Electrical Tree Degradation of Silicone Rubber Considering the Effects of Solution Conditions

In addition to electrothermal stresses, cable systems face significant degradation from environmental factors like moisture and nitric acid during long‐term operation. This study systematically examines how long‐term immersion (1000 h) in deionized water and 0.1 mol/L nitric acid influences the electrical performance of silicone rubber (SiR) used in cable accessories, focusing on AC electrical treeing characteristics and space charge behavior. The results reveal a clear dichotomy: water immersion raises the tree initiation voltage, slows tree growth, and induces homo‐charge accumulation, whereas nitric acid immersion lowers the initiation voltage, accelerates tree growth, and promotes hetero‐charge accumulation. Molecular modeling and orbital‐energy calculations for three aging states further clarify the role of different immersion treatments in tree initiation. Supported by physicochemical characterization, we demonstrate that nitric acid causes oxidative degradation of the SiR network, increasing the density of physical weak regions and fostering the growth of pine‐branch‐like trees with distinct main channels. Notably, moisture incorporation is found to counterintuitively enhance certain tree‐resistance properties of the silicone rubber, offering fresh insight for material design in humid environments.