Ingineer said:
Imagine a child standing barefoot in wet grass, touching your Leaf, which could, without an earth-referenced ground, pass lethal current, and also, the EVSE's GFCI will not detect it if the fault is caused by some other device, such as a simple extension cord end, dropped in a puddle or mud.
OK, I see now you mean all this happening at once. To be more explicit: a 120V generator with three receptacles, one has the EVSE going to the car, one has the "neutral"-EGC low resistance grounding plug, and one has an extension cord whose other end I carelessly throw into a puddle of water.
For simplicity, say only the "hot" wipers are in the water, so the earth gets energized but there is no return path to the generator. That is, until I come along and stand in the wet grass and touch the car. Then my body completes the circuit via the "neutral"-EGC bond and I get a shock. If the "hot" - earth connection and the connection through my body are both 1000 ohms, then I get 60 ma through my body and that could be lethal.
Back to my original question, does adding a ground rod to this scenario make it safe? The ground rod presents another return path from earth of lower resistance than the path through my body. Say the ground rod has a resistance of 100 ohms. Then the total current through the extension cord increases to 110 ma, but the current through my body reduces to 10 ma. So I still get a shock, but it shouldn't be dangerous.
However, this is very sensitive to the actual resistances involved. If the ground rod resistance is 300 ohms, the puddle resistance is 300 ohms, and my body resistance stays 1000 ohms, then the current through the extension cord is over 200 ma, and the current through my body is up to 50 ma, which is dangerous or possiblely lethal.
So as far as I can see, while a ground rod makes this installation safer, it doesn't remove the risk in this scenario.
Cheers, Wayne