Neutral earth links in feeder pillars

Edit - I have multiple locations where I think there are neutral earth links that shouldn't be there, but even though it doesn't "feel" right to me, especially when I see 26 amps going down the earth conductor and only 16 amps going down the neutral in one particular place, I can't find anything certain to confirm it is incorrect.

This arrangement creates a multiply earthed neutral which, assuming you're in the UK, ESQCR 8(4) prohibits in most private cases:

https://www.legislation.gov.uk/uksi/2002/2665/part/II

https://assets.publishing.service.gov.uk/media/5a79ece6e5274a684690d165/GuidElectSafety_Quality.pdf

See also BS7671 543.4.3 to the effect that neutral and PE cannot be recombined.

Are both the neutral and earth cables sized for full potential current? You maybe need just a few to be low in capacity to provide additional reasons for 'fixing' any problems. Just a thought.

Is this part of your on-site distribution, or consumption side ?

I.e are any current consuming loads connected to the TNS part between the links ? 
If not you might be marginally legally OK, even in the UK. Depending how the system was set up, a TNC distro to each building say, but in the building feeding TNS final circuits is permitted - for none consumer circuits only (DNOs do exactly that of course)
Legality aside, it needs some serious thought to get it right, and then does not work well if the earths of different areas are cross linked,  and what you have sounds like it may be if it is diverting current through the earthing and perhaps the building superstructure which is not a good sign.

Don't remove anything yet though - if there are high resistance links masked by the down stream ones it may make it vastly worse. If there are separate neutrals and CPCs in the feeds to the pillars/ cabinets or whatever, then the CPC and neutral continuity should both be verified, as should the presence of upstream link,  before removing the load end link and converting to TN-S, (or TN-s depending on your preference, I tend to follow a former forum contributor's convention of the small 's' load side, and the large one distribution side)

Don't move more than one thing at a time and don't have it energised if/when you do.

Also, related, where is the CPC earthed to terra-firma - where are whatever is acting as the system LV electrodes ?
Mike

Morning, sorry, just trying to decipher the first bit.

Each feeder pillar has TP+N plus CPC supply, so wouldn't be TN-C.  Not sure what is meant by on-site distribution or consumption side though, although it may be asking whether I believe that there is TN-C to each feeder pillar and then that's where the neutral earth link is, which I don't believe it is.

Would definitely be eyeballing and testing each and every part before taking anything out, when it's isolated of course.

With regards to the LV electrodes, we have a combined HV/LV earth electrode as we are not a hot site. 

The neutrals are bigger than the earths, not taking into account the armouring of the supply cable.  These systems have been working without issue for the last 17 years, but that doesn't mean that the earth should be carrying load current in its normal working life.

Thanks - it's certainly not PME as each feeder pillar has its own earth cable, so regulation 9 coming out of 8(4) is not true - plus I don't believe we would meet the definition of a "distributor" or that our buildings are classed as "consumers".  

Well distribution cables only supply boxes doing the  ADS and perhaps metering, that in turn  supply final circuits that may have loads directly connected,. If it has a directly connected load at any point  its not "distro".

I think what you have could perhaps be described as TN-S-C-s, as NE is first both common then separated then connected then separated again, which is not really a recognized combination in the UK unless you are operating your own distribution network ;-)

I'm assuming you are in the UK. In much of Europe, or in AU/NZ this sort of thing would, or at least if done rightl could, be fine.

Mike.

mapj1 said:

I think what you have could perhaps be described as TN-S-C-s, as NE is first both common then separated then connected then separated again, which is not really a recognized combination in the UK unless you are operating your own distribution network ;-)

'reconnection' of N and PE is not permitted by BS 7671, and I don't think it has been at least as far back as prior to 15th Ed of the Wiring Regulations.

if everything on site is under common ownership, then it's a consumer's installation. you've described a private network, so I assume that you're providing a service to somebody. I think that makes them consumers and you a distributor and possibly a supplier

ESQCR prohibits PME only on consumers' installations, not on distribution networks whether public/licensed or private/unlicensed

this doesn't affect the engineering discussion, because you've got MEN not PME