Sylvia Else wrote:
Phil Allison wrote:
The MEN system:

In Australia, AC power delivery uses a system called " Multiple Earth
Neutral " - which requires that the neutral conductors in a premises
be connected to the plumbing system at the distribution board (ie
power box). It also requires that an earth stake be installed for the
same purpose, but some older premises may not have this.

If as you say, neutral has to be tied to Earth at the premises, then I
can indeed see that the situation might not be so bad.

Grounding the mains to "plumbing" *was* common in the US many
years ago. Now, I believe, you *must* ground to a metal
rod driven into the earth (8 ft?). Note that if the water
meter was removed, your earth-through-plumbing would fail.

On the face of it, having significant current flowing from neutral to
Earth would have to indicate a fault. It would be nice for the breakers
to trip in such a situation, but I can't see that they will.

This is how GFCI breakers work -- they watch for current "leaking"
off to ground someplace other than in the "return" conductor.