Three-Zone Distance Protection of the Transmission Line Considering High Resistance Fault (HRF)

Transmission lines play an important role in power grids. Protection of transmission lines is a challenging task looking at the reliability and economics of the power supply. There are various kinds of faults occurring on the transmission line from time to time with wide variations in fault parameters. This paper describes the identification of faults on the transmission line with high resistance in the fault path. Moreover, a three-zone stepped distance relay is developed with Mho characteristics. The identification of line fault is realized through the sensing of current and voltage signals. FFT analysis is used to derive the magnitude and phase angle of captured signals. Sequence filters are designed to transform the phasors of voltage and currents in sequence components. Later, using the impedance measurement block, fault resistance, and reactance are estimated for ground and phase faults. The system is simulated in PSACD software using the Bergeron Transmission line model. A distance relay with Mho characteristics is set for three different zones to provide local and backup protection to the grid-tied transmission line. Various fault cases are generated with wide variations in parameters including high resistance faults. The relay operates successfully concerning the types and locations of faults in the considered transmission line.