Open-circuit (series) faults — a broken conductor in one or two phases — are modeled by inserting a large (theoretically infinite) series impedance in the affected phase(s), producing asymmetrical currents and voltages that require symmetrical-component (sequence-network) analysis rather than single-phase treatment. Because the fault spans two distinct points in the network, each sequence network is represented as a two-port (rather than one-port) equivalent characterized by open-circuit driving-point and transfer impedances, and the specific interconnection of the positive-, negative-, and zero-sequence networks at those two points depends on which phase(s) are open. This belongs to power system fault analysis, extending the sequence-network methodology used for short-circuit (shunt) faults to series faults, and generalizes into a systematic algorithm (using Thevenin reduction, or Y-bus/Z-bus methods for large systems) for computing fault currents and post-fault bus voltages.
Open-circuit (series) faults — a broken conductor in one or two phases — are modeled by inserting a large (theoretically infinite) series impedance in the affected phase(s), producing asymmetrical cu…