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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
  • If all the countries listed have PME like arrangements why is it that from what I have experienced only UK regulations and UK EV charge point manufacturers worry about open pen detection., maybe with a few exceptions where companies highly value the UK market. As far as I know it's never included in granny chargers. Is it because the other countries all have a supplementary earth connection to some sort of very good TT earth. 

Reply
  • If all the countries listed have PME like arrangements why is it that from what I have experienced only UK regulations and UK EV charge point manufacturers worry about open pen detection., maybe with a few exceptions where companies highly value the UK market. As far as I know it's never included in granny chargers. Is it because the other countries all have a supplementary earth connection to some sort of very good TT earth. 

Children
  • If all the countries listed have PME like arrangements why is it that from what I have experienced only UK regulations and UK EV charge point manufacturers worry about open pen detection

    Good question.

    The reason we consider PME as potentially problematic in the UK is because of the DTI guidance on ESQCR: see the bottom of page 20, where it states:

    Special consideration should be given to the earthing and protection arrangements for certain installations where reliance on the connection of the consumer’s protective conductor with the distributor’s combined neutral and protective conductor could result in more significant risks.

    Previous legislation and industry practices with PME also highlight the risk. Basically, the Government told us to be careful!

    PEN fault protection is being actively considered in the Republic of Ireland.

    Some other countries, like Germany, have other measures in place, such as foundation earth electrodes, and they don't see it as an issue.

    Australia, I understand, are putting the onus on distributors to monitor for PEN faults with the smart meter system.

    New Zealand believe the risks are low and have advised anyone receiving tingles or minor shocks to report this to the distributor.

    And yet other countries have different views in their legal system (at the moment) and are not taking action.

    So, it's actually a "luck of the draw" that we are in the UK and the UK legislative framework and hazard perception have led to this point. Let's be quite clear ... there are far greater risks of injury from driving the EV than charging it (even from unprotected PME) !

    Is it because the other countries all have a supplementary earth connection to some sort of very good TT earth. 

    No, as above Germany does, but not everywhere else. Whilst BS 7671 now recommends installations with TN earthing arrangements have an additional earth electrode connected to  the MET, it can be easily demonstrated that for it to guarantee to provide protection, the earth electrode resistance that needs to be achieved is very low - single figures in fact ... but would depend on the three-phase unbalance of the distribution network downstream of the break. Worst-case is that all properties downstream of the break are on the same phase, or that phase is the only loaded phase downstream of the break, and you would need earth electrode resistance of less than 1 ohm.

    But there's no saying other countries won't get on board if tragic incidents like the one in Australia happen elsewhere.

  • seconded, as one who travels and tries to use the local supplies I have taken loads of  photos of the electrics in strange places. The risks are the same, perhaps greater, in very many places, the difference is mainly that the locals don't worry about them as they are small beer compared to other dangers, especially in the developing world.

    TN-'x' == don't really care if its earthed or not, really is the only common standard ;-)

    In Russia and much of the former communist bloc that followed their wiring rules, 2 wire supplies even within the building were common and when a 3 pin socket was needed, the 'earth' for it was generated by a short link to neutral behind the sockets -  totally defeating the point of a CPC in my view,  -  though in the former East Germany that was already changing in the mid 2000s, and has probably improved further, though personally I've not been further East recently.

    Mike