基于负荷电流补偿的负序方向保护改进算法

Improved Algorithm for Negative Sequence Directional Protection Based on Load Current Compensation

电力系统非全相运行和非全相运行方式下再发生故障的工况,会对负序方向保护的正确动作造成影响。当电压互感器安装于母线侧,非全相运行时,负序方向元件会误动;而非全相运行方式下再发生正向故障时,负序方向元件能正确识别。针对该问题,提出了一种修正的负序方向保护新方案:加入负荷电流补偿来抵消非全相运行时系统中存在的负序电流,使得非全相运行时,负序方向保护能有效不动作,而非全相运行再发生故障时,负序方向保护能有效识别。PSCAD与MATLAB的仿真结果表明,新的保护方案在输电线路非全相运行各种工况下具有很好的实用性。

Working conditions of open-phase operation and open-phase fault operation of the power system may cause impact on correct action of negative sequence directional protection.When voltage transformer（VT）is installed at the bus side and the power system is under open-phase operation condition,mal-operation of negative sequence directional elements will be caused.While it is able to correctly identify negative sequence directional elements during open-phase fault operation.In allusion to these problems,a new kind of modified scheme for negative sequence directional protection is presented which is to add load current compensation to offset negative sequence current in the system under the condition of open-phase operation and ensure effective no-action of negative sequence directional protection.Meanwhile,under the condition of open-phase fault operation,it is able to effectively identify negative sequence protection.Simulation results of PSCAD and MATLAB indicate that the new protection scheme has good practicability under various working conditions of open-phase operation of power transmission lines.