Evolutions of guide vane moment of a pump-turbine during runaway transient process after pump trip

The collision of guide vanes with runner of a pump-turbine during transient processes is rarely seen in pumped-storage power stations, but the consequence is serous when happens. To investigate the reason of a case of such an accident, we analyse the evolution rules of guide vane moment during the runaway transient process after a pump trip of a prototype pumped-storage system by using 1D-3D method. First the histories of macro parameters such as flow rate, rotational speed and runner moment and trajectory of working condition point are given. Secondly, the difference of guide vane moment under different working conditions is analysed, and the fluctuation components are decomposed by frequency domain analysis. Finally, the main factors affecting the fluctuation of guide vane moment are obtained by comparing pulsation and flow patterns. The results show that, due to different flow structures in different working conditions, there is a significant difference in the characteristics of guide vane moment, which affects the closing and opening trend of guide vanes in different positions. In contrast, the pulsation amplitudes of guide vane moment in no-load mode are the largest, followed by the pump braking mode, and those in the turbine and pump mode are smallest. The maximum guide vane moment is smaller than the design moment of guide vane fastening device during the transient, but it reaches 85.7% of the design value.