磁通密度特征分析与CT饱和区识别及重构技术

Magnetic Flux Density Feature Analysis and CT Saturation Region Recognition and Reconstruction Technology

为解决电流互感器饱和引起的继电保护问题,提出了一种基于磁通密度特征的电流互感器(current transformer,CT)饱和识别方法,以及畸变区二次电流重构技术。首先以饱和时磁通密度梯形区域特征为基础,对CT饱和进行识别,进而利用磁通方差的斜率在进入饱和与退出饱和的差异构建饱和判据,并计算二次电流饱和起点和终点对应的时间,以此得到CT饱和区。然后以电网负荷最大时的电流为依据构建保护启动判据,避免保护误动。最后利用最小二乘法对饱和区二次电流进行重构,可靠反映系统一次电流。基于PSCAD/EMTDC软件的仿真验证表明,所提方法准确可靠,能快速有效识别CT饱和区段,且时间误差不超过1 ms。

To solve the problem of relay protection caused by CT saturation,a CT saturation identification method is proposed based on flux density characteristics and secondary current reconstruction technology in the distortion area.The CT saturation is identified based on the characteristics of the magnetic flux density trapezoidal region at saturation.Then the saturation region of CT is obtained using the slope of the flux variance to construct the saturation criterion based on the difference between entry saturation and exit saturation and calculate the time corresponding to the start and end point of secondary current saturation.The protection starting criterion is constructed based on the current at the maximum grid load to avoid protection misoperation.Finally,the least square method is used to reconstruct the secondary current in the saturation region to reflect the primary current reliably.The simulation results based on PSCAD/EMTDC software show that the proposed method is accurate and reliable,and can quickly and effectively identify the saturated CT segment with a time error of less than 1 ms.