JPH0129962B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a main steam stop valve, and more particularly to a main steam stop valve for a main turbine for a nuclear power plant.

A plurality of main steam stop valves are installed between the main turbine for a nuclear power plant and the reactor, and an electro-hydraulic control device (hereinafter referred to as EHC) is used to control the main steam stop valves (hereinafter referred to as MSV). ) is provided.

Figure 1 is a block diagram of the main parts of a nuclear power plant.
1 is the nuclear reactor, 2 is the main turbine, 3 is the main generator,
4 is located between the reactor 1 and the main turbine 2
Consisting of units MSV41, 42, 43, 44
At MSV, it is connected to reactor 1 via main steam header 5,
The main turbine 2 is a control valve (hereinafter referred to as CV) 6
connected via. 7 is the water pump, 8 is
In EHC, 9 is MSV opening control circuit, 10 is MSV
In the control circuit, the MSV control circuit 10 has a specific MSV.
The detection result of the limit switch 11 attached to 41 is input, and the MSV fully open signal or fully closed signal 12 is given to MSVs 42, 43, and 44.

FIG. 2 is a block diagram of the MSV control circuit 10.
11 is the limit switch attached to the specific MSV41,
12 is a CV steam room warming setting device, 13 is a setting circuit,
14 is speed setting device, 15 is MSV bias, 16
is the opening feedback signal, 17 is the adder, 18
1 is a servo amplifier, 19 is a servo valve, 20 is a hydraulic trip signal shutoff valve, and 21 is a cylinder.

Figure 3 is the MSV control circuit diagram, and 11 is the MSV41
The attached limit switch is a switch whose contacts open only when the MSV opening is 100%.Relay A 22 is operated by opening and closing of limit switch 11, and relay A 23, 24, and 25 are connected in parallel with each other. connected in series with the contact 22a of
Solenoid valve E26, solenoid valve F27, solenoid valve G28, and excitation contact 23 attached to MSV42, 43, and 44
Relays B, C, D with a, 24a, 25a
29 is a contact that opens when the main turbine trips, and 30 is a contact that opens during the MSV41 test.

In a nuclear power plant, as shown in FIG.
After passing through the CV 6, rotating the main turbine 2 and main generator 3 to generate electricity, and completing the work, the steam becomes condensed water and returns to the reactor 1 by the feed water pump 7. Consists of multiple units MSV41, 42, 43, 44
To control the opening of MSV4, multiple units are required.
The opening of a specific valve among the MSVs 41, 42, 43, and 44, MSV 41 in the case of FIG. 1, is controlled by a signal from the MSV opening control circuit 9.

Before starting the main turbine, warm-up operation of the CV steam room is performed, and during the warm-up operation, the MSV opening setting signal is sent to the CV steam room warm-up setting device 12 and the setting circuit 1.
3 is added to the opening feedback signal 16 in an adder 17, and the deviation signal is sent to a servo amplifier 18. The output signal of the servo amplifier 18 drives the servo valve 19, and when the shutoff valve 20 is in the reset state, the opening degree of the cylinder 21 is controlled to be constant, and one specific valve MSV 41 is continuously controlled to an intermediate opening degree.

Next, when trying to start the main turbine, if the speed setting device 14 is switched to a predetermined speed setting value, the signal from the CV steam room warm-up setting circuit 12 is cut off, and the MSV opening setting signal is switched. MSV bias 15
is added and MSV41 is fully opened. When the MSV 41 is fully open, a signal from the limit switch 11 that detects that it is in a state other than fully open is input to the MSV control circuit 10 shown in FIG.
42, 43, and 44 are fully opened. That is,
When MSV41 is fully opened, limit switch 11 changes from the closed state to the open state in FIG. 3, relay A22 becomes de-energized, contact 22a opens, and relay B23, relay C24, relay D25
is de-energized, and solenoid valves E26, F27, and G28 attached to MSV42, 43, and 44 are de-energized. MSV42, 43, and 44 are on/off valves, and are configured so that they do not have an intermediate opening when either fully open or fully closed, but are fully open when solenoid valve E26, solenoid valve 27, and solenoid valve G28 are not energized. Therefore, all MSVs 41, 42, 43, and 44 are fully opened and the main turbine 2 is started. Next, the speed of the main turbine 2 is increased by a speed control device (not shown) and normal operation begins. In addition, during normal operation, MSV
41 is fully open → fully closed → fully open, the limit switch 11 is in the closed state, so at this time, the contact 30 that opens during the MSV41 test is operated, and relay B23 and relay C
24. Prevents relay D25 from being energized.
Also, when the main turbine trips, the MSV hydraulic power source (not shown) is cut off by the trip signal.
Since the MSV is fully closed, the main turbine trip activates the contact 29, which opens the contact, and relay B23,
This prevents relay C24 and relay D25 from being excited.

In other words, the warm-up operation of the CV steam room is performed using MSV41,
Only one valve MSV41 of 42, 43, and 44 is opened (intermediate opening degree), and in the subsequent main turbine speed-up process, all MSV41 and 4 valves are opened (intermediate opening degree).
In order to fully open 2, 43, and 44, first,
When the MSV 41 is fully opened using the MSV opening control circuit 9 and the limit switch 11 detects that it is fully opened, the remaining MSV 42,
43 and 44 are configured to be automatically fully opened.

In this way, after the speed-up operation is finished and the normal operating state is entered, this state will be maintained for a long time. This MSV can easily perform a speed increase process of several hours, but during long normal operation,
If the limit switch 11 attached to MSV41 closes due to a failure, the remaining MSV42, 43,
44 is closed and all MSVs are fully closed.
That is, in Fig. 3, MSV41 is originally in the open state only when the opening degree is 100%, but MSV41
When the attached limit switch 11 closes due to a failure, relay A22 is energized, and as a result, relay B23, relay C24, and relay D25 are energized, and the remaining MSVs 42, 43, and 44 are fully closed.
When MSVs 41, 42, 43, and 44 are completely closed in this way, it becomes impossible for the nuclear power plant to continue operating. That is, the plant is constantly exposed to the danger of stopping the plant due to the failure of one limit switch, which is a major drawback in terms of a reduction in the operating rate.

The present invention aims to eliminate these drawbacks and to provide a main steam stop valve that can prevent unnecessary stoppage of a plant. has a first limit switch whose contacts are open only when the opening degree is 100%, and a first relay connected in series to the first limit switch to fully open the remaining valves; The main steam stop valve is equipped with a control means that detects whether one valve is fully open or not fully open, and opens and closes the remaining valves according to each detection result. A second limit switch is connected in series to the second limit switch, and its contacts are connected in series to the contacts of the first relay, and the remaining valves are closed. and a second relay to prevent the first relay from entering the condition.
A plurality of limit switches are connected in series to the plurality of limit switches, and the contact point is connected to the first relay, the contact of which closes when it is detected that the remaining valve has an opening of 90% or more. A second feature is that the valve further includes a second relay connected in series with the contact point of the valve to prevent the remaining valve from closing.

As the signal to prevent the MSV from fully closing automatically, we used a signal that is always emitted during normal operation.
This signal can be supplied by a relay energized by a contact that opens when the main generator or circuit breaker closes, or by a residual
Detects when MSV reaches 90% opening or higher
This is done by inserting a relay contact that is energized by the limit switch attached to the MSV41.

Examples will be described below.

FIG. 4 is a control circuit diagram of the main parts of one embodiment,
MSV4 is 4 units MSV41, 42, 43, 4
4 is shown. In this diagram, the same parts as in Figure 3 are given the same reference numerals, but the difference between this control circuit diagram and the control circuit diagram in Figure 3 is that relay B23, relay C24, which are connected in parallel to each other,
Specific MSV41 connected in series with relay D25
The MSV4 is connected to the series circuit of the contact 22a of the relay A22, which is operated by opening and closing the attached limit switch 11, the contact 29, which opens when the main turbine trips, and the contact 30, which opens during the MSV41 test.
A contact 34a operated by a relay K34 connected in series with limit switches 31, 32, 33 whose contact is closed when the opening degree of 1, 42, 43 is 90% or more.
is inserted.

In the device of this embodiment, when starting the main turbine,
MSV41 is fully open, limit switch 11 that detects a state other than MSV fully open has a contact open, contact 22a of relay A22 is open, and relay B2
3. Relay C24 and relay D25 are de-energized, and solenoid valve E26 and solenoid valve F27 attached to MSV are activated.
Solenoid valve G28 becomes de-energized, and MSV42, 43,
The limit switches 31, 32, and 33 (contacts closed when 90% or more) detect the opening of 44 at 90% or more close their contacts, and relay K34 is energized. This relay K3
Since the contact No. 4 is inserted in series with the contact of relay A22 in the excitation circuit of relay B23, relay C24, and relay D25, a single failure of limit switch 11 that detects a state other than MSV41 fully open will cause limit switch 11 to be activated. Even if the contacts are closed and relay A22 is energized, MSV41,
42, 43 can be automatically prevented from being fully closed.

Therefore, according to this embodiment, during the warm-up operation of the CV steam chamber before starting the main turbine and when starting the main turbine, after the MSV 41 is fully opened, the MSVs 42, 43, and 44 are fully opened by this full open signal, and the main turbine is started. 2 starts up and becomes normal operation, and MSV
When the limit switch 11 attached to 41, which detects a position other than fully open, malfunctions, MSV42, 4
3 and 44 are automatically prevented from being fully closed, automatic shutdown of the plant can be avoided, and the operating rate can be improved.

FIG. 5 is a control circuit diagram of main parts of another embodiment,
This example is also a case where the number of MSVs is four valves. In this diagram, the same parts as in Figure 4 are given the same reference numerals, but the difference between this control circuit diagram and the control circuit diagram in Figure 3 is that the MSVs 42, 43, and 44 are prevented from becoming fully closed. As a means for
is connected in series to relay A22, and its contact 36a is connected in series to relay A22.
This embodiment operates in the same manner as the embodiment shown in FIG. 4 in that it includes a relay H36 connected in series with the contact point of FIG. 4, and the same effects can be obtained.

In addition, in any of the examples, the MSV is 4 unit MSV
Although the case where there are more than four pieces has been described, it can be similarly used in cases other than four pieces.

As described above, the present invention makes it possible to provide a main steam stop valve that can prevent unnecessary stoppage of a plant, and has great industrial effects.

[Brief explanation of drawings]

Figure 1 is a block diagram of the main parts of a nuclear power plant, Figure 2 is a block diagram of the main steam stop valve control circuit, and Figure 3 is a block diagram of the main steam stop valve control circuit.
The figure is a control circuit diagram of a conventional main steam stop valve, and FIGS. 4 and 5 are control circuit diagrams of different embodiments of the main steam stop valve of the present invention. 1... Nuclear reactor, 2... Main turbine, 4,41,
42, 43, 44...Main steam stop valve (MSV), 9
...MSV opening control circuit, 10...MSV control circuit, 11...limit switch attached to specific MSV41, 22...relay A, 23...relay B,
24...Relay C, 25...Relay D, 26...
Solenoid valve E, 27...Solenoid valve F, 28...Solenoid valve G, 29...Contact that opens during a main turbine trip, 30...Contact that opens during a specific MSV41 test, 31, 32, 33 ...MSV opening 90
% or more limit switch whose contacts are closed, 3
4...Relay K, 35...Contact that opens when the main generator circuit breaker is turned on, 36...Relay H.

Claims (1)

[Scope of Claims] 1. A first limit switch consisting of a plurality of unit main steam stop valves, the contact of which opens only when a particular one of the valves is 100% open, and a first limit switch connected in series with the first limit switch. and a first relay that is connected to the valve to fully open the remaining valves, detects whether the specific one valve is fully open or is in a state other than fully open, and responds to each of the detection results. In the main steam stop valve, which is provided with a control means for opening and closing the remaining valves, a second limit switch whose contacts are opened when the main generator or disconnector is turned on, and a second limit switch connected in series with the second limit switch, is provided. a second relay connected to the main steam stop valve, the contacts of which are connected in series with the contacts of the first relay to prevent the remaining valve from closing. 2 Consisting of a plurality of unit main steam stop valves, a first limit switch whose contact is open only when one particular valve is 100% open, and the remaining valves connected in series to the first limit switch. and a first relay that fully opens the valve, detects whether the specific one valve is fully open or is in a state other than fully open, and controls the remaining valves according to each detection result. In a main steam stop valve provided with a control means for opening and closing, a plurality of limit switches whose contacts close when it is detected that the remaining valves have an opening degree of 90% or more, and the plurality of limit switches and a second relay whose contacts are connected in series with the contacts of the first relay to prevent the remaining valves connected in series from closing. Steam stop valve.