Hi Mike,

On 27-Dec-02, MIKE ROSS wrote to Roy J. Tellason:

 JB>>> you to see something really wierd, in some places they
 JB>>> distribute the power to consumers with a single conductor and
 JB>>> use a ground return,

 RJT>> Wouldn't there be some nontrivial resistance there?

 JB>> yeah, that doesn't seem to stop them doing it though.

 MR> In my metropolitan area the distribution wire branches off one of
 MR> the 3-phases and carries a few thousand volts along the top of the
 MR> poles. Every few homes there will be a transformer (pole pig) to
 MR> reduce the voltage to household levels and it is grounded. It may
 MR> seem like there is no return except through ground but don't
 MR> forget the utility poles tend to carry phone and cable service too
 MR> and these are supported by steel cables which are grounded every
 MR> few poles. Though iron may have more resistivity than copper it is
 MR> still better than the earth path in between each pole pig. I can't
 MR> say if it is the same in rural areas.

In the UK the system generally has transformers to final distibution
voltage as fairly large, ground based items. They are usually 33 Kv to
415 v three phase (240 v phase to ground), and final distribution is
by 3 phase along the street (usually underground in urban areas and
new rural developments), with a continuity earth. Each house is tapped
off one phase and ground, and if they get the balance right there is
only a small residual current in the earth wire.
In rural communities final distribution is three phase on poles,
otherwise as above.
For isolated farms/houses and hamlets the 33 Kv distribution is single
phase and there are pole mounted transformers at point of use for
every house/small group of houses.

George

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