Identification of localized moisture defects in power cables based on frequency domain reflection coefficient spectra method

Abstract

Based on the frequency domain reflection method, this paper studies the reflection coefficient spectrum characteristics of the head-end of the cable. The vector network analyzer is used to obtain the logarithmic amplitude, linear amplitude, and phase spectrum of the normal cable and the local heat aging cable. By comparing the reflection coefficient spectrum of the cable with/without the fault, the typical characteristics of the cable with local dampness defect are obtained. The experimental results show that: within 1 MHz-100 MHz, the logarithmic amplitude and linear amplitude of the reflection coefficient spectrum increase with the time of dampness. The frequency and amplitude of the first trough show a decreasing trend. The number of positive peaks of the phase waveform of the damped cable is smaller than the normal cable. The test results show that: within 1 MHz-100 MHz, the logarithmic amplitude and linear amplitude increase with the increase of the moisture time. The frequency and amplitude of the first trough of the reflection coefficient spectrum of the logarithmic amplitude and linear amplitude show a decreasing trend. The number of positive peaks in the phase waveform of the cable after the moisture is less than that of the normal cable, and the period of the waveform becomes larger. The results can provide a reference for the detection and identification of localized moisture defects in cables.