CA1138657A - Control system for steam turbine plants including turbine bypass systems - Google Patents
Control system for steam turbine plants including turbine bypass systemsInfo
- Publication number
- CA1138657A CA1138657A CA000329117A CA329117A CA1138657A CA 1138657 A CA1138657 A CA 1138657A CA 000329117 A CA000329117 A CA 000329117A CA 329117 A CA329117 A CA 329117A CA 1138657 A CA1138657 A CA 1138657A
- Authority
- CA
- Canada
- Prior art keywords
- pressure
- steam
- turbine
- bypass line
- valve
- 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
Links
Classifications
-
- 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steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating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steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type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steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type the turbines having inter-stage steam heating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
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K13/00—General layout or general methods of operation of complete plants
- F01K13/02—Controlling, e.g. stopping or starting
-
- 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
- F01K7/165—Controlling means specially adapted therefor
Abstract
ABSTRACT OF THE DISCLOSURE
A control system for a steam turbine plant is disclosed which includes a boiler provided with a super heater and a reheater, a first valve mechanism, a high pressure turbine connected to receive steam generated by the boiler through the first valve mechanism and to supply exhaust steam to the reheater, a second valve mechanism, a medium pressure turbine connected to receive reheated steam from the reheater from the second valve mechanism, a high pressure bypass line connected between the first valve mechanism and the reheater, and a low pressure bypass line connected between the second valve mechanism and a condenser the control system also including an electric control system for the low pressure bypass line including a mechanism responsive to the pressure of steam supplied to the medium pressure turbine for controlling the quantity of the steam circulating through the low pressure bypass line.
A control system for a steam turbine plant is disclosed which includes a boiler provided with a super heater and a reheater, a first valve mechanism, a high pressure turbine connected to receive steam generated by the boiler through the first valve mechanism and to supply exhaust steam to the reheater, a second valve mechanism, a medium pressure turbine connected to receive reheated steam from the reheater from the second valve mechanism, a high pressure bypass line connected between the first valve mechanism and the reheater, and a low pressure bypass line connected between the second valve mechanism and a condenser the control system also including an electric control system for the low pressure bypass line including a mechanism responsive to the pressure of steam supplied to the medium pressure turbine for controlling the quantity of the steam circulating through the low pressure bypass line.
Description
TITLE OF THE INVENTION:
CONTROL SYSTEM FOR STEAM TURBINE PLANTS
INCLUDING TURBINE BYPASS SYSTEMS
Field of the Invention:
.
This invention relates to a control system for a steam turbine plant provided with turbine bypass systems, more particularly it is concerned with improvement of a control system for steam turbine plants including turbine bypass systems.
Brief Description of the Drawings:
FIGURE l is a block diagram showing a prior art steam turbine plant with turbine bypass lines;
FIGURE 2 is a graph showing the manner of setting pressure for the prior art turbine bypass system in FIGURE l in which the ordinate shows the pressure in % and the abscissa the quantity of steam led into medium pressure turbine or stage shell pressure in %;
FIGURE 3 is a block diagram showing a prior art control system for a low pressure turbine bypass system;
FIGURE 4 is a graph showi.ng the operating characteristics of reheated steam pressure of the prior art turbine bypass system of FIGURE 3;
FIGURE 5 is a block diagram showing the turbine bypass control system embodying the invention;
FIGURE 6 is a graph showing the operating characterist-ics of reheated steam pressure of a turbine bypass system embodying the present invention;
FIGURE 7 is a graph showing the operating characteristics of the main steam pressure, the quantity of steam led into medium pressure turbine, reheated steam pressure and the opening degree of the valve provided for the low pressure bypass line, respectively, of the present invention.
113E~6~7 Description of the Prior Art:
A recent trend has been to provide a turbine bypass system for an electric power generating plant in the form of a combina-tion of a subcritical pressure natural circulation type boiler and a reheat turbine or a combination of a forced circulation type boiler and a reheat turbine as shown in FIGURE 1. A turbine bypass system utilized in such power~lant includes a high press-ure bypass line 10 and a low pressure bypass line 11.
The high pressure bypass line 10 is connected to the inlet I side of a main stream stop valve 13 for a high pressure turbine 12 and includes a pressure reduclng valve 14 and a desuperheater 15. The lower end of the high pressure bypass line 10 is connected to a cold reheating line 16. The purpose of the high 1.
, I
,
CONTROL SYSTEM FOR STEAM TURBINE PLANTS
INCLUDING TURBINE BYPASS SYSTEMS
Field of the Invention:
.
This invention relates to a control system for a steam turbine plant provided with turbine bypass systems, more particularly it is concerned with improvement of a control system for steam turbine plants including turbine bypass systems.
Brief Description of the Drawings:
FIGURE l is a block diagram showing a prior art steam turbine plant with turbine bypass lines;
FIGURE 2 is a graph showing the manner of setting pressure for the prior art turbine bypass system in FIGURE l in which the ordinate shows the pressure in % and the abscissa the quantity of steam led into medium pressure turbine or stage shell pressure in %;
FIGURE 3 is a block diagram showing a prior art control system for a low pressure turbine bypass system;
FIGURE 4 is a graph showi.ng the operating characteristics of reheated steam pressure of the prior art turbine bypass system of FIGURE 3;
FIGURE 5 is a block diagram showing the turbine bypass control system embodying the invention;
FIGURE 6 is a graph showing the operating characterist-ics of reheated steam pressure of a turbine bypass system embodying the present invention;
FIGURE 7 is a graph showing the operating characteristics of the main steam pressure, the quantity of steam led into medium pressure turbine, reheated steam pressure and the opening degree of the valve provided for the low pressure bypass line, respectively, of the present invention.
113E~6~7 Description of the Prior Art:
A recent trend has been to provide a turbine bypass system for an electric power generating plant in the form of a combina-tion of a subcritical pressure natural circulation type boiler and a reheat turbine or a combination of a forced circulation type boiler and a reheat turbine as shown in FIGURE 1. A turbine bypass system utilized in such power~lant includes a high press-ure bypass line 10 and a low pressure bypass line 11.
The high pressure bypass line 10 is connected to the inlet I side of a main stream stop valve 13 for a high pressure turbine 12 and includes a pressure reduclng valve 14 and a desuperheater 15. The lower end of the high pressure bypass line 10 is connected to a cold reheating line 16. The purpose of the high 1.
, I
,
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~ ~, ", ~ii
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3~6~7 pressure bypass line is to decrease the temperature and pressure of the high temperature and high pressure steam generated by the superheater 18 of a boiler 17. Cooling water from a feedwater pump (not shown) is supplied to the desuperheater 15 through a temperature control valve (not shown). This system permits the boiler to start and supply a certain load independently of the turbine so that the pressure and temperature of the boiler are readily stabilized before starting the turbine. The steam passed ¦
through the high pressure bypass flows back to the reheater 26 of¦
the boiler 17 and is circulated through the boiler 17.
The low pressure bypass line 11 is connected between the inlet side of a reheat stop valve or intercept valve 22 and a condenser 25 via a pressure reducing valve 23 and a desuperheater 24 and operates to reduce the temperature and pressure of the reheated steam. The coolin~ water from a condensate pump (not shown) is supplied to the desuperheater 24 through a temperature ¦
control valve (not shown) for the purpose of preventing thermal deformation of the medium pressure turbine 21 caused by the high pressure, high temperature steam from the reheater 26 during starting. The resulting low temperature low pressure steam is circulated through the boiler 17 together with the condensate from the condenser 25.
11~8657 When the high pressure bypass lines are provided for an electric power plant, the steam generated by boiler 17 flows, during starting, from superheater 18 through high pressure bypass line 10, reheater 26, low pressure bypass line 11, and condenser 25. However, the quantity of steam that flows through this circuit is about 30% of the rated steam flow. During the bypass operation the pressure of the main steam generated by the superheater 18 of the boiler 17 and reheated steam are controlled by pressure reducing valve 14 and 23 provided for the high pressure bypass line 10 and the low pressure bypass line 11, respectively.
During turbine starting, both the main and reheated steams flow into high pressure, medium and low pressure turbines through main steam stop valve 13 and reheat stop valve or intercept valve 22, respecjtively.
As the load of the turbine increases gradually the quantity of the steam supplied to the turbines is increased and the quantity of steam circulating through the high and low bypass line 10 and 11 is decreased correspondingly. Thereafter, the total quantity of the steam generated by the boiler flows through 2Q the turbines. Then pressure reducing valves 1.4 and 23 are fully ":
113~657 closed to terminate the operation of the bypass lines.
During the normal running of the power plant the high and low bypass lines are not used, but when the quantity of the ~ steam flowing into the turbines decreases rapidly due to the load reduction or turbine trip, the turbine bypass systems described above operate to prevent pressure rise of steam and make it possible to continue the operation of the boiler without tripping and starting the turbine quickly.
~ ' le control system of the turbine low pressure bypass systems consists of the pressure reducing valve 23, a pressure control device 30 which controls the pressure reducing valve 23, a first pressure dete~tor 31 which detects the pressure of bypass line 11 and generates a pressure signal to the pressure control apparatus 30 and a second pressure detector 32 which detects the stage shell pressure of the medium pressure turbine 21 at its turbine stage and sends this pressure signal to the pressure control device 30.
The control of the temperature and pressure has been provid-ed by the control system described above. A recent tendency has, however, been to use a electric-hydraulic control system (EHC) for controlling a turbine control valve because of its 113~65'7 quick response characteristic Incorporation of EHC into the control system for the turbine bypass system results in such advantages as a collective control of the turbine plant, cost saving due to common use of the hydraulic system, ease of maintainance and repair and improvement of the control character-istics due to interlocked control of the turbine system and the bypass system.
Normally the bypass-system is designed to handle from 30~
to 50~ or 100% of the rated steam flow due to the characteristics of the boiler 17 or to the fuel, for example, coal~ petroleum or to the various kinds of factors of the turbine plant. As for the steam turbine plant provided with both high pressure and low pressure bypass system, the quantity of the pressure reducing valve 23 provided for thellow pressure bypass line 11 i5 designed in light of aforesaid reasons. The size of the pressure reducing ~
valve 23 depends upon the pressure at the valve 23 inlet. Namely, when the pressure at the valve 23 inlet is high, the small size of the pressure reducing valve 23 is quite enough. But as the load of the turbines increases the quantity of the steam supplied to the turbines is increased and when the quantity of steam flow-¦
ing to the condenser 25 through the low bypass line ll is stopped¦
by the valve 23, the pressure change at the medium pressure turbine 21 inlet becomes great and occurs rapidly. Therefore, this rapid and great pressure change has an adverse influence upon the medium pressure turbine 21 and the reheater 26. Accord-ingly, it is desirable to make the pressure reducing valve 23, provided for the low pressure bypass line 11, small for prevent-ing a rapid and great pressure change at the medium pressureturbine 21 inlet.
The set-point pressure at the pressure reducing valve 23 inlet is set up in consideration of the quantity of the low pressure bypass line 11. When the quantity of the low pressure bypass line 11 is 50% of the rated steam flow of the boiler, the set-point pressure at the pressure reducing valve 23 inlet is generally set up at the pressure at the reheater 26 outlet when the turbine generator runs with 50% load. This allows the inlet pressure be equal to the outlet pressure of the reheater 26 and transfer of the steam which flows from the low pressure bypass line 11 to the medium pressure turbine 21 through the valve 22 without pressure change when the steam which flows the bypass line 11 is transferred to the turbine 21 as the load of the turbine increases. After the steam which flows through the bypass line 11 is transferred to the turbine 21, the pressure set-point of the bypass line 11 is always a little higher than 113~6~
the reheater 26 pressure so that the pressure reducing valve 23 is ready to operate as soon as quick shutdown of the turbine or the load rejection occurs since the reheater 26 pressure increases in proportion to the quantity of the inlet steam of the medium pressure turbine 21. The set-point pressure of the bypass line 11 is proportional to the quantity of the inlet steam of the medium pressure turbine 21, as shown in FIGURE 2. Namely, the set-point pressure of the bypass line 11 is set up at 50% of rated pressure 21 when the pressure of the medium pressure turbine is under 50% of the rated pressure, and is set up at a little higher pressure than the reheater 26 pressure when the pressure of the medium pressure turbine 21 is over 50% of the rated pressure.
FIGURE 3 shows a bloqk diagram of a prior art pressure control device 30 in detail. The pressure control device 30 comprises transducer 35, the output of which is proportional to the pressure detected at the turbine 21 stage by the pressure . detector 32, a high valve priority circuit 36 connected to receive the output from the transducer 35 and output from a pressure setter 37, a comparator 38 where the output is compared withan ~ tput from the pressure detector 31, a PI ccntrol circ-it 11;~8657 which is connected to receive the output from the comparator 38 and a pressure reducing valve control circuit ~0 which is connected to receive the output from the PI control circuit 39 and to supply the signal to the pressure reducing valve 23.
A pressure signal a which is sent from the pressure detec- ¦
tor 32 which detects the actual pressure at the turbine 21 stage is sent to the transducer 35. An output signal b from the transducer 35 and the set signal c from the pressure setter 37 are transferred to the high valve priority circuit 36 to select one of the outputs having the higher valve. Thus, the signal having a higher valve is used to control the low pressure bypass line 11. The pressure signal d from the pressure detector 31 is sent to a comparator 38 to be compared with an output signal e which is produced by the high valve priority circuit 36.
The output signal from the comparator 38 is sent to the pressure reducing valve control circuit 40 via the PI control circuit 39 to control the pressure reducing valve 23. Thus, the inlet pressure of the pressure reducing valve 23 is controlled accord-ing to the characteristics as shown in FIGURE 2.
It is natural that the pressure reducing valve 23 has a 50 capacity of the rated steam flow when the pressure at the valve 23 inlet is 50~ of the rated pressure, or, a 100% capacity of the rated eam flow when the pressure at the valve 23 inlet is 100~
_g_ !
;l :
1 113~fi57 f the rated pressure. It is inconvenient that the pressure reducing valve which has a 100% capacity of the rated steam flow needs to be provided with the desuperheater 15 and the condenser which are as large as are compatible to the valve.
Contrary to the pressure reducing valve described above, it is possible to reduce the size of the pressure reducing valve if the low pressure bypass line 11 is provided with the valve which has a 50% capacity of the rated steam flow when the press-ure at the valve 23 inlet is 100% of the rated pressure. However, when a low pressure bypass line is provided with the pressure re-ducing valve which has a 50~ capacity of the rated steam flow and when the pressure at the valve 23 inlet is 100~ of the rated press _ ure, the quantity of the steam supplied to the medium pressure turbine 21 is gradually increased and the quantity of the steam which flows through the low pressure bypass line 11 is gradually . decreased correspondingly. Thereafter, the reheat stop valve or the intercept valve 22 is fully opened to let the total quantity of the steam generated to flow into the medium pressure turbine 21, and then pressure reducing valve 23 is fully closed to terminate the operation of the bypass lines. Thereupon, when the valve 23 is closed, the pressure of the reheater 26 is changed from 100% of the rated pressure to 50~ because the 113~65q pressure of the reheater 26 is allowed to be equal to the pressure at the turbine inlet, or, 50% of the rated pressure owing to the opening of the reheat stop valve 22. These phenomena are shown in FIGURE 4 and these - 5 rapid pressure changes are undesirable for both of the boiler 17 and the turbine 21.
SUMMARY OF THE INVENTION
Accordingly, this invention seeks to provide a novel control system for a steam turbine plant provided with bypass lines.
This invention also seeks to provide an improved steam turbine control system capable of reducing the size of the pressure reducing valve and removing the rapid pressure change of the reheater.
According to this invention, there is provided a control system for a steam turbine plant which includes a boiler provided with a superheater and a reheater, a first valve means, and a high pressure turbine connected to receive steam generated by the boiler through the first valve means and to supply exhaust steam to the reheater. The control system also includes second valve means, a medium pressure turbine connected to receive reheated steam from the reheater through the second valve means, a condenser, and a high pressure bypass line connected between the first valve means and the reheater. A low pressure bypass line is connected between the second valve means and the condenser, the system further including an electric control system -11386~7 for the low pressure bypass line including means responsive to the pressure of steam supplied to the medium pressure turbine for controlling the quantity of the steam circulating through the low pressure bypass line. Also included in the system is a pressure reducing valve with a pressure contol device for controlling the pressure reducing valve. A first pressure detector detects the pressure of the low pressure bypass line and generates a pressure signal to the pressure control apparatus, and a second pressure detector detects the pressure of the medium pressure turbine and generates a pressure signal to the pressure control device, wherein the pressure control device has a bathtub curved characteristic relationship ; 15 between the pressure setting of the low pressure by-pass line and the quantity of steam flowing into the medium pressure turbine.
......... ~ ~
~13865~7 Various other aspects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate like or corresponding parts throughout the several views.
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS
-The invention will now be described in detail with reference to a preferred embodiment illustrated in the accompanying drawings. FIGURE 5 shows a block diagram of a low pressure bypass line control system wherein a novel control system for a low pressure bypass line system is incorporated into a prior art electro-hydraulic control system (EHC) for controlling a turbine control valve and shows the details of a turbine bypass control circuit for controlling the pressure reducing valve provided with the low pressure bypass line. More particularly, in FIGURE 5, the block diagram of a pressure control device 30 is shown.
Referring to FIGURE 5, the pressure control device 30 Il 113~6~7 I
comprises a first transducer 41, the output signal of which is proportional to an input signal hl from the pressure detector 32, a second transducer 42, the output signal of which is in inverse proportion to input signal h2 from the pressure detector 1 32, a time delay circuit 43, a pressure setter 37 for producing ¦ a pressure setting signal for the low pressure bypass line, a high value priority circuit 36 which compares an output signal jl sent from first transducer 41, an output signal j2 sent from a second transducer 42 via the time delay circuit 43 and an output signal j3 sent from the pressure setter 37, a comparator 38 where .~ signal k sent from a pressure detector 31 is compared with a il signal R sent from the high valve priority circuit 36, a PI con-trol circuit 39 and a pressure reducing valve control circuit 40.
~ ' The first transducer 41 sends an output signal jl which is proportional to an input signal hl from the pressure detector ¦ 32 which detects the stage shell pressure of the medium pressure turbine 21 to the high value priority circuit 36. The second ~ transducer 42 sends an output signal j2 which is in inverse pro-j portion to an input signal h2 from the pressure detector 32 which 20 ' detects the stage shell pressure of the medium pressure turbine 21 to the high value priority circuit 36 through the time delay 1, ~. ,, ~13E~657 circuit 43. As regards the inverse proportion of the second transducer 42, such has the following characteristics. When the stage shell pressure of the medium pressure turbine is "0", that is, when the quantity of steam flowing into the medium ~ pressure turbine is "0", the output singal is "100", and when the stage shell pressure of the medium pressure turbine is 50% of the rated pressure, that is, when the steam flows into the medium pressure turbine to the full extent of its capacity, the output signal is "0". The high value priority circuit 36 compares the output signals, i.e.output signal jl from the first transducer 41, output signal j2 from the second transducer 42 through the time delay circuit 43 and an output signal j3 from the pressure setter 37, selects the signal having the highest value Il and sends it to the comparator 38.The comparator 38 compares 15 1I the signal k from the pressure detector 31 with the signal ~ from the high value pr:iority circuit 36. When signals k and ~ are not equal, a deviation or error signal is sent to the pressure reducing valve control circuit 40 through the PI control circuit ,, 39. The pressure detector 31 detects the pressure of the low 20~ pressure bypass line 11. The time delay circuit 43 is constructed to delay the changed pressure setting of the low pressure bypass line in order to remove the influence brought about in case the operation of the pressure reducing valve 23 and the change of I its pressure setting occur simultaneously when the quantity of steam flowing into the medium pressure turbine 21 is changed.
l!
, I ~13~65 Il The pressure control device 10 is thus constructe~ that whe~
the output signal j2 from the second transducer 42 is directly ¦ communicated to high value priority circuit 36, that is, in case the time delay circuit 43 is set aside, the pressure setting ¦ signal Q sent to the comparator 38 has a kind of "bathtub" curve as shown in FIGURE 6.
The pressure setting of the low pressure bypass line is made in the following manner. In case the quantity of steam flowing into the medium pressure turbine 21 increases until 25% of the rated pressure, the output signal j2 is the highest of all the output signals jl, j2, j3. Therefore, the pressure setting value of the low pressure bypass line is set up at the value designated by output signal j2. In case the quantity of steam flowing into l the medium pressure turbine 21 increases from 25% of the rated pressure to 50% of the rated pressure, or to the point that the quantity of steam flowing into the medium pressure turbine is O, the output signal j3 is the highest of all the output signals jl, j2, j3D Therefore, the pressure bypass line is set up at the value designated by output signal j3. Furthermore, in case the quantity of steam flowing the medium pressure turbine 21 increases until 100~ of the rated pressure, the output signal jl i is the highest of all the output signals jl, j2, j3. Therefore, the pressure setting value of the low pressure bypass line is set up at the value designated by output signal jl, or, a little ~' , ~3 ~
.~ I !
~L13865~7 ., I higher value than actual reheated steam pressure detected by the ¦~ pressure detector 32.
Il I By controlling pressure setting of the low pressure bypass ¦ line as described above, it is possible to adopt the pressure ~ reducing valve which has a 50~ capacity of the rated steam flow when the pressure at the valve inlet is 100% of the rated press-ure. In case the quantity of steam flowing into the low pressure bypass line decreases as the quantity of steam flowing into the ~ medium pressure turbine increases, the pressure reducing valve lO ¦ is able to make a sufficient quantity of steam flow through the bypass even if the pressure setting of the bypass falls. Further-more, when the operation of the low pressure bypass line is over, or the pressure reducing valve 23 is closed, a rapid pressure change at the medium pressure turbine 12 inlet does not occur because the pressure setting valve of the reheater 26 is 50% of rated pressure.
The operation of the control system of this invention will ! now be described with reference to FIGURE 7.
I. From boiler starting to pressure rise:
20 1l From boiler starting to pressure rise, the quantity of steam from boiler increases gradually to be 50~ of rated ll ~3 i 113~6~7 , 1.
steam flow. The steam from the boiler flows into the condenser through a high pressure bypass line and a low pressure bypass line. The reheated steam pressure gets to be 100% of the rated l pressure because the pressure setting of low pressure bypass ¦ line inlet is set up at 50% of the rated pressure. When the quantity of the steam flowing into the turbine increases to 50%
of the rated steam flow, the opening of the low pressure bypass pressure reducing valve 23 is increased to be 100% of its capacitt.
~ II. Turbine starting:
10lll As the turbine starts, the main steam stop valve 13 and ,j reheat stop valve 22 control the quantities of the main steam and ~ the reheated steam respectively. The quantity of steam flowing '~ into medium pressure turbine increases gradually.
I III. Turbine loading 15l As the turbine load increases the quantity of main steam is increased by main steam stop valve 13 and the reheat stop valve 22. The pressure setting value of the low pressure ' bypass line is decreased as shown in FI5URE 6 because the stage I shell pressure of the medium pressure turbine 21 is increased as 20l the quantity of steam flowing into medium pressure turbine :i .j 'l l 113~65~
increases~ As the quantity of main steam increases, the quantity of steam flowing into the low pressure bypass line is decreased.
But the opening degree of the low pressure bypass pressure reduc-l ing valve 23 is still controlled in the state of 100% of its I capacity because the pressure of the pressure reducing valve 23 l inlet is decreased.
When the quantity of steam flowing into the medium pressure turbine 21 increases to the extent of 25% of the rated steam ll flow, the pressure setting valve of the low pressure bypass line 10l¦ 11 is set up at 50% of the rated pressure. Thereafter, the pressure setting value is controlled as a constant. Furthermore, as the quantity of steam flowing into the medium pressure turbine ¦ 21 increases, the opening degree of the pressure reducing valve 1 21 of the low pressure bypass line is decreased.
15 ! IV. Turbine bypass running:
When the load increases under these conditions, as the opening of the reheat stop valve increases, opening of the low pressure bypass pressure reducing valve 23 decreases. The con-ll trol of the turbine bypass system becomes inoperative and the 20 1l normal running of the turbine using reheated steam commences.
Thereafter, the reheated pressure increases in proportion to the l l quantity of steam flowing into the medium pressure turbine 21.
When the pressure reducing valve 23 is fully closed, rapid ¦ pressure change is not brought about because the reheat pressure is 50% of the rated pressure. During normal operation the pressure set-point of the low pressure bypass line 11 is always a little higher than the actual reheat pressure so that the by-pass valve remains closed and is ready to control the reheat pressure.
V. Interruption of the turbine load:
Due to the rapid closure of the main stream stop valve 13 and reheat stop valve 22, the pressures of the main steam and the reheat steam generated by the boiler 17 increase so ¦ that the high pressure bypass pressure reducing valve 14 and ¦, the low pressure bypass pressure reducing valve 23 are opened ~uickly.
Il The description above relates to the 50% bypass system.
However, 50~ bypass depends upon the capacity of bypass system.
The characteristic of the second transducer 42 is not always , restricted to the graph as shown in FIGURE 5, but its having 201 an inverse proportion between input signal and output signal results in desirable performance.
~3' , ~¦ Thus, according to this invention a turbine bypass control system for controlling the turbine bypass lines is incorporated in a conventional main control system which controls the main l steam stop valve and reheat stop valve so that it is possible 1 to provide an overall control of the turbine plant. Accordingly, it is possible to improve the control characteristics, to reduce the capacity of the low pressure bypass pressure reducing valve, the pressure change when the bypass running is complete and the cost of the valve.
., .
10~ Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings.
It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as apeciflcall~ described herein.
:
~' . . .
through the high pressure bypass flows back to the reheater 26 of¦
the boiler 17 and is circulated through the boiler 17.
The low pressure bypass line 11 is connected between the inlet side of a reheat stop valve or intercept valve 22 and a condenser 25 via a pressure reducing valve 23 and a desuperheater 24 and operates to reduce the temperature and pressure of the reheated steam. The coolin~ water from a condensate pump (not shown) is supplied to the desuperheater 24 through a temperature ¦
control valve (not shown) for the purpose of preventing thermal deformation of the medium pressure turbine 21 caused by the high pressure, high temperature steam from the reheater 26 during starting. The resulting low temperature low pressure steam is circulated through the boiler 17 together with the condensate from the condenser 25.
11~8657 When the high pressure bypass lines are provided for an electric power plant, the steam generated by boiler 17 flows, during starting, from superheater 18 through high pressure bypass line 10, reheater 26, low pressure bypass line 11, and condenser 25. However, the quantity of steam that flows through this circuit is about 30% of the rated steam flow. During the bypass operation the pressure of the main steam generated by the superheater 18 of the boiler 17 and reheated steam are controlled by pressure reducing valve 14 and 23 provided for the high pressure bypass line 10 and the low pressure bypass line 11, respectively.
During turbine starting, both the main and reheated steams flow into high pressure, medium and low pressure turbines through main steam stop valve 13 and reheat stop valve or intercept valve 22, respecjtively.
As the load of the turbine increases gradually the quantity of the steam supplied to the turbines is increased and the quantity of steam circulating through the high and low bypass line 10 and 11 is decreased correspondingly. Thereafter, the total quantity of the steam generated by the boiler flows through 2Q the turbines. Then pressure reducing valves 1.4 and 23 are fully ":
113~657 closed to terminate the operation of the bypass lines.
During the normal running of the power plant the high and low bypass lines are not used, but when the quantity of the ~ steam flowing into the turbines decreases rapidly due to the load reduction or turbine trip, the turbine bypass systems described above operate to prevent pressure rise of steam and make it possible to continue the operation of the boiler without tripping and starting the turbine quickly.
~ ' le control system of the turbine low pressure bypass systems consists of the pressure reducing valve 23, a pressure control device 30 which controls the pressure reducing valve 23, a first pressure dete~tor 31 which detects the pressure of bypass line 11 and generates a pressure signal to the pressure control apparatus 30 and a second pressure detector 32 which detects the stage shell pressure of the medium pressure turbine 21 at its turbine stage and sends this pressure signal to the pressure control device 30.
The control of the temperature and pressure has been provid-ed by the control system described above. A recent tendency has, however, been to use a electric-hydraulic control system (EHC) for controlling a turbine control valve because of its 113~65'7 quick response characteristic Incorporation of EHC into the control system for the turbine bypass system results in such advantages as a collective control of the turbine plant, cost saving due to common use of the hydraulic system, ease of maintainance and repair and improvement of the control character-istics due to interlocked control of the turbine system and the bypass system.
Normally the bypass-system is designed to handle from 30~
to 50~ or 100% of the rated steam flow due to the characteristics of the boiler 17 or to the fuel, for example, coal~ petroleum or to the various kinds of factors of the turbine plant. As for the steam turbine plant provided with both high pressure and low pressure bypass system, the quantity of the pressure reducing valve 23 provided for thellow pressure bypass line 11 i5 designed in light of aforesaid reasons. The size of the pressure reducing ~
valve 23 depends upon the pressure at the valve 23 inlet. Namely, when the pressure at the valve 23 inlet is high, the small size of the pressure reducing valve 23 is quite enough. But as the load of the turbines increases the quantity of the steam supplied to the turbines is increased and when the quantity of steam flow-¦
ing to the condenser 25 through the low bypass line ll is stopped¦
by the valve 23, the pressure change at the medium pressure turbine 21 inlet becomes great and occurs rapidly. Therefore, this rapid and great pressure change has an adverse influence upon the medium pressure turbine 21 and the reheater 26. Accord-ingly, it is desirable to make the pressure reducing valve 23, provided for the low pressure bypass line 11, small for prevent-ing a rapid and great pressure change at the medium pressureturbine 21 inlet.
The set-point pressure at the pressure reducing valve 23 inlet is set up in consideration of the quantity of the low pressure bypass line 11. When the quantity of the low pressure bypass line 11 is 50% of the rated steam flow of the boiler, the set-point pressure at the pressure reducing valve 23 inlet is generally set up at the pressure at the reheater 26 outlet when the turbine generator runs with 50% load. This allows the inlet pressure be equal to the outlet pressure of the reheater 26 and transfer of the steam which flows from the low pressure bypass line 11 to the medium pressure turbine 21 through the valve 22 without pressure change when the steam which flows the bypass line 11 is transferred to the turbine 21 as the load of the turbine increases. After the steam which flows through the bypass line 11 is transferred to the turbine 21, the pressure set-point of the bypass line 11 is always a little higher than 113~6~
the reheater 26 pressure so that the pressure reducing valve 23 is ready to operate as soon as quick shutdown of the turbine or the load rejection occurs since the reheater 26 pressure increases in proportion to the quantity of the inlet steam of the medium pressure turbine 21. The set-point pressure of the bypass line 11 is proportional to the quantity of the inlet steam of the medium pressure turbine 21, as shown in FIGURE 2. Namely, the set-point pressure of the bypass line 11 is set up at 50% of rated pressure 21 when the pressure of the medium pressure turbine is under 50% of the rated pressure, and is set up at a little higher pressure than the reheater 26 pressure when the pressure of the medium pressure turbine 21 is over 50% of the rated pressure.
FIGURE 3 shows a bloqk diagram of a prior art pressure control device 30 in detail. The pressure control device 30 comprises transducer 35, the output of which is proportional to the pressure detected at the turbine 21 stage by the pressure . detector 32, a high valve priority circuit 36 connected to receive the output from the transducer 35 and output from a pressure setter 37, a comparator 38 where the output is compared withan ~ tput from the pressure detector 31, a PI ccntrol circ-it 11;~8657 which is connected to receive the output from the comparator 38 and a pressure reducing valve control circuit ~0 which is connected to receive the output from the PI control circuit 39 and to supply the signal to the pressure reducing valve 23.
A pressure signal a which is sent from the pressure detec- ¦
tor 32 which detects the actual pressure at the turbine 21 stage is sent to the transducer 35. An output signal b from the transducer 35 and the set signal c from the pressure setter 37 are transferred to the high valve priority circuit 36 to select one of the outputs having the higher valve. Thus, the signal having a higher valve is used to control the low pressure bypass line 11. The pressure signal d from the pressure detector 31 is sent to a comparator 38 to be compared with an output signal e which is produced by the high valve priority circuit 36.
The output signal from the comparator 38 is sent to the pressure reducing valve control circuit 40 via the PI control circuit 39 to control the pressure reducing valve 23. Thus, the inlet pressure of the pressure reducing valve 23 is controlled accord-ing to the characteristics as shown in FIGURE 2.
It is natural that the pressure reducing valve 23 has a 50 capacity of the rated steam flow when the pressure at the valve 23 inlet is 50~ of the rated pressure, or, a 100% capacity of the rated eam flow when the pressure at the valve 23 inlet is 100~
_g_ !
;l :
1 113~fi57 f the rated pressure. It is inconvenient that the pressure reducing valve which has a 100% capacity of the rated steam flow needs to be provided with the desuperheater 15 and the condenser which are as large as are compatible to the valve.
Contrary to the pressure reducing valve described above, it is possible to reduce the size of the pressure reducing valve if the low pressure bypass line 11 is provided with the valve which has a 50% capacity of the rated steam flow when the press-ure at the valve 23 inlet is 100% of the rated pressure. However, when a low pressure bypass line is provided with the pressure re-ducing valve which has a 50~ capacity of the rated steam flow and when the pressure at the valve 23 inlet is 100~ of the rated press _ ure, the quantity of the steam supplied to the medium pressure turbine 21 is gradually increased and the quantity of the steam which flows through the low pressure bypass line 11 is gradually . decreased correspondingly. Thereafter, the reheat stop valve or the intercept valve 22 is fully opened to let the total quantity of the steam generated to flow into the medium pressure turbine 21, and then pressure reducing valve 23 is fully closed to terminate the operation of the bypass lines. Thereupon, when the valve 23 is closed, the pressure of the reheater 26 is changed from 100% of the rated pressure to 50~ because the 113~65q pressure of the reheater 26 is allowed to be equal to the pressure at the turbine inlet, or, 50% of the rated pressure owing to the opening of the reheat stop valve 22. These phenomena are shown in FIGURE 4 and these - 5 rapid pressure changes are undesirable for both of the boiler 17 and the turbine 21.
SUMMARY OF THE INVENTION
Accordingly, this invention seeks to provide a novel control system for a steam turbine plant provided with bypass lines.
This invention also seeks to provide an improved steam turbine control system capable of reducing the size of the pressure reducing valve and removing the rapid pressure change of the reheater.
According to this invention, there is provided a control system for a steam turbine plant which includes a boiler provided with a superheater and a reheater, a first valve means, and a high pressure turbine connected to receive steam generated by the boiler through the first valve means and to supply exhaust steam to the reheater. The control system also includes second valve means, a medium pressure turbine connected to receive reheated steam from the reheater through the second valve means, a condenser, and a high pressure bypass line connected between the first valve means and the reheater. A low pressure bypass line is connected between the second valve means and the condenser, the system further including an electric control system -11386~7 for the low pressure bypass line including means responsive to the pressure of steam supplied to the medium pressure turbine for controlling the quantity of the steam circulating through the low pressure bypass line. Also included in the system is a pressure reducing valve with a pressure contol device for controlling the pressure reducing valve. A first pressure detector detects the pressure of the low pressure bypass line and generates a pressure signal to the pressure control apparatus, and a second pressure detector detects the pressure of the medium pressure turbine and generates a pressure signal to the pressure control device, wherein the pressure control device has a bathtub curved characteristic relationship ; 15 between the pressure setting of the low pressure by-pass line and the quantity of steam flowing into the medium pressure turbine.
......... ~ ~
~13865~7 Various other aspects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate like or corresponding parts throughout the several views.
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS
-The invention will now be described in detail with reference to a preferred embodiment illustrated in the accompanying drawings. FIGURE 5 shows a block diagram of a low pressure bypass line control system wherein a novel control system for a low pressure bypass line system is incorporated into a prior art electro-hydraulic control system (EHC) for controlling a turbine control valve and shows the details of a turbine bypass control circuit for controlling the pressure reducing valve provided with the low pressure bypass line. More particularly, in FIGURE 5, the block diagram of a pressure control device 30 is shown.
Referring to FIGURE 5, the pressure control device 30 Il 113~6~7 I
comprises a first transducer 41, the output signal of which is proportional to an input signal hl from the pressure detector 32, a second transducer 42, the output signal of which is in inverse proportion to input signal h2 from the pressure detector 1 32, a time delay circuit 43, a pressure setter 37 for producing ¦ a pressure setting signal for the low pressure bypass line, a high value priority circuit 36 which compares an output signal jl sent from first transducer 41, an output signal j2 sent from a second transducer 42 via the time delay circuit 43 and an output signal j3 sent from the pressure setter 37, a comparator 38 where .~ signal k sent from a pressure detector 31 is compared with a il signal R sent from the high valve priority circuit 36, a PI con-trol circuit 39 and a pressure reducing valve control circuit 40.
~ ' The first transducer 41 sends an output signal jl which is proportional to an input signal hl from the pressure detector ¦ 32 which detects the stage shell pressure of the medium pressure turbine 21 to the high value priority circuit 36. The second ~ transducer 42 sends an output signal j2 which is in inverse pro-j portion to an input signal h2 from the pressure detector 32 which 20 ' detects the stage shell pressure of the medium pressure turbine 21 to the high value priority circuit 36 through the time delay 1, ~. ,, ~13E~657 circuit 43. As regards the inverse proportion of the second transducer 42, such has the following characteristics. When the stage shell pressure of the medium pressure turbine is "0", that is, when the quantity of steam flowing into the medium ~ pressure turbine is "0", the output singal is "100", and when the stage shell pressure of the medium pressure turbine is 50% of the rated pressure, that is, when the steam flows into the medium pressure turbine to the full extent of its capacity, the output signal is "0". The high value priority circuit 36 compares the output signals, i.e.output signal jl from the first transducer 41, output signal j2 from the second transducer 42 through the time delay circuit 43 and an output signal j3 from the pressure setter 37, selects the signal having the highest value Il and sends it to the comparator 38.The comparator 38 compares 15 1I the signal k from the pressure detector 31 with the signal ~ from the high value pr:iority circuit 36. When signals k and ~ are not equal, a deviation or error signal is sent to the pressure reducing valve control circuit 40 through the PI control circuit ,, 39. The pressure detector 31 detects the pressure of the low 20~ pressure bypass line 11. The time delay circuit 43 is constructed to delay the changed pressure setting of the low pressure bypass line in order to remove the influence brought about in case the operation of the pressure reducing valve 23 and the change of I its pressure setting occur simultaneously when the quantity of steam flowing into the medium pressure turbine 21 is changed.
l!
, I ~13~65 Il The pressure control device 10 is thus constructe~ that whe~
the output signal j2 from the second transducer 42 is directly ¦ communicated to high value priority circuit 36, that is, in case the time delay circuit 43 is set aside, the pressure setting ¦ signal Q sent to the comparator 38 has a kind of "bathtub" curve as shown in FIGURE 6.
The pressure setting of the low pressure bypass line is made in the following manner. In case the quantity of steam flowing into the medium pressure turbine 21 increases until 25% of the rated pressure, the output signal j2 is the highest of all the output signals jl, j2, j3. Therefore, the pressure setting value of the low pressure bypass line is set up at the value designated by output signal j2. In case the quantity of steam flowing into l the medium pressure turbine 21 increases from 25% of the rated pressure to 50% of the rated pressure, or to the point that the quantity of steam flowing into the medium pressure turbine is O, the output signal j3 is the highest of all the output signals jl, j2, j3D Therefore, the pressure bypass line is set up at the value designated by output signal j3. Furthermore, in case the quantity of steam flowing the medium pressure turbine 21 increases until 100~ of the rated pressure, the output signal jl i is the highest of all the output signals jl, j2, j3. Therefore, the pressure setting value of the low pressure bypass line is set up at the value designated by output signal jl, or, a little ~' , ~3 ~
.~ I !
~L13865~7 ., I higher value than actual reheated steam pressure detected by the ¦~ pressure detector 32.
Il I By controlling pressure setting of the low pressure bypass ¦ line as described above, it is possible to adopt the pressure ~ reducing valve which has a 50~ capacity of the rated steam flow when the pressure at the valve inlet is 100% of the rated press-ure. In case the quantity of steam flowing into the low pressure bypass line decreases as the quantity of steam flowing into the ~ medium pressure turbine increases, the pressure reducing valve lO ¦ is able to make a sufficient quantity of steam flow through the bypass even if the pressure setting of the bypass falls. Further-more, when the operation of the low pressure bypass line is over, or the pressure reducing valve 23 is closed, a rapid pressure change at the medium pressure turbine 12 inlet does not occur because the pressure setting valve of the reheater 26 is 50% of rated pressure.
The operation of the control system of this invention will ! now be described with reference to FIGURE 7.
I. From boiler starting to pressure rise:
20 1l From boiler starting to pressure rise, the quantity of steam from boiler increases gradually to be 50~ of rated ll ~3 i 113~6~7 , 1.
steam flow. The steam from the boiler flows into the condenser through a high pressure bypass line and a low pressure bypass line. The reheated steam pressure gets to be 100% of the rated l pressure because the pressure setting of low pressure bypass ¦ line inlet is set up at 50% of the rated pressure. When the quantity of the steam flowing into the turbine increases to 50%
of the rated steam flow, the opening of the low pressure bypass pressure reducing valve 23 is increased to be 100% of its capacitt.
~ II. Turbine starting:
10lll As the turbine starts, the main steam stop valve 13 and ,j reheat stop valve 22 control the quantities of the main steam and ~ the reheated steam respectively. The quantity of steam flowing '~ into medium pressure turbine increases gradually.
I III. Turbine loading 15l As the turbine load increases the quantity of main steam is increased by main steam stop valve 13 and the reheat stop valve 22. The pressure setting value of the low pressure ' bypass line is decreased as shown in FI5URE 6 because the stage I shell pressure of the medium pressure turbine 21 is increased as 20l the quantity of steam flowing into medium pressure turbine :i .j 'l l 113~65~
increases~ As the quantity of main steam increases, the quantity of steam flowing into the low pressure bypass line is decreased.
But the opening degree of the low pressure bypass pressure reduc-l ing valve 23 is still controlled in the state of 100% of its I capacity because the pressure of the pressure reducing valve 23 l inlet is decreased.
When the quantity of steam flowing into the medium pressure turbine 21 increases to the extent of 25% of the rated steam ll flow, the pressure setting valve of the low pressure bypass line 10l¦ 11 is set up at 50% of the rated pressure. Thereafter, the pressure setting value is controlled as a constant. Furthermore, as the quantity of steam flowing into the medium pressure turbine ¦ 21 increases, the opening degree of the pressure reducing valve 1 21 of the low pressure bypass line is decreased.
15 ! IV. Turbine bypass running:
When the load increases under these conditions, as the opening of the reheat stop valve increases, opening of the low pressure bypass pressure reducing valve 23 decreases. The con-ll trol of the turbine bypass system becomes inoperative and the 20 1l normal running of the turbine using reheated steam commences.
Thereafter, the reheated pressure increases in proportion to the l l quantity of steam flowing into the medium pressure turbine 21.
When the pressure reducing valve 23 is fully closed, rapid ¦ pressure change is not brought about because the reheat pressure is 50% of the rated pressure. During normal operation the pressure set-point of the low pressure bypass line 11 is always a little higher than the actual reheat pressure so that the by-pass valve remains closed and is ready to control the reheat pressure.
V. Interruption of the turbine load:
Due to the rapid closure of the main stream stop valve 13 and reheat stop valve 22, the pressures of the main steam and the reheat steam generated by the boiler 17 increase so ¦ that the high pressure bypass pressure reducing valve 14 and ¦, the low pressure bypass pressure reducing valve 23 are opened ~uickly.
Il The description above relates to the 50% bypass system.
However, 50~ bypass depends upon the capacity of bypass system.
The characteristic of the second transducer 42 is not always , restricted to the graph as shown in FIGURE 5, but its having 201 an inverse proportion between input signal and output signal results in desirable performance.
~3' , ~¦ Thus, according to this invention a turbine bypass control system for controlling the turbine bypass lines is incorporated in a conventional main control system which controls the main l steam stop valve and reheat stop valve so that it is possible 1 to provide an overall control of the turbine plant. Accordingly, it is possible to improve the control characteristics, to reduce the capacity of the low pressure bypass pressure reducing valve, the pressure change when the bypass running is complete and the cost of the valve.
., .
10~ Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings.
It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as apeciflcall~ described herein.
:
~' . . .
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A control system for a steam turbine plant comprising:
a boiler provided with a superheater and a reheater;
a first valve means;
a high pressure turbine connected to receive steam generated by the boiler through said first valve means and to supply exhaust steam to the reheater;
second valve means;
a medium pressure turbine connected to receive reheated steam from said reheater through said second valve means;
a condenser;
a high pressure bypass line connected between said first valve means and said reheater;
a low pressure bypass line connected between the second valve means and said condenser, said control system further com-prising an electric control system for said low pressure bypass line including means responsive to the pressure of steam supplied to the medium pressure turbine for controlling the quantity of the steam circulating through said low pressure bypass line, a pressure reducing valve, a pressure control device for controlling said pressure reducing valve, a first pressure detector for detecting the pressure of said low pressure bypass line and for generating a pressure signal to said pressure control apparatus and a second pressure detector for detecting the pressure of said medium pressure turbine and for generating a pressure signal to said pressure control device wherein said pressure control device has a bathtub curved characteristic relationship between the pressure setting of the low pressure bypass line and the quantity of steam flowing into the medium pressure turbine.
2. The control system according to Claim 1 said pressure control device further comprising:
a comparator;
a PI control circuit;
a pressure reducing control valve circuit to control said pressure reducing valve;
a high value priority circuit;
a first transducer which generates signals proportionally to signals from said second pressure detector to said high value priority circuit;
a second transducer unit which generates signals inversely proportional to signals from said second pressure detector to said high value priority circuit ; and, a pressure setter member which generates a signal to said high value priority circuit wherein said high value priority circuit compares signals from the first transducer unit, the second transducer unit and the pressure setter and generates
a boiler provided with a superheater and a reheater;
a first valve means;
a high pressure turbine connected to receive steam generated by the boiler through said first valve means and to supply exhaust steam to the reheater;
second valve means;
a medium pressure turbine connected to receive reheated steam from said reheater through said second valve means;
a condenser;
a high pressure bypass line connected between said first valve means and said reheater;
a low pressure bypass line connected between the second valve means and said condenser, said control system further com-prising an electric control system for said low pressure bypass line including means responsive to the pressure of steam supplied to the medium pressure turbine for controlling the quantity of the steam circulating through said low pressure bypass line, a pressure reducing valve, a pressure control device for controlling said pressure reducing valve, a first pressure detector for detecting the pressure of said low pressure bypass line and for generating a pressure signal to said pressure control apparatus and a second pressure detector for detecting the pressure of said medium pressure turbine and for generating a pressure signal to said pressure control device wherein said pressure control device has a bathtub curved characteristic relationship between the pressure setting of the low pressure bypass line and the quantity of steam flowing into the medium pressure turbine.
2. The control system according to Claim 1 said pressure control device further comprising:
a comparator;
a PI control circuit;
a pressure reducing control valve circuit to control said pressure reducing valve;
a high value priority circuit;
a first transducer which generates signals proportionally to signals from said second pressure detector to said high value priority circuit;
a second transducer unit which generates signals inversely proportional to signals from said second pressure detector to said high value priority circuit ; and, a pressure setter member which generates a signal to said high value priority circuit wherein said high value priority circuit compares signals from the first transducer unit, the second transducer unit and the pressure setter and generates
Claim 2 - cont'd ...
the highest signal to said comparator such that said signal from said first pressure detector is compared with said signal from the high value priority circuit and is communicated to said pressure reducing valve control circuit via said PI control circuit.
the highest signal to said comparator such that said signal from said first pressure detector is compared with said signal from the high value priority circuit and is communicated to said pressure reducing valve control circuit via said PI control circuit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP53069045A JPS5820363B2 (en) | 1978-06-08 | 1978-06-08 | steam turbine equipment |
| JP69045/78 | 1978-06-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1138657A true CA1138657A (en) | 1983-01-04 |
Family
ID=13391210
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000329117A Expired CA1138657A (en) | 1978-06-08 | 1979-06-05 | Control system for steam turbine plants including turbine bypass systems |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5820363B2 (en) |
| AU (1) | AU537365B2 (en) |
| CA (1) | CA1138657A (en) |
| CH (1) | CH630440A5 (en) |
| DE (1) | DE2923288A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113568443A (en) * | 2021-07-28 | 2021-10-29 | 哈尔滨沃华智能发电设备有限公司 | Method for controlling pressure behind valve of low-pressure bypass control system |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62206203A (en) * | 1986-03-07 | 1987-09-10 | Hitachi Ltd | Operation control method for steam turbine |
| AU628916B2 (en) * | 1989-02-03 | 1992-09-24 | Hitachi Limited | Ni-Cr-Mo-V low alloy steel and a rotor shaft fabricated therefrom |
| EP1854964A1 (en) * | 2006-05-10 | 2007-11-14 | Siemens Aktiengesellschaft | Use of the steam turbine for primary frequency control in power generating plants |
| EP2685055A1 (en) * | 2012-07-12 | 2014-01-15 | Siemens Aktiengesellschaft | Method for supporting a network frequency |
| CN103352733B (en) * | 2013-06-29 | 2016-02-10 | 内蒙古电力勘测设计院有限责任公司 | The longitudinal direction of the steam turbine building of 350MW level NCB unit is arranged |
| CN104533549B (en) * | 2014-12-25 | 2016-06-29 | 中国电力工程顾问集团华东电力设计院有限公司 | Three grades of Bypass Control System and control method thereof |
| CN112343679B (en) * | 2020-11-05 | 2022-09-23 | 华能国际电力股份有限公司玉环电厂 | Control method for deep peak shaving and shutdown of unit |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS538001A (en) * | 1976-07-09 | 1978-01-25 | Mitsubishi Electric Corp | Fm receivers |
-
1978
- 1978-06-08 JP JP53069045A patent/JPS5820363B2/en not_active Expired
-
1979
- 1979-06-05 CA CA000329117A patent/CA1138657A/en not_active Expired
- 1979-06-05 AU AU47751/79A patent/AU537365B2/en not_active Expired
- 1979-06-08 DE DE19792923288 patent/DE2923288A1/en active Granted
- 1979-06-08 CH CH535179A patent/CH630440A5/en not_active IP Right Cessation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113568443A (en) * | 2021-07-28 | 2021-10-29 | 哈尔滨沃华智能发电设备有限公司 | Method for controlling pressure behind valve of low-pressure bypass control system |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS54160902A (en) | 1979-12-20 |
| JPS5820363B2 (en) | 1983-04-22 |
| CH630440A5 (en) | 1982-06-15 |
| DE2923288A1 (en) | 1979-12-20 |
| AU537365B2 (en) | 1984-06-21 |
| AU4775179A (en) | 1979-12-13 |
| DE2923288C2 (en) | 1988-09-15 |
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