Over-reaching factor for distance relay with Mho characteristic

Fault resistance is a source of error for distance relays by the means of deviating the measured impedance from its actual value. The presence of the fault resistance not only leads to measured resistance deviation, but also the measured reactance deviates from its actual value. This would lead to both under-reaching and over-reaching. This paper investigates the over-reaching aspect by defining an over-reaching factor for Mho distance characteristics. Variation of this factor due to changes in the power system conditions is also discussed.