Just a second.

As I understand and correct me if I am wrong, the problem with the EVC is where exactly (potential wise) your feet stand when using the EVC.

If they are standing on PME potential or if they are standing on true earth potential.

And this is the criteria about having a TT system for the EVC or not.

I get it correctly, don't I?

P.S. Thanks for your answers guys. Really appreciate

Concerning footwear: leather soles, especially on a wet day are hardly insulators.

Keys?


Very retro.

If a driver drops their car keys onto the concrete floor and reaches to retrieve them, they may be in contact with the metal keys on the floor with one hand, and the car as they steady themselves with the other bare hand.

But concrete (being non-metallic) has a relatively high resistance - hence you need contact with a reasonably large surface area to get a low enough resistance to allow enough current to flow to get a hazardous shock - a bare foot with perhaps several tens cm² of contact with the concrete would be far more dangerous than a bunch of keys with perhaps only a couple of mm² contact.


In some ways I agree with OMS's assessment that the PME situation probably isn't as dire as trying to apply normal BS 7671 rules on simultaneous contact might suggest - we've had earthy metalwork (e.g. barrier fencing) within reach of PME'd steel lampposts, all outdoors, with no bonding, for decades (as per reg 714.411.3.1.2) with little apparent problem.


  - Andy.

But who says that the concrete floor is dry Andy. The car park floor may be covered in salty water in the winter as the slush melts from cars' wheel arches and chassis onto it.


Z.

What measures do E.V. chargers have to protect people from an external broken P.M.E. neutral situation?

https://www.youtube.com/watch?v=JRHyqouJPzE&vl=en-GB


Z.

The broken PME will bring any metal casing connected to the MET through the CPC to 230V.

So forget for now the EVC in the basement car park.

Lets focus for a moment on the metal casing of a grill oven in the kitchen which is also at 230V under a brokent PME.

Someone touches the casing and stands on the floor in the kitchen.

Will he get a shock?

My logic says he will. However this implies obviously that the kitchen's floor is at 0V and not....PME earth i.e. 230V.

How is this different than the car park's floor while we are touching the metallic car body?

I have never heard anyone asking for a TT system for the....kitchen!

You are of course quite right - and such things do occur - one of the symptoms of a failing PEN is tingles from domestic appliances, as well as dimming or over-brighteing of lights which tends to make people more wary, and such things do normally get reported and fixed smartish..

There is an argument that a house floor is likely to be (but only most of the time) drier, and more likely to have a DPC or even an insulating coat of lino or carpet than a garage or car park. As such the floor is indeed at true terra-firma earth voltage, but via a high resistance, so even padding about the house in pyjamas and bare feet at bed time,  the shock current is still at least limited. And this is where the arguments about earthing of radiators and kitchen sinks, and what to, start to matter. A gas cooker may be well earthed to true earth via a metal gas pipe (it may not be if it is on a hose, but not all are intended to connect that way) , and gas boiler almost certainly is So should we bond the sink to PME earth, or leave it floating? This is one of those questions that is far from clear cut, and the advice to bond the incoming metallic services is an attempt to make sure it all moves as one.

There will always be  cases that are not ideal, outside taps, outside lights and power often mean the PME earth is exposed to touch outdoors, but the risk of this is lower than the risk of not earthing at all, PME faults are quite rare, and normally fixed quickly. It is worth remembering that there are not large numbers of lifeless bodies slumped under the PME supplied metal street lamps and bus stopsevery morning, and the few that are are far more likely to do with late night drinking. (which from an electrical point of view is just as well)

Greetings to ONE & ALL - this is my first Post ever on a IET Site - In brief now "retired" I still enjoy Electronics & of course Electrical work having started in 1970 in the Society of Electronic & Radio Technicians (SERT). Then the 16th in Cornwall some years ago, (TT -  still rules on Farms), my Electronics is from HM Forces (Grey Funnel Line - Royal Navy) now living in a Village in East Sussex therefore TN-C-S with of course PME !! - As I am now & can only be considered, an "enthusiastic amateur" I have embarked on a "Major Re Wire."  Firstly a,  "Full Surge Protection" system & a  Mains Voltage Optimiser to "condition" Mains some days can realise 253 volts plus - Three (3) Separate DBs One (1) Power - One (1)  Luminaires & One (1) Critical/Auxillary  Load(s) - The Critical Loading is fed by a Uninterrupted Power Supply (UPS) the "Generator" will supply Critical Loads on sensing UPS operation - I appreciate sleep at night can be a "Challenge"  & so finally onto EVC. The Charging Point will be outside the Garage, (no room in the garage for a car). The Site has had the, "GOV. Grant  Survey" I am using 10mm SWA from my Sub Station to the Garage - I was told 6 mm was "ok" BUT would get warm on "rapid charge"  - My Point on "True Earth on Solid Floor" is very simple - Electricity will NEVER miss the chance to find "Earth" - as was explained to us in South Shields Marine College.  We are only, "RESISTIVE SHUNTS." Then having debated Footwear from Flip Flops to Hob Nail Boots & "No Footwear" whatsoever. Whether it is raining or washing the Car/Caravan & people do pursue these occupation(s) on Sundays & the Car can be half in & out of the Garage (Scenarios are numerous) !! - MY personal view is to install an "Isolation Transformer" the price is worth the Life !! - after all we have installed them in Shower/Bathrooms standing "Bare Foot" (wet shave is bestest). No "TT" stick required - O well, back to studying PME & Generator (7.5 KVA) Earthing. Remember the "Ole Pneumonic" SIDE = Switch Off - Isolate - Dump & Earth  I cannot wait for PME to fail "deal with the challenge."