JPS5977009A - How to protect nuclear turbines - Google Patents

Abstract

PURPOSE:To enable stress management to be made with a high degree of accuracy, by converting the steam pressure of steam turbine into a saturation temperature with the use of a stream table, and as well by estimating the temperatures of turbine main components in accordance with these temperatures to carry out the sress management of a trubine rotor. CONSTITUTION:Upon operation of a nuclear turbine the output signals of detectors 8, 26, 21 arranged in a high pressure first stage, for detecting a pessure P1, a temperature T1 and a humidity M1, respectively, are delivered to a steam temperature selector 22. Where M1>0, a temperature T10 estimated from the pressure P1 with the use of a steam table is set to the temperature after the high pressure first stage, and where M1=0, the temperature T1 is set to the temperature after the high pressure first stage. Then, from the above-mentioned temperature T1 or T10 and the pressure P1, the heat transfer coefficient of a rotor surface is calculated, and a thermal stress computing unit 10a computes a themal stress sigmaT in accordance with a temperature variation DELTAT computed by an operating unit 9. Further, an operating unit 13 combines the thermal stress sigmaT and a centrifugal stress computed by an operator 12, and in accordance with this composite stress, an adjusting valve 25 is controlled to be opened and closed by means of a rotor stress discriminator 16, a valve regulator 18, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for maintaining turbine acuity by managing stress in a steam turbine operated in a humid region, and in particular, the present invention relates to a method for maintaining turbine acuity by managing stress in a steam turbine operated in a humid region. The present invention relates to a turbine acceleration method suitable for stress sound control and management of the steam turbine rotor.

[Prior art]

Conventionally, rotor stress management due to changes in the load of a nuclear power turbine has generally been performed using a control chart as shown in FIG. 1, without directly measuring the deterioration of the rotor.

In the figure, the horizontal axis represents the amount of change in the load factor, and the vertical axis represents the minimum time required for the load change, and the four curves u shown
N, (b), e9. ), the smaller load factor before and after the load change is 0%, 10%, 20%, and 3.
This is a curve when it is 0%.

For example, a curve p-9 of 20% is used both when the load factor increases to 20 scallions and above and when the load factor decreases to 20%.

However, in recent years, in power plants using nuclear power turbines, there has been a demand for temporary isolated operation within the plant in the event of a failure in the outside line system.

In-plant isolated operation cuts off the load of the external line system and covers only the power consumption within the plant, and is a significantly lighter load operation than rated operation.

When entering the plant's isolated operation and restoring normal operation, a large thermal stress is applied to the turbine rotor due to the sudden load change, which reduces the life of the rotor. Furthermore, the frequency of normal startups and shutdowns as well as unplanned shutdowns and startups in nuclear power plants tends to increase, and these also generate thermal stress on the rotor and shorten its lifespan. Furthermore,
In the future, it is predicted that nuclear power plants will be required to operate at intermediate loads, which will also reduce the thermal stress on the rotor and shorten its lifespan. Under these circumstances, there is a growing need for stress management in nuclear turbine rotors.

FIG. 2 is a chart showing an example of temperature changes and stress changes in the turbine rotor when the load on the steam turbine changes. The upper half of this chart represents temperature, where 1 is the high pressure first stage steam temperature, 2 is the rotor surface temperature, and 3 is the rotor center hole temperature. The lower half of this diagram represents stress; 4 is the rotor center hole stress, 5 is the rotor surface stress, 6 is the rotor residual stress, and 7 is the compressive yield point. Now, we will explain the case of cold start, that is, the case where the rotor temperature is approximately equal to room temperature and high temperature steam flows in. First, with the inflow of steam, the rotor surface temperature increases by two degrees, indicated by a broken line, and a compressive stress 5Fi occurs on the rotor surface, also indicated by a broken line.

Here, the thermal stress is the highest in areas where stress is concentrated, such as the base of the disk, and the stress exceeds the minus yield point by 7 mm, causing plastic deformation noise in the compression direction. As a result, when the steady state is reached, a tensile residual stress of 6 hours is generated. On the other hand, in this process, a change in the rotor center hole temperature 3 shown by a dashed line causes a rotor center hole stress 4 in the opposite direction to the rotor surface shown by a solid line. When the turbine is stopped, the steam temperature 1 falls more rapidly than the rotor temperature. At this time, the rotor surface stress 5 (broken line) produces a tensile stress as indicated by the point (E), and the rotor center hole pressure 4 (solid line) produces a compressive stress as indicated by the point (E).

In order to deal with the occurrence of such thermal stress, conventional nuclear power turbines have adopted a method of monitoring rotor stress by securing the allowable load change period and time according to the curve shown in FIG.

In a conventional thermal power turbine, a stress management system as shown in FIG.
The detection signal of the steam temperature detector 26 is input to the thermal stress calculator 10 through the ΔT calculator 9, and in parallel with the above, the detection signal of the rotor rotation speed measuring device 11 is input to the centrifugal stress calculator 12.
input. The calculation result of the above thermal stress calculator 10,
The calculation result of the centrifugal stress calculation unit 12 is combined with the calculation result of the centrifugal stress calculation unit 13.
Based on the results, the creep wear calculator 15 and the rotor stress determiner 16 determine the situation and continue operating 17 or adjust the valve 18.
Decide on one.

When adjusting the valve, the adjustment valve 25 is controlled to open or close by the adjustment command signal 18a via the valve switch 19'.

If a nuclear power turbine is completely managed by the rotor stress monitoring method as described above, there are drawbacks such as failure.

One of the drawbacks is that when the monitoring system shown in Fig. 3 performs control based on the diagram shown in Fig. 1, the load change width and load fluctuation width shown in Fig. 1 cannot be controlled due to the wide range of operational changes in actual operation. In particular, it was not possible to manage stress in response to sudden load changes and rotational speed changes such as load shedding during an accident or isolated operation within the plant. In addition, due to the poor accuracy of rotor temperature control, it may take longer than necessary to respond to restarts and load increases after such accidents, or to load increases after isolated operation within the plant, or if the load increases under normal load. There was a risk of excessive stress due to the change curve.

Another disadvantage of traditional rotor stress monitoring methods is that nuclear turbines are often operated in humid steam, so the steam thermometer is also in the humid steam range, which means that there are no rapid load changes where thermal stress becomes a problem. Another problem is that the thermometer reading cannot fully follow changes in steam temperature, making it impossible to perform highly accurate stress management.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for protecting a nuclear power turbine, which can accurately determine the thermal stress of the rotor of a steam turbine that is operated mainly with wet steam, such as a nuclear power turbine, and can perform highly accurate stress management. .

[Summary of the invention]

In order to achieve the above object, the present invention detects the pressure in the humid region of a steam turbine such as a nuclear turbine that is operated in a humid region, and uses this pressure to determine the saturation temperature, which is uniquely determined by the amount of steam. From this, the total thermal stress of the steam turbine rotor is calculated and stress management of the rotor is performed. As a result, the thermal stress generated in the steam turbine can be determined with high accuracy, so accurate control can be performed so that the stress is always within a specified value, and the turbine can therefore be operated safely.

[Embodiments of the invention]

Next, an example of the present invention? 4 to 6 will be explained.

FIG. 4 is an i-s diagram of a nuclear turbine.

The reactor generated steam is located at point A, and at rated load the high pressure turbine inlet is located at point 8. By performing work within the high pressure turbine, the high pressure turbine outlet becomes a zero point. , the enthalpy (vertical axis) of the steam at point 0 increases due to the moisture separator,
Point D is at the inlet of the low pressure turbine. Then, work is done in the low pressure turbine, and at the outlet of the low pressure turbine it becomes a point E on the exhaust pressure line e.

In the case of partial load, the pressure at each stage decreases due to the decrease in the amount of steam at the steam turbine inlet.

Point E moves to points Bl, CI, DI, and E1, respectively.

Typically, the minimum load for nuclear turbines is 25% of rating.

In addition, during station isolated operation where the pressure of each stage of the steam turbine rapidly decreases, the station load is small at about 3%, but the reactor side requires about 40% of the feed water flow trt', so the high-pressure turbine bleed air amount is large. During station independent operation, the high pressure turbine inlet flow rate is relatively large compared to the station load, and the high pressure
The area after the stage is in a humid state. In other words, except when the rotational speed increases or decreases, the stage on the low-pressure side after the high-pressure first stage is in the humid region. Figure 5 shows the relationship between pressure and saturation temperature in humid steam. As is clear from this figure, when the stage is in the wet steam region, the steam temperature of the stage is uniquely determined from the steam table if the stage pressure is detected.

As mentioned above, in most of the load changes in nuclear turbines, the stages after the first high-pressure stage are operated in the wet steam region, so it is necessary to create stress control sounds specific to operating changes in wet steam. . A thermometer has a poor ability to track temperature changes in wet steam due to the humidity, so it cannot follow sudden changes like in the case of dry steam. In order to solve this problem, the method of the present invention detects all the pressures in the paragraphs, uniquely converts the pressure to saturation temperature as shown in Figure 5, and achieves high accuracy and tracking. Detects steam temperature with ease. However, if the steam is in the superheated range, it is not possible to convert pressure to temperature using the steam table, so if the steam is in the superheated range (for example, when the rotation speed is increasing during startup), monitor the steam temperature with a thermometer. Steam temperature can be monitored by confirming that the steam is in the humid area with a hygrometer when moving to the humid area and converting the detected pressure to temperature.

Therefore, under the above-mentioned conditions, the method of the present invention is applied to fully manage the rotor stress.The stage pressure detection positions are the high pressure first stage rear mouth, the high pressure first stage rear, and the high pressure exhaust part. , after the low-pressure first stage, after the first low-pressure stage, before and after the final low-pressure stage, etc.

A block diagram of a stress management system configured to carry out the method of the present invention based on the above basic idea is shown in FIG. 6. In this embodiment, all the objects were subjected to the high-pressure first immersion.

A stress management system configured for turbine monitoring according to the prior art is shown.The high-pressure first stage rear pressure detector 8, the ΔT calculator 9, and the rotor thermal stress calculator 101 rotation are given the same drawing reference numbers as in FIG. 3. Number measuring device 11. Rotor centrifugal stress calculator 12, composite stress calculator 13, operation time measuring device 14, creep wear calculator 15, rotor stress determiner 16, continuous operation 17. .

The valve regulator 18, the valve opener 19, the control valve 25, and the high pressure cylinder first stage temperature detector 26 are the same or similar components as in the prior art stress management system (FIG. 3).

A feature of the system configuration of an example of a stress management system (FIG. 6) configured to carry out the method of the present invention is the addition of a Q portion shown by a phantom line. That is, the signal output detected by the high-pressure first stage post-pressure detector 8 is input to the steam temperature selector 22 via the temperature converter 20. The above-mentioned temperature converter 20 stores the saturated steam pressure/temperature curve shown in FIG. 5, and is used to convert the input steam pressure into temperature. The above conversion can also be done using a steam table. In the present invention, the steam table includes the vapor pressure and temperature curves.

A signal output from a temperature detector 26 for detecting the steam temperature after the high-pressure first stage is also input to the steam temperature selector 22.

Furthermore, a humidity detector 21i for detecting the humidity of the steam after the high-pressure first stage is provided, and its signal output is inputted to the steam temperature selector 22.

The steam temperature selector 22 is configured to receive the signal output from the humidity/temperature detector 21 and operate as follows based on the signal output. That is, when the humidity is 9 degrees > 0, the temperature converter 20
A signal tΔT representing the steam temperature converted by is given to the calculator 9. Also, when humidity = O, the temperature sensor 26
A signal tone representing the steam temperature detected at .DELTA.T is given to the .DELTA.T calculator 9.

The steam temperature selector 22 described above has a structure that also has a comparison calculation function, and compares the converted steam temperature by the temperature converter 2o described above with the actual steam temperature measured by the temperature detector 26, and records the comparison result on the recorder 24. record it. Furthermore, the steam temperature selector 22 detects that the deviation between the temperature calculated by the temperature converter 2o and the actual temperature measured by the temperature detector 26 is The configuration is such that when a predetermined reference value is exceeded, the G alarm 23 is activated.

Next, an example in which the turbine protection method of the present invention is implemented using the above-mentioned management system shown in FIG. 6 will be described.

Pressure p after the high pressure first stage detected by the pressure detector 8, temperature detector 26 and humidity detector 21 installed in the high pressure first stage
H temperature T! and the humidity level M1 are determined and selected by the steam temperature selector 22. That is, the humidity level h4. > o, the pressure detected by the pressure detector is P1't - the temperature converted from the steam table TIO high pressure first stage, and the humidity M
When 1=0, the temperature Tlk detected by the temperature detector -C
l Select as the positive high voltage first stage rear.

The temperature after the first stage selected in this way T1° or TI
Then, the heat transfer coefficient of the rotor surface is calculated based on the first stage post-pressure P1, and the thermal stress σT? calculate. If the thermal stress σ↑ is calculated in this way, stress management of the rotor can be performed based on this. That is, it is possible to manage the stress of the rotor at each point in time so that it does not exceed the allowable stress, and to perform inspection and maintenance by calculating the degree of thermal fatigue of the rotor during long-term use.

In the above example, the rotor temperature was calculated based on the steam temperature converted by the steam table and stress management of the rotor was performed, but the turbine casing temperature was similarly calculated based on the steam temperature converted by the steam table. However, a rotor stress management method can also be determined based on changes in either or both of the calculated rotor temperature and the calculated casing temperature.

〔Effect of the invention〕

As explained above, the atomic catharp/protection method of the present invention detects the steam pressure sound of a steam turbine, converts the above pressure into a saturated steam temperature using a steam table, and based on this temperature, the rotor of the steam turbine or casing etc.
By calculating the temperature of the main components that come into contact with steam and managing the stress of the turbine rotor, we can accurately determine the thermal stress of the rotor of steam turbines that are mainly operated with wet steam and perform highly accurate stress management. Since the steam turbine can be maintained in service, it is particularly suitable for protecting nuclear power turbines.

As described in the above embodiment, the temperature of at least one of the turbine rotor and the turbine casing, which are the main constituent members of the turbine, can be calculated, and stress in the rotor can be managed based on this.

Regarding the above-mentioned embodiment, a more detailed stress management method will be described below.

The centrifugal stress σvk is calculated by the rotor centrifugal stress calculator 12 from the rotational speed determined by the rotational speed measuring device 11, and the resultant stress σF+σ↑t5 is calculated first and is stored in the operating time measuring device 14. Creep wear and tear calculator 15 from operation time
The rotor stress determiner 16 makes a comparison judgment using the pre-scheduled stress per cycle, which is calculated by 4 and takes into account the creep loss, as an allowable value, and if the resultant stress is less than the allowable value, a continuous operation instruction 17 is issued, and If the resultant stress exceeds the allowable value, the valve controller 1''8 adjusts the control valve 25'lir according to the increase or decrease in the rotational speed of the turbine and the increase or decrease in the load using the valve switch 19. In addition to measuring the stress and thermal stress, the rotor life wear and tear is integrated and stored based on the operating time measured by the operating time measuring device 14. In this way, the rotor life loss Jlt- is calculated, and the remaining service life is calculated. Since it can be estimated with high accuracy, inspection and maintenance can be carried out at appropriate times and the steam turbine can be completely maintained without waste.

As in the above example, if stress management is performed by finding the resultant force of the thermal stress calculated by applying the present invention and the centrifugal stress calculated from the rotation speed, stress management that accurately simulates the actual conditions becomes possible. .

Further, by integrating the calculated thermal stress with respect to the operating time, it is possible to appropriately and precisely manage the stress in consideration of the rotor's creep stress.

As mentioned above, in addition to monitoring long-term wear and tear, it is necessary to calculate the ratio of rotor stress to allowable stress at each point in time during operation, and to control this ratio so that it does not exceed 100%. This is also an effective protection measure, and if it is fully automatically controlled, stress management can be done unmanned.

In addition, as in the management system shown in Fig. 6, a 19 degree detector 21 is provided, and when the steam is wet steam, the converted steam temperature is used, and when the steam is dry steam, the actual steam temperature is used. If the stress is calculated using this method and stress management is performed, appropriate management can be performed even when the steam conditions become dry, such as when the rotational speed is increasing during startup of a nuclear steam turbine.

As explained in the management system diagram in Figure 6, the saturated steam temperature converted from the steam pressure and the steam temperature directly detected by the temperature detector are constant values when the steam in the steam turbine is wet steam. More deviation? A device will be installed to automatically record or alarm when this occurs, and if the above deviation exceeds a certain value, it will be determined that some kind of abnormality has occurred, and the pressure or temperature detector or calculator will be activated. Abnormal? Can be detected early.

In addition, as described in the above embodiment, the detection of steam pressure, the detection of steam temperature, and the detection of whether steam is wet steam or dry steam are performed at the high-pressure first stage inlet of the steam turbine, respectively. Rear, high pressure exhaust section, low pressure cylinder 1
Crotch inlet, after low pressure first stage, before low pressure final stage, after low pressure final stage,
and at least one of the intermediate stages,
The rotor temperature and stress can be calculated appropriately.

Furthermore, in the management system shown in FIG. 6, the humidity level detector 21 may be omitted and the steam humidity level may be determined by comparing a preset turbine output value with the actual operating output. Using this method, the humidity detector 21
This eliminates the need for a turbine protection system, making the configuration of the turbine protection system simple and inexpensive.

[Brief explanation of drawings]

Figure 1 is a control chart used for stress management in conventional nuclear turbines, and Figure 2 shows the state of rotor stress generation due to steam temperature changes. Figure 3 is a diagram of the management system used in a conventional thermal power turbine, Figure 4 is an i-s diagram of a nuclear turbine, and Figure 5 is a diagram showing the relationship between the pressure of wet steam and the saturation temperature. The steam diagram in FIG. 6 is an example of a diagram of a steam turbine management system configured to carry out the nuclear turbine protection method of the present invention. ■...High pressure first stage inlet temperature, 2...Rotor surface temperature, 3
...Rotor center hole temperature, 4...Rotor center hole stress,
5... Rotor surface stress, 6... Residual stress, 7...
Minus yield point, 8...High pressure first stage rear pressure detector, 9
...ΔT calculator, lO... Rotor thermal stress calculator, 1
DESCRIPTION OF SYMBOLS 1... Rotation speed measuring device, 12... Rotor centrifugal stress computing device, 13... Composite stress computing device, 14... Operating time measuring device, 15... Creep wear computing device, 16... Rotor stress determiner, F...Continuous operation, 18...Valve regulator 19...Valve switch, 20...Pressure? Converter for converting to saturation temperature, 21... Humidity detector, 22...
Steam temperature change device, 23...Alarm, 24...Recorder, 25...Adjustment valve, 26...Temperature detector after the first stage of high pressure cylinder. Agent Benkaushi Masami Akimoto I eye trap mark Tsubame 10 I Takashi Kaura 7 vs. Umetsu Kaya 2 eyes $5 Air pressure 0 Mun 6th eye 17 /≦ lσ

Claims (1)

[Claims] 1. Detect the steam pressure of the steam turbine, convert the above pressure into a saturation temperature using a steam jacket, calculate the temperature of the main components of the steam turbine based on this temperature, and adjust the temperature of the turbine rotor. A method of protecting a nuclear power turbine, the entire feature of which is stress management. 2 The temperature of the main components of the steam turbine is t
Claim 1, characterized in that the stress management of the rotor is performed by calculating the thermal stress of the rotor based on the calculated temperature of the main component, using at least one of the rotor temperature and the casing temperature. Methods for protecting nuclear power turbines as described in Section. 3. In addition to the thermal stress of the rotor mentioned above, is there centrifugal stress of the same rotor? Add to result in composite stress? 3. The method for protecting a nuclear power turbine according to claim 2, wherein all stress management of the rotor is performed based on the calculated resultant stress. 4. Rotor stress management based on the rotor thermal stress described above:
The atomic turbine maintenance system according to claim 2 or 3 is characterized in that the creep life of the rotor is calculated based on the thermal stress and the continuous operation time of the steam turbine. Waist method. 5. Any one of claims 1 to 4, characterized in that the rotor force management is automatically controlled so that the calculated rotor stress does not exceed an allowable stress level. A method for protecting a nuclear turbine according to one of the above. 6. Rotor stress management based on the above calculated thermal stress takes into consideration whether the steam in the steam turbine is wet steam or dry steam, and if it is wet steam, calculates the saturated steam calculated from the steam pressure. Perform rotor stress calculation based on temperature,
In the case of dry steam, the stress of the rotor is calculated based on the steam temperature directly detected by a temperature sensor. A method for protecting a nuclear turbine according to any one of the above. 7. If the saturated steam temperature converted from the steam pressure and the steam temperature directly detected by the temperature sensor differ by a certain value or more when the steam in the steam turbine is wet steam, an error occurs. 7. The nuclear turbine protection method according to claim 6, characterized in that it is determined that n has occurred. 8. The above-mentioned steam pressure detection, steam temperature detection, and detection of whether steam is wet steam or dry steam are carried out at the high-pressure first stage inlet, after the high-pressure first stage, high-pressure exhaust section, and low-pressure steam turbine, respectively. According to claim 6 or 7, the process is performed at at least one of the following: after the final stage, after the first low-pressure stage, before the final low-pressure stage, after the final low-pressure stage, and at an intermediate stage. Nuclear turbine protection method described. 9. Should the above-mentioned determination of whether the steam is wet steam or dry steam be made by comparing the preset turbine output value with the actual operating output? A nuclear power turbine protection method according to claim 6 or 7, characterized in that: