A useful methodology for analyzing distance relays performance during simple and inter-circuit faults in multi-circuit lines

A methodology for evaluating and visualising the response of power system distance protection units most commonly used is presented. A general case, with different topologies, of a double-circuit transmission line is considered and different types of inter-circuit faults are treated. Single line and simple faults are simplified cases of the general one. Faults are treated by means of the adequate connection between the sequence networks, where different types of faults are represented by a resistance star associated to both lines and ground. Different combinations of these resistances result in different types of faults. Fault conditions are introduced to sequence networks of the rest of the system through phase current controlled current sources, and the resulting sequence voltages at the fault point are applied to fault resistances through sequence voltage controlled voltage sources. To calculate faults the mesh analysis method has been modified to take into account the dependencies fixed by the controlled sources. Real previous state of the power system (load flow, sequence source impedances at both ends and sequence impedance between ends) is taken into account. A useful and reliable way of representation is presented to obtain the expected response of different types of distance units in multi-circuit lines in presence of inter-circuit simultaneous faults.