基于模极大值理论的配电网接地保护研究

Study of grounding fault protection in distribution system based on the theory of modular maxima

应用小波变换模极大值理论,对故障后的电气量进行分析,反应零序电流的突变情况,根据其在各条线路上的极性和大小的不同变化规律实现故障选线。判据采用做内积的方法,在对含有误差的信号进行处理时具有良好的容错性,因而能够获得更高的选线精度。该方法适用于小接地电流系统的各种中性点运行方式,并且现场安装简单、不需要定值整定。EMTP仿真结果表明,该方法是有效的、可靠的。

In this paper, the method to abtain the modular maxima of wavelet transform is employed to analyze the electrical components after the fault, respond the abrupt change of zero sequence current, and determine the fault line by comparing the change of the zero-sequence currents on all lines′ polarities and magnitudes. With the using of scalar product, the criteria has good property of bearing error and can get higher precision of fault line selection. This method is suitable for various distribution systems with different neutral grounding modes. Moreover, it can be easily used on site without adjusting protective setting. EMTP simulations show that the method is effective and reliable.