Patent GB-1214424-A (GB)
Title: System for supervising steam turbine operation
IPC: F01D19/02
Filed: 1969-03-28
Abstract: 1,214,424. Programmed control of turbines. WESTINGHOUSE ELECTRIC CORP. March 28, 1969 [April 19, 1968], No.16323/69. Heading G3N. [Also in Division F1] The operation of a steam turbine is supervised, to maintain the thermal strain of the rotor at a minimum, by determining the steam temperature in a region in heat transfer relation with a preselected turbine rotor portion, determining the thermal condition of the rotor portion and controlling the turbine steam conditions in the region under the constraint of limiting the rate of change of said steam temperature as a function of the thermal condition. A three-stage steam turbine is supplied from a constant delivery pressure steam-generating system and is controlled by the selective, and variable, actuation of hydraulic governor and throttle inlet valves by a computer control system responsive to impulse stage pressure, electrical generated power and turbine speed. Steam enters the high-pressure stage of the turbine, Fig. 3, through a plurality of peripherally disposed inlets 108 and nozzle blocks 105, and is directed through two rows of impulse blades 107, 109 and a row of stationary blades 111 into an impulse chamber 110 where the steam flow is reversed and passes through reaction blading 112. A thermocouple probe 114 measures the impulse chamber temperature and inner and outer wall temperatures are sensed by thermocouple probes 106, 104 as a basis for a casing strain determination. It is stated that a steam temperature sensor can be employed in the intermediate pressure inlet steam chamber. The turbine is controlled by a computer system which carries out a dynamic constraint sub-programme, block 156, Fig.10 to determine maximum load or speed change demands to be called up in the main programme. The rotor surface strain is determined, block 164, from the impulse chamber temperature T 1  by equating it to the rotor surface temperature T 5 , during operation, run-up or shutdown, as a function of temperature T 1  and the steam to rotor heat transfer. The determined strain Eg is stored, block 166, the rotor fatigue damage calculated, block 168 and accumulated, block 170, and a strain limit applied, block 172, having a value, predetermined, or selected from a table of values in correspondence with computer derived conditions. The bore thermal loadings for HP and IP sections are determined, block 174, from rotor temperature gradients, as for block 164, and the centrifugal stress, block 176, calculated from stored data and the output of a speed sensor. A combined load limit is derived, block 184, from a predetermined value, or stored sets of operating conditions. Similarly, HP casing wall strain is derived, block 180, from casing thermocouples and a fixed casing strain limit, block 182. An allowed maximum rate of change of impulse chamber steam temperature is determined, block 184, as a function of surface strain, block 164. The operating mode is questioned, block 190, and for a start-up or run-down responds to bore loading or casing strain limits, block 198, to control the maximum steam flow rate, block 200, and/or the maximum steam temperature rate of change by control of steam valve positioning devices.