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Elec Eng AC 3 Phase Symmetrical Components Q - Phase to Fault question

  1. Oct 7, 2014 #1
    Hello again,

    I've got another question that involves symmetrical components, this time I've attempted it.

    The Question follows:

    1. In a 3 phase circuit with resistance earthed and neutral and earth fault in phase “A” which produces a fault current of 800 amps.

    Load currents may be taken as zero.

    What will be the positive, negative and zero sequence currents in this system?

    Answer

    I have Ia = 800 for Phase A, Ib = 0 and Ic = 0 and I assume this is a Phase-to-earth fault

    According to this source https://www.selinc.com/WorkArea/DownloadAsset.aspx?id=100688, when Phase B and Phase C is zero (as suggested by "Load currents may be taken as zero"): the zero,
    positive and negative sequence are all 1/3Ia. It also says that when an phase to earth fault happens in Phase A: Phase B and Phase C can be assumed to have no current anyway.

    Therefore Ia = 800A and I0, I1, I2 = 267A. Is my answer and thought process right?

    Cheers:)
     
  2. jcsd
  3. Oct 8, 2014 #2
    Yes, it's correct
     
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