A new principle of traveling wave differential protection on series-capacitor-compensated transmission lines

Traveling wave differential protection has the ability, in theory, to entirely eliminate the effects of distributed capacitive current, but it cannot be applied on series-capacitor-compensated lines directly. In this paper, unbalanced output of conventional forward and reverse traveling wave differential currents under normal operating conditions and external faults was analyzed. A new type of traveling wave differential current was defined by combining forward and reverse traveling wave differential currents. Expressions of the defined differential current when internal and external faults occur were deduced. On this basis, a new principle of traveling wave module differential protection on series-capacitor-compensated lines was proposed, and characteristics of module differential current under different faults were analyzed. The priniciple is immune to line distributed capacity, series capacitor positions, and presence or absence of MOV breakovers. The validity of this scheme was verified by PSACD simulations.