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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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    John Peckham:

    Can we all agree these situations?


    1.  A new build housing estate of a few hundred house on a green field site.  New transformer(s). DNO compelled to provide a TN-S  supply to all properties with earth electrodes laid in the trench connected to every joint earth?

    2. A new cable run out from a sub-station as a replacement or a new supply to be TN-S?

    3. If the DNOs were compelled to upgrade their networks as the water and gas services have been doing for years (why not a requirement as gas and water) the new supplies would be TN-S?




    Afraid not! ?


    1. Yes, I do agree with most of this one. I am not sure about the need for all those earth electrodes. Legislation would, of course, need to be amended. It would also be necessary for the law to require DNOs to maintain TN-S installations as such.


    2. Yes and no. Yes if new, no if old. That's because you couldn't guarantee that all the service cables would have maintained separate N and PE.


    3. No. Unlike with gas supplies, you cannot just shove a new wire up an old one.


    The underlying problem is that whilst it is easy to go from TN-S to TN-C-S, the reverse is not the case, so slowly but surely the LV network has been "PME'd".


    I suspect that part of the problem was deterioration of PILC junction boxes and that TN-C-S was seen as a way of avoiding it. So now most of us are stuck with it.

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    John Peckham:

    Can we all agree these situations?


    1.  A new build housing estate of a few hundred house on a green field site.  New transformer(s). DNO compelled to provide a TN-S  supply to all properties with earth electrodes laid in the trench connected to every joint earth?

    2. A new cable run out from a sub-station as a replacement or a new supply to be TN-S?

    3. If the DNOs were compelled to upgrade their networks as the water and gas services have been doing for years (why not a requirement as gas and water) the new supplies would be TN-S?




    Afraid not! ?


    1. Yes, I do agree with most of this one. I am not sure about the need for all those earth electrodes. Legislation would, of course, need to be amended. It would also be necessary for the law to require DNOs to maintain TN-S installations as such.


    2. Yes and no. Yes if new, no if old. That's because you couldn't guarantee that all the service cables would have maintained separate N and PE.


    3. No. Unlike with gas supplies, you cannot just shove a new wire up an old one.


    The underlying problem is that whilst it is easy to go from TN-S to TN-C-S, the reverse is not the case, so slowly but surely the LV network has been "PME'd".


    I suspect that part of the problem was deterioration of PILC junction boxes and that TN-C-S was seen as a way of avoiding it. So now most of us are stuck with it.

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