Steam turbine plant

A steam turbine plant comprising:

• a high-pressure side steam turbine configured to have a high-pressure casing into which steam is configured to flow and a high-pressure turbine rotor which is provided in the high-pressure casing, both ends of which face outward from openings formed in the high-pressure casing, and which is configured to be rotated by the steam flowing into the high-pressure casing;
• a low-pressure side steam turbine configured to have a low-pressure casing into which the steam exhausted from the high-pressure side steam turbine is configured to flow and a low-pressure turbine rotor which is provided in the low-pressure casing, both ends of which face outward from openings formed in the low-pressure casing, and which is configured to be rotated by the steam flowing into the low-pressure casing;
• and
• a condenser which restores a steam exhausted from the low-pressure side steam turbine into water,
• wherein the high-pressure side steam turbine has high-pressure gland portions that are configured to supply the steam to gaps between the openings of the high-pressure casing and the ends of the high-pressure turbine rotor as gland steam and thereby are configured to seal the gaps,
• the low-pressure side steam turbine has low-pressure gland portions that are configured to supply the gland steam to gaps between the openings of the low-pressure casing and the ends of the low-pressure turbine rotor and thereby are configured to seal the gaps, and
• the steam turbine plant further comprises
• a gland regulator line configured to guide the gland steam from the high-pressure gland portions to the low-pressure gland portions,
• a rotor-driving steam supply line configured to branch off from the gland regulator line and to supply some of the gland steam to a flow passage of the steam that rotates the low-pressure turbine rotor in the low-pressure casing,
• a flow control valve configured to adjust a flow rate of the gland steam flowing along the rotor-driving steam supply line,
• a correlation value detector configured to detect a steam flow rate correlation value that correlates to a flow rate of the gland steam flowing along the gland regulator line,
• an exhaust line which branches off from the gland regulator line and carries a part of the gland steam to the condenser, and
• an on-off valve provided on the exhaust line,
• wherein the flow control valve is opened when the steam flow rate correlation value detected by the correlation value detector is greater than or equal to a preset value.