good article at
http://www.rsgb.org/emc/pdfs/leaflets/emc7protectivemultipleearthingmembers.pdf
on PME
-- The trees that are slow to grow bear the best fruit.
-Moliere, actor and playwright (1622-1673)
On 13 May 2008, at 18:29, Stephen Prior wrote:
Don, and others
In older houses in the UK the neutral is bonded to a real ground at
the fuse
box, where the ground is usually a long copper rod just a few feet
away.
There is rarely in my experience more than a volt or two on the
neutral.
More modern houses use PME (protective multiple earthing) where the
neutral
is bonded not at the house but locally at the final step-down
transformer-
the argument being that this forms a higher quality ground I
believe. The
real danger with PME is that the neutral may well then rise above 0
volts,
but in normal circumstances, because plumbing inside the house is
bonded to
'ground', no potential (!) exists for electrocution. Until, that
is, a ham
decides to ground his equipment 'properly' outside. Then large
amounts of
current can potentially flow!
There was an excellent piece on this in Radcom many years ago by Peter
Chadwick G3RZP I think. Ian, GM3SEK will no doubt remember and also
know
far more than me about the issue!
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