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What earthing arrangement is this?

Former Community Member
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..
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  • Former Community Member
    0 Former Community Member

    Johno12345:

    would you go with PNB or TN-S though?




     

    Depends on which capacity I was acting in - for the consumer, I would describe the system as PNB (assuming the DNO own the TX) and insist you achieve bonding as if the system were defined as PME


    If the consumer owned and operated the transformer, I would describe it as TN-S


    It's just semantics - you have a system with a single N-E bond - you don't have a system with a multiple earthed neutral (that would be illegal in the UK, unless you were operating under ESQCR)


    Regards


    OMS
Reply
  • Former Community Member
    0 Former Community Member

    Johno12345:

    would you go with PNB or TN-S though?




     

    Depends on which capacity I was acting in - for the consumer, I would describe the system as PNB (assuming the DNO own the TX) and insist you achieve bonding as if the system were defined as PME


    If the consumer owned and operated the transformer, I would describe it as TN-S


    It's just semantics - you have a system with a single N-E bond - you don't have a system with a multiple earthed neutral (that would be illegal in the UK, unless you were operating under ESQCR)


    Regards


    OMS
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