Automatic Load Control for Turbine Generators

This paper describes a load-control apparatus recently installed on two 20,000-kw turbines at the power plant of the Tennessee Coal Iron and Railroad Company at Fairfield, Ala., to reduce the magnitude of load swings imposed on a tie line by a hot-strip mill in the Tennessee Coal Iron Company Plant. The power plant contains three 20,000-kw turbine-driven generators and is tied in with the Alabama Power Company to furnish the steel-mill load. Previous to the installation of the equipment herein described, the three 20,000-kw turbine generators have carried load under control of their speed governors and the variations in strip-mill load which are about 20,000 kw were imposed upon the Alabama Power Company tie line causing objectionable disturbances on the connecting power system. It was desired to develop a means of imposing all or part of the strip-mill load on the Tennessee Coal Iron and Railroad Company turbine generators to reduce these disturbances. Several methods were considered, and the one selected was based upon a static watt-measuring circuit, the output of which is an Amplidyne generator. The Amplidyne in turn operates the pilot motor of an hydraulic (oil) relay at the turbine to control the steam admission valves.