Formulation of Instantaneous Fault-Branch Currents in Case of Cross-Circuit Faults on Asymmetrical Double-Circuit Transmission Lines

Cross-circuit faults (CCFs) are atypical short-circuit faults occurring between two dissimilar phases of the different circuits of double-circuit transmission lines with a high occurrence probability. Circuit analysis of the asymmetrical double-circuit lines’ model in such fault cases is a sophisticated one, particularly in the time domain, because all the mutually coupled six phases of the line circuits are to be essentially incorporated. From analyzing the circuit model of asymmetrical double-circuit lines with non-identical circuits on a time domain basis, this paper develops clear-cut formulas governing the instantaneous fault-branch currents flowing from the faulty phases at the fault point into the fault branches during CCFs. They are acquired in terms of the line one-end circuits’ phase currents and the fault location measured from the same end. The proposed formulas can readily be employed in practical applications such as fault analysis, line relaying/protection, and fault location/classification, particularly, those intended to be developed in the time domain in the case of CCFs. The formulas are validated via the simulation studies in PSCAD/EMTDC with an accurate time-domain model of the asymmetrical lines.