On Apr 12, 8:06 pm, Cecil Moore wrote:
Owen Duffy wrote:
Cecil, you have conveniently clipped the context (as you do), the
relevant context being the line-load interface and source-line interface.

Following published usenet rules, I trim the part to which
I am not replying.

Statements in some explanations (by others) like "This clearly proves
that reflected power and forward power in a transmission line are both
real power, and that no fictitious power, or reactive volt-amperes,
exists in either one." seem incompatible with the basic AC circuit theory
explanation of a reactive load which must exchange reactive energy with
the transmission line over a complete cycle (and the same effect at the
source end).

Those statements are generally about lossless lines where the
Z0 is purely resistive. In the lossless wave reflection model,
there is no reactive energy in the transmission line. The forward
voltage is in phase with the forward current and the reflected
voltage is 180 degrees out of phase with the reflected current.
Both V*I*cos(theta) terms are in watts with zero vars. Of course,
real world transmission lines have (hopefully negligible) vars.

There are two models that can accurately describe the same
phenomenon: the power folk like VAs, Watts and VARs; the RF folk
like forward and reverse travelling waves. But the phenomenon
is the same. One can indeed describe what happens on a transmission
line in terms of VAs, Watts, and VARs and any line that has a
reverse wave will be found to have VARs. The different terms apply
to different models, not to different situations.

Just another reason why you have to be careful when you think
that the forward and reverse waves necessarily represent real
power. Trust the power folk on this one; they know what represents
real power, they are billing for it. And its Watts. Net. They
only power that counts is the power you can bill for.

....Keith