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13A EV socket

lyledunn
TNCS system in local development. Second hand BMW 330E Hybrid with ICCB that appears to restrict charging to 6A. Owner wants 13A socket on outside wall of house. 

The area is near the Mourne mountains where an Ra of 200 ohms would be difficult to achieve with a single rod. In any event the driveway has just be nicely finished. It would be a simple matter of drilling through the back of the meter cupboard to provide  the 13A socket but it is the loss of neutral protection that is the problem. Anyone know if loss of neutral protection is available as a separate item?
  • 0
    "With a PME LV network you cannot tell fault current to earth from neutral current,"

    This is generally true but surely, at the PEN to earth connection at the substation you can. If there is a PEN break, then the entire load current of the properties beyond the break must return via earth, the exact amount depending on how good the earth is at the property. Some of this will find its way back into the PEN conductor at other properties but much of it will travel through earth until it arrives at the transformer earth.

    It should not be beyond a protection engineer to set the level at above the allowable general leakage and below that which would detect a PEN break.
  • 0
    That is an interesting idea - in effect you are suggesting monitoring electrode current at the substation. I am not sure about this, as part of normal operation will involve quite a bit of electrode current even when there is no fault, as the earth path is in parallel with the neutral, depending a bit on phase balance, and things like how local water pipes are arranged. However I take the point that in fault the electrode current at substation, and at other places as well  will rise relative to the normal case and a  sudden step could be reported as needing investigation, if not an immediate trip. It would require telemetry from substation back to some central HQ, I'm not sure if projects to add telemetry (e.g, https://www.ashwireless.com/pages/35-substation-temperature-monitor)

    could easily be augmented to phone home with additional parameters. You may need to find a way of putting current transformers around the mounting bolts of some large lumps of steel as well, not all transformers are on wooden poles with an easily identifed LV earth wire coming down the side.

    You could extend the idea and telemeter the current flowing into the bonding conductors at preemies with a smart meter..

    I fear there is no appetite for such cunning however, the idea is to keep the existing running as long as possible.
  • 0
    Harry Macdonald:

    "With a PME LV network you cannot tell fault current to earth from neutral current,"

    This is generally true but surely, at the PEN to earth connection at the substation you can. If there is a PEN break, then the entire load current of the properties beyond the break must return via earth, the exact amount depending on how good the earth is at the property. Some of this will find its way back into the PEN conductor at other properties but much of it will travel through earth until it arrives at the transformer earth.

    It should not be beyond a protection engineer to set the level at above the allowable general leakage and below that which would detect a PEN break.


    That would require an electrode downstream of all possible open PEN conditions. 


  • Former Community Member
    0 Former Community Member
    lyledunn:

    TNCS system in local development. Second hand BMW 330E Hybrid with ICCB that appears to restrict charging to 6A. Owner wants 13A socket on outside wall of house. 


     


    Hi Lyle, does the appliance, ie the car come with an instruction book that gives the user any kind of guidance towards what kind of 13A socket the 13A plug supplied is safe to be plugged into? 


  • 0
    lyledunn:
    Harry Macdonald:

    "With a PME LV network you cannot tell fault current to earth from neutral current,"

    This is generally true but surely, at the PEN to earth connection at the substation you can. If there is a PEN break, then the entire load current of the properties beyond the break must return via earth, the exact amount depending on how good the earth is at the property. Some of this will find its way back into the PEN conductor at other properties but much of it will travel through earth until it arrives at the transformer earth.

    It should not be beyond a protection engineer to set the level at above the allowable general leakage and below that which would detect a PEN break.


    That would require an electrode downstream of all possible open PEN conditions. 




    And ignores the effect of extraneous-conductive-parts, which can mask broken PEN conditions by diverting neutral currents via the MET of installations upstream of the break through shared metallic service pipes, or, if extensive and soil resistivity is very low, provide an alternative return path


  • 0
    The more we discuss this, the clearer it becomes that PME is a basically unsafe system and needs to be banned.

    Existing installations should be allowed on the condition that no EV charging points are installed or that the DNO puts in effective protection against PEN faults, e.g. end of line monitoring.
  • 0
    Back to the OP. there are Chinese made relay drivers such as the ZHRV2- series that detect loss of neutral (or more accurately out of spec supply voltage ) you can pair up with your own 3 pole (LNE) contactor if you feel brave.   ( example data sheet of the sort of thing.)

    I have not seen this done for equipment in the UK, but in kit that 'goes abroad' and may be used with what is politely referred to as "power of opportunity", which may be a stack of dodgy cables and adaptors or as crude as someone shinning up a pole holding what look like well insulated jump leads, such arrangements are used to auto-disconnect for the most serious errors of connection or infrastructure damage. Needless to say BS7671 does not really apply to those situations, but unlike the UK, often the  ground is very dry so a shock to terra firma is unlikely to be lethal.
  • 0
    We are waiting for instruction from the company. Meanwhile the lady cracks open the garage door to feed a trailing lead through with the end tied in a plastic bag. Despite me telling her that the risk of loss of neutral is extremely low, I think that she is scared stiff to go near her car while on charge! All things being equal, it would have been better to have installed a simple IP rated socket until her company agreed to pick up the tab for a compliant arrangement. At least that way it would have reduced the risk with the plastic bag and kept the opportunistic burglar from raiding her garage!
  • 0
    yes, in that sense fitting a "lawnmower" socket, that you know would be used for the car, would be a safer option. Extension leads, especially ones that get moved about a lot are more likely to give loss of CPC or indeed any sort of fault, than the network.
  • 0
    lyledunn:

    Meanwhile the lady cracks open the garage door to feed a trailing lead through with the end tied in a plastic bag. Despite me telling her that the risk of loss of neutral is extremely low, I think that she is scared stiff to go near her car while on charge!  




    Mistress of her own destiny?

    If she cleared her garage and parked her car in it whilst it charged what would there be to worry about?


    Andy Betteridge.

     


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