GB1265841A - - Google Patents

Abstract

1,265,841. Programmed control. WESTINGHOUSE ELECTRIC CORP. March 28, 1969 [April19, 1968], No.16330/69. Heading G3N. [Also in Division F1] The flow of steam through at least one section of a steam turbine is determined by a steam valve controlled by a system responsive to a steam valve position demand, determined in accordance with a predetermined characterization required to satisfy an input demand for an operating variable placed under end control, which is correctively modified by the error between the actual and input demand valves of the variable. As shown, Fig.1 a three-stage axial flow turbine 10, driving an A .C . generator 16, is supplied at a constant steam pressure from a drum type steam boiler 26. The turbine is fed through throttle-inlet valves TV1-TV4 and governor-inlet valves GV1 -GV8 arcuately spaced about the turbine high-pressure casing. The turbine highpressure section 20 is interconnected with the intermediate pressure section 22 through a reheater 28, stop-valves SV preventing steam back flow and intercept valves IV provide overspeed protection. The low-pressure section 24 exhausts to a condenser 32. During start-up the valves GV1-GV8 are initially fully open and control is through valves TV1-TV4, at transfer the valves TV1-TV4 are fully open and valves GV1 -GV8 are operated in a predetermined sequence to reduce thermal stress. The valves TV1 are positioned by hydraulic actuators 42 controlled by position controls 50 responsive to position feedback from detectors PDT1-PDT4. Similarly, valves GV1-GV8 are positioned by actuators 44 operated by controls 52 responsive to position feedback from detectors PDG1-PDG8. The valves SV, IV are positioned by hydraulic actuators 46, 48, the valve IV being operated by a control 56 responsive to position feedback from a detector PD1 and the position of the valve SV is indicated by status contacts CSS. The signals from the valve position detectors PDTI-PDT4, PDG1-PDG8, PD1 status contacts GSS, a generated power detector 18, a phonicwheel speed detector 58, an impulse pressure detector 40 and a throttle pressure detector 38 are employed in a programmed computer operating system 60, Fig.2. The central processor 62 is interfaced with the turbine operating conditions through 1) a contact closure input system 64, responsive to interlock and protection status contacts 66 and the SV valve status contacts CSS, 2) an analogue input system 72, responsive to, impulse pressure and power detectors 40, 18 intercept throttle and governor valve position detectors PD1-PDG8 and miscellaneous sensors 74 comprising generator hydrogen coolant pressure and temperature detectors, (not shown) and 3) a pulse input system responsive to the speed detector 58. The control programme is entered into the central processor core through a tape reader system 78, datalogging being effected by a teletypewriter system 80 and a printer 82, and display by a device 98. The transfer of information through the computer'is effected by an interrupt system 84. The processor 62 carries out a plurality of control programmes, which are described in detail, whereby signals are derived to determine through a contact closure system 86 1) analogue outputs from a system 88 to auxiliary devices such as the hydrogen coolant system, (not shown), 2) alarm devices 94, 3) HP valve fluid and lubrication control by a system 87 and, 4) valve positioning signals from a system 90 to controls 50, 56, 52. A start signal is initiated manually through a supervisory control 68 and start-up cleared by interlock permissives, a throttle and governor valve programme is then periodically executed to bring the turbine up to synchronous speed, at a rate determined by a stored ramp curve of turbine speed versus time, through a feedback control loop operation. On load, a load reference demand signal is applied in a feed-forward load control loop which includes the programmed processor 62 the governor controls 52 and the governor valves GV1-GV8 with their position detectors PDG1-PDG8. A load reset feedback loop, employing the impulse pressure detector 40, applies a steady state correction to the load reference by being cascaded into the feed-forward load control loop.