"Frank Erskine" wrote in message
...
On Sat, 30 Aug 2008 23:02:59 +0100, "Ron Lowe"
ronATlowe-famlyDOTmeDOTukSPURIOUS wrote:

"Dave Plowman (News)" wrote in message
...
That's because there's no such thing as polarity with AC - unless you
ground one leg as the UK does. Not all countries do.

Now, that's a whole can of worms I never really got my head round.

*Why* do we have one leg ( Neutral ) referenced to earth?
The reason for earthing one side of the mains is that by so doing, you
prevent the mains from floating to a dangerous voltage due to leakage
in the substation transformer, or indeed faulty appliances owned by
somebody else off the same feed.

--
Frank Erskine


I'll need to think about that.

What does "floating to a dangerous voltage" mean?
To a dangerous voltage with respect to what?
Earth?
A floating system has undefined voltage WRT earth.

I'm trying to imagine an actual fault scenario, where a floating L-N pair
can float to a 'dangerous voltage' WRT earth. If the whole system is
floating, then there's no such thing as a 'dangerous voltage'.

Hmm, perhaps if one leg leaks to earth at the substation, then the system no
longer floats, and there's the possibility of shock WRT earth.

Need to think some more.

--
Ron