Patent US 3,974,643

A combined cycle electric power plant includes gas and steam turbines and steam generators and a digital/analog control system. A backup control is included for each of the gas turbines with an outlet or preferably blade path temperature limit control which prevents the operator from causing the turbine to operate above a temperature limit reference. The temperature limit control further restricts the rate at which the operator can move the gas turbine operating or load level toward the temperature limit value. When the turbine is operating at a load below the temperature limit value, the operator can freely move the fuel reference until the blade path temperature approaches the temperature limit value.