Owen Duffy wrote:
The so called "forward power" and "reflected power" are notional values,
but not actual power "components". The only power is the average rate at
which energy passes a point, and it is in one direction or the other.

That statement depends upon the definition of "power"
being used. The IEEE Dictionary has a different
definition of power than does a physics textbook.
The net power is the average rate at which net energy
passes a point. The net power is the difference between
the forward joules/sec and the reflected joules/sec.

Instead of using the word "power", let's switch over to
the dimensions of power, i.e. "joules/second". Those
joules are indeed *actual energy components*.

The so called "forward power" is a forward traveling
EM wave containing energy moving at the speed of light.
There are indeed actual forward joules/sec moving past
a point on the transmission line.

The so called "reflected power" is a rearward traveling
EM wave containing energy moving at the speed of light.
There are indeed actual reflected joules/sec moving past
a point on the transmission line.

Note that an EM wave cannot stand still. According
to the theory of relativity, EM waves always move at
the speed of light (taking VF into account).

Standing waves consist of a forward traveling wave
containing joules/second and a reflected traveling
wave containing joules/second. The joules/second in
those two waves are supplied during the transient
power-on state. During steady-state, that energy has
not yet reached the load. But the total energy contained
in the transmission line during steady-state is exactly
the amount of energy needed to support the forward
traveling wave and the reflected traveling wave. Standing
waves would not be possible without those two real EM
wave energy components traveling in opposite directions.

At power-down, assuming the source is disconnected
from the transmission line, all of the forward wave
energy and reflected wave energy stored in the lossless
transmission line is eventually dissipated in the load.
That happens during a time when the source is supplying
zero energy.
--
73, Cecil http://www.w5dxp.com