Wavelet transform based protection of transmission lines with four quadrant operation of STATCOM

This paper proposes a new wavelet transform based relay logic for the protection of transmission lines compensated with a static synchronous compensator incorporating energy storage device (STATCOM – ES). STATCOM with energy storage systems can operate in any of the four quadrants in P – Q plane. A conventional distance relay with standard settings may not be reliable to identify and categorize short circuit faults in such systems. A simple, fast acting and reliable wavelet based relay logic is presented to accurately identify and categorize transmission line faults in shunt compensated lines. The developed relay discriminates between internal and external faults accurately. It provides reliable protection for the transmission line considering the entire four quadrant operating range of STATCOM – ES and is immune to the value of fault resistance.