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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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    Be aware that Brazil more than most only has a nodding relationship with its own regulations, in the sense of not actually following them, and the regulations themselves are  a bit incomplete.

    Despite rules to the contrary, much LV wiring is still first fault to danger. Any country that can standardise on the same type of  plug for 2 voltages and then not use it anyway  is a bit different anyway. I found it quite illuminating to see things like twist and tape joints in a shower and the attitude to earthing (as in who needs it).


    More generally, and back to the UK,  I agree LV network fault detection could be a lot better if it was automated.


    The HV side is becoming quite well networked already, with telemetry from new switches and transformers, automatic earth fault relays on overhead supplies,  but some of the LV side in the UK is still state of the ark. 


    On the HV (either 33kV or 11kv phase to phase)  we do not have a neutral or a ground, so any earth leakage is a fault, so the earth can be an electrode and then we keep LV and HV separate if the earthing is not very low resistance, as the HV earth can see quite a rise of potential during an HV to ground fault.

    (Used to be a simple one ohm limit for deciding combined or separate, now it is a risk assessment and a calculation, that still usually means that much above an ohm, HV and LV earth separates, or combined if much below)

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  • 0
    Be aware that Brazil more than most only has a nodding relationship with its own regulations, in the sense of not actually following them, and the regulations themselves are  a bit incomplete.

    Despite rules to the contrary, much LV wiring is still first fault to danger. Any country that can standardise on the same type of  plug for 2 voltages and then not use it anyway  is a bit different anyway. I found it quite illuminating to see things like twist and tape joints in a shower and the attitude to earthing (as in who needs it).


    More generally, and back to the UK,  I agree LV network fault detection could be a lot better if it was automated.


    The HV side is becoming quite well networked already, with telemetry from new switches and transformers, automatic earth fault relays on overhead supplies,  but some of the LV side in the UK is still state of the ark. 


    On the HV (either 33kV or 11kv phase to phase)  we do not have a neutral or a ground, so any earth leakage is a fault, so the earth can be an electrode and then we keep LV and HV separate if the earthing is not very low resistance, as the HV earth can see quite a rise of potential during an HV to ground fault.

    (Used to be a simple one ohm limit for deciding combined or separate, now it is a risk assessment and a calculation, that still usually means that much above an ohm, HV and LV earth separates, or combined if much below)

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