Online Monitoring Technology for Vacuum Degree of Vacuum Circuit Breakers Based on Fiber-Optical Laser-Induced Breakdown Spectroscopy

As a major switching device in today's power systems, vacuum circuit breakers have a utilization rate of 95% in the medium voltage field. However, the lack of reliable online vacuum detection methods hampers their daily operation and expansion to higher voltage levels. This study proposes an online vacuum detection method for vacuum circuit breakers based on Fiber Optic Laser-induced Breakdown Spectroscopy (FO-LIBS), integrating a single fiber optic structure with LIBS technology. This method addresses the shortcomings of traditional LIBS systems, such as flexibility and cumbersome on-site operation, thereby better protecting the detection and analysis equipment. Experimental results demonstrate the stability of laser energy in the fiber optic laser coupling system and confirm the feasibility of laser excitation and plasma light collection through fiber optic transmission. Comparison of ablation pit morphology confirms that FO-LIBS is more suitable for applications requiring minimal damage compared to traditional LIBS. Spectral lines of copper and hydrogen elements were collected at 10 different pressures ranging from 10^-4 Pa to 10⁵ Pa, and the trends of spectra with pressure variation were investigated. Then, employing Support Vector Machine (SVM) algorithm as a classification algorithm achieved an accuracy rate of 97.8%. Our attention was directed towards the classification accuracy at low vacuum levels using visualized confusion matrices and ROC curves. The results demonstrate that this method is operationally simple, with flexible laser transmission, making it more suitable for application in extreme field environments. It can be considered a novel approach for online monitoring of vacuum levels in vacuum circuit breakers.