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

Philip Oakley

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')

 

  • 0 in reply to gkenyon

    Graham, thank you for the clarification. It is always useful to be explicit about definitions.

  • 0 in reply to mapj1
    mapj1 said:
    so long as

    .." tied down to gnd with pole base electrodes"..

    I think it's that step that maybe causing the UK/AUS confusion. Because we (UK) have a variety of arrangements with a wide range of ages and states of repair, we are reasonably happy with a bit of flexibility with definitions, yet at times, pernickety/pedantic about distinctions.

    If the Western Australia Beldon case's diagram is to be taken literally, then they are indicating TT at the point of supply (i.e. use a local Earth rod) and likely only a neutral-earth bond at source (off diagram). So in their case  (The YT commenter) they would see PME as needing a true third cable run through the overhead supply to provide a good earth return. (assuming some level of poor western desert distribution condition)

    No doubt a different view of the local pragmatics!

  • 0 in reply to lyledunn

    plastic bottle supporting the joint.
    locally sourced infill material, surelyThinking... It'll be fine when its filled in and give future archaeologists something to think about
    We have reached " the 21st century plastic layer".
    M.

  • 0 in reply to Philip Oakley

    possibly.
    Given that the australian MEN approach has multiple consumer side NE links it is quite different.

    Consider this diagram lifted from an Australian training document. Look how the 2 out building supplies get a 2 wire feed and an earth rod each - which would on its own be TT in the UK, and acceptable, and then they also get an neutral earth bond, which would actually be illegal in the UK. Only outbuilding 3 would be acceptable both here and there. Equally they would have kittens over 'TT'. I had a long conversation about such matters with a NZ sparky last summer as we were both working on the same scout event, and their approach to earthing is more or less orthogonal to ours.

  • 0 in reply to lyledunn

    Western Power Distribution used to have an environmental impact assessor who would carry out spot checks to ensure that plastic and other waste was not being buried in the holes.

    That hole would have had to be cleaned out before it was backfilled.

  • 0 in reply to Philip Oakley

    I've put in an enquiry to the WA govt (email and contact form) to request a copy of the report and asking that their web interface correct the link errors.

  • 0

    Just updated the numbers

    Going through this discussion one of my takeaways is that no one has quoted any serious injury or death from open pen faults in the UK. There are about 1 million home ev charge points installed in the uk. Assuming that at least 900,000 have open pen detection and open pen detection adds £100 to the price, that means the public have so far spent £90 million protecting against a problem that hasn't caused any serious injuries so far. Is this actually a proportionate reaction to the risk. The biggest benefit or downside of open pen detection is that it's showing how poorly UK supply voltage is managed at the moment, with local supply networks failing to deal with massive changes in demand or moving to surplus.

  • 0 in reply to Alan B

    I suspect that adding an open PEN detector to a wall charger costs a lot less than that.  It will already have a microcontroller, and relays to cut the power to the car.  All they need to add is a way of measuring the L-N, L-E and/or N-E voltages, and a bit of software.

  • 0 in reply to Simon Barker

    But the point is valid - even if was free and all  it did was add 15 mins of labour to the installation and commissioning time, it is a non-negligable cost .and that money will come from not doing something else instead. Which may be something trivial like a safety improvement to the hot water system or skipping a service on the car, or something really important like drinking an extra few pints on Friday that affects the nations mental health.

    Mike 

  • 0 in reply to Alan B

    I have to admit that my initial feeling was that 1M EVCPs was a lot, but there are more EVs.

    In terms of risk, when did your DB last trip? Are all those fuses/MCBs/RCBOs really necessary?

    What price a life? I think that we have discussed this in the past and arrived at the conclusion of £1M.

    Fuses and MCBs also protect against the risk of damage to property, which helps to justify their expense. Do open-PEN devices do that?

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