Under voltage accelerated protection of single source distribution systems

This paper presents a new technique for accelerated protection of distribution systems with single source configuration. In the technique, a specially designed unbalanced under voltage relay is arranged to trip for faults on the line section from the source direction of the system. The relays on the source side of the line section will detect the system balanced operation condition and accelerated operate to isolate the fault from both ends of the line section. Extensive simulation studies with respect to a typical open ring main system show that the proposed technique is able to increase significantly the speed of response of the conventional time grading based protection scheme.