Builder needing advice after damaging temporary supply to new build!

[westward10]

And nothing is impossible given the correct circumstances.

 

[Lucien Nunes]

Of course where I wrote CNE conductor above, it might be a PEN, but as it caused such far reaching effects it seems not to have lots of decent ground paths shunting it.

 

[westward10]

Of course where I wrote CNE conductor above, it might be a PEN, but as it caused such far reaching effects it seems not to have lots of decent ground paths shunting it.

Your scenario seems highly likely. The OP really needs a technical report stating the cause and effect of what occurred then I suspect the charges maybe reassessed.

 

[Lucien Nunes]

The only way to ensure safety would be to use a local earth for all CPCs

Yes the site temp was presumably on TT, but if the service cable was connected to a PME system, an L-CNE fault current could have blown a defective PEN O/C elsewhere, where other properties were relying on it.

E2A Ah I see your point, the site should not have had stray voltages on its CPCs / bonding due to the failure if it was TT, although we don't know what was shorted to what at the fault location so it's difficult to predict. If the floating section had come into good contact with true earth, and we know the hole was full of water, there could have been all sorts of voltage gradients about the site.

 

[Wilko]

Hi - apologies if this has already been said or is rubbish (please correct me) - if the DNO cable was concentric, then our man has exposed the N by nicking the cable. The N would have to already have been well above a few volts to cause the bubbly water that's reported. So either more than a nick or distribution system already in trouble, or both (?). A pic of the damaged cable might be interesting .

 

[elsparko]

That's exactly what I thought Richard, sounds like they are trying to blame me for a fault in there network! The engineer got a shock when he touched the outer sheathing wires as he took his gloves off, he obviously wasn't expecting them to be live!

but the cable was damaged, he should have at least tested the sheath

the only time i willingly touch conductors is when i know 100% that they are dead.

 

[elsparko]

Hi - apologies if this has already been said or is rubbish (please correct me) - if the DNO cable was concentric, then our man has exposed the N by nicking the cable. The N would have to already have been well above a few volts to cause the bubbly water that's reported. So either more than a nick or distribution system already in trouble, or both (?). A pic of the damaged cable might be interesting .

i was on a large steading job, diggers outside working on the underground heating system, then a loud bang and some smoke coming from their ditch

hydro boys came out and sorted it and everything was back to normal, so i sense that the suppliers network is not up to standard in this particular case

still, the labourer caused the fault(straw) that broke the camels back

if i had any inclination there may be a live cable buried, id use a trowel with an insulated handle!

anyone ever seen the video of "travellers" stealing railway lines? using axes to cut the cables...

 

[Lucien Nunes]

(please correct me) - if the DNO cable was concentric, then our man has exposed the N by nicking the cable. The N would have to already have been well above a few volts to cause the bubbly water that's reported. So either more than a nick

Much more than a nick... OP says there was a loud bang so he almost certainly shorted L - PEN within the cable, and it was that fault current that broke the continuity upstream.

 

[elsparko]

any pictures of the bit that hit the live cable? how much of the steel is missing?

 

[stevels4]

DNO will only install a temporary supply using TT, they insist on having the Earth Rod in place or they won’t connect meters.

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.

 

[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

 

[shaun rosier]

RESULT!!!!

The company backed down today and are now only charging for the damage we did to the supply cable! They didn't admit fault of course but said they are dropping all the overhead cable charges!

Can I say a big thanks to all you guys who obviously know your stuff as we used your technical explanations in our replies to the company which I'm sure made them think twice about taking it further!!

Thanks again and if anyone needs building advice I'm happy to return the favour!

 

[elsparko]

RESULT!!!!

The company backed down today and are now only charging for the damage we did to the supply cable! They didn't admit fault of course but said they are dropping all the overhead cable charges!

Can I say a big thanks to all you guys who obviously know your stuff as we used your technical explanations in our replies to the company which I'm sure made them think twice about taking it further!!

Thanks again and if anyone needs building advice I'm happy to return the favour!

i have a block of granite, i need it turned into dust, how much?

5x5x5metres

 

[shaun rosier]

Kim Jong-Un might be able to help you on that one! He has a few nukes he needs to get rid of now!!

 

[elsparko]

Kim Jong-Un might be able to help you on that one! He has a few nukes he needs to get rid of now!!

could just drive down to trumps golf course and start digging up the greens with a putter, maybe now they are mates he will just fire them at me

 

[ruston]

i have a block of granite, i need it turned into dust, how much?

5x5x5metres

We used to get similar problems when it would not fragment with a blast.

Stock photo but we used to get them like this regular.

 

[elsparko]

We used to get similar problems when it would not fragment with a blast.

View attachment 42752
Stock photo but we used to get them like this regular.

no idea how guys managed to drill this stuff out before electric motors!

think id go mad with the cold chisel and twist method

 

[ruston]

no idea how guys managed to drill this stuff out before electric motors!
think id go mad with the cold chisel and twist method

Amazing really when you think of what the ancients done with it.
We got close to a village and had to restrict the amount of blasting and as bad luck would have it we hit limestone . The blasting would only split it. We had Caterpillar D9 dozers in with with single ripper picks fitted ; they hardly looked at it.

 

[elsparko]

Amazing really when you think of what the ancients done with it.
We got close to a village and had to restrict the amount of blasting and as bad luck would have it we hit limestone . The blasting would only split it. We had Caterpillar D9 dozers in with with single ripper pics fitted ; they hardly looked at it.

seen a video of a pensioner on youtube splitting huge boulders with just a cold chisel and bolster

seen guys struggle to drill through concrete slabs without splitting it! they just cant resist using hammer mode even though its soft like butter to just drill through

does amaze me how civilizations with no heavy transport could move such stones

heres the vid of the old bloke

 

[ruston]

seen a video of a pensioner on youtube splitting huge boulders with just a cold chisel and bolster

seen guys struggle to drill through concrete slabs without splitting it! they just cant resist using hammer mode even though its soft like butter to just drill through

does amaze me how civilizations with no heavy transport could move such stones

heres the vid of the old bloke

I worked with an old stone mason that could do that . He worked at a famous quarry in Northumberland .
He used to hue the winstone from the solid and hand cut the sets for the old cobbled streets . He was amazing to watch.

 

[elsparko]

I worked with an old stone mason that could do that . He worked at a famous quarry in Northumberland .
He used to hue the winstone from the solid and hand cut the sets for the old cobbled streets . He was amazing to watch.

when i was really young i threw a big metal spike straight into the chuckies below me, ended up with a stone stuck in my throat for ages LOL , just think of all the man hours it must have taken to cobble all the roads of britain at one time

 

[johnduffell]

think of all the man hours it must have taken to cobble all the roads of britain at one time

Isn't that what they used to do to pass time before they invented smart phones?

 

[elsparko]

Isn't that what they used to do to pass time before they invented smart phones?

the romans didnt get to cobble much of the roads here, if only the romans knew about north sea oil, i doubt they would have built the wall