Earthing Arrangements Explained + Photo's

[Hohmage]

So what do YOU think about them??

Hi Engineer54. The first few posts were along the lines of a quiz, so I was trying to get people guessing. Perhaps it's so obvious it isn't worth asking, in which case I'll go now! I'm no electrician, but have been told what the system is by the DNO. It's fairly unusual and outdated as far as I know, and I thought people might be interested (as the thread suggested). I have more pics, I was waiting to see if folk needed more. I was ultimately going to ask this question which I don't know the answer to: how safe is it and what can I do to make it safer!

 

[Silly Sausage]

As no one is playing Hohmage's game, I'll take a punt...

It's PNB.

Away you go fellas!

 

[aesmith]

What's going on there? It looks like two cables leaving the pole, but three arriving at the house.

 

[telectrix]

i'd like to see it with the red insulation tape removed.

 

[Knobhead]

What's going on there? It looks like two cables leaving the pole, but three arriving at the house.

There will an intermediate pole or poles with an earth rod.

 

[Hohmage]

Hi folks. yes, intermediate pole with earthing. Didn't mean to mislead anyone. The red tape isn't masking anything, it was covering the exposed copper at the meter tails. I'm guessing that the greenish wire to right of main fuse is the earth. I am trying to post more pics, but have just upgraded machine to Windows 8 and am lost!

 

[Silly Sausage]

Come on Hohmage, what did the DNO say?
Exact wording please!

 

[Hohmage]

Come on Hohmage, what did the DNO say?
Exact wording please!

Chap said "CEW". Couldn't get much more from him. I've Googled CEW and found one reference to it on this forum, someone asking a question about it but no one answered. Anyone know?

 

[Hohmage]

Is it a posh TT? Earthing cable comes down a big pole?

 

[Silly Sausage]

I've found CEW = Continuous Earthwire. (PME or PNB)

Ask on the IET Wiring Regs Forums, they're bound to know!

 

[Hohmage]

Great, thank you Archy. Did you find much then? It seems that this system is new to some of you - I'd hoped you might find it a bit challenging!

 

[Silly Sausage]

Hahaha....Well I wouldn't have know what it was if it came up and kicked me in the nuts and told me!
I'm still non the wiser.
I'll keep an eye on the IET forums in case you ask over there.

 

[Hohmage]

I found this comment on the IET forum (thanks Archy S): "Up in Scotland as one of the DNOs, CEW or (SEN) is a Continuos earth wire earthing system given to consumers who have an earth loop higher than 0.35 ohms. ie 3 wire single phase system consisting of a phase, neutral and a separate earth. If PME they'd just get a phase and a combined earth/neutral."

This doesn't sound as if it's much better than a TT system, does it? Can anyone say whether I ought to be having my sheds TT'd, based on this comment? I am about to have a RCD-protected split CU installed. 30mA RCDs sufficient? Having seen some shoddy workmanship up here, I want to know exactly what an electrician should be suggesting!

 

[aesmith]

How's the earth actually made, and where does it join neutral (if at all).

I'm comparing with our supply, which is the same type of pole mounted 11kV transformer but in our case we're connected by underground split concentric to provide TN-S (DNO called this CEW as well). As explained by the DNO our transformer's neutral on the LV side is connected to an earth cable/rod/spike or something at the foot of the pole.

A previous house, served by overhead 240V, only had L and N overhead with a locally provided earth.

In this case, are they really providing Earth on an overhead cable?

 

[Silly Sausage]

I found this comment on the IET forum (thanks Archy S): "Up in Scotland as one of the DNOs, CEW or (SEN) is a Continuos earth wire earthing system given to consumers who have an earth loop higher than 0.35 ohms. ie 3 wire single phase system consisting of a phase, neutral and a separate earth. If PME they'd just get a phase and a combined earth/neutral."

That'd be TNS then. (?)
Further research needed, when I'm totally C[SUB]2[/SUB]H[SUB]5[/SUB]OH free!

 

[aesmith]

"Up in Scotland as one of the DNOs, CEW or (SEN) is a Continuos earth wire earthing system given to consumers who have an earth loop higher than 0.35 ohms."

I'm not sure if it's the same thing he was meaning, but SSE publishes a target of max 0.35 ohms for TNCS, but up to 0.80 for TNS. It doesn't necessarily mean that TNS will be over 0.35 though, ours is 0.29.

 

[Hohmage]

How's the earth actually made, and where does it join neutral (if at all).

I'm comparing with our supply, which is the same type of pole mounted 11kV transformer but in our case we're connected by underground split concentric to provide TN-S (DNO called this CEW as well). As explained by the DNO our transformer's neutral on the LV side is connected to an earth cable/rod/spike or something at the foot of the pole.

A previous house, served by overhead 240V, only had L and N overhead with a locally provided earth.

In this case, are they really providing Earth on an overhead cable?

Hi aesmith, thank you for replies. I am only versed in basic electrics. Can you tell me were I should b looking to answer your question "how's earth made, and whre does it join neutral". I have a basic understanding of the more obvious systems TN-S etc. I could take more pics.

I have been told that this overhead earth is still common up here. I had a response on another forum about split concentric: "It looks like an old TN-S to me. Separate overhead earth (no longer done). You could report lack of earthing and see if they will replace your aged supply with a SPLIT concentric drop (TN-S)". I decided to post on this thread because it was specifically targeting earthing systems. I did try to get the chap from SSE to explain more to me, but he seemed unwilling.

 

[Hohmage]

That'd be TNS then. (?)
Further research needed, when I'm totally C[SUB]2[/SUB]H[SUB]5[/SUB]OH free!

I am going to join you on that stuff right now! The electrics in this house are doing my head in!

 

[Hohmage]

"Up in Scotland as one of the DNOs, CEW or (SEN) is a Continuos earth wire earthing system given to consumers who have an earth loop higher than 0.35 ohms."

I'm not sure if it's the same thing he was meaning, but SSE publishes a target of max 0.35 ohms for TNCS, but up to 0.80 for TNS. It doesn't necessarily mean that TNS will be over 0.35 though, ours is 0.29.

This is interesting, thanks. I was hasty in my response about the resistance and the thought of TT, best to be quick whilst kind folk are in the process of helping you out!

 

[aesmith]

Hi aesmith, thank you for replies. I am only versed in basic electrics. Can you tell me were I should b looking to answer your question "how's earth made, and whre does it join neutral". I have a basic understanding of the more obvious systems TN-S etc. I could take more pics.

You may be misunderstanding me, I'm not an electrician but I have taken a keen interest in our earthing arrangements because of the need to take supplies out to some outbuildings with a lot of extraneous metalwork so I made it my business to get a definitive answer.

I see you're supplied by SSE as well, but I guess there are regional differences. I contacted them ([email protected]) to ask what sort of earth they provided. Their first response was that I should get it checked by an electrician, but they also said they were installing PME and could check whether we could be "upgraded". When I asked to follow that up they arranged for their guy to come to site, who clarified the system and also took the Ze reading. I think you have to be a bit persistent, you're probably dealing with someone non technical in the first instance, so you need to give them a reason to pass your question onto the technical team. Are you concerned about the safety of your supply from an earthing point of view?