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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?
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    I agree - but the power in question is not the load at the bus stop, which will be hundreds of watts, so a few amps, nor the car, which may be 10-12A on a 13A socket "granny lead", but all the load downstream of the PEN break - which could be anywhere between the substation and the car charge point. I'm visualising  a case when  the lamp post and the house with the electric car are both on the wrong side of the same PEN break.

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    Let's not confuse street installations vs consumer installations.


    The guidance in A722 directs you to consider the demand of the installation if you are using an earth electrode to attempt to limit the touch voltage [at the same time, I'll openly say I think this is rarely practicable, especially for single-phase installations). I do accept it may be more than one installation you have to consider in the big picture, but that's not what BS 7671 is telling us. This may well be down to doing what you reasonably can do in practice (although it's not very practicable).
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    If the advice only covers the case of the broken PEN just outside your own property it is missing a whole slew of more likely fault cases (there being probably one PEN joint that can fail to isolate only one property, and a multitude of joints that can fail in  way that isolates more than one.).

    I agree any attempt to use electrodes to hold the neutral down close to ground potential on both sides of a break in a current carrying circuit is pretty much futile.

    Hence bosky bonds to plumbing and advice to TT to the local surface potential if it really matters.



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    We appear to be back to what if high cpc-pme-neutral currents running in live conductors suddenly need a cpc.

    It may be an idea if we reconsider the use of a separate earthing system using exsisting/new/adapted utility services.

    An example maybe that while companies such as Gigaclear/fix/stuffed continue to rollout fast fibre they might install the earthing alongside.

    Don't worry chaps i'll eventually get my coat.

    Legh
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    mapj1:

    If the advice only covers the case of the broken PEN just outside your own property it is missing a whole slew of more likely fault cases (there being probably one PEN joint that can fail to isolate only one property, and a multitude of joints that can fail in  way that isolates more than one.).

    I agree any attempt to use electrodes to hold the neutral down close to ground potential on both sides of a break in a current carrying circuit is pretty much futile.

    Hence bosky bonds to plumbing and advice to TT to the local surface potential if it really matters.



     


    Agreed on the "only covering PEN outside your property". However, if we're talking about a dwelling, using the full maximum demand perhaps errs on the side of caution by a good way. In addition, in a three-phase installation, the electrode resistance depends not only on the demand downstream of the PEN break, but also on the phase imbalance ...


    With respect to "TT the local surface potential", the local surface potential drops off quite rapidly, perhaps even the difference between one side of a parked vehicle and the other ... forget about it's length ... and you've no idea where buried metalwork connected to PME is located ...


    Shock risk is reduced if you're on certain surfaces (e.g. paved/tarmac) but not dependable (weather, ground saturation conditions, etc.)


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    I can't help thinking that the onus for detecting and making safe an installation following a PEN break should rest on the DNO not on every household that is being supplied. Especially with the advent of EV charging. 

    It should be quite easy to detect a break at the source substation simply by measuring the current in the neutral earth link

    Or am I being too simple here.
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    If you had a TN-S system back to the substation, you could look at the balance of phase and neutral currents and detect faults down stream in an RCD (or earth fault relay) style.

    In this strange parallel universe, you'd want each house to be equipped with an RCD at the incomer to remove any from the network that would lead to tripping of the LV network RCD.


    With a PME LV network you cannot tell fault current to earth from neutral current, so such protection is impossible. Oddly this was first brought home to me in the generator yard at Agrekko near Milton Keynes, when the chap showing us what they had, explained to us all that a special key switch for earth fault detection disable, was fitted to all the gensets they may be called upon to provide to the local DNO, so they could feed in at a faulty substation, in to a network with in effect the biggest NE short going.

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    If it is a PME supply with TNCS installation then you should use a double pole socket. Don't know if you can get an outdoor weather proof one but there are plenty of indoor makes around , looking at ones yesterday in Homebase. Scowling a bit about all these new silver switch bar ones , excellent looking of course for switches four bars in a row  for a multi gang switch. No the centre pivited long bar on sockets only takes the slighted touch to flick it over' a dog / cat small baby could switch on. Around here with PME/TNCS the main earth goes from the cut-out neutral to the metal consumer earth bar which is bolted to the metal casing , the earths now separate from the neutral in the installation, but do they? no still connected to neutral , (and the regs still call the neutral a live conductor). 

    I have seen the result of a aluminum armour  installed around a large factory fence  for security lighting , a cold poured plastic T joint was made at each lighting pole with copper SWA cables to the pole lights, about 6months later what a mess having to break open the joints , copper to aluminum corrision don't  mix.  With old supply  copper overheads between houses now being changed to aluminum ABC's but with the existing copper service drop from the power company's aerial power lines still being used , I predict some trouble in years to come and neutral faults.

    Below is the inners of a double pole switch socket.


    Double Socket, Double Failure, Double Pole - YouTubewww.youtube.com › watch › v=gkNSzAeStws


    regards

    jcm
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    I suppose I will have to clear my garage out if I buy an EV to charge it indoors.
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    Harry Macdonald:

    I can't help thinking that the onus for detecting and making safe an installation following a PEN break should rest on the DNO not on every household that is being supplied. Especially with the advent of EV charging. 

    It should be quite easy to detect a break at the source substation simply by measuring the current in the neutral earth link

    Or am I being too simple here.

    Definitely oversimplification ... diverted neutral currents can happen in any case, especially where there are large amounts of interconnected extraneous-conductive-parts.


    HOWEVER, interesting that, as I understand it, the main distribution companies in Australia are being mandated to put in place voltage monitoring using the Smart Meter system they are installing.


    Should be possible here in the UK ... I'm sure GDPR can be overcome in the way it seems to have beem for the purposes of combatting extraction ...

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