JPH0223207A - Control device for steam turbine - Google Patents

Abstract

PURPOSE:To hold a settled speed governing rate constant during all sliding pressure operations by providing a movable supporting point on the lever of a reversion mechanism to a governor rotational pilot value, and changing the supporting point position in response to a main steam pressure. CONSTITUTION:A lever a9 in a lever mechanism containing the lever a10 of a reversion mechanism to the sleeve of a governor rotational pilot value (not shown in the figue) is supported by a movable supporting point 21 whose position is controlled in its movement by a supporting point position control device 20. Namely, a pin 23 provided on the upper end part of the movable supporting port 21 is engaged with a long groove 22 formed on the central part of the lever a9, and the lower part of the movable supporting point 21 is screwed in a driving screw shaft 28, while the movable supporting point 21 is moved in the axial direction of the screw shaft 28 by the rotation of the driving shaft 28 which is driven by a motor 30. In addition, the output of a supporting point position detecting device 33 connected to the movable supporting point 21 through a connecting rod 32, is inputted into a controller 35 together with the output of a steam pressure detector 37, to contribute to the control of the motor 30.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention maintains the exhaust steam amount of a turbine constant regardless of fluctuations in the load of the steam turbine, and also maintains a constant speed regulation rate of the turbine. The present invention relates to a steam turbine control device that is capable of always maintaining a constant value.

(Prior Art) Generally, a steam turbine plant that supplies electric power to a small area and uses its exhaust steam for purposes such as a water supply plant is well known.

FIG. 3 is a schematic configuration diagram of a steam turbine plant,
Main steam generated in the boiler 1 is supplied to the steam turbine 4 via the main steam stop valve 2 and the steam control valve 3. The steam supplied to the steam turbine 4 performs work in the steam turbine 4 to drive the generator 5, and then is discharged from the steam turbine 4 as exhaust steam. This exhaust steam is then supplied to the water supply plant 6.

Incidentally, the power demand for such a steam turbine generally tends to be high during the day and low at night, and the load on the turbine fluctuates. Therefore, the load on the turbine is controlled by controlling the opening and closing of the steam control valve 3 in accordance with the fluctuations in the load and changing the main steam meteor.

However, in the water supply plant 6, it is necessary to maintain the amount of exhaust steam constant in order to keep the amount of fresh water constant. However, as mentioned above, if the main steam flow rate is changed according to the load, there is a problem that the exhaust steam amount of the turbine will not be constant. Therefore, in a steam turbine equipped with a water supply plant, load control is performed by changing the main steam flow rate. I can't.

Therefore, in order to deal with this, the main steam pressure is changed according to the load on the turbine, and during high load times when there is a lot of electricity demand during the day, the main steam is brought to the normal rated pressure on the boiler side from the steam control valve to the steam turbine. On the other hand, during low-load periods when electricity demand is low at night, low-pressure main steam whose pressure is lowered on the boiler side is supplied to the steam turbine via a steam control valve in response to the decrease in turbine load. There is.

Figure 4 shows the difference between high-load operation using high-pressure steam during the day (hereinafter referred to as daytime rated load) and nighttime low-load operation using low-pressure steam (hereinafter referred to as nighttime rated load). This will be explained using the flow rate characteristics of the valve.

Figure 4 is a diagram showing the flow rate characteristics of a steam regulating valve in a plant equipped with four steam regulating valves, where curve A is at daytime rated load, curve B is at nighttime rated load, and curve C is under load. Shows the flow rate characteristics during fluctuations.

Further, points A, 9, C and 2 indicate the opening positions of the steam control valves from the first valve to the fourth valve, and point E indicates the fully open position of each steam control valve. The operating position α1 during the daytime rated load shown by curve A is controlled by the second valve, and the third and fourth valves remain idle. Further, the operating position α2 during low pressure operation at the rated load of discoloration shown by curve B is controlled by the fourth valve, and the steam control valve is almost fully open. The flow characteristics are determined so that the main steam flow rate at each operating position is kept substantially constant, and in this case, the rated main steam flow rate is controlled to Ql. By controlling the pressure value of the main steam and the opening degree of the steam control valve in this way, the amount of exhaust steam is always maintained at a constant value.

FIG. 5 is a diagram showing a control device for a steam control valve in a conventional steam turbine. Control from the start of the steam turbine to around the rated rotational speed is performed by a starter device 10. That is, when the starting device 10 is driven by the starting device motor 11, the auxiliary pilot valve 12 is operated in the opening direction, and the control oil flows from the boat 12a of the auxiliary pilot valve 12 to the port 12b, and the governor rotation pilot valve 13 inlet port 13a. At this time, since the rotational speed of the steam turbine is 0, the valve body of the governor rotation pilot valve 13 is positioned upward in the figure due to the action of the governor 14, and the inlet boat 13a is communicated with the outlet boat 13b. ing. Therefore, the control oil supplied to the inlet port 13a is supplied to the piston lower chamber 17a of the speed relay 15 via the outlet port 13b.

As a result, the piston rod of the speed relay 15 rises, the upper lever a1 is pushed up, and the steam control valve oil cylinder pilot valve 1
Valve body 6 is pushed down. Therefore, port 16a
is connected to the boat 16b, and control oil is supplied to the steam control valve oil cylinder 17.
The steam control valve 3 is controlled in the opening direction via the piston rod 17b and the lux shaft c2.

On the other hand, the movement of the piston rod 17b is fed back to the steam control valve oil cylinder pilot valve 16 via the lever a4. Further, the movement of the speed relay 15 is fed back to the auxiliary pilot valve 12 via the lever a5, the torque shaft C3, the lever a6, and the lever a7 whose one end is connected to the starting device 10, and further the torque shaft C lever a8, Link b3, lever a9, link b lever a10 to governor rotation pyro 4
It is fed back to the sleeve 13c of the cut valve 13.

In this way, when the steam control valve 3 reaches a predetermined opening degree and the rotational speed of the turbine reaches the rated rotational speed, the valve body of the governor-like rotary pilot valve 13 is lowered by the action of the governor 14, and the inlet port 13a is closed, the supply of control oil to the speed relay 15 is stopped, and the steam control valve 3 is controlled to a predetermined opening degree.

The control from the above rated rotation speed to the rated load is performed by the starting device 1.
This is done by the synchronizer 18 after fully opening 0. That is, when the synchronizer 18 is actuated by the synchronizer drive motor 19, lever a1 link b5, lever a
Sleeve 1 of governor rotating pilot valve 13 through lo
3c is pushed down, and the inlet port 13a becomes the outlet port 1.
3b, control oil is again supplied to the piston lower chamber 15a of the speed relay 15, and the steam control valve 3 is controlled in the opening direction in the same manner as described above.

By the way, in the control system of the steam turbine as described above, as is generally known, the speed change when the rated load is changed to no load, that is, the settling speed adjustment rate is 3 to 5% of the rated speed.
This is the governor-like rotary pilot valve 13.
and the steam control valve 3.

On the other hand, if a load shedding occurs during operation at the daytime rated load operating position α1, the opening degree of the steam control valve 3 changes to the daytime no-load operating position β1, as shown in FIG. The amount of change in the opening degree of the steam control valve at this time is θ1. and,
The settling speed adjustment rate is adjusted to 5% so that the turbine settling rotation speed at this time is about 105%. On the other hand,
If a load interruption occurs during operation in a state where the operation position has shifted to the operating position α2 during the rated load at night, the opening degree of the steam control valve 3 changes until it reaches the operating position β2 during the no-load operation at night.

That is, the amount of change in the opening degree of the steam control valve at this time is θ2. Therefore, between daytime and nighttime, the amount of change in the opening degree of the steam control valve during load shedding will change approximately three times as much from θ1 to θ2. Therefore, since the settling speed adjustment rate is adjusted to 5% when the amount of change is θ1, the settling speed adjustment rate when the amount of change in the opening degree of the steam control valve at night is θ2 is approximately three times as high as 15%.

(Problem to be Solved by the Invention) As described above, in a steam turbine control device that is capable of keeping the exhaust steam amount constant in two types of high-load operation and low-load operation, daytime and nighttime, When the settling speed regulation rate is adjusted to 5% during operation, the lever ratio between the governor-like rotary pilot valve and the steam control valve is constant, so the settling and constant speed regulation rate is approximately 3 times as large during nighttime operation. It becomes 15%. Therefore, if a load shedding occurs during rated load operation at night, the turbine's settling rotation speed will be approximately 115%, and the turbine overspeed will be 11% of the emergency governor's set surface rotation speed.
There is a problem in that when the speed greatly exceeds 0%, the emergency governor operates, leading to a turbine trip.

The same applies when the amount of change θ3 in the opening degree of the steam control valve is large when the load is changed.

In view of these points, the present invention is capable of always keeping the exhaust steam amount constant, and even if the turbine load fluctuates, the settling speed adjustment rate can always be kept constant during different rated load operations during the day and night. The purpose of this invention is to obtain a control device for a steam turbine.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a steam turbine that can perform variable pressure operation by changing the main steam pressure in accordance with the load, and can also maintain a constant amount of exhaust steam. In this control device, a moving fulcrum is provided in a lever system in a mechanism for restoring a governor-like rotary pilot valve to a sleeve whose operation is controlled by a synchronizer, and the fulcrum is moved by moving this moving fulcrum along the longitudinal direction of the lever. A device, a position detector that detects the position of the moving fulcrum, a function calculator that calculates the position of the moving fulcrum that keeps the settling speed adjustment rate constant according to the pressure signal of the main steam pressure, and this function calculator. and a controller that outputs a control signal to the fulcrum moving device based on a deviation signal between the calculated signal and the detection signal of the position detector.

(Function) When the main steam pressure is changed in order to shift from daytime operation to nighttime operation, the position of the moving fulcrum that keeps the settling speed adjustment rate constant is calculated by the function calculator according to the change in main steam pressure. , it is compared with the position of the moving fulcrum, and the deviation signal activates the fulcrum moving device, the position of the moving fulcrum of the lever system is moved, and the settling speed adjustment rate is adjusted so that it is always constant during variable pressure operation. Ru.

(Example) The present invention will be described below with reference to FIGS. 1 and 2. Note that the same parts as in FIG. 5 are given the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 1, a lever a9 in the lever system of the mechanism for restoring the governor rotation pilot valve 13 to the sleeve 13c is supported by a movable fulcrum 21 whose position is controlled by a fulcrum position control device 20.

FIG. 2 is an enlarged explanatory view of the lever a9 and the fulcrum position control device 20. The lever a9 has a long groove 22 in the longitudinal axis direction formed in the center thereof.
A pin 23 provided at the upper end of the movable fulcrum 21 is engaged with the movable fulcrum 21, and the movable fulcrum 21 is movable along the lever a9. Further, one end of the lever a9 is pivotally connected to a ring b3, and the other end is pivotally connected to the lower end of a link b4 connected to one end of the lever a1o connected to the sleeve 13c of the governor rotation pilot valve 13. ing. The connecting bin 24 that connects the lever a9 and the ring b4 is
Guide 25 erected in a direction substantially perpendicular to lever a9
The lever a is engaged with a long groove 26 extending in the axial direction of the lever a.
9 should not move left or right.

The lower part of the movable fulcrum 21 is screwed onto a drive screw shaft 28 which is supported by a bearing 27.
Two gears are fixed to one end of 8, and a drive gear 31 driven by a motor 30 is meshed with the gear 29.

Furthermore, the mobile branch 21 is connected to a fulcrum position detection device 33 via a link 32, and the position signal of the movable fulcrum detected by the fulcrum position detection device 33 is input to the controller 351 via a demodulator 34. It is intended to be done.

On the other hand, a pressure detector 37 is connected to the main steam pipe 36 that supplies the main steam generated in the boiler 1 to the steam turbine 4 on the upstream side of the main steam stop valve 2. The pressure signal is input to the function calculator 38,
Therefore, the position of the moving fulcrum that makes the settling speed adjustment rate corresponding to the above pressure become 5% is calculated and output. In other words, in this main steam turbine, the opening degree of the steam control valve changes according to changes in the main steam pressure, as shown in Figure 4, and the main steam pressure and the amount of change in the opening degree of the steam control valve have a functional relationship. be. Therefore, if the settling speed adjustment rate, which depends on the amount of change in the opening degree of the steam control valve, is constant at 5%, then
Since the settling speed adjustment rate is determined by the lever ratio, the value of the main steam pressure and the position of the moving support point 21 that determines the lever ratio also have a functional relationship. Therefore, the steam function calculator 38 is designed to calculate and output the moving fulcrum position corresponding to the main steam pressure based on the above functional relationship so that the settling speed adjustment rate becomes 5%. There, the above function calculator 3
The position setting signal calculated in step 8 is sent to the controller 35.
There, the deviation signal is inputted to the position signal and compared with the position signal of the moving fulcrum, and the motor 30 is driven and controlled based on the deviation signal.

However, during daytime rated load operation when electricity is often required,
The moving fulcrum 21 is fixed at the solid line position, and the lever a9 is controlled to swing around the bin 23.

In this case, the position of the moving fulcrum is set so that the settling speed adjustment rate is 5% as described above. In this case, when the opening degree of the steam control valve is controlled, the lever a
9 swings around the bin 23, and the connecting pin 2
4 moves along the long groove 26, the lever a9 moves slightly to the left in the figure, but this leftward movement component is absorbed by the gap W between the end of the long groove 22 and the bottle 23.

Therefore, when the main steam pressure is reduced when switching from daytime to nighttime operation, the function calculator 38 selects the movable fulcrum 2 corresponding to the pressure according to the drop in main steam pressure.
1 is calculated, the calculated signal and the position signal of the moving fulcrum are compared by the controller 35, and the deviation signal is manually input to the motor 30. Therefore, the motor 30 is rotationally driven and the drive screw shaft 28 is rotated via the drive gear 31 and the gear 29, and this rotation moves the moving fulcrum 21 to the dotted line position in FIG. 2, and the lever a9 is supported at that position. will be done.

Therefore, even if the lever ratio of lever a9 is changed and the steam control valve opening degree at load shedding during nighttime rated load changes by the amount of change θ2, the settling speed adjustment rate will be 5% and the turbine after load shedding will be The settling rotation speed is about 1 for the same material as during the day.
05%.

Further, as described above, even during pressure changes, the moving fulcrum is moved to the optimum position in accordance with the pressure each time, so the settling speed adjustment rate is always maintained at 5% even during this period.

〔Effect of the invention〕

As explained above, in the present invention, a moving fulcrum is provided on the lever of the restoration mechanism to the governor-like rotary pilot valve, and the fulcrum position is changed according to the main steam pressure.
During daytime and nighttime operation, and during all transformation operations,
The lever ratio changes in response to the amount of change in the opening degree of the steam control valve at the time of load cutoff, making it possible to keep the settling speed adjustment rate constant. Therefore, even if a negative 6I cutoff occurs under these operating conditions, it is possible to prevent the turbine from overspeeding.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the steam turbine control device of the present invention, Fig. 2 is an enlarged explanatory diagram of the fulcrum moving device shown in Fig. 1, and Fig. 3 is a system diagram of a general steam turbine plant. ,
FIG. 4 is a diagram showing flow characteristics of a steam control valve during variable pressure operation, and FIG. 5 is a system diagram of a conventional steam turbine control device. 3...Steam control valve, 10...Starting device, 12...
Auxiliary pilot valve, 13... Speed governor-like rotary pilot valve, 14... Speed governor, 15... Speed relay, 16...
・Steam control valve oil cylinder pilot valve, 17... Steam control valve oil cylinder, 18... Synchronizer, 20... Fulcrum position control device, 21... Moving fulcrum, 22... Long groove, 23...・・・
Bin, 24...Connection pin, 25...Guide, 28.
... Drive screw, 30... Motor, 33... Fulcrum position detection device, 35... Controller, 37... Pressure detector, 38... Function calculator.

Claims (1)

[Claims] In a steam turbine control system that can perform variable pressure operation by changing the main steam pressure according to the load, and can also maintain a constant amount of exhaust steam, the operation is controlled by a synchronizer. A moving fulcrum is provided in the lever system in the mechanism for restoring the governor rotation pilot valve to the sleeve, and a fulcrum moving device is provided to move this moving fulcrum along the length of the lever, and the position of the moving fulcrum is detected. a function calculator that calculates the position of a moving fulcrum that keeps the settling speed adjustment rate constant according to the pressure signal of the main steam pressure, and a calculation signal of the function calculator and detection of the position detector. A control device for a steam turbine, comprising: a controller that outputs a control signal to the fulcrum moving device based on a deviation signal from the fulcrum moving device.