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Probably a stupid question...

tonydon

Right...

We are on a site with 2 onsite substations providing our supplys.

Upon inspection the supply comes from the substation transformer room, into our switch room, as a TP&N feed to our section boards.

We cant see any earth other than the armour of the supply cable which is obviously attached to the section board.

A colleague and I have been debating whether this is a TNS or TNCS supply.???

Given that the transformer is just the other side of the wall in our switch room, and that the earth and neutral must be bonded at the star point of the transformer secondary.

Are we right in thinking the supply is TNS??? 

Parents
  • 0

    Sometimes the N-PE link is in the first switchboard rather than on the transformer itself - but I agree it's normally TN-S (not least because if you receive the supply at HV and have private transformers, all LV side including the transformer secondaries will be part of the 'consumer's installation' as so prohibited from having a combined earth and N conductor by the ESQCR).

       - Andy.

Reply
  • 0

    Sometimes the N-PE link is in the first switchboard rather than on the transformer itself - but I agree it's normally TN-S (not least because if you receive the supply at HV and have private transformers, all LV side including the transformer secondaries will be part of the 'consumer's installation' as so prohibited from having a combined earth and N conductor by the ESQCR).

       - Andy.

Children
  • 0 in reply to AJJewsbury

    "if you receive the supply at HV and have private transformers, all LV side including the transformer secondaries will be part of the 'consumer's installation' as so prohibited from having a combined earth and N conductor by the ESQCR)."

    Interesting answer.  we have 2 subs the first was put in in 1954 with the original "college building" as it was then.

    The second was installed about 15 years ago.  If I remember correctly we had to pay for the full installation.... so private??

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