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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 wonder if the argument could be made should the source earth be made at a point further away than would be considered “direct” such as in the PNB example, that the criteria implicit in the first letter “T” in the codes used for system earthing is not met. In other words unless the connection of the neutral to earth is direct (using the OE dictionary definition of “direct”) then it isn’t a “T” anything earthing system and not recognised by 7671.
I wonder if the argument could be made should the source earth be made at a point further away than would be considered “direct” such as in the PNB example, that the criteria implicit in the first letter “T” in the codes used for system earthing is not met. In other words unless the connection of the neutral to earth is direct (using the OE dictionary definition of “direct”) then it isn’t a “T” anything earthing system and not recognised by 7671.
