Abstract
Accurate damage diagnosis is obtained using strain, typified by low-cycle fatigue damage and the like, representing a majority of the damage from age deterioration of a machine facility. A rotating electrical machine damage diagnostic system evaluates fatigue damage in a component of a rotating electrical machine based on a sensor. A strain range calculating section determines elastic strain and elastic stress in an evaluation area of the rotating electrical machine in terms of a quadratic function of a rotational speed of the rotating electrical machine detected by the sensor. Conversion of the elastic strain range and the elastic stress range into a total strain range is performed and a fatigue damage rate is calculated in the evaluation area of the rotating electrical machine from the total strain range resulting from the conversion. An integration section is provided for cumulating the fatigue damage rates to calculate a cumulated fatigue damage rate.
Claims
1. A rotating electrical machine damage diagnostic system which evaluates fatigue damage in a component of a rotating electrical machine based on a sensor signal representing detection by a sensor installed in the rotating electrical machine, comprising: a strain range calculating section for determining elastic strain and elastic stress in an evaluation area of the rotating electrical machine in terms of a quadratic function of a rotational speed of the rotating electrical machine detected by the sensor, counting frequency of occurrence of an elastic strain range and an elastic stress range in the evaluation area, and using Neuber's rule to perform conversion of the elastic strain range and the elastic stress range into a total strain range; a fatigue damage rate calculating section for calculating fatigue damage rates in the evaluation area of the rotating electrical machine from the total strain range resulting from the conversion; and an integration section for cumulating the fatigue damage rates to calculate a cumulated fatigue damage rate.
2. (canceled)
3. The rotating electrical machine damage diagnostic system according to claim 1, wherein the fatigue damage rate calculating section uses a fatigue strength diagram for strain control of materials in the evaluation area and modified Miner's rule to calculate the fatigue damage rates in the evaluation area of the rotating electrical machine.
4. The rotating electrical machine damage diagnostic system according to claim 1, wherein either the fatigue damage rate calculating section or the integration section gives an alarm when the fatigue damage rates or a cumulated value of the integration section exceeds a preset threshold value.
5. The rotating electrical machine damage diagnostic system according to claim 1, wherein a damage diagnostic apparatus including the strain range calculating section, the fatigue damage rate calculating section and the integration section is connected with an installation place of the rotating electrical machine via a communications line and performs remote diagnosis.
6. The rotating electrical machine damage diagnostic system according to claim 1, wherein the rotating electrical machine includes a rotating component and a non-rotating component, and wherein the evaluation area is an area in the rotating component.
7. The rotating electrical machine damage diagnostic system according to claim 6, wherein the evaluation area is a site or a component in the rotating component on which centrifugal force caused by rotation is exerted, the site or the component used as a member with a rotating copper member that is a conductor, or the evaluation area is an area of stress concentration in the rotating component on which centrifugal force caused by rotation is exerted.
8. A rotating electrical machine damage diagnostic method for evaluating fatigue damage in a component of a rotating electrical machine based on a sensor signal representing detection by a sensor installed in the rotating electrical machine, comprising the steps of: determining elastic strain and elastic stress in an evaluation area of the rotating electrical machine in terms of a quadratic function of a rotational speed of the rotating electrical machine detected by the sensor; counting frequency of occurrence of an elastic strain range and an elastic stress range in the evaluation area; using Neuber's rule to perform conversion of the elastic strain range and the elastic stress range into a total strain range; calculating fatigue damage rates in the evaluation area of the rotating electrical machine from the total strain range resulting from the conversion; and cumulating the fatigue damage rates to calculate a cumulated fatigue damage rate.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a diagram illustrating an example configuration of a damage diagnostic system applied to a wind power generation apparatus.
[0017] FIG. 2 is a block diagram illustrating the processing functionality of a diagnostic apparatus 11.
[0018] FIG. 3 is a diagram illustrating an example flow of the damage diagnosis processing in a processing unit 12.
[0019] FIG. 4 is a diagram illustrating an example of a time function N(t) of a rotational speed.
[0020] FIG. 5 is a diagram illustrating an example where a time function σ.sub.ei(t) of elastic stress of an evaluation area i is created from the time function N(t) of the rotational speed.
[0021] FIG. 6 is a diagram illustrating an example where a time function ε.sub.ei(t) of elastic strain of an evaluation area i is created from the time function N(t) of the rotational speed.
[0022] FIG. 7 is a diagram illustrating a relationship between the time function N(t) of the rotational speed, the elastic stress σei and the elastic strain εei.
[0023] FIG. 8 is a diagram illustrating the concept of the rainflow method.
[0024] FIG. 9 is an example table illustrating a relationship between the number of times and an elastic strain range determined by the rainflow method.
[0025] FIG. 10 is a diagram illustrating the conversion of an elastic strain range Δεei of a member i into a total strain range Δεi.
[0026] FIG. 11 is a diagram illustrating the conversion of a frequency distribution of an elastic strain range Δεei at each point (i) into a frequency distribution of a total strain range Δεi.
[0027] FIG. 12 is a table illustrating a relationship between a total strain range Δεi and the frequency thereof.
[0028] FIG. 13 is a diagram showing a fatigue lifetime curve L3 as the relationship between a strain range Δe and rupture lifetime (fracture repetition number N) and describing how to calculate a fatigue damage rate Dfi according to the linear damage rule in the evaluation area i.
[0029] FIG. 14 is a diagram illustrating the concept of the correction based on the modified Goodman diagram.
[0030] FIG. 15 is a diagram illustrating a relationship between a strain range and rupture lifetime in consideration of the effect of mean stress.
[0031] FIG. 16 is a diagram illustrating an example where a strain range and a stress range in an area i are determined by an elastoplastic finite element analysis.
[0032] FIG. 17 is a diagram illustrating the use of Neuber's rule for conversion into an elastic stress range Δσ.sub.eOi and an elastic strain range Δε.sub.eOi.
DESCRIPTION OF EMBODIMENTS
[0033] Embodiments of the present invention will be described with reference to the drawings.
Embodiment 1
[0034] Embodiment 1 according to the present invention will be described with reference to FIG. 1 to FIG. 15. A rotating electrical machine used in a wind power generation apparatus is described for an example in this embodiment although a damage diagnostic system according to the present invention is applicable to various types of rotating electrical machines.
[0035] FIG. 1 illustrates an example configuration of a damage diagnostic system applied to a wind power generation apparatus. In FIG. 1, the wind power generation apparatus has blades 3 rotatably supported by a nacelle 2 on top of a tower 1. The rotation of the blades 3 is transferred through a speedup gear 4 to a generator 5 as the rotating electrical machine in the nacelle 2 for generation of electric power. A plurality of wind power generation apparatuses 10 may form a windfarm 7. In the damage diagnostic system, a rotation counter 6 is installed in a rotating portion in the nacelle 2 of the wind power generation apparatus 10 to detect a rotational speed. Typically, the rotational speed and rotational speeds of the other wind power generation apparatuses 10 in the windfarm 7 are collected in an intra-farm control monitoring unit 8 and are then transmitted as signals from the control monitoring unit 8 to a remotely located diagnostic apparatus 11 through communication such as Internet 9 or the like. The diagnostic apparatus 11 comprises a processing unit 12 including a calculator, an input unit 14 such as a keyboard, and an output unit 13 such as a monitor screen. It is noted that the diagnostic apparatus 11 may be located next to the control monitoring unit 8 in the windfarm 7.
[0036] FIG. 2 is a block diagram illustrating the processing functionality of the diagnostic apparatus 11. The processing functionality includes a rotational speed input section 12a, a component strain range calculating section 12b, a fatigue damage rate calculating section 12c, an integration storage section 12d, and a display control section 12e.
[0037] In the present invention, the rotation counter 6 is installed in the rotating electrical machine 5 (generator) including a rotating component 5b and a non-rotating component 5a, and the diagnostic apparatus 11 detects a rotational speed and/or the like with the rotation counter 6, and incorporates the rotational speed and/or the like into the signal input section 12a of the remotely located diagnostic apparatus 11 through communication such as the Internet 9 and/or the like. Finally, the diagnostic apparatus 11 evaluates, for example, fatigue damage in the rotating component 5b based on the sensor signal and operation information of the rotating electrical machine. For this purpose, initially, the component strain range calculating section 12b calculates a strain range for a component using a quadratic function of a signal of the rotational speed sensor, the result of an elastic finite element analysis, a stress strain diagram of materials, and Neuber's rule.
[0038] Subsequently, the fatigue damage rate calculating section 12c calculates a fatigue damage rate in the rotating component 5b using a fatigue strength diagram for strain control of materials and modified Miner's rule. The integration storage section 12d performs a cumulative calculation of fatigue damage rates and stores a cumulated fatigue damage rate. The display control section 12e converts the analysis result into a user-understandable display format which is then displayed on the output unit 13 such as the monitor screen or the like. At this time, a user's instruction is also captured through the input unit 14 such as a keyboard or the like and reflected in arithmetic approach and display.
[0039] FIG. 3 is a diagram illustrating an example flow of damage diagnosis processing in the processing unit 12. Processing step signs (S1 to S9) representing the processing in the damage diagnosis processing are indicated on the right side of the flow diagram, and arithmetic processing portions (12a to 12e) for the respective functions illustrated in FIG. 2 are indicated on the left side. According to this, for example, the component strain range calculating section 12b is implemented by processing steps S1 to S5. It is noted that the processing order of the processing steps in FIG. 3 is not always the same as the processing order in the arithmetic processing portions of the respective functions in FIG. 2, and in the actual processing, repetitive processing and storing processing required in each repetitive processing, display processing, correction processing, and the like are executed as appropriate.
[0040] In the series of processing, initially, as the processing in the component strain range calculating section 12b, in a processing step S1, a signal of the rotation speed of a rotor which is the rotating component 5b of the rotating electrical machine 5 is acquired at a predetermined sampling frequency, and a time function N(t) of the rotational speed is created. In a wind turbine generator 5 and/or the like, a time function N(t) is created at a sampling frequency of the order of 1 Hz, which is then retained in an internal storage device in the control monitoring unit 8. The sampling frequency is defined as a frequency at which rotational speed variations in the rotating electrical machine may be described. The above-described processing in processing step S1 is performed in an input stage in the control monitoring unit 8. Then, the rotational speed signal is transmitted to and retained in a remotely located monitoring facility or the Cloud from the control monitoring unit 8 using the communication network 9.
[0041] FIG. 4 illustrates an example of the time function N(t) of a rotational speed. The example illustrates a collection for a time span of T days. In this example, it is assumed that in the first half of the time span of T days, the operation is conducted with rotational speeds varying but within a predetermined range, whereas in the second half, the phenomenon of momentary interruption is exhibited on occasion. In the following processing step S2, a function N.sup.2(t) of the square of the time function of the rotational speed is created and retained.
[0042] In processing step S3, a rotor elastic stress function σ.sub.ei(t) proportional to the function N.sup.2(t) of the square of the time function of the rotational speed is created and retained. The rotor elastic stress function σ.sub.ei(t) is created for each area of the rotor where damage is to be evaluated. At this time, the elastic stress function of the rotor area i may be expressed by Equation (1). It is noted that i is a suffix (=1, 2, 3, . . . ) denoting an area to be evaluated.
σ.sub.ei(t)=k.sub.si*{N(t)}.sup.2=k.sub.si*N2(t) (1)
[0043] Processing step S3 may be a step for calculating an elastic strain εei(t) represented by Equation (2). This is because the elastic stress σei(t) and the elastic strain εei(t) are in a proportional relationship having a proportionality constant which is a longitudinal elastic modulus of materials. In this case, i is also a suffix (=1, 2, 3, . . . ) denoting a rotor area to be evaluated.
ε.sub.ei(t)=k.sub.ei*{N(t)}.sup.2=k.sub.ei*N2(t) (2)
[0044] In Equations (1) and (2), modulus terms k.sub.si and k.sub.ei are set as follows. FIG. 7 is a characteristic curve where the horizontal axis indicates the rotational speed N including a rated rotational speed N.sub.0 and the vertical axis indicates the elastic stress σei and the elastic strain εei. The characteristics shown in FIG. 7 correspond to the quadric function shown in Equation (1), (2). With respect to the elastic stress σei0 and the elastic strain εei0 at the rated rotational speed N.sub.0, measured values at N(t) at a current time are the elastic stress σei(t) and the elastic strain εei (t). For setting the modulus terms k.sub.si and k.sub.ei in Equations (1) and (2), each of the elastic stress σ.sub.e0i and the elastic strain ε.sub.e0i in an evaluation area i at a rotational speed N.sub.0 is determined by material mechanics calculation and/or numerical calculations such as elastic finite element method and the like. Here, i is a suffix denoting an area to be evaluated. For the area i with residual stress, constant terms shown in Equations (3), (4) are incorporated in Equations (1), (2).
K.sub.si=σ.sub.si0/(N.sub.0).sup.2 (3)
K.sub.ei=ε.sub.ei0/(N.sub.0).sup.2 (4)
[0045] FIG. 5 illustrates an example where a time function σ.sub.ei(t) of elastic stress of an evaluation area i is created from the time function N(t) of the rotational speed in FIG. 4, Equation (1) and Equation (3). FIG. 6 illustrates an example where a time function ε.sub.ei(t) of elastic strain of an evaluation area i is created from the time function N(t) of the rotational speed in FIG. 4, Equation (2) and Equation (4).
[0046] FIG. 7 is a diagram illustrating a relationship between the time function N(t) of the rotational speed, the elastic stress σei and the elastic strain εei, expressed by Equation (1) to Equation (4). In FIG. 7, when the horizontal axis indicates the time function N(t) of the rotational speed and the vertical axes indicate the elastic stress σei and the elastic strain εei, the elastic stress σei and the elastic strain εei may be expressed as square-law characteristics of the time function N(t) of the rotational speed. When the rotational speed is equal to the rated rotational speed N.sub.0, the values of the elastic stress σei and the elastic strain εei are σei0 and the elastic strain εei0, respectively. When the rotational speed at a current time is N(t), the values of the elastic stress σei and the elastic strain εei are σei(t) and the elastic strain εei(t), respectively. According to the square-law characteristics, the higher the rotational speed is, the greater the increments of the elastic stress σei and the elastic strain εei are reflected.
[0047] In processing step S4 in FIG. 3, the frequency of occurrence of the stress range or strain range is determined from the time function σei(t) of the elastic stress or the time function εei(t) of the elastic strain, using a frequency counting method for the stress range or the strain range, typified by the rainflow method. Then, the elastic stress range Δσei or the elastic strain range Δεei of an area where damage is evaluated and the number of occurrences thereof are calculated and retained.
[0048] FIG. 8 is a diagram illustrating the concept of the rainflow method, in which the vertical axis indicates the elastic strain εei (or elastic stress σei) and the horizontal axis indicates time that advances from left to right. The strain is negative on the lower side and positive on the upper side. Heavy zigzag line L1 shows changes in strain over time. Thin line L2 shows “raindrops” flowing based on the rainflow method. FIG. 8 shows an example where the frequency of the elastic strain range Δεei is counted by the rainflow. For frequency count, an appropriate cycle-counting method may be used such as a range pair method, a range pair mean method, and the like. At this stage, a strain maximum value Δε.sub.p in a certain time range is also retained. This facilitates histogram display of the frequency distribution of the elastic strain range Δεei.
[0049] FIG. 9 illustrates an example of a relationship between the number of times and the elastic strain range determined by the rainflow method. For the elastic strain range Δεei, a maximum value Δε.sub.p of strain in a certain time range is divided by a certain number of partitions m, thereby the frequency distribution becoming uniform frequency distribution with equal intervals, which in turn facilitates the analysis of distribution of the frequency number of the strain range. This is the same as when the frequency distribution of the elastic stress range Δσei is determined.
[0050] FIG. 10 is a diagram illustrating the conversion of an elastic strain range Δεei of a member i into a total strain range ΔεI, in which the horizontal axis indicates a strain range Δε and the vertical axis indicates a stress range Δσ. In FIG. 10, a straight line as elastic calculation property L1 of the member i and saturation characteristics L2 showing a relationship between the stress range Δσ and the strain range Δε are also illustrated. As shown in FIG. 10, the elastic stress range Δσei and the elastic strain range Δεei of the member i determined by elastic calculation are in a proportional relationship, which can be positioned and indicated on the elastic calculation property L1.
[0051] On the other hand, Neuber's rule can be used to reflect a point on the elastic calculation property L1 as a point on the saturation characteristics L2 showing a relationship between the stress range Δσ and the strain range Δε. For information, the point shown by the elastic stress range and the elastic strain range for the member i determined in terms of elasticity has coordinates (Δσei, Δεei), and the point on the saturation characteristics determined based on Neuber's rule shown in Equation (5) has coordinates (Δσi, Δεi). The ΔσI and Δεi denoting a coordinate of the point on the saturation characteristics L2 correspond to the total stress range Δσi and the total strain range Δεi, respectively.
Δε.sub.ei.Math.Δσ.sub.ei=Δε.sub.i.Math.Δσ.sub.I, (5)
[0052] In processing step S5, using the relationship between the stress range Δσ and the strain range Δε of materials, the elastic stress range Δσei and the elastic strain range Δεei of the member i are converted into the total strain range Δεi, which is then retained. This is a method known as Neuber's rule. Specifically, the total strain range Δεi is determined from the relationship between the stress range Δσ and the strain range Δε and Equation (5). The relationship between the stress range Δσ and the strain range Δε varies depending on repeated stress and/or strain, and therefore the relationship may be changed according to the number of the repetitions.
[0053] Further, as a result of this processing, each point (Δeim) indicated in the frequency distribution of the elastic strain range Δεei in FIG. 9 may be converted into each point (Δim) indicated in the frequency distribution of the total strain range Δεi as illustrated in FIG. 11. Thus, as illustrated in FIG. 12, the relationship between the total strain range Δεi and the frequency thereof is determined. It is noted that FIG. 11 is a diagram illustrating the conversion of a frequency distribution of the elastic strain range Δεei at each point (i) into a frequency distribution of the total strain range Δεi, and FIG. 12 is a table illustrating a relationship between the total strain range Δεi and the frequency thereof.
[0054] The previous discussion describes the processing in the component strain range calculating section 12b in FIG. 2. Next, the processing in the fatigue damage rate calculating section 12c is performed in processing step S6. In processing step S6, a fatigue damage rate Dfi of the area i in question is calculated from the relationship between the total strain range Δe and the frequency (the number of times n) thereof created in processing step S5 and shown in FIG. 12 and from the fatigue test results of materials of the component under evaluation, i.e., the relationship between the total strain range Δe and rupture lifetime (fracture repetition number N) shown in FIG. 13. The fatigue damage rate Dfi may be calculated using, for example, linear damage rule typified by modified Miner's rule as shown in Equation (6) and/or various damage rules.
[00001]
[0055] It is noted that FIG. 13 is a diagram showing a fatigue lifetime curve L3 as a relationship between the strain range Δε and rupture lifetime (fracture repetition number N) and describing how to calculate a fatigue damage rate Dfi according to the linear damage rule for the evaluation area i. The characteristics are pre-obtained as the fatigue test results of materials of the component under evaluation. By referring to the characteristics L3, and by referring to a value of the total strain range Δe summarized in FIG. 12, fracture repetition number N at the time of the value is determined, so that Equation (6) may be executed using the fracture repetition number N and the number of times n in FIG. 12.
[0056] It is noted that, although the relationship between the strain range Δe and rupture lifetime (fracture repetition number N) as illustrated in FIG. 13 has been described as being pre-obtained using the fatigue test results in strain control, this relationship may be determined taking into account the influence of reduced lifetime by tensile hold, using fatigue test results in tensile hole.
[0057] Further, the relationship between the strain range and rupture lifetime may be used which uses the modified Goodman diagram taking into account a lifetime reduction by the effect of mean stress. FIG. 14 is a diagram illustrating the concept of the correction based on the modified Goodman diagram, in which the horizontal axis indicates mean stress and the vertical axis indicates amplitude of alternating stress. The modified Goodman diagram is used to determine: a stress amplitude σN when fracture repetition number N is reduced to one half by multiplying the strain range of fracture repetition number N by a longitudinal elastic modulus; and a stress amplitude σ′N when fracture repetition number N is reduced due to the effect of mean stress from yield stress σy, tensile strength σu of materials. Then, the stress amplitude σ′N when fracture repetition number N is reduced due to the effect of mean stress is divided by a longitudinal elastic modulus, and the resulting value is doubled to obtain a strain range ΔεN at fracture repetition number N.
[0058] FIG. 15 illustrates a relationship between the strain range and rupture lifetime taking into account the effect of mean stress. Using the relationship between the strain range (vertical axis) and the rupture lifetime (fracture repetition number, the horizontal axis) as illustrated in FIG. 15 may enable easy consideration of the effect of mean stress. The effect of mean stress causes a reduction in lifetime by the effect of mean stress as shown by the dotted line in FIG. 15. Here, the relationships between the strain range and the fracture repetition number taking into account the effect of mean stress have been discussed. For the relationships, the relationship between the strain range and the fracture repetition number by the fatigue test results taking into account the effect of hold stress and the environmental effects such as corrosion environments and/or the like may be used.
[0059] In the processing step S6, this is also retained and cumulated as the function of the integration storage section 12d in FIG. 2.
[0060] In processing step S7, as the function of the display control section 12e in FIG. 2, the fatigue damage rates Dfi in the area i obtained in processing step S6 and the integrated value ΣDfi thereof are displayed in appropriate form.
[0061] Further, in processing step S8, as the functions of the fatigue damage rate calculating section 12c or the integration section 12d and the display control section 12e in FIG. 2, an alarm is displayed when the fatigue damage rate Dfi (i=1, 2, 3, . . . , i is a component number) or the integrated value thereof exceeds a preset threshold Dthi (i=1, 2, 3, . . . , i is a component number). This enables maintenance such as repair, replacement and/or the like to be performed prior to fatigue failure of the member i.
[0062] In processing step S9, also, when there is a case where the member i is actually broken, Dfai at the time when the actual breakage is caused is calculated and retained in a database, and a threshold Dthi is calculated based on the Dfai and updated.
[0063] According to Embodiment 1, damage caused from the rotation of a rotating electrical machine component is predicted with precision, so that remaining lifetime may be evaluated with precision, thus increasing the reliability of the rotating electrical machine and achieving suitable maintenance.
Embodiment 2
[0064] In Embodiment 2, desirable monitoring target sites in the rotating electrical machine 5 are descried. One of the monitoring target sites is a site or component used as a member with a rotating copper member that is a conductor, in the rotating electrical machine 5 on which centrifugal force caused by the rotation is exerted. Specifically, the monitoring target sites include a coil, a coil end, a jumper wire, a conductor bar (bar), and an end ring. For such copper components, thermally treated materials with low yield stress are used for the purpose of improving the workability. As in the example of the bar and the end ring, the yield stress may be reduced by being exposed at high temperature of the order of 800° C. due to brazing.
[0065] According to the present invention, the lifetime is evaluated when such members whose yield stress tend to be reduced are repeatedly exposed to centrifugal force caused by rotation, and repair and/or replacement may be performed before damage occurs.
[0066] Further, as the other monitoring target sites, the application to an area that is a rotational part in the rotating electrical machine and a stress concentration part is desirable. Specifically, a slot into which an iron core of the bar is inserted, a cooling hole installed in an iron core, a hole for a mounting bolt of a fan, and the like are included in such an area.
[0067] The present invention encompasses applications to a stress concentration area that experiences centrifugal force caused by rotation of a rotating machine, such as a turbine including a gas turbine, a steam turbine, a hydraulic turbine, a wind turbine, a compressor, and the like.
Embodiment 3
[0068] FIG. 16 illustrates an example where a strain range and a stress range in an area i are obtained by an elastoplastic finite element analysis. The analysis was conducted to determine stress and strain in the area i using a rotational speed as a parameter.
[0069] It is found from FIG. 16 that when the rotational speed is increased repeatedly from zero to N.sub.0, the stress range is Δσ.sub.0i and the strain range is Δε.sub.0i. Using the stress range Δσ.sub.0i and the strain range Δε.sub.0i obtained by the elastoplastic stress analysis, the functions of the rotational speed, the elastic stress, and the elastic strain shown in Equation (1), Equation (2) may be created.
[0070] This corresponds to, as shown in FIG. 17, conversion of the stress range Δσ.sub.0i and the strain range Δε.sub.0i obtained in FIG. 16 into an elastic stress range Δσ.sub.e0i and an elastic strain range Δε.sub.e0i by using Neuber's rule.
[0071] Moduli k.sub.si, k.sub.ei may be determined using the converted elastic stress range Δσ.sub.e0i, the converted elastic strain range Δε.sub.e0i, and Equations (3), (4). If an apparatus or area where fatigue evaluation is performed has high non-linearity, the method in FIG. 16, FIG. 17 is effective. This is because the method calculates the elastoplastic behavior of a complicated structure using a finite element method.
LIST OF REFERENCE CHARACTERS
[0072] 1 . . . tower, [0073] 2 . . . nacelle, [0074] 3 . . . blade, [0075] 4 . . . speedup gear, [0076] 5 . . . generator 5, [0077] 5a . . . non-rotating component, [0078] 5b . . . rotating component, [0079] 6 . . . rotation counter, [0080] 7 . . . windfarm, [0081] 8 . . . intra-farm control monitoring unit, [0082] 9 . . . Internet, [0083] 10 . . . wind power generation apparatus, [0084] 11 . . . diagnostic apparatus, [0085] 12 . . . processing unit, [0086] 12a . . . signal input unit, [0087] 12b . . . component strain range calculating section, [0088] 12c . . . fatigue damage rate calculating section, [0089] 12d . . . integration storage section, [0090] 12e . . . display control section, [0091] 14 . . . input unit, [0092] 13 . . . output unit.
