Builder needing advice after damaging temporary supply to new build!

[shaun rosier]

Hi Everyone,

I would really appreciate some advice on the following problem I have had with a temporary electric supply.

We are in the process of building a couple of flats and had a temporary supply put in, no problem! However much later when one of the labourers was putting the hockey sticks into the new boxes and needed to bust through some of the footing he stupidly damaged the cable with a breaker and grazed the cable exposing the outer sheath (cable was not severed) and there was a load bang and the cable started fizzing in the hole which was filled happened to be filled with water!

We called the supplier out to repair and two guys turned up to repair the cable and one of them got a zap of the cable as he tried to repair it. Before this the same labourer got a zap off the site cabin handle after he went through the cable.

We then had the two neighbours that lived down the lane come out and say there TVs had blown up!

The engineer said that there was no way that us going through the cable would have caused the TVs to blow and it was just a coincidence! I just don't believe that as it happened at exactly the same time!

He then called his boss and about 5 vans pulled up within about 20mins and started to take down the over head cables to the main road. They replaced a stretch of the cable and were working on one of the poles.

I don't remember exactly what our sparky said but he thinks that the supply cable had an existing fault and that the sheathing was somehow live and that's what caused the cabin to become live when it was damaged and the cable was possibly 'vibrating' and caused a surge down the line to blow up the TV's. This he says may be why the engineer got a shock as he didn't expect the sheathing to be live!

The reason why I could really do with some advise on this one is because the supplier is charging me for the whole team that turned up (about 6 guys) for about 5 hours with the overhead work when I was just expecting to pay for the two guys for a couple of hours to fix my temporary supply not half the road! I have offered to pay them what I think is fair but they say they will bring me to court if I don't cough up in full!

Any advice would be most welcome from the pros!

cheers

Shaun

 

[LankyWill]

DNO’s do not connect meters, they will run the service cable to a cut out which may also be TNCS, MOPs supply and fit the meters.

I am aware of this, it was just a generalisation.

 

[shaun rosier]

Looked at the latest email from the supplier and this is what they said!

"The damaged caused an open circuit neutral fault. Where the cable has been damaged it has caused a surge down the overhead network and we have had to replace the ABC conductor and overhead span to rectify this."

"Had there been a fault on the network already we would have known as we would have received prior call outs."

 

[shaun rosier]

Thanks for all your responses by the way, really appreciate all the advice/info!

 

[elsparko]

Thanks for all your responses by the way, really appreciate all the advice/info!

im surprised how the fault caused 2 t.vs to "blow up"

my dad wanted a new t.v but mum said no, so he poured some water down the back of it that night and we had a flatscreen the next day

if it damaged their network it suggests their network was substandard to begin with

not that i know a great deal about overhead lines so i could be wrong but my logical lizard brain tells me to go with what seems most obvious

 

[westward10]

Looked at the latest email from the supplier and this is what they said!

"The damaged caused an open circuit neutral fault. Where the cable has been damaged it has caused a surge down the overhead network and we have had to replace the ABC conductor and overhead span to rectify this."

"Had there been a fault on the network already we would have known as we would have received prior call outs."

The fault on your cable should have caused no detrimental issue to the supply network.

 

[shaun rosier]

blew up one of their kettles as well apparently!

 

[telectrix]

don't the DNO fit fuses to prevent such damage to their precious network?

 

[elsparko]

blew up one of their kettles as well apparently!

if i was you, id hire a solicitor as it sounds like the 2 neighbours are taking the michael, and so are the supply company.

 

[elsparko]

don't the DNO fit fuses to prevent such damage to their precious network?

yeah but this sounds like it was the cable before the service head

 

[telectrix]

substation has fuses as well.

 

[westward10]

I have said before you need to ask for a technical report.

 

[elsparko]

substation has fuses as well.

if their fuse didnt react then their system design is a failure, so they should be liable for their own overheads, then the labourer responsible for the damaged cable from overhead to temporary

the 2 neighbours banging on about their appliances can as good as be ignored

guarantee if you open up these appliances and have a gander it will tell you all you need to know.

 

[johnduffell]

The dno design their network on the basis that there won't be many faults, none of this fault protection nonsense.
Since they can just claim back any costs of blowing up other things from whoever they blame for a fault.
No idea who wants to claim a kettle, not the best scam to pull, or has Mr Dyson started making fancy expensive kettles?

 

[Richard Burns]

The ESQCR regulations require the generator or distributor to "ensure, as far as reasonably practicable, his network does not become disconnected from earth in the event of any foreseeable fault" and a "distributor shall ensure that a supply neutral is connected with earth at... such other points as may be necessary to prevent, so far as is reasonably practicable, the risk of danger arising from the supply neutral conductor becoming open circuit"
A short circuit on a supply conductor is eminently foreseeable and they have already admitted to having an open circuit neutral.
This does not detract from the dangers of the construction company operations but should limit their responsibility to the area of actual damage and not subsequent failures on the existing network.

 

[alasdairp]

Lucian Nunes posted the best response imho. There was almost certainly an existing distribution network fault on that part of the network. Broken Neutrals, especially on early XLPE 3-core cables when the Neutral and earth are carried by the armour (i.e. the Neutral does not have a 4th internal conductor), are suprisingly common - water gets in the the armouring eventually rusts through. Everything usually continues to work ok because of the use of PME. I have detected many of these faults over the years. One of the worst cases was about 360 amps going back through the building steelwork and various undergound metal pipes to the substation. In another (even worse) case the DNO Electricity had fogotten to reconnected the Neutral in a 1 MW internal substation for a large office and shopping complex - all currents were returning via the protective Earth!!! The only problems reported were "wobbling CRT computer monitor displays" due to the high EMFs caused by the current loops formed.

What I suspect happened in thei builder's case here was that there was an existing broken Neutral in the part of the network supplying his temporary supply and the damage current (the 'bang') went to the 'Earth' connection which also happend to be working as the Neutral to houses also on the same 3-phase LV circuit feed . This will have caused some homes to get a sudden short drop in supply voltage and people on one of the phases (not the one hit by the jack hammer) to get a short high voltage surge - up to maybe 360 volts (or so) - hence the damaged TVs.

The idea of PME was to try to prevent this sort of thing from happening - the downside is that serious Neutral faults can exist which are not detected or corrected. I tried (at a high level) to get the ENA to implement an LV 3-phase cable overall current-balance check whenever they did work on a network - but they said it would add too much cost and bother. It is so simple to do with a large clamp or Rogowski coild meter - so I suspect they really just did not want to detect a load more Neutral connection faults.

I would definitely contest it and ask for a #detailed# report on #all# the work that was required to be done on the LV network and the reasons why. I suspect they are taking the p*** at your expense. The TV people should also be able to claim compensation from the DNO.

 

[Lucien Nunes]

Alasdair's explanation is even more convincing - that it was a PME service that had already lost its neutral upstream and carried on without symptoms. The DNO will have a job arguing that your service cable fault directly caused that problem without at the same time revealing that they were not complying with the ESQCR. Subject to the specifics in the report, I can't see how you could be held responsible for it, or the consequential damage.

FWIW I 've fixed a ton of electronic gear that has been blown up by a wandering neutral. It's a specific hazard in my industry with lots of temporary 3-phase TNS on single-pole connectors and cables. Unlike lightning, which can destroy every semiconductor in one hit, the modest over-voltage of 400V maximum only normally affects the PSU and often just a few components within it. Repair was usually viable and well worth doing, although we sometimes had to write things off for insurance reasons depending on the circumstances. That was professional kit though, where a rack might be worth £100k or more.

 

[elsparko]

Alasdair's explanation is even more convincing - that it was a PME service that had already lost its neutral upstream and carried on without symptoms. The DNO will have a job arguing that your service cable fault directly caused that problem without at the same time revealing that they were not complying with the ESQCR. Subject to the specifics in the report, I can't see how you could be held responsible for it, or the consequential damage.

FWIW I 've fixed a ton of electronic gear that has been blown up by a wandering neutral. It's a specific hazard in my industry with lots of temporary 3-phase TNS on single-pole connectors and cables. Unlike lightning, which can destroy every semiconductor in one hit, the modest over-voltage of 400V maximum only normally affects the PSU and often just a few components within it. Repair was usually viable and well worth doing, although we sometimes had to write things off for insurance reasons depending on the circumstances. That was professional kit though, where a rack might be worth £100k or more.

100k? pop that down to the scrappy at lunchtime and go 50/50 with the boss aye?

maybe worth letting the supply company take you to court, then get a payout in your favour for your time etc.

 

[Toneyz]

It is where the neutral and earth of the consumer's installation is joined together so on the supply side you have the live conductor and the outer armouring in the combined neutral/earth conductor.

Why the dumb Rigpig at least have the decency to correct me or give the other viewpoint.

 

[123]

Why the dumb Rigpig at least have the decency to correct me or give the other viewpoint.

Chances are it's accidental on a phone. I've done it a few times, even when just trying to scroll down the screen

 

[johnduffell]

Chances are it's accidental on a phone. I've done it a few times, even when just trying to scroll down the screen

Yeah every time i post something loads of people accidentally hit disagree or dislike, really annoying