Abstract: A control system of pumping operation comprises a cycloconverter for converting AC power from a AC power system into AC power having a given frequency, anAC exciting generator-motor, having a stator side electrically connected to the AC power system, having a rotor side electrically connected to the cycloconverter, and having a rotor shaft mechanically coupled to a pump-turbine by which the pumping operation is carried out, a circuit breaker inserted between the AC power system and the AC exciting generator-motor, a rotation speed controller for controlling a rotation speed of the AC exciting generator-motor such that the rotation speed becomes slow when the pumping operation is to be stopped, an AC excitation controller for decreasing a degree of excitation effected by the cycloconverter, wherein decreasing of the excitation degree starts when the rotation speed of the AC exciting generator-motor reaches a given minimum value, and a circuit breaker controller for turning off the circuit breaker when input po

Abstract: A method for stopping a multi-stage hydraulic machine with an inlet valve, guide vanes including highest and lowest stage guide vanes, and a return passage connected between flow passages of respective stages, wherein the machine is in turbine operation, including the steps of initiating the closing of the highest stage movable guide vanes firstly and the lowest stage movable guide vanes secondly and judging whether a closing relation between the highest and lowest stage vanes is normal or not in accordance with predetermined criteria after initiation of closing the lowest stage movable guide vanes. The method includes the steps of controlling the closing of the lowest stage movable guide vanes based on the judgement result, and the step of closing the inlet valve.

Abstract: An increment speed per unit time from the detected rotation speed of a water turbine or a pump turbine with an inlet valve is compared with a prescribed increment to deliver a close order to the inlet valve, when the increment becomes greater than the prescribed increment, for closing the inlet valve to a prescribed opening. Then, a fully open order to the inlet valve is delivered under the condition that neither an emergency shutdown order nor a quick shutdown order is issued to the water turbine or the pump turbine, when a speed governor performs a normal operation.