Earthing arrangement

Sounds like it is all wired in straight concentric, not SWA. That's not considered OK for direct burial under BS7671 so totally independent of the earthing I can see why the electrician wants to condemn it. The problem is that if someone puts a spade or anything else through the cable it hits the concentric neutral, not earth, and neutral is considered to be a live conductor.

How is the supply metered? Or put another way, where are the meters?

If this was a DNO or independent distribution network it would be OK, as they are allowed  TN-C but it is not OK in consumer side wiring, as it is not TNC-s.

Unless the cable is in ducting, then the option to make all the sheds TT is not really there.  BS7671 does not recognise a 'neutralled' armour as a means of protection.

This previous thread may be of interest for reference - it has parallels and turned into a bit of a saga, though an informative one.

mike

If it's straight concentric, then the outer should really be a PEN rather than just N. If it is then it might not be quite so bad - a PEN qualifies as an earthed Protective Conductor and isn't (by convention) classified as a live conductor so is suitable for direct burial. BS 7671 doesn't have any blanket ban on PEN conductors - although does impose a few conditions (see 543.4). Since the demise of the old Supply Regs I'm not aware of any requirement to obtain authorization from anyone (in the UK at least) and while the current Electricity Safety Quality and Continuity Regulations prohibit the use of PENs in consumer's installations, that prohibition would not seem to apply installations operated by some third party who isn't a consumer - e.g. a BNO or perhaps landowner providing a separate supply to tenants.

It sounds like the system might be deficient on a few details - e.g. the 6mm² branches probably wouldn't meet the BS 7671 requirement for PEN conductors to be min 10mm² Copper (or 16mm² aluminium)  - but that might be more a matter of a technical non-compliance than posing an immediate danger (depending on the circumstances).

Of course there are lots of details that might trip things up - e.g. if the “PEN” is fed through some means of switching or isolation (or even worse a fuse) rather than being solidly connected all the way back to the supply, but the situation might not be quite as bad as it has been painted.

   - Andy.

However, the ‘network operator’ even if it is the site or building owner, will need to work to the same standards as the DNOs in terms of preventing the accidental interruption of that PEN conductor.  Double crimps or double screw terminals encapsulated etc. 

And the actual DNO may well refuse to connect to  it - or would do of they knew about it - I suspect they do  not ?.

And ‘consumer installation’ usually starts at the first electricity meter. Where is that ?

Mike.

How are the sheds metered? As in are they paying the landlord or supply companies.

Are these “sheds” used as living accommodation with people cooking and sleeping in them? 

What toilet and washing facilities are there onsite?

It sounds like you are describing a Gypsy and Traveller Caravan site, if you are I presume there’s an electric supply run into each of the caravans from the adjacent shed that contains the kitchen and bathroom?

But as a sites point of view do they have to supply a earth through the swa or can it be upto the owners of the sheds to install a earth rod. 

The presence of central metering means this is ‘consumer side’ wiring so no PENs please, ESCQR and all that.

The site could supply each shed with a bare live and neutral and no earth, on the clear understanding that the end users organised their own earths and RCDs. 

However, this would either have to be done in overhead singles so the route is visible, or in a buried cable with an earthed armour, or buried under or inside a suitably strong  cover or  enclosure  providing sufficient  mechanical protection to prevent accidental damage, as the cable is not armoured

This cable is NOT an SWA. For very good magnetic reasons, single core steel armoured cable is simply not made. It will be a plain concentric cable with either a copper or aluminium outer armour layer, and intended for pre-meter distribution. 

Such an installation is not compliant with current regulations, and as that part of the rules has not changed for more than half a century, I also imagine it was not compliant when it was installed either.

Mike.