Performance analysis of distance protection using different impedance calculation methods

Abstract

Various combinations of voltages and currents are possible in the power system in an event of fault. Distance relays use these voltage and current phasors, obtained from PTs and CTs, to calculate impedance. The relay operates when the calculated impedance is below the reach or set impedance. The operation can be better understood when plotted on an impedance plane. Mho circles and quadrilateral characteristic are essentially the most popular characteristics used all across the world since they are inherently directional and provide well defined reach with minimal over reaching and under reaching errors. All the impedance points that lie within the characteristic are considered operating points.