Steam turbine damage assessment device, method, and program

Abstract

To provide a technique to precisely simulate and evaluate creep deformation behavior of a nozzle diaphragm in a steam turbine used in a power generation plan associated with large output fluctuation.SOLUTION: A damage evaluation device 10 comprises: an acquisition section 11 which acquires detection data 31 from each of a plurality of sensors 21 installed on a steam turbine 20; a calculation section 15 which calculates an operation state amount φ of a nozzle diaphragm in the steam turbine 20 on the basis of the detection data 31; an operation section 16 which performs an operation of a creep deformation speed V of the nozzle diaphragm on the basis of the operation state amount φ; and an estimation section 17 which estimates a deformation amount D of the nozzle diaphragm from the creep deformation speed V on the basis of a future operation plan 26 of the steam turbine 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a damage assessment technique for 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 baseload plants, generating electricity continuously at rated power operation with high energy efficiency. However, in recent years, there has been an increasing demand for thermal power plants to adjust output fluctuations of renewable energy power plants such as solar and wind power. As a result, thermal power plants are increasingly operating at partial loads, which is less energy efficient, and the number of starts and stops has also increased.

[0003] Incidentally, it is known that damage and deterioration occur and accumulate in various parts of the main components of thermal power plants, such as steam turbines, control valves, and boilers, during operation, resulting in a decline in power generation performance and an increase in the risk of damage. One example of such damage is creep deformation of various parts and the associated crack generation. Creep deformation is a phenomenon in which, when a metallic material is used in a temperature environment of about half its melting point, a gradual permanent deformation occurs over time even at a low stress below the yield strength of the metallic material, eventually causing cracks and the metal to break.

[0004] Regarding creep deformation, one component that is considered important in the maintenance of steam turbines is the nozzle diaphragm, which is exposed to steam at 500°C or higher. The reason for this is that the gap between the nozzle diaphragm and the adjacent moving blades and rotor is 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 blades or the rotor that holds them, causing damage and scattering of parts, 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 performed, such as predicting the amount of creep deformation of the nozzle diaphragm from a database or operating data, and measuring the amount of deformation during regular inspections. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2003-303014 A Summary of the Invention [Problem to be solved by the invention]

[0008] As mentioned above, recent thermal power plants are repeatedly started and stopped and operated at partial loads to adjust output fluctuations. This makes it more difficult to evaluate the risk of damage due to creep deformation of the nozzle diaphragm. Conventional maintenance management of the creep deformation of the nozzle diaphragm was based on simulations assuming base load operation.

[0009] In baseload operation, plants are often operated near the rated output where plant efficiency is at its maximum. In such cases, the temperature, pressure, etc. to which each nozzle diaphragm is exposed (hereinafter referred to as "operating state quantities") are precisely evaluated and optimized at the time of turbine design. Furthermore, because there is little fluctuation in turbine output during operation, there is no need to consider fluctuations in the operating state quantities. For this reason, the amount of deformation of the nozzle diaphragm during baseload operation could be easily simulated from the design information and operating history.

[0010] On the other hand, as partial load operation and start / stop frequency 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 assumed during the design for long periods of time, and where the operating state quantities fluctuate. For this reason, it was not possible to directly apply the conventional database and simulations on the creep deformation of the nozzle diaphragm to the modern thermal power plants, where start / stop cycles are repeated many times a day and partial load operation is widely practiced.

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

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

[0013] An embodiment of the present invention has been made in consideration of the above circumstances, and aims to provide a technology for precisely evaluating, through simulation, the creep deformation behavior of a nozzle diaphragm in a steam turbine operated in a power generation plan involving large output fluctuations. [Means for solving the problem]

[0014] A damage assessment 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 on the steam turbine or its surrounding area, a calculation unit that calculates an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data, a calculation unit that calculates a creep deformation rate of the nozzle diaphragm based on the operating state quantity, and an estimation unit that estimates the deformation amount of the nozzle diaphragm from the creep deformation rate based on a future operating plan for the steam turbine. Effect of the Invention

[0015] In an embodiment of the present invention, a technique is provided for precisely evaluating, by simulation, the creep deformation behavior of a nozzle diaphragm in a steam turbine operated in a power generation plan involving large output fluctuations. [Brief description of the drawings]

[0016] [Figure 1] 1 is a block diagram of a damage assessment device for a steam turbine according to a first embodiment of the present invention. [Diagram 2] FIG. 6 is a block diagram of a damage assessment device for a steam turbine according to a second embodiment. [Diagram 3] 5 is a graph showing the relationship between the equivalent stress acting on a nozzle diaphragm and the creep deformation rate. [Figure 4] A damage risk assessment table showing the occurrence frequency of nozzle diaphragm deformation versus steam turbine operating time. [Diagram 5] 13 is a damage risk assessment graph showing a future prediction of the amount of creep deformation of the nozzle diaphragm. [Figure 6] 3 is a flowchart showing steps of a damage assessment method for a steam turbine according to an embodiment, and an algorithm of a damage assessment program for a steam turbine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] (First embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a block diagram of a damage assessment device 10A (10) for a steam turbine according to a first embodiment of the present invention. As described above, the damage assessment device 10A for a steam turbine 20 includes an acquisition unit 11 that acquires detection data 31 from each of a plurality of sensors 21 installed on the steam turbine 20 or its periphery, a calculation unit 15 that calculates an operation state variable φ of a nozzle diaphragm in the steam turbine 20 based on the detection data 31, a calculation unit 16 that calculates a creep deformation speed V of the nozzle diaphragm based on the operation state variable φ, and an estimation unit 17 that estimates a deformation amount D of the nozzle diaphragm from the creep deformation speed V based on a future operation plan 26 for the steam turbine 20.

[0018] The nozzle diaphragm (not shown) is a component that is 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.

[0019] Furthermore, the inner and outer circumferences of these nozzle plates are held by ring-shaped structures called the inner and outer rings. The nozzle plate, inner and outer rings are fixed by welding or other methods, and have a structure that allows them to be separated at the 0 degree and 180 degree positions. The nozzle diaphragm has such a separation structure, and is installed so that it sandwiches the rotor from above and below, making it possible to install it between each stage of the moving blades embedded in the rotor.

[0020] The nozzle diaphragm is designed so that steam that has passed through the upstream moving blades passes between the nozzle plates, and has the function of directing the steam to the downstream moving 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 a high temperature range, the pressure difference with the outer ring side held by the turbine casing easily causes creep deformation in which the inner ring side tilts toward the downstream steam side.

[0021] A plurality of sensors 21 are installed on the steam turbine 20 or its periphery, and output detection data 31 such as the temperature and pressure on the steam inlet and steam outlet sides of the steam turbine 20 and the extraction temperature and pressure. In addition to this, the sensors 21 also output detection data 31 such as the temperature and pressure before and after a steam valve, and detection data 31 on 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 31 on those equipment as well.

[0022] The acquisition unit 11 sequentially acquires, at an appropriate sampling frequency, the detection data 31 that is continuously output from each of the multiple sensors 21 from time to time. When the steam turbine 20 is started from a stopped state, it passes through a transient state and transitions to a steady state in which the power generation output becomes constant. Furthermore, the steam turbine 20 may transition from one steady state to another steady state or be stopped in response to a request for output adjustment. In such cases, the steam turbine also passes through a transient state. Furthermore, the steady state after the transition is also broadly classified into rated operation, which is highly energy efficient, and partial load operation, which is less energy efficient.

[0023] As the operating condition of the steam turbine 20 fluctuates frequently in this way, the creep deformation rate of the nozzle diaphragm also fluctuates. Therefore, the detection data 31 acquired by the acquisition unit 11 can be said to be information that directly reflects the behavior of the creep deformation of the nozzle diaphragm. Then, the detection data 31 is subjected to correction such as averaging and noise removal in the correction unit 12 so that it can be appropriately processed in the subsequent process.

[0024] The calculation unit 15 calculates the heat balance of the steam turbine 20 based on these detection data 31. 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.

[0025] That is, the calculation unit 15 calculates and outputs the operation state quantity φ, such as temperature, pressure, enthalpy, flow rate, etc., related to at least the nozzle diaphragm among these components, based on the detection data 31. Note that the calculation method of the operation state quantity φ 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.

[0026] Specifically, the calculation unit 15 obtains the heat balance at each stage of the steam turbine 20 by a balance calculation based on the detection data 31 output by the temperature sensors 21 and the like installed on the inlet and outlet sides of the steam turbine 20. However, depending on the type and number of nozzle diaphragms constituting the steam turbine 20, it may be difficult to use all of the detection data 31 acquired sequentially for the heat balance calculation process.

[0027] In such a case, the heat balance of the evaluation portion (nozzle diaphragm) is stored in a database (not shown) in correspondence with the assumed detection data 31. Then, a calculation process may be performed in which the operating state quantity φ corresponding to the detection data 31 acquired by the acquisition unit 11 is sequentially output from this database.

[0028] The calculation unit 16 calculates the creep deformation speed V of the nozzle diaphragm based on the operation state variable φ of the nozzle diaphragm obtained from the calculation result of this heat balance and the design information K of the nozzle diaphragm. Alternatively, a data set of the operation state variable φ of the nozzle diaphragm and the creep deformation speed V may be constructed, and the calculation unit 16 may output the corresponding creep deformation speed V for any input operation state variable φ. Note that the creep deformation speed V calculated here may only have a directional component along the rotation shaft of the steam turbine 20.

[0029] The estimation unit 17 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 16 in real time. Furthermore, the estimation unit 17 can also estimate the future deformation amount D of the nozzle diaphragm from the operation time estimated from a future operation plan 26 of the steam turbine 20 and the creep deformation rate V. Note that the operation plan 26 here is, for example, the equipment availability rate, average output, start / stop frequency, etc.

[0030] The display unit 18 (see FIG. 5) displays the creep deformation amount D of the nozzle diaphragm versus the operation 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" based on the operation plan 26.

[0031] 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 timing for a nozzle diaphragm that is designed with a small clearance margin.

[0032] 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 damage assessment device 10B (10) according to the second embodiment. In Fig. 2, parts having the same configuration or function as Fig. 1 are indicated by the same reference numerals, and duplicated explanations will be omitted.

[0033] The damage assessment device 10B of the second embodiment, like the damage assessment device 10A of the first embodiment, has the functions of an acquisition unit 11 for detection data 31, a heat balance calculation unit 15 for outputting the operating state quantity φ, a calculation unit 16 for the creep deformation rate V, and an estimation unit 17 for the deformation amount D.

[0034] The creep deformation rate V in the damage assessment device 10B of the second embodiment is calculated based on the detection data 31 acquired in real time as in the first embodiment, as well as on historical data 32 obtained by accumulating detection data 31 acquired in the past.

[0035] This history data 32 is formed by correcting the detection data 31 acquired in real time by the correction unit 12 and then storing the data in the storage unit 14. Therefore, this history data 32 is data obtained by accumulating the entire operating period from the start of operation of the steam turbine 20.

[0036] The historical data 32 can also be externally input from the data input unit 13. This is to accommodate cases where the damage assessment device 10B is operated on an existing steam turbine 20 that has been in operation for some time. Based on such historical data 32 as well, a more reliable creep deformation rate V can be calculated.

[0037] 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 limited to the nozzle diaphragm being evaluated.

[0038] A calculation unit 16 (FIG. 2) of the damage assessment device 10B calculates the creep deformation rate V based on the equivalent stress σ of the nozzle diaphragm derived from the operating state quantity φ. That is, this calculation unit 16 inputs the operating state quantity φ of the nozzle diaphragm and design information K to an arithmetic expression 25, and calculates the equivalent stress σ generated in the nozzle diaphragm.

[0039] The equivalent stress σ is calculated based on the creep deformation behavior of the nozzle diaphragm and is calculated using elasticity theory or elastic creep theory as the stress that represents the amount of creep deformation. If it is difficult to determine the equivalent stress σ using these theoretical formulas, it is also possible to obtain an approximate formula for the stress parameter that represents the amount of creep deformation in advance using the finite element method, etc. The function G that represents the creep deformation rate V can also be defined with a range for the equivalent stress σ, such as a probability distribution29, by taking into account the variation in materials such as creep strength.

[0040] Equivalent stress σ=f(φ,K) Creep deformation speed V=G(φ,K,σ)=A・σ B Here, A and B are constants determined by φ and K. Assuming the deformation of the nozzle diaphragm, they may be determined from the theory of elasticity or elastic creep theory, as in the case of the calculation formula f for calculating the equivalent stress σ described above, or they may be determined using the finite element method, etc.

[0041] In this embodiment, the creep deformation rate V is calculated using the power law of the equivalent stress σ, but other prediction formulas can also be used. Since the shape of the nozzle diaphragm differs for each plant and each turbine stage, a prediction formula suitable for each nozzle can be applied. In all of these prediction formulas, the constants used in the formula are calculated from φ and K.

[0042] 4 is an assessment table of the damage risk showing the occurrence frequency of the deformation amount D of the nozzle diaphragm with respect to the operating time of the steam turbine 20. This assessment table shows the occurrence frequency in three stages, "High," "Middle," and "Low," but there is no particular limitation on this display method.

[0043] Damage assessment device 10B (Fig. 2) is equipped with assessment unit 28 which assesses the risk of damage to the nozzle diaphragm based on creep deformation amount D estimated by estimation unit 17. By expressing creep deformation rate V with respect to equivalent stress σ as probability distribution 29 (Fig. 3), it is possible to assess the risk of damage to the nozzle diaphragm in terms of occurrence frequency based on deformation amount D and operating time t, as shown in Fig. 4. Each threshold value (A, B, a, b) shown in Fig. 4 can be determined in advance based on design information K such as the dimensions, material, etc. of the nozzle diaphragm.

[0044] The deformation amount D of the nozzle diaphragm is calculated from the real-time detection data 31 of the sensor 21. However, this raises concerns that a prediction error due to variations in the material strength of the nozzle diaphragm may occur in the deformation amount D. This error increases in proportion to the increase in operation time. For this reason, as shown in the damage risk assessment table (Fig. 4), an appropriate risk assessment can be realized by assessing the damage risk using two parameters, the deformation amount D and the operation time t.

[0045] In the second embodiment, a method has been described in which the evaluation unit 28 displays an evaluation table (FIG. 4) of damage risk based on a matrix of two parameters on the display unit 18. However, the damage risk evaluation by the evaluation unit 28 is not necessarily limited to this method. For example, the equipment availability rate, average operating temperature, number of starts and stops, etc. may be used as parameters, and it is also possible to calculate the damage probability using a probabilistic method rather than uniquely determining the risk based on the matrix and parameters.

[0046] Figure 5 is a damage risk assessment graph showing a future prediction of the creep deformation amount D of the nozzle diaphragm. In this way, the damage risk can be assessed by correcting the calculated estimated value 24 of the creep deformation amount D with the actual measured value 27 of the nozzle diaphragm.

[0047] That is, the accuracy of future prediction can be improved by reflecting information on actual measurement values ​​27 such as visual inspections performed when the steam turbine 20 is stopped. The deviation between the estimated value 24 of the creep deformation amount D output in advance from the estimating unit 17 and the actual measurement value 27 by inspection is quantified, and the future damage prediction line is corrected according to the deviation, as shown by the arrow.

[0048] Based on the flowchart in Fig. 6 (see Fig. 2 as appropriate), the steps of the method for evaluating damage to a steam turbine according to the embodiment and the algorithm of the program for evaluating damage to a steam turbine will be described. First, detection data 31 is acquired from each of a plurality of sensors 21 installed on the steam turbine 20 or its periphery (S11). Next, the heat balance of the steam turbine 20 is calculated based on the detection data 31 (S12).

[0049] Then, based on the operating state quantity φ of the nozzle diaphragm obtained from the calculation result of this heat balance (S13), the creep deformation speed V of the nozzle diaphragm is calculated (S14). Note that this creep deformation speed V is also calculated based on history data 32 obtained by integrating past detection data 31 as necessary.

[0050] The calculated creep deformation rate V is integrated to display the real-time creep deformation amount D of the nozzle diaphragm (S15). Furthermore, based on a future operation plan 26 for the steam turbine 20 (S16), the future creep deformation amount D of the nozzle diaphragm is estimated from the past creep deformation rate V and displayed (S17). Then, based on this future creep deformation amount D, the risk of damage to the nozzle diaphragm is evaluated (S18), and the recommended maintenance timing for the nozzle diaphragm is presented (END).

[0051] According to at least one of the embodiments of the steam turbine damage assessment device described above, the creep deformation rate of the nozzle diaphragm is calculated in real time based on the heat balance of the steam turbine calculated from the detection data of multiple installed sensors, making it possible to precisely evaluate through simulation the creep deformation behavior of the nozzle diaphragm in a steam turbine operated according to a power generation plan involving large output fluctuations.

[0052] Although some 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 in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention.

[0053] The steam turbine damage assessment device described above includes a control device with a highly integrated processor such as a dedicated chip, an FPGA (Field Programmable Gate Array), a GPU (Graphics Processing Unit), or a CPU (Central Processing Unit), a storage device such as a ROM (Read Only Memory) or a RAM (Random Access Memory), an external storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive), a display device such as a display, an input device such as a mouse or a 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 damage assessment device can also be realized by a computer processor and can be operated by a steam turbine damage assessment program.

[0054] The steam turbine damage assessment program is provided by being pre-installed in a ROM, etc. Alternatively, the program may be provided by being stored in a computer-readable storage medium, such as a CD-ROM, a CD-R, a memory card, a DVD, or a flexible disk (FD), in the form of an installable or executable file.

[0055] The steam turbine damage assessment program according to the present embodiment may be stored in a computer connected to a network such as the Internet and provided by downloading it via the network. The steam turbine damage assessment device may also be configured by combining separate modules that independently perform the functions of the components and are connected to each other via a network or dedicated lines. [Explanation of symbols]

[0056] 10 (10A, 10B)...damage assessment device, 11...acquisition unit, 12...correction unit, 13...data input unit, 14...storage unit, 15...calculation unit, 16...operation unit, 17...estimation unit, 18...display unit, 20...steam turbine, 21...sensor, 24...estimated value, 25...operation formula, 26...operation plan, 27...actual measured value, 28...evaluation unit, 29...probability distribution, 31...detection data, 32...historical data, φ...operational 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 in the vicinity thereof; a calculation unit for calculating an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data; a calculation unit that calculates a creep deformation speed of the nozzle diaphragm based on the operating state quantity; an estimation unit that estimates a deformation amount of the nozzle diaphragm from the creep deformation rate based on a future operation plan of the steam turbine, 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 calculation unit obtains the operating state quantity from a calculation result of a heat balance of the steam turbine based on the detection data.

2. In the damage assessment device for a steam turbine according to claim 1, The creep deformation rate is calculated based on historical data obtained by integrating the past detection data.

3. The damage assessment device for a steam turbine according to claim 2, The damage assessment device for a steam turbine, wherein the history data is input from an external source.

4. The damage assessment device for a steam turbine according to any one of claims 1 to 3, A damage assessment device for a steam turbine, wherein the creep deformation rate is calculated based on an equivalent stress of the nozzle diaphragm derived from the operational state quantity.

5. The damage assessment device for a steam turbine according to any one of claims 1 to 4, A damage assessment device for a steam turbine comprising an assessment unit that assesses a risk of damage to the nozzle diaphragm based on the estimated deformation amount.

6. An acquisition unit that acquires detection data from each of a plurality of sensors installed in the steam turbine or its surroundings; a calculation unit for calculating an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data; a calculation unit that calculates a creep deformation speed of the nozzle diaphragm based on the operating state quantity; an estimation unit that estimates a deformation amount of the nozzle diaphragm from the creep deformation rate based on a future operation plan of the steam turbine; an evaluation unit that evaluates a risk of damage to the nozzle diaphragm based on the estimated deformation amount, the creep deformation rate is calculated based on an equivalent stress of the nozzle diaphragm derived from the operating state quantity, A damage assessment device for a steam turbine that evaluates the damage risk of the nozzle diaphragm by the occurrence frequency of the amount of deformation by expressing the creep deformation rate as a probability distribution with respect to the equivalent stress.

7. The damage assessment device for a steam turbine according to claim 5 or claim 6, The evaluation unit is a steam turbine damage evaluation device that evaluates the damage risk based on two parameters, including the operating time of the steam turbine.

8. An acquisition unit that acquires detection data from each of a plurality of sensors installed on the steam turbine or its surroundings; a calculation unit for calculating an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data; a calculation unit that calculates a creep deformation speed of the nozzle diaphragm based on the operating state quantity; an estimation unit that estimates a deformation amount of the nozzle diaphragm from the creep deformation rate based on a future operation plan of the steam turbine; an evaluation unit that evaluates a risk of damage to the nozzle diaphragm based on the estimated deformation amount, The evaluation unit evaluates the damage risk based on two parameters including an operating time of the steam turbine, The damage risk is evaluated by correcting an estimated value of the deformation amount based on a calculation with an actual measured value of the nozzle diaphragm.

9. acquiring detection data from each of a plurality of sensors installed on or around the steam turbine; calculating an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data; calculating a creep deformation speed of the nozzle diaphragm based on the operating state quantity; and estimating a deformation amount of the nozzle diaphragm from the creep deformation rate based on a future operation plan of the steam turbine, 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 method for evaluating damage to a steam turbine, wherein the calculation obtains the operational state quantity from a calculation result of a heat balance of the steam turbine based on the detection data.

10. On the computer, acquiring detection data from each of a plurality of sensors installed in the steam turbine or in its periphery; calculating an operating state quantity of a nozzle diaphragm in the steam turbine based on the detection data; calculating a creep deformation speed of the nozzle diaphragm based on the operating state quantity; estimating a deformation amount of the nozzle diaphragm from the creep deformation rate based on a future operation plan of the steam turbine; 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 calculation includes a damage assessment program for a steam turbine that obtains the operating state quantity from a calculation result of a heat balance of the steam turbine based on the detection data.

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