Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Power Transmission through Transmission Lines

  1. Feb 8, 2016 #1

    cnh1995

    User Avatar
    Homework Helper

    In the numericals based on transmission line, the wording is like this-" A transmission line feeds power to a load at 132kV, 0.8 pf lagging and so on." In practice, are pf and
    current really constant? Doesn't it depend on the load? I mean, every minute someone is switching something on and something off. If the current waveform for a minute is plotted, how will it look? Will the pf be constant? By pf , I mean transmission line pf.
     
  2. jcsd
  3. Feb 8, 2016 #2

    anorlunda

    User Avatar
    Science Advisor
    Gold Member

    Yes, of course the loads change all the time. That doesn't mean that you can't quote an average value or a specific value as an example.
     
  4. Feb 8, 2016 #3

    cnh1995

    User Avatar
    Homework Helper

    So, if the current waveform for a minute is plotted, it has to be of variable amplitude(provided the load is changning). But for the numericals, some specific value is taken for convenience, right?
     
  5. Feb 8, 2016 #4

    anorlunda

    User Avatar
    Science Advisor
    Gold Member

    It is a simplification. AC analysis with P+jQ does assume an average over an integral number of pure cycles. But we also use it when the average is time variant. We simply ignore the distortions in the sinusoidal. Nevertheless, the approximations are highly accurate and often verified.

    Most students never realize the apparent contradiction between "static" AC analysis and time varying averages. Good for you.
     
  6. Feb 8, 2016 #5

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    And when a car goes along the road, it will keep changing its velocity and power output.That doesn't stop us from doing calculations about a specific set of conditions. Things can rapidly get very complicated in real life so we have to start with a simple case.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Power Transmission through Transmission Lines
Loading...