同塔四回线路纵向故障对零序方向保护的影响研究

结合同塔四回输电线路的结构特点，针对同一电压等级的有电气联系和无电气联系的同塔四回线路，研究分析了同塔四回线路发生单回线纵向故障时线间互感对零序方向保护的影响，利用网络拓扑的等效变换，计算出了各回线路上零序电压、零序电流的幅值和相角特征。分析表明同塔四回线路单回线路纵向故障时，对于两侧均无电气联系的同塔线路，零序方向保护存在误动的风险，对于两侧均有电气联系的线路，零序方向不会误动。最后通过PSCAD建立同塔四回线路的模型，对单相断线纵向故障进行了仿真，仿真结果验证了理论分析的正确性。

Influence research of longitudinal fault on zero sequence direction protection for four parallel transmission lines on the same tower

Based on the structural characteristics of the four circuit transmission lines on the same tower and the lines with/without electrical connection on the same voltage level, this paper analyzes the influence of the mutual inductance between the lines on zero-sequence directional protection when single line longitudinal fault occurs on four circuit transmission lines on the same tower, and calculates the amplitude and phase angle characteristics of zero sequence voltage and current on each line by using the equivalent transformation of the network topology. The analysis indicates that when the single line longitudinal fault occurs on four circuits on the same tower, there is a risk of mal-operation of zero sequence directional protection for the line without electrical connection on both sides; for the line with electrical connection on both sides, the zero sequence direction will not mal trip. Finally through the PSCAD, the model of four circuits on the same tower is established and the single-phase line break is simulated. Simulation results verify the correctness of the theoretical analysis.