Effect of La2Li0.5Co0.5O4 in semiconductive nanocomposites on suppression of space charge injection to the insulating medium for high-voltage direct current cables

Abstract Space charge accumulation in the insulating layers of high-voltage direct current cables is a key factor in the degradation of such cables and limits their operational safety. It is necessary to weaken charge injection to the insulation. The semiconductive shielding layer sandwiched between the conductive core and the insulating layer plays a vital role in preventing carrier injecting into the insulation. In this study, a new method is proposed to suppress charge injection. A certain amount of La2Li0.5Co0.5O4 nanopowder was doped in the semiconductive screen to enhance the internal conductive network and block charge injection in the insulation. The influence of La2Li0.5Co0.5O4 in the nanocomposite on the positive temperature coefficient effect and space charge injection process were explored. The results revealed that the peak resistivity of the specimen containing 5 wt% La2Li0.5Co0.5O4 decreased by 50.5% compared to the composites without La2Li0.5Co0.5O4, and charge quantity in the insulating layer was reduced by 41.2%.