The IET is carrying out some important updates between 17-30 April and all of our websites will be view only. For more information, read this Announcement

Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 58 replies
  • Subscribers 31 subscribers
  • Views 9244 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

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..
Parents
  • 0

    Thus what Andy has drawn would be TN-C-S if the exposed parts in the installation are connected to a separate protective conductor. Any PNB system would also be described as TN-C-S in Ireland.



    I'm not sure that's right. TN-S vs TN-C-S and PNB vs PME are almost two different things. TN-S vs TN-C-S is about whether there's a shared neutral and earth conductor at some point in the system; PNB/PME is down to how many distinct connections to earth the N has (one vs two more).


    PNB could be either TN-S or TN-C-S depending on whether the N-PE link is upstream or downstream of the earthing of the N.

    b5d6b6dc8e4ab52c65f06dee2399d6f3-huge-tn-c-s-paths_zpshylchzz3.png


    The above would be the TN-C-S version of PNB, but add an extra electrode between A and B and it becomes PME. But the earlier diagram would be TN-S in Ireland as well I think - there being no CNE.


      - Andy.
Reply
  • 0

    Thus what Andy has drawn would be TN-C-S if the exposed parts in the installation are connected to a separate protective conductor. Any PNB system would also be described as TN-C-S in Ireland.



    I'm not sure that's right. TN-S vs TN-C-S and PNB vs PME are almost two different things. TN-S vs TN-C-S is about whether there's a shared neutral and earth conductor at some point in the system; PNB/PME is down to how many distinct connections to earth the N has (one vs two more).


    PNB could be either TN-S or TN-C-S depending on whether the N-PE link is upstream or downstream of the earthing of the N.

    b5d6b6dc8e4ab52c65f06dee2399d6f3-huge-tn-c-s-paths_zpshylchzz3.png


    The above would be the TN-C-S version of PNB, but add an extra electrode between A and B and it becomes PME. But the earlier diagram would be TN-S in Ireland as well I think - there being no CNE.


      - Andy.
Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines