Fault Location Of Specially-structured Transmission Lines With Four-jointed Parallel Line

Four-jointed parallel line is more and more widely used in power system because of its narrow corridors, especially in increasing complex modern power transmission system. It is linked with all kinds of lines to consist of teed line system in complex power transmission system. Teed connecting four-jointed parallel line frequently subjects a variety of technical problems in the view of protection engineering. These problems are mainly due to the mutual coupling between lines and the multiple branch of teed connection, which requires choosing faulted branch before fault location.Two kinds of teed connection for four-parallel transmission lines are presented in this paper. One is 4-1-1 teed connection which consists of one four-jointed parallel line and two single lines. The other is 4-4-1 teed connection which consists of two four-jointed parallel lines and one single line. New accurate fault location algorithms for these two kinds of teed connection are introduced according to the feature of lines, sequence components and parameter modification. Depending on twelve-sequence fault component method, the coupled transmission equations are transformed into decoupled ones. Based on the detailed analysis of peculiar characteristic of teed connection, the differential sequence component measurement, which is one of the twelve-sequence fault components, is used to implement fault location for four-jointed parallel line with a teed connection.The new location algorithm makes full use of the decoupled mode and the teed structure.It is independent of fault type, fault resistance, source impedance and mutual coupling between four jointed parallel lines. The algorithm has been tested by ATP simulations, which indicates that this fault location method obtains high accuracy under various fault conditions.