Location of Cable Joints with Moisture in Medium Voltage Distribution Grid Based on Frequency Domain Reflection Method

• Main Authors: Li, Rong, Zhou, Kai, Wan, Hang, Xie, Min, Liu, Li, Wang, Xianjin
• Format: Conference Proceeding
• Language: English
• Subjects: Blackman window; Capacitance; distribution cable; frequency domain reflection; Frequency-domain analysis; High-voltage techniques; Impedance; intermediate joint location; Moisture; moisture diagnosis; Power cable insulation; Power cables
• ISSN: 2474-3852
• DOI: 10.1109/ICHVE49031.2020.9279543

In order to solve the shortcomings of location for intermediate joints with moisture in distribution cables at present, this paper presents a new method based on frequency domain reflectometry (FDR), which can locate joints and diagnose its dampness. Firstly, the basic principle of the proposed method was clarified, which included the frequency domain reflection theory, the cable impedance discontinuity point positioning principle and the Blackman window function. Then, the change of how the cable capacitance is affected with damp was analyzed. Through the analysis of simulation and experiment, the variation rule of the electrical parameters for those joints was obtained before and after damp. After that, the Blackman window function was selected to eliminate the error caused by spectral leakage in the intermediate joint positioning spectrum. Next, the intermediate joints with different damp degrees were analyzed by using the windowed diagnostic function K_{\text{blackman}}(x) through simulation. Finally, 10 kV XLPE cables with different joint defects were produced in the laboratory, which simulated normal, mild and severe moisture conditions. The effectiveness of the proposed method was verified via the experimental tests and the data analysis. The results indicate that this method can locate and diagnose the intermediate joints with different moisture levels.