Effect of Air Gap Defects on the Electric Field Distribution and Partial Discharge Characteristics of Vehicle-Mounted High-Voltage Cable Terminals

The on-board cable terminal is the main electrical equipment in a moving train set's high-voltage system, and the stability and safety of this equipment are essential preconditions. To study the impact of air gap flaws in on-board cable terminals on insulation performance, this paper builds a model of the air gap between the stress tube and the main insulation of the vehicle cable terminal, investigates the distinctions in the internal electric field distribution of air gaps existing in on-board high-voltage cable terminals, and scrutinizes the impact of air gap size on the internal electric field of terminals. The partial discharge of cable terminals with different lengths of air gap defects was studied, and the partial discharge of air gap cable terminals under different temperature variations was analyzed. The findings indicate that the longer the air gap length, the greater the electric field strength of the cable terminal; with the increase of the air gap thickness, the electric field strength of the cable terminal first increases and then decreases, and when the thickness of air gap inside the cable terminal is 0.1mm, the electric field intensity is the largest, with a value of 9.4x107 V/m. In addition, the larger the air gap defect, the more severe the partial discharge of the cable; The larger the temperature difference, the lower the initial discharge and extinction voltages at the cable terminals, and the higher the average and maximum partial discharge capacity at the cable terminals. The trend is in line with the simulation results.