Effects of radical scavenger on space charge accumulation of PP/ULDPE composites for HVDC cable insulation

In this work, the space charge behavior and breakdown strength of polypropylene (PP)/ultralow density polyethylene (ULDPE) blends and three different radical scavenger modified composites are performed at 30, 60 and 90 °C. The trap distribution in the radical scavenger and the composites are investigated based on quantum chemistry calculation and isothermal discharge current test. The results show that, 0.3 wt% addition of radical scavenger has little effect on the thermal and mechanical property of the composites. The radical scavenger can introduce traps with different energy levels, which has greatly inhibited the space charge accumulation aggravated by the increasing temperature in the PP/ULDPE (PU) blends. Although the overall breakdown strength of the samples decreases with the rise of temperature, the performance of radical scavenger modified composites show the best, which suggests a great correlation with the traps they introduce, the molecular structure and chemical reaction of the additives themselves. The PP/ULDPE blends with 0.3 wt% C944 exhibit great potential for HVDC cable insulation.