Steam turbine overspeed protection system, and steam turbine

A steam turbine, wherein, the steam turbine comprises a steam turbine overspeed protection system, the steam turbine overspeed protection system comprises:

• a drive gear, the drive gear is arranged to match a rotation speed of a rotor of a steam turbine;
• a rotating shaft, the rotating shaft is parallel to an axis of the drive gear and capable of rotating at a critical rotation speed;
• a protective gear, the protective gear is arranged on the rotating shaft and forms a lead screw nut mechanism with the rotating shaft, and the protective gear is arranged to engage with the drive gear when the rotation speed of the drive gear exceeds the critical rotation speed;
• and
• an operating rod capable of being connected to the protective gear;
• wherein, when the drive gear engages with the protective gear, the protective gear moves in the axial direction of the rotating shaft and thereby drives the operating rod to move and produce an action that activates a protection device for preventing steam turbine overspeed.