JPS622124B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a steam turbine plant having a reheater in a nuclear power plant.

The steam produced in nuclear reactor plants for power generation is more
Generally, the temperature is low and near the saturation temperature. The steam generated in a nuclear reactor plant is led to a high-pressure turbine to convert its energy into power, and then is sometimes used to generate power in a low-pressure turbine; in this case, the high-pressure The steam discharged from the turbine has low temperature and pressure, and high humidity, so in addition to separating the moisture, a reheater that uses reactor generated steam as a heating source is sometimes used. This reheater heats the exhaust steam from the high-pressure turbine and guides it to the low-pressure turbine to obtain power, thereby increasing the driving power of the low-pressure turbine. Thermal efficiency of the area can be improved. In a prior art example, the control device for this reheater consists of an air-operated heating steam control valve and a motor-operated cam that transmits an air signal to the heating steam control valve. The driver operates these devices to control the heating steam control valve.

In addition, the examples of Japanese Patent Publication No. 53-47842 and Special Publication No. 55-21243 show methods for continuously and automatically controlling steam reheating work. The two examples each include a turbine temperature detector, a control system for controlling the amount of heated steam, a temperature reference signal source,
It includes a comparator, an integrator circuit, and a relational generator to control the reheat system according to one of a plurality of control modes. The important control parameters in these examples are the turbine inlet temperature, which includes temperature change rate control, maximum temperature control at the end and inlet of the low pressure turbine, and control to prevent excessive cooling of the low pressure turbine. is being carried out. However, the conventional method has a drawback in that it is not possible to monitor the thermal stress inside the reheater and the rotor of the low-pressure turbine, which actually requires monitoring. That is, the areas that require the most thermal stress monitoring are the inside of the reheater and the rotor of the low-pressure turbine. A tube is generally disposed inside the reheater, and heating steam passes through the inner surface of the tube to heat steam led from the high-pressure turbine exhaust flowing outside the tube. If a sudden temperature change is applied to the tube, excessive thermal stress may be generated between the tube and the supporting device due to deformation, or thermal stress may be generated in the tube itself. Compared to the stationary side of the turbine, the tube and tube support that are the internal structure of the reheater have better heat transfer with the steam.
The need for thermal stress monitoring is greater inside the reheater. Similarly, the turbine rotor has higher heat transfer than the turbine stationary body side, so
The temperature of the turbine rotor is more likely to change due to the inflowing steam, and the thermal stress is also higher.

The purpose of the present invention is to control the amount of heating steam supplied to the reheater so that the thermal stress inside the reheater and the low pressure turbine rotor is within an allowable range, and to An object of the present invention is to provide a control device for a steam turbine plant having a reheater that can protect both by avoiding cooling and overheating.

Next, a control device for a steam turbine plant having a reheater, which is an embodiment of the present invention, will be described.

FIG. 1 shows a steam turbine plant for nuclear power generation, which is the object of the present invention. In the figure, steam generated in a steam generator 1 passes through a main steam stop valve 2 and a steam control valve 3 to a high-pressure turbine 6.
guided by. The main steam stop valve 2 and the steam control valve 3 are
Based on the speed signal from the speed detector 4 of the steam turbine rotor, the control and drive device 5 opens and closes the rotor so as to reach the target speed. The steam that does work in the high-pressure turbine 6 and drives the high-pressure turbine has a lower pressure and temperature and an increased moisture content, so after separating the moisture in the moisture separator 7, the steam is recycled. It is guided to the heating device 8. The heat source of the reheater 8 uses steam generated by the steam generator 1, and branches from the upstream side of the main steam stop valve. Exchange heat with heated steam in reheater 8,
The steam whose temperature has increased is called reheated steam and is guided to the low pressure turbine 9. The high pressure turbine 6 and the low pressure turbine 9 are coupled to a generator 10 to drive the generator. Steam that performs work in the low-pressure turbine and generates driving power is led to a condenser 11, condensed into water, and led to a feedwater heater 12. The heated steam that has been heat exchanged in the reheater is also guided to this feed water heater.
Heat the water from the condenser. The heated water is supplied to the steam generator 1.

A heating steam stop valve 13 and a heating steam control valve 14 are installed in the heating steam piping, and are closed by a control and driving device 15.

FIG. 2 shows a control device for a steam turbine plant, which is an embodiment of the present invention. Heating steam stop valve 13
is opened and closed by the stop valve drive and valve position determiner 16, and the opening and closing are either fully open or fully closed. Opening and closing are instructed by the stop valve control device 17. The reheat steam control valve 14 is opened and closed by a control valve drive and valve position determiner 18, and the opening and closing may be not only fully open/closed but also an intermediate opening, and the opening is instructed by the control valve controller 19. be done. Control valve control device 1
9 calculates the thermal stress inside the low pressure turbine rotor and reheater based on the detected values from various detectors,
The opening degree of the heating steam control valve 14 is set to be optimal, and the opening degree is instructed. The detected values of the various detectors are sent to the control valve control device 19 via the detected value repeater 20.

The detector repeater 20 transmits signals.
Furthermore, when multiple detectors are placed at the same detection point, the detector repeater 20 can select a high value, select a low value, or exclude a detected value that shows an excessive change in detected value during measurement. This increases the reliability of detected values.

Additionally, protection detectors are provided, which send detected values to the stop valve controller 17 via a protection detector repeater 37 . The protective detector repeater 37 performs signal transmission. The signal is sent to the stop valve controller 17, and when the value exceeds or falls below a predetermined set value for equipment protection, the signal is sent to the stop valve drive and valve position determiner 16 to fully close the stop valve. send a signal. At this time, a plurality of detectors may be placed at the same detection point, and a stop valve fully closed signal may be output when a majority of the plurality of detection values exceeds or falls below a set value. Alternatively, a stop valve fully closed signal may be output when two detected values among the plurality of detected values exceed or fall below a set value.

As described above, by making the control system from the detector to the control valve and the protection system from the detector to the stop valve independent of each other, equipment can be safely protected even when the control system malfunctions.

Also, when the detected value by the detector exceeds or falls below the preset reset value,
When the full close signal is canceled and a reset signal is sent from the central controller 38 to the stop valve controller 17, the stop valve is fully opened to prepare for startup.

The manual controller 34 sends valve opening/closing signals to the stop valve controller 17 and the control valve controller 19 by manual operation at the driver's discretion. As a result, in an emergency, the valve can be opened and closed at the driver's discretion, and the stop valve and control valve can be tested for opening and closing.

Next, optimal control by the reheat steam control valve 14 will be described. The low-pressure turbine thermal stress and the reheater internal thermal stress are calculated and controlled so that they fall within allowable values.

The low-pressure turbine thermal stress can be calculated by taking the rotor stress, which can be obtained as follows.

σ _S =Eα/1−ν(T _avg −T _o ) σ _B =Eα/1−ν(T _avg −T _B ) However, σ _S : Rotor surface stress σ _B : Rotor center hole stress E : Rotor material elasticity Coefficient α: Rotor material linear expansion coefficient ν: Poisson's ratio T _o : Rotor surface temperature T _B : Rotor center hole temperature T _avg : Rotor volume average temperature T _avg = 1/γ _o ² - γ _p ² ∫〓 ⁿ 〓 _p T・r・dr However, T: Temperature at rotor radius r γ _o : Rotor surface radius γ _p : Rotor bore radius The rotor temperature T is determined by the following formula.

∂T/∂t=a(∂ ² T/∂γ ² +∂T/γ∂γ) t: Time a: Temperature conductivity of rotor material The boundary condition is K(T _S −T _o )=λ∂T/ ∂r T _S : Steam temperature on the rotor surface λ: Thermal conductivity of the rotor material K: Heat transfer coefficient between the rotor surface and the steam The steam leaving the reheater is led to the low pressure turbine, so the steam exits the reheater. The temperature is equal to the steam temperature at the low pressure turbine inlet rotor surface. Therefore, the initial temperature of the turbine rotor before steam flows into the low pressure turbine is detected by the low pressure turbine internal metal temperature detector 32.
As the temperature detected in , the rotor surface stress and center hole stress are calculated moment by moment using the above calculation formula from the reheater outlet temperature from the heater. At the same time, the amount of change ΔT ₃₀ in steam temperature at the outlet of the reheater that can be allowed until after an appropriate time Δt in the future is determined from the calculated stress value and the allowable stress value. The reheater outlet steam temperature can be controlled by adjusting the heated steam temperature and the amount of heated steam entering the reheater. Furthermore, when the reheater inlet steam temperature or the reheater inlet steam amount is changing, the heating steam amount is corrected in consideration of the rate of change. Since the reheater inlet steam amount is proportional to the pressure after the first stage of the high pressure turbine, it is calculated from the measured value of the pressure after the first stage of the high pressure turbine. In this way, the range in which the amount of heating steam can be increased or decreased until after Δt is determined.

Similarly, with regard to the thermal stress inside the reheater, the momentary thermal stress is calculated to determine the range in which the amount of heating steam can be increased or decreased until after Δt so that the thermal stress falls within the allowable value.

Compare the range in which the amount of heating steam can be increased or decreased, determined from the thermal stress of the low-pressure turbine rotor, and the range in which the amount of heating steam can be increased or decreased, determined from the internal thermal stress of the reheater, and determine the amount to increase or decrease the amount of heating steam within the overlapping area. .

After the heating steam increase/decrease is determined, the opening degree increase/decrease of the heating steam control valve is determined based on the heating steam conditions, and the heating steam control valve is opened/closed.

FIG. 3 shows arithmetic blocks for the above-mentioned control. This calculation function is possessed by the control valve controller.

The reheater inlet steam pressure (detector 27) and the reheater inlet steam temperature (detector 28) are proportional to the turbine load as long as the main steam condition is constant. Since the turbine load is proportional to the pressure after the first stage of the turbine (detector 33), it is sufficient to implement the present invention even if the other two are calculated from the pressure after the first stage of the turbine.

Since the heating steam is taken from the main steam line, its steam conditions are the same as the main steam conditions. Even when the main steam conditions change, the main steam temperature often changes because it is approximately the saturation temperature and the main steam pressure changes. That is, this is a case where the main steam temperature is approximately saturated and the reactor thermal output is increased so as to gradually increase the main steam pressure. In such a case,
It is sufficient to carry out the present invention even if the pressure of the heated steam (detector 21) is used and the temperature of the heated steam (detector 22) is controlled using a calculated value without measuring it.

There are cases where the turbine is controlled by making a certain relationship between the main steam condition and the turbine load turbine rotation speed. That is, this is a case where the turbine rotational speed is increased while increasing the main steam pressure, and after reaching the rated pressure, the turbine load is started. In this case, the same effect can be obtained even if the main steam conditions are determined inversely from the turbine rotational speed (detector 4) and the turbine load. Therefore, detectors 21 and 22 may be omitted.

As mentioned above, the turbine load is proportional to the pressure after the first stage of the high pressure turbine (detector 33), so the turbine load is determined from the pressure after the first stage of the high pressure turbine, but this can be determined by detecting the generator output to determine the turbine load. are also sufficient for practicing the invention.

It is sufficient to carry out the present invention even if it is considered that the steam after the heating steam control valve undergoes isenthalpic expansion after being throttled by the control valve. Therefore, the heating steam conditions and the pressure after the heating steam control valve (detector 2
The temperature after the heating steam control valve may be calculated and obtained from 3).

The steam in the steam turbine plant of a nuclear power plant contains moisture, and by removing the moisture using a dehumidifier inside the turbine or an external dehumidifier, the steam conditions can be brought to near saturation. and to increase turbine efficiency. If a dehumidifier is not installed inside the turbine, or if the humidity is expected to be high even if a dehumidifier is installed, or if the humidity of the main steam is high, check the temperature at each steam temperature measurement point to improve control accuracy. I am trying to measure the humidity. By measuring the humidity and determining the enthalpy, the temperature after the heating steam control valve described above can be calculated with high accuracy, and the heat transfer coefficient between the steam and the turbine rotor can be calculated with high accuracy.

Reheater internal metal temperature detector 3 used for control
1 and the low-pressure turbine internal metal temperature detector 32, or both, and the respective initial detection values are calculated in a state where there is steam flow just before the stop. Based on the metal temperature, the cooling during the turbine stop time is considered. The present invention can also be implemented by calculating.

According to the present invention, a control device for a steam turbine plant having a reheater is capable of controlling the amount of heated steam supplied to the reheater so that the thermal stress inside the reheater and the low-pressure turbine rotor is within an allowable range. This has the effect that it can be realized.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing a steam turbine plant of a nuclear power plant, which is the subject of the present invention, and Fig. 2 is an overall system diagram showing a control device for a steam turbine plant having a reheater, which is an embodiment of the present invention. , FIG. 3 is a control flow diagram showing detailed contents of the control device of the present invention. 1...Steam generator, 2...Main steam stop valve, 3...
... Steam control valve, 4 ... Speed detector, 5 ... Control and drive device, 6 ... High pressure turbine, 7 ... Moisture separator, 8 ... Reheater, 9 ... Low pressure turbine, 10
... Generator, 11 ... Condenser, 12 ... Feed water heater, 13 ... Heating steam stop valve, 14 ... Heating steam control valve, 15 ... Control and drive device, 16 ... Stop valve drive and Valve position determiner, 17...Stop valve controller, 18...Control valve drive and valve position determiner, 19
... Control valve controller, 20 ... Detector repeater, 21
... Heating steam pressure detector, 22 ... Heating steam temperature detector, 23 ... Heating steam control valve rear pressure detector,
24...Steam temperature detector after heating steam control valve, 25
... Heating steam reheater outlet pressure detector, 26 ... Heating steam reheater outlet temperature detector, 27 ... Reheater inlet steam pressure detector, 28 ... Reheater inlet steam temperature detector, 29 ...Reheater outlet steam pressure detector, 3
0... Reheater outlet steam temperature detector, 31... Reheater internal metal temperature detector, 32... Low pressure turbine internal metal temperature detector, 33... High pressure turbine first stage rear pressure detector, 34... Manual Controller, 35...
Reheater internal metal temperature sensor (for protection), 36...
...Low pressure turbine internal metal temperature detector (for protection), 37...Protection detector repeater, 38...Central control unit.

Claims (1)

[Claims] 1. In a steam turbine plant equipped with a reheater installed in a nuclear power plant, a control valve is installed in the heating steam piping that supplies heating steam to the reheater, and a control valve is installed in the heating steam piping that supplies heating steam to the reheater, and Temperature detectors are installed, and a calculation device is installed that calculates the thermal stress of the low-pressure turbine rotor and the stress inside the reheater from these temperature detectors. 1. A control device for a steam turbine plant having a reheater, characterized in that the control device comprises a valve control device that operates the control valve so that the control valve is within a certain value.