Appliances in single phase property damaged by 415v

[I Trippet]

Got an emergency call out from a very worried old lady the other night - the power at her apartment had gone off and the kitchen light was smouldering badly. She'd been on the phone to the DNO (Northern Powergrid), they were telling her to turn the main switch off but she couldn't understand and was frightened. As soon as I walked in I could smell the smouldering, although it had stopped by then as lighting circuit breaker had tripped. The light was an old fluorescent batten with a bulky transformer - it was hot and could tell it was burnt out. At first I thought it must have just failed itself and the MCB has done it's job. Alarm bells started ringing though when she said her tv and table lamp flickered for a short while before going off.

I turned the main switch off at the consumer unit and measured the supply voltage - 415v between line and neutral, 240v between neutral and earth! I said I'd contact Northern Powergrid and there was nothing more I could do for now but reassured her the power was isolated. I was puzzled because the stairwell lights were fine and I could see lights on in other apartments. The next morning, I phoned her as NPG wanted confirmation she would be in for the next three hours. Apparently the other two apartments on that side of the building, directly below hers, also had no power but they had gone to bed so didn't realise until the morning. She phoned me back later to say someone had been to her apartment, checked the supply in the meter cabinet and told her it was fine.

I went back later to put power back on for her, check everything was safe inside and replace the kitchen light. I checked the supply voltage, hey presto 240v line to neutral, 0v neutral to earth. Turned the power on again, numerous light bulbs had blown, a radio, a radio alarm clock and her tv aren't working, the fuses were all fine. Out of curiosity I unscrewed the cover for the radio alarm clock and sure enough several components had blown/melted.

My concern is how little information the engineer from NPG gave about any fault on their network that had now been sorted, just told her it was fine. Well, I wasn't imagining the reading on my tester the night before and several appliances have been damaged that were working. I'm wondering how likely it is that the fault is intermittent and wasn't showing at the time the engineer came - he checked it, said it was fine and cleared off. Or is it possible they are keeping quiet about what had caused it in the hope she won't make any claim off them for any damage?

 

[snowhead]

Sounds like loss of DNO Neutral at a point (D.B ?) common to the 3 (or possibly more) appartments.
It may be an issue within the building network / distribution so not the problem of NPG.
The fault will return if no-one has fixed it.

 

[i=p/u]

He could.of fixed it.and not said.

 

[I Trippet]

Sounds like loss of DNO Neutral at a point (D.B ?) common to the 3 (or possibly more) appartments.
It may be an issue within the building network / distribution so not the problem of NPG.
The fault will return if no-one has fixed it.

That's what I'm thinking. I looked and looked all over the building, couldn't find any service room, all locked doors were just storage cupboards. There is actually a substation on the driveway to the apartments and I suspect they are fed directly from that rather than via a main supply to the whole building, but could be wrong. Phoned people responsible for maintaining the building but they were clueless.

 

[I Trippet]

He could.of fixed it.and not said.

I hope so but would have thought he'd made some comment as to what had happened or acknowledged the fault.

 

[i=p/u]

Less said the better maybe.

 

[UNG]

Got an emergency call out from a very worried old lady the other night - the power at her apartment had gone off and the kitchen light was smouldering badly. She'd been on the phone to the DNO (Northern Powergrid), they were telling her to turn the main switch off but she couldn't understand and was frightened. As soon as I walked in I could smell the smouldering, although it had stopped by then as lighting circuit breaker had tripped. The light was an old fluorescent batten with a bulky transformer - it was hot and could tell it was burnt out. At first I thought it must have just failed itself and the MCB has done it's job. Alarm bells started ringing though when she said her tv and table lamp flickered for a short while before going off.

I turned the main switch off at the consumer unit and measured the supply voltage - 415v between line and neutral, 240v between neutral and earth! I said I'd contact Northern Powergrid and there was nothing more I could do for now but reassured her the power was isolated. I was puzzled because the stairwell lights were fine and I could see lights on in other apartments. The next morning, I phoned her as NPG wanted confirmation she would be in for the next three hours. Apparently the other two apartments on that side of the building, directly below hers, also had no power but they had gone to bed so didn't realise until the morning. She phoned me back later to say someone had been to her apartment, checked the supply in the meter cabinet and told her it was fine.

I went back later to put power back on for her, check everything was safe inside and replace the kitchen light. I checked the supply voltage, hey presto 240v line to neutral, 0v neutral to earth. Turned the power on again, numerous light bulbs had blown, a radio, a radio alarm clock and her tv aren't working, the fuses were all fine. Out of curiosity I unscrewed the cover for the radio alarm clock and sure enough several components had blown/melted.

My concern is how little information the engineer from NPG gave about any fault on their network that had now been sorted, just told her it was fine. Well, I wasn't imagining the reading on my tester the night before and several appliances have been damaged that were working. I'm wondering how likely it is that the fault is intermittent and wasn't showing at the time the engineer came - he checked it, said it was fine and cleared off. Or is it possible they are keeping quiet about what had caused it in the hope she won't make any claim off them for any damage?

So if I'm reading this post correctly a vulnerable old lady was left without power overnight or certainly for several hours on her own, also the DNO only appears to have only responded to the fault call the following day. If this is correct then I feel there is a good reason to raise a complaint
As an electrician attending a property with the fault that is described I would expect on contacting the DNO that an emergency crew would be on site within 2 - 3 hours

I think for the more experienced it is very easy to understand why the DNO is not forthcoming with what the fault was as it would no doubt result in a potentially large compensation claim for the damaged equipment, a fault like this one does not fix itself and must have had some work done by the DNO to correct the problem

 

[snowhead]

I wouldn't be surprised if the other 2 appartments have got as yet undiscovered failed / faulty appliances.
Possibly even others beyond the 3.

They could all end up individually paying to have items fixed when they shouldn't be.

 

[UNG]

I wouldn't be surprised if the other 2 appartments have got as yet undiscovered failed / faulty appliances.
Possibly even others beyond the 3.

They could all end up individually paying to have items fixed when they shouldn't be.

This is where I feel you have to be a bit more forensic in how you go about your faultfinding and reporting of the issue IMO, knocking on neighbours doors and doing a quick check of their supply, taking a look outside at the street lighting and the other properties along the street usually gives a good indication of the extent of the problem and it all helps when you make that call to the DNO if you have some understanding of the distribution system to indicate where the fault may be. These days with cable theft it would not be that uncommon to find a substation has had it earth cabling removed causing the neutral point to float

 

[I Trippet]

So if I'm reading this post correctly a vulnerable old lady was left without power overnight or certainly for several hours on her own, also the DNO only appears to have only responded to the fault call the following day. If this is correct then I feel there is a good reason to raise a complaint
As an electrician attending a property with the fault that is described I would expect on contacting the DNO that an emergency crew would be on site within 2 - 3 hours

I think for the more experienced it is very easy to understand why the DNO is not forthcoming with what the fault was as it would no doubt result in a potentially large compensation claim for the damaged equipment, a fault like this one does not fix itself and must have had some work done by the DNO to correct the problem

Yes, she rang them first and they told her to isolate the supply and call an electrician. At that point it wasn't clear what had happened, they could have reasonably just thought it was a faulty light fitting and nothing to do with them. When I realised what the problem was I phoned back but said they wouldn't treat it as an emergency as long as the supply was isolated, and call again in the morning. So no, she had no power overnight which is bad, but she was just relieved to go to bed knowing the light wasn't going to carry on burning!

 

[I Trippet]

I wouldn't be surprised if the other 2 appartments have got as yet undiscovered failed / faulty appliances.
Possibly even others beyond the 3.

They could all end up individually paying to have items fixed when they shouldn't be.

I'm going back tomorrow I said drop off some more light bulbs for her and I'll try asking them. How likely is it to for them to successfully claim for damage from NPG?

 

[UNG]

Yes, she rang them first and they told her to isolate the supply and call an electrician. At that point it wasn't clear what had happened, they could have reasonably just thought it was a faulty light fitting and nothing to do with them. When I realised what the problem was I phoned back but said they wouldn't treat it as an emergency as long as the supply was isolated, and call again in the morning. So no, she had no power overnight which is bad, but she was just relieved to go to bed knowing the light wasn't going to carry on burning!

So what did you identify the problem as?
As to the DNO response I would have certainly got the name of the person you spoke to as leaving a vulnerable old lady without power overnight is an extremely calous action and worthy of some retraining, I think I would have been asking to speak to the duty supervisor

I'm going back tomorrow I said drop off some more light bulbs for her and I'll try asking them. How likely is it to for them to successfully claim for damage from NPG?

I assume when you say them you are only referring to your customer, I don't think they have any chance of a claim due to the way it was reported to the DNO and the response they gave it

 

[Dartlec]

It may well be worth getting her to speak to the neighbours. If 3 separate apartments have had damaged appliances - along with your test result that night, I would think they would find it hard to argue that it was nothing to do with them (assuming there isn't a BNO involved).

At the very least I would put something in writing to the DNO - from the customer ideally, but with your 'site report' included (Just a description of your actions, on business letter headed notepaper.)

I'm surprised that they thought an elderly lady would be fine without any power overnight - at the very least a complaint in writing will make someone look at the call logs, etc.

Not sure if her insurance company might be worth mentioning this to as well (assuming she has one and was going to claim( - they might well be interested if they can offset any of their claim onto the DNO.

 

[I Trippet]

So what did you identify the problem as?
As to the DNO response I would have certainly got the name of the person you spoke to as leaving a vulnerable old lady without power overnight is an extremely calous action and worthy of some retraining, I think I would have been asking to speak to the duty supervisor

I assume when you say them you are only referring to your customer, I don't think they have any chance of a claim due to the way it was reported to the DNO and the response they gave it

The supply voltage was too high. Yes I agree it was bad of them.

I meant anyone that's had equipment damaged. When I spoke to them I made it very clear that I was getting 415v at the supply.

 

[LastManOnline]

I wouldn't be surprised if the other 2 appartments have got as yet undiscovered failed / faulty appliances.
Possibly even others beyond the 3.

They could all end up individually paying to have items fixed when they shouldn't be.

Ironically I had just finished sending an invoice tonight to the DNO for an exact same situation. It was you Snowhead who replied to my (similar) query a, few weeks ago and you mentioned your son got compensated from DNO for damages he suffered.
I had no issues when I contacted them. They achknowledged liability and simply asked for a list of damages and bank details. I think it would be rare if there was no record somewhere of a power outage. In any case, from what I have read here there certainly appears to be sufficient circumstantial evidence

 

[UNG]

The supply voltage was too high. Yes I agree it was bad of them.

I meant anyone that's had equipment damaged. When I spoke to them I made it very clear that I was getting 415v at the supply.

Do you have any idea why the voltage would be so high?

 

[I Trippet]

Do you have any idea why the voltage would be so high?

Possible broken neutral, I couldn't investigate any further as it's the DNOs domain.

 

[UNG]

Possible broken neutral, I couldn't investigate any further as it's the DNOs domain.

It's quite clear from your responses that you were totally out of your depth with this fault and lack some very basic knowledge of the electricity distribution system and what causes faults like this to occur

 

[I Trippet]

It's quite clear from your responses that you were totally out of your depth with this fault and lack some very basic knowledge of the electricity distribution system and what causes faults like this to occur

So instead of getting personal, how about you tell us your theory!

Not quite sure how I can be "out of [my] depth" when the fault is on the supply side and acknowledged it's the DNO's responsibility and contacted them.

 

[LastManOnline]

It's quite clear from your responses that you were totally out of your depth with this fault and lack some very basic knowledge of the electricity distribution system and what causes faults like this to occur

Is that a windup? What more could he have done?

 

[UNG]

So instead of getting personal, how about you tell us your theory!

Try reading post #9 for a start or did you miss that
Checking the voltage a few other properties is all useful info to the DNO
You identified the local sub did you look around it for any sign damage
What voltage was on the stairwell lights

Not quite sure how I can be "out of [my] depth" when the fault is on the supply side and acknowledged it's the DNO's responsibility and contacted them.

You accepted the DNO's response that having isolated the property at the main switch it was safe, what about the meter was that isolated or did a 240v meter still have 415v connected to it creating a potential fire hazard, how many other apartments within the building and adjacent properties unknowingly also had potential fire hazards because of the over voltage
If the DNO didn't want to turn out I would have been talking to the fire brigade due to the potential fire hazards the fault might create I'm sure the fire brigade would get a response from the DNO

Is that a windup? What more could he have done?

No and see above

Maybe I approach things differently, over the years I have reported many network faults to the DNO's local to me, some of the faults are not that apparent but they are faults to which they respond and repair, yes I have a good working knowledge of three phase and how the DNO network is constructed and operates and it all helps when reporting a fault, had quite a few DNO guys on the ground comment that it's a pity more electricians are not as clued up and report faults

I suppose it was good that it was a TNS supply could have been very interesting on a TNCS Supply

 

[I Trippet]

Is that a windup? What more could he have done?

Yes clearly.

Should have broken in to the substation to have a closer look. Or maybe turn up to the DNOs head office with a loaded shotgun and tell them to send someone out or I'll blow their head off!

 

[ElectricSeamus]

That’s one very unhappy soul. Talk to someone, please.

 

[I Trippet]

Deleted

 

[I Trippet]

Deleted.

 

[UNG]

Should have broken in to the substation to have a closer look.

I don't recommend that but having a look to see if is secure or at the ground around the sub to see if has been recently disturbed could indicate that the earthing has been stolen

Or maybe turn up to the DNOs head office with a loaded shotgun and tell them to send someone out or I'll blow their head off!

But who would answer the next fault call?

I don't know your skill or qualification level as your profile doesn't tell me much.
I have tried to make you see the bigger picture of what the fault could do, it is harder on some occasions now to get the DNO to respond than it was 40 years ago for the reasons stated previously and the more information you have about the scale of the fault increases the pressure on them to respond by putting boots on the ground. I have had many arguments with the call handlers and asked for it to elevated to supervisors and managers and not accepted the refusal for immediate attendance so being able to stand your ground with the maximum amount of information you can find really helps

Look at the information you had
You have a neutral at 240v in one property in an apartment block how many other properties in the same block have got a neutral connection at 240v and what about the surrounding properties, knocking on a few doors and doing a quick mains check if the fault is present get them to call the DNO as well, as this is an apartment block and there is now a potential fire hazard in it should you evacuate the block while the DNO sort it out (more pressure or the DNO to respond)

May be speak to the DNO and see if you can meet up with one of their team and discuss their response to this fault and how if you have a similar fault you could better report it and get the DNO on site quicker, even using this thread as a reference and discuss the points raised

 

[Lister1987]

It should be noted that certain events are reportable to HSE under ESQCR - What must be reported? - ESQCR - HSE - https://www.hse.gov.uk/esqcr/what-must-be-reported.htm

Admittedly your run-of-the-mill sparky isn't listed, meter maids are however bit I would rather file a report as a competent person so that I know it's been done, rather than solely trusting the DNO, unless you can secure a (meaningful) unique reference from the DNO.

 

[UNG]

It should be noted that certain events are reportable to HSE under ESQCR - What must be reported? - ESQCR - HSE - https://www.hse.gov.uk/esqcr/what-must-be-reported.htm

Admittedly your run-of-the-mill sparky isn't listed, meter maids are however bit I would rather file a report as a competent person so that I know it's been done, rather than solely trusting the DNO, unless you can secure a (meaningful) unique reference from the DNO.

After a quick read of that it looks like the fault in this thread is not reportable

 

[Simon47]

So instead of getting personal, how about you tell us your theory!

Not quite sure how I can be "out of [my] depth" when the fault is on the supply side and acknowledged it's the DNO's responsibility and contacted them.

As said, knowing the basics of the distribution systems in use and the fault symptoms is useful even though they are out of your control.
That you measured 415V suggests a loss of neutral in the supply network. Turn to page 48 of the Wiring regs and look and figures 3.8 and 3.9 - from the sound of things, 3.8 for TN-S. Doodle in a star transformer for the supply - the local substation. Now consider what happens if the neutral cable between substation of consumer gets cut/broken. You now have a floating neutral, and the individual phase-neutral voltages for each phase will depend on the relative loadings.
In the traditional depiction of a star transformer, the arrangement of the windings corresponds with the phase diagram for the three phases. Once you lose the neutral, then the common point as seen by the loads will not be in the middle of the star.

In the best case, the loads are all the same, the phases are balanced, and there will be little difference to normal. But that's rare. Worst case is that one phase is heavily loaded, while the others are only lightly loaded. In this case, the phase-neutral voltage of the heavily loaded phase will be reduced, and those of the other phases will be increased - the neutral will drift until the currents are balanced.

Of course, as bulbs blow, fuses/breakers trip, and things generally let the magic smoke out - the loads on the phases showing higher voltages will reduce, and the imbalance will get worse. In extreme, you could end up with nothing on two phases, and a large resistive load on one phase - so one phase now gets very little because the neutral point is now pulled out to that corner of the phase diagram, while the other two phases now get 415V P-N (the neutral is now effectively one of the other phases).

Unfortunately, the <insert you own expletives here> who nick metal don't care about what damage they cause. So stealing a neutral earthing link for a substation might get them a tenner in scrap value, but cause many thousands in damage. The DNOs tend to hush up the problem, especially if someone is clever enough to get themselves injured or killed - the HSE people tend to take the attitude that the DNO should have done more to protect the sort of people who break into a locked compound, with security fencing, and with plenty of "DANGER OF DEATH" signs - and then interfere with what is obviously live electrical equipment ?

 

[Lister1987]

Unfortunately, the <insert you own expletives here> who nick metal don't care about what damage they cause. So stealing a neutral earthing link for a substation might get them a tenner in scrap value, but cause many thousands in damage. The DNOs tend to hush up the problem, especially if someone is clever enough to get themselves injured or killed - the HSE people tend to take the attitude that the DNO should have done more to protect the sort of people who break into a locked compound, with security fencing, and with plenty of "DANGER OF DEATH" signs - and then interfere with what is obviously live electrical equipment ?

I'd argue they should do more to discourage it, make the interior live so that they get a belt and think twice, or no more....either-or I'm not fussed, safe entry is granted by permit to work and remote isolation. Does make you wonder why they don't use vertical ground electrodes, as opposed to a horizontal arrangement that is easier to nick

 

[Simon47]

The ground mat isn't just about grounding, it's also about creating a safe environment for people. So even if they put 'kin big earth rods in, they'd still need the ground mat covering the whole substation site to avoid any possibility of dangerous potential differences from being present.
And even if you could rule that out, you'd need some large bonding cables - which would also be a target.
At least the earthing mat is buried which makes it less trivial to steal than above ground cable.

Unfortunately, the nature of the electricity distribution system is such that it's inherently difficult to secure - a lot like railway infrastructure. I was a talk a few years ago where it was mentioned that in some places they bury cable ducts under the middle of the track bed (i.e. under the sleepers), and a whole meter down to try and reduce cable thefts.

I've also seen adverts (aimed at large users like railways operators) for cables with the customer name embedded within the cable - as in, a small tape, with the name punched in it, embedded in the copper strand layup. Short of chopping the cable into tiny fragments, or melting it, it's impossible to destroy the evidence, and thus make it traceable when it turns up in a scrapyard where it shouldn't be.

 

[JD6400]

In fairness to the op , even if he had looked deeper into the fault what more could he have done !?
If they are not coming out , that is what you are getting .
Admittedly for those of us that have dealt with these , jobs worth ----ers on the end of a so called utilities help line , we would have a new somewhat larger ring piece ripped.in no time at all .

And to honest , out of the 8 or 9 times that I have come across lost neutrals , it has never shown 415v present between either phases or neutral.
The only time I have seen 415v was at the beginning of the year on a completely new build farm . They had just moved in about a week before hand , and one Sunday night the neutral on load side of the new TX failed and as it burnt out it curled over and made connection with L2 .
Luckily it only seemed to obliterate the house , but that came to just over £60k. ?
The first I found out about it was a call at 6:30am on Monday morning , as we had installed 12KW of solar on the grain store when we wired the shed up, and the spark appointed by the DNO , who had been there doing an EICR and cataloguing the damage from 11:15 pm on Sunday night !!!! Was not sure about the 3ph pedestal grain fans and the solar.

 

[Lister1987]

After a quick read of that it looks like the fault in this thread is not reportable

If it didn't fall under ESQCR, you could try RIDDOR, even if it doesn't qualify there either, it's putting pressure on the DNO. It would be interesting to see HSE actually get involved in cases like this but they seem all too happy leaving it to the DNOs to deal with, brush under the carpet, not maintain thier system and give bonuses to the fat cats for a 'good job' managing the networks

 

[I Trippet]

As said, knowing the basics of the distribution systems in use and the fault symptoms is useful even though they are out of your control.
That you measured 415V suggests a loss of neutral in the supply network. Turn to page 48 of the Wiring regs and look and figures 3.8 and 3.9 - from the sound of things, 3.8 for TN-S. Doodle in a star transformer for the supply - the local substation. Now consider what happens if the neutral cable between substation of consumer gets cut/broken. You now have a floating neutral, and the individual phase-neutral voltages for each phase will depend on the relative loadings.
In the traditional depiction of a star transformer, the arrangement of the windings corresponds with the phase diagram for the three phases. Once you lose the neutral, then the common point as seen by the loads will not be in the middle of the star.

In the best case, the loads are all the same, the phases are balanced, and there will be little difference to normal. But that's rare. Worst case is that one phase is heavily loaded, while the others are only lightly loaded. In this case, the phase-neutral voltage of the heavily loaded phase will be reduced, and those of the other phases will be increased - the neutral will drift until the currents are balanced.

Of course, as bulbs blow, fuses/breakers trip, and things generally let the magic smoke out - the loads on the phases showing higher voltages will reduce, and the imbalance will get worse. In extreme, you could end up with nothing on two phases, and a large resistive load on one phase - so one phase now gets very little because the neutral point is now pulled out to that corner of the phase diagram, while the other two phases now get 415V P-N (the neutral is now effectively one of the other phases).

Unfortunately, the <insert you own expletives here> who nick metal don't care about what damage they cause. So stealing a neutral earthing link for a substation might get them a tenner in scrap value, but cause many thousands in damage. The DNOs tend to hush up the problem, especially if someone is clever enough to get themselves injured or killed - the HSE people tend to take the attitude that the DNO should have done more to protect the sort of people who break into a locked compound, with security fencing, and with plenty of "DANGER OF DEATH" signs - and then interfere with what is obviously live electrical equipment ?

That's pretty much what I said, but for whatever reason that made it clear that I "lack some very basic knowledge of the electricity distribution system", which is actually completely wrong.

Anyway, I've spoken to the lady again, she's been in contact with Northern Powergrid and they have confirmed their engineer didn't do any investigative work, just came to the apartment, checked the supply voltage, said it was fine and left. They apparently don't seem to think there is any fault, despite me explaining to them 3 times - first in the early hours when it happened, and twice the next day (had to call back because she was out at first and they wanted confirmation she would be there) - that I was getting 415v when I was called out. So how they can be satisfied that there isn't a fault and that it won't reoccur is beyond me.

 

[marcuswareham]

That's pretty much what I said, but for whatever reason that made it clear that I "lack some very basic knowledge of the electricity distribution system", which is actually completely wrong.

Anyway, I've spoken to the lady again, she's been in contact with Northern Powergrid and they have confirmed their engineer didn't do any investigative work, just came to the apartment, checked the supply voltage, said it was fine and left. They apparently don't seem to think there is any fault, despite me explaining to them 3 times - first in the early hours when it happened, and twice the next day (had to call back because she was out at first and they wanted confirmation she would be there) - that I was getting 415v when I was called out. So how they can be satisfied that there isn't a fault and that it won't reoccur is beyond me.

It would appear as if the DNOs have little regard for high impedance / open neutral faults, scary !

 

[Sparkgap]

It would appear as if the DNOs have little regard for high impedance / open neutral faults, scary !

Not only those faults: I have a substation halfway down my garden which supplies most of my road via overhead lines. We've had two faults of interest: first was a failure of the HV connection onto the transformer which required chopping the incoming HV cable and reterminating it. While this was being done over a couple of days we were hooked onto a supply from a transformer in the next road over. As a result my house voltage (normally 245V) varied from 230V down as low as 178V. I did phone the DNO to check on progress as I was a bit concerned at the low voltage possibly damaging equipment in my house but the guy on the phone said there was nothing they could do (which is more than likely). Fortunately I had no issues and the fault was sorted relatively quickly.
The second fault was loss of one of the HV phases feeding the substation which resulted in my supply dropping to about 88V. This was due to tree branches striking the overhead wire (according to the DNO engineer I talked to when he came to check the line they had cut back on cutting back(!) nearby trees generally and this could be a problem in future with strong winds). One surprising thing was some of my lights still worked: normal GLS tungsten bulbs gave a dull glow, most of my LED lamps didn't work but a couple of LED lamps plus the DAB radio in the kitchen all worked perfectly! I assume these were all switch mode psu and able to cope with the low voltage.