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

The new definition of PNB in part 2 seems to have suffered from a bit of cut & pate itus I think... for me the critical difference between PNB and PME is PNB has its N earthed at a single point (i.e. there's nothing multiple about it) - "a single source of voltage" has nothing to do with it (you can still have PV or other local generation with PNB).

   - Andy.

ah split phase - how to win friends and confuse people ;-)  at least the cancellation of third harmonics will be better. It is the sort of thing that's only really obvious with a meter to reveal the phasing and a look outside for the transformer arrangement. Perhaps if there is an HV line pair instead of a triple outside one does not need the meter.
Mike.

At what point does TN-S become "TN-C-S (PNB)"?

In my mind it's quite simple - where the path of the N current shares a conductor with the path between exposed-conductive-parts and the means of earthing.

I think a mistake has been made in describing the N tail from the transformer as a PEN conductor. Earthing is the concept of connecting an exposed-conductive-part to a means of Earthing. In the new Fig 3.9B the N conductor to the left of the N-PE link serves no earthing purpose - it's not connected to any exposed-conductive-parts - just the star point (transformers are earthed to the HV earthing system). Calling it a PEN causes confusion and rapidly reduces the whole situation to absurdity.

As I understand DNO documentation, there are two versions of PNB - the common one is TN-S in our terms, another (typically used where there's >1 customer) does have a PEN conductor and does carry some of the dangers of PME, despite having N earthed at a single point on the DNO side.

   - Andy.