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Hi,

Please could you help my friend, who is having electrical work done at his house?

…The ground wires in his house all go to the consumer unit (main fuse box) and there they connect to the Neutral of the incoming mains power supply. In other words his "earth" is the neutral of the mains.

He is now going to Install an electricity kiosk at the edge of his land where the incoming supply and the meter will go. He asked the electrician what to do about grounding, and he said "nothing". Is this correct?

Anyway, Subsequently, his electrician brought another electrician over for advice, who said he actually needs to place two grounding rods into the ground, one next to the kiosk and one next to the property, some 35 m away.

Do you know if this is correct?

Would I be right in saying that the determining factor here is the (albeit rare) situation of “Lost Neutral conductor” in the three phase system somewhere “upstream” of his supply? As is known. “Lost Neutral conductor” is the scourge of mains supply systems the world over, since it can mean Live to Neutral voltages going up to Line-to-Line levels, that is, UK mains Live-to-Neutral in someone’s house could go up to 415VAC.

Presumably, if someone has a local earthing rod near to their house, then these overvoltages would be less likely during situations of “Lost Neutral Conductor”?
 
As the supply is being moved to the edge of the property line the distribution network operator will inform you friend of what type of earth will be supplied.

As the earth is already tied to the neutral, TNC-S, then it is a good bet that this will not change. I cannot see any need for additional earth electrodes unless a car charging point, or similar, is being added.
 
The ground wires in his house all go to the consumer unit (main fuse box) and there they connect to the Neutral of the incoming mains power supply

The neutral and earth should not connect in the consumer unit, only the network operator is allowed to connect them in the service terminal equipment (head) to create a TN-C-S system. I suppose this is what he means?

Would I be right in saying that the determining factor here is the (albeit rare) situation of “Lost Neutral conductor” in the three phase system somewhere “upstream” of his supply?

You are confusing two related but different scenarios that can happen separately or together:
a) A lost/broken neutral conductor in a 3-phase system, causing voltage imbalance and possible L-N overvoltage.
b) A lost/broken PEN conductor (combined neutral and earth) in any system, causing the main earth of a TN-C-S system and everything connected or bonded to it, to rise above local true earth potential.

Hopefully the electrician will have sufficient knowledge of the relative merits of TT and TN systems to determine the best way to earth the new installation.
 

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