Abstract: The present stress in the turbine rotor is estimated at each control period, from the steam temperature and pressure at the turbine inlet. In addition, the future turbine inlet steam temperature or pressure is preestimated once every n.sub.T control cycles, for a given speed or load changing rate, making use of data concerning the changing rate of the turbine steam inlet temperature or pressure in relation with the change of the speed or load, which has been obtained by a learning of the past turbine operating condition. This future steam temperature or pressure at the turbine inlet is used as a factor for preestimating the future stress expected to be caused in the turbine rotor. The preestimation of the rotor stress is performed for a plurality of assumed speed or load changing rates. The turbine is controlled at the maximum speed increase-rate or load changing rate which would not cause the future stress preestimated over a given preestimation time to exceed a limit stress.

Abstract: A governing system for use in a sliding-pressure type turbine power plant, in which a target level for a main steam pressure is automatically set in response to a load demand, while two or more regulating valves are controlled according to a valve-positioning signal so as to eliminate a deviation of an actual load from a load demand, whereupon a target level for the main steam pressure is corrected, based on the diviation of the actual opening from the target opening of each regulating valve, whereby the main pressure generated in a boiler is regulated to a corrected target level. This governing system includes a valve driving mechanism functioning such that all regulating valves be opened at a time in a range up to a given opening, and thereafter the regulating valves be opened one after another, commensurate to the magnitude of a control signal, after entering a range beyond the aforenoted given opening.

Abstract: In a steam turbine plant with feed water heaters receiving steam extracted from the turbine to apply in heat exchange with the feed water being supplied to the boiler, the drain water level in the water heaters is monitored so that when the drain level exceeds a predetermined abnormal level, for example due to rupture of the feed water pipes in the feed water heater, steam supplied to the turbine is automatically reduced to runback the load on the turbine, and thereafter the extraction of the steam to the malfunctioning feed water heater from the turbine is stopped and the feed water heater is bypassed with respect to the feed water flowing to the boiler, so that the malfunctioning feed water heater is thus isolated from the turbine plant.