On Jan 9, 10:46*pm, Cecil Moore wrote:
On Jan 9, 3:33 pm, Gene Fuller wrote:
Reflections *ARE* power factor problems. When the power company brings
the power factor to unity, they have eliminated reflections and turned
the system into a traveling wave energy delivery system.

This would not be quite correct. The power factor correction
capacitors make the load impedance real, they do not match
the load to the impedance of the distribution line. As such,
they have not eliminated reflections.

Since the customer decides on the load impedance (infinity
when the equipment is disconnected), the power company is
always dealing with mismatched loads. And does not seem
too concerned as long as the load is close to real.

It might be instructive to consider some real transmission
systems. From La Grande-2 (5.6 GW) or Churchill Falls (5.4 GW)
to the first significant load center is about 1/4 wave
at 60 Hertz. Churchill Falls has three 735 kV lines to move
the energy; 1.8 GW per line. At 735 kV, that's about a
300 ohm load impedance. I've seen estimates that put power
line impedance between 100 and 400 ohms. So there might be
a match at full load, but at no load there is serious
mismatch. Of course the generator impedance is close
to zero (feedback achieves this) so there is no attempt
to match at that end. (The above quick analysis ignores
that it is actually a three phase system).

There are apparently serious challenges with keeping
the output voltage down on lightly loaded lines (q.v.
Ferranti effect).

And what happens when the load breakers at the end of
the line trip. 4 milliseconds later the reflected wave
arrives back at the plant. What happens when it hits
the 0 output impedance of the generators?
And how does one stop 11 columns of water 1000 feet
high (500 psi) and 20 feet in diameter before the
generators overspeed?

I am betting there is a story there.

...Keith