Domestic supply cable

[Tristar]

In the course of my builder digging out foundations for an extension, some concrete had to be cleared away during which the supply cable to the house was damaged. Power supply was uninterrupted, however the cable metal sheath is damaged. Am I correct that this cable should have been laid at a minimum depth of 450mm? It was at a depth of 260mm below the surface.

 

[bernardgreen]

You need to contact your DNO ( Distribution Network Operator ) and inform them of the damage if you haven't already done so.

http://www2.nationalgrid.com/uk/Our-company/electricity/Distribution-Network-Operator-Companies/

What appears to be armouring may be the combined neutral and earth conductor and if this is broken then your installation will become extremely dangerous. While it is not broken now ( supply still there ) it may fail in the near future, if the insulation between the live inner core and the outer conductors is damaged and then fails it could be a small explosion underground.

 

[Tristar]

You need to contact your DNO ( Distribution Network Operator ) and inform them of the damage if you haven't already done so.

http://www2.nationalgrid.com/uk/Our-company/electricity/Distribution-Network-Operator-Companies/

What appears to be armouring may be the combined neutral and earth conductor and if this is broken then your installation will become extremely dangerous. While it is not broken now ( supply still there ) it may fail in the near future, if the insulation between the live inner core and the outer conductors is damaged and then fails it could be a small explosion underground.

Thanks for that, my leccy is dealing with it, and it will not be underground in future as it is being moved, however I would still like to know if its depth was legal at 260mm.

 

[westie101]

There is actually no "legal" depth for DNO cables, there are expected depths and a lot of advice from the HSE on how to avoid damaging them which also makes NO reference to legal depths.

The DNO may use their discretion an whether to charge for the damage, which should have been reported immediately to ensure safety.
Even if the damage seems minor the situation is such that the cable could fail with a minor explosion that could injure anyone in the immediate vicinity. The builder should have reported it immediately, not you, not the electrician

It should also be noted that the HSE advice (HS (G) 47)does have a separate section covering the situation where concrete is involved, the actions that should be taken when this is disvovered and the response that should be made by the DNO.
That the cable got damaged in this situation shows that the builder is unaware of this vital piece of safety advice, which could be a worry.

Or to put it another way, when we attend a report of a damaged cable we ask the "damager" if they are aware of HS(G)47, they usually answer yes (even if they are not)
One answering yes in this case is lying as cables in concrete require to be dealt with in a specific way, which has not occurred
This would ensure that I will raise a charge for the repair

 

[Tristar]

There is actually no "legal" depth for DNO cables, there are expected depths and a lot of advice from the HSE on how to avoid damaging them which also makes NO reference to legal depths.

The DNO may use their discretion an whether to charge for the damage, which should have been reported immediately to ensure safety.
Even if the damage seems minor the situation is such that the cable could fail with a minor explosion that could injure anyone in the immediate vicinity. The builder should have reported it immediately, not you, not the electrician

It should also be noted that the HSE advice (HS (G) 47)does have a separate section covering the situation where concrete is involved, the actions that should be taken when this is disvovered and the response that should be made by the DNO.
That the cable got damaged in this situation shows that the builder is unaware of this vital piece of safety advice, which could be a worry.

Or to put it another way, when we attend a report of a damaged cable we ask the "damager" if they are aware of HS(G)47, they usually answer yes (even if they are not)
One answering yes in this case is lying as cables in concrete require to be dealt with in a specific way, which has not occurred
This would ensure that I will raise a charge for the repair

Thanks very much, I will ensure this is done.

 

[kai]

That supply cable may be fused at up to 800 amps or so, so it will be dangerous to any passers by if it were to cause an explosion.