Evolution Process and Characteristics of Medium Voltage Cable Joints' Incipient Faults in Humid Environment

For lack of research on the evolution process of incipient cable joint faults at present, this paper designed simulation experiments for incipient cable joint fault in wet environment according to the actual operation scenario, obtained the characteristics of the change law of incipient cable joint fault current, insulation damage, water displacement in the air gap and so on under different discharge times, and analyzed the evolution process of incipient fault. According to the electrode composition characteristics, the incipient fault is divided into the first stage and the second stage, and the respective characteristics of the two stages are proposed. On this basis, an early fault simulation model was established when the arc position was fixed. Moreover, the changes in arc temperature, the formation of high-temperature areas in the solid insulation part, and the heat dissipation in the arc area are simulated and analyzed. Based on the experimental and simulation results, the moving position arc and reignition arc constitute the first stage of incipient fault. When the arc position is near the joint ground point, the incipient fault will enter the second stage. When the flashover marks transfix the insulation surface, a permanent fault will be formed. The results of this paper provide theoretical supports for incipient fault feature recognition and monitoring.