Danny D'Amico formulated on Wednesday :
On Tue, 26 Nov 2013 08:22:27 -0500, clare wrote:

Note the "essentially" - it is not "litterally"

Indeed. The return path to the power company's transformers is complex.

I've found a few references that try to explain it (some of which
are on google books, so I can never tell if you'll see the same
pages that I do).

The math is horrendously complex.

But the summary is simple:
"The power company essentially uses the earth as one of
the wires in the power system. The earth is a pretty good
conductor and it is huge, so it makes a good return path
for electrons."

Anyway, I'm moving on to trying to understand *why* and *when*
the power companies use the wye versus the delta transformers ...

I'm starting with the *simplified* answer, and then working toward
the key details:
http://www.phaseconverterinfo.com/ph...r_deltawye.htm

"Three-phase power is most commonly provided by the electric
utility in a wye configuration. The main advantage to wye power
is that the phase-to-neutral voltage is equal on all three legs."

In Delta configuration there is NO Neutral so whats you point.

The POwer generator almost always uses DELTA configuration of the HV
and Vvery HV lines with only 3 three wires.

The last leg from the local substation to the street transformers (POLE
PIG) will likely be WYE so that each PP only gets a phase and neutral
to convert to 240 volts centre tapped.

--
John G