Development of three zone quadrilateral adaptive distance relay for the protection of parallel transmission line

This paper describes the development of adaptive distance relay for the protection of parallel transmission line with mutual coupling. The quadrilateral trip characteristic with directionality feature is developed for three zone protection. The relay automatically adjusts its operation based on the availability of the input signals. Zero sequence current, if available from the parallel transmission line, is used to fully compensate the mutual coupling effect. When the parallel line´s zero sequence current is not available, the line operating status is used to select the proper zero sequence current compensation factor in impedance calculation. If both the signals mentioned above are not available, default compensation factor is used. The performance of adaptive relay is tested through steady state and dynamic test. The comparative evaluation of test results presented shows the efficacy of the proposed adaptive distance relay over the conventional distance relay.