Mho Characteristic Shifting and Distance Relay Robustness against Fault Resistance

This paper discusses the variation of distance relay robustness criterion as a function of Mho characteristic shifting angle as well as power system conditions. Boundary fault resistance is the maximum tolerable fault resistance which distance relay can discriminate between in-zone and out-of-zone faults. 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 and robustness criterion curves are presented.