不同电压等级四回线双端故障测距原理研究

由于存在互感和故障类型众多,不同电压等级四回线的故障分析和故障测距愈加困难.为此采用六序分量矩阵叠加方法对不同电压等级的四回线进行解耦,可以将阻抗阵转换为一个特殊的对角阵,非对角线上不为零的元素只有2个,表明四回线的同向零序网存在互感,其它的非对角线元素为零,表明四回线的反向正序网之间不存在互感.采用六序分量矩阵叠加方法对四回线系统的2条同杆双回线两端的电流分别进行矩阵变换,得到2组反向正序电流,利用反向正序电压在故障点相等的特点,实现不同电压等级四回线的双端故障测距.该双端故障测距方法不需要考虑不同电压等级同杆双回线的参数归算,测距精度不受故障类型、故障点过渡电阻、系统运行方式的影响.仿真结果表明,该双端故障测距方法具有有效性和实用性

Two-Terminal Fault Location for Four-Circuit Transmission System Composed of Two Double-Circuit Transmission Lines on Same Towers Respectively Belonging to Different Voltage Grades

Due to the existence of mutual inductances and various types of faults,it is more difficult in fault analysis and fault location for four-circuit transmission system composed of two double-circuit transmission lines on same towers respectively belonging to different voltage grades.For this reason,the superposition of two six-sequence component matrices is adopted to decompose the four-circuit transmission lines respectively belonging to two different voltage grades,thus the impedance matrix can be turned into a special diagonal matrix and only two nonzero elements on non-diagonals and this suggests that there is mutual inductance in the synclastic zero-sequence network of the four-circuit transmission system.Applying matrix transformation to currents at both terminals of the two double-circuit transmission lines on same towers in the four-circuit transmission system,two sets of reverse positive sequence currents are attained,then based on the feature that at fault point the reverse positive-sequence voltages calculated from opposite buses are equal,the two-terminal fault location for the four-circuit transmission system can be implemented.It is not needed for the proposed two-terminal fault location method to perform parameter reduction among double-circuit transmission lines on same towers respectively belonging to different voltage grades,and the fault location accuracy is not affected by fault types,transition resistance at fault point and operation modes of power grid.Simulation results show that the proposed fault location method is available and practicable.