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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..
We are all agreed that the transformer's internal wiring is not included.
But as Alan says the earthing of the N at source isn't internal to the transformer. Indeed if you look carefully at some rural systems where both HV and LV are overhead you'll often see N earthed not even at the pole the transformer is mounted on, but at the next pole several tens of meters away (as that's a simple way of segregating the LV and HV earths).
We are all agreed that the transformer's internal wiring is not included.
But as Alan says the earthing of the N at source isn't internal to the transformer. Indeed if you look carefully at some rural systems where both HV and LV are overhead you'll often see N earthed not even at the pole the transformer is mounted on, but at the next pole several tens of meters away (as that's a simple way of segregating the LV and HV earths).
