GB1347934A - Control system for an elastic fluid turbine - Google Patents

Abstract

1347934 Turbine plant TOKYO SHIBAURA ELECTRIC CO Ltd 7 April 1972 [19 April 1971 16176/72 Heading FIT [Also in Division G3] An extraction turbine plant comprising an electric generator 13 driven by high and low pressure turbine stages 11, 12, and admission and interstage valves 15, 16 has a control system which during normal running controls both valves 15, 16 in response to rotational speed of the turbine and pressure of the extracted fluid (e. g. steam), control of admission valve 15 by extraction pressure being interrupted when circuit breakers 19 trip upon loss of generator load. Turbine speed is sensed by two electromagnetic pick-ups 23, 24 whose outputs are applied via detectors 25, 26 and gate 27 to a speed-load controller 30 where the speed signal is compared with a reference value from speed setting device 33. The error signal is limited by a further reference signal from maximum load setting device 34 and is passed through an amplifying circuit 32 to an adder 35 which, during normal operation, also receives a pressure signal from controller 43 via the closed contacts 57b of relay 57. The adder output is amplified at 40 and applied to an electro-mechanical converter 41 driving an hydraulic servo-mechanism 42 which adjusts admission valve 15 to maintain the speed constant. The pressure in extraction line 17 is sensed by detector 29 which transmits a signal to pressure controller 43 where the signal is compared with a reference from pressure setting device 46. The error signal is limited by a further reference from maximum pressure setting device 47 and is passed through amplifier 45 to an inverter, or polarity changer, 48 and thence to adder 49. The latter also receives a speed signal from controller 30 and transmits a signal to adjust interstage valve 16. The system is arranged such that, during normal operation, adjustment of speed does not affect the extraction pressure and vice versa. Should there be a fault in the power system 21 or load 22 of electric generator 13 then main circuit breakers 19 trip causing contacts 19b to close and energize relay 58. The consequential closing of contacts 58a energizes relays 57, 60 to open contacts 57b and close contacts 57a, 60a. Thus the pressure signal from controller 43 is no longer transmitted to adder 35 but is replaced by a zero pressure level signal Po so that admission valve 15 is then operated in response only to the signal from speed controller 30. However the extraction pressure signal is still applied to adder 49 to cause closing of interstage valve 16 and thus prevent turbine overspeed. Relays 57, 58, 60 may be replaced by transistorized circuitry.