Reliable and Economical Scheme to Improve Protection and Stability of Heavily Loaded Double Circuit Transmission Lines Using Series Compensation

Tripping of one circuit of a heavily loaded doublecircuit transmission line may lead to tripping of the healthy circuit due to an out-of-step condition. Out of step is resulted by overloading of the healthy circuit. In this paper, a reliable and economical scheme of using series capacitors is proposed to avoid tripping of healthy circuit. Series Capacitors improve the power transfer capability of the remaining circuit by inserting a capacitor in series with the healthy circuit at the same instant of tripping faulted circuit. The insertion of series capacitors SCs improves system stability and prevents system blackouts, but in other hand affects the transient performance of distance relays. Then Elliptical characteristics are proposed to reduce the effects of SCs on distance relays.