26 Apr
1999
26 Apr
'99
3:12 p.m.
On Mon, 26 Apr 1999, Daniel T. Burrows wrote:
Maybe where you're at, but generally not here (small town Illinois).
In the more-populated rural areas (10 or so houses per mile) all 3 phases
of the 12kV local loop are run. If the houses are all about the same age,
each pole-pig is fed off successive pairs of phases (AB, BC, CA,...).
Newer houses jumble this slightly. Rarely, in sparse areas or
clusters of houses in the middle of nowhere, a single big pole-pig
converts to about 4kV to ground. Then smaller ones make the 234V.
I've always
seen it shown in diagrams with the primary connected across two
phases of the three-phase. Otherwise you need a high-current return path
somewhere else.
Take a close look at rural areas and there is only 1 High voltage line
present.
It is fed to the HT input of all the pole transformers. When there are 3 phases available that sometimes is
the case. Look closely
at the pole transformers and in most cases when there are 2 or more
transformers mounted on 1 pole there is only 1 HT input to each transformer.
If it were between phases there would be 2 HT inputs.
??? Every place that I've seen that has 2 or 3 12kV-to-234V transformers
has them between pairs of phases.
Richard
rws(a)enteract.com