Abstract: For a large hydropower station, technical challenges emerge in estimating high energy consumption or regulating the thermal environment in the ventilation system of its underground cavern groups. Aiming at these difficulties, we conduct a one-year continuous field monitoring campaign at Xiangjiaba Hydropower Station hydropower plant. This paper focuses on a comprehensive analysis and reveals the spatial and temporal distribution characteristics of temperature field in its main powerhouse, cable tunnels, and other key caverns. We identify the key influencing factors－equipment heat dissipation, ventilation operation mode, external environment, and geological conditions, and prove the most effective control measure can be implemented through regulating the ventilation operation mode. Then comprehensive optimization strategies are worked out, including stratified air supply, localized enhanced ventilation, and demand-based dynamic air volume regulation. Engineering application demonstrates that after optimization, average temperature in the main powerhouse decreases by 4.2%, and the overall energy consumption of the ventilation system is reduced by 15.1%, meeting the dual objectives of thermal environment improvement and energy saving. This study achieves a data-driven approach to optimizing ventilation in underground cavern groups, useful for the design and efficient operation of similar projects.

Key words: underground cavern group, temperature field, ventilation optimization, energy saving and consumption reduction, long-term monitoring