Steam turbine valve abnormality monitoring system, steam turbine valve drive device, steam turbine valve device, and steam turbine plant

A steam turbine valve abnormality monitoring system that monitors an abnormality in opening degree control of a steam turbine valve driven by a steam turbine valve drive device including:

• a cylinder housing a piston disposed on an operating rod operating the steam turbine valve and having a load side oil chamber and an unload side oil chamber partitioned by the piston;
• a bidirectional pump that selectively supplies hydraulic oil to the load side oil chamber and the unload side oil chamber;
• a servomotor that drives the bidirectional pump;
• a control unit that controls the servomotor;
• and an oil storage unit supplied with the hydraulic oil leaked from the bidirectional pump, the steam turbine valve abnormality monitoring system comprising:
• a detection unit that detects a state of the steam turbine valve or the steam turbine valve drive device;
• a determination unit that determines whether or not an abnormality has occurred in opening degree control of the steam turbine valve based on a detected result of the detection unit;
• and
• an abnormality processing unit that issues an alarm or issues a stop command of a steam turbine when the determination unit determines that an abnormality has occurred in opening degree control of the steam turbine valve.