Overhead 240V Supply - How is Earthing Provided?

[aesmith]

Hi,
Posted here as I'm not an electrician, not because it relates to anything I'm considering "Doing Myself".

My late parent's house is supplied by overhead 240V, and I was puzzling over how earthing is provided. As far as I can see following cables it goes ..

• Two overhead cables to the house
• Single cable down to meter cabinet (I assume SWA or concentric)
• Meter cabinet hold main fuse, from which there are L and N meter tails, and an Earth cable

As far as I can see that Earth is the only provision, for example I can't see any sign of an Earth rod.

How is Earth normally provided in these cases?

Thanks, TS

 

[Rockingit]

The Earth is actually the Neutral. Inside the block of the main fuse is a link.

 

[aesmith]

Cheers. Naturally I'm not going look in there, I'll take your word for it. So the earth is actually provided overhead. I did wonder, but then thought that wouldn't be safe, for example if the overhead N failed there'd be no earth. Or maybe far fetched, but if the overhead L came in contact with N.

 

[brianmoooore]

This kind of supply is known as TNC-S Earth (Terra) and neutral (N) combined (C) up to the consumer's supply, and then separate
(S).
You are correct that there is potential danger if the supply neutral fails, and there are regs applicable to TNC-S systems to alleviate that danger.
If overhead live and neutral touch, there's usually a big spark, and a bang somewhere, after which everything is safe because it's not live any more.

 

[James]

It is also worth noting that the overhead N will be connected to earth rods at more than one point so Is less likely to fail and become Live.

 

[brianmoooore]

It is also worth noting that the overhead N will be connected to earth rods at more than one point

Hence the former name for TNC-S, PME. Protective Multiple Earth.