EV Charger TT arrangements for private drive close to highway apparatus

The situation is not "omitted" from the 4th Edition of the EV CoP ... it is covered. The situation is discussed in the 4th Ed CoP - see section 5.1.2, item (a). BS 7671, Regulation 411.3.1.1, requires simultaneously-accessible exposed-conductive-parts to be connected to the same earthing system. The risk assessment for simultaneous contact (Annex B for Dwellings) was introduced in earlier Editions of the EV CoP to help identify this safety issue, and on page 50 there is a discussion in item (b) of Section 6.8 on the simultaneous contact issue. The first of the Notes on Page 50 (mi highlight) says:

When assessing the risks of simultaneous contact between conductive-parts
in contact with different earthing systems within items (a), (b) and (c)
above, this assessment must include all accessible conductive-parts including,
for example, any conductive-parts associated with adjoining or nearby
properties, and any other outdoor-installed electrical equipment, etc.

Because in this case, the lamp post is part of another installation that is outside the control of the owner of the installation to which the EV charging equipment is to be connected, of course as you point out it's not possible to use TT in this instance, unless some barrier, fence, or other means could be installed on the consumer's side of the boundary to prevent simultaneous contact with both the vehicle body and the lamp post, see 6.8(b)(ii).

Where an installation has a PME supply (see Section 5.3 of the 4th Ed CoP), the use of a separate TT earthing arrangement for the charging equipment (section 5.3.3) is only one option. There are other design choices to explore, such as provision of electrical separation (section 5.3.4) or use of equipment that detects open-circuit PEN conductor faults (section 5.3.5).

Is the house on the same PME supply as the house?  If so, then what's the problem (other than awkward installers)?

Yes, this is the perfect install for the type of EV charger that has Open Pen Detection. 

I think that all Manufacturers will be going down this route within the next year (certainly for domestic customers), and doing away with the TT install for the charger.

Graham, thanks for the detailled response.... I must admit I had glossed over that!....  We can assist by converting the street light to a TT system of earthing but obviously the client would have to pay for such modifications. Usually whenever we install EV Chargers on the highway we convert anything within 2.5m of the parking bay to TT which includes any electrical apparatus located on the highway as per the CoP.

No the House and service to the street ligh are on different phases of the network.

We have an issue as the local DNO, who do not currently recognise anything but the TT method of earthing arrangement for these installations. WPD seem to be the most pre-active across the other regions, embracing new Open Pen Conductor technologies.

But that doesn't mean that they are on different earthing systems.

But if the charging point is TT, then the charging point and vehicle will be on a different earthing system to the street lamp.

Converting the street lamp to TT won't solve the problem, unless you bond the TT system of the street lamp to the TT system for the EV charger (Regulation 411.3.1.1) ... and because the installations are not owned and operated by the same organisation, it's not generally considered suitable to simply bond them. I agree the solution is fine for on-street, where it's all just "street furniture", but this is a private dwelling installation which has different considerations.

What this may well mean, if your local DNO won't accept open-PEN detection, is electrical separation (or no EV charging point). Having said that, if a consumer installation (as opposed to on-street) complies with BS 7671, does the DNO have any recourse?

I understood that Larryinplymouth had said that both the house and street lamp were PME.