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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

    In  a lot of DNO literature they sidestep the loaded 'is it really proper PME ?' question by referring to CNE 'Combined Neutal and Earth' or SNE 'separated Neutral and earth'.

    Avoids saying things like

    'my supply is TNS-C-S-C-s '

    which is actually quite representative of the situation you may have in an older street with a few repairs and new streetlights etc, as at every new joint or new service tap the N and E will be bonded, but the older properties  will still present a TN-S service head.Hence the general advice that if we are not certain to assume PME-like conditions apply, as these are the most onerous.

    We may not be allowed more than one NE bond on a genset, or indeed any on the consumer side of a mains supply, but the networks, who have more control over their cables and routes, and most importantly know better the current rating of their earthing arrangements, are more than happy to have many.

    Mike

Reply
  • 0

    In  a lot of DNO literature they sidestep the loaded 'is it really proper PME ?' question by referring to CNE 'Combined Neutal and Earth' or SNE 'separated Neutral and earth'.

    Avoids saying things like

    'my supply is TNS-C-S-C-s '

    which is actually quite representative of the situation you may have in an older street with a few repairs and new streetlights etc, as at every new joint or new service tap the N and E will be bonded, but the older properties  will still present a TN-S service head.Hence the general advice that if we are not certain to assume PME-like conditions apply, as these are the most onerous.

    We may not be allowed more than one NE bond on a genset, or indeed any on the consumer side of a mains supply, but the networks, who have more control over their cables and routes, and most importantly know better the current rating of their earthing arrangements, are more than happy to have many.

    Mike

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  • 0 in reply to mapj1
    mapj1 said:
    We may not be allowed more than one NE bond on a genset, or indeed any on the consumer side of a mains supply, but the networks, who have more control over their cables and routes, and most importantly know better the current rating of their earthing arrangements, are more than happy to have many.

    Agreed - particularly as consumers receiving their supply at LV are not permitted to combine neutral and earth in the consumer's installation by Regulation 8(4) of the Electricity Safety, Quality and Continuity Regulations.

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