Simulation of Space Charge in HVDC Cable under DC Superimposed Operating Impulse Voltage

This research examines the space charge properties of cross-linked polyethylene (XLPE) insulation for HVDC cables under DC superimposed operating impulse voltage. A bipolar charge transport (BCT) model considering impurity dissociation is developed to simulate the evolution of the electric field and charge distribution in XLPE under DC superimposed impulse voltages of different polarities. The results show that there is an obvious polarity effect on the space charge characteristics within the cable insulation when subjected to impulse voltage. Specifically, the application of a homopolar impulse voltage leads to an overall intensification of the electric field within the insulation, facilitating the injection and migration of homopolar charges and culminating in enhanced charge accumulation. Conversely, the application of an opposite polarity impulse voltage triggers a complex electric field reversal process (positive-negative-positive). The reversed electric field will lead to the extraction and recombination of the originally accumulated homopolar charge at the electrodes, resulting in a decrease in the amount of accumulated charge. The space charge characteristics under the superimposed heteropolar impulse voltage become insignificant due to the repeated alternation of the electric field within the insulation.