单电源多级串供型输电线路距离保护误动原因分析及改进

结合一起单电源多级串供型输电线路距离保护误动的事例,详细探讨了保护误动的原因,分析指出:输电线路在保护安装处近区发生区外单相接地故障时,由于分布电容的影响,判断故障方向的负序方向元件将落入正向区内,引起保护误动.为解决上述问题,在传统负序方向元件判据的基础上提出了一种基于正序电流和负序电流之间相位关系的故障方向判据,并...

Analysis and improvement of mal-operation in distance protection of multi-stage series transmission line with single power source

Based on a case of mal-operation in distance protection of multi-stage series transmission line with single power source, the cause of mal-operation of protection are discussed in detail, which points out: when the external single-phase grounding fault near protection installation location of the transmission line, due to the influence of distributed capacitance, the negative-sequence direction component judging the fault direction will fall into the forward zone, causing the mal-operation of protection. In order to solve the above problems, a fault direction criterion based on the phase relation between positive-sequence current and negative-sequence current is proposed based on the traditional criterion of negative-sequence direction component, and the action interval of positive direction is given. The PSCAD/EMTDC simulation verifies that the proposed direction criterion is not affected by the transition resistance, and solves the problem of mal-operation of the distance protection when the external fault occurs near protection installation location.