At full load, pump-turbines operating in generating mode may experience a cylindrical cavitation vortex rope caused by the swirling flow in the draft tube cone. Under certain conditions, this vortex rope initiates both pressure and power oscillations. The hydro-acoustic analysis of a pumped storage plant experiencing such pressure and power oscillation is presented to illustrate the self induced oscillation nature of the observed event. The main physical parameters of the system stability are first introduced using a simplified 1D mathematical model of the full-load vortex rope. Then, a modal analysis of the full hydraulic circuit is performed to determine the stability domain of the plant as a function of the vortex rope parameters. Finally, a full hydro-acoustic SIMSEN model of the plant, validated with existing experimental data, is used to simulate the time sequence of the pressure surge event, and the cause of this pressure surge event is clearly identified.