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    devarajan7's Avatar
    devarajan7 Posts: 1, Reputation: 1
    New Member

    Jan 28, 2009, 04:09 AM
    How to calculate the short circuit current flow in a three phase circuit
    How to calculate the short circuit current flow in a three phase circuit?
    sathe1963's Avatar
    sathe1963 Posts: 97, Reputation: 4
    Junior Member

    Apr 19, 2009, 08:21 AM
    To calculate short circuit current flow in a 3 ph. Circuit, we should know % impedance of source like transformer or generator. Fault mva = base mva / % impedance. On obtaining fault mva, we could find out a.
    I Newton's Avatar
    I Newton Posts: 110, Reputation: 8
    Junior Member

    Jan 4, 2010, 02:37 AM

    In short:

    If the impedance of the transformer is 5%
    If the full load current of the transformer is 1000A
    The short circuit current is 20 times the full load current

    i.e. short circuit current = 20,000A
    anasmemon's Avatar
    anasmemon Posts: 3, Reputation: 1
    New Member

    Mar 10, 2011, 01:52 AM

    STC is maximum fault current that a system is designed to withstand.For obtaining STC it will be as following example.

    Conider a 10 MVA transformer with 6.5% Impedance. System voltage is 13.8/4.16KV. Now Fault MVA = base MVA/PU Impedance

    So Fault MVA=10/0.065=153MVA

    Now Fault Current = 153*1000/(1.73*4.16)=21259A = 21KA

    I hope this can help

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