Sounds odd - unless of course it's a TT installation (or someone at the DNO thinks it is).

557.5.3.1 indent (iii)

I read that as none of the live conductors of the secondary circuit should be deliberately earthed - like a separated circuit  - that doesn't imply to me that section 412 must apply.

   - Andy.

AJ,

TN-S

Indent (iii) of 557.5.3.1 reads;

Doh, should have gone to specsavers - I'd read (i)

(iii) doesn't read as class II construction to me either - as that's usually a matter of the outer enclosure being reliably insulating to prevent electric shocks - class II construction wouldn't necessarily separate one live part from another within the same enclosure (unless I'm miss-interpreting what's being asked for ... wouldn't be the first time)

   - Andy.

Morning Lyle

No usual noways in my part of the world, UKPN land, for panel to have an inbuilt CT chamber. 

The usual method is to bring in a multi-core SWA from the transformer in to the switchroom to supply a separate meter. The cable is provided by the DNO and the meter by the meter operator.

Doing a job at the moment with an 800kVA TX in a GRP enclosure and an adjacent GRP enclosure with the Form 4 panel to supply a large EV charging installation.

The Tx is in, the LV panel is in, 2 x 630mm AWAs connect the panel to the TX, meter cable in and connected to the meter, HV cables installed out to the grass verge adjacent to the roadway. However highway authority not authorising the excavation of the verge as there are already road works nearby replacing traffic lights. Having to wait for traffic light works to finish before the 2 x HV cables to be connected in to the HV ring. 

Might be worth abandoning the existing CT chamber and going for the multi-way meter cable option?

JP

That may well be the reason JP. Come to think of it, a recent replacement had just what you describe done in UKPN land on another site I was involved with. 
Will let you know how matters resolve. 

Lyle

I was on site this morning for a meeting and the meter fixer was there to fit the meter. He had stripped back the SWA cable to connect in to the meter box. I counted the cores in the cable and I can confirm there were 10 cores. Still waiting for the 2 No. bundles of HV cables to be connected in to the HV ring out in the verge beside the roadway. Need a permit from the highway authority but cannot get one until the work changing the traffic lights along the main road is complete! The Highway Authority will not allow 2 nearby street works at the same time. Just another problem to get in the way of completing the project.

JP