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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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    I'd support some sort of TNS or SNE (separated neutral and earth)approach to distribution as being slightly safer.

    It also has the advantage of allowing an earth fault transformer (like the RCD sensing part) at the substation, allowing the substation to call in (or even disconnect for) earth faults, and the lost PEN giving rise to a live chassis becomes impossible.

    However, it does not eliminate the more general 3 phase loss of neutral problem, and may make the extremes of fault voltage seen by single phase equipment worse, but of course side effects are contained to equipment damage, not loss of life.


    There is not much real evidence that PME is very dangerous, at least when well maintained. After all while A and E is full on  Saturday nights, it is not the victims of the electrical network that clutter the cheap plastic chairs... 


    So for new work and repairs, SNE may be preferred, but it is not possible on safety grounds to justify taking out existing PME.


    A better approach may be to regulate the  inspection and reporting of PME installations so that dangerous situations are spotted sooner, before something fails and the first warning is is customers calling in with flashing lights and tingles off the taps (I'd support a campaign of testing ZS and labeling cut outs with the result whenever a DNO visits on any system)
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  • 0
    I'd support some sort of TNS or SNE (separated neutral and earth)approach to distribution as being slightly safer.

    It also has the advantage of allowing an earth fault transformer (like the RCD sensing part) at the substation, allowing the substation to call in (or even disconnect for) earth faults, and the lost PEN giving rise to a live chassis becomes impossible.

    However, it does not eliminate the more general 3 phase loss of neutral problem, and may make the extremes of fault voltage seen by single phase equipment worse, but of course side effects are contained to equipment damage, not loss of life.


    There is not much real evidence that PME is very dangerous, at least when well maintained. After all while A and E is full on  Saturday nights, it is not the victims of the electrical network that clutter the cheap plastic chairs... 


    So for new work and repairs, SNE may be preferred, but it is not possible on safety grounds to justify taking out existing PME.


    A better approach may be to regulate the  inspection and reporting of PME installations so that dangerous situations are spotted sooner, before something fails and the first warning is is customers calling in with flashing lights and tingles off the taps (I'd support a campaign of testing ZS and labeling cut outs with the result whenever a DNO visits on any system)
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