Originally Posted by cowboy99
...Will that HV short to 'earth' throw(blow) the beaker(fuse) that connects it to mains power ???...
For typical dirt-rod, it will NEVER blow the fuse.
I've done just that, except with lamp-limiter and meters. (You often can't get good dirt resistance readings with a low-V ohmmeter.) One dirt rod in my mineral soil runs 100-120 Ohms. On 120V power, it will pass hardly over 1 Amp. 240V to the house is run 120V each side of neutral/ground, so same answer.
FYI: this 1A current is not enough for welding (maybe thin foil with a needle-rod).
Even if you do get 25 Ohms, that's only 5 Amps. Not a fuse-popper, and real lame welder.
"Ground" does NOT "protect" against normal power-company power. It diverts stray leakage in transformer, and tends to divert lightning and HV crosses.
Jumper live 120V directly to the power company Neutral, fuses pop. My very long line will max-out at 800A (on 100A main breaker). Shorter feeders (dense housing) can deliver over 10,000 Amps to a dead short (fuses/breakers try to jump out of the box; 22,000A rating is now common on Service Equipment).
I believe my numbers are typical for 50+% of houses. The NEC wants 25 Ohms, and at 100+ Ohms I am required to drive a second dirt rod. Many many good installations just put in 2 rods, knowing that 1 rod is rarely enough, except in very wet mucky soil. NEC does not require testing 2 rods for <25r, recognizing that some places that would be impractical. (I actually have 5, and may be near 25 Ohms. )
Last edited by PRR; 10th February 2018 at 03:37 AM.