High-speed relaying scheme for protection of transmission lines in the presence of thyristor-controlled series capacitor

This study presents a new protective scheme for transmission lines which are compensated by thyristor-controlled series capacitor (TCSC). Employing the averages of voltage and current, a new criterion is introduced to discriminate between the forward and reverse faults. The validity of introduced criterion is tested for the inductive and capacitive modes of TCSC. During normal conditions, the averages of voltage and current are almost zero. While, following a short-circuit fault, they change from zero to non-zero values. The concept of fault superimposed components is used to extract the mathematical equations of the proposed scheme. Various case studies are considered to evaluate the performance of the proposed scheme. Computer and experimental simulations approve the efficiency of proposed method in high-speed protection of TCSC-compensated transmission lines.