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 the 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 the abnormality has occurred in opening degree control of the steam turbine valve, wherein
• the steam turbine valve drive device further includes a servo driver that performs feedback control of the servomotor based on a command rotation speed received from the control unit and an actual rotation speed received from the servomotor,
• the servo driver is configured to be switchable between an ON state in which the feedback control is performed and an OFF state in which the feedback control is not performed,
• the detection unit detects whether the servo driver is in the ON state or whether the servo driver is in the OFF state, and
• the determination unit determines that the abnormality has occurred in opening degree control of the steam turbine valve when the detection unit detects that the servo driver is in the OFF state.