Electric power plant system and method for operating a steam turbine especially of the nuclear type with electronic reheat control of a cycle steam reheater

Claim 2

A reheater control system for a reheater system in a steam turbine generating system comprising: control means having, temperature reference means, means for detecting temperature, comparator means, means for generating a ramp, means for generating a function having an input connected to an output of said ramp generator means, means for valving a flow of steam through said reheater system, means for moving said reheater valVing means from one position to another, an output of said function generator means connected to an input for said moving means, whereby said moving means is controlled by a signal from said function generator means, said function generator means having transfer characteristics matched with the input/output characteristics of said valving means, such that, said valving means is opened in a manner producing a substantially linear increase of inlet pressure with time when an output of said temperature reference means is connected to an input of said ramp generator means.

Claim 3

The reheater control system as defined in claim 2 including, load control means adapted for placing said control means in a plurality of modes.

Claim 4

The reheater control system as defined in claim 2 including computer means for automatically switching said control means from one mode to another.

Claim 5

The reheater control system as defined in claim 2 wherein said plurality of modes includes a first mode adapted to control said means for moving said reheater valving means over a fixed period of time so as to vary the temperature substantially linearly at a low pressure inlet to said steam turbine generating system from a first predetermined temperature to a second predetermined temperature, over a predetermined period of time.

Claim 6

The reheater control system as defined in claim 4 including computer means for automatically switching said control means from one mode to another.

Claim 7

The reheater control system as defined in claim 4 wherein said control means has a second mode adapted to maintain a temperature at the hottest low pressure turbine inlet at a predetermined temperature.

Claim 8

The reheater control system as defined in claim 6 including computer means for automatically switching said control means from one mode to another.

Claim 9

The reheater control system as defined in claim 6 wherein said temperature detection means comprises thermocouple sensor means at the low pressure inlets of said steam turbine generating system, said thermocouple sensor means generating signals representing temperatures at said inlets, and having auctioneering diode logic means for providing an electrical signal representative of the highest detected inlet temperature.

Claim 10

The reheater control system as defined in claim 8 including computer means for automatically switching said control means from one mode to another.

Claim 11

The reheater control system as defined in claim 8 wherein said control means has a third mode adapted to bring heating steam quickly to a level corresponding to a predetermined low pressure inlet temperature.

Claim 12

In a turbine system for generating electrical energy, having at least one high pressure turbine and a plurality of low pressure turbines driven by steam from a nuclear powered steam source, a reheater system for reheating cycle steam which is passed through said at least one high pressure turbine before it is passed into and through one of said low pressure turbines, comprising: a. reheater means, receiving heating steam from said steam source for reheating relatively wet cycle steam from said at least one high pressure turbine and producing superheated and relatively dry steam suitable for passage to one of said low pressure turbines; b. temperature detection means, for detecting the turbine temperatures near the steam inlets of said low pressure turbines, and generating signals representing said turbine temperatures; c. reheater control means, receiving said signals, and having logic for deriving that one of said signals representing the highest of said temperatures, comparator circuitry for comparing said one signal with a temperature reference signal, and a plurality of control modes in each of which the amount of heating steam passing through said reheater means is controlled according to a separate predetermined function; and d. mode control means, adapted for placing said control means in one of said plurality of modes.

Claim 13

In a turbine system for generating electrical energy, having at least one high pressure turbine and a plurality of low pressure turbines driven by steam from a nuclear powered steam source, a reheater system for reheating cycle steam which is passed through said at least one high pressure turbine before it is passed into and through one of said low pressure turbines, comprising: a. reheater means, receiving heating steam from said steam source for reheating relatively wet cycle steam from said at least one high pressure turbine and producing superheated and relatively dry steam suitable for passage to one of said low pressure turbines; b. temperature detection means, for detecting the turbine temperatures near the steam inlets of said low pressure turbines, and generating signals representing said turbine temperatures; c. reheater control means, receiving said signals, and having logic for deriving that one of said signals representing the highest of said temperatures, comparator circuitry for comparing said one signal with a temperature reference signal, and a plurality of control modes in each of which the amount of heating steam passing through said reheater means is controlled according to a separate predetermined function; and d. mode control means, adapted for placing said control means in one of said plurality of modes.

Claim 14

The reheater sysTem as described in claim 11 wherein said mode control means is switchably connected to programmable computer means for continuously calculating the desired mode of control of said reheater control means, and comprising a data network for continuously monitoring physical operating parameters in said low pressure sections of said turbine and for transmitting to said computer means data representing said monitored parameters.

Claim 15

The reheater system as described in claim 11, wherein said reheater control means has a first mode adapted to control said heating steam over a fixed period of time so as to vary the temperature at said low pressure inlets from a first predetermined temperature substantially linearly to a second predetermined temperature, over a predetermined time period.

Claim 16

The apparatus as described in claim 13 wherein said reheater control means has a second mode adapted to maintain the temperature of the hottest low pressure turbine inlet at a predetermined temperature.

Claim 17

The apparatus as described in claim 1, wherein said temperature detection means comprises thermocouple sensors at each of said lower pressure inlets, thermocouple amplifiers connected to an amplifying the signals from each of said thermocouples, and having auctioneering diode logic means for providing an electrical signal representative of the highest detected inlet temperature.

Claim 18

The apparatus as described in claim 13, wherein said reheater control means has a third mode adapted to bring said heating steam quickly to a level corresponding to a predetermined low pressure inlet temperature.

Claim 19

The reheater system as described in claim 1 wherein said reheater control means comprises a switching circuit operatively connected to said comparator circuit, said switching circuit operatively connected to said mode control means to hold said reheater control means in a temperature limit mode and out of all other of said plurality of modes when said highest temperature exceeds said reference temperature.

Claim 20

In a nuclear powered turbine system, having at least one high pressure turbine and at least one low pressure turbine, with steam generated in a steam generator being first passed through said at least one high pressure turbine and exhausted therefrom, and then passed into said at least one low pressure turbine, with a reheater interposed between said high pressure turbine and said low pressure turbine for reheating the exhausted and relatively wet steam from said high pressure turbine and to produce superheated and relatively dried steam for passage to said low pressure turbine, said reheater deriving its heating energy from relatively dry reheating steam obtained directly from said steam generator, the amount of said reheating steam being controlled by a pneumatically operated reheater valve positioned between said steam generator and said reheater, said valve being controlled by an electropneumatic transducer which produces output pneumatic signals connected to said reheater valve in response to an input electric signal and having a generally non-linear transfer function, a control system for generating said input electric signal comprising: a. a ramp generator for producing a ramp signal rising substantially linearly with time; b. a function generator, connected to the output of said ramp generator, and having a diode-resistor logic network characterized by a plurality of set points; c. a power amplifier, including an operation amplifier having said function generator connected to its output, said electric signal appearing at the output of said amplifier; d. said function generator cooperating with said power amplifier to provide a straight line-type gain characteristic; e. at least one reference source providing a reference signal switchably connected to said ramp generator, so that when so connected the output of said power amplifier varies in time in a non-linear manner designed to compensate for the non-linear characteristic of the transducer so aS to cause a substantially linear rise in temperature of the reheated steam with time; and f. a zero offset circuit having an output connected to the input of said power amplifier, for producing a live zero output when said reference source is not connected to said ramp generator.

Claim 21

In a nuclear powered turbine system, having at least one high pressure turbine and at least one low pressure turbine, with steam generated in a steam generator being first passed through said at least one high pressure turbine and exhausted therefrom, and then passed into said at least one low pressure turbine, with a reheater interposed between said high pressure turbine and said low pressure turbine for reheating the exhausted and relatively wet steam from said high pressure turbine and to produce superheated and relatively dried steam for passage to said low pressure turbine, said reheater deriving its heating energy from relatively dry reheating steam obtained directly from said steam generator, the amount of said reheating steam being controlled by a pneumatically operated reheater valve positioned between said steam generator and said reheater, said valve being controlled by an electropneumatic transducer which produces output pneumatic signals connected to said reheater valve in response to an input electric signal and having a generally non-linear transfer function, a control system for generating said input electric signal comprising: a. a ramp generator for producing a ramp signal rising substantially linearly with time; b. a function generator, connected to the output of said ramp generator, and having a diode-resistor logic network characterized by a plurality of set points; c. a power amplifier, including an operation amplifier having said function generator connected to its output, said electric signal appearing at the output of said amplifier; d. said function generator cooperating with said power amplifier to provide a straight line-type gain characteristic; e. at least one reference source providing a reference signal switchably connected to said ramp generator, so that when so connected the output of said power amplifier varies in time in a non-linear manner designed to compensate for the non-linear characteristic of the transducer so aS to cause a substantially linear rise in temperature of the reheated steam with time; and f. a zero offset circuit having an output connected to the input of said power amplifier, for producing a live zero output when said reference source is not connected to said ramp generator.

Claim 22

The system as described in claim 18, wherein said turbine system comprises a plurality of low pressure turbine sections, with a reheater interposed between said high pressure turbine and each of said low pressure sections, with reheater valves positioned in the reheating system path of each of said reheaters, said valves being commonly controlled by said transducer, and comprising: a. thermocouple means placed in each of said low pressure sections, for generating temperature signals representing the temperatures of said sections; b. auctioneering means, for auctioneering that temperature signal representing the highest of said section temperatures; c. a first temperature reference source providing a first temperature reference signal; d. comparator means, having said auctioneered signal connected to its input, for comparing two input signals and providing a comparator signal; e. first switch means, for normally connecting said first temperature reference signal to said comparator means input; and f. second switch means, switchably connecting said comparator signal and said reference signal to said ramp generator.

Claim 23

The system as described in claim 19, comprising: a. temperature limit switching circuitry, having said auctioneered signal connected to its input; b. a second temperature reference source providing a second temperature reference signal; and c. said temperature limit switching circuitry operatively connected to said first switch means to cause it to switch said second temperature reference signal into connection with said comparator means input when said auctioneered temperature exceeds a predetermined limit, whereby said comparator signal is of a polarity and magnitude that said amplifier signal causes said reheater valves to close and reduce the amount of reheating steam obtained by said reheaters.

Claim 24

The apparatus as described in claim 20, comprising mode control means, adapted to switchably place said control system into one of a plurality of modes of control, in each of which the amount of heating steam passing through said reheaters is automatically controlled in a separate predetermined manner.

Claim 25

The apparatus as described in claim 21, wherein said temperature limit switching circuitry is operatively connected to said mode control means to hold said control system out of any of said plurality of modes of control when said auctioneered temperature exceeds said predetermined limit and thereafter until it drops to a second predetermined limit.

Claim 26

In a turbine system, having a controllable reheater for reheating steam passed from a high pressure turbine to a low pressure turbine, a control system having an output connected to said reheater for controlling the operation of said reheater so as to control the temperature of the steam passed to said low pressure turbine and accordingly the turbine temperature at the inlet where said reheated steam is received, comprising: a. cold start means for generating a cold start control signal when said control system is switched into a cold start mode, for controlling said reheater over a fixed period of time so as to raise said low pressure turbine inlet temperature from a first predetermined temperature to a second predetermined temperature over a predetermined time period; b. constant temperature means, for generating a constant temperature control signal when said control means is switched into a constant temperature mode, said constant temperature signal automatically maintaining the temperature at said low pressure turbine inlet at a predetermined temperature; c. hot start means, for generating a hot start control signal to quickly raise said low pressure turbiNe inlet to a predetermined temperature when said control system is switched into a hot start mode; d. reset means, for generating a reset control signal to maintain said low pressure turbine inlet at a low temperature when said control system is switched into a reset mode; e. manual control means, adapted so that said control system output can be manually determined when said control system is switched into a manual mode; f. control mode means for switchably connecting said control system into one of said modes; and g. ramp generator means operatively connected as a part of said cold start means when in said cold start mode, as a part of said constant temperature means when in said constant temperature mode, and said hot start means when in said hot start mode.

Claim 27

In a turbine system, having a controllable reheater for reheating steam passed from a high pressure turbine to a low pressure turbine, a control system having an output connected to said reheater for controlling the operation of said reheater so as to control the temperature of the steam passed to said low pressure turbine and accordingly the turbine temperature at the inlet where said reheated steam is received, comprising: a. cold start means for generating a cold start control signal when said control system is switched into a cold start mode, for controlling said reheater over a fixed period of time so as to raise said low pressure turbine inlet temperature from a first predetermined temperature to a second predetermined temperature over a predetermined time period; b. constant temperature means, for generating a constant temperature control signal when said control means is switched into a constant temperature mode, said constant temperature signal automatically maintaining the temperature at said low pressure turbine inlet at a predetermined temperature; c. hot start means, for generating a hot start control signal to quickly raise said low pressure turbiNe inlet to a predetermined temperature when said control system is switched into a hot start mode; d. reset means, for generating a reset control signal to maintain said low pressure turbine inlet at a low temperature when said control system is switched into a reset mode; e. manual control means, adapted so that said control system output can be manually determined when said control system is switched into a manual mode; f. control mode means for switchably connecting said control system into one of said modes; and g. ramp generator means operatively connected as a part of said cold start means when in said cold start mode, as a part of said constant temperature means when in said constant temperature mode, and said hot start means when in said hot start mode.

Claim 28

The control system as described in claim 23 wherein the input of said ramp generator is connected to a constant signal source when said system is in the cold start mode.

Claim 29

The control system as described in claim 24 wherein the input of said ramp generator is connected to a fast rise time network when said system is in the hot start mode.

Claim 30

The control system as described in claim 25 wherein said ramp generator comprises an operational amplifier.

Claim 31

The control system as described in claim 26 wherein the output of said ramp generator is connected to a power amplifier through a function generator, said function generator having a plurality of break points so that when said ramp generator produces a substantially linear ramp output, said power amplifier produces a non-linear output signal.

Claim 32

The control system as described in claim 27 wherein said controllable reheater comprises a pneumatically operated reheater valve and a heat-transfer reheater unit, said reheater valve controllably passing said reheating steam to said reheater unit, and an electropneumatic transducer which actuates said valve, the output of said power amplifier being connected to said transducer.

Claim 33

The apparatus as described in claim 28 wherein said transducer has a non-linear transfer characteristic, and said function generator combines with said transducer to provide a substantially linear overall control characteristic.

Claim 36

The method as described in claim 30 comprises controlling said flow of heating steam over a fixed period of time so as to raise the temperature at said low pressure inlet from a first predetermined temperature substantially linearly to a second predetermined temperature, and over a predetermined time period.

Claim 37

The method as described in claim 31 wherein said first predetermined temperature is about 300*F, said second predetermined temperature is about 500*F, and said predetermined time period is approximately one hour.

Claim 38

The method as described in claim 30, comprising maintaining said inlet temperature within + or - 2.5*F of a fixed temperature.

Claim 39

The method as described in claim 30 comprising simultaneously initiating control of said heating steam and limiting said control signal to a reset level.

Claim 40

The method as described in claim 30 comprising automatically choosing the control mode of operation as a function of analysis of the turbine system operation made by a computer.

Claim 41

The method as described in claim 30 wherein said turbine system comprises at least two low pressure turbine sections, and comprising the step of sensing the temperature at the steam inlet of each of said low pressure sections and generating temperature signals corresponding to said sensed temperatures, and auctioneering said temperature signals to derive an auctioneered signal representing the highest of said temperatures.

Claim 42

In an electronic reheater control system for a steam turbine generating system, for controlling the reheating of steam which is cycled from a high pressure section of said turbine to a low pressure section of said turbine, wherein said reheating steam is controllably passed by a reheater valve, which valve is controlled by a transducer having a non-linear transfer characteristic, the method comprising: a. continuously generating an electric signal which is a non-linear function of the desired low pressure turbine temperature, and which compensates for said non-linear transducer characteristic; b. connecting said electrical signal to said transducer, and generating a pneumatic signal; c. connecting said pneumatic signal to said reheater control valve, thereby controlling the passage of reheating steam; d. measuring the temperature at the inlet of said low pressure turbine section, and generating an electric temperature signal representing said measured temperature; e. comparing said measured temperature signal with a temperature reference signal; f. generating a temperature-error signal as a function of said temperature comparison; and g. generating said control signal as a function of said temperature-error signal.

Claim 43

In an electronic reheater control system for a steam turbine generating system, for controlling the reheating of steam which is cycled from a high pressure section of said turbine to a low pressure section of said turbine, wherein said reheating steam is controllably passed by a reheater valve, which valve is controlled by a transducer having a non-linear transfer characteristic, the method comprising: a. continuously generating an electric signal which is a non-linear function of the desired low pressure turbine temperature, and which compensates for said non-linear transducer characteristic; b. connecting said electrical signal to said transducer, and generating a pneumatic signal; c. connecting said pneumatic signal to said reheater control valve, thereby controlling the passage of reheating steam; d. measuring the temperature at the inlet of said low pressure turbine section, and generating an electric temperature signal representing said measured temperature; e. comparing said measured temperature signal with a temperature reference signal; f. generating a temperature-error signal as a function of said temperature comparison; and g. generating said control signal as a function of said temperature-error signal.

Claim 44

The method as described in claim 37 wherein said temperature reference signal represents a temperature limit, and comprising the steps of: a. comparing said measured temperature signal with a second reference signal representing a temperature lower than said temperature limit by a fixed amount; and b. generating a temperature-error signal such that, said control signal causes said low pressure temperature to be reduced to and maintained at said lower temperature.