Patent ID: 8356974

Claim:
A steam turbine, comprising: a casing; a turbine rotor disposed through the casing; a labyrinth portion provided circumferentially along the turbine rotor between the casing and the turbine rotor; a gas supply system configured to supply cooling air for the turbine rotor to the labyrinth portion when starting the steam turbine; a sealing steam supply system configured to supply sealing steam to the labyrinth portion; an expansion detector configured to detect an amount of a thermal expansion of the turbine rotor in the axial direction; a movement detector configured to detect an axial moving distance of a sealing portion of the labyrinth portion in the axial direction of the turbine rotor; and a controller configured to: calculate a thermal expansion difference between the turbine rotor and the labyrinth portion based on detection information detected by the expansion detector and the movement detector, control the gas supply system to increase a supply amount of the cooling air according to an increased amount of the thermal expansion difference when the thermal expansion difference is increased, and control the gas supply system and the sealing steam supply system to decrease the supply amount of the cooling air and increase a supply amount of the sealing steam when the thermal expansion difference is decreased.