Book excerpt: This brief provides a comprehensive introduction on the flow-induced instabilities (e.g., the pressure fluctuations and the vibrations) of the reversible pump turbines (RPTs) in the pumped hydro energy storage power stations (PHSEPSs) in China based on long-term field tests. The pressure fluctuations and the vibrations of several RPTs in China under different operational conditions are analysed in detail to reveal their generation mechanisms and propagation characteristics. The book presents advanced signal analysis and processing methods which are used for obtaining the time-frequency information and for finding the internal correlations between several types of signals. Advanced artificial intelligence algorithms are adopted for understanding the effective fault diagnosis and the identification of different flow patterns. The book overviews the fundamentals of the RPTs and the signal analysis methods, while it demonstrates that the analysis results of the pressure fluctuation and vibration data may be employed for the calibration of numerical simulations and the comparisons of model tests. It is primarily targeted to researchers and engineers working on the fields of condition monitoring and fault diagnosis of hydraulic machineries.