AUTOMATIC EXTRACTION AND EXHAUST PRESSURE TYPE TURBINE CONTROL SYSTEM

摘要

1,267,590. Automatic control of steam turbines. TOKYO SHIBAURA DENKI K.K. July 8, 1969 [July 8, 1968], No.34296/69. Heading G3R. In a multi-stage turbine with steam extraction between stages, constant speed or pressure conditions are maintained by automatically controlling electro-hydraulic steam inlet valves to each stage in dependence on a combination selected by a switch from electrical signals corresponding to extraction steam pressure, exhaust steam pressure and turbine speed. As shown, electrohydraulically operated valves 47, 48 respectively control the flow of steam to and between high- and low-pressure stages 11, 12 of a turbine driving an electrical generator 14. Exhaust steam and steam from between the stages is led off through conduits 20, 17 to supply energy for other purposes. Electrical signals dependent on turbine speed, interstage steam pressure and exhaust steam pressure are produced at 22, 24, 23 and compared with desired values set at 26, 27, 25 to produce error signals at 32, 33, 31. With a selector switch 51 in the position shown, the speed error signal 32 controls both steam valves 47, 48 in the same sense to correct the speed without affecting the interstage output of steam and the interstage steam pressure error signal 33 controls the steam valves in opposite senses, by virtue of inverter 45, to correct interstage pressure without affecting turbine output. With switch 51 in its other position, the interstage steam pressure error signal 33 controls main steam inlet valve 47 only to correct interstage pressure without affecting exhaust steam pressure which is automatically controlled by the exhaust steam pressure error signal 31 controlling both steam valves 47, 48 in the same sense. The control signals are suitably weighted in dependence on the thermal drops in the turbine stages by potential dividers 40, 41, 42. If the speed error signal exceeds a value set at 49, a device 50 operates to close both steam valves 47, 48.