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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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    My understanding is that metal gas and water mains, at least in the street, are being (or have been) replaced by plastic. Once this is completed, the place any remaining pipework (the bit up the driveway of a house, for example) is connected to the PME earthing system is in consumer's premises.



    I wouldn't bank on that. Around these parts at least the water authority's method of "replacing with plastic" seems to consist of breaking the old iron main at junctions and sliding the new plastic tube inside (presumably saves a lot of digging that way). So what we end up with is a continuous plastic main, but surrounded by long lengths of metal pipes with only comparatively short breaks of muddy soil between them. To get the equivalent of 3.5m of soil gap between metalwork you might need half a dozen or more such gaps in series - which might mean many tens if not hundreds of meters of upgraded "plastic" water main.


        - Andy.
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  • 0

    My understanding is that metal gas and water mains, at least in the street, are being (or have been) replaced by plastic. Once this is completed, the place any remaining pipework (the bit up the driveway of a house, for example) is connected to the PME earthing system is in consumer's premises.



    I wouldn't bank on that. Around these parts at least the water authority's method of "replacing with plastic" seems to consist of breaking the old iron main at junctions and sliding the new plastic tube inside (presumably saves a lot of digging that way). So what we end up with is a continuous plastic main, but surrounded by long lengths of metal pipes with only comparatively short breaks of muddy soil between them. To get the equivalent of 3.5m of soil gap between metalwork you might need half a dozen or more such gaps in series - which might mean many tens if not hundreds of meters of upgraded "plastic" water main.


        - Andy.
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