US3913329A - Turbine overspeed control system - Google Patents

Turbine overspeed control system Download PDF

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Publication number
US3913329A
US3913329A US512808A US51280874A US3913329A US 3913329 A US3913329 A US 3913329A US 512808 A US512808 A US 512808A US 51280874 A US51280874 A US 51280874A US 3913329 A US3913329 A US 3913329A
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United States
Prior art keywords
amplifier
speed
valve
turbine
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US512808A
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English (en)
Inventor
David Manuel Priluck
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General Electric Co
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General Electric Co
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Filing date
Publication date
Application filed by General Electric Co filed Critical General Electric Co
Priority to US512808A priority Critical patent/US3913329A/en
Priority to AU82768/75A priority patent/AU489535B2/en
Priority to CA236,430A priority patent/CA1038474A/en
Priority to GB39331/75A priority patent/GB1519833A/en
Priority to CH1254175A priority patent/CH599454A5/xx
Priority to DE19752542936 priority patent/DE2542936C3/de
Priority to JP50119031A priority patent/JPS5162203A/ja
Application granted granted Critical
Publication of US3913329A publication Critical patent/US3913329A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
    • F01K7/16—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type
    • F01K7/22—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type the turbines having inter-stage steam heating
    • F01K7/24—Control or safety means specially adapted therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
    • F01D21/02—Shutting-down responsive to overspeed

Definitions

  • This invention relates to turbine overspeed control systems for limiting turbine speed increases during the occurrence of sudden decreases in a load driven by the turbine, where the turbine must be capable of stable operation at the new load. More particularly, this invention relates to an overspeed control system for a reheat turbine generator which must be capable of stable operation upon separation from a large electric system in which generator normally operates synchronously with other generators in the system.
  • Control systems of the above-described type operate effectively for small load losses or slowly decreasing loads where both valves partially close and the reduced load is proportionately distributed over all turbine stages. These systems also operate effectively on the occurrence of sudden severe load reductions where the load decreases to an amount which the high pressure stages are capable of driving alone. In this case a ram in the intercept valve is actuated causing rapid complete valve closure and a consequent loss of the major portion of driving power normally provided by the reheat stages. Steam flow to the high pressure stages is reduced by the main control valve to that. level necessary to support driving of the reduced load.
  • the present invention eliminates the instability experienced with prior art systems during severe load changes by improving intercept valve control and eliminating the need for sudden complete intercept valve closure. Thus the speed instability caused by cycling of the intercept valve is avoided.
  • Intercept valve control is improved by development of a nonlinear command signal and application of this signal to the valve causing rapid motion of the valve during that portion of valve movement having little effect on the steam flow and causing less rapid motion of the valve during that portion of valve movement having a significant effect on steam flow.
  • a command signal controlling intercept control valves in such a manner as to compensate for intercept valve non-linearities is generated by two amplifiers.
  • the command signal is developed at the output of a first amplifier and increases in magnitude at a rapid rate in response to an increase in turbine speed above the reference speed. This rapid signal increase causes rapid initial intercept valve closing motion during that portion of valve movement having little effect on steam flow.
  • a second amplifier interacts with the first to cause a reduction in the rate of increase of command signal.
  • This reduction in command signal rate of change causes less rapid valve closing motion during that portion valve movement having significant effect on steam flow.
  • the net effect of varying valve movement in this manner is a rapid, steady decrease in steam flow resulting in effective control of sudden speed increases by intercept valves. The speed instability caused by intercept valve cycling is thus avoided.
  • FIG. 1 is a block diagram of a steam turbine generator in which the overspeed control system of this invention is incorporated.
  • FIG. 2 is a curve representing the command signal utilized to compensate for control nonlinearities.
  • FIG. 3 is a schematic diagram of a circuit for generating the command signal.
  • steam produced in steam gene rater 11 flows through main stop valve 13 and main control valve 14 to a high pressure turbine stage 15.
  • the direction of steam flow is indicated by the direction of the arrows along steam lines.
  • Steam flows through the high pressure stage 15 to reheat section 17 of steam generator 11 where it is reheated and then to intercept control valves 19 and 2].
  • From valves 19 and 21 steam is applied to a first reheat stage 23, through the first reheat stage and then through second and third reheat stages 25 and 27.
  • Steam from the second and third stages 25 and 27 is collected in condenser 29 where it is condensed and then returned to steam generator 11.
  • the turbine drives generator 31 to generate electric power.
  • main stop valve 13 and intercept control valves 19 and 21 are full open.
  • the amount of steam required to rotate the turbine at a particular speed is dependent upon generator loading and is normally controlled by main control valve 14 which is governed by control 37 in response to speed changes detected by speed sensor 39. If the speed increases above a predetermined reference speed control 37 applies a command signal to intercept control valves 19 and 21 causing closing movement of the valves until turbine speed decreases to the reference speed.
  • a command signal is generated which has the characteristic of increasing rapidly during a first period to effect rapid closing movement of the intercept control valves, and then less rapidly during a second period to effect a less rapid closing movement of the valves.
  • V represents the command signal voltage
  • V represents the speed sensor output voltage.
  • Each particular V also corresponds to a particular position of the intercept valves.
  • Below reference speed A a zero volt command signal is generated and intercept control valves 19 and 21 remain full open. If turbine speed increases above the reference speed the command signal voltage rises at a rapid rate B proportional to the rate of increase of turbine speed. Closing movement of the intercept control valves at this same rapid rate compensates for the small effect valve movement has on steam flow during initial closure.
  • valves At overspeed C the valves have moved to that partially closed position where they begin to have significant effect on steam flow and the rate of change of command signal voltage is decreased to a less rapid rate D. Although the valves are also moving toward their closed positions at this slower rate D, they have significantly more control over steam flow and essentially the same rate of change of steam flow as that occurring during rate of movement B is maintained. The net effect is a rapid steady decrease of steam flow until the turbine speed is under control.
  • FIG. 3 shows a circuit for generating the command signal function of FIG. 2.
  • the command signal is generated at circuit output 41 by amplifier 42 in response to a turbine speed signal applied to circuit input 43.
  • the speed signal is applied through a resistor 44 to a summing node 45 at a first input of amplifier 42.
  • a reference speed signal is also applied to summing node 45 through resistor 46.
  • This reference speed signal is in the form of an adjustable voltage level provided at potentiometer 47 which has one end connected to a positive voltage supply and the opposite end connected to a zero volt reference or ground.
  • a second input of amplifier 42 is referenced to ground.
  • Resistor 48 and potentiometer 49 provide a feedback path from circuit output 41 to summing node 45.
  • Potentiometer 49 is included in the feedback path for the purpose of adjusting amplifier gain.
  • a resistor 50 is connected in series with the amplifier output to effectively increase amplifier output impedance so that limiting amplifier circuitry. to be described, can override the output of this amplifier if the amplifier output exceeds certain predetermined voltage limits.
  • the circuit of amplifier 51 functions to place a predetermined upper limit on circuit output voltage in accordance with a predetermined reference voltage.
  • the circuit output voltage and the reference voltage are applied to a first input of amplifier 51 through resistors 52 and 53, respectively.
  • the reference voltage is provided at potentiometer 54 which has one end connected to a negative voltage supply and the opposite end connected to ground.
  • a second input of amplifier 51 is referenced to ground.
  • Diode 55 is connected in series with the output of amplifier 51 to effectively disconnect the amplifier output from circuit output 41 at all circuit output voltages below the upper limit. If the circuit output voltage at 41 rises above the predetermined limit, an output voltage developed by amplifier 51 decreases sufficiently to forward bias diode 55 and reduce circuit output voltage to the predetermined limit.
  • the circuit of amplifier 56 functions to place a predetermined lower limit on circuit output voltage in accor dance with a predetermined reference voltage. Normally the lower limit is the zero volt level.
  • the circuit output voltage and the reference voltage are applied to a first input of amplifier 56 through resistors 57 and 58, respectively.
  • the reference voltage is provided at potentiometer 59 which has one end connected to a positive voltage supply and the opposite end connected to a negative voltage supply.
  • a second input of amplifier 56 is referenced to ground.
  • Diode 60 is connected in series with the output of amplifier 56 to effectively disconnect the amplifier output from circuit output 41 at all positive circuit output voltages. If the circuit output voltage at 41 goes negative, an output voltage developed by amplifier 56 increases sufficiently to forward bias diode 60 and increase circuit output voltage to the zero volt level.
  • An additional input signal to amplifier 42 is provided by amplifier 61 at speeds above C to cause a reduction in the rate of change of circuit output voltage.
  • This signal which increases at a constant rate with respect to turbine speed, is applied to summing node 45 through resistors 62 and 63.
  • Amplifier 61 is connected in a summing configuration similar to that of amplifier 42.
  • the turbine speed signal from circuit input 43 is applied through resistor 64 to a summing node at a first input of amplifier 61.
  • a reference speed signal representing turbine speed C is also applied to the summing node through resistor 65.
  • This reference speed signal is in the form of an adjustable voltage level provided at potentiometer 66 which has one end connected to a positive voltage supply and the opposite end connected to ground.
  • a second input of amplifier 61 is refering to ground Resistor 67 and potentiometer 68 provide a feedback path from output resistor 62 to the summing node. Potentiometer 68 is included in the feedback path for the purpose of adjusting amplifier gain. Output resistor 62 is connected in series with the amplifier output to effectively increase amplifier output impedance.
  • amplifier 69 In order to prevent the signal applied to resistor 63 from dropping below zero volts when the output from amplifier 61 goes negative limiting amplifier 69 is pro- .videcl.
  • the signal applied to resistor 63 and a reference voltage level are applied to a first input of amplifier 69 through resistors 70 and 71, respectively.
  • the refer ence voltage is provided at potentiometer 72 which has one end connected to a positive voltage supply and the opposite end connected to a negative voltage supply.
  • a second input of amplifier 69 is referenced to ground.
  • Diode 73 is connected in series with the output of amplifier 59 to effectively disconnect the amplifier output from the amplifier 42 input at resistor 63 when positive voltages are applied to resistor 63.
  • the test signal is applied through resistor 75 to cause a negative unbalance at summing node 45 resulting in development of a command signal at circuit output 41 and consequent partial closing of the intercept control valves.
  • the intercept control valve command signal is generated by amplifier 42 in response to the turbine speed signal applied to circuit input 43.
  • the speed signal which becomes increasingly more negative as turbine speed increases, is algebraically summed with a positive reference speed signal applied to summing node 45 through resistor 46. If the turbine is operating at the reference speed, the turbine speed signal and reference signal balance and a zero volt output signal is developed by amplifier 42. At speeds below the reference speed A the speed signal becomes less negative and the output of amplifier 42 goes negative. Circuit output 41 also attempts to go negative but limiting amplifier 56 prevents this by forward biasing diode 60.
  • This applied signal assists amplifier 42 in balancing the negative going speed signal at the resistor 44 input causing a less rapid rate of rise of voltage at circuit output 41.
  • This decreased rate of rise of output voltage is indicated at D in FIG. 2.
  • the ratio between the rates of rise of turbine speed and circuit output voltage during transition D can be set at a particular value by adjusting the gain of amplifier 61 at potentiometer 68.
  • the output voltage continues to increase until level E of FIG. 2 is reached at which time limiting amplifier 51 stops the voltage rise.
  • the limiting amplifiers effect sharp transition points at each change of the command signal rate. Of particular importance is a sharp transition at point C where the rate of change of valve motion must be altered to compensate for valve nonlinearities.
  • the shapness of these transition points is dependent on the stability of the references utilized to determine these points. Since the references utilized with the limiting amplifiers can be selected to be as stable as desired, by proper choice of positive and negative voltage supplies, very sharp transition points are obtainable.
  • Circuit input 74 is utilized for the periodic application of a test signal to input resistor 75. Usually this signal is applied during operation of the turbine at normal operating speed A. The signal takes the form of a negative going voltage and is algebraically added to the actual speed signal applied to resistor 44 to cause a negative unbalance at summing node 45. This negative unbalance simulates an overspeed condition and should cause the intercept valves to close to the degree required to offset the simulated overspeed.
  • the present invention overcomes deficiencies of prior art turbine speed control systems related to ineffective control of speed during load changes.
  • the effectiveness of typically used intercept control valves is greatly increased allowing rapid speed control during severe load changes without the instability problems experienced with the prior art systems.
  • a a circuit for developing a command signal for controlling the position of the valve in response to a difference between the reference speed and the actual speed of the turbine;
  • said circuit including means for developing a command signal which initially increases at a rapid rate causing rapid closing motion of the valve during that portion of valve movement having little effect on steam flow and later increases at a less rapid rate causing less rapid closing motion of the valve during that portion of valve movement having substantial effect on steam flow, whereby said circuit compensates for a nonlinear relationship between valve movement and change in the steam flow.
  • circuit comprises:
  • a. a first amplifier functioning at speeds above the reference speed to develop a first electrical output signal varying at a rapid rate with respect to turbine speed;
  • a second amplifier functioning at speeds above a predetermined overspeed to develop a second electrical output signal varying at a less rapid rate than the first output signal with respect to turbine speed;
  • a system as in claim 3 further comprising a fifth amplifier acting to prevent the second amplifer output signal from falling below a predetermined lower voltage limit.
  • a system as in claim 2 including means for provid' ing an input to said first amplifier utilized for periodic application of a test signal causing development of an output signal from said first amplifier resulting in partial closure of the valve.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Control Of Turbines (AREA)
US512808A 1974-10-04 1974-10-04 Turbine overspeed control system Expired - Lifetime US3913329A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
US512808A US3913329A (en) 1974-10-04 1974-10-04 Turbine overspeed control system
AU82768/75A AU489535B2 (en) 1974-10-04 1975-07-04 Turbine overspeed control system
CA236,430A CA1038474A (en) 1974-10-04 1975-09-25 Turbine overspeed control system
GB39331/75A GB1519833A (en) 1974-10-04 1975-09-25 Turbine overspeed control systems
CH1254175A CH599454A5 (en)) 1974-10-04 1975-09-26
DE19752542936 DE2542936C3 (de) 1974-10-04 1975-09-26 Drehzahl-Regelsystem für eine Dampfturbine
JP50119031A JPS5162203A (en) 1974-10-04 1975-10-03 Jokitaabinno chokasokudoseigyosochi

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US512808A US3913329A (en) 1974-10-04 1974-10-04 Turbine overspeed control system

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US3913329A true US3913329A (en) 1975-10-21

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US512808A Expired - Lifetime US3913329A (en) 1974-10-04 1974-10-04 Turbine overspeed control system

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US (1) US3913329A (en))
JP (1) JPS5162203A (en))
CA (1) CA1038474A (en))
CH (1) CH599454A5 (en))
GB (1) GB1519833A (en))

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4184337A (en) * 1977-06-29 1980-01-22 Bbc Brown Boveri & Company Limited Method and apparatus for regulating a resuperheated steam turbine
US4355514A (en) * 1979-09-28 1982-10-26 Kraftwerk Union Aktiengesellschaft Control device for steam turbines with reheater
US6609361B2 (en) * 2001-07-13 2003-08-26 Pecom Energia, S.A. Primary frequency regulation method in combined-cycle steam turbines
US20070022756A1 (en) * 2005-07-27 2007-02-01 General Electric Company Method and system for controlling a reheat turbine-generator
US20120151922A1 (en) * 2010-12-17 2012-06-21 Alstom Technology Ltd Steam turbine overspeed protection method and system
US9765636B2 (en) 2014-03-05 2017-09-19 Baker Hughes Incorporated Flow rate responsive turbine blades and related methods

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3811279A (en) * 1970-05-26 1974-05-21 Sulzer Ag Shut-off valve for a working medium circuit

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3811279A (en) * 1970-05-26 1974-05-21 Sulzer Ag Shut-off valve for a working medium circuit

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4184337A (en) * 1977-06-29 1980-01-22 Bbc Brown Boveri & Company Limited Method and apparatus for regulating a resuperheated steam turbine
US4355514A (en) * 1979-09-28 1982-10-26 Kraftwerk Union Aktiengesellschaft Control device for steam turbines with reheater
US6609361B2 (en) * 2001-07-13 2003-08-26 Pecom Energia, S.A. Primary frequency regulation method in combined-cycle steam turbines
US20070022756A1 (en) * 2005-07-27 2007-02-01 General Electric Company Method and system for controlling a reheat turbine-generator
US7343744B2 (en) 2005-07-27 2008-03-18 General Electric Company Method and system for controlling a reheat turbine-generator
US20120151922A1 (en) * 2010-12-17 2012-06-21 Alstom Technology Ltd Steam turbine overspeed protection method and system
US9765636B2 (en) 2014-03-05 2017-09-19 Baker Hughes Incorporated Flow rate responsive turbine blades and related methods

Also Published As

Publication number Publication date
JPS5162203A (en) 1976-05-29
DE2542936A1 (de) 1976-04-22
CH599454A5 (en)) 1978-05-31
JPS5624763B2 (en)) 1981-06-08
CA1038474A (en) 1978-09-12
AU8276875A (en) 1977-01-06
GB1519833A (en) 1978-08-02
DE2542936B2 (de) 1977-04-21

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