Measured impedance by distance relay in second protective zone

Distance relays are one of the mostly used protective devices in the transmission systems. These relays are used as the main, First zone and a part of second zone, and the backup, the rest of second zone and 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 investigates the measured impedance by distance relays for the faults on the next line by means of measured impedance calculation and its variation duo the changes in the power system parameters.