Study on Space Charge Characteristics of XLPE at Different Temperature Gradients

As the main insulation material of DC cable, the insulation performance of crosslinked polyethylene(XLPE) directly affects the safety of cable operation, and the existence of space charge will lead to the distortion of field strength. Due to the temperature difference between the inner and outer layers of XLPE cables during operation, few studies have reported the effect of temperature gradient on the space charge distribution. Therefore, this paper establishes a two-dimensional model of the DC XLPE cable by means of numerical simulation, couples the temperature-electrostatic-charge multi-physical fields, simulating the space charge distribution based on the bipolar carrier transport (BCT) model, and considering the influence of temperature gradient on the results. In this paper, the charge distribution at the temperature gradient of 0 K and 15 K in the inner and outer layers of XLPE is studied. The results show that under different temperature gradients, the significant changes of charge mobility and charge rate injected from the electrodes result in a great difference in the charge distribution characteristics. The charge migration velocity on the side with higher temperature is faster than the charge injection depth on the side with lower temperature. The higher the temperature gradient, the greater the distortion rate of the field strength, so the more likely the insulation failure of the cable will occur.