DP Isolation and PME (fault)

[plugwash]

The neutral normally carries very little but with two phases connected together at the supply it would be taking a LOT of current. Particularlly if the load was already a bit imbalanced in a direction that added to the huge imbalance caused by the bodge so it wouldn't surprise me at all that the neutral was higher than normal.

Frankly it shocks me that anyone signs off on allowing a bodge like that. Did they warn three phase customers first?

 

[Lectrician]

Did they warn three phase customers first?

I would guess they knew there was none.

 

[bernardgreen]

Did they warn three phase customers first?

Most of the property on the damaged supply was residential. Only one residential has three phase

The last 200 yards and 6 houses (including the one with 3 phase ) is overhead and ends on the pole outside our house. The DNO isolated that 200 yards from the damaged cable by pulling the pole mounted fuses and then patched it to another supply that ends on the same pole.

 

[securespark]

With two phases distributed, the neutral would have had to take a little more current than usual due to the imbalance. This extra current would have caused a greater voltdrop in the neutral, and hence the reason why it floated noticeably apart from mother earth.

All overhead and UG networks do have the CNE conductor 'staked' down regularly to try to keep the neutral voltage as steady and as close to earth as possible.

yes that is what the 'multiple' in protective multiple earthing (PME) stands for. You have an earth rod at the end of the cable, the LV earthing at the substation and depending how long the run of that cable is, maybe another one out of a straight joint.

Not just to keep the PD down, but so that if one grounded connection goes down, the chances of a PD developing are reduced.