Discuss Appliances in single phase property damaged by 415v in the Electrical Engineering Chat area at ElectriciansForums.net

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UNG

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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

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UNG

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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

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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

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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

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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

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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

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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
 
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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.
 
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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 !
 

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