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DNO cable

Kelly Marie Angel

Hi just a quick question I used to know this but now can't remember if the old PILC cable joined to a PVC covered cable as a replacement for a faulted section  how do they keep the earth impedance down? Especially if the PILC length is now a lot less than it was supply's in properties along the road are a mix of TNS and CNE  Thanks

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  • 0

    They make it all TNS by bonding the neutral to the PILC sheath.

    Slight typo from David there I suspect - I think it should have read: They make it all TN-C-S by bonding the neutral to the PILC sheath.

      - Andy.

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    They make it all TNS by bonding the neutral to the PILC sheath.

    Slight typo from David there I suspect - I think it should have read: They make it all TN-C-S by bonding the neutral to the PILC sheath.

      - Andy.

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  • 0 in reply to AJJewsbury

    Correct Andy , I was posting with my phone and it's awkward!

  • 0 in reply to AJJewsbury
    AJJewsbury said:

    They make it all TNS by bonding the neutral to the PILC sheath.

    Slight typo from David there I suspect - I think it should have read: They make it all TN-C-S by bonding the neutral to the PILC sheath.

      - Andy.

    Not quite ... the issue is it's tricky and you'd need to check with the DNO.

    Some arrangements where it's not separate neutral and earth (SNE) all the way back to the transformer are still classified as TN-S (confusingly), and PME conditions do not apply.

    Where the system is "full TN-C-S" and PME conditions apply, the consumer is supposed to be notified by the DNO.

    I know this goes against our strict definitions of "TN-S", but it's important to note that "TN-C-S" is not always PME (as implied, but not implicitly stated, by BS 7671), and there are some "strictly TN-S by the logic and book" earthing arrangements, such as some PNB arrangements, where PME conditions apply. This situation all comes out of ESQCR and G12/4.

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