Micro characterization of aged liquid silicone rubber used for 220kV current transformer jacket

In recent years, some composite hollow core insulators of current transformers used in China Ningxia Power Grid have showed different levels of degradation and cracking phenomena, especially electrical tracking and erosion. After 10 years operation in a quite dry area, the liquid silicone rubber kept a good state of hydrophobicity and hardness. It seemed the transformer jacket erosion phenomenon cannot be explained by conventional flashover theoretical model. In this paper, some tests and experiments, including SEM, FTIR and TGA analysis, XPS analysis, have been done on the aged silicone rubber. The results of SEM analysis showed the microgram of the aged surface. The FTIR results showed that only the erosion parts of sheds have changed a lot in the organic functional groups. The TGA results could distinguish the severity of the material aging. From the XPS results, the main elements of the specimen showed little changed. It is found that the low-voltage sheds suffer from more serious degradation than the other sheds. Also, it is found that the structure and functional groups of the aged surface have changed a lot, which may lead to the degradation of tracking and erosion performance. Compared to the macroscopic properties, it´s easier and earlier for micro structure characterization to track dielectric materials signs of aging.