Effect of Harmonic Superimposed DC Voltage on Electrical Tree Characteristics in XLPE

As the insulation material of HTS DC cable, cross-linked polyethylene (XLPE) will meet the dual effects of low temperature and the harmonic superimposed DC voltage during its operation, which will change the aging process of XLPE. To solve this problem and to provide the theoretical basis for the design of HTS cable, electrical treeing process under harmonic superimposed DC voltage at 30 and -196 °C were investigated in this study. Results revealed that the treeing process under harmonic superimposed DC voltage has polarity effects, that positive DC bias voltage is easier to initial electrical tree than negative DC bias voltage. Although low temperature slows down the electrical treeing process, we still should pay more attention to the third harmonic in the daily operation of HTS cables.