GPS synchronized current differential protection of mutually coupled line

Mutual coupling effect makes the protection of parallel transmission lines a quite challenging problem. Recent work shows that current differential protection can be a better option for protection of transmission lines due to its selectivity and sensitivity. In this paper we explore a current differential protection scheme for mutually coupled lines considering line charging current. Global Positioning System (GPS) is used for synchronized current and voltage measurements. The differential function is developed using equivalent-π model for transmission line and phase coordinate approach. Simulations are carried out in ATP/EMTP environment on a parallel two terminal transmission system. Results show the superiority of scheme.