JP3909466B2 - Steam turbine operation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating a steam turbine, and in particular, to perform an operation for suppressing an increase in turbine rotational speed when loads of a plurality of turbines connected to a drive shaft of a generator are interrupted. The present invention relates to a method for operating a preferred steam turbine.
[0002]
[Prior art]
In power plants, and connected to the drive shaft of the steam generator and condenser respectively generator high pressure turbine and the intermediate pressure turbine and low pressure turbine disposed in the fluid flow path connecting a generator by the turbine A rotational drive system is adopted.
[0003]
In this type of system, when an accident occurs in an electric power system or the like connected to a generator, the load on the turbine is cut off. If the generator is driven to rotate by the turbine when the turbine load is interrupted, the turbine speed increases and the turbine may be damaged. When the turbine load is interrupted, the maximum turbine speed increases. A technique for reducing the rate is employed.
[0004]
For example, when the load on the turbine is cut off, the steam control valve disposed between the boiler and the high pressure turbine and the intercept valve disposed between the reheater and the intermediate pressure turbine are closed as soon as possible. Reduce the amount of steam flowing into the turbine, shorten the length of piping connecting the steam turbine and the high-pressure turbine, piping connecting the intercept valve and the intermediate-pressure turbine, and piping connecting the intermediate-pressure turbine and the low-pressure turbine. The volume of each pipe is reduced as much as possible to reduce the amount of steam remaining in each pipe, thereby reducing the amount of steam that overspeeds the steam turbine.
[0005]
However, even when the closing speeds of the steam control valve and the intercept valve are increased, considering the friction and inertia of the machine, it is almost in an extreme state, and it is difficult to increase the closing speed any more.
[0006]
Even if the volume of the pipe connecting the steam control valve and the high pressure turbine, the pipe connecting the intercept valve and the intermediate pressure turbine, and the pipe connecting the intermediate pressure turbine and the low pressure turbine is made as small as possible, It is difficult to shorten the length of each pipe.
[0007]
On the other hand, the steam turbine cost is reduced by shortening the blade length of the steam turbine or shortening the rotor diameter of the steam turbine, but when comparing steam turbines that generate the same output The reduction in the inertia weight due to the shortening of the blade length and the rotor diameter of the steam turbine contributes to the cost reduction. However, when the turbine load is cut off, the inertia weight is reduced to reduce the rotation speed of the turbine. Will rise excessively.
[0008]
Therefore, in order to reduce the amount of steam flowing into the turbine, for example, as described in JP-A-5146602, JP-A-55-146204, and JP-A-61-55303, a high pressure is used. A system in which steam flowing into a turbine is discharged to a condenser has been proposed.
[0009]
[Problems to be solved by the invention]
In the prior art, in order to reduce the amount of steam flowing into the steam turbine after shutting off the turbine load, the steam control valve is closed and the steam flowing into the high-pressure turbine is discharged to the condenser. Therefore, the amount of steam flowing into the high-pressure turbine can be reduced, and the increase in the speed of the steam turbine can be suppressed.
[0010]
However, in order to suppress the rotation speed of the steam turbine, it is possible to increase the rotation speed of the steam turbine only by closing the steam control valve after shutting off the turbine load and discharging the steam flowing into the high pressure turbine to the condenser. Is not enough to suppress.
[0011]
The subject of this invention is providing the operating method of the steam turbine which can suppress the raise of the rotational speed of a steam turbine more than when reducing only the quantity of the steam which flows in into a single turbine.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a plurality of turbines when loads of a plurality of turbines arranged in a fluid passage connecting a steam generator and a condenser and driving a generator are interrupted. Of the steam turbine that closes a control valve that controls the amount of steam that flows into the turbine that has a large influence on the rotational speed of the generator, and that discharges steam on the downstream side of the control valve to the condenser Is adopted.
[0013]
When adopting the operation method of the steam turbine, steam can be extracted from an extraction pipe provided in a turbine downstream of the control valve and discharged to the condenser.
[0014]
In addition, the present invention provides a turbine that is arranged in a fluid passage that connects a steam generator and a condenser, and when a load of the plurality of turbines that drive the generator is interrupted, A steam turbine operating method is employed in which the control valve for controlling the amount of steam flowing into the turbine is closed and the steam flowing into each of the plurality of turbines is discharged to the condenser.
[0015]
In this case, steam can be extracted from the extraction pipes provided in each of the plurality of turbines and discharged to the condenser.
[0016]
When employing the operation method of each steam turbine, steam having a pressure higher than that of the steam flowing into the low-pressure side turbine may be introduced before the final stage of the low-pressure side turbine among the plurality of turbines. it can.
[0017]
The present invention also provides a high-pressure turbine that drives a generator by being arranged in a fluid passage connecting a steam generator and a condenser in a system having a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine as a steam turbine. When the load of the pressure turbine and the low pressure turbine is interrupted, the steam control valve for controlling the amount of steam flowing into the high pressure turbine is closed and the steam downstream of the steam control valve is discharged to the condenser. The operation method of the steam turbine which extracts steam from the extraction pipe provided in the high-pressure turbine and discharges it to the condenser is adopted.
[0018]
In a system having a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine, when the steam turbine load is interrupted, the intercept valve that controls the amount of steam flowing into the intermediate-pressure turbine is closed, and the downstream side of the intercept valve Steam is discharged to a condenser, and steam is extracted from a bleed pipe provided in the intermediate pressure steam turbine and discharged to the condenser, or steam on the downstream side of the intermediate pressure turbine is discharged to the condenser It is possible to employ a method in which steam is extracted from an extraction pipe provided in the low-pressure turbine and discharged to the condenser.
[0019]
In a system having a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine as the steam turbine, an operation method is adopted in which steam having a pressure higher than that of the steam flowing into the low-pressure turbine is introduced before the final stage of the low-pressure turbine. Can do.
[0020]
According to the above-described means, while closing the control valve for controlling the amount of steam flowing into the turbine having a large influence on the increase in the rotational speed, for example, the influence on the rotational speed of the generator among the plurality of turbines, Since the steam on the downstream side of the control valve is discharged to the condenser, the work of the entire turbine can be reduced compared to when only the steam flowing into a single turbine is discharged to the condenser. It becomes possible to keep the maximum speed reaching rotation speed after the load is cut off low.
[0021]
In addition, the control valve for controlling the amount of steam flowing into the turbine is closed and the steam flowing into each of the turbines is discharged to the condenser, so that the steam flowing into the single turbine is recovered. The amount of work of the entire turbine can be reduced and the increase in the rotational speed of the steam turbine can be suppressed, and the maximum speed reaching rotational speed after the load is interrupted can be kept lower than when discharging to the water vessel. It becomes possible.
[0022]
In addition, steam is extracted from the extraction pipe provided in the turbine and discharged to the condenser, or steam higher in pressure than steam flowing into the low-pressure turbine is introduced before the final stage of the low-pressure turbine. As a result, the differential pressure between the turbines can be reduced to reduce the amount of work of the turbine, so that an increase in the rotational speed of the steam turbine can be further suppressed.
[0023]
In a system having a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine, after shutting off the load, the steam control valve is closed and the steam on the downstream side of the steam control valve is discharged to the condenser. Steam is extracted and discharged to the condenser, the intercept valve is closed, the steam on the downstream side of the intercept valve is discharged to the condenser, and steam is extracted from the extraction pipe of the medium-pressure turbine to the condenser. Steam that flows into a single turbine by discharging the steam downstream from the intermediate pressure turbine to the condenser, extracting steam from the extraction pipe of the low-pressure turbine, and discharging it to the condenser The amount of work of the entire steam turbine can be reduced and the increase in the rotation speed of the steam turbine can be suppressed, and the maximum speed reaching rotation after the load is cut off. It is possible to suppress the low.
[0024]
Furthermore, by introducing steam having a higher pressure than the steam flowing into the low-pressure turbine before the final stage of the low-pressure turbine, the work of the entire steam turbine can be further reduced, and the rotation speed of the steam turbine is increased. Can be further suppressed.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of a power plant to which the present invention is applied. 1, the power plant includes a boiler 10, a high-pressure turbine 12, an intermediate-pressure turbine 14, a double-flow low-pressure turbine 16, a generator 18, and a condenser 20. The high-pressure turbine 12, the intermediate-pressure turbine 14, and the low-pressure turbine The turbine 16 is disposed as a steam turbine in a fluid flow path connecting the boiler 10 and the condenser 20, and is connected to a drive shaft 22 of the generator 18.
[0026]
A reheater 24 is accommodated in the boiler 10 as a steam generator, and the boiler 10 is connected to the inlet side of the high-pressure turbine 12 via a pipe 26. The outlet side of the high pressure turbine 12 is connected to the reheater 24 of the boiler 10 via a pipe 28. The reheater 24 is connected to the inlet side of the intermediate pressure turbine 14 via a pipe 30, and the outlet side of the intermediate pressure turbine 14 is connected to the inlet side of the low pressure turbine 16 via a pipe 32.
[0027]
A steam control valve 34 is installed in the middle of the pipe 26, and an intercept valve 36 is installed in the middle of the pipe 30. The steam control valve 34 is configured as a control valve for controlling the amount of steam flowing into the high pressure turbine 12, and the intercept valve 36 is configured as a control valve for controlling the amount of steam flowing into the intermediate pressure turbine 14. A pipe 38 branched from the pipe 26 is connected to the downstream side of the steam control valve 34 of the pipe 26, and a pipe 40 branched from the pipe 30 is connected to the downstream side of the intercept valve 36 of the pipe 30. A pipe 42 branched from the pipe 32 is connected, and each pipe 38, 40, 42 is connected to the condenser 20. Dump valves 44, 46, and 48 for opening and closing the pipes are arranged in the middle of the pipes of the pipes 38, 40, and 42.
[0028]
Further, a pipe 50 branched from the pipe 28 is connected in the middle of the pipe 28, and the pipe 50 is connected to the condenser 20. A ventilator valve 52 is installed in the middle of the pipe 50. When the intercept valve 36 is fully closed (closed), the ventilator valve 52 causes wind damage to the high-pressure turbine 12 due to steam confined between the downstream side of the steam control valve 34 and the intercept valve 36. It is provided to prevent the turbine blades from being heated by the damage. That is, the turbine blades are prevented from being heated by opening the ventilator valve 52 when the intercept valve 36 is fully closed.
[0029]
A control device 54 is provided to control the opening / closing operation of the steam control valve 34, the intercept valve 36, the dump valves 44, 46 and 48, and the ventilator valve 52. The control device 54 monitors the current of the generator 18, and when the load of the steam turbine is interrupted, such as during a system fault, detects that the load is interrupted based on the current of the generator 18, and accompanies the load interruption. Thus, the steam control valve 34 and the intercept valve 36 are controlled to be fully closed, and the dump valves 44, 46 and 48 are controlled to be fully open.
[0030]
In the above configuration, the steam for driving the steam turbine is generated by the boiler 10, the steam generated from the boiler 10 is introduced into the high-pressure turbine 12 via the steam control valve 34, and the introduced steam causes the high-pressure turbine 12 to The steam that has worked and worked in the high-pressure turbine 12 flows into the reheater 24. At this time, the amount of steam flowing into the high-pressure turbine 12 is controlled to the amount of steam commensurate with the load of the generator 18 by the opening of the steam control valve 34.
[0031]
The steam flowing into the reheater 24 is heated by the reheater 24, and the heated steam normally flows into the intermediate pressure turbine 14 through the intercept valve 36 that is kept fully open during operation. The steam that has flowed into the intermediate pressure turbine 14 works in the intermediate pressure turbine 14, passes through the pipe 32, then flows into the low pressure turbine 16, and works in the low pressure turbine 16, and finally enters the condenser 20. Inflow. As the steam flows into each turbine and works, the generator 18 is rotationally driven. For example, the generator 18 rotates at a rated speed of 3000 rpm in a 50 Hz power system. In normal times, the dump valves 44, 46, 48 are fully closed.
[0032]
When an accident occurs in the power system connected to the generator 18 and the load of the steam turbine is cut off, the steam control valve 34 and the intercept valve 36 are controlled to be fully closed. In this case, if only the steam control valve 34 and the intercept valve 36 are fully closed, the rotation speed of the steam turbine is increased by the steam remaining on the steam control valve 34 downstream side and the intercept valve 36 downstream side.
[0033]
For example, when focusing on the high-pressure turbine 12, as shown in FIG. 2, even if the steam control valve 34 is controlled to be fully closed after the load is cut off, the rotation speed of the steam turbine is increased by the steam flowing into the high-pressure turbine 12. As for the energy, when the load is shut off, the energy resulting from the steam amount Q1 already downstream of the steam control valve 34 and the steam control valve 34 after the load is shut off, even if the steam control valve 34 is rapidly fully closed (closed state). There is energy due to the amount of steam Qcv flowing into the high-pressure turbine 12 due to the time delay until the state is reached. These energies are expressed by the following equation (1), and the rotational speed of the steam turbine is increased by the energy UOh contributing to this overspeed.
[0034]
UOh = ΔSh × (Qcv + Q1) (1)
here,
UOh = Energy Qcv given to the high-pressure turbine 12 after the load is interrupted and contributing to the overspeed of the high-pressure turbine = Steam flowing into the high-pressure turbine 12 due to a time delay until the steam control valve 34 is fully closed after the load is interrupted Amount Q1 = amount of steam remaining on the downstream side of the steam control valve 34 when the load is shut off ΔSh = a heat drop determined by a differential pressure between the inlet side and the outlet side of the high-pressure turbine 12 In the present embodiment, In order to reduce UOh, the steam control valve 34 is fully closed and the dump valve 44 is controlled to be fully open.
[0035]
Specifically, as shown in FIG. 3 (a), the steam control valve 34 is controlled to a fully closed state and the dump valve 44 is controlled to a fully open state as the load is interrupted. When such control is performed, as shown by a broken line, the dump valve 44 is fully opened, so that the steam flowing into the high-pressure turbine 12 is allowed to flow into the condenser 20 until the steam control valve 34 is fully closed. The amount of steam flowing into the high-pressure turbine 12 can be reduced. In contrast, when the dump valve 44 is not fully opened, the amount of steam flowing into the steam turbine 12 exists even after the steam control valve 34 is fully closed, as shown by the solid line.
[0036]
That is, conventionally, as shown in FIG. 3B, at the moment when the steam control valve starts to close after the load is cut off, the steam control valve is closed because there is a steam flow in the rated state downstream of the steam control valve. After starting, the steam amount decreases after a certain time delay T.
[0037]
In contrast, according to the present embodiment, as shown in FIG. 3A, after the load is interrupted, the steam control valve 34 is controlled to a fully closed state, and the dump valve 44 is fully opened to control the steam. Since the steam on the downstream side of the valve 34 is extracted instantaneously, after the load is shut off, the amount of steam on the downstream side of the steam control valve 34 starts to rapidly decrease. As a result, after the load is shut off, The amount of inflowing steam can be reduced.
[0038]
In consideration of the above, in the present embodiment, after the steam turbine load is cut off, the steam control valve 34 and the intercept valve 36 are controlled to be fully closed, and the dump valves 44, 46, and 48 are controlled to be fully open. The steam on the downstream side of the steam control valve 34, the downstream side of the intercept valve 36, and the downstream side of the intermediate pressure turbine 14 is discharged to the condenser 20.
[0039]
After shutting off the load of the steam turbine, the steam control valve 34 and the intercept valve 36 are controlled to be fully closed, and the dump valves 44, 46, and 48 are controlled to be fully open so that the steam control valve 34 downstream side and the intercept valve 36 downstream side are controlled. By controlling the discharge of the steam on the downstream side of the intermediate pressure turbine 14 to the condenser 20, the amount of steam flowing into the high pressure turbine 12, the intermediate pressure turbine 14, and the low pressure turbine 16 can be reduced, and the steam The work of the entire turbine can be reduced, the increase in the rotation speed of the steam turbine can be suppressed, and the maximum speed reaching rotation speed after the load is interrupted can be suppressed low.
[0040]
In the present embodiment, the steam control valve 34 and the intercept valve 36 are controlled to be fully closed and the dump valves 44, 46, and 48 are controlled to be fully open after the load of the steam turbine is interrupted. Instead of fully opening the dump valve, the control valve for controlling the amount of steam flowing into the turbine having a large influence on the increase in the rotational speed of the generator 18, for example, the intercept valve 36 is closed (fully closed), Even when the steam control valve 34 is closed and the dump valves 44 and 46 are controlled to be fully open, the work of the entire steam turbine can be reduced as compared with the case where only the steam flowing into the single turbine is discharged to the condenser. Can be reduced.
[0041]
In particular, when the work loads of the steam turbine 12, the intermediate pressure turbine 14, and the low pressure turbine 16 are 30:30:40, respectively, the steam control valve 34 and the intercept valve 36 are fully closed and the dump valves 44 and 46 are fully opened. By controlling the state, the work amount of the entire steam turbine can be reduced.
[0042]
When a turbine in which the intermediate pressure turbine 14 and the low pressure turbine 16 are integrated is used, the steam turbine 34 and the intercept valve 36 are fully closed and the dump valves 44 and 46 are controlled to be fully open. The work of the entire steam turbine can be reduced.
[0043]
Further, when each of the high pressure turbine 12, the intermediate pressure turbine 14, and the low pressure turbine 16 is provided with an extraction pipe, steam is extracted from each extraction pipe and discharged to the condenser 20 to reduce the work of the entire steam turbine. It can be further reduced.
[0044]
Further, by introducing steam having a pressure higher than that of the steam flowing into the low-pressure turbine 16, for example, steam downstream of the intercept valve 36, into the front side of the final stage blades of the low-pressure turbine 16, the intermediate-pressure turbine 14 and the low-pressure turbine The differential pressure between 16 can be lowered, and the work of the entire steam turbine can be further reduced.
[0045]
【The invention's effect】
As described above, according to the present invention, the control valve that controls the amount of steam flowing into the turbine having a large influence on the rotational speed of at least the generator among the plurality of turbines is closed and the control valve downstream Since the steam on the side is discharged to the condenser, the work of the entire turbine can be reduced compared to when only the steam flowing into a single turbine is discharged to the condenser. It becomes possible to keep the maximum speed at a later maximum speed low.
[Brief description of the drawings]
FIG. 1 is a system diagram of a power plant to which the present invention is applied.
FIG. 2 is a diagram for explaining energy acting on a high-pressure turbine after load interruption.
FIGS. 3A and 3B are diagrams for explaining the amount of steam flowing into the turbine after the load is cut off, in which FIG. 3A is a characteristic diagram according to the present invention, and FIG. 3B is a conventional characteristic diagram;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Boiler 12 High pressure turbine 14 Medium pressure turbine 16 Low pressure turbine 18 Generator 20 Condenser 24 Reheater 34 Steam control valve 36 Intercept valve 44, 46, 48 Dump valve 54 Control apparatus

Claims (7)

When loads of a plurality of turbines arranged in a fluid passage connecting a steam generator and a condenser to drive a generator are interrupted, an influence on at least the rotation speed of the generator among the plurality of turbines is reduced. The control valve for controlling the amount of steam flowing into the large turbine is closed, the steam on the downstream side of the control valve is discharged to the condenser, and the turbine on the low pressure side is placed in front of the final stage of the low pressure side turbine. A steam turbine operating method, wherein steam having a pressure higher than that of the steam flowing into the steam is introduced .   2. The steam turbine operating method according to claim 1, wherein steam is extracted from an extraction pipe provided in a turbine downstream of the control valve and discharged to the condenser. The amount of steam that flows into any of the plurality of turbines when the loads of the plurality of turbines that are arranged in the fluid passage connecting the steam generator and the condenser and drive the generator are interrupted And the steam that flows into each of the plurality of turbines is discharged to the condenser, before the final stage of the low-pressure side turbine, and more than the steam that flows into the low-pressure side turbine. A steam turbine operating method characterized by introducing steam at high pressure .   4. The steam turbine operating method according to claim 3, wherein steam is extracted from an extraction pipe provided in each of the plurality of turbines and discharged to the condenser. The amount of steam that flows into the high-pressure turbine when the loads of the high-pressure turbine, medium-pressure turbine, and low-pressure turbine that are disposed in the fluid passage connecting the steam generator and the condenser and drive the generator are interrupted. Closing the steam control valve to be controlled, discharging steam on the downstream side of the steam control valve to the condenser, extracting steam from an extraction pipe provided in the high-pressure turbine, and discharging the steam to the condenser ; A steam turbine operating method , wherein steam having a pressure higher than steam flowing into the low-pressure turbine is introduced to a front side of a final stage of the low-pressure turbine . The amount of steam that flows into the intermediate pressure turbine when the load of the high pressure turbine, the intermediate pressure turbine, and the low pressure turbine that are disposed in the fluid passage connecting the steam generator and the condenser and drives the generator is interrupted Closing the intercept valve for controlling the steam, discharging the steam downstream of the intercept valve to the condenser, extracting the steam from a bleed pipe provided in the intermediate pressure turbine and discharging it to the condenser , A steam turbine operating method , wherein steam having a pressure higher than steam flowing into the low-pressure turbine is introduced to a front side of a final stage of the low-pressure turbine . When the load of the high-pressure turbine, the intermediate-pressure turbine, and the low-pressure turbine that are arranged in the fluid passage connecting the steam generator and the condenser and drives the generator is interrupted, the steam on the downstream side of the intermediate-pressure turbine is Discharge to the condenser, extract steam from an extraction pipe provided in the low-pressure turbine, and discharge the steam to the condenser. The pressure before the final stage of the low-pressure turbine is higher than the steam flowing into the low-pressure turbine. A method for operating a steam turbine, characterized by introducing high steam .

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