Optimum Setting of Distance Protection Scheme for HV Transmission Line

Abstract

Protective relays in a power system are used to detect system abnormalities and to execute appropriate commands to isolate swiftly only the faulty component from healthy system.  One of the protective relay is the distance relay. When the fault occurs it is seen that large amount of current flows through the network. The distance relay detect the over current by measuring the impedance of the transmission line and send the tripping signal to the circuit breaker to isolate the power line.  This paper focuses on determining the optimum setting and the performance of the distance relay when different types of faults occur in the system.  The modeling and analysis of the test system with corresponding relay circuits have been carried out by using Power System Computer Aided Design PSCAD.  From the simulation, it can be observed that the fault voltage, fault current, mho relay settings and its characteristics are consistent with those from the theoretical concept.

Keywords: high voltage transmission line, distance relay settings, Mho relay characteristics, PSCAD-EMTDC