Abstract：In order to study the negative effects of abnormal transient processes on the pump turbine and the corresponding improved measures, the inherent feature of performance curve of the pump turbine(named S-shaped characteristics),together with the recent research progress in several typical transient processes of the pump turbine, is introduced. The S-shaped characteristics shown in the performance curve of the pump turbine along the guide vane opening line are briefly introduced, with its physical origins and negative effects. A detailed introduction to the hysteresis phenomenon of the pump turbine is performed and it is found that the present discharge of pump turbine at the fixed rotational speed is not a unique value because the operational condition of the pump turbine depends not only on the current input of the system but also on the history of the system and hence the hysteresis phenomenon leads to the drop of water head,low efficiency, vibrations and noise. The generation condition of the hysteresis phenomenon, the influence of rotational speed and the improved methods based on changing runner inlet and outlet angles are set forth. Measurement of the dynamic stress on the shaft and influences of the rotor-stator interaction on the measured signal analysis are both elaborated,giving the corresponding phenomena, basic characteristics and paramount influencing parameters. The instability of the pump turbine working with no load at start-up as well as the instability at the guide vanes closure, and the solutions to them are also expounded. Mereover, the advantage and the disadvantage of different methods are compared.
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