System and method for operating a steam turbine with improved

Abstract

The throttle and governor valves of a steam turbine are operated by a digital computer control system to provide speed and load control for the turbine. The computer includes a speed and load control which periodically generates control outputs and a separate logic control which responds to panel and contact inputs to generate logicals which structure the speed and load control. An analog scan periodically enters feedback parameters into the computer for use by the controls. An input contacts scan enters feedback logicals into the computer on demand, or under certain conditions periodically. A monitor operates with an auxiliary synchronizer to control the execution of the scans and the controls. The speed and load controls are bid for execution once each second to generate the control outputs which are applied to an external electrohydraulic control for the valves. The analog scan is bid for execution once each half second and the logic control is bid for execution on demand for performance of a logic function. The auxiliary synchronizer is bid for execution once each tenth of a second. The monitor controls the execution with a priority order of auxiliary synchronizer, speed and load control, analog scan and logic control. Certain logic and controller functions are performed commonly by a single programmed element as needed at different points in time by multiple parts of the controls.