Anyone who's not a 'consumer' (who are prohibited from using CNE conductors in their installation Regulation 8(4) of ESQCR) could theoretically  use CNE conductors.

Does the connection agreement provide a status?

However, going forward, embedded generation and G98/G99 connectivity to the grid (whether at HV or LV) may well change the status of someone who thinks they are a 'generator' or 'distributor'. to a 'consumer' .. that might, again, depend on connection agreements.

Many thanks for the reply - I had overlooked 8(4).

I would have to dig the connection agreement out, but I doubt it would help in determining if the private network operator is a 'consumer' (from the connection agreements I am familiar with).

Looking at the definition of 'consumer' within ESQCR, the network operator is not 'supplied' by a supplier - any electricity they consume comes from the tenant installations (small power and lighting for the substations), so hopely would not be a 'consumer'?

Hello, I think the test for consumer in this context would be the existence of a meter used for settlement and any installation downstream of such a meter would be a consumer installation.  The test for a settlement meter would be whether it has a full MPAN.  This can be established from the relevant DNO or IDNO MPAS enquiry service.

Cop2 Meters on the 33kV incomers to the site, everything downstream is private.

Private meters on all the buildings the 11kV substations feed, as well as any services the LV network feeds.

In that sense metering is the DNO to BNO/LENO IDNO  boundary or whatever sort of 'NO' your side is supposed to be and in that case the LV side NE split  cannot be assumed to be at the metering as there it is on the wrong side of the transformer and HV has no neutral anyway !!

"Consuming" only starts with the bit of the installation that is supplying loads (though thhat may be at HV in some cases) and the agreed demarkation then may be the first breaker after the transformers or switch panel or similar. Problem is that each case is layout dependent.

Mike

edited for clarity

It is metered there - at the IDNO/LENO boundary, via CTs and VTs and COP 2 meters.

on site there is an 11kV and LV network.

I don't think the statutory definition works like that Mike.  It just defines consumer in relation to supply made by a supplier which in the context of electricity regulation means anything after a meter used to measure for settlement purposes (with one or two exclusions for other types of licensee).  I fear this is one of those cases where previous separate regulations have been updated and combined with insufficient technical input following the separation of supply and distribution activities of the old Public Electricity Suppliers.  The lack of a neutral on [part] of such a system doesn't mean that it would be allowable downstream were a neutral to exist there such as the secondary of a DY transformer.  All very obscure if you ask me.  I think it boils down to a blanket ban on private PME of any form.

Except if you think you should  read it like that there would be a  great many installations with multiple transformer that are illegal and some that are switched in a way that  would become very dangerous indeed if you tried to remove the multiple neutral earth bonds and parallel earth and neutral paths in an attempt to make it 'right'. I do not think they are illegal though and  I  am not aware of any test case.

There are also plenty of combined neutral earth submains and 'red top' cut outs that belong to building network operators who have inherited what used to be electricity board risers and and laterals in the common parts of older blocks of flats and so on. They are not DNO, and metering may well occur twice once for the building and then again once per flat.

I agree it is tricky, and like much UK technical legislation, not very satisfactory or clear for corner cases. It is not always an appropriate rule anyway, most countries allow extra NE  bonds and combined NE under some conditions such as private transformers and ;ocal gensets, so long as you keep track of the maximum credible diverted neutral current and size accordingly.

Mike

Except if you think you should  read it like that there would be a  great many installations with multiple transformer that are illegal and some that are switched in a way that  would become very dangerous indeed if you tried to remove the multiple neutral earth bonds and parallel earth and neutral paths in an attempt to make it 'right'. I do not think they are illegal though and  I  am not aware of any test case.

There are also plenty of combined neutral earth submains and 'red top' cut outs that belong to building network operators who have inherited what used to be electricity board risers and and laterals in the common parts of older blocks of flats and so on. They are not DNO, and metering may well occur twice once for the building and then again once per flat.

I agree it is tricky, and like much UK technical legislation, not very satisfactory or clear for corner cases. It is not always an appropriate rule anyway, most countries allow extra NE  bonds and combined NE under some conditions such as private transformers and ;ocal gensets, so long as you keep track of the maximum credible diverted neutral current and size accordingly.

Mike

Thanks Mike, As you say it depends on how you read it.  The words say: " A consumer shall not combine the neutral and protective functions in a single conductor in his consumer’s installation" .  I have always thought this allowed multiple Neutral to Earth connections as long as there was always a continuous Neutral from [local] source to load and appropriate but separate earthing.

statter said:

I have always thought this allowed multiple Neutral to Earth connections as long as there was always a continuous Neutral from [local] source to load and appropriate but separate earthing.

Legislation might appear to permit multiple connections between N and E, but downstream of any point where N and PE are separated, BS 7671 does not.

Having multiple N-E connections can cause circulating currents and is, effectively, an 'N-E fault' (at least to RCDs), and therefore can cause unwanted tripping too. This is really why the 'PNB' earthing arrangement is used.

Nothing to prevent repeated earthing of protective conductors though (except downstream of an Open-PEN protective device, see 722.411.4.1, para and list immediately before NOTE 3).

A consumer shall not combine the neutral and protective functions in a single conductor in his consumer’s installation" .  I have always thought this allowed multiple Neutral to Earth connections as long as there was always a continuous Neutral from [local] source to load and appropriate but separate earthing.

Or another interpretation would be that if you had continuous N and a continuous PE bonded together at two (or more) points, you in effect have two CNE conductors in parallel - and the prohibition applies to each of those conductors.

Typically where there are multiple parallel sources there is only one N-PE link - often the DNO's - and "local" generation is connected as if it were a -ve load (i.e. just between L/N, no N-PE link) - and then if there's a need to run disconnected from the DNO supply (island mode) there's a definite change of mode with a local N-PE link being switched in as the DNO supply is switched out.  (I gather that some  very large installations didn't always do that sort of thing though, although BS 7671's requirements have been pretty definite for a very long time).

   - Andy.