Effect of magnetic compound electrode on space charge injection and accumulation in LDPE

Space charge accumulation is the main factor in accelerating the degradation of polymeric insulation in high-voltage direct current (HVDC) cables. It is essential for the development of HVDC cables to suppress the space charge in the insulating layer. In this paper, an approach is presented to decrease carrier injection from the inner semiconductive layer to the insulating layer, using a magnetic semiconductive compound. The semiconductive shielding compound was prepared by adding strontium ferrite to a carbon black/ethylene-vinyl acetate/low-density polyethylene (LDPE) matrix. The addition of strontium ferrite led to an increase in the residual magnetic induction of the semiconductor shielding layer. Unmagnetized and magnetized semiconductive compounds were used as electrodes to test the injection of carriers into the LDPE insulation layer. When SrFe12O19 had been added, the charge injected into the LDPE by the magnetized semiconductive layer was less than with an unmagnetized semiconductive layer. When the content of SrFe12O19 was 5 wt. %, 10 wt. %, 30 wt. %, and 50 wt. % in the semiconductive compound, the charge in the LDPE was reduced by 4.2%, 8.1%, 12.5%, and 27.1%, respectively.