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Homework Help: Transmission Line, Max Real Power Transfer

  1. Feb 25, 2014 #1
    1. The problem statement, all variables and given/known data

    A 230kV, 160km long transmission line has the following parameters expressed on a 230kV, 100MVA base.

    R = 0.0151
    X = 0.1476
    Y = 0.288

    The sending end voltage of the line is held constant at 1.0 pu. The load at the receiving end has a lagging power factor of 0.8.

    Show that the Thevenin equivalent yields,

    [tex]V_{Th} = 1.022 \angle -0.13^{\circ}[/tex]

    [tex]Z_{Th} = 0.0158 + j0.15077[/tex]

    2. Relevant equations

    3. The attempt at a solution

    See figure attached for my attempt.

    I'm confused regarding the maximum real power transfer limit.

    Is this supposed to be calculated assuming,

    [tex]Z_{load} = Z_{Th}^{*}[/tex]

    or are we supposed to use the PF of the load stated in the question somehow?

    Thanks again!

    Attached Files:

  2. jcsd
  3. Feb 26, 2014 #2


    User Avatar

    Staff: Mentor

    While it may seem to be hinting at conjugate matching, as far as power transmission goes that sounds unrealistic to me. Who would be happy to have a load voltage just half of what the power station was supplying? With half of the station's power output going to heat in the powerline? It's overdoing the de-icing just a tad.

    Maybe they are asking what power you could get to that load if you used powerfactor correction?

    When in doubt, ask your professor for clarification.
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