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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..
When I first read the OP, I assumed that the green/yellow cable was a protective conductor which was augmenting the armour of the 4-core cable, which I assume was insufficient on its own.
Now what puzzles me ('cos I can just about cope with things on a domestic scale) is why this cable is marked as a protective conductor (514.4.2) when it is connected to a neutral terminal.
When I first read the OP, I assumed that the green/yellow cable was a protective conductor which was augmenting the armour of the 4-core cable, which I assume was insufficient on its own.
Now what puzzles me ('cos I can just about cope with things on a domestic scale) is why this cable is marked as a protective conductor (514.4.2) when it is connected to a neutral terminal.
