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EVs, Street furniture, PME and TT configurations

Former Community Member
Former Community Member
Good afternoon all,


I'm part of one of the teams installing the EV charging points around London and we keep running into the same situations and problems when going through the site selection process - proximity of other electrified street furniture to the units we are installing (as well as potentially plugged in cars which is measured to the edge of the parking bay.)

Regs say that any EV installation cannot be connected to a PME system and must be converted to a TT in case of a damaged/faulty PEN conductor. Naturally if you're converting something to a TT system and not using the DNO TN-C-S earthing arrangement, there must be a reasonable distance between the TT and any other TN-C or TN-C-S systems (2m or so is reasonable).

If there were other services in the vicinity but can be proven that these have also been converted to TT and are 100% confirmed to not be using the DNO earth, would it be reasonable to say that the requirement for the 2m distance can be reduced or ignored completely? Another thought I've had is to bond the cabinets together - being on the same type of system, it makes logical sense that this would in turn reduce the Ze and improve disconnection times, both units have their methods of ADS and incorporate an RCD/RCBO of a 61008 or 61009 standard respectively.


Any other thoughts or ideas would be much appreciated as I try and figure a workaround for this issue. I understand this could work for smaller cabinets and for individual supplies, and not necessarily for street lighting which might not be adequately equipped for being converted to TT (bit of a bigger job to start installing RCDs and then giving a minor works cert etc.).
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    I like your straw man  idea of an equipotential zone outdoors - the idea is of course beautifully ludicrous (rather like including the floor area served by a garden socket in the loading calculation), and highlights the problems in the regs we do not really distinguish that  cycle rack from a cast iron water main, and the both the Ze, and the chances of being bonded to the local PME CPC at an adjacent property are very different, and therefore so is the associated shock risk.  I think any form of words  that really says 'don't bother if its just an isolated metal thing planted in or the ground' is reasonable.

    New water pipes and gas mains are plastic, but round here the ~ 50 year old iron pipes are very much still in service, and to meet the 2020 no cast iron gas main target, we are having yellow plastic liners pushed and inserted inside the old mains, and the old pipe is not actually being dug up, and as they do not even leak yet, I suspect they will remain electrically interconnected between properties and to ground for probably another 20 -50 years before rusting through to the point of being electrical islands  .
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  • 0
    I like your straw man  idea of an equipotential zone outdoors - the idea is of course beautifully ludicrous (rather like including the floor area served by a garden socket in the loading calculation), and highlights the problems in the regs we do not really distinguish that  cycle rack from a cast iron water main, and the both the Ze, and the chances of being bonded to the local PME CPC at an adjacent property are very different, and therefore so is the associated shock risk.  I think any form of words  that really says 'don't bother if its just an isolated metal thing planted in or the ground' is reasonable.

    New water pipes and gas mains are plastic, but round here the ~ 50 year old iron pipes are very much still in service, and to meet the 2020 no cast iron gas main target, we are having yellow plastic liners pushed and inserted inside the old mains, and the old pipe is not actually being dug up, and as they do not even leak yet, I suspect they will remain electrically interconnected between properties and to ground for probably another 20 -50 years before rusting through to the point of being electrical islands  .
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