An Analysis of Long-Term Operation and Maintenance Characteristics of Air-Cooled and Evaporative-Cooled Hydrogenerators at Lijiaxia Hydropower Station

With China’s increasing integration of variable renewable energy into power grids, conventional hydropower units are progressively assigned critical grid-stabilizing functions— such as peak shaving, frequency regulation, and contingency reserve—due to their broad output adjustment range and rapid response capability. Under frequent load regulation, hydrogenerators experience cyclic variations in internal electromagnetic forces, thermal stresses, and mechanical stresses. The cumulative fatigue effect induces significant deviations in long-term structural reliability compared to units operating under steady base loads. This paper statistically analyzes over twenty years of operational and maintenance data from aircooled and evaporative-cooled hydrogenerators at Lijiaxia Hydropower Station, a…