JP2013064372A - Low pressure turbine bypass control device, and power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low pressure turbine bypass control device, capable of evading an unnecessary open operation of a low pressure turbine bypass valve and enabling a stable operation under each operating condition, even in the operating condition different from normal conditions such as an increase of pressure at an inlet of an intermediate and low pressure turbine during a normal load operation.SOLUTION: The control device captures a bypass condition of the high pressure water supply heater (opening and closing of the high pressure water supply heater bypass valve 28), when in the operating condition different from the normal conditions such as the increase of pressure at the inlet of the intermediate and low pressure turbine during the normal load operation, for example, when the water supply to a boiler 1 is switched from the side of a high pressure water supply heater 30 to the side of a high pressure water supply heater bypass pipe 29. Then the control device performs switching from a function generator (A) 42 in the normal operating condition to a function generator (B) 43 calculated based on a heat balance calculation in the condition, and also performs the setting of control pressure of the low pressure turbine bypass valve 12 and controls the opening/closing of the low pressure turbine bypass valve 12.

Description

  The present invention relates to a low-pressure turbine bypass control device and a power plant.

  In a thermal power plant having a high-pressure turbine and a medium- and low-pressure turbine, a high-pressure turbine bypass pipe that bypasses the high-pressure turbine and discharges steam to the high-pressure turbine exhaust pipe, and a low-pressure turbine bypass that bypasses the medium- and low-pressure turbine and discharges steam to the condenser A tube is provided. Conventionally, as a low-pressure turbine bypass control device that controls a low-pressure turbine bypass valve provided in a low-pressure turbine bypass pipe, for example, as described in Patent Document 1, target initial values of different plants are different depending on the start-up mode at the time of plant start-up. Patent Document 2 describes a low-pressure turbine bypass control device that sets a target value of a reheat steam pressure corresponding to a load and controls a low-pressure turbine bypass valve, or a steam turbine plant that uses part of steam as process steam in a factory. As described above, a low-pressure turbine bypass control device that enables supply of process (factory) steam even when the turbine is stopped or the boiler is operating independently has been proposed.

JP-A-2-11807 Japanese Patent Laid-Open No. 10-325306

  The steam that bypasses the high-pressure turbine and is discharged to the high-pressure turbine exhaust pipe is heated by the reheater and supplied to the medium- and low-pressure turbine. Further, steam is extracted from the high-pressure turbine or the high-pressure turbine exhaust pipe, and the steam is supplied to a feed water heater or the like. In such a power plant, during normal load operation, all the steam generated from the steam generator is supplied to the high pressure turbine, and the steam that has worked in the high pressure turbine is heated by the reheater and supplied to the medium to low pressure turbine. The high-pressure turbine bypass valve and the low-pressure turbine bypass valve respectively provided in the high-pressure turbine bypass pipe and the low-pressure turbine bypass pipe are fully closed and in a standby state. From this state, if an event occurs in which steam is no longer discharged from the high-pressure turbine or high-pressure turbine exhaust pipe to the feed water heater, the high-pressure turbine exhaust volume increases. The operating state is different from the heat balance. For this reason, when trying to continue the load operation in this state, the low-pressure turbine bypass valve is opened, resulting in disturbance of the turbine load operation due to the discharge of unnecessary steam. Conventionally, including the Patent Documents 1 and 2, the pressure control of the medium / low pressure turbine inlet pressure (when the low pressure turbine bypass valve is controlled to open / close) There is no countermeasure for low-pressure turbine inlet pressure control.

  The present invention avoids unnecessary opening operation of the low-pressure turbine bypass valve and enables stable operation in each operation state even when the operation pressure is different from the normal operation state in which the medium-low pressure turbine inlet pressure increases during normal load operation. An object of the present invention is to provide a low-pressure turbine bypass control device.

  In order to solve the above-described problems, the present invention provides a control setting pressure for the medium-low pressure turbine inlet pressure when the low-pressure turbine bypass valve opening / closing control is in an operation state different from normal in which the medium-low pressure turbine inlet pressure increases during normal operation. Is switched to a setting based on the heat balance calculation in that state, and the open / close control is performed.

  For example, in a power generation plant having a feed water heater that supplies steam from a middle stage of a high-pressure turbine and exchanges heat with feed water to a boiler, and a feed water heater bypass pipe that bypasses the feed water heater and feeds feed water to the boiler. When the feed water to the feed water heater side is switched from the feed water heater side to the feed water heater bypass side and the feed water to the feed water heater is cut off and heat exchange with the steam supplied from the high pressure turbine intermediate stage is not performed, Since there is no steam flow to the heater and the displacement of the high-pressure turbine increases, the intermediate / low-pressure turbine inlet pressure rises, and the relationship between the high-pressure turbine first stage pressure and the intermediate / low-pressure turbine inlet pressure changes. If the operation is continued in a state where the heat balance is changed, the low pressure turbine bypass valve is opened unnecessarily due to an increase in the intermediate / low pressure turbine inlet pressure, and the turbine load is disturbed. In the present invention, in order to avoid this, the bypass condition of the feed water heater is captured, and the setting based on the high pressure turbine first stage pressure calculated by the heat balance calculation in a state where the feed water heater is bypassed is set to the medium / low pressure turbine inlet pressure. By switching the pressure set value, it is possible to perform the same control as during normal load operation.

  According to the present invention, it is possible to avoid unnecessary opening operation of the low-pressure turbine bypass valve even when the operation state is different from the normal operation state in which the medium-low pressure turbine inlet pressure increases during normal load operation, and stable operation in each operation state. Is possible.

It is a figure which shows the system | strain and low-pressure turbine bypass control system (Example 1) of the steam power plant to which one Example of this invention is applied. High pressure turbine first stage pressure and control setting in a function generator that outputs a control set pressure (pressure for opening / closing control of a low pressure turbine bypass valve) at a medium to low pressure turbine inlet based on the high pressure turbine first stage pressure used in Embodiment 1 of the present invention It is a figure which shows the relationship with a pressure, and is a figure which shows the relationship at the time of normal driving | operation. High pressure turbine first stage pressure and control setting in a function generator that outputs a control set pressure (pressure for opening / closing control of a low pressure turbine bypass valve) at a medium to low pressure turbine inlet based on the high pressure turbine first stage pressure used in Embodiment 1 of the present invention It is a figure which shows the relationship with a pressure, and is a figure which shows the relationship at the time of a high voltage | pressure feed water heater bypass operation. It is a figure which shows the system | strain and low-pressure turbine bypass control system (Example 2) of the steam power plant to which one Example of this invention is applied. It is a figure which shows the system | strain and low-pressure turbine bypass control system (Example 3) of the steam power plant to which one Example of this invention is applied.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a steam power plant system and a low-pressure turbine bypass control system to which an embodiment of the present invention is applied. In the present Example 1, it has the function to catch the opening operation of a high pressure feed water heater bypass valve, and to switch the function computing unit used as a control setting.

  The outline | summary of this Example 1 is heated with the steam generator (boiler), the high pressure turbine driven with the steam generated from the steam generator, the reheater which heats the exhaust steam of the high pressure turbine, and the reheater. High-pressure turbine bypass pipe having a high-pressure turbine bypass valve that bypasses the high-pressure turbine to the high-pressure turbine exhaust pipe (low-temperature reheat pipe), and reheats the medium- and low-pressure turbine driven by the reheat steam, the condenser, and the steam generator The low-pressure turbine bypass pipe with a low-pressure turbine bypass valve that leads the reheated steam heated by the generator to the condenser and bypasses the medium- and low-pressure turbine, and heats the feed water to the steam generator by the steam supplied from the intermediate stage of the high-pressure turbine Feed water heater (high pressure feed water heater), feed water heater bypass pipe having a feed water heater bypass valve that bypasses the feed water heater and guides the feed water to the steam generator In order to suppress the rise in reheat steam pressure at the outlet of the reheater during transient operation where surplus steam is generated during startup, shutdown, emergency stop, etc., the surplus steam from the low pressure turbine bypass pipe to the condenser This is a low-pressure turbine bypass control device that controls the intermediate and low-pressure turbine inlet pressure with a low-pressure turbine bypass valve.When the low-pressure turbine bypass valve is started, stopped, or emergency stopped, the pressure setting is based on the first-stage pressure of the high-pressure turbine. During normal load operation, it is controlled to be fully closed by applying a bias to the pressure setting so that the load operation is not hindered, and the feed water heater bypass valve is opened to the feed water heater. The water supply is cut off, heat is not exchanged with the steam supplied from the intermediate stage of the high-pressure turbine, and there is no steam flow from the high-pressure turbine to the water heater. When the high-pressure turbine displacement increases, the medium- and low-pressure turbine inlet pressure rises, the relationship between the high-pressure turbine first stage pressure and the intermediate-pressure turbine inlet pressure changes, and the operation continues with this heat balance changed. The low-pressure turbine bypass valve was opened unnecessarily to avoid disturbing the turbine load, and the open operation of the feed water heater bypass valve was captured and calculated by heat balance calculation after the feed water heater bypass. The setting is based on the first-stage pressure of the high-pressure turbine, and is controlled by switching the pressure setting value at the inlet of the medium- and low-pressure turbine.

  Hereinafter, it demonstrates in detail based on drawing. The steam generated in the boiler 1 passes through the main steam pipe 2, flows into the high-pressure turbine 7 through the main steam stop valve 5 and the main steam control valve 6, and after working, is discharged as low-temperature reheat steam. After being led to the reheater 9 through the low-temperature reheat pipe 8 and heated by the reheater 9, it becomes high-temperature reheat steam, passes through the high-temperature reheat pipe 10, and passes through the reheat steam stop valve 14 and the intercept valve 15. It flows into the intermediate pressure turbine 16. After working in the intermediate pressure turbine 16, the steam flows into the low pressure turbine 17, and after working, is discharged to the condenser 18, condensed, and becomes condensed water. The condensate whose pressure has been increased by the condensate pump 19 passes through the condensate pipe 20, flows into the low-pressure heater 24 through the deaerator water level control valve 23, is heated, and is degassed by the deaerator 25. After that, the pressure is raised by the feed water pump 26, heated by the high pressure feed water heater 30, and supplied to the boiler 1 as feed water. The high-pressure feed water heater 30 is supplied with extraction steam from an intermediate stage of the high-pressure turbine through an extraction pipe 31 provided with an extraction stop valve 32 to heat the feed water with the extraction steam. Moreover, the high pressure feed water heater 30 to which the extraction steam from the low temperature reheat pipe or the intermediate pressure turbine intermediate stage is supplied is installed as necessary.

  Further, in a transient operation state in which surplus steam that cannot be passed to the turbine is generated at the time of start / stop / emergency stop, the steam generated from the boiler 1 passes through the high-pressure turbine bypass pipe 3 having the high-pressure turbine bypass valve 4 and is recycled. Heated by the heater 9. The steam heated by the reheater 9 passes through the low pressure turbine bypass pipe 11 having the low pressure turbine bypass valve 12 from the high temperature reheat steam pipe 10 and is discharged to the condenser 18 via the temperature reducer 13. Condensate from the condenser 18 is supplied to the temperature reducer 13 via a temperature reduction water pipe 21 provided with a temperature reduction valve 22. Thus, the high pressure turbine bypass pipe bypasses the high pressure turbine, and the low pressure turbine bypass pipe bypasses the intermediate pressure turbine and the low pressure turbine. In this embodiment, an intermediate pressure turbine is used, but the intermediate pressure turbine may be omitted. Therefore, in the present invention, the medium-pressure turbine and the low-pressure turbine are collectively referred to as a medium-low pressure turbine, and the term “medium-low pressure turbine” includes both the combination of the medium-pressure turbine and the low-pressure turbine and only the low-pressure turbine.

  The feed water pipe 27 is provided with a high pressure feed water heater bypass valve 28 and a high pressure feed water heater bypass pipe 29 for bypassing the high pressure feed water heater 30 and supplying feed water to the boiler 1.

  Next, control of the low pressure turbine bypass valve will be described.

  In a transient state where surplus steam is generated such as during start-up / stop / emergency stop, in order to suppress the increase in the reheat steam pressure at the reheater outlet, the control set pressure of the intermediate pressure turbine inlet pressure based on the high pressure turbine first stage pressure 40 is set. The low pressure turbine bypass valve is controlled at, and surplus steam is discharged from the low pressure turbine bypass pipe to the condenser. FIG. 2A shows the contents of the function setter (A) 42 for obtaining the control set pressure at the inlet of the intermediate pressure turbine based on the first-stage pressure of the high-pressure turbine during normal operation. The pressure is set based on this. This function is calculated by calculating the heat balance during normal operation.

  In the low pressure turbine bypass control during normal load operation, as shown in FIGS. 1 and 2A, a bias value 46 is added to the control set pressure obtained by the function calculator (A) 42 based on the high pressure turbine first stage pressure 40. Control by value. In order to control in this way, it is operated so that the fully closed state is maintained and normal load operation is not hindered. Since the low pressure turbine bypass valve 12 is operated in cooperation with the high pressure turbine bypass valve 4, the bias value 46 is set so that the low pressure turbine bypass valve 12 is also closed when the high pressure turbine bypass valve 4 is fully closed. 4 Adder 45 adds to the output of function generator (A) 42 under the fully closed condition. As a result, the low-pressure turbine bypass valve 12 is also in a fully closed standby.

  When the high-pressure feed water heater bypass valve 28 is opened during normal operation and the feed water supply from the feed water pump 26 to the boiler 1 is switched from the feed water pipe 27 to the high-pressure feed water heater bypass pipe 29, the high-pressure feed water heater 30 Since there is no heat exchange with the turbine bleed air, the flow of bleed air is blocked. When the bleed air is shut off, steam is no longer discharged from the high pressure turbine 7 and the low temperature reheat steam pipe 8, the amount of steam flowing from the reheater 9 into the intermediate pressure turbine 16 increases, and the intermediate pressure turbine inlet pressure 41 increases. To do.

  At this time, the heat balance between the high-pressure turbine first-stage pressure 40 and the intermediate-pressure turbine inlet pressure 41 used in the function calculator (A) 42 changes from that during normal operation. Therefore, the intermediate pressure turbine inlet pressure 41 rises above the pressure value set based on the function generator (A) 42 used for the low pressure turbine bypass control during normal operation, and the low pressure turbine bypass valve 12 opens. Thus, the high-temperature reheat steam is discharged to the condenser 18 to disturb the load operation, and energy is lost. In order to avoid the unnecessary opening operation of the low-pressure turbine bypass valve 12, as shown in FIG. 1, the opening operation of the high-pressure feed water heater bypass valve 28 is caught and the heat in the bypassed state is detected by the signal switch 44. The control setting is switched to the function generator (B) 43 calculated by the balance calculation. As a result, the low-pressure turbine bypass valve 12 can be controlled with the setting based on the heat balance in the feed water heater bypass operation as in the normal load operation. In the figure, 47 indicates a deviation calculator and 48 indicates a PI calculator.

  In addition, since the function generator (A) 42 and the function generator (B) 43 create a function based on the heat balance calculation under each load condition, the load condition changes due to load increase / decrease etc. 2A and 2B, the intermediate pressure turbine inlet pressure 41 is always at the pressure on the function generator (A) 42 or the function generator (B) 43, and stable low-pressure turbine bypass control is possible. It becomes. FIG. 2A and FIG. 2B show the function generator used in Example 1, comparing the functions during normal operation and high-pressure feed water heater bypass operation, and showing the relationship with the actual operation pressure. FIG. 2A shows the function generator (A) 42 during normal operation, and FIG. 2B shows the function generator (B) 43 when bypassing the high-pressure feed water heater.

  According to the present embodiment, in the event that the intermediate / low pressure turbine inlet pressure rises abnormally due to an increase in excess high pressure turbine exhaust steam, the relationship between the intermediate / low pressure turbine inlet pressure and the high pressure turbine first stage pressure is different from that during normal operation. Even when the balance is achieved, the low-pressure turbine bypass valve can be kept closed. In addition, when the intermediate / low pressure turbine inlet pressure rises and the thermal balance between the high pressure turbine first stage pressure and the intermediate / low pressure turbine inlet pressure changes, the control setting value of the intermediate pressure turbine inlet is adjusted to the heat balance at the time of this event. By switching to the pressure setting, it is possible to control the bypass valve stably even for operations such as load increase / stop while the heat balance is changed.

  FIG. 3 is a diagram showing a steam power plant system and a low-pressure turbine bypass control system to which one embodiment of the present invention is applied. The second embodiment has a function of catching the opening operation of the bleed stop valve and switching the function computing unit as the control setting.

  The outline of the second embodiment is the same as that of the first embodiment. The low-pressure turbine bypass valve is controlled by the pressure setting based on the turbine first stage pressure at the time of start / stop / emergency stop, and does not hinder the load operation at the normal load operation. Thus, by adding a bias to the pressure setting, the low-pressure turbine bypass valve is controlled to be fully closed. In the second embodiment, instead of opening the feed water heater bypass valve, the high-pressure turbine When the bleed stop valve installed in the bleed pipe from the intermediate stage to the feed water heater is closed, the displacement of the high pressure turbine increases, the medium and low pressure turbine inlet pressure rises, the high pressure turbine first stage pressure and the medium and low pressure turbine inlet pressure When the operation is continued with this thermal balance changed, the low-pressure turbine bypass valve is opened unnecessarily, causing disturbance to the turbine load. In order to avoid this, the setting of the pressure setting value (the pressure setting value at the inlet of the medium / low pressure turbine) is set based on the first-stage pressure of the high pressure turbine, which is calculated by calculating the heat balance after closing the bleeding stop valve. ) To be controlled.

  Hereinafter, it demonstrates in detail based on drawing. The basic configuration is the same as in FIG.

  In the second embodiment, instead of capturing the opening operation of the high pressure feed water heater bypass valve 28 of the first embodiment shown in FIG. 1, the bleed stop valve 32 installed in the bleed pipe 31 supplied from the high pressure turbine 7 is closed. The control setting is switched from the function generator (A) 42 used for low-pressure turbine bypass control during normal operation to the function generator (B) 43 calculated by heat balance calculation when the bleed valve is closed. . Thereby, even when the bleed valve is closed, the low pressure turbine bypass valve 12 can be controlled with the setting based on the heat balance as in the normal load operation.

  In addition, since the function generator (A) 42 and the function generator (B) 43 create a function based on the heat balance calculation under each load condition, the load condition changes due to load increase / decrease etc. As in the first embodiment, the intermediate pressure turbine inlet pressure 41 is always at the pressure on the function generator (A) 42 or the function generator (B) 43, and stable low-pressure turbine bypass control is possible.

  FIG. 4 is a diagram showing a steam power plant system and a low-pressure turbine bypass control system to which one embodiment of the present invention is applied. The third embodiment has a function of catching the opening operation of the process steam stop valve and switching the function computing unit as the control setting.

  The outline of the second embodiment is that a steam generator, a high-pressure turbine driven by steam generated from the steam generator, a reheater that heats exhaust steam of the high-pressure turbine, and reheat steam heated by the reheater Reheat heated by a reheater, having a high pressure turbine bypass pipe having a high pressure turbine bypass valve that bypasses the high pressure turbine and leads the steam from the steam generator to the high pressure turbine exhaust pipe A low-pressure turbine bypass pipe having a low-pressure turbine bypass valve that bypasses the medium- and low-pressure turbine and leads to the condenser, a high-pressure turbine, or a process steam pipe that supplies the extracted air from the exhaust pipe to be used in another facility such as a factory. Suppress the rise of reheat steam pressure at the reheater outlet in the transient operation state where surplus steam is generated at the start, stop, emergency stop, etc. For this purpose, a low-pressure turbine bypass control device that discharges surplus steam from the low-pressure turbine bypass pipe to the condenser and controls the intermediate-low pressure turbine inlet pressure with the low-pressure turbine bypass valve. It is controlled with a pressure setting based on the first stage pressure of the high-pressure turbine at the time of emergency stop, and is controlled to be fully closed by applying a bias to the pressure setting so that the load operation is not hindered during normal load operation, and The high-pressure turbine or the process steam supplying steam from the exhaust pipe is shut off, the displacement of the high-pressure turbine increases, the medium- and low-pressure turbine inlet pressure rises, and the relationship between the high-pressure turbine first stage pressure and the medium- and low-pressure turbine inlet pressure When the operation is continued with the normal pressure setting in a state where has changed, the low pressure turbine bypass valve becomes an unnecessary opening operation, In order to avoid disturbing the bin load, the process steam shut-off condition is taken and the pressure set value (at the low-pressure turbine inlet is set to the setting based on the first stage pressure calculated by the heat balance calculation after the process steam shut-off. The pressure setting value) is switched and controlled.

  Hereinafter, it demonstrates in detail based on drawing. The basic configuration is the same as in FIG.

  The plant to which the third embodiment is applied includes a process steam pipe 33 and a process steam stop valve 34 for supplying steam to another facility such as a factory to the extraction pipe 31 in the first and second embodiments shown in FIGS. It is an installed plant. In the third embodiment, instead of capturing the closing operation of the high pressure feed water heater bypass valve 28 and the bleed stop valve 32, the closing operation of the process steam stop valve 34 is captured and used for the low pressure turbine bypass control during normal operation. The control setting is switched from the function generator (A) 42 to the function generator (B) 43 calculated by the heat balance calculation in the process steam stop valve closed state. Thus, even when the process steam stop valve is closed, the low-pressure turbine bypass valve 12 can be controlled with the setting based on the heat balance as in the normal load operation.

  In addition, since the function generator (A) 42 and the function generator (B) 43 create a function based on the heat balance calculation under each load condition, the load condition changes due to load increase / decrease etc. As in the first embodiment, the intermediate pressure turbine inlet pressure 41 is always at the pressure on the function generator (A) 42 or the function generator (B) 43, and stable low-pressure turbine bypass control is possible.

1 ... Boiler, 2 ... Main steam pipe, 3 ... High pressure turbine bypass pipe, 4 ... High pressure turbine bypass valve, 5 ... Main steam stop valve, 6 ... Main steam control valve, 7 ... High-pressure turbine, 8 ... Low temperature reheat pipe, 9 ... Reheater, 10 ... High temperature reheat pipe, 11 ... Low pressure turbine bypass pipe, 12 ... Low pressure turbine bypass valve, 13・ ・ ・ Low temperature reducer, 14 ... Reheat steam stop valve, 15 ... Intercept valve, 16 ... Medium pressure turbine, 17 ... Low pressure turbine, 18 ... Condenser, ...・ Condensate pump, 20 ... Condensate pipe, 21 ... Temperature reduction water pipe, 22 ... Temperature reduction valve, 23 ... Deaerator water level control valve, 24 ... Low pressure feed water heater, 25 ..Deaerator, 26 ... Feed pump, 27 ... Feed pipe, 28 ... High pressure feed heater bypass valve, 29 ... High pressure feed heater bypass pipe, 30 ... High pressure feed heater 31 ... Extraction pipe, 32 ... Bleed stop valve, 33 ... Process steam pipe, 34 ... Process steam stop valve, 40 ... High pressure first stage pressure (pressure gauge), 41 ... Medium pressure turbine inlet pressure (pressure gauge), 42 ... -Function generator (A), 43 ... Function generator (B), 44 ... Signal switcher, 45 ... Adder, 46 ... Bias value (fixed value), 47 ... Deviation Calculator, 48 ... PI calculator

Claims (5)

Steam generator, high-pressure turbine driven by steam generated from the steam generator, reheater for heating exhaust steam of the high-pressure turbine, and medium-low pressure turbine driven by reheat steam heated by the reheater A condenser, a high-pressure turbine bypass pipe having a high-pressure turbine bypass valve for bypassing the steam from the steam generator to the high-pressure turbine exhaust pipe, and the reheat steam heated by the reheater A low-pressure turbine bypass pipe having a low-pressure turbine bypass valve that bypasses the medium-low pressure turbine and leads to the condenser, and a feed water heater that heats the feed water to the steam generator by the extracted steam from the intermediate stage of the high-pressure turbine And a steam generator bypass pipe having a feed water heater bypass valve that bypasses the feed water heater and guides feed water to the steam generator. Wherein a low-pressure turbine bypass valve controller controls the opening and closing of the low-pressure turbine bypass valve in cement,
The low-pressure turbine bypass valve is controlled to open and close so that the inlet pressure of the medium-low pressure turbine does not exceed the control set pressure of the inlet of the medium-low pressure turbine, which is set based on the initial stage pressure of the high-pressure turbine,
If the operation pressure differs from that during normal operation when the inlet pressure of the medium / low pressure turbine increases during normal load operation, the control set pressure is switched to a setting based on the heat balance calculation in that operation state. A low-pressure turbine bypass valve control device. In claim 1,
During normal load operation, when the water supply to the steam generator is switched to the feed water heater bypass pipe side from the feed water heater side, the control set pressure is bypassed the feed water heater. A low-pressure turbine bypass valve control device that switches to a setting based on a heat balance calculation in a state. In claim 1,
During normal load operation, when the extraction stop valve provided in the extraction pipe for introducing extraction steam from the intermediate stage of the high-pressure turbine to the feed water heater is closed, the control set pressure is set to the extraction stop valve. A low-pressure turbine bypass valve control device, wherein the setting is switched to a setting based on a heat balance calculation in an operating state in which the engine is closed. Steam generator, high-pressure turbine driven by steam generated from the steam generator, reheater for heating exhaust steam of the high-pressure turbine, and medium-low pressure turbine driven by reheat steam heated by the reheater A condenser, a high-pressure turbine bypass pipe having a high-pressure turbine bypass valve for bypassing the steam from the steam generator to the high-pressure turbine exhaust pipe, and the reheat steam heated by the reheater A low-pressure turbine bypass pipe having a low-pressure turbine bypass valve that bypasses the medium-low pressure turbine and leads it to the condenser, and a process for supplying extracted steam from the high-pressure turbine or the high-pressure turbine exhaust pipe to another facility such as a factory A low-pressure turbine bypass valve control device that controls opening and closing of the low-pressure turbine bypass valve in a steam generation plant having a steam pipe Te,
The low-pressure turbine bypass valve is controlled to open and close so that the inlet pressure of the medium-low pressure turbine does not exceed the control set pressure of the inlet of the medium-low pressure turbine, which is set based on the initial stage pressure of the high-pressure turbine,
In normal load operation, when the process steam pipe is shut off, the control set pressure is switched to the setting based on the heat balance calculation in the operation state where the process steam pipe is shut off. A low-pressure turbine bypass valve control device. Steam generator, high-pressure turbine driven by steam generated from the steam generator, reheater for heating exhaust steam of the high-pressure turbine, and medium-low pressure turbine driven by reheat steam heated by the reheater A condenser, a high-pressure turbine bypass pipe having a high-pressure turbine bypass valve for bypassing the steam from the steam generator to the high-pressure turbine exhaust pipe, and the reheat steam heated by the reheater A low-pressure turbine bypass pipe having a low-pressure turbine bypass valve that bypasses the medium-low pressure turbine and leads to the condenser, and a feed water heater that heats the feed water to the steam generator by the extracted steam from the intermediate stage of the high-pressure turbine A feed water heater bypass pipe having a feed water heater bypass valve that bypasses the feed water heater and guides the feed water to the steam generator, and start / stop / emergency Excess steam is discharged from the low-pressure turbine bypass pipe to the condenser so as to suppress an increase in reheat steam pressure at the outlet of the reheater in a transient operation state where surplus steam is generated such as when stopped, and the medium-low pressure turbine A power plant having a low-pressure turbine bypass control device for controlling an inlet pressure with the low-pressure turbine bypass valve,
The low-pressure turbine bypass control device controls the low-pressure turbine bypass valve with a pressure setting based on the first-stage pressure of the high-pressure turbine at the time of start / stop / emergency stop,
During normal load operation, the low pressure turbine bypass valve is controlled to be fully closed by applying a bias to the pressure setting,
When the operation state is different from the normal operation in which the inlet pressure of the medium / low pressure turbine rises during normal load operation, the pressure setting is switched to the setting based on the heat balance calculation in the operation state. A power plant characterized by

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