Robustness of communication aided distance relay with Quadrilateral characteristic against inter phase fault resistance

This paper discusses the maximum fault resistance, which can be tolerated by a communication aided distance relay with Quadrilateral characteristic in the case of inter phase, phase to phase and three phase, faults. This is defined as the boundary fault resistance, which is the maximum fault resistance that the relay can discriminate between in-zone and out-of-zone faults correctly. The robustness criterion is defined based on the boundary fault resistance. In order to achieve this, the related equations are derived and then the boundary fault resistance curve and robustness criterion are presented.