Earthing Arrangements Explained + Photo's

[Hohmage]

Hi aesmith, yes, my main concern is with the safety of the earthing. I was originally concerned that the system was TT or similar, and so the CU required a 100mA RCD. At present it has no RCDs at all. As someone else said, the earthing arrangement that I do have here could deteriorate underground. Similarly with the outbuildings, I wondered if earthing rods were required and am still unclear on that one, because some folk say you can never have too much earthing. If he system here is TN-S, then I should worry less. SSE is installing a new substation couple of miles away from here right now, so I will ask again for someone more technical to visit. Thank you for your help.

 

[Knobhead]

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

The three wire is an old way of N→E connection. It moves the LV earth rod away from the MV earth rod.

 

[Hohmage]

The three wire is an old way of N→E connection. It moves the LV earth rod away from the MV earth rod.

Hi Tony, thank you for this. However, being a layman (but really wanting to know more about the subject) I don't understand where the HV would be at the house, let alone the earths. Could you point me in the right direction of a simple explanation please? Many thanks.

 

[Knobhead]

Look for voltage gradients.

 

[GLENNSPARK]

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

for more reading :

http://kisdwebs.katyisd.org/campuses/THS/teacherweb/chemapgt/Teacher Documents/AP reactions.pdf

 

[Hohmage]

Look for voltage gradients.

Thank you Tony. Lots to trawl through on the web, but I found these useful and confusing at the same time:

https://www.ergon.com.au/__data/ass...5/Distribution-System-Earthing-Guidelines.pdf

http://www.ussu.co.uk/ClubsSocietie...g Documens/L2+ Electrical/REF BS7430 2011.pdf

 

[Silly Sausage]

The three wire is an old way of N→E connection. It moves the LV earth rod away from the MV earth rod.

Come on Tony, please explain what CEW is in simple terms, maybe with one of your infamous drawings! (If you're feeling in a generous mood! )
I just can't visualise it.

 

[Silly Sausage]

for more reading :

http://kisdwebs.katyisd.org/campuses/THS/teacherweb/chemapgt/Teacher Documents/AP reactions.pdf

Cheers Cock! I've sussed it.
Cerium Tungsten Electrodes.





That link takes me back to school chemistry, nightmare!
Who let you back in?

 

[Knobhead]

Just because you asked Archy

How it was explained to me at the EMEB collage.

Around each of the earth rods there will under earth fault conditions be a voltage gradient in the ground. In order for the MV and LV to be interconnected the LV earth electrode must be <2Ώ. Higher and the site is referred to by the DNO as hot and no direct MV→LV earth connection is allowed.
Therefore the LV earth has to be moved away from the MV equipment earth. This is to prevent a MV earth fault migrating to the LV system.

My drawing for OH supply

DNO drawing for ground mounted

 

[GLENNSPARK]

Just because you asked Archy

How it was explained to me at the EMEB collage.

Around each of the earth rods there will under earth fault conditions be a voltage gradient in the ground. In order for the MV and LV to be interconnected the LV earth electrode must be <2Ώ. Higher and the site is referred to by the DNO as hot and no direct MV→LV earth connection is allowed.
Therefore the LV earth has to be moved away from the MV equipment earth. This is to prevent a MV earth fault migrating to the LV system.

My drawing for OH supply

DNO drawing for ground mounted

and when you think about it Tony...its just common sense isn`t it...

differing potentials n all that lot...

 

[shanky887614]

Ah so when a lot of people install earth rods they are potentially increasing the chance of nuisance tripping

 

[Knobhead]

Ah so when a lot of people install earth rods they are potentially increasing the chance of nuisance tripping

Only if they link N→E. Which as we all know they shouldn't.

 

[Silly Sausage]

Ta Tony, I'll have to get back later on this one.
I need a clear head!

 

[Knobhead]

This is a thread from many moons back. Imported N→E fault.

http://www.electriciansforums.co.uk...eral-electrical-forum/21227-tingley-taps.html

 

[GLENNSPARK]

and i`ll say this as well Tony..

one of the neighbours up until recently had issues with extranious in his house with voltage sitting on it..

then he said one day the DNO came out and were doing something...
ever since then the extranious in his house has been clear....

hmm.....

 

[Knobhead]

The DNO’s also have another crafty trick with MV OH earthing. You may have seen section switches on OH lines. If you look there will be an earth running from the switch metalwork to the ground. It isn’t a rod, there will be a mat.
The idea is that the ground the operator is standing on is at the same potential as the switch metalwork. Where it gets tricky is approaching the switch, I was taught “the shuffle”. You don’t go striding up to the switch as there could be a ground voltage gradient, you shuffle towards it not putting one foot fully in front of the other.

PS I don’t like MV OH lines.

 

[DPG]

Cows are more sensitive to the gradient effect because of the distance between their legs (this applies to some TV 'celebrities' as well). Luckily most cows don't need to operate MV switchgear - they normally stick the the LV stuff. Daz

 

[Hohmage]

PS I don’t like MV OH lines.[/QUOTE]

Oh boy, this is all filling me with confidence, not! So, as a poor soul who has to live with an overhead supply, is there anything I can do/have done to make it safer? Apart from avoid crawling about on all fours! The DNO is clearly not concerned until some poor sod discovers a fault!

 

[Knobhead]

The advantage of having sheep and cattle in the field is you know there’s a ground voltage gradient around the switch. Dead sheep and cows tend to give it away.

 

[Knobhead]

Oh boy, this is all filling me with confidence, not! So, as a poor soul who has to live with an overhead supply, is there anything I can do/have done to make it safer? Apart from avoid crawling about on all fours! The DNO is clearly not concerned until some poor sod discovers a fault!

If you know there's a fault, supplies gone off etc. Don't go nosing around the MV gear, simple as. If you're that woried, talk to the DNO. If you're on a farm then it's worth a phone call.

Remember I’m talking of fault conditions, not the everyday life of country folk.