JPH04264296A - Controlling apparatus for feed water of steam generating plant - Google Patents

Abstract

PURPOSE:To protect a feed water pump by controlling water feeding by conducting a proportional-plus-integral operation with a feed water control valve opening detection signal used as a starting point, when a feed water flow rate exceeds a reference value. CONSTITUTION:Judging the relation between a pump number determining unit 27 and a feed water flow rate detection signal 17, a feed water flow rate determining unit 30 outputs a feed water pump protection signal 33. when a protection signal 33 is received, a changeover is made from a water level controller 23 for increasing the feed water flow rate to a feed eater flow rate controller 36 for constantly controlling the flow rate at a set value for protection of a pump, on the basis of three element signals of a reactor water level 14, a main steam flow rate 19 and the feed water flow rate 17. Since the feed water flow rate controller 36 controls the flow rate according to a feed water control valve opening signal 48 until the pump is protected, a flow rate control having little overshoot can be realized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to water level control of a steam generator and protection of feedwater pumps, and more particularly to a feedwater control system for a steam generation plant suitable for application to a boiling water nuclear power plant.

0002

2. Description of the Related Art A conventional water supply control system for a boiling water nuclear power plant is disclosed in Japanese Patent Application Laid-Open No. 197499/1983. The water supply control device receives signal values of the water level in the nuclear pressure vessel (hereinafter referred to as reactor water level), the water supply flow rate, and the main steam flow rate, and controls the water supply flow rate supplied to the reactor pressure vessel, thereby controlling the reactor water level. Keep the water level at a predetermined level.

[0003] In a plant where three motor-driven water pumps are installed in parallel, two motor-driven water pumps are driven by electric motors that rotate at a constant speed, so the opening degree of the water supply control valve provided on the discharge side of the motor-driven water pump varies. The water supply flow rate is adjusted by controlling according to the valve opening request signal output from the water supply control device.

[0004] In such plants, selective control rods (SRI
) If a drop in the reactor water level occurs due to the insertion of
As shown in , even if the input amount has the same reactivity, depending on the SRI pattern, the water level may drop by about -15 cm as shown by the solid line, or by about -40 cm as shown by the broken line.

In the former case, the water supply control device 11 opens the water supply control valve as the water level drops, and the water supply flow rate temporarily increases to 110%, but as the reactor water level recovers, the water supply flow rate also decreases. , the change ends.

On the other hand, in the latter case, as shown by the broken line, the water supply flow rate increases according to the signal from the water supply control device in accordance with the initial drop in the reactor water level, reaching approximately 135%. At this time, the water pump was in a runout state, and there was a possibility that the water pump would be damaged.

[0007]

[Problem to be solved by the invention] The above-mentioned conventional technology does not take into account the runout protection or overload prevention of the feedwater pump, and if an event occurs in which the reactor water level drops due to selective control rod insertion, etc. In addition, there was a possibility that the water supply flow rate would increase too much and exceed the runout flow rate.

An object of the present invention is to prevent runout of the water supply pump, and further to reduce the amount of overshoot of the water supply flow rate from the runout setting value immediately after activation of the runout prevention mechanism, and to adjust the water supply flow rate to the water supply flow rate pump trip value. The object of the present invention is to provide a water supply control device that does not lead to water damage.

[0009]

[Means for solving the problem] The above problem is solved by providing a means for detecting the water supply flow rate and a water supply flow rate controller for controlling the water supply flow rate to a specified value, and when the water supply flow rate exceeds the specified value, the water level This problem can be solved by switching from control to constant water flow rate control.

[0010] Furthermore, by constantly tying back the water supply flow rate controller to the water supply control valve opening signal until the roundout protection circuit is activated, overshoot of the water supply flow rate can be reduced and the water supply pump trip value can be reduced. You can avoid this from happening.

[0011]

[Operation] The water supply flow rate controller is always tied back with the water supply control valve opening signal until the runout protection operation is performed. As a result, when the water supply flow rate exceeds the specified value and the runout protection mechanism is activated, the water supply control valve opening request signal increases to the actual water supply control valve position, and proportional/integral calculations are performed from that value. Therefore, overshoot from the water pump protection specified value can be reduced, and the water pump trip value will not be reached.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS A water supply control system for a steam generation plant, which is a preferred embodiment of the present invention applied to a boiling water nuclear power plant, will be described below with reference to FIGS. 1, 2 and 3. The pressure vessel of a boiling water nuclear power plant is a steam generator.

During normal operation of a boiling water nuclear power plant, cooling water (feed water) heated in the reactor core 2 in the reactor pressure vessel (steam generator) 1 turns into steam.

This steam is discharged from the reactor pressure vessel 1 and sent to the turbine 4 through the main steam pipe 3. Steam exhausted from the turbine 4 is condensed into water by a condenser 5. The condensed water discharged from the condenser 5, that is, the feed water that becomes the cooling water for the reactor, is passed through the water supply pipe 6 to a condensate demineralizer (
(not shown), a condensate pump 7, and a feed water heater (not shown).

Furthermore, the water supply is carried out through branch pipes 8A and 8A of the water supply piping.
Three MD-RFP9A, 9B installed in 8B, 8C
, 9C, and the two water supply regulating valves 10A and 10B are further adjusted by the valve opening command signal 12 from the water supply control device 11 to obtain an appropriate water supply flow rate, and the supply water is supplied to the reactor 1. Ru. The water supply flow rate is controlled by the water supply control valves 10A and 10B using a water level signal 14 from a water level gauge 13 that measures the water level in the reactor pressure vessel 1, a water supply flow rate signal 17 from a water flow meter 16 provided in the water supply piping 15, and The feedwater flow rate control device 1
1.

That is, as shown in FIG. 2, the main steam flow rate signal 1
The water level deviation signal 22 is the difference between the reactor water level setting signal 21 and the sum signal of the signal obtained by applying the mismatch gain 20 to the deviation signal of the water supply flow rate signal 17 and the reactor water level signal 14.
Then, the signal is input to the water level controller 23, where proportional integral calculation is performed, and outputted from the water supply control device as the water supply control valve opening request signal 12.

A water supply control device according to the present invention is shown in FIG.

In addition to the three-element water level controller, this control device also uses a signal 2 that detects the closed state of the breakers 25A, 25B, and 25C of the water supply pump motors 24A, 24B, and 24C.
6A, 26B, and 26C, the number of pumps determining unit 27,
2 Out of logic determines whether one or two water pumps are running, and the one pump running signal is 29 or the two water pumps are running signal 2.
8 is sent to the water supply flow rate control determination section 30.

In the water supply flow rate control determination unit 30, if the water supply flow rate signal 17(c) exceeds the specified value D while two water supply pumps are in operation, or exceeds the specified value E while one water supply pump is in operation. , water pump protection signal 3 is activated at or gate 31.
Outputs 2. This signal is self-held and output as the water pump protection signal 33.

When this signal is output, the switch 35 switches from the normal 100% signal generator 34 to the water supply flow rate controller 36.

In the water supply flow rate controller 36, the water supply flow rate signal 2
7 and the signal from the water supply pump number determination unit 27, a deviation signal 39 between the given set value 38 when one or two water supply pumps is operated is input, proportional and integral calculations are performed, and the water supply flow rate is controlled. output as a device output signal. During normal operation, that is, when the water supply pump protection signal is off, the water supply control valve opening detection signal 52 is tied back to the water supply flow rate controller 36, so when the water supply pump protection signal 33 is turned on, the water supply flow rate control output is 37 starts control from the same value as the water supply control valve opening detection signal 52 at that time, so the amount of overshoot of the water supply flow rate from the specified value is reduced, and the water supply pump trip value is never reached.

When the water supply pump protection signal 33 is turned on, the water supply flow rate controller signal 37 is input to the low value priority circuit 42 and compared with the water level controller output signal 12 to generate the valve opening request signal 41.
is output as As a result, when the water supply flow rate exceeds the protection setting value determined by the number of operating water supply pumps, constant water supply flow rate control is performed.

On the other hand, when the water supply pump protection is on, the output signal 40 of the water supply flow rate controller 36 is biased (+10%).
The integrator upper limit value 43 to which 42 is added is the water level controller 2.
3, the upper limit of the integrator output is input to the controller 23, and the upper limit of the integrator output is limited to the above limit value.

[0024] As a result, even if the feed water pump protection operation continues for a long time, the integrator of the water level controller will not become saturated, so that when the reactor water level recovers, water level control can be promptly resumed through the low value priority circuit. .

In addition, the water level controller output 12 and the low value priority circuit output 41 are input to the water supply pump protection reset determination section 44 , and the water level controller output signal 12 is determined by the signal comparator 45 from the water supply control valve opening request signal 37 . becomes smaller, and after a delay of about five seconds by the timer 46, a reset signal 47 is sent to the water supply control determining section 30, and by resetting the self-holding circuit, the water pump protection signal 33 is reset.

[0026] Details of embodiments of the present invention are shown below.

FIG. 5 shows changes in the feed water flow rate, reactor water level, and controller output when the main steam isolation valve is fully closed, using solid lines (conventional three-element system) and broken lines.

In the conventional system (solid line), the water level controller increases the water supply flow rate to about 140% in response to the drop in the reactor water level due to the closing of the main steam isolation valve. Therefore, the runout flow exceeds the set value of 110% when two water pumps are operated, which poses a problem in terms of equipment protection. Figure 6 shows the feed water flow rate and reactor water level when the tie back of the feed water flow rate controller is set to the water level controller output signal (solid line) and when the feed water control valve opening signal (broken line, the present invention) is used. , which shows the change in the controller output.

In the case of tieback to the water level controller output signal, the overshoot of the water supply flow rate immediately after the water supply pump protection mechanism is activated reaches approximately 120%. In addition, in plants where condensate filtration equipment and condensate desalination equipment are installed, the water supply pump trip value is temporarily reached.

On the other hand, in the present invention, the maximum value of the water supply flow rate is about 114%, which is equal to the water supply pump trip value of 117%.
%, and damage to the water pump can be avoided. Other embodiments of the present invention will be described.

In the previous embodiment, the water supply flow rate controller signal was made to match the water supply control valve opening signal until the water supply pump protection operation was applied, but as shown in FIG. The value obtained by subtracting a certain deviation (5%) is made to match the water supply flow rate controller output.

This makes it possible to avoid reaching the water supply pump trip value, as shown in FIG.

[0033]

Effects of the Invention According to the present invention, when the reactor water level suddenly decreases due to closing of the main steam isolation valve, the water supply flow rate increases due to water level control, and the feed water pump protection operation is performed, the specified feed water flow rate can be adjusted. The amount of overshoot from the value is reduced, and water pump equipment can be protected.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a water supply control device and boiling water nuclear power plant according to the present invention.

FIG. 2 is a detailed view of the water supply control device according to the invention.

FIG. 3 is a detailed view of the water supply control device according to the invention.

FIG. 4 is an explanatory diagram of plant behavior when SRI is inserted using a conventional water supply control device.

FIG. 5 is an explanatory diagram of plant behavior when the main steam isolation valve is closed using a conventional water supply control device.

FIG. 6 is an explanatory diagram of plant behavior when the main steam isolation valve is closed by the water supply control device of the present invention.

FIG. 7 is a system diagram of another embodiment of the present invention.

[Explanation of symbols]

1...Reactor pressure vessel, 2...Reactor core, 4...Main steam piping, 4...
Turbine, 5... Condenser, 6... Water supply piping, 7... Condensate pump, 8A, 8B, 8C... Water supply branch pipe, 9A, 9B, 9C...
Electrically driven water supply pump, 10A, 10B...water supply control valve, 1
1... Water supply control device, 12... Water supply control valve opening request signal, 1
3...Reactor water level detector, 14...Reactor water level signal, 15...
Water supply piping, 16... Water supply flow rate detector, 17... Water supply flow rate detection signal, 18... Main steam flow rate detector, 19... Main steam flow rate detection signal.

Claims (1)

[Claims] 1. A condenser of a steam generator, a water supply pipe that leads water supply from the condenser to the steam generator, a water supply pump provided in the water supply pipe, and a water supply flow rate that is determined by the water level of the steam generator; In a feed water control device for a steam generation plant equipped with a feed water control valve that is adjusted by three-element control using signals of a feed water flow rate and a main steam flow rate, the feed water flow rate signal output from the feed water flow rate detection means and the feed water flow rate detection means is provided. In a runout protection mechanism that is equipped with a water supply flow rate controller that controls the water supply flow rate to the specified value from three-element control when the water flow rate exceeds the specified value, the output signal of the water supply flow rate controller is 1. A water supply control device for a steam generation plant, comprising means for matching the opening degree signal of the water supply control valve output from the water supply control valve.