JPS6241504A - Feed water control system for steam turbine plant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a water supply 91 control device for a steam turbine plant such as a nuclear power plant, and is particularly used to stabilize the water level of a nuclear reactor, etc. during startup and shutdown of the reactor. The present invention relates to a water supply control device for a steam turbine plant that can control the water supply to a steam turbine plant.

[Technical background of the invention and its problems] Generally, in a steam turbine plant such as a nuclear power plant, the water level of the reactor or boiler, the water supply flow to the reactor, etc., and the main steam flow rate from the reactor, etc. The water supply flow rate is controlled by adjusting the rotational speed of the water supply pump or the opening degree of the water supply flow rate control valve so that the water level in the reactor etc. remains constant. On the other hand, in order to prevent the water pump from heating up when it is operated in a low flow range, a recirculation system is installed that returns a certain amount of flow from the water pump's discharge line to the suction side of the water booster pump. Also, efforts are being made to avoid circulating the minimum amount of cooling water necessary for safe operation of the water supply pump.

FIG. 3 is a schematic system diagram of the conventional water supply control m+ device, in which condensate condensed in a condenser connected to the turbine 1 is pressure-increased by a condensate pump 3, and is passed through the water supply pump suction line. The water is fed to the feed water pump section 5 through the water supply pump section 4, and after being pressurized by the water feed pump section 5, it is supplied to the nuclear reactor 6.

The water pump unit 5 includes a plurality of water pumps 7a, 7b, 7c connected in parallel to each other, and each of the water pumps 7a, 7.
The water supply pump bypass valve 9 is further connected in parallel to the parallel circuit of the water supply pump and the water supply flow rate adjustment valve. has been done. Further, the downstream side of each of the water supply pumps 7a, 7b, 7c and the condenser 2 are connected by water supply recirculation pipes 11a, 11b, Ilc having minimum flow valves 10a, 10b, 10c, respectively. Minimum f[1-valve 10a, 10b,
10c is each water supply pump 7a.

Opening/closing is controlled by flow rate signals detected by water supply flow rate detection switches 12a, 12b, 12c provided on the discharge port sides of YA 7, b, 7c. That is, when the discharge flow rate from the water supply pumps 7a, 7b, 7c becomes less than a predetermined value, the water supply flow rate detection switches 12a, 12b, 1
2c is activated and the minimum flow valves 10a, 10b, 10
c opens, and when the flow m increases, the water supply flow rate detection switches 12a, 12b, 12c return to their original states, and the minimum 70-valve 10a, 10b, 10c closes, respectively.

Incidentally, a feed water stream detector 14 and a main steam flow drunken detector 15 are provided at the water supply inlet to the reactor 6 and the main steam pipe 13 that feeds main steam from the reactor 6 to the turbine 1, respectively. , the flow rate signals detected by the rain detectors 14 and 15 are input to the water supply control calculator 16. In addition, the water level signal from the reactor water level detector 17 is also added to the water supply control calculator 16, and the water supply flow rate required to maintain the reactor water level above the specified level is calculated based on each flow rate signal and the water level signal. , the opening degree of each of the water supply flow m regulating valves 8a, 8b, 8c and the water supply pump bypass valve 9 is controlled by the output signal.

FIG. 4 is an explanatory diagram of the configuration of the feed water flow rate control section as described above, in which the main steam flow rate detector 1 is connected to the feed water control calculator 16.
5 and the feedwater flow rate detector 14, the difference between the main steam flow m and the feedwater flow rate is determined, and the required feedwater flow rate is determined based on the difference between the reactor water level and the reference water level according to the signal from the reactor water level detector 17. is calculated, and the output signal is transmitted to the water supply flow rate control valves 8a, 8b, 8c and the water supply pump bypass valve 9 via automatic/manual controllers 18a, 18b, 18c, and 18d, and their opening degrees are adjusted.

The automatic/manual controllers 18a, 18b, 18c.

When 18d is in the "auto" position, the water supply flow m control valve, etc. is controlled by the output signal from the water supply control calculator 16, and when it is in the "manual" position, the automatic/manual controller is controlled. 18a, 18b.

The opening degrees of the water supply flow m control valve and the water supply pump bypass valve are adjusted according to the positions of the adjustment knobs provided at 18G and 18d.

FIG. 5 is a characteristic explanatory diagram of the above-mentioned apparatus during plant shutdown operation, where the horizontal axis shows time and the vertical axis shows reactor water level, feed water pump flow rate, and minimum flow valve opening degree. By the way, three water supply pumps are generally installed, each having a capacity of about 50% of the rated water supply flow rate. Now, when the two feed water pumps 7a and 7b are operating and the reactor output drops to 40%, the automatic fjJ/manual control mt controller 18b is switched to the "manual" position, and the automatic/manual control is switched to the "manual" position. The adjustment knob of the automatic/manual controller 18b is adjusted while the m device 18a is in the "auto" position, and the opening degree of the water supply flow mawJ valve 8b is gradually reduced. Therefore, when the pump flow rate Q of the water supply pump 7b decreases and reaches the operating point A of the water supply flow rate detection switch 12b, the minimum flow valve 10b is operated and fully opened. However, when the minimum flow valve 10b is fully opened in this way, the water supply flow rate suddenly decreases, and the water supply control 2I
The water supply increase operation is performed by the operation of the l-operator 16.

In this way, when the reactor water level T1 gradually settles down while taking pictures and reaches its specified value, the pump flow rate continues to decrease.

Furthermore, when the reactor is started up, the operating state is reversed to that described above.

In this way, when the feed water flow rate is increased or decreased during reactor startup or shutdown, the minimum flow valve of the water pump closes,
When the reactor opens, the water supply flow rate changes suddenly, and the reactor water level changes rapidly in response to this change, causing problems such as the inability to operate the reactor stably. Therefore, it has been proposed to adopt a minimum flow valve that can continuously control the recirculation flow rate, but in this case, the opening degree of the minimum flow valve changes according to changes in the water supply flow m, so When operating for a long time, there are problems such as negative effects on the minimum flow valve.

(Objective of the Invention) In view of these points, the present invention is designed to maintain the water level in a nuclear reactor or boiler even when the minimum flow valve of a feed water pump opens or closes during startup or shutdown of a steam turbine plant such as a nuclear couplant. The purpose of the present invention is to provide a water supply control device that can maintain stable operation of a plant by keeping it constant.

(Summary of the Invention) The present invention includes a first function generator that generates a bias signal in the direction of increasing the water supply flow rate when the minimum flow valve of a water supply pump is opened, and a bias signal that generates a bias signal in the direction of decreasing the water supply flow rate when the minimum flow valve is opened. a second function generator that generates a bias signal, an adder that adds the output j signals of both of the function generators to the water supply flow control signal, and a control that controls the water supply flow rate using the output signal from this adder. It is characterized by having a ``m device''.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3.

In FIG. 1, output signals from the feedwater flow rate detector 14, the main steam flow rate detector 15, and the reactor water level detector 17 are inputted to the feedwater control calculator 16, and the output signals from the feedwater flow rate detector 14, the main steam flow rate detector 15, and the reactor water level detector 17 are inputted to the feedwater control calculator 16, and the output signals are inputted to the feedwater control calculator 16. The required water supply flow rate is calculated from the difference between the reactor water level and the reference water level, and this output signal is sent to the adder 20a,
20b.

It is input to 20c and 20d.

Each of the adders 20a, 20b, 20c, and 20d has a first
The output signal of the function generator 21 and the second function generator 2
2 output signals are also input, and each adder 20a,
The output signals of 20b, 20c, and 20d are automatically/
Manual controller 18a.

Water supply control valve 8a via 18b, 18c, 18d,
8b, 8c and the water pump bypass valve 9;
The opening degree of the multi-valve is controlled. Each of the above adders 20a, 20b
, 20c, 20d are contacts 2 of the first relay (not shown)
When the contact 3a of the second relay is closed, the output signal of the first function generator 21 is input, and when the contact 24a of the second relay is closed, the output signal of the second function generator 22 is input.

Thus, each adder 20a, 20b, 20c.

20d calculates the sum of the output signal of the water supply control calculator 16 and the output signal of the first function generator 21 or the second function generator 22, and outputs the corresponding automatic/manual controllers 18a and 18b, respectively. , 18c.

18d.

By the way, when two or more water supply pumps are in operation, the first relay operates when any one of the minimum flow valves corresponding to the water supply pumps in operation opens, and closes the contact 23a. The second relay is configured to operate when only one water pump is in operation and the minimum flow valve of the next water pump closes, closing its contact 24a.

On the other hand, the first function generator 21 generates a positive signal corresponding to the opening speed and capacity of the minimum flow valve, which is operated in the opening direction from the time the contact 23a closes, and corresponds to the capacity value of the minimum flow valve. The second function generator 22 has a characteristic of gradually reducing the magnitude of the signal to zero when the value reaches a value of It has a characteristic that when a negative signal corresponding to the speed and capacity reaches a value corresponding to the capacity value of the minimum flow valve, the magnitude of the signal gradually returns to zero.

For example, when the feedwater pump 7a and the feedwater pump 7b are in operation and the feedwater flow m is to be throttled due to a reduction in reactor output, the opening of the feedwater flow rate control valve 8b is controlled via the self-vj/manual controller 18b. The water supply flow rate of the water supply pump 7b is reduced by controlling the water supply pump 7b, and when the water supply flow rate reaches the operating point of the water supply flow m detection switch 12b, the water supply flow rate detection switch 12b is closed and the minimum 70-valve 10b of the water supply pump is opened. Start (see Figure 2).

Therefore, the flow rate of the feed water flowing from the feed water pump 7b to the reactor side decreases inversely to the opening degree of the minimum flow valve 10b. On the other hand, since the output signal from the function generator 21 is input to the adder 20a at this time, the water supply flow rate of the water supply pump 7a gradually increases according to the output signal of the first function generator 21, and the minimum flow valve When 10b is fully opened, the output signal of the first function generator 21 is also held at a constant value for a certain period of time. Therefore, the flow rate of water supplied to the reactor is maintained substantially constant during the opening operation of the minimum flow valve 10b, and the reactor water level is maintained constant.

When a certain period of time elapses after the minimum flow valve 10b is fully opened, the output signal of the first function generator 21 gradually decreases and returns to the zero value, so that the water supply flow rate of the water supply pump 7a decreases.

Therefore, when the output signal of the first function generator 21 becomes zero, the water supply flow rate of the water supply pump 7a is thereafter controlled by the output signal of the water supply control calculator 16, and the flow rate is gradually reduced. During this period, the reactor water level will fluctuate slightly, but the range of fluctuation is extremely small and will not cause any adverse effects.

Furthermore, when the reactor power increases, the output signal of the second function generator 22 temporarily decreases the water supply flow rate of the other water supply pumps in response to the opening operation of the minimum 70 valve. - The feed water flow m to the reactor before and after the valve opening operation is maintained constant.

In this way, the flow rate of the feed water pump is adjusted in response to the closing or opening operation of the minimum flow valve, so the reactor water level is kept constant and the reactor can be operated stably.

In the above embodiments, a water supply system for a nuclear reactor has been described, but the present invention can also be applied to a water supply system for a boiler in an ordinary steam turbine plant. Furthermore, the present invention can also be applied to a system in which the water supply flow rate is adjusted not by adjusting the opening of the pump discharge valve but by adjusting the number of revolutions or speed of the pump.

Furthermore, if there is only one water supply pump, this can be handled by adjusting the opening degree of the water supply pump bypass valve in the same way.

〔Effect of the invention〕

Since the present invention is configured as described above, a bias signal is applied to the water supply flow rate control signal from the first function generator or the second function generator in response to the opening and closing of the minimum flow valve,
The total water supply flow rate to the reactor etc. is controlled to be constant regardless of whether the minimum flow valve is opened or closed. Therefore, the water level of the reactor, boiler, etc. can be maintained constant even during start-up and stop operations of Plan I, and stable operation of the plant can be achieved. Moreover, since only a function generator and an adder are added to the conventional device, the increase in cost can be kept low.

[Brief explanation of the drawing]

Fig. 1 is a schematic system diagram showing one embodiment of the water supply control device of the present invention, Fig. 2 is a diagram explaining the operation of the device of the present invention, Fig. 3 is a system diagram of a general water supply device, and Fig. 4 is a system diagram showing an embodiment of the water supply control device of the present invention. A schematic system diagram of a conventional water supply control device, and FIG. 5 is a water supply flow rate characteristic diagram in the conventional device. 7a, 7b, 7cm...Water pump, Qa, 8b. 8C... Water supply flow control valve, 10a, 10b, 10c.
...Minimum flow valve, 16...Water supply control operator, 2
0a, 20b, 20c, 20d...adder, 21...
- First function generator, 22... second function generator. Applicant's agent Sato - Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A first function generator that generates a bias signal in the direction of increasing the water supply flow rate when the minimum flow valve of the water supply pump is opened, and a bias signal in the direction of decreasing the water supply flow rate when the minimum flow valve is closed. It has a second function generator that generates a signal, an adder that adds the output signals of both of the function generators to the water supply flow rate control signal, and a controller that controls the water supply flow rate based on the output signal from the adder. A water supply control device for a steam turbine plant, characterized in that: 2. Claim 1, characterized in that the controller that controls the water supply flow rate is an opening controller of a water supply flow rate adjustment valve.
A water supply control device for a steam turbine plant as described in 2. 3. The bias signal is of a magnitude sufficient to reduce or increase the water supply flow rate in response to an increase or decrease in the water supply flow rate caused by opening and closing of the minimum flow valve. 3. The water supply control device for a steam turbine plant according to item 2.