There is no power loss in either pure capacitance or pure inductance.
There is loss only in the resistive (or conductive) components: the RF
resistance in the wire and the RF conductance in the dielectric. It is
fundamental that the inductance and capacitance in a TEM transmission
line are just what cause the energy to propagate from one end to the
other...or I suppose if you view it at a higher level, you could say
that the same fields which yield the effects we call capacitance and
inductance also cause the propagation of energy when they result from a
TEM transmission line configuration. I'm sure other valid ways of
looking at the situation exist too. (I should also mention that there
can be some power lost to radiation, but in most cases that's quite
small.)

Increased loss at high frequencies comes from several sources: smaller
skin depth at higher frequencies means higher resistance in the wires.
That goes up as the square root of frequency, once you get to a skin
depth which is small compared with the thickness of the copper. Higher
frequencies result in higher dielectric loss, though that's generally
not an issue below a few GHz. But imperfections along a line can cause
significant attenuation because of multiple reflections; dozens of
small reflections can add up to a big problem.

Cheers,
Tom


Cheers,
Tom