Synchrophasors-Based Transmission Line Protection in the Presence of STATCOM

Distance relay identifies the type and location of fault by measuring the transmission line impedance. However, any other factors that cause miscalculating the measured impedance make the relay detect the fault in incorrect location or do not detect the fault at all. One of the important factors which directly increases the measured impedance by the relay is fault resistance. Another factor that indirectly changes the impedance of the transmission line is static synchronous compensator (STATCOM). When a fault occurs, measured signals by the relay change due to the variation of current injected by the STATCOM and it makes the calculated impedance to be incorrect. This paper provides a method based on the combination of distance and differential protection. At first, faulty transmission line is detected according to the current data of buses. After that the fault location is calculated using the proposed algorithm on the transmission line. This algorithm is based on active power calculation of the buses. Fault resistance is calculated from the active powers, and its effect will be deducted from calculated impedance by the algorithm. Furthermore, by choosing the appropriate data bus, the effect of STATCOM is eliminated and fault location will be detected. © 2016, Brazilian Society for Automatics--SBA.