Impact of Shunt-flexible AC Transmission System on Distance Protection of transmission Lines

Abstract

In recent years, a new technology – Flexible AC Transmission Systems (FACTS) is introduced in the power system. This technology could increase the transmission line capability, control the power flow, and enhance the transient stability of the power system effectively. Due to the injection of the FACTS components; the line parameters of transmission system will be changed. Therefore, the power system protection relay’s operation will be influenced. This dissertation explores an apparent impedance calculation procedure for transmission line incorporating Static Synchronous Compensator (STATCOM) (which is a vigorous component of FACTS) based on the power frequency sequence circuits. A detailed model of 6 pulses STATCOM and its control and a mho relay model are proposed and integrated into the transmission system using Power Systems Computer Aided Design (PSCAD) software. The simulation results of the application of conventional distance relay for the protection of transmission line incorporating STATCOM are presented. The simulation results carried out by PSCAD software and the analytical calculations show the impact of STATCOM on the distance protection relay during the different fault condition. The influence of location of STATCOM, the setting of STATCOM's reference voltage and the operation mode of STATCOM on mho distance relay are studied as well. The results are presented in relation to a typical 220kV, 450Km (Atbara- Portsudan) transmission system employing midpoint. III STATCOM at the