Robustness of Communication aided Distance Relay with Mho Characteristic against Fault Resistance

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