TN-C-S (PNB) versus TN-C-S (PME).

Two different DNO intakes, both are the only connections to a transformer and both have a DNO earth electrode at the intake with the DNO earth electrode conductor cable tied to the DNO supply cable, but one has an internal earth electrode connection and the other has an external connection.

From looking at them, how would you tell the difference between these, if there is a difference?

Also, how would you tell the difference between these and the picture of the TT earth installed by a DNO that I posted a picture of earlier in the discussion?

Sparkingchip said:

TT earth installed by a DNO

As far as I'm aware UK DNOs never supply TT earthing facilities - if it's TT the electrode is part of the consumer's installation, if the DNO supply an earthing terminal then it's connected to their PEN or PE.

An extra G/Y at the intake might just be the final additional electrode of a PME system (seems to be more common on 3-phase supplies or where the service cable is >40m long), or it could be the only electrode on a PNB system (although that usually comes with some very obvious warning notices about not disconnecting it).

    - Andy.

Never say never, just when you think you know something, someone changes it.

Never say never, just when you think you know something, someone changes it.