小电流接地系统单相接地故障选线新方法

为改进小电流接地系统单相接地故障选线方法,结合数字信号处理中的相关分析技术与小波包分解技术,利用db小波包以适当频带宽度分解了这种故障后的暂态零序电流,自适应地选出各条线路上故障能量最大的特征频段。两两相关分析各线路故障特征频段对应小波包分解系数的波形,获得相关矩阵,并求出各线路的综合相关系数,最终给出按接地故障发生可能性大小排列的选线结果。理论分析及大量MATLAB仿真结果表明:该法不受故障条件的影响,可准确、可靠地实现配电网单相接地故障选线,适于中性点不接地或经消弧线圈接地系统。

New Method for Line Fault-detection Under Single-phase-to-earth Fault of Low Current Neutral Grounding Power System

An improved line fault-detection method is proposed in this paper by applying both the wavelet packets technology and the correlation analysis technology of digital signal processing.Firstly,each line's transient zero sequence current,which appears in the low current neutral grounding power system while a single-phase-to-earth fault occurring,is decomposed to obtain the suitable outputs of specific frequency bands.And the characteristic frequency band of each line,of which the transient capacitive current is most concentrated,is chosen adaptively according to the view of maximum energy.Secondly, the correlation analysis between each line's waveform of wavelet packets decomposition coefficient corresponding to its characteristic frequency band is carried out,so as to acquire the correlation matrix and then get each line's integrated correlation coefficient.Finally,the result of line fault-detection is obtained,which is arranged by the size of the probabilities of the grounding fault. The theoretical analysis and MATLAB simulations show that the proposed method can choose the faulty line exactly and reliably under all kinds of fault conditions.This method is suitable for both neutral insulated power networks and Peterson coil earthed power networks.