A Hybrid Time Domain Protection Scheme for Series Compensated Lines

In this paper, a hybrid time-domain protection scheme for series compensated lines using incremental quantity combined with traveling wave principle is proposed. Each principle is assigned a zone of the protected section of the line to achieve fast protection. The incremental quantity-based method is assigned for close-in faults up to 35% and the traveling wave from 33.33% to 66.67% of the line from the relay end. The incremental quantity-based method compares a dynamic restraining quantity obtained from voltage and current to the operating quantity using current for the protection decision. The traveling wave-based method derives a decision by comparing the calculated line length, obtained using the first three arrival times measured at the relay location, to the actual line length. The proposed hybrid approach exploits the advantages of both principles to achieve better reliability and speed of protection for series compensated transmission lines. The proposed scheme is verified for a 400-kV, 300 km series compensated transmission line and results are compared with traditional impedance and incremental quantity-based methods.