Exported PME to steel floodlight columns, public tennis courts

When looking for justification for adding earth electrodes should this document be considered?

2.5.3 Lighting authority/asset owner private cable distribution system
A lighting authority/asset owner may design and install their own cable networks but these usually consist of a separate neutral and earth (TN-S), which is connected to a PME point of supply.
An earth electrode should be installed and connected to the earth terminal at the point of supply. It is good practice to install and connect an earth electrode at the last or penultimate lighting column on the circuit where there are three or more columns on that circuit.

www.theiet.org/.../guide-to-highway-electrical-street-furniture.pdf

When looking for justification for adding earth electrodes should this document be considered?

2.5.3 Lighting authority/asset owner private cable distribution system
A lighting authority/asset owner may design and install their own cable networks but these usually consist of a separate neutral and earth (TN-S), which is connected to a PME point of supply.
An earth electrode should be installed and connected to the earth terminal at the point of supply. It is good practice to install and connect an earth electrode at the last or penultimate lighting column on the circuit where there are three or more columns on that circuit.

www.theiet.org/.../guide-to-highway-electrical-street-furniture.pdf

It is not quite fair to say that the regs do not allow us to consider the possibility of an NE offset voltage and to do so is in someway wrong. It is only true that we are not obliged to consider it, but that is not the same at all - there may be local conditions that push toward TT islanding.

And as an aside if you are building a milking parlour or an outdoor swimming pool then in many ways the advice in the regs does oblige us to consider touch voltages and the conclusion to that deliberation is that farms in general that are not private transformer and pure TNS, are instead TT, but almost never TNC-s.

So if the lamp post was in the middle of a the yard of a dairy farm, even if the supply is a sub-main from a PME supplied  living area you may well decide it should be TT.

If however it is more like the city street light and in the middle of a tarmac pavement  of nebulous contact with the terra-firma below, then it may as well be PME and the faster fuses only ADS time is an advantage.

The question is not stupid, and the regs are not the last word in thinking.

We do not all live in urban town and city centres, and one rule does not fit all. (and in my local south English market town we have rows of houses that are all TT as well, fed from bare overhead singles - you'd certainly not want to PME from that - a tree branch bringing down the lower wire only is a very credible fault indeed.)

Mike