Static characteristics analysis of ground MHO distance relay for UHV lines

UHV/EHV long transmission lines have large distributed capacitance and shunt reactors, which may have significant effects on the operation of a traditional distance relay. The distance relay without considering any of the above two factors will operate with serious overreaching or underreaching. Several papers have analysed these effects on the measuring impedance of distance relay and proposes different schemes to ensure the reliability and selectivity of distance relay for UHV/EHV long transmission lines. This paper compares the static characteristics of these schemes, and proposes a hybrid scheme which is easier to calculate and set.