JPH0416601B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to turbine bypass devices in thermal and nuclear power plants.

[Technical background of the invention]

FIG. 1 shows part of a typical nuclear power plant system with a turbine bypass system. In the figure, steam supplied from a steam generator (not shown) is passed through a main steam pipe 1, a main steam stop valve 2 inserted in the main steam pipe 1, and a main steam stop valve 2 that cuts off the supply of steam to the turbine. The high-pressure turbine 4 is reached through the steam control valve 3 that controls the steam flow. The steam that has done work in the high-pressure turbine 4 is further introduced into each of the low-pressure turbines 5 arranged in three systems in parallel, performs work in the low-pressure turbines 5, and then is condensed in the condenser 6. On the other hand, the turbine bypass pipe 7 branched from the main steam pipe 1 branches into three systems, each of which is equipped with a turbine bypass valve 8 and connected to a pressure reducer 9 consisting of a multi-stage orifice connected to the condenser 6. are doing. The pressure reducer 9 is supplied with cooling water from an external cooling water tank or the like to a cooling water pipe 10 and a cooling water spray valve 11 provided in the cooling water pipe 10.
supplied through. When the steam turbine bypass valve 8 is opened, the cooling water spray valve 11 is also fully opened, and the main steam passing through the turbine bypass pipe 7 is cooled and guided to the condenser 6 so as to bypass the turbine. It's becoming like that.

Such turbine bypass systems are used in thermal and nuclear power plants, and their purpose is to ensure that the steam generator can continue operating in a suitable manner even when the system is under load or disconnected during plant startup or turbine operation. Part or all of the steam generated in the steam generator is recovered in the condenser. The operation of this turbine bypass system will be explained below using examples of plant startup and system load interruption.

When starting up the plant When starting up the plant, at least the minimum required amount of steam is generated in the steam generator, and overheating of the steam generator itself is prevented and stability is ensured.
Among the steam generated at this time, main steam other than the amount of steam necessary for starting the turbine is recovered to the condenser 6 via the turbine bypass pipe 7. As the load on the turbine increases, the opening degree of the steam control valve 3 gradually increases, and as more steam is required to be supplied to the turbine, the turbine bypass valve 8 gradually closes and the amount of bypass steam decreases. Normally, the turbine is under constant load (rated load
25 to 30%), the turbine bypass valve is fully closed.

System load interruption If the load is interrupted due to an accident in the power system while the turbine is operating normally,
The steam control valve 3 closes quickly to cut off the main steam to the turbine. At the same time, the output of the steam generator is controlled to decrease, but the pressure of the steam generator rapidly increases due to the sudden closing of the steam regulating valve 3. In conjunction with the sudden closing of the steam regulating valve 3, the turbine bypass valve 8 suddenly closes. It will be opened. The main steam passing through the turbine bypass pipe 7 is then reduced in pressure by a pressure reducer 9, further reduced in temperature by cooling water, and recovered in a condenser 6. Note that the cooling water spray valve 11 that supplies cooling water is opened in conjunction with the turbine bypass valve 8. In this way, pressure increases in the steam generator can be prevented, thereby avoiding reactor scrams and emergency shutdowns of the plant. Additionally, the turbine bypass valve, which opened suddenly at this time, is now closed as the output of the steam generator decreases, and when the output of the steam generator reaches about 30 to 50% of the rated value, the turbine shuts down inside the power plant. It will be operated depending on the load, and excess main steam will be bypassed to the condenser while waiting for the system to be restored.

[Problems with background technology]

Now, as mentioned above, in the case of a steam turbine plant having a turbine bypass system, since the main steam at high temperature and high pressure is directly introduced into the condenser, the turbine bypass system is designed to prevent damage to the condenser due to this. The system reduces the pressure and temperature of the main steam. In particular, in order to reduce the temperature of steam, in the past, as shown in FIG. 1, a cooling water spray valve 1 is
1 was opened to supply cooling water from the cooling water pipe 10, but in the unlikely event that the turbine bypass valve 8
If only the cooling water spray valve 11 is opened and the cooling water spray valve 11 is not operated, the steam will flow into the condenser 6 without being reduced in temperature. Needless to say, when such an unexpected situation occurs, it is sufficient to close the turbine bypass valve 8, but in that case, the steam generator must be stopped. The original purpose of the bypass system will not be fulfilled at all.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and its purpose is to prevent the cooling water spray valve from opening when the turbine bypass system is activated due to load or interruption, etc., and the temperature of the steam is not reduced. Another object of the present invention is to provide a turbine bypass device that can protect a condenser, ensure safety, and avoid shutdown of a plant or steam generator.

[Summary of the invention]

The present invention provides a turbine bypass valve installed in a line branching from a main steam pipe and connected to a condenser, and a line supplying cooling water for cooling steam introduced from the line to the condenser. A cooling water spray valve is provided, and when the turbine bypass valve opens, the cooling water spray valve is opened and an operation of the cooling water spray valve is detected, and the cooling water spray valve is not opened normally. The turbine bypass device includes a control device that fully closes the turbine bypass valve after a certain period of time when the turbine bypass valve is closed.

In other words, conventionally, the opening of the cooling water spray valve has been detected by detecting the opening of the turbine bypass valve and interlocking with this, but in the present invention, the operation of the cooling water spray valve is further detected, and if the cooling water If the spray valve does not open normally, the turbine bypass valve is fully closed after a certain period of time. However, during the certain period of time when the lever turbine bypass valve is open, the bypass steam is not supplied with sufficient cooling water and its temperature is only incompletely reduced, but this high-temperature bypass steam is introduced. By determining the above-mentioned time so that the rise in the internal temperature of the condenser falls within an allowable range, it is possible to suitably process the steam generated until the output of the steam generator decreases.

[Embodiments of the Invention] Examples of the present invention will be described below with reference to the drawings. In the following drawings, when the same parts as shown in FIG. 1 are shown, the same reference numerals are given and the explanation thereof will be omitted.

FIG. 2 shows a system of a steam turbine plant equipped with a turbine bypass device according to this embodiment, in which a control device 20 connected to turbine bypass valves 8a, 8b, 8c and cooling water spray valves 11a, 11b, 11c is installed. The above-mentioned valves are controlled by the control device 20.

The internal configuration of the control device 20 is shown in FIG. Third
In the figure, a turbine speed signal 30 detected from the turbine is input to a steam amount calculator 33 together with a set load signal 32 set in a load setter 31. This steam amount calculator 33 calculates the amount of steam required for turbine operation using two parameters: the magnitude of the load and the deviation between the actual turbine speed and the rated speed. The thus obtained required steam amount signal 34 is subjected to load restrictions based on various factors or restrictions such as the reactor design maximum steam flow rate in a limiter 35, and becomes a steam control valve flow rate signal 36. On the other hand, the main steam pressure signal 37 indicating the steam pressure in the reactor is input to the main steam amount calculator 38, and the main steam amount calculator 38 calculates the amount of steam generated in the reactor. Then, the bypass steam calculator 39 subtracts the aforementioned steam control valve flow rate from this reactor generated steam amount, and a turbine bypass valve flow rate signal 40 is obtained as the difference. This turbine bypass valve flow signal 40 is branched into three directions, and each turbine bypass valve 8a, 8b, 8
c is transmitted to each independently provided control system, of which only the system for the turbine bypass valve 8c is illustrated here.

Now, such turbine bypass valve flow signal 40
is input to the turbine bypass valve control device 41. This turbine bypass valve control device 41 controls the servo valve of the turbine bypass valve 8c based on the turbine bypass valve flow signal 40, and as a result controls the opening degree of the turbine bypass valve 8c. For this purpose, a turbine bypass valve control signal 42 is output to the turbine bypass valve 8c. Further, the turbine bypass valve control device 41 detects that the signal status of the turbine bypass valve flow signal 40 or the turbine bypass valve control signal 42 is in a state in which the turbine bypass valve is opened, and opens the cooling water spray valve 11c. A cooling water spray valve open signal 43 is output. code 44
is a contact point that detects the operation of the cooling water spray valve 11c, and the delayed activation relay 46 is energized or de-energized via the operation detection contact 45 similarly installed for the turbine bypass valve 8c. There is. The turbine bypass 8c is connected to one end of the contact 47 driven by the delayed activation relay 46, and the turbine bypass valve control device 41 and the fully closed signal transmitter 48 are connected to the other end, and the delayed activation relay 46 is connected to the turbine bypass 8c. 46, the turbine bypass 8c is connected to either the turbine bypass valve control device 41 or the fully closed signal transmitter 48.

FIG. 4 shows the control circuit for the turbine bypass valve 8c and the cooling water spray valve 11c in more detail. In FIG. 4, a turbine bypass valve flow rate signal 40 transmitted from the bypass steam calculator 39 is input to a valve position control circuit 50. This valve position control circuit 50 includes each turbine bypass valve 8.
Different valve opening start biases 51 are applied to a, 8b, and 8c, and at the same time, a valve opening signal 52 is input which gives a valve opening corresponding to the steam flow rate. In the valve position control circuit 50, the turbine bypass valve flow signal 40 is calculated in accordance with the valve opening degree signal 52 and the valve opening start bias 51 and converted into a turbine bypass valve control signal 42.

On the other hand, the valve position control circuit 50 is provided with a bias valve open signal detector 53 that detects that the turbine bypass valve control signal 42 is in the valve "open" state. This bypass valve opening signal detector 53
When the turbine bypass valve control signal 42 detects that the valve is in the "open" state, it conducts a contact 55 connected in series to the cooling water spray valve solenoid 54. When this contact 55 becomes conductive, current is supplied to the cooling water spray valve solenoid 54 via the control bus lines P ₀ and P ₁ , and the cooling water spray valve solenoid 54 becomes energized. That is, the turbine bypass valve control signal 42 causes the valve to be "open".
In this state, the cooling water spray valve solenoid 54 is energized to open the cooling water spray valve 11c. Connected in parallel with the contact 55 is a contact 56 which becomes non-conductive when the relay 57 is energized. The relay 57 connects the control bus line P ₀ ,
_P1 , so when the turbine bypass valve 8c opens, the bypass valve open detection switch 45 becomes non-conductive, the relay 57 becomes de-energized, and the contact 56 becomes conductive. In order to open the cooling water spray valve 11c without error, two systems, a contact 55 and a contact 56, are provided for energizing the cooling water spray valve solenoid 54, and these contacts are connected when the turbine bypass valve 8c is opened. Both are designed to conduct.

On the other hand, a delayed activation relay 46 is connected to a contact 58 which becomes non-conductive when the relay 57 is energized, like the contact 56, through a contact 44 which becomes conductive when the cooling water spray valve 11c does not operate. has been done. This delayed activation relay 46 is energized to drive its contacts 47 after a certain period of time has elapsed since it was energized. The delayed activation relay 46
One end of the contact 47 is connected to the servo valve 59 of the turbine bypass valve 8c, and the other end is connected to the valve position control circuit 50 and the fully closed signal transmitter 48. The contact 47 is connected to the delay activation relay 4.
When the delay activation relay 46 is energized, the servo valve 59 is connected to the valve position control circuit 50, and when the delay activation relay 46 is energized, the servo valve 59 is connected to the fully closed signal transmitter 48.

Next, the operation of this embodiment will be explained. The turbine bypass system mainly operates at the time of startup and when the system load is interrupted during operation, and here, the latter case will be explained using as an example the case where the system load is interrupted during turbine operation.

During normal turbine operation, the turbine bypass valve flow signal 40 output from the bypass steam calculator 39 is 0 or a negative value, and therefore the turbine bypass valve control signal 42 output from the valve position control circuit 50 is also Bypass valve is in “closed” state. Since the turbine bypass valve 8c is fully closed by these signals, the bypass valve open detection switch 45 is in a conductive state, and the relay 57 connected to the bypass valve opening detection switch 45 is energized, and the contacts 56 and 58 is non-conductive. Further, as described above, when the turbine bypass valve control signal 42 indicates the bypass valve "closed" state, the contact 55 which is conductive when the bypass valve is closed is also rendered non-conductive by the turbine bypass valve opening signal detector 53. There is. Therefore, both contacts 55 and 56 are non-conductive and the cooling water spray valve solenoid 54 is not energized, so the cooling water spray valve 11c
will never open. Further, since the contact 58 is also non-conductive, the delay activation relay 46 is not activated, and the contact 47 driven by the delay activation relay maintains the conduction between the servo valve 59 and the valve position control circuit 50.

If the system load is interrupted in this state, the main steam stop valve is fully closed, the steam control valve flow rate signal 36 becomes 0, and the bypass steam operator 39
Turbine bypass valve flow signal 40 output from
increases rapidly. This turbine bypass valve flow signal 4
0, the valve position control circuit 50 increases the turbine bypass valve control signal 42 to control the servo valve 5.
9 to suddenly open the turbine bypass valve 8c. At the same time, the turbine bypass valve opening signal detector 53 detects that the turbine bypass valve control signal 42 has increased, and makes the contact 55 conductive. On the other hand, when the bypass valve open detection switch 45 detects that the turbine bypass valve 8c has opened, the relay 57 is energized and the contacts 56 and 58 are made conductive.
Therefore, the cooling water spray valve solenoid 5 is activated by conduction of either the contact 55 or the contact 56.
4 is excited and the cooling water spray valve 11c opens. If the cooling water spray valve 11c operates normally and opens at this time, the temperature of the turbine bypass steam is reduced by the cooling water supplied through the cooling water spray valve 11c, and the turbine bypass steam is collected in the condenser. The open state of the cooling water spray valve 11c is maintained as long as the turbine bypass valve 8c is open, that is, as long as the contact 55 or 56 is conductive.

On the other hand, if the cooling water spray valve 11c does not open normally even though the turbine bypass valve 8c is open, the present embodiment operates as follows. That is, the turbine bypass valve 8
When c opens, turbine bypass valve open detection switch 45 becomes conductive, relay 57 is energized, and contact 5
6 and 58 are conductive. Excitation current flows through the cooling water spray valve solenoid 54 due to conduction of the contact 56, but when the cooling water spray valve 11c does not open normally due to a failure of the valve body or a disconnection of the solenoid, the cooling water spray valve 11c A contact 44 for detecting an operational malfunction becomes conductive. At this time, since the contact 58 is also conductive due to the excitation of the relay 57, the delay activation relay 46 starts operating at the same time as the contact 44 is conductive. This delayed activation relay 4
6 is adapted to drive the attached contact 47 after a certain period of time has elapsed after being energized as described above, and the operation of this contact 47 causes the servo valve 59 of the turbine bypass valve 8c and the valve position control circuit 50 to be activated. The servo valve 59 is now connected to the fully closed signal transmitter 48 instead. By being connected to this fully closed signal transmitter 48, a turbine bypass valve fully closed signal is input to the servo valve 59, and even though the turbine bypass valve 8c has opened, the cooling water spray valve 11c does not open normally. In this case, the turbine bypass valve 8c is fully closed after a certain period of time has elapsed since the turbine bypass valve 8c opened, that is, the time from when the delay activation relay 46 is energized until the contact 47 is driven. It is becoming more and more like this.

In the above explanation, only one system of turbine bypass valves 8c has been described as an example, but the remaining two valves 8a and 8 of the three systems of turbine bypass valves shown in FIG.
The same applies to b. Note that the opening start bias 51 shown in FIG. 4 is provided for each of these three turbine bypass valves 8a, 8b, and 8c.
Different bypass values are set for each of the valves, and normally the three valves are opened sequentially.

A curve 71 shown in FIG. 5 shows the temporal change in the turbine bypass steam flow rate after the system load is interrupted, and the vertical axis represents the ratio of the bypass steam flow rate to the rated main steam flow rate. As is clear from the figure, the amount of bypass steam increases rapidly immediately after the load is turned off and eventually reaches its maximum. At this time, the entire amount of main steam generated in the reactor is bypassed, but since the reactor output is immediately reduced rapidly, the amount of bypass steam also gradually decreases accordingly. Also, the dashed-dotted straight lines 72a, 72b, 72c shown in the same figure.
shows the bypass allowable steam amount when only one turbine bypass valve is open, when only two turbine bypass valves are open, and when all three turbine bypass valves are open, respectively. These figures show that cooling water is not supplied to one of the three turbine bypass valve systems out of the three systems in this example even though the bypass valve has opened, and after a certain period of time the turbine bypass valve is closed. It can be seen that even if the valve is closed, the remaining two valves can sufficiently process the bypass steam.

FIG. 6 is a diagram showing the relationship between the elapsed time after the load is cut off and the temperature change inside the condenser. A curve 81 in the figure shows a case where the cooling water spray valve opens normally, and the temperature of the steam is reduced by the cooling water, so that the temperature rise inside the condenser is small. On the other hand, a curve 82 shows the temperature change when the turbine bypass device according to this embodiment is operated, and the turbine bypass valve is opened with no cooling water supplied for a certain period of time after the load is cut off, and during this period the steam is restored without being cooled. This shows that even when the water is introduced into the water condenser, the temperature inside the condenser only rises to a level that has a sufficient margin over the design limit value. Curve 83 shown by a broken line shows the case where the turbine bypass valve continues to be opened even though cooling water is not supplied. reach.

Note that the delay time of the delayed activation relay 46 in the embodiment, that is, the contact 47 attached thereto after being energized
The time required for activation is determined as appropriate depending on the amount of bypass steam, the strength of the condenser, and the like. In this case, the delay time may be variable so as to correlate with the bypass steam flow rate. It goes without saying that the switches and contacts that detect the operating status of the turbine bypass valve and cooling water spray valve may be of the type that is attached directly to the valve body or of any other type. There is no such place. Furthermore, this embodiment can be suitably implemented even in a system in which cooling water is introduced into the condenser itself rather than into the desuperheater.

〔Effect of the invention〕

As described above, the present invention opens the cooling water spray valve when the turbine bypass valve opens, detects the operation of the cooling water spray valve, and when the cooling water spray valve does not open normally, opens the turbine bypass valve. Since the bypass steam is introduced into the condenser by opening for a certain period of time, the steam can be processed until the output of the steam generator decreases, preventing the steam generator from shutting down and releasing the steam to the atmosphere. This has the effect of being able to avoid such situations. Furthermore, as a result, the condenser is not damaged, so it can be said that it is an extremely useful device in practice.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the turbine bypass system, Figure 2
6 to 6 are diagrams explaining one embodiment of the present invention, FIG. 2 is a system diagram showing an overview of the turbine bypass device, FIG. 3 is a block diagram showing the internal configuration of the control device, and FIG. 4 is a diagram showing an overview of the turbine bypass device. A circuit diagram showing a part of the control device in detail, Figure 5 is a diagram showing the relationship between the elapsed time after the load sheath is interrupted and the bypass steam flow rate, and Figure 6 is a diagram showing the relationship between the elapsed time after the load sheath is interrupted and the recovery. It is a diagram showing the relationship between the internal temperatures of the water container. 1... Main steam pipe, 6... Condenser, 7... Turbine bypass pipe, 8a, 8b, 8c... Turbine bypass valve, 10... Cooling water pipe, 11a, 11b,
11c...Cooling water spray valve, 20...Control device.

Claims (1)

[Claims] 1. A turbine bypass valve installed in a line that branches from the main steam pipe and connects to the condenser, and a pipe line that supplies cooling water to cool the steam introduced from the line to the condenser. a cooling water spray valve that opens the cooling water spray valve when the turbine bypass valve opens and detects the operation of the cooling water spray valve; A turbine bypass device includes a control device that fully closes a turbine bypass valve after a certain period of time.