基于CT饱和准确识别的零序方向元件改进方案  

Improved Scheme of Zero-sequence Direction Element Based on Accurate Recognition of CT Saturation

作　　者：刘益青[1] 武凯 徐明阳 唐涛南 LIU Yiqing;WU Kai;XU Mingyang;TANG Taonan(School of Electrical Engineering,University of Jinan,Jinan 250022,Shandong Province,China;Power Dispatching and Control Center of Beijing Electric,Xicheng District,Beijing 100031,China)

机构地区：[1]济南大学自动化与电气工程学院,山东省济南市250022 [2]国网北京电力调度控制中心,北京市西城区100031

出　　处：《电网技术》2021年第10期4161-4171,共11页Power System Technology

基　　金：山东省重点研发计划(2019GGX103014);济南大学科技计划项目(XKY2020)。

摘　　要：零序方向元件广泛应用于输电线路的方向纵联保护和接地距离保护,在输电线路反方向出口故障且伴随电流互感器(current transformer,CT)严重饱和时,零序方向元件会误判为正方向,导致保护失去选择性。为解决这一问题,提出1种改进零序方向元件性能的方案。改进方案首先通过计算Hausdorff距离,确定CT是否进入饱和状态,若确定CT饱和,则继续使用Hausdorff距离值确定CT饱和区范围。然后,在CT处于非饱和区时利用短数据窗算法快速确定零序方向元件判断结果,将该判断结果的输出作为CT饱和区的零序方向元件判断结果直至退出饱和区。利用PSCAD仿真软件,建立220kV双端电源输电线路模型,对零序方向元件改进方案进行了仿真验证。仿真结果显示,在反方向出口伴随CT严重饱和时,所提改进方案能确保零序方向元件不误动,而在CT未发生饱和时,不影响零序方向元件的判断结果。Zero-sequence direction element is widely used in the directional pilot protection and ground distance protection of transmission lines.When a fault occurs in the opposite direction of a transmission line with a seriously saturated current transformer(CT),the zero-sequence direction element may judge it as a positive directional fault incorrectly,which probably results in the mal-operation of directional protection.To solve this problem,a scheme for improving the performance of zero-sequence direction element is proposed.Firstly,the Hausdorff distance algorithm is used to accurately identify the state of CT saturation and the range of linear transition periods.Then,the short-window fast algorithm is launched when CT is unsaturated to obtain the judgment result of the zero-sequence direction element,which will then be remembered until the CT quits the saturation period.A typical simulation model of transmission lines is established in PSCAD to verify the proposed scheme.The simulation results show that the improved scheme can effectively avoid the misjudgment of zero-sequence direction element when a fault occurs in the opposite direction with CT saturation.Meanwhile,the proposed scheme does not affect the judgment result of the existing zero-sequence direction element when CT is unsaturated.

关 键 词：CT饱和 线性传变区 零序方向元件 HAUSDORFF距离 短窗快速算法 

分 类 号：TM721[电气工程—电力系统及自动化]