A condition-based monitoring strategy to extend the lifetime of a generator with stator ovalization

The authors present a detailed investigation of anomalous and critical vibrational behaviour observed in a 200 MW Kaplan unit. The study used a multi-technique analytical approach, including vibration analysis, orbit monitoring, frequency spectrum evaluation, oil analysis, and temperature trends to diagnose complex faults and assess critical risks accurately. The findings identified the root cause of high vibrations as a structural-electromechanical problem caused by stator ovalization leading to unbalanced magnetic pull (UMP), rather than a simple mass unbalance. Recommendations include immediate enhanced monitoring, new clearance, air gap sensors, and corrective repairs in the stator and bearing. The case study highlights the importance of integrated condition monitoring for generator reliability.