earthing

[Big_Spark]

Breezer..he doesn't work on Pylons, that is The National Grid, he works on the rural overhead kit that is at 11Kv or below. The highest he goes is about 20ft!!

 

[breezer]

oh, thanks.

 

[securespark]

When I said PME, I was not referring to TN-C-S (because it is an overhead line) but the principle of PME, the neutral bonded to the earth conductor at the intake.

 

[ban-all-sheds]

Yep, all it is is an adapted TT supply where they ground the Neutral in multiple locations with the lightning conductor earth rods and at the substations. However in your home they install a PME head and split them again for the a standard domestic installation with seperate conductors...that is how it was described to me by a friend who is a 24/7 Overhead Engineer anyway

Sounds just like TN-C-S / PME to me.

If the supply to your house has the neutral and earth combined ("they ground the Neutral in multiple locations") , then there's your TN-C. If at the head they the separate the protective and neutral, there's your -S.

And because of the dangers that would arise from a broken neutral they ground it in multiple places, the fact that the PME rods also act as lightning conductors is incidental to the type of earthing scheme.

Now I know you know all this - I'm not trying to lecture you - I just don't yet see how what you have is in any way different from what I've always seen described as TN-C-S.

When I said PME, I was not referring to TN-C-S (because it is an overhead line) but the principle of PME, the neutral bonded to the earth conductor at the intake.

Securespark - can you run through the definitions of the meaning of the letters T, N, C & S in 1st, 2nd, 3rd and 4th places and show us how an overhead supply cannot be TN-C-S?

 

[securespark]

Ban: Ouch, that f*****g hurt!!

It can.

 

[--tom]

thank you all for your replies.

 

[--tom]

thank you all for your replies.

 

[Big_Spark]

Ban, as far as the IEE and the supply compnaies are concerned these are not TN-C-S..OK, I 100% agree that in priciple it is..so do they?? However they say that as far as they are concerned a true TN-C-S can only be supplied by a concentric cable in which the Neutral and Earth are combines, then split at the consumers intake.

They said that as the Neutral and Phase conductors are actually wholely seperate cables and thus can be replaced independantly, this does not neet the definition of TN-C-S. 24/7 (Energis) said that they understand the confusion, it causes problmes with their engineers, but as the Neutral has been ADAPTED to have multiple Earths, not installed with dedicated earth connections, it cannot be classified as TN-C-S. They suggest it is called a "Hybrid PME"?


Confused..you will be after this episode of

"Electricity, the story of the UK supply Industry!"

 

[IanDB]

Whatever happened to the KISS theory? (Keep it simple, stupid).

 

[ban-all-sheds]

Ban, as far as the IEE and the supply compnaies are concerned these are not TN-C-S..OK, I 100% agree that in priciple it is..so do they?? However they say that as far as they are concerned a true TN-C-S can only be supplied by a concentric cable in which the Neutral and Earth are combines, then split at the consumers intake.

The words "hairs" and "splitting" come to mind - have you, or anybody, ever heard this distinction before? Assuming (??) that the designations are some sort of EN standard (??) what does that say about the exact definitions?

They said that as the Neutral and Phase conductors are actually wholely seperate cables and thus can be replaced independantly, this does not neet the definition of TN-C-S.

I should jolly well hope that Neutral and Phase conductors are wholly separate, otherwise it'll be jolly hard to get any electricity down the jolly wires...

OK - I know, it's a typo (let's hope you're more careful with the real thing )

Assuming (again - bad habit) that you meant that Neutral and Earth were wholly separate, doesn't that make it TN-S?

24/7 (Energis) said that they understand the confusion, it causes problmes with their engineers, but as the Neutral has been ADAPTED to have multiple Earths, not installed with dedicated earth connections, it cannot be classified as TN-C-S. They suggest it is called a "Hybrid PME"?

So if you had the identical design, but installed that way from scratch, what would it be called? I don't see what difference adaptation makes.

Confused..you will be after this episode of

"Electricity, the story of the UK supply Industry!"

It's a confusion of little import. AFAICT I've got TN-S, which makes life a lot simpler...