an automatic control system enabling comprehensive operation of a reheat steam turbine with sliding or constant pressure boilers . the control system includes an hp control valve for regulating steam flow to the high - pressure turbine according to load and speed demands , an intercept valve for regulating steam flow to the low - pressure turbine and for reheater pressure control , and a bypass flow system for bypassing excess boiler steam during periods of low loading . the bypass system includes a high - pressure bypass sub - system and a low - pressure bypass sub - system , each having a flow control valve and provision for desuperheating the steam . a signal indicative of actual load demand and proportional to the product of boiler pressure and main control valve flow demand is produced . from the ald signal , reference functions are generated to effect control of the bypass valves . the intercept valve is controlled directly by the ald signal with a regulation factor inversely proportional to the minimum allowable reheat pressure . coordinated valve control is effected during all principal phases of turbine operation .