TT On-street EV charging installation, Upstream RCD requirements

What protective measure is being deployed within the feeder pillar to provide protection against electric shock?

If it's automatic disconnection of supply, and the earthing arrangement deployed is TT, It's highly likely you will need a suitably rated RCD to supplement the overcurrent protection device at the incoming section. You will also need similar protection upstream to protect against faults that take place inside of the feeder pillar but upstream of the incoming protection device.

I think it's technically feasible for feeder pillars to utilise the protective measure of double or reinforced insulation. Essentially, all of the wiring, switchgear/controlgear, and the enclosure itself is rated at least Class II, meaning an RCD isn't necessarily required at the incoming section.

Thanks for the response,

It's a couple of different scenarios that I'm looking at.

Double or reinforced insulation doesn't look to be excluded as an acceptable protective measure in 'on-street' EV installations in the Code of Practice, so a GRP feeder pillar with an insulated DB  and Class II EV equipment would meet this requirement as I understand it.

But a metal feeder pillar and/or metal DB Class I, would use ADS as the protective measure and in all likelihood would require an upstream, time delayed RCD installed as close as practicable to the service cutout to meet the requirements?

But a metal feeder pillar and/or metal DB

There's not necessarily a direct relationship between metallic enclosures and Class I/ADS (nor insulating enclosures and Class II/double-or-reinforced insulation). There are many double-insulated appliances with metal cases (e.g. cooker hoods) and plastic cased things that require an earth (e.g. some laptop PSUs). The critical bit is the level of insulation around the live conductors - if that meets double/reinforced requirements, then it can go in a metal box without needing it to be Earthed or ADS to work. We commonly use that approach with metal cased domestic CUs used on TT systems where leaving the sheath on the incoming tails right up to the incomer and, where all RCBOs are used, the construction of the bus-bars, provide the equivalent of double/reinforced insulation up to the first RCD. Normally the case is then earthed, to allow ADS to function on the outgoing circuits (as achieving double insulation when terminating multicore cables is a bit more challenging, but the general principle still holds.

   - Andy.

But a metal feeder pillar and/or metal DB

There's not necessarily a direct relationship between metallic enclosures and Class I/ADS (nor insulating enclosures and Class II/double-or-reinforced insulation). There are many double-insulated appliances with metal cases (e.g. cooker hoods) and plastic cased things that require an earth (e.g. some laptop PSUs). The critical bit is the level of insulation around the live conductors - if that meets double/reinforced requirements, then it can go in a metal box without needing it to be Earthed or ADS to work. We commonly use that approach with metal cased domestic CUs used on TT systems where leaving the sheath on the incoming tails right up to the incomer and, where all RCBOs are used, the construction of the bus-bars, provide the equivalent of double/reinforced insulation up to the first RCD. Normally the case is then earthed, to allow ADS to function on the outgoing circuits (as achieving double insulation when terminating multicore cables is a bit more challenging, but the general principle still holds.

   - Andy.