Simulation of Space Charge Distribution in the Insulator Under Negative DC Voltage and Its Impact on Ice Flashover Voltage

Abstract

Space charges can reduce the flashover voltage of the insulators and adversely affect their normal operation. However, the research on space charges in the field of iced insulators remains scarce. This study took the FXBW-35/70 composite insulator as the research object, and a space charge distribution equation on the insulator surface under dc negative polarity voltage was derived. A 3-D simulation model was constructed to analyze the impacts of different voltage application time and voltage levels on electric field and space charge accumulation characteristics. The findings were further validated through natural icing experiments. The simulation results indicate that under negative dc voltage, negative charges predominantly accumulate on the lower surface of insulator sheds, while positive charges mainly gather on the upper surface. Space charge density initially increases rapidly and then approaches saturation as voltage application time extends, and it rises significantly with an increase in voltage level. The corresponding maximums of space charge densities are 5.46 and 9.1 mC/m³, respectively. Moreover, the influence of voltage level on space charge and water droplet trajectory is stronger than that of voltage application time. The accumulation of space charges exacerbates electric field distortion, elevating the maximum electric field strength of the insulator. Under the combined effects of applied voltage and space charges, a new discharge channel forms, ultimately leading to the extinction of the original arc. The flashover voltage of iced insulators exhibits a negative correlation with both voltage application time and voltage level. Based on this relationship, a multivariate fitting model for flashover voltage has been developed, with an average error of 7.3%. The space charge distribution is derived from simulation and validated indirectly through flashover experiments.