利用相电流突变防止零序方向元件误动的方法

弱电强磁情况下相邻回线间互感是造成零序方向元件误动的根本原因。文中分析了零序方向元件正确工作的条件,对比了零序方向元件正确动作与误动作情况下该回线电气量的特征差异,得出了误动线路的三相电流具有相同突变的故障特征。在此基础上利用模型误差识别三相电流相同突变特征,提出了一种防止零序方向元件误动的方法。通过PSCAD建立同塔双回线路模型进行仿真验证,仿真结果表明:文中方法能够可靠闭锁相邻回线短路、断线情况下健全线路的零序方向元件,不会闭锁该线路故障情况下的零序方向元件。所述方法具有识别弱电强磁环境下相邻回线互感的能力,提高了零序方向元件的适应性,具有实用价值。

A Method for Preventing Mal-operation of Zero-sequence Direction Component Using Current Fault Component

Mutual inductance between adjacent lines is the root cause of mal-operation of the zero-sequence direction component under weak current and strong magnetic situations. The correct working condition of the zero-sequence direction component is analyzed and the difference in fault characteristics is obtained by comparing the electric quantity of the lines when the zero-sequence direction components are in correct operation and mal-operation. Consequently, the fault characteristic of the line in mal-operation is found that the fault components of the three-phase currents are the same. By identifying this characteristic with the model error algorithm, a method is proposed to prevent the mal-operation of the zero-sequence direction component. To test the effectiveness of the proposed method, a double-circuit transmission system on the same tower is built based on the PSCAD software. Simulation results show that the method is reliable in identifying the healthy line. When a line is under fault, the zero-sequence direction component of adjacent healthy lines can be correctly blocked to avoid mal-operation. In contrast, the zero-sequence direction component of the fault line will be working properly instead of being blocked. The proposed method is capable of identifying mutual inductance between lines under weak current and strong magnetic conditions while improving the applicability of the zero-sequence direction component. This work is supported by Sate Grid Corporation of China.