JPH05312995A - Steam turbine controller - Google Patents

Abstract

PURPOSE:To enable continuing stable operation of a turbine without lowering below the rated revolution number by detecting the drop of load due to system accident, controlling it, and omitting a power load balance detection circuit after a certain time limit. CONSTITUTION:During the drop of load due to a system accident, turbine revolution number increases and a power to load umbalance detection circuit 22 detects the power to load umbalance because of large load change rate and large deviation of power to load, takes self-maintaining with a wipeout 39, and starts time counting with a timer 38. After quick shut of a control valve and quick opening motion of a bypass valve, it releases the self-maintaining. Then, a control valve flow-rate demand signal 33 and a bypass valve flow-rate demand signal 7 are requested from a total steam flow-rate signal 5 and a speed/load control signal 18 and by controlling the steam control valve and the bypass valve, the number of revolutions of the turbine is set near the rated number of revolutions. Thus, such an event only the bypass valve is closed without opening the steam control valve which causes lowering of turbine revolution number below the rated number, is avoided and so, stable operation becomes possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine control device for a boiling water nuclear power plant, and more particularly to a turbine control device for continuing the operation without scramming when the turbine speed fluctuates due to the disturbance of the power system. It relates to an optimum steam turbine control device.

[0002]

2. Description of the Related Art An example of a turbine steam system in a nuclear power plant is shown in FIG. The steam generated in the reactor 41 flows into a turbine 44 through a main steam stop valve (hereinafter referred to as MSV) 42 and a steam control valve (hereinafter referred to as CV) 43, and is then condensed in a condenser.
Condensed at 45. Further, a part of the steam passes from the front of the MSV 42 through a turbine bypass valve (hereinafter referred to as BPV) 46 to bypass the turbine 44 and flow into the condenser 45. Always MS
V42 is fully opened and the valve opening of CV43 and BPV46 is adjusted to control the turbine speed and turbine inlet steam pressure. An example of a conventional turbine control system is shown in FIG.

In FIG. 3, a deviation signal between a pressure signal 1 measured by a pressure detector installed in a reactor or a main steam pipe and a preset pressure set value 2 passes through a filter circuit 3 and a pressure control circuit. Input to 4. The pressure control circuit 4 uses the deviation signal to output the total main steam flow rate signal (hereinafter I
PR signal) 5 is created.

On the other hand, the deviation signal between the turbine speed signal 8 measured by the turbine speed detector and the turbine speed set value 9 is input to the speed control circuit 10 and becomes the turbine speed control signal 11 there. The speed control signal 11 is further added with a load set value 12 which is an output signal of the load setter 13, and
It becomes the load control signal 18. These, IPR signal 5 and speed /
The load control signal 18 is input to the low value priority circuit 20. As a result of the low value priority selection, the lower signal of the two becomes the regulating valve flow rate signal 33, and the regulating valve opening degree is controlled.

A signal from the power load unbalance circuit 22 is also input to the load setting device 13, and the power load unbalance circuit 22 takes in the intermediate steam pressure signal 23 and the generator current signal.

In contrast to the control valve controlled by the above system, the turbine bypass valve requests the bypass valve flow rate by subtracting the control valve flow rate request signal 33 from the IPR signal 5 and the bypass valve chattering prevention bias signal 6 during normal operation. The opening degree is controlled by the signal 7.

In a boiling water nuclear power plant, the reactor output is adjusted by the amount of voids in the core, so the neutron flux sensitively reflects changes in pressure. Therefore, during normal operation, the IPR signal 5 based on the pressure signal 1 controls the control valve with priority, and the load setting value 12 is set to the IPR signal 5 so that the control valve does not operate in response to a relatively small fluctuation in turbine speed. Of 10
It is set about% higher. The speed control signal 11 is within -10% (generally, the speed adjustment rate is 100% control signal / 5% speed change, which corresponds to 0.25 Hz at 50 Hz). Does not respond and pressure control is prioritized. On the other hand, for a turbine speed increase (that is, a frequency increase of 0.25 Hz or more) such that the speed / load control signal 18 decreases to 10% or more, the speed / load control signal 18 becomes the IPR signal 5 or less and the control valve Is narrowed down. The excess steam resulting from the throttle operation of the steam control valve is processed by opening the bypass valve with a signal obtained by subtracting the control valve flow rate request signal 33 and the bias value 6 from the IPR signal 5, that is, the bypass valve flow rate request signal 7. To be done. In this way, when the regulator valve and the bypass valve are operated in a coordinated manner, the reactor pressure remains almost unchanged and the plant operation can be continued. Power load unbalance circuit in power transmission system
Explain the nuclear power plant response in the event of a malfunction that activates 22.

When an accident such as a lightning strike occurs in the power transmission system, the power transmission system breaker operates and the load is lost. If the missing load is relatively large, the power load unbalance detection circuit 22 operates. When the power load imbalance detection circuit 22 operates, the regulator valve rapid opening circuit 37 operates,
The load setting device 13 is set back and the load setting value 12 becomes 0% as the control valve is suddenly opened. When the load setting value becomes 0%, the speed / load control signal 18 becomes 0% or less, and the low value priority selection circuit 20 compares it with the IPR signal 5,
18 is selected, and the regulator valve flow rate request signal 33 becomes 0%. On the other hand, when the increase / decrease valve flow rate request signal 33 becomes 0%, the value obtained by subtracting the closing bias 6 from the IPR signal 5 becomes the bypass valve flow rate request signal 7, so the bypass valve control circuit 34 saturates and the saturation is detected. The bypass valve rapid opening circuit 35 operates to rapidly open the bypass valve. At this time, at the nuclear power plant where the bypass valve capacity is less than the reactor rated flow rate, the reactor shuts down due to the sudden closing of the control valve.

However, in a nuclear power plant where the bypass valve capacity is 100% or more of the reactor rated flow rate (hereinafter 100% bypass plant), the reactor output decreases as the control valve suddenly closes and the bypass valve suddenly opens, and the bypass valve At this point, the reactor pressure is controlled, and finally the operation shifts to in-house isolated operation.

[0010]

The operation of the power load unbalance circuit 22 will be described with reference to FIG. Converts the generator current into a load signal and detects a large rate of change. On the other hand, the intermediate steam pressure is converted into an output signal, and the deviation between the output signal and the load signal is calculated to detect a large deviation. The power load unbalance operates with a large load change rate and a large output-load deviation. On the other hand, this condition is self-maintained, and the self-maintenance is released when the large output-load deviation is restored. However, since it takes time until the intermediate steam pressure detecting the output signal falls below the large output-load deviation setting, the self-holding continues to operate more than necessary.

[0011] Here, when a load cutoff in which the power load unbalance detection circuit operates in the 100% bypass plant occurs, the turbine speed is increased during the operation of the power load unbalance detection circuit during the process of shifting to the independent operation in the plant. When the speed is lower than the rated speed, the control valve flow rate request signal 33 increases, but the power load unbalance circuit 22 operates to operate the control valve rapid closing circuit 37, so the steam control valve does not actually open, On the contrary, since the bypass valve flow rate request signal 34 decreases and only the bypass valve is closed, the nuclear pressure rises, and as a result, the neutron flux may exceed the specified value and the reactor may shut down.

According to the present invention, the power load unbalance detection circuit operates due to load cutoff so that the turbine speed does not become lower than the rated speed when the power load unbalance detection circuit operates due to a system fault, and the steam control valve is closed soon afterwards. Another object of the present invention is to provide a turbine control device having a function of canceling a power load unbalance detection circuit.

[0013]

A steam turbine control apparatus of the present invention detects a load drop by a power load imbalance detection circuit in order to prevent turbine overspeed at the time of load drop due to a system accident, and a steam control valve sudden The turbine control device having a function of closing and suddenly opening the bypass valve is provided with a function of excluding the power load unbalance detection circuit at a time limit after the steam control valve is rapidly closed.

[0014]

[Operation] As a result, the power load unbalance circuit operates when the load is dropped due to a system accident, and after a rapid closing of the steam control valve and sudden opening of the bypass valve, a stable plant without falling below the turbine rated speed during the turbine deceleration process You can continue driving.

[0015]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, the same elements as those in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. The power load imbalance detection circuit 22 detects a power load imbalance with a large load change rate and a large output-load deviation, and the wipeout 39 holds itself and the timer 38 starts counting up. Exclude self-holding.

When the load is dropped due to a system accident, the power load imbalance detection circuit 22
Is activated, and after the regulator valve is closed and bypass valve is opened rapidly,
The self-holding of the power load unbalance is released, and thereafter, the steam control valve / bypass valve is controlled by the control valve flow rate request signal 33 and the bypass valve flow rate request signal 7 obtained from the IPR signal 5 and the speed / load control signal 18. As a result, the turbine speed will settle near the rated speed.

According to the embodiment, when the load is cut off, the power load imbalance detection circuit operates and the turbine speed becomes equal to or lower than the rated speed during the settling process after the steam control valve / bypass valve is closed and opened rapidly. There is no event that the valve does not open and only the bypass valve closes.

In the present invention, the timer starts to operate by the operation of the power load imbalance detection circuit. However, in order to ensure that the timer is operated more reliably, the steam load control valve is activated by the operation of the power load imbalance detection circuit. It is also possible to exclude the power load unbalance detection circuit with a time limit by detecting that the power load imbalance has been closed.

[0019]

As described above, according to the present invention, when the turbine speed is increased and the power load unbalance circuit operates when the load is dropped due to a system accident, after the control valve is suddenly opened and the bypass valve is rapidly closed, During the turbine deceleration process, stable plant operation will be continued without lowering the turbine rated speed or lower.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a steam turbine control device of the present invention.

FIG. 2 is a system diagram showing a steam turbine system.

FIG. 3 is a block diagram showing an example of a conventional steam turbine control device.

[Explanation of symbols]

 1 pressure signal 2 pressure set value 3 filter circuit 4 pressure control signal 5 all main steam flow rate signal 6 fully closed bypass 7 bypass valve flow rate request signal 8 speed signal 9 speed set value 10 speed control circuit 11 speed control signal 12 load set value 13 Load setter 18 Speed / load control signal 20 Low value priority selection circuit 22 Power load imbalance detection circuit 23 Intermediate steam pressure signal 33 Adjusting valve flow rate request signal 34 Bypass valve control circuit 35 Bypass valve quick closing circuit 36 Adjusting valve control circuit 37 Control valve rapid closing circuit 38 Operation delay timer 39 Wipe out 41 Reactor 42 Main steam stop valve 43 Steam control valve 44 Turbine 45 Condenser 46 Turbine bypass valve 47 Pressure detector

Claims (1)

[Claims] 1. A function of controlling a reactor pressure, a turbine speed and a generator load of a boiling water nuclear power plant, and a sudden decrease of the generator load in order to prevent an abnormal increase of the turbine speed when a load cutoff occurs. In the steam turbine control device having a function of rapidly closing the steam control valve by the operation of the power load unbalance circuit for detecting, a means for measuring the time when the power load unbalance detection circuit starts operating after the power load unbalance operation. And a means for forcibly excluding the power load unbalance detection circuit after a lapse of time after the steam control valve is closed abruptly.