JPH11343812A - Turbine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the rising maximum value of a turbine speed after shutdown of a load by automatically operating a governor setter to reduce, and lowering the turbine speed after fully closing an adjusting valve, when necessity of quick closing of an intercept valve is judged by the condition of reheat steam pressure, turbine speed, and opening of a generator cut-off machine. SOLUTION: Under the condition of low steam pressure at variable pressure operation, namely, under the condition in which an adjusting valve 3 is opened by a governor setter 23, when load shutdown is generated by system accident or the like, reheat steam pressure 17, the generator cut-off machine opening signal from a generator cut-off machine 60, and the turbine speed from a turbine speed detector 11 are input to a governor reduction operating circuit 50. If necessary, a command 51 forcedly reducingly operating a governor setter 23 is output to fully close the adjusting valve 3, thereafter deviation between a valve opening command and valve opening is detected by a monitor relay 32, and a valve quick close command is output to a valve quick close mechanism 16 to quickly close an intercept valve 7. Hereby the rising maximum value of turbine speed after load shutdown is restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generation plant that performs a variable pressure operation, and more particularly to a turbine control device suitable for suppressing a maximum rise in turbine speed after a load interruption due to a system failure or the like.

[0002]

2. Description of the Related Art In a turbine control device, FIG.
As shown in (a) and (b), the steam generated in the boiler 1 is guided to a main steam pipe 2, flows into a high-pressure turbine 4 via a control valve 3, and generates torque. This high pressure turbine 4
Is returned to the boiler 1 again, and is heated again by the reheater 5 to become reheated steam. Reheat steam is reheat steam pipe 6
And flows into the low-pressure turbine 8 via the intercept valve 7 to generate torque.

The generator 9 is driven by the torque generated by the high-pressure turbine 4 and the low-pressure turbine 8 to generate electric power. The steam discharged from the low-pressure turbine 8 is condensed in the condenser 10 and returned to the boiler again by the water supply pump 19.

The speed / load control of the turbine / generator is performed by adjusting the control valve 3 and the intercept valve 7 by the turbine controller 200. Note that 11
Indicates a speed detector.

Next, an outline of speed / load control of the turbine control device 200 will be described. A rated turbine speed is set in the signal generator 20, a deviation from the actual turbine speed detected by the speed detector 11 is obtained by a subtractor 21, multiplied by a regulation rate 22, and a governor setting device 23 is set. The values are added by an adder 24, and are passed through an adjustable valve opening characteristic 25 as shown in FIG. 5B and output to an adjustable valve control circuit 26 as an adjustable valve opening command. The control valve 26 feeds back the actual opening from the opening detector 12 and outputs a valve drive signal to the valve drive unit 13.

On the other hand, the signal passing through the adder 24 is multiplied by an intercept valve adjustment rate 27, and the intercept valve fully open bias from a signal generator 28 is added by an adder 29, and as shown in FIG. It is output to the intercept valve control unit 31 as an intercept valve opening command through the opening characteristic 30. The intercept valve control section 31 outputs a valve drive signal to the valve drive section 15 using the actual opening from the opening detector 14 as feedback. During normal operation, since the turbine speed is the rated speed, the speed deviation calculated by the subtractor 21 is "0", the output of the adder 24 becomes equal to the set value of the governor setting device 23, and the opening / closing valve opening characteristic 25 The governor setting device 23 determines the control valve opening degree command which is the output of.

In such a configuration, in the constant pressure operation plant, the generated steam pressure of the boiler is kept constant, so that the generated power is adjusted by the governor setter 23. When the turbine speed increases, the speed deviation of the subtractor 21 becomes negative, and the value obtained by multiplying the negative value by the control valve adjustment rate 22 becomes negative. Therefore, the value obtained by adding the governor setting device 23 by the adder 24 becomes the turbine speed increase. It decreases with it. As a result, the output of the control valve opening degree characteristic 25 decreases, and the control valve 3 is eventually fully closed.

On the other hand, in the intercept valve opening command, since the fully open bias from the signal generator 28 is added by the adder 29, the output of the adder 24 becomes "0" and the control valve 3
Until is fully closed, the intercept valve opening command is equal to or greater than full open, and the intercept valve 7 is fully opened. When the turbine speed further rises, the control valve 3 is fully closed, and the output of the adder 24 becomes negative, the output of the adder 29 becomes a value equal to or less than the fully open state, and the closing control of the intercept valve 7 starts.

At this time, if a deviation between the intercept valve opening command and the actual valve opening is detected by the monitor relay 32,
An intercept valve rapid closing signal is output to the valve rapid closing device 16,
The intercept valve 7 is forcibly fully closed to suppress an increase in turbine speed. Generally, the intercept valve quick closing is used as a turbine overspeed prevention means at the time of load interruption when the turbine load is 10% or more.

[0010]

In recent years, a variable pressure operation in which the degree of opening and closing of a control valve is maintained and the generated power is adjusted by adjusting the steam pressure in order to improve the power generation efficiency and to shorten the start-up time from the stop of the plant to the rated operation has been the mainstream. It is becoming. In this variable pressure operation, the governor setter is set near the upper limit to reduce steam loss at the control valve, and the control is performed with the control valve close to full open. In the event of a load shedding, the variable valve operation plant has a larger opening degree of the regulator valve than the conventional constant pressure plant, so the intercept valve is closed after the regulator valve is fully closed due to the increase in turbine speed, and the intercept valve is rapidly closed. Since the turbine speed during operation increases, the maximum value of the turbine speed increase due to load shedding increases, and the time until the turbine speed stabilizes at the rated speed and rejoins increases,
In some cases, an increase in turbine speed may lead to serious accidents such as turbine damage, which has been a problem.

As an overspeed protection method, an acceleration relay system in which the turbine acceleration is equal to or more than a specified value and the ICV is rapidly closed is adopted instead of the ICV suddenly closed due to the ICV opening deviation. Although it is possible to close quickly,
Turbine speed rise at the time of system failure including load interruption such as system fluctuation is irregular, and it may be technically difficult to quantitatively grasp turbine acceleration as overspeed protection.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problem, a turbine control device according to the present invention is uniquely designed based on the turbine speed at the time of load shedding and the energy flowing into the turbine when the speed rises at the time of load shedding. Since the energy flowing into the turbine is almost proportional to the reheat steam pressure, it is determined whether or not the intercept valve needs to be rapidly closed based on the reheat steam pressure, the turbine speed, and the condition of opening the generator breaker. If necessary, automatically reduce the governor setting device to reduce the turbine speed during the intercept valve sudden closing operation after the control valve is fully closed, thereby suppressing the maximum value of the turbine speed increase after load interruption. It has such means.

That is, according to the present invention, the governor setter is automatically corrected on the basis of the conditions of the reheat steam pressure and the turbine speed when the load is cut off due to a system accident or the like of the variable pressure operation plant,
There is an operation of operating the intercept valve sudden closing so that the maximum rise value of the turbine speed after the load is cut off does not exceed the allowable value.

[0014]

1 to 4 show an embodiment of the present invention.
This will be described with reference to FIG.

[0015]

[Equation 1] Adjustable valve opening command = (Rated speed (%)-Actual speed (%)) x Adjustable valve adjustment rate + Governor setting (%) ... (1)

[0016]

## EQU2 ## Intercept valve opening command = control valve opening command (%) × intercept valve adjustment rate + full opening bias (100%) (2) FIG. 3 shows the relationship between the control valve, the intercept valve and the turbine speed. The relationship between the turbine speed and the valve opening / closing command is expressed by equation (1). When the turbine speed rises, the value obtained by subtracting the value obtained by multiplying the speed deviation by the valve regulation rate from the governor setting device is subtracted from the graph. As shown by a curve 40, the value decreases as the speed deviation increases. The intercept P of the Y axis is equal to the governor setting at this time.

Further, the intercept valve is represented by equation (2), and is a value obtained by multiplying the value of equation (1) by the intercept valve adjustment rate and adding 100% as a fully open bias, as shown by a curve 41 on the graph. In this way, the closing control of the intercept valve at the time of turbine speed increase is started after the control valve is fully closed. Further, in the normal operation state, since the turbine speed deviation is “0”, the opening of the control valve at this time is determined by the set value P of the governor setter.

Next, FIG. 4 shows the relationship between the generated power, the governor setting, and the steam pressure from a no-load operation to a rated load operation of a general variable-pressure operation plant. In FIG. 4, the steam pressure is kept constant from 0% to 30% of the no-load power, and the generated power is adjusted by controlling the opening of the regulator valve. However, the generated power is lower than the rated pressure. In order to obtain the desired value, it is necessary to increase the opening and closing of the control valve, and the governor setting device is increased to the point a, and then from 30% to 90%
Up to the load, the governor setting is kept constant, and the generated power is adjusted by increasing the steam pressure. At 90% load, the start of the boiler is completed, and the steam is in a plant rated state. From 90% to the rated load operation, the power generation is increased to the rated load by keeping the boiler constant in the rated state and increasing the governor setting.

In this manner, by simultaneously starting the boiler while generating power, the start-up time of the plant can be reduced. In such a variable pressure operation, the governor setting is large when the steam pressure is low, the load is cut off due to a system accident, etc., the intercept valve closes, and the turbine speed when the intercept valve suddenly closes is operated. And the maximum rise speed of the turbine speed after load shedding becomes high, which has been a problem. Incidentally, the characteristics of the generated power-governor setting / steam pressure in the variable pressure operation are determined by the characteristics of the main body of the boiler / turbine or the like.

According to the present invention, when a load interruption occurs due to a system accident or the like in a state where the steam pressure during the above-mentioned variable pressure operation is low, it is determined from the generated power and the turbine speed whether or not the generated load requires the intercept valve to be rapidly closed. When necessary, the governor setter is automatically deactivated to activate the intercept valve suddenly and to suppress the increase in turbine maximum speed after the load is cut off.

FIG. 1 shows an embodiment of the present invention.

As shown in FIG. 1, a speed deviation between the turbine speed detector 11 and the rated speed setting device 20 is subtracted by a subtractor 21.
And the adder 24 multiplies the governor setting rate 22 and adds the governor setting of the governor setter 23. Thereafter, the control signal is output to the control valve control circuit 26 as a control valve opening command through the control valve characteristic 25. The control valve control circuit 26 feeds back the actual opening from the opening detector 12 and outputs a valve drive signal to the valve drive unit 13 to control the control valve opening.

On the other hand, the signal to which the governor setting value has been added by the adder 24 is multiplied by the intercept valve adjustment rate 27 and the intercept valve fully open bias 28 is added by the adder 29. It is output to the valve control circuit 32 as an opening command.
The valve control circuit 32 feeds back the actual opening from the opening detector 14 and outputs a valve drive signal to the valve drive unit 15 to control the intercept valve opening.

In this configuration, when the steam pressure during the variable pressure operation is low, that is, when the regulator valve is opened by the governor setter 23, and a load interruption occurs due to a system accident or the like, the reheat steam pressure 17 and The generator breaker opening signal from the generator breaker 60 and the turbine speed from the turbine speed detector 11 are input to the governor reduction operation circuit 50, and when the intercept valve needs to be rapidly closed, the governor setter 23 is forced. A command 51 to perform the reduction operation is output to the governor setting device 23, and the control valve 3 is fully closed by the control of the control of the control valve by the governor setting reduction and the speed increase, and then the intercept valve closing control is started, and the intercept valve opening command The monitor relay 32 detects the deviation of the valve opening and the valve opening degree, and outputs an intercept valve rapid closing command to the intercept valve rapid closing mechanism 16 to rapidly close the intercept valve. .

As a result, the maximum increase value of the turbine speed after the load is cut off is suppressed by lowering the turbine speed at the time of the intercept valve sudden closing operation. FIGS. 2A and 2B show the circuit of the governor reduction operation circuit 50. An example is shown below. 2 (a) and 2 (b), the reheat steam pressure detection signal 56 indicates the turbine load 10
The monitor relay 53 detects that the pressure has reached a pressure of several percent or more, detects that the turbine speed 55 has risen and has exceeded a specified value by the monitor relay 52, and generates a load shedding and a circuit breaker open signal 57. Is input from the generator circuit breaker 60, the turbine load is 10% or more, the turbine speed is equal to or more than the specified value, and the logical product of the circuit breaker open detection signal is calculated by the logical product calculator 54. 51 is output to the governor setting device 23, and the governor setting device 23 is depressed as indicated by 56. As a result, the opening / closing degree of the control valve is closed as indicated by 58, the intercept valve is also closed as indicated by 59, and the intercept valve is rapidly closed.

[0026]

According to the turbine control device of the present invention, even if a load interruption occurs in a plant performing a variable pressure operation,
When the load is interrupted in the load zone where the intercept valve suddenly needs to be closed, the turbine speed during the intercept valve suddenly closes can be suppressed, and as a result, the maximum speed increase of the turbine can be suppressed.

[Brief description of the drawings]

FIG. 1 is a system diagram of a turbine control device shown as an embodiment of the present invention.

FIGS. 2A and 2B are a circuit diagram of a governor reduction operation circuit and characteristic diagrams of various devices at the time of load interruption.

FIG. 3 is an opening characteristic diagram of the control valve used in the turbine control device according to the embodiment of the present invention.

FIG. 4 is a load characteristic diagram during a variable pressure operation according to the present invention.

FIGS. 5A and 5B are a system diagram and a characteristic diagram of a control valve opening degree of a conventional turbine control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Boiler, 2 ... Main steam pipe, 3 ... Control valve, 4 ... High pressure turbine, 5 ... Reheater, 6 ... Reheat steam pipe, 7 ... Intercept valve, 8 ... Low pressure turbine, 9 ... Generator, 10 ... Condenser,
11 ... speed detector, 12, 14 ... opening detector, 13, 1
5: valve drive unit, 16: intercept valve quick closing mechanism, 17
... Reheat steam pressure detector, 19 ... Feed water pump, 20 ... Signal generator, 21 ... Subtractor, 22 ... Adjustable valve setting rate, 23 ... Governor setter, 24,29 ... Adder, 25 ... Adjustable valve opening Characteristics: 26: control valve control circuit, 27: intercept valve adjustment rate, 28: signal generator, 30: intercept valve opening degree characteristic, 31: intercept valve control circuit, 32, 52,
53 ... monitor relay, 40 ... open / close valve opening-speed deviation characteristic, 41 ... intercept valve opening-speed deviation characteristic, 50
... governor setting decrease operation circuit, 51 ... governor setting compulsory decrease operation signal, 54 ... AND operator, 60 ... generator breaker, equation (1) ... opening / closing valve opening-speed deviation characteristic, equation (2) ... intercept Valve opening-speed deviation characteristics.

Claims (2)

[Claims] 1. Steam from a boiler flows into a high-pressure turbine through a regulator valve, further flows into a low-pressure turbine via a reheater and an intercept valve, and regulates steam pressure while maintaining the regulator valve opening. The governor setter of the variable-voltage operation plant that regulates the generated power, the opening command during the intercept valve closing control, and the intercept valve that forcibly fully closes the intercept valve when the deviation of the valve opening exceeds the allowable value. In a turbine control device with a rapid closing function, when load interruption occurs due to a system accident or the like during variable pressure operation, the governor setter is automatically corrected based on the reheat steam pressure and turbine speed, and intercept valve closing control is performed by intercept valve closing control. A turbine control device characterized by suppressing a maximum speed increase of a turbine after an ICV sudden closing operation by performing a closing operation in advance. 2. The turbine control device according to claim 1, wherein the automatic correction of the governor setting device is performed on condition that a turbine output, a turbine speed and a circuit breaker opening at the time of load interruption are conditions.