Turbine acceleration governing system
First Claim
1. In a turbine speed control system which is operative to control the speed of a steam turbine through a turbine start-up operation by regulating the position of at least one steam admission valve of said turbine in accordance with a speed control function based on a computed speed error between an adjustable speed reference signal and a signal representative of the actual speed of said turbine, said speed reference signal being adjusted, at times, to converge to a desired speed demand signal at a selected acceleration, an improvement comprising:
- a first controller operative to control the speed of said turbine at selected accelerations from turning gear to a predetermined turbine speed value;
a second controller selectively operative to govern said turbine accelerations as controlled by said first controller in accordance with calculated present and anticipated rotor stresses of said steam turbine, said second controller performing said rotor stress calculations concurrently with the speed control operations of said first controller;
means for generating a plurality of signals representative of actual temperature differences of predetermined portions of said steam turbine and for providing said differential temperature representative signals to said first controller;
and wherein said first controller is further operative to reduce said turbine acceleration to substantially zero upon the detection of at least one of said representative temperature difference signals exceeding a preset limit value respectively associated therewith, said first controller being still further operative to detect when said turbine speed is controllably held substantially fixed in one of a number of predetermined critical speed zones as a result of said acceleration governing by said second controller or as a result of a temperature difference signal exceeding its preset limit value and to adjust said turbine speed outside of said one critical speed zone during either one of said detected turbine speed states.
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Accused Products
Abstract
A turbine speed control system comprising a pair of concurrently operable electronic microprocessor-based controllers which are coupled together by a data link to functionally cooperate in controlling turbine acceleration primarily during start-up operations in accordance with a set of predetermined measured and calculated turbine conditions. One controller is operative to control the speed of the turbine at selected accelerations from turning gear to a predetermined speed value. This same controller monitors a plurality of temperature differences from preselected regions of the turbine and inhibits turbine acceleration in accordance with an out-of-limit temperature condition associated therewith. In addition, the one controller is further operative to selectively override the turbine speed hold initiated by an out-of-limit temperature condition, the override permitting the one controller to proceed with controlling the speed of the turbine at a desired acceleration. The other controller is selectively operative to govern the turbine acceleration as controlled by the one controller based on calculated present and anticipated rotor stresses which are derived concurrently with the speed control operations of the one controller. A turbine speed hold may be initiated by either a detected differential temperature out-of-limit condition or a detected calculated rotor stress limit condition. In either case, the one controller is further operative to detect if the speed hold occurs in one of a number of predetermined critical speed zones and to adjust the turbine speed outside of the zone in which the speed hold occurs.
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Citations
9 Claims
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1. In a turbine speed control system which is operative to control the speed of a steam turbine through a turbine start-up operation by regulating the position of at least one steam admission valve of said turbine in accordance with a speed control function based on a computed speed error between an adjustable speed reference signal and a signal representative of the actual speed of said turbine, said speed reference signal being adjusted, at times, to converge to a desired speed demand signal at a selected acceleration, an improvement comprising:
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a first controller operative to control the speed of said turbine at selected accelerations from turning gear to a predetermined turbine speed value; a second controller selectively operative to govern said turbine accelerations as controlled by said first controller in accordance with calculated present and anticipated rotor stresses of said steam turbine, said second controller performing said rotor stress calculations concurrently with the speed control operations of said first controller; means for generating a plurality of signals representative of actual temperature differences of predetermined portions of said steam turbine and for providing said differential temperature representative signals to said first controller; and wherein said first controller is further operative to reduce said turbine acceleration to substantially zero upon the detection of at least one of said representative temperature difference signals exceeding a preset limit value respectively associated therewith, said first controller being still further operative to detect when said turbine speed is controllably held substantially fixed in one of a number of predetermined critical speed zones as a result of said acceleration governing by said second controller or as a result of a temperature difference signal exceeding its preset limit value and to adjust said turbine speed outside of said one critical speed zone during either one of said detected turbine speed states. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification