Unbalanced short-circuit calculation by phase coordinates

This paper demonstrates a direct approach for fault current calculations without using symmetrical components. By representing a polyphase network in phase-coordinates, i.e. phase voltages, currents and impedances, the unbalanced fault currents can also be analyzed and calculated. The proposed approach is direct and can be implemented easily by solving a set of linear system equations. Identical results for both methods are obtained in a sample network. The following faults are analyzed: phase-to-earth with/without impedance; phase-to-phase fault with/without impedance; two-phase-to-earth fault; and a three-phase fault