 05:39:31 pm
content: Quote from: paulca on August 27, 2020, 05:29:19 pmThat's good. It's pretty hard to lose 40V on the consumer side of the supply without a very nasty smell!Edit: Somebody else is probably 'benefiting' from your lost 40V! Good call Ian.M!

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 27, 2020, 07:05:58 pm
content: Quote from: paulca on August 27, 2020, 05:29:19 pmprobably the sub station is faulty or overloaded. my parent's house (the whole neighborhood) is running at 190V for many years already since we moved there. company never bother to upgrade the sub station.

author: Monkeh
author_rank: Super Contributor
timestamp: August 27, 2020, 08:28:50 pm
content: Quote from: Gyro on August 27, 2020, 05:37:52 pmThe natural state of a PIR is full of water and dead. Working ones are a fluke.

author: paulca
author_rank: Super Contributor
timestamp: August 27, 2020, 08:31:59 pm
content: And back to normal... for now.Power dropped, came back on 1 minutes later with voltage restored.2 minutes later the engineer called at the door and asked if my voltage was back up. I told him it. So apparently it wasn't just me, it was the whole street, I was the only one to phone it in. Something to do with a cable fault which they know about which knocked the substation out on Sunday night. They re-energised it then and all was well, explaining my power cut on Sunday night. He thinks today it tripped one of the HV lines but the "Back feeds" held, so the sub station stayed on, but the voltage was dropping as it was overloaded at that point. They will probably need to dig up the street to find and fix the cable fault though.

author: Ian.M
author_rank: Super Contributor
timestamp: August 27, 2020, 09:13:07 pm
content: Quote from: paulca on August 27, 2020, 08:31:59 pmEnergy efficient lighting is a safety hazard!In days of yore, most or all of the street would have noticed due to the color shift of incandescent lighting during severe brownouts and its likely that 10% or so would have phoned it in. Also, the engineer could have simply walked down the street and noted a significant proportion of the houses that were affected by the appearance of any visible lighting. The utility company tries to keep the load evenly distributed between the phases, so if every third house was dim that would point to a phase fault. If excessively bright bulbs were seen as well it would point to an open neutral.Nowadays, low line conditions may make energy efficient lighting dimmer, or even make it flicker more, down to the point where it cuts off, but wont cause a color shift. Also everything except heating and motorized appliances is likely to have a SMPSU which will accommodate a significant input voltage decrease by drawing more current (incidentally making the effects of a lost neutral for anyone on the high phase much worse) so unless the householder notices their kettle is particularly slow to boil or their vacuum cleaner lacks oomph, they may well not be aware they are suffering a brownout.IMHO it should be mandatory for modern smart meters to alarm on incoming under or over-voltage, outside the permitted limits.

author: IanB
author_rank: Super Contributor
timestamp: August 28, 2020, 01:27:57 am
content: It would be cool to have a device that plugs into a three pin socket with an LED display on the front showing the current mains voltage and frequency. You could just plug it in somewhere at eye level like in the kitchen and keep an eye on it. It probably could be about the same size as a USB charger.

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 28, 2020, 04:17:00 am
content: https://www.ebay.com/itm/Socket-Tester-Voltage-Meter-LCD-Display-Intelligent-Detection-Frequency-90-250V/363080863641?hash=item54894e4f99:g:myIAAOSwRD1fPZ2xhttps://www.ebay.com/itm/AC-80V-300V-LCD-Digital-Voltmeter-Plug-in-Home-Voltage-Meter-Monitor-US-PLUG/193160881088?hash=item2cf94923c0:g:QPYAAOSwtDRfFrvG

author: paulca
author_rank: Super Contributor
timestamp: August 28, 2020, 10:05:46 am
content: I might set an alarm on my voltage monitor. The easy win is to change the graph above to add a threshold which turns the graph red at 230V - 6% which is the spec.The device I'm using for that the ShellyEM is partly intended for overload protection. You can put it on a single (or dual) circuits and monitor the voltage, power and reactive power and it has a 2 Amp 240V Contactor pilot signal to switch that circuit on/off if it hit's a overload trigger. I don't have any contactors with a 240V pilot signal, so I just use it to monitor power usage.What I can't workout is if the power is real or apparent. Still some research I suppose.Nor am I sure of it's accuracy. Right now I'm showing 383W with -183W reactive. Does that mean I have 200W real power as billed or 383W real power.I'm sure I'll find out when I research it as I would like to extrapolate real, apparent and power factor and maybe current from those.

author: Gyro
author_rank: Super Contributor
timestamp: August 28, 2020, 10:40:43 am
content: Quote from: Mechatrommer on August 28, 2020, 04:17:00 amIronically, you need to avoid the more professional socket testers because they draw sufficient current to minimize false detection of 'ghost' voltages / leakages. They normally have a maximum time limit or duty cycle. As for the cheap Chinese ones, who knows - dissipation, what's that?

author: Jeroen3
author_rank: Super Contributor
timestamp: August 28, 2020, 11:23:47 am
content: Do you have smart meters?My smart meter reports the voltage back to the grid company every 15 minutes, I can see it with 5 second intervals.

author: perieanuo
author_rank: Frequent Contributor
timestamp: August 28, 2020, 11:28:19 am
content: hi,that's why voltage supervision relays (with an contactor drived by the relay for fast decoupling and correct current rupture), combined with lightning surgers (less than 200 euros for like 6kW power or more) it's a good ideain my new apart one day after a big storm I got 90Vac voltage, I had half of small consumers working, like led bulbs, router etc.no big ones of course.Investigation: 2 phases down (0volts AC) and one to 90V!!!and really 90V, not some floating voltage on digital multimeter.the f...ng company who built the residential area supply (220Vac and maybe 250KVA) FORGOT to implement on the tri-phase transformer phase-protection techniques like if one the three phases are down, they must cut the transformer.well, capitalism screws us all, they cut cost everywhere...best regards,pierre

author: Cerebus
author_rank: Super Contributor
timestamp: August 28, 2020, 11:43:02 am
content: Quote from: paulca on August 28, 2020, 10:05:46 amYou could watch what your monitor says versus what the electricity company's meter says over a long enough period. The electricity company's metershouldbe reading only real power. Obviously their's is in kWh so you're going to have to do a little numerical integration. If they agree, your monitor is reading real power, if not apparent power..

author: paulca
author_rank: Super Contributor
timestamp: August 28, 2020, 01:04:09 pm
content: Quote from: IanB on August 28, 2020, 01:27:57 amI had one of these:https://www.amazon.co.uk/Nevsetpo-Monitor-Consumption-Electricity-Calculator/dp/B07H1ZFVFM/It was in the garage where I was using it to work out how much a laundry wash and dry costs me. (About £0.50 for circa 3 kWh)The ShellyEM said: 204VThe Extech RMS meter said 203VThe power monitor plug said 204VI believe Big Clive tested one against his HOPI meter and it turned out to be better than it, particularly on low load. The odd chinese products are actually quite good. Though I don't think using one for compliance measurements would cut it on code.

author: janoc
author_rank: Super Contributor
timestamp: August 28, 2020, 01:07:10 pm
content: Quote from: Gyro on August 28, 2020, 10:40:43 amYou mean the situation when the meter "dissipates" in a puff of black smoke?

author: paf
author_rank: Regular Contributor
timestamp: August 28, 2020, 01:09:35 pm
content: One from many years ago. After some work at the local power transformer, a water pump stopped working...The pump (electric motor) still turned on (noise from the pump), but we had no water out from the well.Cause: the guys from the power company switched two phases by mistake and the tri-phase electric pump motor started to rotate in reverse...

author: paulca
author_rank: Super Contributor
timestamp: August 28, 2020, 01:13:50 pm
content: So question. The supply engineer (the second guy who called) mentioned "The HV side was effected but the backfeeds held."Does he mean that there are multiple paths in the system and while the HV line quick disconnected the alternative path was trying to supply the street over loading the transformer, ie power was not meant to be coming in that way, but was?

author: IanB
author_rank: Super Contributor
timestamp: August 28, 2020, 04:29:02 pm
content: Quote from: paulca on August 28, 2020, 01:13:50 pmI think there can be multiple paths in a system to provide redundancy. I believe I have read about this being more common higher up the distribution chain, so, for example, they can disconnect a particular circuit for maintenance while not interrupting supply to consumers.The mention of backfeed is interesting. It implies a transformer was backfeeding the 11 kV side from the 240 V side and keeping the 11 kV energized, even though the main 11 kV feed was disconnected at source.This kind of situation is not uncommon. If you look closely at any local substation transformer you will see prominent warning signs to isolatebothsides of the transformer before working on it, not just the incoming high voltage side. The danger of other supplies backfeeding the secondary and energizing the disconnected primary is all too real.

author: paulca
author_rank: Super Contributor
timestamp: August 28, 2020, 05:10:57 pm
content: It sort of makes sense that they didn't detect that fault when fixing things on Sunday night. Or maybe it happened again.But the transformer was feeding the HV side. From memory his words were.... "...and that affected the HV side...".I put the 3 phase lost neutral argument as best I could, but he rolled his head and said, "That can happen.", "We have very few faults like that though."I tried the falling voltage meaning more current point and he said, "You'd think it would work like that, but it's more complicated."So I guess, there was more than one HV power source on the local 240V network, my transformer's HV side dropped out but the other source' 240V was able to push current back through onto the HV through my transformer, keeping both the HV appearing normal to them and while supplying twice as many houses... so the voltage sagged as it saturating the transformer.

author: paulca
author_rank: Super Contributor
timestamp: August 28, 2020, 05:39:33 pm
content: And another thing....WTF is this 20min cycle load spike?I've tried with almost everything off... and it's still there. Fridge, freezers? Nope. Turn all the PCs off, nope. Turn off the kitchen equipment, nope. Pushed TEST on the boiler trip, nope.Mystery 160W for 3-4mins every 20 minutes, like clockwork, night and day.I do need to confirm the readings with a second meter tomorrow.