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

Is the UK the only country that continues to permit and deploy TN-C-S earthing systems?

In a discussion about Diverted Neutral Currents, an contributor (Australia I think) suggested that the problem was that it (DNC) is unique to UK.

I'm not that well versed in international systems of earthing, but it's my understanding that while part of the diverted neutral current problem is because of PME (Protective Multiple Earth), and PEN (Protective Earth and Neutral). And that the the problem is likely to be common to all systems, because there is only one planet earth/ground and we all have to be careful with it when latent and patent faults abound.

I suspect part of the issue is that different folks hear different parts of the story and then project the aspect that's different from their system onto the UK system (given we are reporting it).

Is PME / TN-C-S special to UK?

(discussion was in a Youtube video on ' Loose Neutral Fault Explained')

 

Parents
  • I am confused. Is the discussion about diverted neutral currents or lost neutral?

  • I am confused. Is the discussion about diverted neutral currents or lost neutral?

    Well ... aren't "high resistance neutral" and "lost neutral" quite simply the extreme cases of diverted neutral current (the resistance of the neutral is so high that the alternative path is now preferred by the current, or is the current's only option)?

    Any case of diverted neutral current might cause local rises in earth potential, or rises in potential of conductors connected to the TN-C-S neutral with respect to local Earth.

  • Yes, the original video was about 'lost neutral', however it has a lot of similarity with diverted neutrals, especially in fault conditions and depending on where the potential path to earth was located. This then created the comment that TN-C-S was somehow 'wrong', and my seeking of clarification.

  • This then created the comment that TN-C-S was somehow 'wrong', and my seeking of clarification.

    TN-C-S has its problems.

    But then again, because of protective conductor currents, a broken PE conductor would also be dangerous, potentially lethal, and, unlike broken or high resistance neutrals, you don't get voltage variations.

    TT also has a few potential problems associated with it.

  • however it has a lot of similarity with diverted neutrals

    Definitely one in the same thing really.

  • Well ... aren't "high resistance neutral" and "lost neutral" quite simply the extreme cases of diverted neutral current (the resistance of the neutral is so high that the alternative path is now preferred by the current, or is the current's only option)?

    Surely some diversion is normal where there is at least one service, gas or water, in metal pipes between neighbours.

    Isn't that why main bonding has to be so substantial?

  • Surely some diversion is normal

    Yes. No-one is disputing that. But if it's "normal" is it "diverted"?

    When we are talking about "diverted neutral current" we usually mean it's not flowing where we expect it, usually in greater magnitude than we expect.

Reply Children