Collaborative study on vibration modes and stability of key components of hydropower units based on multi-physical field joint test

Abstract

In recent years, the gradual molding of new power systems has required hydroelectric units to assume more grid regulation tasks. Consequently, these units frequently traverse vibration zones, leading to severe blade cracking that compromises safe power production. Based on actual blade cracking faults in a power plant, this study conducts joint field experimental research focusing on the stability of hydropower units and the vibration modes of runners and blades. Vibration modal parameters and unit stability data under various working conditions were acquired through hammering and stability tests. The results demonstrate that mass imbalance is a primary factor affecting unit stability, with minor differences observed in the intrinsic frequency distribution among different blades. Under small load conditions, the vibration frequency at multiple measurement points approaches half of the blades' multi-order intrinsic frequency, potentially triggering sub-harmonic resonance. Furthermore, the fourth to sixth-order intrinsic frequencies of the runner are similar to the intrinsic frequency, increasing the risk of high-order resonance. To mitigate these issues, recommendations including dynamic balancing tests, optimized operation strategies, and periodic inspections of component connections are proposed. Ultimately, this research provides crucial data and a theoretical foundation for the safe operation, optimal design, and future investigation of hydropower units, significantly promoting the sustainable development of the hydropower industry.