TN-S or Not

Question

Hi, 
 Would I be correct in saying the attached is a form of PNB? 
 The transformers are private so for the purpose of EV charging equipment, we treat it as a TN-S?

Thank you in advance.

AJJewsbury · Accepted Answer

Hard to tell from the diagram where the N-PE links are in relation to the Earthing conductors - which would be the clincher.. But presuming this is in the UK and the transformer is part of the "consumer's" installation, then the law (ESQCR) prohibits the use of PEN conductor in consumer's installations, so it shouldn't be PME whatever. 
 - Andy.

gkenyon · Answer

PME conditions only exist in installations that take their supplies at LV from a public distribution system. 
 Mark Fleming said: I ask as we are installing EV chargers which if this was a PME, then an O-Pen device would be needed. 
 Except for a prosumer's installation operating in island mode , that usually takes an LV PME supply from the public distribution network in connected mode , PME conditions CANNOT exist in an installation with supplies at LV taken from only private transformers/generators. It is possible (but not always "legal" - ESQCR) to have TN-C-S in an installation that is not PME. An example could be where the installation is not classed as a "consumer's installation" according to ESQCR. 
 If an installation is "Private PNB", this is not the same as "PNB" for public supplies discussed in G12/4. "PNB" for public supplies must be treated as PME.

TN-S or Not

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