EV install on a TT system - DNO PME?

Chris Pearson: 
 

Zoomup: 
Clues: Notices affixed to the poles. Earth rods installed at the base of poles, especially at the last one in a run of poles.

If the installation is P.M.E. earthed it will have an official P.M.E. earth terminal installed and a notice informing us of that.

It may not be possible to see all the poles and in any event it is possible that none of them has an earth.

 

 

You can't miss 'em Chris. They are big wooden things that rise vertically up like a high tree trunk with cables on the top. 

Vss P.M.E. head…

Z.

Please note Chris that not all poles have a bear on the top.

Bear Gets Stuck Atop Electricity Pole - YouTube

Z.

J.W. clearly explaining the different types of earthing arrangements.

Types of Earthing System for Electricity Supplies (UK) - YouTube

Z.

gkenyon: 
 

KevinF: 
 

i'm trying this - but it's octopus and they won't speak to me as I'm not their customer!

Whilst Octopus may be the supplier (on the energy bills) …  they are probably not the DNO.

I'd say definitely not the DNO. Octopus are just the retail supplier. Should be straightforward to determine DNO from geographical location. We're with Octopus but DNO is SSE (North Scotland).

OP needs to determine the DNO and determine the earthing arrangement.

The Zappi EV charger does not require earth rod on PEN supplies as it has PEN fault protection. Would be interested to know the make of charger.

ebee: 
Are the DNO not obliged to give this info to anyone reasonably requiring it ? i.e. the Electrician

They are, but “Octopus“ is a meter operator / supplier, not the DNO. Whilst it is possible to have a guess, the DNO are the only ones with this information. What area of the country is this? 

Regards,

Alan. 

But at best the DNO could only tell you what kind of Earth terminal they have supplied, if any. They won't be able to tell you if the previous electrician decided not to use it and TT the installation instead (or forgot to connect an Earthing conductor…)

   - Andy.

True, but they will know if someone has tried to create their own type of PME. 

Regards,

Alan. 

Thanks all - some updates.

There is no obvious labelling to indicate a PME here. I have identified what appears to be the earthing conductor as it disappears into a wall, and doing a Ze at the board with all of the other bonding disconnected from the MET I get a reading of 8.6ohms. This is not too far away from my own properties readings.

It's an Ohme charger so does not contain any PEN fault detection. 

PME or not PME that is definatley the question. It seems there's never a straightforward way to tell. Round here we get 0.238 ohm earth loop  but we definatley don't have PME the main earth is to the lead cable sheath BUT in at least one property at the end of the street has a green/yellow cable that goes from the neutral block to the main DB then onto the water pipe there's no PME label anywhere so what would I put on a certificate if I was writing one out? I know that at least one of the newer link boxes has an extra copper rod beside it. Who'd of thought earthing çould be so complicated!

Round here we get 0.238 ohm earth loop  but we definatley don't have PME the main earth is to the lead cable sheath

Probably not a safe assumption these days. Just because you still have a TN-S style connection at the cut-out doesn't mean it's separate N and PE all the way back to the substation - since most DNOs have had a policy for many years of using a combined N and PE in any new or replacement cables and interconnecting N and PE at any connections with old cables. Any N-PE link after the substation and it's still TN-C-S, with the associated risks of a broken CNE/PEN even if the point of separation to -S is somewhere under a pavement or out on a pole rather than at the cut-out.

We could almost do with an extra box on the certificates/reports for ‘worst of both TN worlds’ - to make it clear that we should be thinking of a Earth that could have the slightly raised Ze values of traditional TN-S together with the (sometimes) larger bonding and broken PEN risks of TN-C-S.

    - Andy.