Patent GB-1503890-A (GB)
Title: Electric power plant with turbine acceleration control system
Inventor: BRAYTENBAH ANDREW S
IPC: F01D19/00
Filed: 1976-09-28
Abstract: 1503890 Turbines WESTINGHOUSE ELECTRIC CORP 28 Sept 1976 [30 Sept 1975] 40180/76 Heading FIT [Also in Division G3N]  In running a turbo-generator up to synchronous speed, steam flow through one stage of the turbine is controlled in accordance with a comparison of actual and desired turbine speeds while steam flow through another stage of the turbine is maintained substantially constant. In the embodiment shown, steam generators 101A-C are in the helium coolant gas circuit of a reactor 100 and supply super-heated steam to two parallel turbo-generators each including a high pressure turbine 108, (120), an intermediate pressure turbine 111, (122) and a low pressure turbine 112, (123). The steam is reheated between the HP and IP turbines, and there are valved by-passes 114, (115); 131, 133;(154, 155) across the turbines. Auxiliary turbines ASTA-C drive helium circulators 102A-C. In running either of the turbo-generators up to synchronous speed (3600 rpm), the switch 405, Fig. 4, is initially set to apply a closure bias 420 to the intercept valve positioner 175 (185) so that no flow takes place through the IP and LP turbines until the speed reaches 1800 rpm. Up to 1800 rpm, steam flows through the HP turbine under the control of throttle valve 106 (118), whose positioner is supplied with the output of speed controller 170 via switch 403, and switch 404 is set to apply an open bias 412 to the governor valve positioner 176a, (186a). From 1800 to 3300-3450 rpm, switch 405 is set to apply the speed controller output to the intercept valve positioner, switch 404 still applies the open bias to the governor valve positioner and switch 403 applies the output of #P controller 408 to the intercept valve positioner so that the flow through the HP turbine remains constant. From 3300-3450 to 3600 rpm, switch 404 applies the speed controller output to the governor valve positioner, switch 403 applies an open bias 411 to the throttle valve positioner and switch 405 applies the output of a pressure controller 415 to the intercept valve positioner so that the flow through the IP and LP turbines remains constant. During acceleration of either turbogenerator, a respective by-pass valve control system 146 (165) maintains the pressure in the hot reheat header 125 at a level specified by a signal generator or computer 142 (163) to maintain a desired minimum flow in the reheater. In each by-pass valve control system, the signal applied to the intercept valve positioner 175 (185) is fed via multiplier 209 to summer 206 for summing with a bias signal and a signal from a controller 204 receiving the output of pressure comparator 201. The summer output is applied via low-select 211 to the positioner 135 (157) of one by-pass valve 132, (154) until by-pass flow reaches a given level as established by a signal from function generator 213, at which stage the latter signal is applied to positioner 135 (157) and to comparator 216 whose output is applied to the positioner 137, (159) of a second by-pass valve 134, (156). In alternative embodiments, steam is initially passed through the IP and LP turbines rather than through the HP turbine, and the intercept and throttle valve positioners may be controlled by position controllers rather than pressure or #P controllers during those phases when they are required to hold steam flow constant. Each of the controllers in the speed control systems is of P+I type.