基于小波包的小电流接地系统故障选线的新判据

分析了故障选线的现状和基于小波包选线方法的优势及不足，提出了一种基于小波包的接地故障选线的新判据：先根据能量最大原则确定暂态电容电流最集中的特征频带，再比较各条线路特征频带的模最大值和零序电压首半波的极性以确定故障线路。该判断过程简单，抗干扰能力强，并且能够在只有2回线路的情况下选出故障线路。仿真结果表明，该判据不受接地条件和接地方式的影响，能够更准确可靠地选出故障线路。

A NEW CRITERION FOR EARTH FAULT LINE SELECTION BASED ON WAVELET PACKETS IN SMALL CURRENT NEUTRAL GROUNDING SYSTEM

This paper analyses the development of fault line selection, the deficiencies and the advantages of the methods based on wavelet packets and presents a new criterion for earth fault line selection based on wavelet packets. Based on the principle of maximum energy,it selects the special frequency band that has the major characteristics of transient capacitance current.Comparing the polarity of the special frequency band of each line with the polarity of the zero sequence voltage's first half wave,it can detect the fault line. The detecting process with this new criterion is simple and more able to decrease the affects of disturbances. Further more, this new criterion is still effective in the case of two lines in power system. Simulation indicates that on condition of various earth faults, the fault line can be selected based on the criterion more reliably.