Time Evolution of a Short Circuit Current

When a short circuit occurs in a power system, the time evolution of the fault current depends mainly on the system's - (reactance to resistance) ratio and on the fault occurrence angle (measured relative to the system's voltage) [1].
This Demonstration shows a typical short circuit current (plotted in red) for a single phase, assuming no load current before time for simplicity. The fault current's DC exponentially decaying component is also plotted, as well as the positive and negative envelopes; these three components are plotted in dashed lines. The sinusoidal voltage is plotted in black.


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The - ratio ranges from almost 0 (an ideal purely resistive fault) to 25 (corresponding to an impedance angle of 87.7º, an almost purely inductive fault). You can vary the fault angle between 0º and 90º relative to the voltage.
[1] Richard Roeper, Short Circuit Currents in Three-Phase Systems, 2nd ed., Berlin: Siemens Aktiengesellschaft, 1985.
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