This sort of thing can occur - what are we looking at there actually, as there seem to be 4 wires on the nearby LV pole and yet only 2 to the TX ? or is there concentric cable in use ?

Is that 'just' the HV earth for the transformer can and core, or is it also the reference for the LV system neutral as well ?

Loss of HV earth or a combined earth can be very nasty on  non 3-phase  transformer as there are several nano-farads between the HV windings and the core, so even  when all is working well, there is a non zero current in that lead, and it has quite a large open circuit voltage behind it, perhaps half of the HV phase to ground voltage.

On a 3 phase system, the HV to  earth leakages cancel  to a degree.

Loss of just the LV earth can, as you describe lead to some odd problems with clearing faults, and things that should be at or near earth potential becoming dangerous when there is a fault elsewhere.

The tacit BS7671 assumption that the network is perfect upstream of the company fuse or whatever  is  not always correct is it ?

Mike

mapj1 said:

what are we looking at there actually, as there seem to be 4 wires on the nearby LV pole and yet only 2 to the TX ? or is there concentric cable in use ?

Just a single-phase tx with 2 line and 2 neutral. The LV line goes quite some distance.

Around here a 2nd pole a little way from the Tx pole is common - usually the LV Earth is done at that 2nd pole, and the 1st pole is just the HV earth - a "hot" site in old school terminology. If the LV side is PME there'd likely be some more electrodes further away still, so the LV earthing shouldn't be too bad.

  - Andy.

LV earth may be good but a dangling HV earth on a hot site single phase pole pig can pack a punch, Approach with caution and report to DNO !!

They will approach with suitable gloves or isolate on  the HV side if someone has to climb to repair the damage. There used to be a video on youtube showing one where the earth had been stolen but I cant find it quickly.

M