Steam turbine creep deformation evaluation device, method, and program

Abstract

To provide a technology for sequentially evaluating creep deformation behavior of a nozzle diaphragm in a steam turbine operated by a power generation plan accompanied by a large output fluctuation with excellent follow-up performance.SOLUTION: A creep deformation evaluation device 10 includes: an acquisition part 15 for acquiring the detection data x (x1,x2,,,xn) from each of sensors 21 (211,212,,,21n); a first calculation part 11 for calculating an optimal solution φ1 of an operation state amount of a nozzle diaphragm; a second calculation part 12 for calculating an approximate solution φ2 of the operation state amount in a shorter cycle than the optimal solution φ1; an update part 16 for updating an approximate expression f(x) for calculating an approximate solution φ2 based on an optimum solution φ1, an operation part 17 for operating the creep deformation speed V of a nozzle diaphragm; and an estimation part 18 for estimating the deformation amount D of the nozzle diaphragm from the creep deformation speed V.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a technique for evaluating creep deformation of a nozzle diaphragm in a steam turbine operated in a power generation plan involving large output fluctuations. [Background technology]

[0002] Until now, thermal power plants have mainly operated as base load plants, generating electricity continuously at rated power operation with high energy efficiency. However, in recent years, there has been a growing demand for thermal power plants to adjust to output fluctuations from renewable energy sources such as solar and wind power. As a result, thermal power plants have increasingly been operating at partial loads, which is less energy efficient, and the number of starts and stops has also increased.

[0003] It is known that damage and deterioration occur and accumulate in various parts of thermal power plants, such as steam turbines, control valves, and boilers, during operation, resulting in a decline in power generation performance and an increased risk of damage. One example of such damage is creep deformation of various parts and the resulting cracking. Creep deformation is a phenomenon in which, when metallic materials are used in a temperature environment at about half their melting point, they gradually undergo permanent deformation over time, even at low stress levels below the material's yield strength, eventually causing cracks and fracture of the metal.

[0004] Regarding creep deformation, one component that is considered important in the maintenance management of steam turbines is the nozzle diaphragm, which is exposed to steam at temperatures of over 500°C. The reason for this is that the gaps between the nozzle diaphragm and the adjacent moving blades and rotor are designed to be as narrow as possible to prevent steam leakage.

[0005] If the creep deformation of the nozzle diaphragm reaches a certain level, it will come into contact with adjacent rotating bodies such as the blades and the rotor that holds them, causing damage and scattering of parts, and resulting in an unplanned shutdown of the thermal power plant.

[0006] Therefore, in order to prevent contact between the nozzle diaphragm and the rotating body, maintenance management has traditionally been carried out, such as predicting the amount of creep deformation of the nozzle diaphragm from databases and operating data, and measuring the amount of deformation during regular inspections. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-303014 Summary of the Invention [Problem to be solved by the invention]

[0008] As mentioned above, modern thermal power plants undergo repeated start-stop and partial load operation to adjust output fluctuations. This makes it more difficult to assess the risk of damage due to creep deformation of the nozzle diaphragm. Conventional maintenance management of nozzle diaphragm creep deformation has been based on simulations assuming base load operation.

[0009] In baseload operation, plants are often operated near their rated output, where plant efficiency is at its maximum. In such cases, the temperatures, pressures, and other factors to which each nozzle diaphragm is exposed (hereinafter referred to as "operating state variables") are carefully evaluated and optimized during turbine design. Furthermore, because fluctuations in turbine output during operation are small, there is no need to consider fluctuations in operating state variables. For this reason, the amount of nozzle diaphragm deformation during baseload operation could be easily simulated using design information and operating history.

[0010] On the other hand, as partial load operation and start-stops increase, operation outside the design point also increases. Furthermore, there are more situations where the nozzle diaphragm is exposed to temperatures and pressures that were not anticipated during the design for long periods of time, and where the operating state variables fluctuate. For this reason, it was not possible to directly apply conventional databases and simulations regarding the creep deformation of nozzle diaphragms to modern thermal power plants, where start-stops are repeated many times a day and partial load operation is widely practiced.

[0011] The most common method for managing nozzle diaphragm creep deformation is to disassemble the steam turbine when the plant is shut down, remove the nozzle diaphragm, and directly measure its strain (deformation). However, since multiple nozzle diaphragms are located inside the steam turbine, removing them all requires disassembling the turbine. Furthermore, not only is it time-consuming to disassemble the individual nozzle diaphragms located between the rotor blades, but it also requires lifting the rotor out of the turbine to remove the lower half of the nozzle diaphragm.

[0012] Therefore, although this method is the most reliable because it can measure the amount of deformation most precisely, it has the problem that the measurement requires time (LT) and cost, and furthermore, the periodic inspection period is extended, which increases the power generation cost.In addition, methods such as measuring the gap between the nozzle diaphragm and rotor while the turbine is operating have also been considered, but it was difficult to set up such measuring equipment and to maintain high reliability for long periods of time in special environments.

[0013] On the other hand, studies have also been conducted to sequentially estimate the deformation of the nozzle diaphragm using operational state variables obtained from detection data from various sensors during turbine operation. Generally, calculating an appropriate operational state variable requires heat balance calculations at the turbine inlet, outlet, and inside. However, because the operational state variables obtained through heat balance calculations have many variable terms, it is difficult to determine them uniquely, and search calculations are required, resulting in a huge computational load. Therefore, sequential calculations while acquiring detection data during operation pose the problem of long calculation cycles and poor tracking of fluctuating operational state variables.

[0014] An embodiment of the present invention has been made in consideration of the above circumstances, and aims to provide a technology for sequentially evaluating, with excellent tracking capability, the creep deformation behavior of a nozzle diaphragm in a steam turbine operated under a power generation plan involving large output fluctuations. [Means for solving the problem]

[0015] A creep deformation evaluation device for a steam turbine according to an embodiment includes an acquisition unit that acquires detection data from each of a plurality of sensors installed in the steam turbine or its surrounding area, a first calculation unit that calculates an optimal solution for an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data, a second calculation unit that calculates an approximate solution for the operating state quantity based on the detection data at a shorter period than the optimal solution, an update unit that updates an approximation formula that calculates the approximate solution based on the optimal solution, a calculation unit that calculates a creep deformation rate of the nozzle diaphragm based on the approximate solution, and an estimation unit that estimates the deformation amount of the nozzle diaphragm from the creep deformation rate based on an operation plan of the steam turbine. [Effects of the Invention]

[0016] In an embodiment of the present invention, a technique is provided for sequentially evaluating, with excellent tracking capability, the creep deformation behavior of a nozzle diaphragm in a steam turbine operated in a power generation plan involving large output fluctuations. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram of a steam turbine creep deformation evaluation device according to a first embodiment of the present invention. [Figure 2] FIG. 6 is a block diagram of a steam turbine creep deformation evaluation device according to a second embodiment. [Figure 3] 4 is a graph showing the relationship between the equivalent stress acting on the nozzle diaphragm and the creep deformation rate. [Figure 4] 10 is an evaluation graph showing a future prediction of the amount of creep deformation of the nozzle diaphragm. [Figure 5] 2 is a flowchart showing steps of a method for evaluating creep deformation of a steam turbine according to an embodiment and an algorithm of a program for evaluating creep deformation of a steam turbine. DETAILED DESCRIPTION OF THE INVENTION

[0018] (First embodiment)

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a block diagram of a steam turbine creep deformation evaluation device 10A (10) (hereinafter simply referred to as "evaluation device 10A") according to a first embodiment of the present invention.

[0019] In this way, the evaluation device 10A includes a plurality of sensors 21 (211, 212, . . . 21) installed in the steam turbine 20 or its periphery. n ) from each of the detected data x(x1, x2...x n ), a first calculation unit 11 that calculates an optimal solution φ1 of an operating state quantity of a nozzle diaphragm in a steam turbine 20 based on the detection data x, a second calculation unit 12 that calculates an approximate solution φ2 of the operating state quantity based on the detection data x at a shorter period than the optimal solution φ1, an update unit 16 that updates an approximate equation f(x) that calculates the approximate solution φ2 based on the optimal solution φ1, a calculation unit 17 that calculates a creep deformation rate V of the nozzle diaphragm based on the approximate solution φ2, and an estimation unit 18 that estimates a deformation amount D of the nozzle diaphragm from the creep deformation rate V based on an operation plan 28 of the steam turbine 20.

[0020] The nozzle diaphragm (not shown) is a component installed between each stage of moving blades arranged in multiple rows in the steam turbine 20. The nozzle diaphragm has multiple nozzle plates (stationary blade plates) arranged circumferentially so as to face the moving blades arranged on the rotor surface.

[0021] Furthermore, the inner and outer peripheries of these nozzle plates are held in place by ring-shaped structures called inner and outer rings. The nozzle plate and the inner and outer rings are fixed together by welding or other methods, and are designed to be separable at the 0-degree and 180-degree positions. The nozzle diaphragm has this separable structure and is installed to sandwich the rotor from above and below, allowing it to be installed between each stage of the moving blades embedded in the rotor.

[0022] The nozzle diaphragm is designed to allow steam that has passed through the upstream rotor blades to pass between its nozzle plates, and has the function of directing the steam to the downstream rotor blades at an appropriate flow rate. Due to this function, a pressure difference occurs in the steam between the upstream and downstream sides of the nozzle diaphragm. Furthermore, because the nozzle diaphragm is used in high-temperature regions, the pressure difference with the outer ring side held in the turbine casing makes it prone to creep deformation, in which the inner ring side tilts toward the downstream side of the steam.

[0023] A plurality of sensors 21 are installed on the steam turbine 20 or its periphery, and output detection data x such as the temperature and pressure on the steam inlet and steam outlet sides of the steam turbine 20 and the temperature and pressure of extracted steam. In addition to these, the sensors 21 also output detection data x such as the temperature and pressure before and after a steam valve, and detection data x of the turbine casing and steam valve casing to which they are attached. The sensors 21 also include those installed on equipment (not shown) other than the steam turbine 20 in the power plant, such as the generator output, and output detection data x of those equipment.

[0024] The acquisition unit 15 sequentially acquires, at an appropriate sampling frequency, the detection data x that is continuously output from each of the multiple sensors 21. When the steam turbine 20 is started from a stopped state, it passes through a transient state and transitions to a steady state where the power generation output is constant. Furthermore, the steam turbine 20 may transition from one steady state to another or be stopped in response to a request for output adjustment. In such cases, it also passes through a transient state. Furthermore, the steady state after the transition can be broadly classified into rated operation, which is highly energy efficient, and partial load operation, which is less energy efficient.

[0025] As the operating conditions of the steam turbine 20 fluctuate frequently, the creep deformation rate of the nozzle diaphragm also fluctuates. Therefore, the detection data x acquired by the acquisition unit 15 can be said to be information that directly reflects the behavior of creep deformation in the nozzle diaphragm. Note that the detection data x is subjected to corrections such as averaging and noise removal in the acquisition unit 15 so that it can be appropriately processed in subsequent processes.

[0026] The first calculation unit 11 calculates the heat balance of the steam turbine 20 based on the detected data x. Here, the heat balance indicates the distribution state of thermal energy in each of the components (including the nozzle diaphragm) of the steam turbine 20.

[0027] That is, the first calculation unit 11 calculates and outputs an optimal solution φ1 of the operation state quantity based on the detected data x such as temperature, pressure, enthalpy, flow rate, etc., which are related to at least the nozzle diaphragm among these components. Note that the calculation method for the optimal solution φ1 of the operation state quantity of the nozzle diaphragm is not limited to being based on the heat balance of the steam turbine 20, and may be based on other calculation methods.

[0028] Specifically, the first calculation unit 11 calculates the heat balance at each stage of the steam turbine 20 by heat balance calculation based on the detected data x output by temperature sensors 21 and the like installed on the inlet and outlet sides of the steam turbine 20. However, the operating state variables calculated by these heat balance calculations have many variable terms, making them difficult to determine uniquely. This requires search calculations, but performing search calculations each time on the detected data that is constantly acquired during operation would result in an enormous computational load. For this reason, the calculation cycle for the optimal solution φ1 is long, and tracking performance decreases when the operating state variables fluctuate.

[0029] The second calculation unit 12 calculates the detected data x (x1, x2..., x n The approximate solution φ2 of the operating state quantity is calculated at a shorter period than the optimal solution φ1 by an approximate equation f(x) expressed by a polynomial with variables (f(x)=f(x) / f(x)). Note that the approximate equation f(x) applied in the second calculation unit 12 is not particularly limited to equation (1).

[0030] φ2=f(x)=f(x1,x2…,x n ) =A0+A1·x1+A2·x2+···+A n x n ···(1) A i : constant, x i :Detection data (i=1~n)

[0031] Incidentally, some of the detected data x that are the calculation basis for the optimal solution φ1 are difficult to detect sequentially, and so there are cases where an approximate solution φ2 of the operating state quantity is calculated by selecting limited detected data x. The second calculation unit 12 reads this approximate formula f(x) and calculates the approximate solution φ2 of the operating state quantity in a shorter period than the optimal solution φ1 without imposing a calculation load.

[0032] The update unit 16 compares the optimal solution φ1 and the approximate solution φ2 of the driving state quantity calculated from the detection data x acquired at the same timing, and updates the approximate equation f(x) so that the two match. In the approximate equation f(x) expressed by a polynomial such as the above equation (1), the coefficient A iIn addition, a threshold value may be used to determine whether the optimal solution φ1 and the approximate solution φ2 match, and if a match is determined at the time the optimal solution φ1 is calculated, the approximate formula f(x) may not be updated.

[0033] The calculation unit 17 calculates the creep deformation rate V of the nozzle diaphragm based on the design information K of the nozzle diaphragm and the approximate solution φ2 of its operating state quantity. Alternatively, a data set of the nozzle diaphragm's operating state quantity φ and the creep deformation rate V may be constructed, and the calculation unit 17 may output the corresponding creep deformation rate V for any input approximate solution φ2 of the operating state quantity. Note that the creep deformation rate V calculated here may only have a component in the direction along the rotation axis of the steam turbine 20.

[0034] The estimation unit 18 can estimate the deformation amount D of the nozzle diaphragm at the current time by integrating the creep deformation rate V output from the calculation unit 17 in real time. Furthermore, the estimation unit 18 can also estimate the future deformation amount D of the nozzle diaphragm from the operation time and creep deformation rate V estimated from an operation plan 28 of the steam turbine 20. Note that the operation plan 28 here refers to, for example, the equipment availability rate, average output, start / stop frequency, etc.

[0035] The display unit 19 (see FIG. 4) displays the creep deformation amount D of the nozzle diaphragm relative to the operating time t of the steam turbine 20. Here, the creep deformation amount D at the current time is displayed as "calculated result" based on the creep deformation rate V calculated in real time. Furthermore, the creep deformation amount D in the future is displayed as "future prediction (before correction)" based on the operation plan 28.

[0036] In this way, based on the creep deformation amount D in the "calculated results" at the current time and the "future prediction," it is possible to present an effective maintenance recommendation time for a nozzle diaphragm that is designed with a small clearance margin.

[0037] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Fig. 2. Fig. 2 is a block diagram of a steam turbine creep deformation evaluation device 10B (10) (hereinafter simply referred to as "evaluation device 10B") according to the second embodiment. In Fig. 2, parts having the same configuration or function as those in Fig. 1 are designated by the same reference numerals, and duplicated explanations will be omitted.

[0038] The evaluation device 10B of the second embodiment, like the evaluation device 10A of the first embodiment, includes an acquisition unit 15 for detection data x, a first calculation unit 11 for an optimal solution φ1 of the operating state quantity, a second calculation unit 12 for its approximate solution φ2, an update unit 16 for the approximate equation f(x), a calculation unit 17 for the creep deformation rate V, and an estimation unit 18 for the deformation amount D of the nozzle diaphragm.

[0039] In the evaluation device 10B of the second embodiment, the creep deformation rate V is calculated in the calculation unit 17 based on the equivalent stress σ of the nozzle diaphragm derived from the approximate solution φ2 of the operating state quantity. Furthermore, the evaluation device 10B includes a correction unit 29 that corrects the calculation formula G for the creep deformation rate V based on the actual measurement value 27 of the nozzle diaphragm and the creep deformation amount D estimated by the estimation unit 18.

[0040] Figure 3 is a graph showing the relationship between the equivalent stress σ acting on the nozzle diaphragm and the creep deformation rate V. This graph was created so that it can be universally applied to structures made of common materials, not just the nozzle diaphragm being evaluated.

[0041] The calculation unit 17 calculates the creep deformation rate V based on the equivalent stress σ of the nozzle diaphragm derived from the approximate solution φ2 of the operating state quantity. That is, the calculation unit 17 inputs the approximate solution φ2 of the operating state quantity of the nozzle diaphragm and design information K into the function formula g(φ, K) shown in the following equation (2), and calculates the equivalent stress σ generated in the nozzle diaphragm.

[0042] Furthermore, this equivalent stress σ is determined by the calculation formula G(φ,K,σ) shown in the following formula (3) using elasticity theory or elastic creep theory as a stress representative of the creep deformation amount based on the creep deformation behavior of the nozzle diaphragm.If it is difficult to determine the calculation formula G(φ,K,σ) for the equivalent stress σ using these theoretical formulas, it can also be obtained in advance using the finite element method, etc.

[0043] Equivalent stress σ=g(φ,K) ···(2) Creep deformation speed V=G(φ,K,σ)=A・σ B ···(3) Here, A and B are constants determined by φ and K. Assuming deformation of the nozzle diaphragm, similar to the function g for calculating the equivalent stress σ described above, these may be determined from the theory of elasticity or elastic creep theory, or may be determined using the finite element method, etc. The correction unit 29 updates the coefficients A and B in the calculation formula G such as the above formula (3).

[0044] In this embodiment, the calculation formula G for the creep deformation rate V is calculated using the power law of the equivalent stress σ, but other calculation formulas can also be applied. Since the shape of the nozzle diaphragm differs for each plant and each turbine stage, a calculation formula suitable for each nozzle can be applied. In all of these calculation formulas, the constants used in the formula are calculated from φ and K. Furthermore, although the second embodiment has been described assuming that the configuration of the first embodiment is provided, it is also possible to adopt a configuration in which the updating unit 16 is not provided and only one of the first calculation unit 11 and the second calculation unit 12 is provided.

[0045] Figure 4 is a creep deformation risk assessment graph showing the future prediction of the creep deformation amount D of the nozzle diaphragm. The function of the correction unit 29 corrects the calculation formula G so that the estimated value 26 of the creep deformation amount D matches the actual measured value 27 of the nozzle diaphragm, allowing for an accurate evaluation of the future prediction of creep deformation (after correction).

[0046] That is, the accuracy of future predictions can be improved by reflecting information on actual measurement values ​​27 obtained by visual inspections or the like performed when the steam turbine 20 is shut down. The deviation between the estimated value 26 of the creep deformation amount D output in advance from the estimating unit 18 and the actual measurement value 27 obtained by inspection can be quantified, and the future creep deformation prediction line can be corrected in accordance with the deviation, as shown by the arrow. Note that the actual measurement values ​​27 input to the correcting unit 29 are not limited to values ​​obtained by actual inspections, but may also include hypothetically set values.

[0047] Based on the flowchart in FIG. 5 (see FIG. 2 as needed), the steps of the steam turbine creep deformation evaluation method according to the embodiment and the algorithm of the steam turbine creep deformation evaluation program will be described.

[0048] First, an approximate equation f(x) for obtaining an approximate solution φ2 of the operational state quantity and an arithmetic equation G for calculating the creep deformation rate V are initialized (S11). Then, a plurality of sensors 21 (211, 212, ... 213) installed in the steam turbine 20 or its periphery are used. n ) from each of the detected data x(x1, x2...x n ) is obtained (S12).

[0049] Next, the approximate equation f(x) is called (S13), and an approximate solution φ2 of the operation state quantity is calculated based on the detected data x (S14). In parallel with these (S13, S14), the heat balance of the steam turbine 20 is calculated based on the detected data x (S15), and an optimal solution φ1 of the operation state quantity of the nozzle diaphragm is calculated (S16).

[0050] Then, based on the output optimal solution φ1 (S17, YES), the approximate formula f(x) is updated (S18). Note that since the calculation time for the optimal solution φ1 is longer than the calculation time for the approximate solution φ2, the update frequency of (S18) is lower than the call frequency of (S13).

[0051] Next, the calculation formula G is called (S19), and the creep deformation rate V of the nozzle diaphragm is calculated based on the approximate solution φ1 (S20). Furthermore, the deformation amount D of the nozzle diaphragm is estimated from this creep deformation rate V (S21). If a new actual measurement value 27 of the nozzle diaphragm (including a virtual value) has been acquired (S22, YES), the calculation formula G is modified (S23) so that the actual measurement value of the nozzle diaphragm and the estimated value match, and steps (S19) to (S21) are executed again.

[0052] If no new actual measurement values ​​of the nozzle diaphragm have been acquired (S22, NO), the estimated deformation amount D of the nozzle diaphragm is output (S24).Then, the flow of steps (S12) to (S24) is repeated until the operation of the turbine is completed (S25, NO, YES, END).

[0053] According to at least one embodiment of the steam turbine creep deformation evaluation device described above, by updating an approximate equation for an approximate solution of an operating state quantity with a short calculation period with an optimal solution with a long calculation period, it becomes possible to sequentially evaluate, with excellent tracking capability, the creep deformation behavior of a nozzle diaphragm in a steam turbine operated according to a power generation plan involving large output fluctuations.

[0054] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as the inventions described in the claims and their equivalents.

[0055] The steam turbine creep deformation evaluation device described above includes a control device with a highly integrated processor such as a dedicated chip, FPGA (Field Programmable Gate Array), GPU (Graphics Processing Unit), or CPU (Central Processing Unit), a storage device such as ROM (Read Only Memory) or RAM (Random Access Memory), an external storage device such as HDD (Hard Disk Drive) or SSD (Solid State Drive), a display device such as a monitor, an input device such as a mouse or keyboard, and a communication I / F, and can be realized with a hardware configuration using a normal computer. Therefore, the components of the steam turbine creep deformation evaluation device can be realized by a computer processor and can be operated by a steam turbine creep deformation evaluation program.

[0056] The creep deformation evaluation program for a steam turbine is provided by being pre-installed in a ROM or the like. Alternatively, the program may be provided by being stored in an installable or executable file format on a computer-readable storage medium such as a CD-ROM, CD-R, memory card, DVD, or flexible disk (FD).

[0057] The steam turbine creep deformation evaluation program according to this embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. The steam turbine creep deformation evaluation device may also be configured by combining separate modules that independently perform the functions of their constituent elements and are interconnected via a network or dedicated lines. [Explanation of symbols]

[0058] 10 (10A, 10B)... Creep deformation evaluation device, 11... First calculation unit, 12... Second calculation unit, 15... Acquisition unit, 16... Update unit, 17... Calculation unit, 18... Estimation unit, 19... Display unit, 20... Steam turbine, 21 (211, 212... 21 n )...sensor, 26...estimated value, 27...actual measurement value, 28...operation plan, 29...correction part, x(x1, x2...x n )...detection data, f...approximation formula, G...calculation formula, φ1...optimal solution of operating state quantity, φ2...approximate solution of operating state quantity, σ...equivalent stress, K...design information, V...creep deformation rate (deformation rate), D...creep deformation amount (deformation amount).

Claims

1. an acquisition unit that acquires detection data from each of a plurality of sensors installed in the steam turbine or its periphery; a first calculation unit that calculates an optimal solution for an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data; a second calculation unit that calculates an approximate solution of the operating state quantity at a shorter period than the optimal solution based on the detection data; an update unit that updates an approximation formula for calculating the approximate solution based on the optimal solution; a calculation unit that calculates a creep deformation rate of the nozzle diaphragm based on the approximate solution; an estimation unit that estimates a deformation amount of the nozzle diaphragm from the creep deformation rate based on an operation plan of the steam turbine.

2. 2. The steam turbine creep deformation evaluation device according to claim 1, The sensor is installed on at least one of a steam inlet side, an outlet side, and an extraction pipe of the steam turbine, The first calculation unit is a steam turbine creep deformation evaluation device that obtains the optimal solution from a calculation result of the heat balance of the steam turbine based on the detection data.

3. 3. The steam turbine creep deformation evaluation device according to claim 1, the approximation formula is expressed by a polynomial with the detection data as a variable, The update unit updates the coefficients of the approximation equation.

4. 3. The steam turbine creep deformation evaluation device according to claim 1, The creep deformation evaluation device for a steam turbine, wherein the creep deformation rate is calculated based on an equivalent stress of the nozzle diaphragm derived from the approximate solution of the operational state quantity.

5. 5. The steam turbine creep deformation evaluation device according to claim 4, The creep deformation evaluation device for a steam turbine includes a correction unit that corrects the calculation formula for the creep deformation rate based on the actual measurement value of the nozzle diaphragm and the estimated deformation amount.

6. acquiring detection data from each of a plurality of sensors installed on or around the steam turbine; calculating an optimal solution for an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data; calculating an approximate solution of the operational state quantity at a shorter period than the optimum solution based on the detection data; updating an approximation formula for calculating the approximate solution based on the optimal solution; calculating a creep deformation rate of the nozzle diaphragm based on the approximate solution; and estimating a deformation amount of the nozzle diaphragm from the creep deformation rate based on an operation plan of the steam turbine.

7. On the computer, acquiring detection data from each of a plurality of sensors installed on or around the steam turbine; calculating an optimal solution for an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data; calculating an approximate solution of the operational state quantity at a shorter period than the optimum solution based on the detection data; updating an approximation formula for calculating the approximate solution based on the optimal solution; calculating a creep deformation rate of the nozzle diaphragm based on the approximate solution; a creep deformation evaluation program for a steam turbine that executes a step of estimating a deformation amount of the nozzle diaphragm from the creep deformation rate based on an operation plan of the steam turbine.

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