CA1070125A - Apparatus for controlling steam turbine plants including steam bypass systems - Google Patents
Apparatus for controlling steam turbine plants including steam bypass systemsInfo
- Publication number
- CA1070125A CA1070125A CA258,463A CA258463A CA1070125A CA 1070125 A CA1070125 A CA 1070125A CA 258463 A CA258463 A CA 258463A CA 1070125 A CA1070125 A CA 1070125A
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- Canada
- Prior art keywords
- valve
- steam
- stop valve
- interception
- steam stop
- Prior art date
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Abstract
Abstract of the Disclosure An apparatus is disclosed for controlling a steam turbine plant which includes steam bypass systems of the type wherein the quantites of the steam flowing into a high pressure turbine with a high pressure bypass line and into a reheated steam turbine with a low pressure bypass line are con-trolled by a main steam stop valve, a steam control valve, a reheated steam stop valve and an interception valve. The apparatus includes an inter-lock for interlocking a control system for the main steam stop valve with a control system for the reheated steam stop valve. A second interlock inter-locks the steam control valve and the interception valve. The second inter-lock includes a speed relay device for controlling the second interlock so as to supply steam to the high pressure and reheated steam turbines at a predetermined ratio, a dash pot, and a low valve priority device responsive to the lower one of the control signal from the speed relay device passed through the dash pot and the control signal from the speed relay device.
This controls the interception valve so as to interlock the main steam stop valve with the reheated steam stop valve and to interlock the steam control valve with the interception valve during starting of the turbine plant.
This controls the interception valve so as to interlock the main steam stop valve with the reheated steam stop valve and to interlock the steam control valve with the interception valve during starting of the turbine plant.
Description
fæS
This invention relates to apparatus for controlling a steam turbine plant including a turbine bypass system wherein a plurality of control valves installed on the inlet sides of high pressure and medium pressure turbines are interlocked with each other to be opened simultaneously at the time of starting the turbines.
In an electric power generating plant of the type comprising a super-critical pressure through flow boiler and a reheating turbine it is usual to employ a so-called turbine bypass system in which, at the time of starting the boiler, a portion of the steam generated by the boiler is passed directly to a condenser instcad of passing it through the turbine.
The turbine bypass system has also been used in a modern electric power generating plant of the type including a subcritical pressure natural circulation boiler and a reheating turbine or a forced circulation boiler and a reheating turbine.
When such turbine bypass systems are applied for a generating plant including a combination of a subcritical natural circulation boiler and a re-heated steam turbine or a combination of a forced circulation boiler and a reheated steam turbine, not only can the restarting of the turbine after inter-ruption of the generator load and a s~oppage of 6 to 8 hours can be performed , 20 effectively but the reheater can be protected as well.
On the other hand, since the pressure of the main steam generated by the boiler and ~hat of the reheated steam generated by the reheater have already built up to predetermined values prior to the starting of the turbine, local excessive heat stresses would be formed in the turbine unless the steam flows were passed to the high pressure turbine and the medium pressure turbine in a suitable ratio before starting the turbine.
According to this invention there is provided apparatus for controll-ing a steam turbine plant including steam bypass systems of the type wherein the quantities of the steam flowing into a high pressure turbine provided with a high pressure bypass line and into a reheated steam turbine provided with a .. -- 1 --:
~ :.
~70~Z5 low pressure bypass line a.re controlled by a main steam s~op valve, a steam . control valve, a reheated steam stop valve and an interception valve, said apparatus comprising first interlocking means for interlocking a control system for the main steam stop valve with a control system for the reheated steam stop valve, and a second interlocking means or interlocking the steam - control valve and the interception valve, the second interlocking means in-cluding a speed relay device for controlling the second interlocking means for supplying steam to the high pressure turbine and the reheated steam tur-bine at a predetermined ratio, a dash pot~ and a low value priority device . 10 responsive to the lower one of the control signal from the speed relay device and passed through the dash pot and the control signal from the speed relay device, thereby controlling the interception valve so as to interlock the . main steam stop valve with the reheated steam stop valve and to interlock the ~ ..
steam control valve with the interception valve during starting of the turbine plant.
In the accompanying drawings, which illustrate a power plant of the relevant type, a prior art control system and exemplary embodiments of the present invention:
: Figure 1 is a diagrammatic representation of a prior art steam electric power generating plant provided with turbine bypass systems;
Figure 2 is a block diagram showing a prior art control system;
.. Figure 3 is a graph showing the degree of opening of a prior art steam control valve and an interception valve wherein the ordinate represents the degree of opening of the valves and the abscissa the stroke of a speed relay;
Figure 4 is a block diagram of a control appara-tus according to . invention showing an interlock between the main steam stop valve and the re-heated steam stop valve and an interlock between the steam control valve and the interception valve;
Figure 5 is found on the sam~ sheet as Figure 3 and is a graph . . .
. .
~7~ 5 showing the degree of opening of the steam control valve and the interception valve of the apparatus of Figure 4 and is useful to explain the interlocked relation between these valves, wherein the ordinate represents the degree of opening of the valves and the abscissa the stroke of a speed relay;
Figure 6 is a diagrammatic representation, partly in section, of - the control apparatus oE Figure 4 and is useful to explain the interlocked relation between the main steam stop valve and the reheated steam stop valve;
Figure 7 is a diagram, partly in section, of the control apparatus of Figure 4 and is useful to explain the interlocked relation between the steam control valve and the interception valve; and Figure 8 is a diagram showing a modified interlocking system between the steam control valve and the interception valve.
A prior art generating plant and a prior art control system as described in the foregoing are illustrated in Figures l to 3 and will now be described in more detail with reference to those drawings.
`` Figure 1 illustrates a prior art turbine bypass sytem~wherein a high pressure bypass pipe 3 is connected to an intermediate point of a main steam pipe 2 between a boiler 1 and a high pressure turbine 18, that is a high pres-sure section of the turbine. A high pressure steam stop valve 4, a pressure reduction valve 5 and a temperature decreasing member 6 are connected in series in bypass pipe 3 to form a high pressure bypass line 8. The lower end of pipe 3 is connected to a low pressure steam pipe 7. There is also provided a low pressure bypass line 17 including a low pressure bypass pipe 12 connect-ed to an intermediate point of a high pressure reheated steam pipe 11 between - a reheater 10 and a medium pressure turbine 19~ that is the reheated steam section of the turbine. A low pressure steam stop valve 13, a pressure reduc-tion valve 14 and a temperature decreasing member 15 are connected in series in pipe 12. The lower end of the low pressure bypass pipe 12 is connected to a condenser 16.
When such turbine bypass systems are applied for a generating plant ; - 3 -~25 including a combination of a subcritical natural circulation boiler and a re-heated steam turbine or a combination of a forced circulation boiler and a reheated steam turbine~ not only the restarting of the turbine after interrup-tion of the generator load and after a cease of 6 to 8 hours can be performed effectively but also the reheater lO can be well protected.
On the other hand, since the pressure of the main steam generated by boiler l and that of the reheated steam generated by reheater lO have al-ready build up to predetermined values prior to the starting of the turbineJ
local excessive heat stresses would be formed in the turbine unless passing both steams to high pressure turbine 18 and medium pressure turbine 19 at a , suitable proportion before starting the turbine.
A block diagram of a prior art control system is shown in Figure 2.
As shown, main steam stop valve 20 and reheated steam stop valve 22 are controlled by independent main steam stop valve oil cylinder 24 and reheated steam stop valve oil cylinder 25 respectively so that these control valves are operated independently. For the purpose of preventing the creation of high heat stresses in the turbine during starting, it is usual to use the so-called full arc ejection operation mode wherein an auxiliary valve ~to be described later) contained in the main steam stop valve 20 is opened by the manipulation of a full arc ejection mechanism 26. However~ this mechanism is not related to ~he operation of the reheated steam stop valve 22.
Although steam control valve 21 and interception valve 23 are inter-locked, as shown by solid lines in Figure 3, interception valve 23 is opened at a considerably earlier point than the steam control valve 21 so that the valves are not interlocked such that substantially the same amount of the main steam and the reheated steam is supplied to the high pressure turbine 18 and the medium pressure turbine 19.
A preferred embodiment of this invention is described hereunder with ` reference to Figures 4 to 7 wherein elements corresponding to those shown in Figures 1 and 2 are designated by the same reference numerals.
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. , ~7~5 Referring to Figure 4, the interlocking of main steam stop valve 20 and reheated steam stop valve 22 at the time of starting a turbine can be ac-complished only by simultaneously operating cylinders 24 and 25 for main steam stop valve 20 and reheated steam stop valve 22 respectively. To do this an interlocking linkage 27 is provided between the full arc ejection mechanism - 26 and the reheated steam stop valve operating cylinder 25 so as to apply a control signal produced by the full arc ejection mechanism 26 also to the re-heated steam stop valve operating cylinder 25. Furthermore, there are provided a bias setter 28 for releasing the interlocking linkage 27 when the turbine operation is switched from start to normal running, and a gain adjuster 29 for adjusting the ratio of the degrees of opening of the main steam stop valve 20 and the reheated steam stop valve 22. An actual control system including these members is shown in Figure 6. According to the prior art practice the main steam stop valve 20 is provided with a main valve 30 and an auxiliary valve 31 contained therein. A control signal produced by the full arc ejection mechanism 26 is sent to the main steam stop valve operating cylinder 24 through links 32 and 33, a floating lever 34 and through a pilot valve 35 so as to operate the operating cylinder 24 to open the auxiliary valve 31 thereby effect-ing the full arc ejection operation during starting. In order to permit such full arc ejection operation during starting, an auxiliary valve 37 is also provided in the main valve 36 of the reheated stealn stop valve 22 shown as of a composite type wherein the reheated steam stop valve and the interception valve are contained in the same valve casing. Further, like the control system of the main steam stop valve 20, there are provided a floating lever 38, a pilot valve 39, and a reheated steam stop valve operating cylinder 25.
The two valve controls are connected by an interlocking lever 41 comprising an interlocking linkage mechanism 27 for interlocking the controls.
The interlocking linkage mechanism 27 further comprises a bias setter 28 and a gain adjuster 29. The bias setter 28 comprises a threaded shaft 44 and a manually operated handle 45. By rotating handle 45, a bias ;~
signal is sent to the main steam stop valve operating cylinder 24 and the re-heated steam stop valve operating cylinder 25 for releasing the interlock between the main steam stop valve 20 and the reheated steam stop valve 22.
It is also possible to drive the bias setter 28 by an electric motor or a solenoid. By moving the operating point of the gain adjuster 29 it is possible to adjust lever ratio a:b thereby determining the ratio of the degrees of open-ing o the main steam stop valve 20 and the reheated steam stop valve 22.
As most particularly illustrated in Figure 4, in order to supply substantially the same quantity of main steam and reheated steam to the high pressure turbine and the medium pressure turbine by interlocking the steam control valve 21 and the interception valve 23, there are provided an inter-locking relay 49 for bypassing a control signal sent from speed relay 46 to an interception valve relay 48 around a dash pot 47, and a low value priority device 51, that is a low value gate which selects the lower one of the output from the dash pot 47 and the output of the interlocking relay 49, for applying selected signal to an interception valve operating cylinder 52 through an interception valve relay 48. A gain adjuster 53 for properly correcting the ratio of the degrees of opening of the steam control valve 21 and the inter-ception valve 23 in accordance with the thermal load condition imparted to the turbine~ or the pressure conditions of the main steam and the reheated steam, and a bias setter 55 for releasing the interlock between the steam ~- control valve 21 and the intercept valve 23 when the operation of the turbine is switched to normal running after completion of the bias running, are provid-.
ed for the interlocking relay 49. This is ;mportant for interception valve 23.
~uring start-up when interlocking is required, the main steam and the reheated steam are admitted into the high pressure turbine and the medium pressure tur-bine respectively at a proper ratio. After start-up when the load of the tur-bine has increased to 15 to 20% of full load the amount of steam circulating through the turbine bypass system becomes zero and thereafter the steam flows ~; 30 a path from boiler to main steam stop valve, to steam control valve, to high .:
.
' ' ' pressure, turbine to reheater, to reheated steam stop valve~ to interception valve, and to medium pressure turbine whereupon the interlock is released.
In this case, the quantity of the steam flowing into the turbines is controlled by the steam control valve 21 while the interception valve 23 is maintained in the fully opened state. This condition of valve 23 is not altered even when the system Erequency varies more or less. For this reason, the interception valve which has been opened in an interlocked relation with the steam control valve will be opened as shown by dotted lines in Figures 5 by the bias signals t sent from bias setter 55. Although the opening characteristic curve of the interception valve is non-linear since the interlocking relation is maintained up to 20% load, the opening characteristic curve is depicted as a straight line. Notwithstanding the bias signals, the interception valve is opened according to a solid line shown in Figure 5 since it is controlled by a low value signal from the low value priority device.
Figure 7 shows the essential portions of the control systems for interlocking the steam control valve and the intercep~ion valve. As shown, the interlocking relay 49 comprises an interlocking lever 58 which transmits the control signal sent from speed relay 46 via link 57, an interlocking relay pilot valve 59 operated by lever 58, an interlocking relay valve 60 actuated by the pressuri~ed oil sent from the interlocking relay pilot valve 59 and gain setter 53 and bias setter 55 connected to the piston rod 61 of the inter-locking relay 60, the gain setter 53 and the bias setter 55 being connected to a rectangular link 62 or a lost motion mechanism provided with an elongated slot. The rectangular link 62 comprises the low value priority device 51 shown in Figure 4 for selecting the lower one of the output signals from the dash pot 47 and the interlocking relay 60. When the output from the interlock-ing relay 60 is high, the interception valve relay pilot lever 78 can move freely in the window of the rectangular link 62~ so that the output signal from the dash pot 47 preferentially controls the interception valve relay 67.
Conversely, when the output signal from the dash pot 47 is high the intercep-` -.
~701Z5 tion valve relay pilot lever 78 engages the upper side of the rectangular link 62 so that the upward movement of the lever 78 is restricted by the rectangular link 62. As a consequence, the position of the lever 78 is con-trolled by the interlocking relay 60 thus controlling the position of the interception valve relay 67.
The control apparatus of this invention operates as follows.
'! Prior to the starting of the turbine, all of the main steam stop valve 20, steam adjusting valve 21, reheated steam stop valve 22, and inter-ception valve 23 are maintained in the fully closed state and only the boiler is operating. At this time, the main steam and the reheated steam circulate through the high pressure bypass system 8 and the low pressure bypass system 17 as shown in Figure 1. The pressure of the reheated steam flowing through reheater 10 reaches 10 to 20 % of the rated pressure.
The interlock betwe0n the steam control valve and the interception - valve will be described with reference to Figure 7. More particularly, a synchronizing device 70 shown in Figure 7 is actuated to transmit its output signal to lever 72 which operates the speed relay 46 through link 71 and to the sleeve 74 of a governor 73 thus moving the sleeve to open opening 75 for pressurized oil. As a consquence the pressurized oil enters into speed relay 46 through opening 75 to increase the stroke of the piston 76 of speed relay 46. The stroke signal and the control signal from the synchronizing device - 70 are transmitted to both levers 57 and 63.
The control signal applied to lever 57 is transmitted through dash pot 47 to interception valve pilot lever 78 so as to pull upwardly the lever 78. The control signal applied to lever 57 is also transmitted to interlocking lever 58 of the interlocking relay 49, whereby the lever 58 and the piston 79 ` of the interlocking pilot valve 59 are moved upwardly as shown by an arrow.
As a conse~uence, the piston 80 of the in~erlocking relay 60 is moved upwardly.
At this time, if the bias setter 55 is at a zero state, or pulled upwardly, as ` 30 the out signal from the dash pot 47 is larger than the output signal of the ~.:
.
.:
;',''`', .
~37~Z5 interlocking relay 60, the lever 78 moves upwardly together with the rectangu-lar link 62 while engaging the upper side thereof. Accordingly, the intercep-; tion valve is opened according to the dotted line characteristic shown in Figure 5. The inclination of this dotted line characteristic can be adjusted by moving the position of the gain adjuster 53 thereby changing the lever ratio.
When the bias setter is moved downwardly after completion of theturbine bypass operation the interception valve will be operated according to the normal characteristic shown by the solid line shown in Figure 5.
Figure 8 shows a modified embodiment of an interlocking mechanism between the steam control valve and the interception valve. In Figure 8, a control signal for operating the steam control valve is derived out through a lever 63 and applied to the interception valve relay pilot lever 78 for operating the interception valve relay 67 through the following mechanism.
The mechanism comprises an interlocking relay 50 including an interlocking arm 64 connected to lever 63, and a gain adjuster 54 and a bias setter 56 associated with the arm 64; a low value priority device 51 including an inter-locking pilot valve 65 and a relay pilot valve 66 for the interception valve 67. The valves 65 and 66 are interconnected hydraulically and the piston of the pilot valve 66 is connected to the lever 78 on the output side of the dash pot. The mechanism also comprises a feedback lever 69 for negative feed back to the pilot valve 65 of a full open signal which is produced when the inter-ception valve is fully opened. ~lith this control system, the interception valve is operated in accordance with the broken line characteristic shown in Figure 5.
The interlock between the main steam stop valve and the reheated steam valve operates as follows.
At first motor 85 (see Figure 6) of the full arc ejection mechanism 26 is operated and the driving force created by the motor is transmitted to lever 32 through threaded shaft 86 and then applied to lever 33 and the inter-locking lever 41 of the interlocking linkage 27. In response to this driving _ g _ ~'.'' ' - ~ .
~, .
~L~7(~25 force the lever 32 rotates in the counterclockwise direction so that lever 33 is moved downwardly. Consequently, the floating lever 34 connected to the lower end of lever 33 and the piston rod 87 of the pilot valve 35 connected to the floating lever are also moved downwardly, thus opening oil port 88.
Then pressurized oil flows into the main steam stop valve operating cylinder
This invention relates to apparatus for controlling a steam turbine plant including a turbine bypass system wherein a plurality of control valves installed on the inlet sides of high pressure and medium pressure turbines are interlocked with each other to be opened simultaneously at the time of starting the turbines.
In an electric power generating plant of the type comprising a super-critical pressure through flow boiler and a reheating turbine it is usual to employ a so-called turbine bypass system in which, at the time of starting the boiler, a portion of the steam generated by the boiler is passed directly to a condenser instcad of passing it through the turbine.
The turbine bypass system has also been used in a modern electric power generating plant of the type including a subcritical pressure natural circulation boiler and a reheating turbine or a forced circulation boiler and a reheating turbine.
When such turbine bypass systems are applied for a generating plant including a combination of a subcritical natural circulation boiler and a re-heated steam turbine or a combination of a forced circulation boiler and a reheated steam turbine, not only can the restarting of the turbine after inter-ruption of the generator load and a s~oppage of 6 to 8 hours can be performed , 20 effectively but the reheater can be protected as well.
On the other hand, since the pressure of the main steam generated by the boiler and ~hat of the reheated steam generated by the reheater have already built up to predetermined values prior to the starting of the turbine, local excessive heat stresses would be formed in the turbine unless the steam flows were passed to the high pressure turbine and the medium pressure turbine in a suitable ratio before starting the turbine.
According to this invention there is provided apparatus for controll-ing a steam turbine plant including steam bypass systems of the type wherein the quantities of the steam flowing into a high pressure turbine provided with a high pressure bypass line and into a reheated steam turbine provided with a .. -- 1 --:
~ :.
~70~Z5 low pressure bypass line a.re controlled by a main steam s~op valve, a steam . control valve, a reheated steam stop valve and an interception valve, said apparatus comprising first interlocking means for interlocking a control system for the main steam stop valve with a control system for the reheated steam stop valve, and a second interlocking means or interlocking the steam - control valve and the interception valve, the second interlocking means in-cluding a speed relay device for controlling the second interlocking means for supplying steam to the high pressure turbine and the reheated steam tur-bine at a predetermined ratio, a dash pot~ and a low value priority device . 10 responsive to the lower one of the control signal from the speed relay device and passed through the dash pot and the control signal from the speed relay device, thereby controlling the interception valve so as to interlock the . main steam stop valve with the reheated steam stop valve and to interlock the ~ ..
steam control valve with the interception valve during starting of the turbine plant.
In the accompanying drawings, which illustrate a power plant of the relevant type, a prior art control system and exemplary embodiments of the present invention:
: Figure 1 is a diagrammatic representation of a prior art steam electric power generating plant provided with turbine bypass systems;
Figure 2 is a block diagram showing a prior art control system;
.. Figure 3 is a graph showing the degree of opening of a prior art steam control valve and an interception valve wherein the ordinate represents the degree of opening of the valves and the abscissa the stroke of a speed relay;
Figure 4 is a block diagram of a control appara-tus according to . invention showing an interlock between the main steam stop valve and the re-heated steam stop valve and an interlock between the steam control valve and the interception valve;
Figure 5 is found on the sam~ sheet as Figure 3 and is a graph . . .
. .
~7~ 5 showing the degree of opening of the steam control valve and the interception valve of the apparatus of Figure 4 and is useful to explain the interlocked relation between these valves, wherein the ordinate represents the degree of opening of the valves and the abscissa the stroke of a speed relay;
Figure 6 is a diagrammatic representation, partly in section, of - the control apparatus oE Figure 4 and is useful to explain the interlocked relation between the main steam stop valve and the reheated steam stop valve;
Figure 7 is a diagram, partly in section, of the control apparatus of Figure 4 and is useful to explain the interlocked relation between the steam control valve and the interception valve; and Figure 8 is a diagram showing a modified interlocking system between the steam control valve and the interception valve.
A prior art generating plant and a prior art control system as described in the foregoing are illustrated in Figures l to 3 and will now be described in more detail with reference to those drawings.
`` Figure 1 illustrates a prior art turbine bypass sytem~wherein a high pressure bypass pipe 3 is connected to an intermediate point of a main steam pipe 2 between a boiler 1 and a high pressure turbine 18, that is a high pres-sure section of the turbine. A high pressure steam stop valve 4, a pressure reduction valve 5 and a temperature decreasing member 6 are connected in series in bypass pipe 3 to form a high pressure bypass line 8. The lower end of pipe 3 is connected to a low pressure steam pipe 7. There is also provided a low pressure bypass line 17 including a low pressure bypass pipe 12 connect-ed to an intermediate point of a high pressure reheated steam pipe 11 between - a reheater 10 and a medium pressure turbine 19~ that is the reheated steam section of the turbine. A low pressure steam stop valve 13, a pressure reduc-tion valve 14 and a temperature decreasing member 15 are connected in series in pipe 12. The lower end of the low pressure bypass pipe 12 is connected to a condenser 16.
When such turbine bypass systems are applied for a generating plant ; - 3 -~25 including a combination of a subcritical natural circulation boiler and a re-heated steam turbine or a combination of a forced circulation boiler and a reheated steam turbine~ not only the restarting of the turbine after interrup-tion of the generator load and after a cease of 6 to 8 hours can be performed effectively but also the reheater lO can be well protected.
On the other hand, since the pressure of the main steam generated by boiler l and that of the reheated steam generated by reheater lO have al-ready build up to predetermined values prior to the starting of the turbineJ
local excessive heat stresses would be formed in the turbine unless passing both steams to high pressure turbine 18 and medium pressure turbine 19 at a , suitable proportion before starting the turbine.
A block diagram of a prior art control system is shown in Figure 2.
As shown, main steam stop valve 20 and reheated steam stop valve 22 are controlled by independent main steam stop valve oil cylinder 24 and reheated steam stop valve oil cylinder 25 respectively so that these control valves are operated independently. For the purpose of preventing the creation of high heat stresses in the turbine during starting, it is usual to use the so-called full arc ejection operation mode wherein an auxiliary valve ~to be described later) contained in the main steam stop valve 20 is opened by the manipulation of a full arc ejection mechanism 26. However~ this mechanism is not related to ~he operation of the reheated steam stop valve 22.
Although steam control valve 21 and interception valve 23 are inter-locked, as shown by solid lines in Figure 3, interception valve 23 is opened at a considerably earlier point than the steam control valve 21 so that the valves are not interlocked such that substantially the same amount of the main steam and the reheated steam is supplied to the high pressure turbine 18 and the medium pressure turbine 19.
A preferred embodiment of this invention is described hereunder with ` reference to Figures 4 to 7 wherein elements corresponding to those shown in Figures 1 and 2 are designated by the same reference numerals.
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. , ~7~5 Referring to Figure 4, the interlocking of main steam stop valve 20 and reheated steam stop valve 22 at the time of starting a turbine can be ac-complished only by simultaneously operating cylinders 24 and 25 for main steam stop valve 20 and reheated steam stop valve 22 respectively. To do this an interlocking linkage 27 is provided between the full arc ejection mechanism - 26 and the reheated steam stop valve operating cylinder 25 so as to apply a control signal produced by the full arc ejection mechanism 26 also to the re-heated steam stop valve operating cylinder 25. Furthermore, there are provided a bias setter 28 for releasing the interlocking linkage 27 when the turbine operation is switched from start to normal running, and a gain adjuster 29 for adjusting the ratio of the degrees of opening of the main steam stop valve 20 and the reheated steam stop valve 22. An actual control system including these members is shown in Figure 6. According to the prior art practice the main steam stop valve 20 is provided with a main valve 30 and an auxiliary valve 31 contained therein. A control signal produced by the full arc ejection mechanism 26 is sent to the main steam stop valve operating cylinder 24 through links 32 and 33, a floating lever 34 and through a pilot valve 35 so as to operate the operating cylinder 24 to open the auxiliary valve 31 thereby effect-ing the full arc ejection operation during starting. In order to permit such full arc ejection operation during starting, an auxiliary valve 37 is also provided in the main valve 36 of the reheated stealn stop valve 22 shown as of a composite type wherein the reheated steam stop valve and the interception valve are contained in the same valve casing. Further, like the control system of the main steam stop valve 20, there are provided a floating lever 38, a pilot valve 39, and a reheated steam stop valve operating cylinder 25.
The two valve controls are connected by an interlocking lever 41 comprising an interlocking linkage mechanism 27 for interlocking the controls.
The interlocking linkage mechanism 27 further comprises a bias setter 28 and a gain adjuster 29. The bias setter 28 comprises a threaded shaft 44 and a manually operated handle 45. By rotating handle 45, a bias ;~
signal is sent to the main steam stop valve operating cylinder 24 and the re-heated steam stop valve operating cylinder 25 for releasing the interlock between the main steam stop valve 20 and the reheated steam stop valve 22.
It is also possible to drive the bias setter 28 by an electric motor or a solenoid. By moving the operating point of the gain adjuster 29 it is possible to adjust lever ratio a:b thereby determining the ratio of the degrees of open-ing o the main steam stop valve 20 and the reheated steam stop valve 22.
As most particularly illustrated in Figure 4, in order to supply substantially the same quantity of main steam and reheated steam to the high pressure turbine and the medium pressure turbine by interlocking the steam control valve 21 and the interception valve 23, there are provided an inter-locking relay 49 for bypassing a control signal sent from speed relay 46 to an interception valve relay 48 around a dash pot 47, and a low value priority device 51, that is a low value gate which selects the lower one of the output from the dash pot 47 and the output of the interlocking relay 49, for applying selected signal to an interception valve operating cylinder 52 through an interception valve relay 48. A gain adjuster 53 for properly correcting the ratio of the degrees of opening of the steam control valve 21 and the inter-ception valve 23 in accordance with the thermal load condition imparted to the turbine~ or the pressure conditions of the main steam and the reheated steam, and a bias setter 55 for releasing the interlock between the steam ~- control valve 21 and the intercept valve 23 when the operation of the turbine is switched to normal running after completion of the bias running, are provid-.
ed for the interlocking relay 49. This is ;mportant for interception valve 23.
~uring start-up when interlocking is required, the main steam and the reheated steam are admitted into the high pressure turbine and the medium pressure tur-bine respectively at a proper ratio. After start-up when the load of the tur-bine has increased to 15 to 20% of full load the amount of steam circulating through the turbine bypass system becomes zero and thereafter the steam flows ~; 30 a path from boiler to main steam stop valve, to steam control valve, to high .:
.
' ' ' pressure, turbine to reheater, to reheated steam stop valve~ to interception valve, and to medium pressure turbine whereupon the interlock is released.
In this case, the quantity of the steam flowing into the turbines is controlled by the steam control valve 21 while the interception valve 23 is maintained in the fully opened state. This condition of valve 23 is not altered even when the system Erequency varies more or less. For this reason, the interception valve which has been opened in an interlocked relation with the steam control valve will be opened as shown by dotted lines in Figures 5 by the bias signals t sent from bias setter 55. Although the opening characteristic curve of the interception valve is non-linear since the interlocking relation is maintained up to 20% load, the opening characteristic curve is depicted as a straight line. Notwithstanding the bias signals, the interception valve is opened according to a solid line shown in Figure 5 since it is controlled by a low value signal from the low value priority device.
Figure 7 shows the essential portions of the control systems for interlocking the steam control valve and the intercep~ion valve. As shown, the interlocking relay 49 comprises an interlocking lever 58 which transmits the control signal sent from speed relay 46 via link 57, an interlocking relay pilot valve 59 operated by lever 58, an interlocking relay valve 60 actuated by the pressuri~ed oil sent from the interlocking relay pilot valve 59 and gain setter 53 and bias setter 55 connected to the piston rod 61 of the inter-locking relay 60, the gain setter 53 and the bias setter 55 being connected to a rectangular link 62 or a lost motion mechanism provided with an elongated slot. The rectangular link 62 comprises the low value priority device 51 shown in Figure 4 for selecting the lower one of the output signals from the dash pot 47 and the interlocking relay 60. When the output from the interlock-ing relay 60 is high, the interception valve relay pilot lever 78 can move freely in the window of the rectangular link 62~ so that the output signal from the dash pot 47 preferentially controls the interception valve relay 67.
Conversely, when the output signal from the dash pot 47 is high the intercep-` -.
~701Z5 tion valve relay pilot lever 78 engages the upper side of the rectangular link 62 so that the upward movement of the lever 78 is restricted by the rectangular link 62. As a consequence, the position of the lever 78 is con-trolled by the interlocking relay 60 thus controlling the position of the interception valve relay 67.
The control apparatus of this invention operates as follows.
'! Prior to the starting of the turbine, all of the main steam stop valve 20, steam adjusting valve 21, reheated steam stop valve 22, and inter-ception valve 23 are maintained in the fully closed state and only the boiler is operating. At this time, the main steam and the reheated steam circulate through the high pressure bypass system 8 and the low pressure bypass system 17 as shown in Figure 1. The pressure of the reheated steam flowing through reheater 10 reaches 10 to 20 % of the rated pressure.
The interlock betwe0n the steam control valve and the interception - valve will be described with reference to Figure 7. More particularly, a synchronizing device 70 shown in Figure 7 is actuated to transmit its output signal to lever 72 which operates the speed relay 46 through link 71 and to the sleeve 74 of a governor 73 thus moving the sleeve to open opening 75 for pressurized oil. As a consquence the pressurized oil enters into speed relay 46 through opening 75 to increase the stroke of the piston 76 of speed relay 46. The stroke signal and the control signal from the synchronizing device - 70 are transmitted to both levers 57 and 63.
The control signal applied to lever 57 is transmitted through dash pot 47 to interception valve pilot lever 78 so as to pull upwardly the lever 78. The control signal applied to lever 57 is also transmitted to interlocking lever 58 of the interlocking relay 49, whereby the lever 58 and the piston 79 ` of the interlocking pilot valve 59 are moved upwardly as shown by an arrow.
As a conse~uence, the piston 80 of the in~erlocking relay 60 is moved upwardly.
At this time, if the bias setter 55 is at a zero state, or pulled upwardly, as ` 30 the out signal from the dash pot 47 is larger than the output signal of the ~.:
.
.:
;',''`', .
~37~Z5 interlocking relay 60, the lever 78 moves upwardly together with the rectangu-lar link 62 while engaging the upper side thereof. Accordingly, the intercep-; tion valve is opened according to the dotted line characteristic shown in Figure 5. The inclination of this dotted line characteristic can be adjusted by moving the position of the gain adjuster 53 thereby changing the lever ratio.
When the bias setter is moved downwardly after completion of theturbine bypass operation the interception valve will be operated according to the normal characteristic shown by the solid line shown in Figure 5.
Figure 8 shows a modified embodiment of an interlocking mechanism between the steam control valve and the interception valve. In Figure 8, a control signal for operating the steam control valve is derived out through a lever 63 and applied to the interception valve relay pilot lever 78 for operating the interception valve relay 67 through the following mechanism.
The mechanism comprises an interlocking relay 50 including an interlocking arm 64 connected to lever 63, and a gain adjuster 54 and a bias setter 56 associated with the arm 64; a low value priority device 51 including an inter-locking pilot valve 65 and a relay pilot valve 66 for the interception valve 67. The valves 65 and 66 are interconnected hydraulically and the piston of the pilot valve 66 is connected to the lever 78 on the output side of the dash pot. The mechanism also comprises a feedback lever 69 for negative feed back to the pilot valve 65 of a full open signal which is produced when the inter-ception valve is fully opened. ~lith this control system, the interception valve is operated in accordance with the broken line characteristic shown in Figure 5.
The interlock between the main steam stop valve and the reheated steam valve operates as follows.
At first motor 85 (see Figure 6) of the full arc ejection mechanism 26 is operated and the driving force created by the motor is transmitted to lever 32 through threaded shaft 86 and then applied to lever 33 and the inter-locking lever 41 of the interlocking linkage 27. In response to this driving _ g _ ~'.'' ' - ~ .
~, .
~L~7(~25 force the lever 32 rotates in the counterclockwise direction so that lever 33 is moved downwardly. Consequently, the floating lever 34 connected to the lower end of lever 33 and the piston rod 87 of the pilot valve 35 connected to the floating lever are also moved downwardly, thus opening oil port 88.
Then pressurized oil flows into the main steam stop valve operating cylinder
2~ through oil ports 88 and 89 whereby piston 90 is moved upwardly to gradual-ly open the auxiliary valve 31 of the main steam stop valve 20.
The driving force applied to the interlocking lever 41 of linkage mechanism 27 rotates the lever 41 in the direction indicated by arrows where-by the auxiliary valve 37 of the reheated steam stop valve 22 is opened simul-taneously with the auxiliary valve 31 of the main steam stop valve 20.
As the opening operation of the auxiliary valves 31 and 37 of the main steam stop valve 20 and the reheated steam stop valve 22 approaches completion, the steam regulating valve 21 and the interception valve 23 whic~
have been maintained in their fully opened positions are gradually closed by the readjustment of the synchronizing device 70 and then maintained at a definite opening. During this closing operation the main steam and the reheat-ed steam flowing through the main steam stop valve 20 and the reheated steam stop valve 22 reach prescribed pressures and the opening operations of the main valves 30 and 36 of the main steam stop valve 20 and the reheated steam ~ stop valve 22 respectively are commenced at the same time.
; After the main valves 30 and 36 have been fully opened the control of the steam is transferred to the steam regulating valve 21 for regulating - the quantity of steam flowing into the turbine. Such transfer can be made ` either during the turbine bypass operation or after completion of the bypass - operation. However, it is essential that the gains should be adjusted by gain adjusting devices 29, 53 and 54 such that the ratio of opening of the main steam stop valve 20 and the reheated steam stop valve 22 will be the same as the ratio between the openings of the steam regulating valve 21 and the inter-" 30 ception valve 23.
. .
~r,~
. ' ' ' ' .
. ,' , ~70~5 When the turbine bypass running is stopped bias signals are sent ,i.
from bias setters 28, 55 and 56 to main steam stop valve 20, reheated steam : stop valve 22, steam adjusting valve 21 and interception valve 23 respectively to release interlockings so that these valves are controlled by the normal control system.
As above described, the main steam stop valve and the reheated steam stop valve are interlocked and the steam adjusting valve and the interception valve are also interlocked so that it is possible to operate the medium pres-~ sure turbine by the full arc ejection mode. Further, it is possible to supply - 10 main steam and reheated steam to the high pressure turbine and the medium pressure turbine at a proper ratio thus making it possible to eliminate any local heating of the turbine and to improve the operating efficiency of the turbine.
:
. . .
', :
.i. - 11 -.
' '': '~f'"'
The driving force applied to the interlocking lever 41 of linkage mechanism 27 rotates the lever 41 in the direction indicated by arrows where-by the auxiliary valve 37 of the reheated steam stop valve 22 is opened simul-taneously with the auxiliary valve 31 of the main steam stop valve 20.
As the opening operation of the auxiliary valves 31 and 37 of the main steam stop valve 20 and the reheated steam stop valve 22 approaches completion, the steam regulating valve 21 and the interception valve 23 whic~
have been maintained in their fully opened positions are gradually closed by the readjustment of the synchronizing device 70 and then maintained at a definite opening. During this closing operation the main steam and the reheat-ed steam flowing through the main steam stop valve 20 and the reheated steam stop valve 22 reach prescribed pressures and the opening operations of the main valves 30 and 36 of the main steam stop valve 20 and the reheated steam ~ stop valve 22 respectively are commenced at the same time.
; After the main valves 30 and 36 have been fully opened the control of the steam is transferred to the steam regulating valve 21 for regulating - the quantity of steam flowing into the turbine. Such transfer can be made ` either during the turbine bypass operation or after completion of the bypass - operation. However, it is essential that the gains should be adjusted by gain adjusting devices 29, 53 and 54 such that the ratio of opening of the main steam stop valve 20 and the reheated steam stop valve 22 will be the same as the ratio between the openings of the steam regulating valve 21 and the inter-" 30 ception valve 23.
. .
~r,~
. ' ' ' ' .
. ,' , ~70~5 When the turbine bypass running is stopped bias signals are sent ,i.
from bias setters 28, 55 and 56 to main steam stop valve 20, reheated steam : stop valve 22, steam adjusting valve 21 and interception valve 23 respectively to release interlockings so that these valves are controlled by the normal control system.
As above described, the main steam stop valve and the reheated steam stop valve are interlocked and the steam adjusting valve and the interception valve are also interlocked so that it is possible to operate the medium pres-~ sure turbine by the full arc ejection mode. Further, it is possible to supply - 10 main steam and reheated steam to the high pressure turbine and the medium pressure turbine at a proper ratio thus making it possible to eliminate any local heating of the turbine and to improve the operating efficiency of the turbine.
:
. . .
', :
.i. - 11 -.
' '': '~f'"'
Claims (10)
1. Apparatus for controlling a steam turbine plant including steam bypass systems of the type wherein the quantities of the steam flowing into a high pressure turbine provided with a high pressure bypass line and into a reheated steam turbine provided with a low pres-sure bypass line are controlled by a main steam stop valve, a steam control valve, a reheated steam stop valve and an interception valve, said apparatus comprising first interlocking means for interlocking a control system for said main steam stop valve with a control system for said reheated steam stop valve, and a second interlocking means for interlocking said steam control valve and said interception valve, said second interlocking means in-cluding a speed relay device for controlling said second interlocking means for supplying steam to said high pres-sure turbine and said reheated steam turbine at a pre-determined ratio, a dash pot,and a low value priority device responsive to the lower one of the control sig-nal from said speed relay device and passed through said dash pot and the control signal from said speed relay device, thereby controlling said interception valve so as to interlock said main steam stop valve with said reheated steam stop valve and to interlock said steam control valve with said interception valve during starting of the tur-bine plant.
2. The apparatus according to claim 1 wherein bias setters are provided for said first interlocking means and said second interlocking means respectively so as to release the interlocks between said main steam stop valve and said reheated steam stop valve, and between said steam control valve and said interception valve.
3. The apparatus according to claim 1 wherein gain adjusters are provided for said first interlocking means and said second interlocking means respectively so as to adjust the ratio of the degrees of openings of said main steam stop valve and said reheated steam stop valve and the ratio of the degrees of the openings of said steam control valve and said interception valve when the inter-locks are released after completion of the starting of the turbine plant, thereby supplying a predetermined amount of reheated steam to said reheated steam turbine.
4. The apparatus according to claim 1 wherein said second interlocking means comprises a governor respon-sive to the speed of the turbine plant, a speed relay controlled by said governor for operating said control valve, an interlocking relay connected in parallel with said dash pot, a low value priority device for selecting smaller one of the outputs from said dash pot and from said speed relay, and an interception valve relay con-trolled by the output from said low value priority device for operating said interception valve.
5. The apparatus according to claim 4 wherein said interlocking relay is provided with a bias setter and a gain adjuster.
6. The apparatus according to claim 1 wherein each of said main steam stop valve and said preheated steam stop valve respectively includes a main valve and an auxiliary valve contained therein, and said apparatus comprises a full are ejection mechanism, a main steam stop valve operating cylinder, a first linkage interconnecting said full arc ejection mechanism and said main steam stop valve operating cylinder for opening the auxiliary valve of the main steam stop valve to provide a full arc ejection operation during starting, a reheated steam stop valve operating cylinder, a second linkage interconnecting said first linkage with said reheated steam stop valve operating cylinder, a gain adjuster and a bias setter provided for said second linkage, and means for adjusting said bias setter for releasing the inter-lock between said main steam stop valve and said reheated steam stop valve.
7. The apparatus according to claim 6 wherein said gain adjuster is provided for one of a link of said second linkage such that the ratio of the degrees of the open-ings of said main steam stop valve and the reheated steam stop valve is made variable.
8. The apparatus according to claim 1 wherein said second interlocking means for interlocking said steam control valve and said interception valve comprises a governor responsive to the speed of the turbine plant, a speed relay controlled by said governor, an interception valve relay for operating said interception valve, a dash pot included in a linkage interconnecting said speed relay and said interception valve relay, a mechanical low value priority device connected in parallel with said dash pot for controlling said interception valve relay, and means for operating said steam control valve by said speed relay.
9. The apparatus according to claim 8 wherein said mechanical low value priority device comprises a pilot valve operated by said speed relay,an interlocking relay controlled by said pilot valve having a piston connected to the output side of said dash pot through a lost motion mechanism, and a bias setter and a gain setter operative-ly connected to said lost motion mechanism.
10. The apparatus according to claim 8 wherein said mechanical low value priority device comprises an inter-locking pilot valve operated by said speed relay through a linkage, a second pilot valve hydraulically connected to said interlocking pilot valve for controlling said interception valve relay, the piston of said second pilot valve being connected to the output side of said dash pot, and a gain adjuster and a bias setter provided for said linkage.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9498475A JPS5224604A (en) | 1975-08-06 | 1975-08-06 | Control system of steam turbine plant having turbine by-pass system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070125A true CA1070125A (en) | 1980-01-22 |
Family
ID=14125151
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA258,463A Expired CA1070125A (en) | 1975-08-06 | 1976-08-05 | Apparatus for controlling steam turbine plants including steam bypass systems |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5224604A (en) |
| AU (1) | AU514591B2 (en) |
| CA (1) | CA1070125A (en) |
| ZA (1) | ZA764675B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS50135442A (en) * | 1974-04-17 | 1975-10-27 | ||
| JPS511841A (en) * | 1974-06-21 | 1976-01-09 | Hitachi Ltd | |
| JP2517763B2 (en) * | 1989-07-13 | 1996-07-24 | 株式会社日立製作所 | Turbin control method |
| US5018356A (en) * | 1990-10-10 | 1991-05-28 | Westinghouse Electric Corp. | Temperature control of a steam turbine steam to minimize thermal stresses |
-
1975
- 1975-08-06 JP JP9498475A patent/JPS5224604A/en active Granted
-
1976
- 1976-08-03 ZA ZA764675A patent/ZA764675B/en unknown
- 1976-08-03 AU AU16523/76A patent/AU514591B2/en not_active Expired
- 1976-08-05 CA CA258,463A patent/CA1070125A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS54243B2 (en) | 1979-01-09 |
| AU1652376A (en) | 1978-02-09 |
| AU514591B2 (en) | 1981-02-19 |
| ZA764675B (en) | 1977-07-27 |
| JPS5224604A (en) | 1977-02-24 |
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| MKEX | Expiry |