EC-based relaying scheme for the protection of shunt-compensated transmission line

Static Var Compensator (SVC) is used to enhance the power flow in the transmission line by improving the voltage profile. SVC injects/draws the reactive power by varying its susceptance. This variation in susceptance offers new challenges to the ordinary protection techniques. The direction of superimposed energy (SE) can be used to discriminate between forward and reverse faults. However, SE depends on various parameters such as the fault location, fault type, and fault resistance. This dependency makes it difficult to select proper threshold value to identify the faulty phase. Therefore, energy coefficients (ECs) are proposed and are utilized to identify the fault direction and to further classify the type of fault. If both the relays sense the forward fault, it is identified as a fault in the protected line else it is a fault outside protected zone. As the energy is dependent on the real line parameters only, this EC-based scheme is reliable for variable shunt reactive compensation. The EC-based algorithm magnificently senses the faults in the protected zone and identifies the fault type under varying system conditions i.e. different fault locations, types, and resistances. The proposed scheme is unaffected by the SVC dynamics, modes and changes in system configuration.