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

My understanding is that the TN-C-S(PNB) earthing arrangement is installed by the DNO to provide a minimum of 8.000 metres separation between the transformer HV earth system and LV earthing system provided for the customer by the DNO.

www.spenergynetworks.co.uk/.../EART-01-002.pdf

Sparkingchip said:

My understanding is that the TN-C-S(PNB) earthing arrangement is installed by the DNO to provide a minimum of 8.000 metres separation between the transformer HV earth system and LV earthing system provided for the customer by the DNO.

Agreed ... but there are two variations

 - one in which the system is earthed at one point only (at or before the first customer, typically of a maximum of 4 customers). This, however, is still NOT TN-S.
 - one in which the system is earthed at or close to each customer's premises (again typically no more than 4 customers). In this case, the N-PE siplt is often at the customer's premises.

Sparkingchip said:

My understanding is that the TN-C-S(PNB) earthing arrangement is installed by the DNO to provide a minimum of 8.000 metres separation between the transformer HV earth system and LV earthing system provided for the customer by the DNO.

Agreed ... but there are two variations

 - one in which the system is earthed at one point only (at or before the first customer, typically of a maximum of 4 customers). This, however, is still NOT TN-S.
 - one in which the system is earthed at or close to each customer's premises (again typically no more than 4 customers). In this case, the N-PE siplt is often at the customer's premises.