Simulation of AC Space Charge in XLPE under Needle-Plate Electrode

The charge transport process under AC is the key to understanding the mechanism of electrical tree initiation. This work established a bipolar charge transport model with the needle-plate electrode under AC to simulate the space charge distribution in cross-linked polyethylene (XLPE). Space charges of different voltage amplitude, temperature and AC cycles were obtained. The result indicates that the electric field strength at the needle tip is the largest under the needle-plate electrode and the space charge is concentrated near the needle tip. Besides, a small amount of charge exists at the end of an AC cycle, which proves that the charge injection and extraction process is asymmetric. The amplitude of AC voltage and temperature affect the depth of space charge injection, and the effect of voltage amplitude is more obvious. Moreover, the space charge density increases and distorts the electric field at the needle tip after multiple AC cycles, which may be related to the polarity of the charges.