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The US electrical system
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Gyro:
John Ward has a useful video on the subject (EV charger earthing)...  https://youtu.be/gZVx7GbAwlg

There are also an increasing number of chargers with earth fault detection, which do not require separate earthing... https://youtu.be/3-HEKqeSrwk
helius:

--- Quote from: tom66 on June 29, 2020, 12:50:52 pm ---The risk is that if PEN fails due to cable damage, corrosion, poor maintenance etc then, although power to the building will be lost, the PEN can effectively float towards Live as any appliance that conducts current in the "off state" (think fridge compressors, heating elements, even some SMPSes) will pull that PEN node up via a low impedance node.
--- End quote ---
The same situation in North America is called a broken neutral, and because of the split pole arrangement, does not cause power to the building to be lost! The tell-tale sign is when some of the lights dim or grow brighter in concert with a refrigerator or heater cycling on and off. Incandescents show the effect most because they run unregulated.


--- Quote ---- Earth rods until the impedance is below some nominal figure, which can often require 5+ earth rods to be drilled in to the driveway and fitted (expensive, time consuming)
--- End quote ---
Measuring earth bonding also requires the installation of temporary grounding rods at some distance (100') to null the effect of local potential variations in the earth (caused by earth leakage). This is obviously complicated in a neighborhood with small subdivisions. And driving 10' grounding rods is no fun...
Monkeh:

--- Quote from: richard.cs on June 29, 2020, 01:55:36 pm ---
--- Quote from: Monkeh on June 29, 2020, 01:37:25 pm ---And this is a rather overblown concern IMO, but it is in fact proving to be a pain.

--- End quote ---

Well yes, it's not introducing a genuinely new risk, the general public was already hopelessly unaware of the risk of outdoor class I appliances with TNC-S earthing and happily bought all manner of earthed metalwork outdoors (outside of the equipotential zone), in addition to the various light fittings, outdoor taps and gas pipes (which now seem to default to running along outside walls) that form part of the installation more generally. The only difference with electric cars is that it's a new kind of class I appliance intended for use outdoors (rather than incidentally used as such), and lots of people have got in a bit of a panic about it. Class II cars would be possible, but it's now rather too late for that.

Generally the safety case for TNC-S in the UK has been looking progressively poorer for decades as the metallic water and gas pipes that used to provide free sub-Ohm backup earthing have disappeared, and the promised reliability of double-crimped neutral connections has not really been achieved.

--- End quote ---

Now, I could be wrong, but as far as I'm aware most electric cars do not connect the charging CPC to the chassis. That coupled with plastic handles and extremely high quality paint finishes leaves me entirely unconcerned about taking a belt off a car. Oh, that and like most people I walk around on a big sheet of rubber, not my bare feet.

I do, however, think we should never have used TN-C-S as an excuse not to properly control potential at the installation. It's a perfectly good system for ensuring a nice low impedance fault path for currents in normal operation without using lots of extra copper (or lead, or alu), but a poor excuse for not having good earthing at the property (and the American method of whacking a rod in quickly doesn't cut it).
tom66:

--- Quote from: Monkeh on June 29, 2020, 02:42:20 pm ---Now, I could be wrong, but as far as I'm aware most electric cars do not connect the charging CPC to the chassis. That coupled with plastic handles and extremely high quality paint finishes leaves me entirely unconcerned about taking a belt off a car. Oh, that and like most people I walk around on a big sheet of rubber, not my bare feet.
--- End quote ---

You would unfortunately be incorrect.  The chassis of my PHEV VW Golf GTE is connected to the earth pin on the type 2 connector.  This means 12V battery earth and the Type 2 connector earth are the same.

While the paint on the vehicle provides some level of insulation (I was unable to measure a direct connection, although I of course did not press into the paint) parts of the car like the door locks and frame were found to be conductive in my tests.  It's possible to imagine someone stepping into their car and getting a shock that way. Also, the trailer connection if fitted would expose this, as would cigarette lighter/USB convenience socket or parts under the engine compartment.

I actually measured a direct connection from the alloy wheels to the protective earth if you want to talk about an interesting way to get a shock. I guess there are some bearings somewhere that are chassis connected.
Monkeh:
Well, that's a shame. Roll out the earth mats (not that anyone wants to spend money on infrastructure).
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