The Effects of Different Load Power Factors on the Performance of Distance Relay

A Distance Relay typically used as main protection relay to protect transmission line from any type of fault. It is very sensitive to voltage and current variation because it uses the impedance measurement principle to detect fault occurrence and fault zone. The impedance measured by distance relay might be different from the actual fault impedance from relay point until fault point because of various factors and one of it is load variation. This research aims to analyze the effects of load power factor variation on the accuracy of distance relay. Transmission line, three-phase source, three-phase load and distance relay were modeled using Matlab/Simulink software. Single line-to-ground (SLG) fault algorithm and Mho characteristic have been chosen in this research to analyze the effects of load variation. Power factor of the load was varied by varying load reactive power to be inductive and capacitive. From the results, it can be concluded that distance relay will be mal-operated for faults near zone reach setting when power factor is less than unity for either lagging or leading conditions.