Keith wrote:
"Are you sure you want to discard all thoughts of the instantaneous?

Certainly not, but it has little application to power in transmission
line problems.

Power is the rate of transferring energy or the rate of doing work.
Electrical power is measured in joules per seconds or more succinctly in
watts.

What is the value in watts or joules per second when seconds equal
zero? I venture an answer: It is the V x I x cos. theta at that instant,
but since work is power x time, it won`t do anything for you in zero
seconds.

Best regards, Richard Harrison, KB5WZI