Comparison of space charge evolution between polypropylene and cross-linked polyethylene under polarity reversal voltage

Isotactic Polypropylene (iPP) is a kind of potential HVDC power cable insulation material for its green property and excellent electrical performance. Dynamic evolution of space charge under polarity reversal voltage is harmful to long term operation of HVDC power cables. The experiment of space charge evolution in XLPE and iPP films during external voltage polarity inverse (from +50 kV/mm to −50 kV/mm) at room temperature was conducted. The results show that the polarity of space charge in the bulk of both XLPE and iPP samples is mainly negative during the whole polarization process. Hetero-charge near the anode was observed in both samples after the poling of positive and negative voltage. iPP samples also present mirror image effect and show a better space charge performance in the the amount of residual space charge and electric field distortion. This study could provide a deeper insight of space charge behavior under polarity reversal voltage in iPP materials.