Influence of Vacuum Evacuation on Electrical Tree Initiation in Silicone Rubber

The usage of silicone rubber is increasing for insulating material of power cable joint in recent years, although ethylene propylene rubber has been used for that purpose. In this paper, we will report the influence of vacuum evacuation on electrical tree initiation in silicone rubber. The electrical tree initiation voltage of silicone rubber increases after vacuum evacuation. However, when air is impregnated again, the electrical tree initiation voltage decreases with time. Finally, the electrical tree initiation voltage goes down nearly to the same value as the original one without vacuum evacuation. This tendency is observed in silicone rubber with secondary cross-linking treatment as well as in sample without secondary cross-linking treatment.