Combined cycle electric power plant

A combined cycle power plant having a gas turbine plant and a steam turbine plant combined together, the power plant comprising:

• an exhaust heat recovery boiler for generating steam for driving the steam turbine by using exhaust heat from the gas turbine;
• and
• a steam cooling system for cooling a target high-temperature portion in the gas turbine by using steam, where superheated steam from the steam cooling system is recovered and used in the steam turbine, and
• wherein the power plant has an air duct, connected to a steam path for supplying steam for cooling the target high-temperature portion, for cooling this portion using air if the steam for cooling is insufficient typically when the plant is activated or stopped, and the air duct including means for boosting the air to have a pressure higher than that inside a combustor of the power plant.