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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..
I’ll agree with TNS as there is only a single neutral-earth bond. The bond is usually made at the incoming circuit breaker on the board, as this lowers the neutral to earth voltage. If it was TNC-S, there would be a conductor that fulfils both the neutral and earth function. In the setup you have described with only one neutral-earth bond, there isn’t one.
I’ll agree with TNS as there is only a single neutral-earth bond. The bond is usually made at the incoming circuit breaker on the board, as this lowers the neutral to earth voltage. If it was TNC-S, there would be a conductor that fulfils both the neutral and earth function. In the setup you have described with only one neutral-earth bond, there isn’t one.
