EMD及其能量变化曲线在小电流接地系统故障选线中的应用

Application of EMD and energy curve to fault line detection in un-effectively grounded system

当谐振接地系统发生单相接地故障后,所有馈线零序电流的暂态信号中包含大量的特性复杂的非平稳、非线性信号,在此基础上提出一种基于经验模态分解(empirical mode decomposition,EMD)和其能量变化曲线的单相接地故障选线方法。EMD方法的优势在于其强大的适应性,能通过信号自身的变化规律来对其进行分解;而能量曲线能够比幅值更好的对故障线路和非故障线路进行鉴别。首先对各条故障线路的零序电流进行EMD处理,然后取其一阶本征模态函数(Intrinsic Mode Function,IMF)并求其能量曲线,最后根据所构建的选线信心度的大小来进行故障选线。仿真与实验的结果证明了该方法有较高的可靠性与实用性。

Aiming at the characteristics of the un-effectively grounded systems that the zero-sequence current is nonstationary and nonlinear,a new fault line detection method based on empirical mode decomposition（ EMD） and energy curve was proposed in this paper. The advantage of the EMD is its great adaptability,because EMD can decompose the signal according to the change regulation of the signals itself; the energy curve is better than the amplitude at the discrimination of the fault line and non-fault lines. Firstly,each of the zero-sequence current of fault lines was EMD treatment; then we can get the first-order intrinsic mode function（ IMF） and its energy curve; finally,the fault line detection can be done by the phase of the first-order IMF and the size of the energy. The results of the simulation and experiment results indicated that the method is reliable and practical.