MY personal view is to install an "Isolation Transformer" the price is worth the Life !!

I think I can see a rational for retaining PME inside, say, a garage. It is likely that there will be lights, sockets, and maybe a garage door mechanism fed from the main distribution board in the house. Therefore their associated metalwork and that of anything connected to them will be at the same potential (save for under a fault condition) as the potential at the incomer's earth. It would be essential that the body of a vehicle on charge is at the same potential, to avoid the risk of shock potential being developed between the car body, and say a metal clad light switch or socket. However, as already pointed out, in the event of a neutral/Earth disconnect fault in the network, there is a risk of shock potentials arising between anything in the garage and "True Earth" which maybe the floor. It strikes me that if the risk of electrocution from touching a connected EV under such conditions is significant, then so to is that from touching any part of the garage's electrical installation. Clearly this cannot be the case, or all garages would have had to be made TT long ago. I think the answer to why PME is allowed indoors but not out is simply that outside regularly gets wet. Inside far less so and there is PME connected metal work around. Consequently the impedance to True Earth is likely to be very much lower outside than in. So outside, a  very rare event with very high impact; high risk of electrocution. Inside, same very rare event, but vastly lower risk of the consequences being catastrophic.

What about all of the P.M.E'd lamp columns and street furniture in the street? As Mike says, we do not see piles of dead bodies at bus shelters or piles of dead dogs at the base of street lamps.

Z.

G12/4 Issue 1 had the answer right there for the reading ... it's related to the connected load downstream of a broken PEN conductor, larger the load, the greater the risk, as the less capable an earth electrode of given resistance is of limiting the rise in touch voltage.

EVs are a large load.

Chrispy said:

So outside, a  very rare event with very high impact; high risk of electrocution. Inside, same very rare event, but vastly lower risk of the consequences being catastrophic.

Sort of ...  the HSL report that was commissioned back in 2011 doesn't really say "high risk of electrocution", but puts the ball-park in the range of"broadly tolerable" which translates to "if you can do something to reduce the consequences or the likelihood, you should do so".

Since no one has answered but you may already have the answer. Reading the code of practice 4th Edition -  paragraph 6.7. Using the PME refers to mode 3 - Tethered charging cable with pilot function and a diagram on Page 10.

Wouldn't the supply be lost as well as the means of earthing?

Jaymack 

Wouldn't the supply be lost as well as the means of earthing?

Yes, in the case of a broken PEN, the supply would be lost - or at least usually significantly reduced (depending on what remained connected to Earth upstream of the break) - but the broken PEN conductor & installation earthing system would still be pulled towards line voltage by other connected loads in the installation, and while the various pilot functions (often including the vehicle's check of the earth loop) might prevent the charge point's L&N contacts closing, the PE connection (other than in specifically open-pen detecting charge points) would usually remain solidly connected.

   - Andy.

AJJewsbury said:

Wouldn't the supply be lost as well as the means of earthing?

Yes, in the case of a broken PEN, the supply would be lost - or at least usually significantly reduced (depending on what remained connected to Earth upstream of the break) - but the broken PEN conductor & installation earthing system would still be pulled towards line voltage by other connected loads in the installation,

I think the truth of the matter is significantly more complex.

The answer is "Not necessarily" ... there are a few situations that would keep the "lights on full" as it were, chiefly because most PME distribution systems are three-phase:

(a) the balance on the network may well mean Neutral current is very low (or zero), in which case the touch potential to the general mass of Earth will be kept down. However, the balance can also be such that, on one or more phases, the voltage can still be significant enough to operate equipment, in fact within "normal" limits, with a hazardous touch potential on the supply neutral (and hence PE of the installation) with respect to the general mass of Earth - only one phase may see a "low voltage".

(b) There could be a sufficiently-low resistance of fortuitous connection back to the supply Neutral, through extraneous-conductive-parts, so that everything seems "normal" - and this again wouldn't necessarily lead to a high touch potential, that is until suddenly something changes.

(c) Even if the installation is upstream of a break, there are occasions when diverted neutral currents could occasionally cause a local rise of PE potential with respect to the general mass of Earth.

I think the truth of the matter is significantly more complex.

Absolutely ... I was aiming my answer to where I guessed the chain of thought was heading - i.e.  that if the EVSE has no power then the contactors inside the charge point wouldn't pull in and so the vehicle wouldn't be connected...

    - Andy.