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THE CAMPAIGN FOR REAL EARTHING

John Peckham
I think that we were considering adopting PME earthing systems today on what we know now we would say no thanks?


I strongly believe that the use of PME earthing systems is inherently unsafe. I am keen to hear any technical arguments to defend the use of PME?


Most PME DNO new distribution cable use 3 core Wavecon cables for UG distribution with single phase concentric cables tapped off for single phase users. For overhead open wire supplies of newer installs ABC cable.


There is no reason not to use 4 core Wavecons and distribute a much safer TN-S earthing system other than the cables will be a 1/3rd more expensive.


 I believe that the DNOs having been tentatively asking government  for a £trillion pounds to upgrade their networks for when we stop burning fossil fuels and go all electric. No doubt the DNOs hope that the government, civil servants and politicians will have forgotten that these private companies purchased a public assets for a knock down price with the idea that the public would no longer have to subsidies a public body! 


A good start would be that no new supplies will be PME, no replacement cables will be PME and no repairs to cables will be PME conversions. For instance a new housing estate would have to be an all TN-S installation. I understand that WPD are already installing TN-S earthing systems for new housing estates. If this is the case then well done WPD. Can anyone confirm this?


I am also concerned about the degradation of the of the Global Earthing System with use of all plastic covered cables, no bonding to metallic service pipes and the failure on DNO contractors to install earth rods and joints to save time and money. Will we start to see 442 type over voltages?


Look at my EV charging thread and the measures we are having to deploy due to PME earthing, we are having to do this because the PME system is inherently unsafe!


Is there support for my proposed campaign?
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    Sparkingchip:

    I believe that’s why MEN with consumer electrodes is used in Australia, isn’t TT is banned in both Australia and New Zealand?


    Do you have a British Geological Survey resistivity map on your wall, I have actually considered getting one and framing it to hang on a wall at as it looks very decorative and rather a talking point. I think I might just get away with it, so long as it was by my desk in a spare bedroom.


    Andy B




     Andy B.





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    To a point, because when it is like that it prevents the use of RCDs.


    Andy B.
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    From that link

    Earth’s mass cancels the effect of leaking current in an installation by earthing out. A correctly earthed system lets one isolate any defective electrical equipment by the means of protective devices.




    and then




    A timber batten acts as ‘touch potentials’ and provides mechanical protection to the pole.




    Seriously, and from  a place that claims to be offering electrical training ~(and called 'success-academy' ) ?


    Elsewhere, at least in NZ, they have considered changing the rules to permit TT on safety grounds, for rural settings where MEN is not as good as it could be,  see report here  but as far as I know it has not got much beyond the discussion phase.



     


  • 0

    mapj1:

    From that link




    Earth’s mass cancels the effect of leaking current in an installation by earthing out. A correctly earthed system lets one isolate any defective electrical equipment by the means of protective devices.




    and then




    A timber batten acts as ‘touch potentials’ and provides mechanical protection to the pole.




    Seriously, and from  a place that claims to be offering electrical training ~(and called 'success-academy' ) ?


    Elsewhere, at least in NZ, they have considered changing the rules to permit TT on safety grounds, for rural settings where MEN is not as good as it could be,  see report here  but as far as I know it has not got much beyond the discussion phase.



     



     




    "The MEN system currently used in New Zealand has limitations, especially in remote rural areas, and the TT system would offer improved safety and performance."


    Yes indeed. I was imagining a very remote house or farm situated on non-conducting dry dust in Australia as well. MEN won't work well if the earth electrodes are living in dry dust.


    Z.

  • 0

    From that link



    Reading between the lines, it sounds like they used to have a fully TT system but had problems getting an effective consumer's earth - in which case even modest leakage currents could raise the touch potentials to something nasty. After that having a a TN system of any kind must seem like an improvement. Presumably none of their LV distribution system had any PE conductors, so TN-S wasn't really an option.

     

    I was imagining a very remote house or farm situated on non-conducting dry dust in Australia as well. MEN won't work well if the earth electrodes are living in dry dust.



    But at least the loop impedance is kept low with a MEN system - even if it might drift a bit above local earth potential. With a fully TT system if the consumer's electrode is just in dry dust you might loose all ADS as well as having leakage currents raise the voltage on the earthing system.


       - Andy.

  • 0

     


     


    I was imagining a very remote house or farm situated on non-conducting dry dust in Australia as well. MEN won't work well if the earth electrodes are living in dry dust.



    But at least the loop impedance is kept low with a MEN system - even if it might drift a bit above local earth potential. With a fully TT system if the consumer's electrode is just in dry dust you might loose all ADS as well as having leakage currents raise the voltage on the earthing system.


       - Andy.

     

     




    Perhaps I'm wrong to visualise a remote dusty sheep station homestead with Kylie Minogue as the  farmer's daughter or wife. With U.K. D.N.O. earth electrodes at least they are underground or situated in a fenced substation enclosure surrounded by gravel chippings.


    Would we have a potential step Voltage shock risk with M.E.N. electrodes with their tops visible in an Australian or New Zealand house lawn? Would Skippy the pet bush kangaroo get zapped in the rain?

    https://www.youtube.com/watch?v=hByob-5pPEs


    Z.

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    Does anybody remember this very sad incident involving a live outdoor water tap?

    https://www.abc.net.au/news/2019-09-27/denishar-woods-garden-tap-electrocution-report-released/11553734


    Z.
  • 0

    Would we have a potential step Voltage shock risk with M.E.N. electrodes with their tops visible in an Australian or New Zealand house lawn?



    I had it mind (but might have imagined it) that thee Aussies insulated the top portion of their rods - specifically to control surface potentials - and often used 2.4m (8') rods as standard. But similar issues with both MEN and TT electrodes in normal circumstances (a few volts difference) and in some 'rare' fault conditions (broken PEN in MEN or earth fault with failed RCD in TT).


       - Andy.
  • 0
    I remember skippy! Takes me back to when I was a little girl fond memory's  thanks for the link
  • Former Community Member
    0 Former Community Member

    AJJewsbury:


    But at least the loop impedance is kept low with a MEN system - even if it might drift a bit above local earth potential. With a fully TT system if the consumer's electrode is just in dry dust you might loose all ADS as well as having leakage currents raise the voltage on the earthing system.


    Of course if the ground really is that dry that you can't get a good connection to it even with a foundation earth or buried tape then it also implies that the risk of shock to earth is low. If you can't manage to earth a great big electrode then a couple of bare feet won't be very well earthed either.

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