基于FDR和时频脉冲转换的长电缆缺陷极性识别研究

Research on Defect Polarity Identification of Long Cable Based on FDR and Time-frequency Pulse Conversion

为解决采用频域反射技术进行长电缆缺陷检测时,其结果易受低频段数据缺失占比的影响,而难以判断电缆缺陷极性的问题,该文提出一种基于频域反射技术的电缆阻抗失配点时频脉冲转换算法以实现缺陷的定位和极性判别。首先,采用2阶Nuttall自卷积窗的快速傅里叶计算方法对不同类型的电缆阻抗失配点进行定位。其次,提出电缆阻抗失配点时频脉冲转换算法,利用高斯窄带包络信号良好的频段调节能力和时频特性,详细阐述了时频脉冲的参数设计和极性判断方法。之后,运用仿真,对不同类型的阻抗失配点进行时频脉冲转换,验证了该算法的有效性。最后,采用该算法对实验室含接头长1500m的10k V XLPE电缆进行实验验证。仿真和实验结果表明:时频脉冲转换算法可以有效地定位长电缆阻抗失配点并且实现不同类型阻抗失配点的极性识别;同时,不同长度电缆阻抗失配点的时频脉冲转换结果不受低频段数据缺失占比的影响,有效提高了长电缆阻抗失配点的极性识别率。

It is difficult to identify the polarity of long cable defects by using frequency domain reflection(FDR)technology due to the results that are easily affected by the proportion of missing data in low frequency band.To solve this problem,this paper presents a time-frequency pulse conversion algorithm of cable impedance mismatch points based on FDR to realize defect location and polarity discrimination.First,different types of the impedance mismatch points of the cable are located by using the second-order Nuttall self-convolution window and fast Fourier calculation.Next,the time-frequency pulse conversion algorithm of cable impedance mismatch is proposed.The parameter design and polarity identification method of the time-frequency pulse are described in detail by using the good frequency modulation ability and time-frequency characteristics of the Gaussian narrowband envelope signal.Then,the effectiveness of the time-frequency pulses conversion algorithm is verified by the simulation of different types of impedance mismatch points.Finally,the effectiveness of the proposed algorithm is verified by the experiment of the 10kV XLPE cable with a joint in the laboratory,and the cable length is 1500m.The simulation and experimental results show that the time-frequency pulse conversion algorithm can effectively locate the impedance mismatch points of long cables and realize the polarity identification of different types of impedance mismatch points.At the same time,the time-frequency pulse conversion results of different length cable impedance mismatch points are not affected by the proportion of missing data in low frequency band,and the polarity recognition rates of long cable impedance mismatch points are effectively improved.