基于PT-PFM激励阻抗谱数字重构的电缆故障诊断定位

Cable Fault Diagnosis and Location Based on Digital Reconstruction of PT-PFM Excitation Impedance Spectrum

由于传统频谱测试仪器增益带宽积有限,高频区间内输出电压过低,在针对长距离电缆测试时信号衰减较为严重,导致阻抗谱在高频区间内存在一定失真问题。该文提出一种基于伪梯形波激励阻抗谱数字重构算法的电缆故障诊断定位算法。分析不同故障类型下电力电缆的局部故障阻抗对电缆输入阻抗谱的影响规律、首端激励电压信号的衰减特性和不同电压幅值的功率传输特性。设计一种基于Si C高速逆变器的大容量伪梯形励磁系统,用于测量最高频率7 MHz的阻抗谱信息,利用阻抗谱数字重构方法实现0.1 Hz~60 MHz宽频区间的全覆盖。与传统的低压正弦激励相比,采用该时空转换函数的定位结果具有更小的区间振荡和更快的收敛速度。缺陷定位精度提高了80%,验证了该方法的有效性和准确性。

Because the gain bandwidth product of traditional spectrum testing instruments is limited,and the output voltage in the high-frequency range is too low,the signal attenuation is relatively serious when testing long distance cables,which leads to a certain distortion problem in the impedance spectrum in the high-frequency range.This paper proposes a cable fault diagnosis and location algorithm based on the digital reconstruction algorithm of pseudo trapezoidal wave excitation impedance spectrum.The influence of local fault impedance of power cable on cable input impedance spectrum under different fault types is analyzed.The attenuation characteristics of the excitation voltage signal at the head end and the power transmission characteristics of different voltage amplitudes are analyzed.A large capacity pseudo trapezoidal excitation system based on SiC high-speed inverter is designed to measure the impedance spectrum information of the highest frequency 7MHz.The full coverage of 0.1Hz~60MHz wide frequency range is achieved by using the digital reconstruction method of impedance spectrum.Compared with the traditional low voltage sinusoidal excitation,the positioning result using the time-space conversion function has smaller interval oscillation and faster convergence speed.The defect location accuracy is improved by 80%,which verifies the effectiveness and accuracy of this method.