EFFECTS OF SERIES COMPENSATION ON DISTANCE PROTECTION OF HIGH VOLTAGE TRANSMISSION LINES UNDER FAULT CONDITIONS

Advent in power electronics enhanced the dynamic performance of modern power system and Flexible AC Transmission Systems (FACTS) provided vital solution for it. FACTS are basically thyristor-controlled devices which control the active and reactive power flow in the network and are equally adaptive to voltage magnitude control thus, utilize the existing power network optimally. But increase in complexity, configurations and total power transmitted lead to a number of problems in relation to transmission line protection. The most widely used protection system in case of high voltage and extra high voltage transmission lines is Distance protection. However, installation of series compensation system creates problems for protective relays and fault locators due to change in the magnitudes and directions of fault voltages and currents in the networks and causes malfunctioning of the distance relay. Since protection of transmission lines plays crucial role in improving the stability and reliability of electric power systems, this paper also throws light on the impact. MATLAB/SIMULINK is used effectively in modelling and simulation of distance relay as well as transmission line compensated with thyristor-controlled series compensator. The simulation results illustrate the effective use of MATLAB/SIMULINK in understanding the behaviour of distance relay in protecting the transmission lines with and without compensation.