Earth provision (TT)

[muzza1]

Was wondering about stuff at work today (out in the sticks upgrading caravan supplies and earthing)

Regarding TT supplies, weather or not the electric supplier should provide the earth (including achieving the lowest value). I think they should.

 

[muzza1]

I think the OP is asking whether the regulations should be changed so that this becomes the responsibility of the supply company?

Thanks for all replies. Yes, leader that's exactly right!
Seeing as the supply company provides the line and neutral, why do they not provide an earth (re TT?)

 

[davesparks]

Thanks for all replies. Yes, leader that's exactly right!
Seeing as the supply company provides the line and neutral, why do they not provide an earth (re TT?)

Because it would defeat the whole point of a TT system if the DNO provided an earth!

 

[muzza1]

Would it? I see what you're saying Dave, but do you not think it would be a good idea if they did?

 

[Richard Burns]

An earth connection relying on the suppliers earthing arrangements and fully under their control (except for the final connection on the customer's property) is a viable choice for a supplier to maintain and support.

To ask a supplier to provide and maintain a system for which the local conditions of the ground, changes on the customers property, malicious or accidental damage on the customers property can all significantly affect the earthing provided would not be a viable choice for the supplier as there are too many items outside of their control that could be easily changed.

A key point of a TT system is that this is used where the supplier does not provide a connection to their neutral point, now a days usually for a good reason.

 

[davesparks]

Would it? I see what you're saying Dave, but do you not think it would be a good idea if they did?

The DNO will not provide an earth connection in any situation where they cannot achieve an acceptable EFLI, or any situation where their earth connection is prohibited from use by a regulation (building sites for example)

If they were to provide an earth electrode for every installation with a TT supply then it would be incredibly expensive for the customer, more expensive than upgrading/converting that distributing main to make an earth connection available.
Following their own earthing rules the DNO would have to install the earth electrodes properly and achieve a stable single figure Ra, which will cost a lot more than having numpty-sparks banging a silly little rod in and would likely result in the customer's garden being filled with inspection pits!

 

[muzza1]

Thanks for your answers chaps. Earthing can be quite a science in it's own right. Does anyone know if other countries adopt a similar practice to ours re TT systems?

 

[davesparks]

Thanks for your answers chaps. Earthing can be quite a science in it's own right. Does anyone know if other countries adopt a similar practice to ours re TT systems?

I believe France adopts TT universally, though may be wrong.

It is indeed a science of its own, and a fascinating one in my opinion. There are some good references freely available online, try searching for the 'east earthing manual' which is an EMEB publication

 

[dnjr]

Hi davespark. Don't suppose you have a link for this as I can't find it. Ta

 

[Richard Burns]

UK power networks have a good library of documentation
this is the east earthing manual (if it will attach)
View attachment East Earthing Manual Feb 2002.pdf

 

[SparkyAndGeorge]

I was always told there is no legal obligation for the supplier to provide an earth connection however during one CU upgrade, I found the Ze far too high for the current earthing arrangement. I rang up the Electricity board to seek advice and they came out and fitted a rod outside.

 

[davesparks]

I was always told there is no legal obligation for the supplier to provide an earth connection however during one CU upgrade, I found the Ze far too high for the current earthing arrangement. I rang up the Electricity board to seek advice and they came out and fitted a rod outside.

They are obliged to make their earth connection available unless they have good reason to withhold it.
They are required to maintain any earth connection they have provided