Andy Wade wrote:
Ian Stirling wrote:

For reference, I'm in the middle of a village, about 100m from the nearest
substation, and get about 0.5 ohms.

Wow, that's high -- overhead or underground distribution? Have you
tried complaining about undervoltage?

Nope, as I'm not suffering any ill effects from it.

If you've got a voltmeter and enough clue to connect it to the mains without
killing yourself, this is easy to measure.
[...]
Meausuring and using a load on the same circuit isn't a good idea as this
adds that resistance in.

It's absolutely essential to measure on a different circuit to the one
you're loading - or straight on the CU busbars, using fused test leads
of course - otherwise the results you get are meaningless.

True.
Well, it is theoretically possible to compensate, but in practice you'r
either going to need exact lengths of wiring, or some means of measuring,
which will involve another circuit.
Otherwise you add the resistance of the ring back to the fusebox and the
fuse/breaker.