数字化行波选线方法与行波分析所选的时间窗宽度、频带范围密切相关,时频窗的选择在一定程度上决定了行波选线的性能。提出一种利用自适应时频窗的高可靠性行波选线新方法。该方法利用线路零模电流行波两两之间的交叉小波变换(cross wavelet transform,XWT),自适应求取出零模电流行波相关性较强的时频窗,作为行波选线的时频窗,同时计算出零模电流行波在该时频窗内的相位差。最后通过自适应时频窗内的零模电流二进小波变换模极大值进行选线,确定故障线路。所提方法充分结合了复小波变换在频带分析方面的优势和实小波变换在突变检测方面的优势。理论分析与仿真结果表明,所提方法选线可靠性高,交叉小波变换应用合理,且不受中性点接地方式、线路结构等因素的影响。
Digital traveling wave based fault feeder selection is closely related to analyzed time span and frequency band. The selection of time-frequency window determines the performance of fault feeder selection algorithm. A novel traveling wave based fault line selection method was proposed, which is based on adaptive time-frequency window. The cross wavelet transform(XWT) between zero mode currents of two feeders were calculated, and the time-frequency window with higher relativity were extracted. The phases between zero mode currents were also obtained by XWT. The faulted feeder was identified in the adaptive time-frequency window by comparison of dyadic wavelet maxima of feeders' zero mode currents. The proposed method combines the advantages of complex wavelet for frequency band analysis and the real wavelet for singularity identification. Theoretical analysis and simulation results prove that the proposed method has high reliability. The application of XWT is reasonable. The performance of the proposed method is not affected by the neutral point grounding type, and feeder structure, etc.