JPH0326804A - Steam turbine controller - Google Patents

Abstract

PURPOSE:To operate a speed governor with slight delay even if load dump occurs during load limiter operation by providing a pressure switch and a timer on an oil path between an auxiliary pilot valve and a governor rotating pilot valve. CONSTITUTION:A pressure switch 27 is provided on an oil path A between an auxiliary pilot valve 12 and a governor rotating pilot valve 28 wherein ON/OFF signal of the pressure switch 27 is input to a synchronous apparatus driving motor 14 as open/close signal by electric signals (E), (F). The electric signals (E), (F) are equipped with a timer 29. The pressure switch 37 determines either load limiter operation or governor operation, and the timer 39 positions the opening degree of a synchronous apparatus 13 slightly higher than the opening degree of a start-up apparatus 15 even during load limiter operation. Thus a governor can be operated with only slight delay even if load dump occurs during load limiter operation. Therefore excessive speed of a turbine can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a steam turbine control device that maintains a constant amount of exhaust steam regardless of the load on the steam turbine.

(Prior Art) Steam turbine plants that generally supply electricity to a small area and utilize exhaust steam for applications such as water production plants are well known. FIG. 4 shows the flow of steam in the steam turbine plant. Main steam 6 generated in the boiler 2 is guided to the steam turbine 1 via the main steam stop valve 3 and the steam control valve 4, and After doing work to operate the turbine and drive the generator 5, the steam is discharged outside the steam turbine 1 as exhaust steam 24. Furthermore, this exhaust steam 24 is intended to be utilized in a water production plant (not shown). Also, steam turbine
The rotation speed and load control is performed by detecting the rotation speed of the steam turbine rotor 8 with the speed governor 7 and sending a signal to the steam control valve 4.

On the other hand, the electric power generated by the generator 5 is transmitted to the circuit breaker 11a,
Power is supplied to the internal system 9 and external system 10 via the llb. In this external system IO, when the power in a small region or the entire country is low, the frequency is unstable and fluctuates greatly even with a slight change in load.

Conventionally, the power demand for such steam turbines generally tends to be high during the day and low at night. In this case where the load on the turbine fluctuates, the load on the turbine is controlled by changing the main steam flow rate by controlling the opening and closing of the steam control valve 4, and the main steam flow rate changes in accordance with the load.

However, in a water production plant, it is desirable to maintain a constant amount of exhaust steam in order to keep the amount of water produced constant, and if the main steam flow rate is changed according to the load as described above, the exhaust steam of the turbine will be reduced. There is a problem that the amount becomes unstable. In a steam turbine equipped with a water production plant in such a state, load control cannot be performed by changing the main steam flow rate.

Therefore, the main steam pressure is changed in response to the load on the turbine, and when there is a lot of power demand during the day (during high load), the main steam pressure is changed from the main steam control valve 4 to the normal rated pressure on the boiler side to the steam turbine 1. Eight inflows. = On the other hand, when the power demand is low at night (low load), low-pressure main steam whose pressure has been lowered on the boiler side is caused to flow into the steam turbine 1 from the steam control valve 4 in response to the decrease in turbine load. The main steam 6 has different pressures, and the steam that has flowed into the steam turbine 1 is
After doing work and driving the generator 5, it is discharged as exhaust steam 24, and this exhaust steam 24 is used in a water production plant.

Here, the difference between high-load operation using high-pressure steam during the day (hereinafter referred to as daytime rated load) and low-load operation using low-pressure steam at night (hereinafter referred to as nighttime rated load) is shown in Figure 5. This will be explained using the flow characteristics of the steam control valve 4. This shows the flow rate characteristics of the steam control valve 4. The flow rate characteristic due to high pressure steam in the daytime is 25a, and the flow rate characteristic due to low pressure steam at night is 25a.
It is 5b.

The operating position 26a during the daytime rated load is controlled at a low opening degree of the steam control valve, and the operating position 26a during the rated load during the night is controlled at a low position.
26b is controlled at a position where the steam regulating valve opening degree is high (almost fully open position), and the flow rate characteristics are determined so that the steam flow rate at each rated operating position is approximately constant.Here, the rated steam flow rate is Z.

As mentioned above, switching from daytime to nighttime operation is as follows:
In the boiler 2 of FIG. 4, the opening degree of the steam control valve 4 is shifted from 26a to 26b while lowering the pressure of the main steam 6. Conversely, when switching from nighttime to daytime rated operation, the steam control valve opening degree is shifted from 26b to 26a while increasing the pressure of the main steam 6. That is, the amount of change in the opening degree of the steam control valve due to variable pressure operation is W. Therefore, in order to keep the amount of water produced in the above-mentioned water production plant constant, it is possible to maintain the amount of exhaust steam constant.

Next, a control device for the above-mentioned steam control valve 4 will be explained with reference to FIG. Control of the steam turbine from startup to around the rated rotational speed is performed by controlling the startup device 15 with a startup device drive motor l6,
The control oil 20 is supplied to the lower part of the piston of the speed relay 17 through the auxiliary pilot valve l2, the governor rotating pilot 1, and the valve 28. When the speed relay l7 pushes up the upper lever 21h, the steam control valve/oil cylinder pilot valve l8
The control oil 20 is supplied to the lower part of the piston of the steam control valve oil [1.9]. Therefore, the steam control valve oil cylinder 19 opens and the steam control valve 4 opens. 21k is provided, and only the control signal of the starter drive motor 16 opens the steam control valve 4 to control the main steam flow rate.

When the rotational speed of the turbine increases to around the rated rotational speed in this manner, the governor rotation pilot valve 28 lowers and blocks the pilot valve boat, so that control oil no longer flows. After that, control from around the rated rotation speed to the rated load is performed by fully opening the starting device with the drive motor 16, then controlling the synchronizer 13 with the synchronizer drive motor 14, and controlling the governor rotation pilot valve 28. Control oil 20 by lowering the sleeve
is again supplied to the r section of the speed relay 17, and the steam regulating valve oil cylinder 19 and the steam regulating valve 4 are further opened to control the main steam flow rate.

As explained above, the cantering motor 1 that moves the starting device
The opening degree of the steam control valve is controlled by the drive motor 14 that operates the synchronizer 5 and the synchronizer. In addition, changes in load are detected by the rotary pilot valve 28 in response to power demand, and the steam control valve 4
Controls the opening degree. As explained earlier, in plants where the system is unstable and the frequency fluctuates greatly due to this load change, the generally well-known synchronizer is fully opened by the drive motor 14,
Load limiter operation is performed to control the load using the drive motor 16 that moves the starter device. This has the advantage that changes in the external system can be operated without causing disturbance to the control system of this plant, but
During load limiter operation, when a load shedding occurs, the synchronizer is in the fully open position, so the governor does not operate immediately, and the turbine is overspeeded and the rotary pilot valve is adjusted only after it has fallen to the fully open position of the synchronizer. As a result, the turbine is likely to overspeed, exceeding the set rotation speed of 110% of the emergency governor (not shown), causing the emergency governor to operate and tripping the turbine.

In particular, there is a special operation in which the opening of the steam control valve is shifted from daytime to nighttime and from nighttime to daytime during variable pressure operation, and at least during this period, load limiter operation is performed to prevent disturbances from being applied to the control system. There is a need.

(Problem to be solved by the invention! i) In the above-mentioned plant, during variable pressure operation and during the transition of the steam control valve opening from daytime to nighttime and from nighttime to daytime, disturbances from the external system are applied to the control system. Use a load limiter to prevent this.

When this load shedding occurs, the governor does not work at first, so the turbine tends to overspeed, which not only puts the turbine at risk, but also causes the emergency governor to operate, causing the turbine to trip, which is a major problem. ．． The purpose of the present invention is to operate the speed governor with only a slight delay even if a load shedding occurs during load limiter operation when switching from daytime to nighttime, suppress the overspeed of the turbine, and prevent the emergency speed governor from operating. To provide a steam turbine control device that can maintain safety without operating the steam turbine.

[Structure of the invention]

(Means for Solving the Problems) A steam turbine control device according to the present invention is a water generating system that utilizes exhaust steam from a steam turbine. #1: In a steam turbine control device that maintains a constant amount of steam, the steam control valve opening degree is changed during the variable pressure operation. The range of change is set to load limiter operation, and a pressure switch and timer are installed in the oil passage between the auxiliary pilot valve and the governor rotation pilot valve, and the setting of this timer changes the opening of the synchronizer to the opening of the starter. It is characterized by being configured so that it is positioned slightly higher than the above.

(Function) In the present invention, by providing a pressure switch, an electric signal, and a timer, changes in the pressure of the oil passage between the auxiliary pilot valve and the governor rotation pilot valve are detected, and the change in pressure of the oil passage between the auxiliary pilot valve and the governor rotation pilot valve is detected, and the change in pressure of the oil passage between the auxiliary pilot valve and the governor rotation pilot valve is detected. This is to determine whether the governor is operating. During the transition from daytime to nighttime during load limiter operation, when the pressure switch is turned on during control by the starting device drive motor, the synchronizer drive motor M opens it after a timer and turns off the pressure switch. When the starter opens further, the pressure switch turns ON again. The moment the pressure switch is turned on like this, the speed governor is controlled.
In other cases, load limiter operation is performed. or. The opening degree of the synchronizer is only slightly above the starting device (by the amount of timer), and at this time load shedding occurs, but since the governor operates with a slight delay compared to conventional systems, it is not possible to perform governor operation. They are almost the same and can prevent overspeeding.

(Example) An example of a steam turbine control device according to the present invention will be described with reference to FIG. It should be noted that the same parts as those in the conventional Figure 6 are given the same reference numerals and are explained in the prior art section 5 above, so the explanation of the overlapping parts will be omitted here. First, the lever system 21a to 2 of the control device of the steam control valve 4
1k is exactly the same as before. A pressure switch 2 is installed in the oil passage A between the auxiliary pilot valve 12 and the rotary pilot valve 28.
73 is provided, and when this switch 27 is turned ON (the IFF signal is turned on to the electric signal), the drying motor 14 of the synchronizer 1 is
It sends open/close signals to. A timer 1129 is provided in the 11t signal E and H.

This pressure switch 27 detects the pressure in the oil passage A, and
This is to determine whether it is Doriminotar operation or Governor operation. The relationship between the limiter operation and the hydraulic pressure of the oil passage A and the opening of the Gapana operation will be explained with reference to FIG. During load limiter operation B, the control of the hydraulic pressure at the end of the speed relay 17 is controlled by the auxiliary pilot well 12. At this time, the bow 1 of the valve 28 to the rotating pilot 1 is open. Therefore, the oil pressure Fa of oil passage A and the oil pressure Ga at the entrance of oil passage A are as follows: Speed 1 no 1
It is the same as the piston part oil pressure of 7.

On the other hand, during governor operation C, the piston lower hydraulic pressure of the speed relay 17 is controlled by the rotary pilot 11 valve 28. At this time, the port of auxiliary pilot valve l2 is open.
Therefore, the oil pressure of oil passage A is F. Therefore, the oil pressure D of the control oil 20 is the same as that of the control oil 20. The oil IEGb at the oil passage opening becomes the same as the piston lower oil pressure of the speed relay 17. In this way, the oil pressure of the oil passage A changes from F, l to FC. The intermediate position of Fb is set to the set pressure E of the pressure switch 27. By turning this pressure switch 27 ON or OFF, it is possible to determine whether load limiter operation or governor operation is being performed.

Next, during variable voltage operation, from daytime 118 to nighttime, night 1? [A method of shifting the opening degree of the steam control valve to daytime will be explained with reference to FIG. During the transition from daytime to nighttime, there is a transition from 4 to ■(, and during the transition, it is L. During this period, the opening of the steam control valve is gradually increased by the drive motor 16 to the opening Ia of the starter device, and from the end to K
Move to. During this time, the opening degree Ha of the synchronizer is opened up the stairs by the synchronizer drive motor l4.

This is the ON state of the pressure switch explained in Fig. 2 above.
When the pressure switch is turned off, it is possible to determine whether it is load limiter operation or governor operation, and when the pressure switch is turned on, it becomes governor operation, so only the signal Na from the timer is opened, so the opening Ha of the synchronizer is higher than the opening Ta of the starting device. Since the pressure switch is located at OFF, the pressure switch switches to L load limiter operation.
Shift from to K.

On the other hand, when transitioning from nighttime to daytime, there is a transition from K to J, and during the transition, it is M. During this time, the opening degree of the steam control valve changes from K to J by gradually closing the opening degree I0 of the starter device by the driving motor l6. During this time, the opening degree of the synchronizer is H. is closed in step 7 by the synchronous device sliding motor l4.

This is because when the pressure switch is turned on, the governor operation is started, so the signal in the closing direction of the synchronizer drive motor is stopped by the timer signal Nb. Then, the activation device 1d is heard. Since the is gradually closing, the pressure switch turns OFF L and switches to load limiter operation. This is repeated to shift the opening degree of the steam control valve from K to 61.

As mentioned above, the moment when the pressure switch is turned on, it is in governor operation, but the rest of the time it is in load limiter operation, and even during load limiter operation, the opening of the synchronizer is slightly smaller than the opening of the starter. Since it is located on the upper side, even if a load shedding occurs at this time, the governor only performs the JDJ operation with a slight delay compared to the conventional one, and overspeed can be sufficiently suppressed.9 [Effects of the Invention] As described above, the In the invention, the load limiter is operated from 4t to nighttime and during the transition from nighttime to daytime, and a pressure gas is provided between the auxiliary pilot valve and the rotary piston valve, and this pressure switch is turned on and off. By turning off, the opening of the same 1υj device is slightly less than the opening of the starting device ``t''.
It can be automatically positioned on the L side. Therefore, even if the load is cut off under these operating conditions, the turbine can be operated safely without overspeeding or tripping.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an example of a steam turbine control device according to the present invention, FIG. 2 is an explanatory diagram of the detected oil pressure of the pressure switch attached to FIG. 1, and FIG. Figure 4 is a system diagram showing the flow of steam in a conventional steam turbine, Figure 5 is a diagram showing the miscarriage characteristics of the steam control valve during daytime and nighttime variable pressure operation, and Figure 6 is a diagram showing the flow of steam in a conventional steam turbine. FIG. 2 is a system diagram of a turbine control device. l2...Auxiliary pilot valve 13...Synchronizer L4...Motor for driving the synchronizer 15...Starting device 16...Motor for driving the starting device l7...Speed relay] 8...Steam control Valve oil cylinder Pilot valve 19... Steam control valve oil cylinder 20... Control oil 2
]a~21k...Lever system 22a~22c...Torque shaft 27...Pressure switch 28...Rotary pilot valve 29...
Timer (8733) Representative Patent Attorney Yoshiaki Inomata (and other names) Figure 2 Figure 3 Figure 111L

Claims (1)

[Claims] In a control device for a steam turbine that requires variable pressure operation that changes the main steam pressure in response to the load of the steam turbine in a water desalination plant that uses exhaust steam from a steam turbine, and maintains a constant amount of exhaust steam, the variable pressure operation At times, the range of change in the opening of the steam control valve is controlled by a load limiter, and a pressure switch and a timer are installed in the oil passage between the auxiliary pilot valve and the governor rotation pilot valve, and the setting of this timer controls the opening of the synchronizer. 1. A control device for a steam turbine, characterized in that the opening angle is positioned slightly higher than the opening angle of a starter device.