Measured impedance for inter phase faults on next line and second circuit of a double circuit line

Distance relays are one of the mostly used protective devices in the transmission systems. These relays are used as the main, the first zone and a part of the second zone, and the backup, the rest of the second zone and the third zone, protective devices. Fault resistance is a source of error for distance relays in the form of the measured impedance deviation from its actual value. This paper compares the measured impedance a by distance relay on a double circuit line for the faults on the next line and the second circuit of the line, in the case of inter phase, phase to phase and three phase, faults. This is done by presenting the measured impedance at the relaying point and distance relay ideal tripping characteristic. The variation of the ideal tripping characteristic due to the changes in the power system parameters is investigated.