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Why do 3 phase balanced faults cause such high fault currents?

  1. Oct 19, 2008 #1
    Not a homework question, Just trying to get more information about it. Its hard to find a textbook or a site that explains this well.

  2. jcsd
  3. Oct 20, 2008 #2
    I don't think that they do as a result of being 3 phase except that a short from phase to phase will draw a higher current than phase to neutral. It may be just a case that 3 phase supplies tend to be higher capacity supplies.
  4. Oct 22, 2008 #3
    It should be remembered that three phase fault current is limited only by the the reactance of the source and perhaps additionally the R and X of any conductors between the source and the fault point. The closer the fault to the source, the higher one should expect the fault current magnitudes to be.
    If your interest in power system faults is strong, try searching for books by Paul M. Anderson, J. Lewis Blackburn, and Walt Elmore. (there are others as well, these just came quickly to mind.)
  5. Jan 7, 2009 #4
    thanks a lot guys.

    I'll be sure to check those books out.

    Its funny how I feel like I haven't learned anything from my college classes.

    How's glover and sarma by the way?
  6. Jan 7, 2009 #5
    Protective Relaying: Principles and Applications, Third Edition (Power Engineering) (Hardcover)
    by J. Lewis Blackburn (Editor), Thomas J. Domin (Editor)

    Is this the Lewis Blackburn book you were referring to? I'll check to see if my college library has it.
  7. Jan 7, 2009 #6


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    Fault currents are highly dependent on the configuration of the circuit's ground reference. Have you studied the differences between Delta and Wye configurations to see how ground-faults can differ?
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