Surface discharge detection of external insulation of outdoor vacuum circuit breaker based on ultraviolet imaging

Post insulator is one important part of outdoor vacuum circuit breaker's insulation, and surface discharge of post insulator is a main cause of outdoor vacuum circuit breaker insulation faults. A new method is introduced to detect surface discharge, using ultraviolet imaging technology. The images of post insulator's surface discharge are captured with ultraviolet imager. Meanwhile its discharge quantity is measured. After image process of ultraviolet imaging video, three feature parameters are found to indicate surface discharge intensity, which are mean facula area, intermittent facula area and repetition times of intermittent facula. Meanwhile the relationship between the three feature parameters and partial discharge quantity is studied by method of least square support vector machine. It demonstrates that under certain voltage and weather condition, discharge quantity can be calculated with the three feature parameters. A power frequency withstand voltage test system is built to test outdoor vacuum circuit breaker under various climatic conditions. The experiments demonstrate that discharge quantity diagnosed by UV image only have an error less than 6% compared with the discharge quantity measured by PD detector, which provides a useful method of external insulation fault diagnosis of outdoor vacuum circuit breaker based on ultraviolet imaging.