Study on the field aging characteristics of composite insulators based on experiment and molecular dynamics simulation

Composite insulators have excellent performance and are more and more widely used in power grid. The performance of composite insulators with different service duration will decline in varying degrees, which could pose a threat to the safe operation of power grid. Multiple composite insulators were collected from the northern region of China after operation to study the effects of electric field strength, pollution level, and service life on aging characteristics. The changes in hydrophobicity, mechanical properties, and material properties of the umbrella shed during aging are obtained through multiple experiments. The mechanism of performance degradation is revealed from the perspective of molecular structure through microscopic test. The molecular dynamics simulation shows the process of molecular bond breaking and morphological changes, revealing the principle of viscoelastic changes. The results reveal that the performance of insulator shed gradually declines with the increase in service life. The hydrophobicity and hardness of high-voltage end shed are similar to that of middle section shed, while other parameters are obviously different, indicating that the electric field can aggravate the aging. FTIR results show that the main chain and hydrophobic side chain of silicone rubber are destroyed. XPS and SEM results show that the crosslinking degree of silicone rubber increases and the porosity increases. The molecular simulation of silicone rubber shows that its morphology gradually changes to tension and its stiffness decreases during bond breaking degradation. The above changes in the microstructure of silicone rubber lead to the decline of insulator performance.