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Aging Evaluation of Composite Insulator with Laser-induced Breakdown Spectroscopy

Silicone rubber composite insulators are widely used in external insulation of power system, but the material will gradually age during service that it will cause conceivable threats in transmission lines. Traditional methods of aging analysis can only be carried on during a power service interruption, consuming a lot of effort and time and requiring a complicated sample preparation process. Laser-induced breakdown spectroscopy (LIBS) has advantages like easy sample preparation, high analyzing speed, and low damage to samples, so it is gradually applied to external insulation detection. Based on LIBS technology, the variation trend of iron element content with depth was obtained, and the thickness of aging layer was calculated accordingly. The aging layer thickness of the sheds of one insulator string on different positions was evaluated. The results indicated that the aging layer of the top surface was thicker than the back, and the aging layer of the root was thicker than the edge on the same surface, the aging condition of sheds on high-voltage and low-voltage side was more serious than those on medium-voltage side, and sheds on the sun-side was more serious than the dark side, too. The conclusion was in accordance with the results of previous research by the traditional microscopic analysis, indicating that with LIBS technology we can characterize the aging condition of silicone rubber materials by the thickness of aging layer, which provides a new method for aging detection of composite insulating materials.