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Safe Disconnection to Undertake Work.

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Scene. An old farm building now used as a double glazing frame maker's workshop.


The supply comes from an old shed about 40 metres away, where the meter is. The old shed has some 70s/80s rusty M.E.M. isolators that feed several S.W.A. cables that exist the shed in many directions underground. I suspect that one feeds the main farmhouse, another a rented cottage and the others various farm buildings. There is no clear labelling of the isolators.


What is the best way to locate the frame maker's  building supply where I have to work?


Somewhere I have a circuit i/d set, if I can find it, but that will need access to the live parts and I do not wish to turn off the wrong isolator.


Z.


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  • 0
    Chris Pearson:

    I still don't understand a pair of cottages with an earth adjacent to the transformer and no other. DNO says PME, so that must be what it is.


    The DNO might prefer you to treat it as if it were PME so that they are then free to alter it to real PME in the future. That seems to be the general advise these days for "presented as TN-S" supplies - treat them as if they could be PME.


    Also if there's a CNE between the first electrode and the consumer's N-PE link, then it's TN-C-S anyway and all the dangers of a broken CNE would apply just as if it were a proper PME system with multiple electrodes on the distribution system.


       - Andy.


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  • 0
    Chris Pearson:

    I still don't understand a pair of cottages with an earth adjacent to the transformer and no other. DNO says PME, so that must be what it is.


    The DNO might prefer you to treat it as if it were PME so that they are then free to alter it to real PME in the future. That seems to be the general advise these days for "presented as TN-S" supplies - treat them as if they could be PME.


    Also if there's a CNE between the first electrode and the consumer's N-PE link, then it's TN-C-S anyway and all the dangers of a broken CNE would apply just as if it were a proper PME system with multiple electrodes on the distribution system.


       - Andy.


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