Abstract: A water turbine comprises a runner, guide vanes formed of a plurality of vanes arranged outside the runner in a peripheral direction, each of the vanes being rotatable about a center axis thereof parallel with a rotation shaft of the runner, stay vanes formed of a plurality of vanes outside the guide vanes in a peripheral direction, and a casing covering the outside of the stay vanes, wherein sections of each vane of the guide vanes perpendicular to the center axis are displaced to the rotation direction of the runner from an upper side of the runner to a lower side, under the condition that the guide vanes are shutdown.

Abstract: A method of starting a variable-speed pump turbine or a variable-speed pump driven by a variable-speed generator motor or a variable-speed motor connected to an electric power line in parallel therewith. The generator motor or the motor is first operated at low speed with the guide vanes or the delivery valve fully closed. The low speed is lower than a stable starting speed of the pump turbine or the motor but high enough to prevent backward flow of water into the pump turbine or the pump. After the operation is set at the low speed, the guide vanes or the delivery valve are opened and the opening degree is gradually opened until the speed is increased to a speed optimum for the steady operating condition of the pump turbine or pump. This method effectively suppresses abrupt increase in the pump input power required for the driving of the pump turbine or the pump, whereby unfavorable effect on the electric power line is avoided advantageously.