Steam cooled system in combined cycle power plant

摘要

A gas turbine steam cooled system has a high temperature portion 8 outlet steam temperature maintained to a predetermined value without a cooling steam pressure becoming lower than the pressure in the gas turbine cylinder. Steam coming from an intermediate pressure superheater 10 of a waste heat recovery boiler 2 is led into the high temperature portion 8 of the gas turbine for cooling thereof. The temperature of the cooling steam at the outlet of the high temperature portion 8 is detected by a high temperature portion outlet steam temperature detector 15, and a signal thereof is sent a lower value selector 19 via a temperature controller 11. Pressure in the gas turbine cylinder is detected by a gas turbine cylinder pressure detector 17, and pressure of the cooling steam at the high temperature portion 8 outlet is detected by a high temperature portion outlet steam pressure detector 16. A differential signal thereof is sent to a pressure controller 18. Signals from the temperature controller 11 and the pressure controller 18 are inputted into the lower selector 19, and temperature control valve 12 is controlled by the lower value thereof to be opened and closed.