[AMPS] Re: AC Mains in Europe

[David Kirkby]

Steve Powlishen wrote:
> 
> Quick question on how the AC mains in Europe
> are set up.
> 
There are 3 wires - live neutral and earth. Neutral and earth are joined
at the substation, so there at least there is 0 V between them. By the
time it reaches your house, there can be a small voltage between them,
but it will be small ( 1 V or so). You should take power between live
and neutral, which has 230 V between them. Hence live to earth will be
close to 230 V too, not 115 V as you might be thinking. 

Neutral and earth can have a small voltage difference, due to the
non-zero neutral current. In a fully balanced 3 phase system, neutral
current would be zero and so neutral-earth voltage zero. In practise
this is not quite so. 

Here is an interesting story. The electricity meter, which charges by kW
hr, does not use the neutral to measure current. (It does use it to
measure voltage, and hence power) Someone once told me of a friend who
used the small voltage between neutral and earth to generate sufficient
power to heat his greenhouse. This is free electricity, as the meter
does not record it.

I measured the voltage and current once between N and E and while I
found it was possible to extract some power, it would not have been
sufficient to heat a dolls house. Trying this will also trip any earth
leakage circuit breakers, so it is not a good idea, but I thought it
might interest someone. 

-- 
Dr. David Kirkby Ph.D,
email: drkirkby@ntlwold.com (formally davek@medphys.ucl.ac.uk)
web page: http://www.david-kirkby.co.uk       
Amateur radio callsign: G8WRB

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