PURPOSE: To stop a hydraulic turbine when its overspeed is detected or the hydraulic pressure of its pressure source drops, by arranging an emergency shut-off valve on a pipe line which connects a servomotor controlling the opening and closing of a guide vane to a pressure distributing valve.

CONSTITUTION: When the solenoid of a selector valve 33 is excited by a signal from an overspeed detecting relay, an emergency shut-off valve 21 is switched over, and ports F and K, and ports J and H are communicated respectively. As the result, servomotors 12, 13 move a guide ring 11 in the direction of closing a guide vane 8, and a hydraulic turbine is made to stop. When the pressure of a hydraulic source drops, a pilot hydrualic pressure drops, and a hydrualic pressure dropping selector 29 is switched over, and a pipe line 27 is switched over to a drain circuit. As the result, ports F and K, and ports J and H of the emergency shut-off valve 21 are communicated respectively, and the guide vane 8 is shut, and it is enabled to make the hydrualic turbine stop.