Diagnosis and Location of Cable Defects Based on Digital Reconstruction of Impedance Spectrum Under Pseudotrapezoidal PFM Excitation
Ji Liu, Shouming Wang, Haiyue Zhang, Mingze Zhang, Wei Sun
Abstract
Because the output voltage of the existing high-frequency instrument for the defect detection of long-scale transmission cable is too low, it is necessary to output both high-frequency and high-voltage excitation. A diagnosis and location method of cable defects based on pseudotrapezoidal pulse frequency modulation excitation and impedance spectrum digital reconstruction is proposed. A high-capacity pseudotrapezoidal excitation system based on SiC high-speed inverter is designed to measure the impedance spectrum up to the highest frequency of 7 MHz. Through digital reconstruction, the impedance spectrum with different cable defects can be obtained by the bandwidth extension within the range of 100 kHz–63 MHz. Compared with traditional low-voltage sinusoidal excitation, the location results using the proposed time-space conversion function have a more minor interval oscillation and a faster convergence speed. The accuracy of defect location is improved by 80%, which verifies the effectiveness and accuracy of the proposed method.