基于反射系数傅里叶逆变换的电缆局部缺陷诊断方法研究

Research on Diagnostic Method of Cable Local Defects Based on Inverse Fourier Transform of Reflection Coefficient

为了及时发现电缆中存在的潜伏性缺陷,研究一种基于反射系数傅里叶逆变换的电缆局部缺陷诊断方法。首先根据传输线理论建立电缆计算模型,然后采用快速傅里叶逆变换(IFFT)将电缆首端反射系数谱转换到空间域,最后利用缺陷定位诊断函数DF(x)实现电缆局部缺陷的定位和诊断。针对存在典型局部缺陷的10 kV交联聚乙烯(XLPE)电缆仿真分析,当选取适当的测试频率和测试点数,缺陷定位误差最低可达0.01%。定位曲线中缺陷对应的DF(x)幅值受分布参数的影响,与电容变化的程度线性相关;缺陷长度在一定范围内,DF(x)幅值与缺陷长度成正比;随着缺陷到电缆首端距离的增加,DF(x)幅值成指数衰减;此外,电缆上多处缺陷的诊断结果相互独立。结果表明,该方法具有良好的灵敏度和精确性。

This paper presents a cable local defect diagnosis method based on Fourier transform of reflection coefficient,which is used to detect the latent defects in the cable in time.First,the cable calculation model is established based on the transmission line theory,and then the front end reflection coefficient spectrum of the cable is transformed to the spatial domain by using the inverse fast Fourier transform(IFFT),and the diagnosis function DF(x)is used to diagnose the local defects of the cable.For the simulation analysis of 10 kV XLPE cable with typical local defects,when the appropriate test frequency and number of points are selected,the minimum defect location error can reach 0.01%.The amplitude of DF(x)corresponding to the defect in the positioning curve is affected by the distribution parameter and is linearly related to the degree of capacitance change.Within a certain range of defect length,DF(x)amplitude is proportional to the defect length.and as the distance from the defect to the cable head increases,the amplitude of DF(x)decays exponentially.In addition,the diagnosis results of several defects on the cable are independent of each other.The results show that the method has good sensitivity and accuracy.