基于改进时频域反射法的电力电缆局部缺陷定位

Power Cable Defects Location Based on Improved Time-frequency Domain Reflectometry

电力电缆已广泛运用于城市配电网系统中,电缆缺陷定位也成为众多学者关注的问题。针对传统时频域反射法(time-frequency domain reflectometry,TFDR)存在的交叉项干扰等问题,该文提出一种改进时频域反射法。通过选取特定的可调频参考信号,对反射信号求取维格纳分布(Wigner-Ville distribution,WVD)以分析时频特性。但该时频分布存在交叉项干扰,因此,提出一种新的交叉项抑制方法。通过分析信号时频分布自项与交叉项的特征差异,利用仿射变换(affine transformation,AT)等信号处理手段在不影响信号分辨率的同时消除交叉项干扰,再利用信号的时频互相关函数对缺陷进行精确定位。该文针对10kV交联聚乙烯(cross-linked polyethylene,XLPE)电缆进行仿真分析,并将含缺陷的105mXLPE电缆和含接头的500mXLPE电缆进行实验。仿真及实验结果表明:所提方法定位准确性优于传统方法,具有较好的鲁棒性。

Power cables have been widely used in urban power distribution systems,and cable defects location has become a problem of concern to many scholars.For the traditional time-frequency domain reflectometry(TFDR)there are cross-term interference and other issues.This paper proposed an improved time-frequency domain reflectometry.The method selected a specific linear frequency modulation(LFM)reference signal and obtained a Wigner-Ville distribution(WVD)of the reflected signal to analyze the time-frequency characteristics.However,there was cross-item interference in the WVD,so a new cross-item suppression method was proposed in this paper.By analyzing the characteristic differences between the self-item and cross-item of the signal time-frequency distribution,the cross-item interference was eliminated without affecting the signal resolution by affine transformation(AT)and other signal processing methods,and the defects location were precisely determined by the time-frequency cross-correlation function of the signal.In this paper,the 10 kV cross-linked polyethylene(XLPE)cable was simulated and analyzed,and the 105 m XLPE cable with defects and the 500 m XLPE cable with joints were experimented.The simulation and experimental results show that the proposed method is more accurate than the conventional method and has better robustness.