Ultra‐High‐Speed Non‐Unit Protection and Fault Location for Parallel Transmission Lines Earth Faults

Abstract

This article proposes a powerful ultra-high-speed technique for earth fault distance protection of double-circuit power transmission lines. The proposed technique uses the zero and positive sequence of the current signals. The technique presents a discriminating method based on the appearance of zero sequences, the zero sequence magnitude, and the time arrival instants of zero and positive sequence at the relaying point. The suggested technique consists of three stages. Stage 1; the polarity technique, which is designed to detect and classify faults within the protected zone. Stage 2; the ratio technique, which is designed to identify in which circuit the fault is involved. Stage 3; it is employed to calculate the distance of faults. Extensive numbers of simulations were conducted to test the action of the proposed technique. Results show that the technique provides a speed, secure, and dependable protection technique of double-circuit transmission lines even for remote fault, high resistance fault, and a low inception time fault. They also avoid the unbalanced load-switching effect and the current transformer (CT) saturation problems.