Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 68 replies
  • Subscribers 32 subscribers
  • Views 9372 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

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?
Parents
  • 0

    Like all these things, we seem to want a Rolls Royce system, but society doesn't want to pay



    I wouldn't call TN-S with an equal sized PE a Rolls Royce solution - if you wanted a properly safe Earthing system you'd go for a PE that had about 5x the conductivity of the line conductors - so that the Voltage on the supplier's earth couldn't exceed 50V - keeping things safe even during long disconnection times (whether 5s BS 7671 ones or quite a bit longer for faults on the distribution network). That would also allow us to solve the 'mixed disconnection times' problem within installations (circuits with long disconnection times have larger c.p.c.s) and have a supplier's earthing terminal that was useful for just about every application.


    As has been said, the larger cost is digging, planning and carrying - a bit of extra copper wouldn't add a huge percentage to the overall cost.


    Alternatively a smaller PE together with a neutral earthing resistor so that during faults the PE remains at close to true earth potential (N is pulled high instead).


    Disconnection of Earth faults at the substation might be problematic if faults on consumer's installations could (false) trigger it. We'd need RCDs at each consumer's intake - but that's exactly what the French do - so not beyond the bounds of possibility.


    While we're about it we might think about going 3-phase for domestic supplies - so we could manage with smaller live conductors and benefit from reduced v.d. 


    And get smart meters to monitor supply voltages and disconnect is they go significantly out of spec to protect consumer's installations from overvoltages (e.g. broken N). They could monitor for loss of Earth while they were at it too - and automatically report back to the DNO (far more efficient than waiting for consumers to notice something dim, tingly or smokey and phone it it manually).


    There's so much we could do far better if we weren't starting from here. I do agree though that there feels to be something fundamentally unsound about the PME approach and alternatives should be considered - even if (like the introduction of 13A plugs) it takes a long time before everyone benefits.


        - Andy.
Reply
  • 0

    Like all these things, we seem to want a Rolls Royce system, but society doesn't want to pay



    I wouldn't call TN-S with an equal sized PE a Rolls Royce solution - if you wanted a properly safe Earthing system you'd go for a PE that had about 5x the conductivity of the line conductors - so that the Voltage on the supplier's earth couldn't exceed 50V - keeping things safe even during long disconnection times (whether 5s BS 7671 ones or quite a bit longer for faults on the distribution network). That would also allow us to solve the 'mixed disconnection times' problem within installations (circuits with long disconnection times have larger c.p.c.s) and have a supplier's earthing terminal that was useful for just about every application.


    As has been said, the larger cost is digging, planning and carrying - a bit of extra copper wouldn't add a huge percentage to the overall cost.


    Alternatively a smaller PE together with a neutral earthing resistor so that during faults the PE remains at close to true earth potential (N is pulled high instead).


    Disconnection of Earth faults at the substation might be problematic if faults on consumer's installations could (false) trigger it. We'd need RCDs at each consumer's intake - but that's exactly what the French do - so not beyond the bounds of possibility.


    While we're about it we might think about going 3-phase for domestic supplies - so we could manage with smaller live conductors and benefit from reduced v.d. 


    And get smart meters to monitor supply voltages and disconnect is they go significantly out of spec to protect consumer's installations from overvoltages (e.g. broken N). They could monitor for loss of Earth while they were at it too - and automatically report back to the DNO (far more efficient than waiting for consumers to notice something dim, tingly or smokey and phone it it manually).


    There's so much we could do far better if we weren't starting from here. I do agree though that there feels to be something fundamentally unsound about the PME approach and alternatives should be considered - even if (like the introduction of 13A plugs) it takes a long time before everyone benefits.


        - Andy.
Children
No Data

Community Rules & Guidelines