Influence of direct fluorination on space charge behavior in silicone rubber

High temperature vulcanized (HTV) silicone rubber (SiR), due to its better electrical insulation, elasticity, temperature resistance, is used in cable accessories for high voltage direct current (HVDC) cables. The space charge, formed under DC stress in SiR, would distort the local electric field, and furtherly influence the characteristics of partial discharge and accelerate the insulation aging. Direct fluorination, as a solution to change the chemical component, could alter the electrical properties of the polymer surface layer. This paper focuses on the effect of the fluorination on the space charge accumulation in HTV SiR. In this investigation, the results indicated that the fluorination for 20 min effectively suppressed the space charge injection in SiR. However, excessive fluorination (over 30 min) brought in abundant deep traps, and led to significant amount of space charge accumulation in the bulk of polymer. As a consequence, the appropriate fluorination has a significant effect on the space charge accumulation in HTV SiR and has a potential application for inner insulation in pre-molded accessories of HVDC cable.