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中文摘要：
配电网缆-线混合线路发生单相接地故障时，对故障前后各1／4周期内的暂态零序电流进行形态滤波预处理。选取任一线路的暂态零序电流，应用希尔伯特变换（HHT）检测其初始行波波头到达时刻，由此精确确定故障发生时刻。利用经验模态分解（EMD）对滤波后的各线路零序电流进行分解，得到各线路零序电流的最高频固有模态函数（IMF）分量，根据故障线路与健全线路暂态零序电流的最高频IMF分量在故障时刻的一阶差分极性相反的原理，比较各线路暂态零序电流在故障时刻的一阶差分极性，藉此形成选线判据。EMD具有唯一性，又能在时域和频域同时具有良好的局部化性质，分析结果在时频分辨率上具有很高的精度。该方法可以避开电流互感器饱和引起的间断角以及倒相对选线准确性的影响，对于缆-线混合线路、电缆线路和纯架空线路，该方法均适用。
英文摘要：
The transient zero sequence current within 1/4 cycle before and after the fault is pretreated with morphological filtering when single-phase grounding fault occurs in distribution network with hybrid lines. Select arbitrarily the transient zero sequence current of a line and detect the arrival instant of its initial traveling wave front applying HHT（Hilbert-Huang Transform）, base on which the fault occurrence time is precisely determined. The filtered zero sequence current of each line is decomposed with EMD to get its IMF （Intrinsic Mode Function） component with the highest frequency. As the first order differential polarity of IMF component of faulty line is opposite to that of normal line at fault occurrence instant, the faulty line is hence selected properly. EMD decomposition is unique and has good localized characteristic, not only in time domain but also in frequency domain, the analytic results of which have very high time-frequency resolution and accuracy. The influence of CT saturation and phase inversion are avoided. The proposed method is suitable for the distribution network with hybrid lines or unitary lines.
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