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What earthing arrangement is this?
Former Community Member
The supply is from a private transformer in a four core cable 3ph + n. The cable armour is earthed and connected to the MET. However there is also a green and yellow cable connected to the neutral terminal at the main isolator going back to a the transformer casing. The transformer is only 5 or 6 metres away. I think this must have been intended to make it a tncs supply but seems to me to just create parallel neutral conductors. Or is it tn-s-c-s? I have only been able to go off visual inspection because I could not disconnect the supply..
Mildly amusing, im in charge of our facility, but not an electrician, and know our setup was initially described as PNB. It has eight earth rods, and earth tape in a trench for the HV side, and the LV side, cant remember which way around, or if they are connected together, but the HV people added their own earth arrangement (I think theirs was the un-insulated tape and rods)
Anyway, when I describe it as PNB to any electrician, or 'consultant', I get a sort of sympathetic dry smile and a pause, then I'm usually ignored.
Also I note that the EIC forms don't have a tick box for PNB
On occasion, ill find an electrical sat on the floor of the powerhouse, studying the busbars and the N-E link
At a guess, I'd say most electricians don't get to work on or near private transformers much, hence the unfamiliarity, it is frustrating when they assume I'm just being thick though.
Mildly amusing, im in charge of our facility, but not an electrician, and know our setup was initially described as PNB. It has eight earth rods, and earth tape in a trench for the HV side, and the LV side, cant remember which way around, or if they are connected together, but the HV people added their own earth arrangement (I think theirs was the un-insulated tape and rods)
Anyway, when I describe it as PNB to any electrician, or 'consultant', I get a sort of sympathetic dry smile and a pause, then I'm usually ignored.
Also I note that the EIC forms don't have a tick box for PNB
On occasion, ill find an electrical sat on the floor of the powerhouse, studying the busbars and the N-E link
At a guess, I'd say most electricians don't get to work on or near private transformers much, hence the unfamiliarity, it is frustrating when they assume I'm just being thick though.
