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Calculate 3ph short circuit symmetrical fault, per unit method.

  1. Feb 21, 2013 #1
    1. The problem statement, all variables and given/known data

    Calculate the three-phase short-circuit fault currents flowing into all five busbars.

    2. Relevant equations

    MVA base = 150MVA
    All base voltages were set to the local busbar voltages.

    Formulas I have used can be seen in the attached photos.

    3. The attempt at a solution

    I have attached two photos, the first shows me calculating the short-circuit fault current to busbar 5. I have made a per unit diagram and ignored the j terms as there is not resistance for less hassle. I have simulated this using software and it confirms my answer.

    The next photo is the problem I'm stuck on, calculating the short-circuit fault current to busbar 2 (BB2). I get stuck because I can't simplify the circuit anymore to get the X fault per unit value. I have tried to use current and voltage dividers, but can't get anywhere near the answer. I have also simulated this problem and get the answer to be 15.954kA

    Any help would be great, and please ask if you need more information.

    thanks
     

    Attached Files:

  2. jcsd
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