Effect of Segmented Thermal Aging on Defect Location Accuracy in XLPE Distribution Cables

Abstract

Frequency domain reflectometry (FDR) technologies could be applied to locate defects in cables effectively. Owing to the large space span and complex operating environment of the actual XLPE distribution cables, segmented thermal aging phenomenon occurs easily, causing the nonuniform distribution of electrical parameters along cables, which might affect the defect location accuracy ultimately. In this paper, the segmented thermal aging cable models were established and the effect of segmented-aging in XLPE distribution cables on defect location accuracy was explored based on simulation. It was found the floating range of defect location deviation in segmented thermal aging cable models could reach 10% of the whole cable length, which could not be ignored. Further research and analysis revealed that the defect location deviation in the segmented-aging cable mainly attributes to the differences of distributed wave velocities in the cable. On this basis, a correction coefficient of defect location M was put forward for the segmented-aging cable models established, which has achieved remarkable results. Finally, a segmentedaging cable model with a length of 119 m was built in the laboratory, and the validity for improving defect location accuracy by considering the differences of wave velocities was verified through experiments. Results show the defect location deviation can be reduced from 2.19% to 0.39% by introducing M.

Residual Life Prediction of XLPE Distribution Cables Based on Time-Temperature Superposition Principle by Non-Destructive BIS Measuring on Site

“…It has been proved that the input impedance spectrum of a coaxial cable varies approximately periodically with the signal frequency f [21,22]. At high frequencies (ωC 0 >> G 0 , ωL 0 >> R 0 ), Z 0 is almost a constant; according to Equation ( 14), it could be reasonably deduced that the periodicity of the input impedance spectrum is determined by e −2γl .…”

“…As illustrated in Figure 10, the distribution parameter model could be used to describe the electrical network structure of power cables under a high frequency power source according to the transmission line theory [21]. R 0 , L 0 , G 0 and C 0 represent the equivalent resistance, inductance, conductance and capacitance of the power cable per unit length, respectively, and they can be calculated according to the material, size, structure and other parameters of the power cables.…”

“…Since R 0 and L 0 are almost unchanged if a degradation occurs, G 0 + jwC 0 can be derived from the complex dielectric constant ε(ω). Meanwhile, the complex dielectric constant of XLPE material in the frequency range between 10 kHz and 100 MHz can be fitted according to the Cole-Cole model [21,24], as shown in Equation (18):…”

“…BIS measuring has been developed in recent years, and has become an effective method of recognizing and diagnosing the local degradation in insulation cables [21,22]. The principle of BIS measuring is to measure the input impedance of the cable in a wide frequency range, which is closely related to the distribution of the propagation coefficient and the characteristic impedance of the cable; in other words, BIS measuring contains healthy information about the cable insulation state.…”

Fault Identification and Localization of a Time−Frequency Domain Joint Impedance Spectrum of Cables Based on Deep Belief Networks

“…The FDR method uses a swept sinusoidal signal as the incident signal of the cable and determines whether a local defect occurs in the cable based on the distortion characteristics of the reflected signal spectrum of the cable. In [ 8 , 9 , 10 ], based on the FDR method, swept−frequency signals were used to diagnose cable defects, and the method was more accurate in localization because the signal contained more high−frequency energy, but it failed to identify different types of cable faults. Meanwhile, single domain analysis faces difficulties in diagnosing cable faults and defects, due to the resolution limitation and weak anti−interference capability of reflected signals.…”