IMPACT OF REAL AND REACTIVE POWER CONTROLLABILITY OF STATCOM ON TRANSMISSION LINE PROTECTION

Static synchronous Compensator (STATCOM) is a shunt connected Voltage Source Converter (VSC) based FACTS controller which is useful in improving the voltage regulation. VSC based FACTS controllers facilitate connection of energy storage devices like battery, fuel cell, Super Magnetic Energy Storage(SMES) etc. at the DC bus. Addition of energy storage device results in better real and reactive power flow control, transient stability enhancement and power oscillation damping. However, FACTS controllers with energy storage device in the line poses new challenges for the line protection device. Operating region of STATCOM with energy storage device (STATCOM – ES) encompasses all the four quadrants in P – Q plane. Impedance contribution by STATCOM operating in any of these four quadrants can modify apparent impedance seen by distance relay and hence needs to be investigated thoroughly. Main aim of this paper is to analyze the impact of emulated conductance and susceptance by four quadrant operation of STATCOM on the performance of distance relay in a hybrid compensated system. A novel control strategy to dynamically modify the reference for real power exchange by STATCOM is proposed to avoid damage to the STATCOM during fault. Possibilities of distance relay under reach and over reach due to operation of STATCOM ES in various operating modes and impact of fault resistance on the relay performance is discussed.