Operation and maintenance of 10kV-550kV GIS gas insulated totally enclosed composite apparatus. Main contents of high-voltage circuit breaker maintenance: high-voltage circuit breaker detection, test and operation diagnosis. High voltage circuit breaker vacuum degree or SF6 gas tightness detection, diagnosis or gas circuit transformation. Infrared imaging detection of SF6 gas leakage of circuit breaker pole. Maintenance of circuit breaker operating mechanism. Switch characteristic test and travel curve analysis. Circuit resistance detection and analysis. Vacuum degree detection of circuit breaker pole. Detection, analysis and treatment of SF6 gas micro water composition. Switch withstand voltage test and partial discharge analysis and treatment.