New Method for Short-circuit Fault Analysis on Double-circuit Transmission Line Based on Interconnection of Sequence Networks

A method based on three sequences is proposed for break-conductor fault analysis on double-circuit transmission lines. Considering possible different phenomena of the two circuits in real-world situation,the relationship of the three sequence networks and characteristics of the sequence electrical quantities are studied first. Then combining with the boundary conditions of the disconnected ports,a new approach for calculating the post-fault electric quantities is presented. In order to simplify calculation process and make the characteristics of fault sequence voltages and currents more intuitive,a method of interconnections of sequence networks is presented and drawings of interconnections of sequence networks for typical break conductor fault types are given. The method has a definite physical meaning and is simple in calculation. It can serve as a basic theoretical approach for studying fault transient process and protection action characteristic in open-phase operation state on double-circuit transmission lines.