DNO Earthing arrangements.

[Knobhead]

This is a bit long winded but there’s some interesting reading for both LV and HV earthing systems. It also covers the DNO’s responsibility to the customer for providing earth points. Something a few of you were talking about a short while ago. It does wander about a bit starting with LV then going to HV followed by LV again.

To save people wading through pages of bilge, page 11 covers the DNO’s obligations to the customer.

http://www.eon-uk.com/distribution/...l/E2 Earthing Manual Earth Guidance Notes.pdf

Bits of interest to me was the HV earthing arrangements. It’s finally explained to me how a transformer 11KV delta secondary can be earthed.

 

[Sintra]

Interesting reading thanks. Will stick it for the benifit of others.

 

[pushrod]

Fom P11 (i think)

However, for reasons of safety some installations are not suitablefor a PME earth terminal in which case a TT supply will be offered (see Section E6.3 for a​

detailed list of exceptions).

Be interesting to see the list of exceptions if you have them Tony.

 

[Knobhead]

Try looking in http://www.eon-uk.com/distribution/1210.aspx or http://www.eon-uk.com/distribution/1239.aspx

 

[pushrod]

Try looking in http://www.eon-uk.com/distribution/1210.aspx or http://www.eon-uk.com/distribution/1239.aspx

That's 2 weeks homework ! mind looks like there could be some interesting (in a nerdy electrical way lol) stuff there. Cheers

 

[Knobhead]

That's 2 weeks homework ! mind looks like there could be some interesting (in a nerdy electrical way lol) stuff there. Cheers

I don’t want to know the “official” way of earthing a house, I wanted to know about HV and industrial transformer earthing. I gave the first link as I thought I may help some of you house bashers.

 

[LocalFeif]

thanks

 

[Mr CJ]

Its good to know about in detail. thanks

 

[Knobhead]

Just found this in another thread and thought it could be useful here http://www.legislation.gov.uk/uksi/2002/2665/regulation/24/made

 

[oxocube]

Just like to make people aware that privately owned HV transformers will have far more stringent fault control systems than are required by the dno's.

 

[Knobhead]

Just like to make people aware that privately owned HV transformers will have far more stringent fault control systems than are required by the dno's.

Most have REF (restricted earth fault) fitted normally for internal transformer fault protection.
Overload can be anything, circuit breakers or fuses. The first 1000KVA transformers I fitted had 1600A fuse/switches fitted. No chance of those fuses ever blowing, the 11KV tripped every time. Others had ACB’s, the worse I ever came across was a 1250KVA Tx fitted with a 3000A breaker, again, no chance.
Some are fitted with differential protection (what goes in is compared to what comes out). I only ever came across this on 20MVA and above.
Finally there’s my old favourite the Buchholtz relay, it detects gas or a surge in the oil. I’ve spent several freezing nights in the dark at work due to the oil contracting and the level dropping below the relay level.

DNO local distribution transformers won’t have any of the above, they just feed direct to a distribution pillar. Fuses only from there to the customers.

 

[Knobhead]

DNO Earthing, have fun reading this!

http://www.sppowersystems.co.uk/newconnections/pdf/EART-01-002%20Issue%203%20-%20Low%20Voltage%20Earthing%20Policy%20and%20Appl..pdf

 

[Helm-Electric]

Most have REF (restricted earth fault) fitted normally for internal transformer fault protection.
Overload can be anything, circuit breakers or fuses. The first 1000KVA transformers I fitted had 1600A fuse/switches fitted. No chance of those fuses ever blowing, the 11KV tripped every time. Others had ACB’s, the worse I ever came across was a 1250KVA Tx fitted with a 3000A breaker, again, no chance.
Some are fitted with differential protection (what goes in is compared to what comes out). I only ever came across this on 20MVA and above.
Finally there’s my old favourite the Buchholtz relay, it detects gas or a surge in the oil. I’ve spent several freezing nights in the dark at work due to the oil contracting and the level dropping below the relay level.

DNO local distribution transformers won’t have any of the above, they just feed direct to a distribution pillar. Fuses only from there to the customers.

Not entirely true.... 33/11kV is still classed as distribution, albeit at Primary level and will have bucholz, differential etc. But yes, for HV/LV distribution (Secondary) then no. They are just lumps in the ground that hum away.

 

[Ladders]

Hi Tony. I know this is an old thread but can not see the info? I ask as came across a property, TNS with no DNO earth. Zs readings were all too high on every circuit. So advised customer to contact them etc... Basically the DNO told them to pay for PME and left... Am amazed at their attitute although not suprised!

 

[WPD Lad]

Hi Tony. I know this is an old thread but can not see the info? I ask as came across a property, TNS with no DNO earth. Zs readings were all too high on every circuit. So advised customer to contact them etc... Basically the DNO told them to pay for PME and left... Am amazed at their attitute although not suprised!

Property may not be a TN-S, it might look like one but may well be an old supply that never had an earth supplied by the DNO

Are you able to see any of the lead on the incoming cable and get an ELI reading off it?

If the supply has a proper sweated or approved DNO earth then they're obliged to maintain it.

Got a pic of it? Where are you based?