Method for evaluating aging state of main insulation of motor stator bar through analytic hierarchy process

Abstract

The invention provides a method for evaluating the main insulation aging state of a motor stator bar through an analytic hierarchy process, and relates to the field of evaluation of the main insulation aging state of the motor stator bar. Obtaining a judgment matrix; calculating a consistency proportion based on the consistency index of the judgment matrix and the corresponding average random consistency index; if the consistency proportion is smaller than a threshold value, obtaining a corresponding weight vector according to a feature vector corresponding to the maximum feature value in the current judgment matrix; obtaining and normalizing parameter values for evaluating the aging state of the main insulation of the motor stator bar to obtain a characteristic parameter matrix; and multiplying the characteristic parameter matrix by the weight vector to obtain a main insulation aging score of the motor stator bar, thereby obtaining a main insulation aging state of the motor stator bar, and providing data for life estimation of the motor.

Description

Technical Field

[0001] The invention relates to the field of motor stator wire bar main insulation aging state assessment, and in particular to a method for assessing the motor stator wire bar main insulation aging state through a hierarchy analysis method. Background Art

[0002] Large generators are key equipment for modern power production, and their operational reliability directly affects the safety and stability of the power grid. Since the insulation state of large generators is a key factor in ensuring the long-term safe operation of generators, domestic and foreign scholars have conducted some investigations and statistics on accidents caused by the insulation state of large motors. The results show that among the many insulation system accidents of large motors, more than half of the failures are caused by the aging and partial discharge of the stator bar main insulation. The higher the rated voltage level of the generator and the larger the single-unit capacity, the easier it is for the main insulation to age, and with the increase in the operating years, the probability of main insulation failure also increases significantly. The main insulation of large generator stators is expensive, complex in structure, difficult to maintain, and cannot be replaced blindly. Therefore, it is of great significance to accurately diagnose the aging state of motor insulation.

[0003] Domestic and foreign scholars have conducted a variety of research on the aging status detection of the main insulation of large generators, which can be mainly divided into the following four categories: evaluation based on electrical non-destructive parameters, evaluation based on non-electrical parameters, evaluation based on operation history, and evaluation based on artificial intelligence technology.

[0004] (1) Based on electrical non-destructive parameter detection methods. Due to the complex microstructure of the main insulation of the motor, it is difficult to establish an accurate mathematical model to analyze the aging characteristics of the insulation. Therefore, domestic and foreign researchers generally use the residual breakdown voltage to measure the aging state of the insulation. However, the residual breakdown voltage test will cause irreversible damage to the insulation. Therefore, the focus of the electrical non-destructive parameter detection method is to find the aging characteristic quantity that is highly correlated with the residual breakdown voltage.

[0005] (2) Non-electrical parameter detection methods mainly include X-ray diffraction, acoustic detection, infrared spectroscopy, etc. These technologies can provide a certain degree of understanding of the microstructural changes of insulating materials, but whether these methods can be used for actual insulation status diagnosis remains to be verified.

[0006] (3) The main detection methods based on operation history include NY image method and D image diagnostic method. This method can be used to infer the changing relationship between insulation electrical parameters and operating years. However, a large number of approximate calculations are performed during the analysis, which is quite different from the actual operation of the insulation and can only be used for rough life estimation.

[0007] For example, in the Chinese patent literature, the publication number is CN109375072B, the publication date is January 26, 2021, and the name is a method for evaluating the insulation aging state of stator wire rods by space charge method. It simulates the influence of electrical aging, thermal aging and mechanical aging on the stator wire rods during the operation of the unit. The comprehensive aging test device is composed of a simulated iron core (1) and a vibration platform (2). During the electrical aging test, the wire rods are placed in the simulated iron core for horizontal vibration, and the aging temperature is between 80°C and 90°C. The reference wire rod (3) is subjected to 1.6UN, 2.0UN, 2.5UN, and 3.0UN (UN is the rated voltage of the wire rod, unit kV) electrical aging tests, and the relationship between voltage and breakdown time is plotted to calculate the service life of the reference wire rod; the test wire rod (4) is subjected to a 1.0UN electrical aging test, and space charge detection and breakdown tests are performed at 0h, 500h, 1000h, 1500h, 2000h, and 2500h, respectively. The remaining service life of the test rod is evaluated based on the functional relationship between the total amount of space charge at different aging times, the space charge threshold field strength and the residual breakdown voltage. However, the prior art with publication number CN109375072B still has defects. During the breakdown test, the insulation is irreversibly damaged, which in turn affects the aging of the test rod. Summary of the invention

[0008] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides a method for evaluating the aging status of the main insulation of the stator wire bar of a motor through a hierarchical analysis method. Without damaging the insulation performance of the stator wire bar, the aging status of the main insulation of the stator wire bar of the motor can be accurately obtained to provide data for the life estimation of the motor.

[0009] The present invention is achieved through the following technical solutions:

[0010] The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the hierarchical analysis method is characterized by comprising the following steps:

[0011] S1. Select factors for evaluating the aging state of the main insulation of the stator bar of the motor, i.e., evaluation parameters;

[0012] S2. Indicating the importance of each factor in the criterion layer by using the pairwise comparison method and the 1-9 point scale method, obtaining the scales of the two factors according to their importance, and using the matrix formed by the scales as the judgment matrix;

[0013] S3, calculating the consistency index of the judgment matrix, and obtaining the corresponding average random consistency index, and calculating the consistency ratio based on the consistency index of the judgment matrix and the corresponding average random consistency index;

[0014] S4, if the consistency ratio is less than the preset threshold, proceed to step S5; otherwise, return to step S2 to re-acquire the scale in the judgment matrix;

[0015] S5. Obtain the corresponding eigenvector according to the maximum eigenvalue in the current judgment matrix, and obtain the corresponding weight vector W;

[0016] S6, obtaining parameter values ​​for evaluating the aging state of the main insulation of the motor stator bar and normalizing them to obtain a characteristic parameter matrix P;

[0017] S7. Multiply the characteristic parameter matrix P by the weight vector W to obtain the motor stator wire bar main insulation aging score S, and perform an evaluation to obtain the motor stator wire bar main insulation aging status.

[0018] Furthermore, in step S2, the scales of the two factors are obtained according to their importance, and the matrix formed by the scales is used as the judgment matrix M:

[0019]

[0020] Where m uv It is the ratio of the influence degree of the uth factor affecting the aging of the main insulation of the motor stator bar to the vth factor affecting the aging of the main insulation of the motor stator bar in the judgment matrix M. If the scale of factor u / factor v is m uv , then the scale of factor v / factor u is 1 / m uv , where u=1, 2, 3...n, v=1, 2, 3...n.

[0021] Furthermore, the step S3 includes the following steps:

[0022] S3.1. Obtain the maximum eigenvalue λ in the judgment matrix max And order n, calculate the consistency index CI of the judgment matrix according to formula 1:

[0023]

[0024] S3.2, then search the average random consistency index RI table to obtain the RI value corresponding to the order n, where the order n is not greater than 9;

[0025] S3.3. Calculate the consistency ratio CR according to formula 2:

[0026]

[0027] Furthermore, in step S4, the preset threshold is 0.1.

[0028] Furthermore, step S5 is as follows:

[0029] S5.1. Obtain the eigenvector corresponding to the maximum eigenvalue in the current judgment matrix T = [t1 t2 … t J ]; where the value of J is equal to the number of evaluation parameters;

[0030] S5.2. Calculate the j-th element value w of the weight vector according to formula 3 j ; where t j is the jth element in the eigenvector corresponding to the maximum eigenvalue in the current judgment matrix,

[0031]

[0032] S5.3, obtain the corresponding weight vector W according to the element value obtained in step S5.2,

[0033] W=[w1 w2 … w j ].

[0034] Furthermore, the specific steps of establishing the characteristic parameter matrix in step S6 are as follows:

[0035] S6.1. Obtaining the initial value of each evaluation parameter for the aging degree of the main insulation of the motor stator bar and the current value of the evaluation parameter at different aging stages;

[0036] S6.2. If the initial value of the parameter used for evaluating the aging status of the main insulation of the motor stator bar is A0 and the current value is A1, and the parameter increases with the aging degree of the main insulation of the motor stator bar, then the normalized value is If the initial value of the parameter used for evaluating the aging status of the main insulation of the motor stator bar is B0, the current value is B1, and the parameter decreases with the aging degree of the main insulation of the motor stator bar, then the normalized value is

[0037] S6.3. Construct the characteristic parameter matrix P:

[0038]

[0039] Where y represents the type of evaluation parameter, and x represents the different aging stages of the evaluation parameter; the element values ​​of the first row of the characteristic parameter matrix P correspond to the normalized values ​​of the initial values ​​of each evaluation parameter, and the remaining rows correspond to the normalized values ​​of the current values ​​of each evaluation parameter at different aging stages.

[0040] Furthermore, in the step S7, if the score S is less than 1, the main insulation of the motor stator bar is aged; the score is shown in Formula 4:

[0041] S=P×W formula 4.

[0042] Furthermore, if the score S is lower, the aging state of the main insulation of the motor stator bar is worse and the insulation performance is lower.

[0043] Furthermore, in the step S1, the evaluation parameters include DC conductivity σ, 0.1Hz polarization dielectric loss tanδpol , dielectric loss deviation index D and depolarization charge Q depol .

[0044] Furthermore, DC conductivity σ / 0.1Hz polarization dielectric loss tanδ pol The scale of is set to 1; the scale of DC conductivity σ / dissipation deviation index D is set to 1 / 3; the scale of DC conductivity σ / depolarization charge Q depol The scale is set to 1 / 6; 0.1Hz polarization dielectric loss tanδ pol / The scale of dielectric loss deviation index D is set to 1 / 2; 0.1Hz polarization dielectric loss tanδ pol / Depolarization quantity Q depol The scale is set to 1 / 6; dielectric loss deviation index D / depolarization charge Q depol The scale of is set to 1 / 3, and then the corresponding judgment matrix M is obtained:

[0045]

[0046] The principle of the present invention is as follows:

[0047] Select factors for evaluating the influencing aging state of main insulation of motor stator wire rods; indicate the importance of each factor in the criterion layer by using pairwise comparison method and 1-9 point scaling method, obtain the scales of the two factors according to their importance, and use the matrix formed by the scales as a judgment matrix; calculate the consistency index of the judgment matrix, and obtain the corresponding average random consistency index, and calculate the consistency ratio based on the consistency index of the judgment matrix and the corresponding average random consistency index; if the consistency ratio is less than a preset threshold, obtain the corresponding eigenvector according to the maximum eigenvalue in the current judgment matrix, and obtain the corresponding weight vector W; obtain the parameter values ​​for evaluating the aging state of main insulation of motor stator wire rods and normalize them to obtain the characteristic parameter matrix P; multiply the characteristic parameter matrix P by the weight vector W to obtain the aging score S of main insulation of motor stator wire rods, and perform an evaluation to obtain the aging state of main insulation of motor stator wire rods.

[0048] The beneficial effects of the present invention are as follows:

[0049] The present invention selects factors that affect the aging state of the main insulation of the motor stator wire rod, and can quickly obtain the degradation of the main insulation of the motor stator wire rod in thermal aging, electrical aging, and internal defects through the hierarchical analysis method. Therefore, the aging state of the main insulation of the motor stator wire rod can be quickly obtained to provide data for the life estimation of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a flow chart of the present invention;

[0051] Figure 2FTIR spectrum of the thermally aged sample in the embodiment;

[0052] Figure 3 FTIR spectrum of the electrically aged stator wire bar sample in the embodiment. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] Example 1

[0055] like Figure 1 As shown, the method for evaluating the aging state of the main insulation of the motor stator bar by using the hierarchical analysis method includes the following steps:

[0056] S1. Select factors for evaluating the aging state of the main insulation of the stator bar of the motor, i.e., evaluation parameters;

[0057] S2. Indicating the importance of each factor in the criterion layer by using the pairwise comparison method and the 1-9 point scale method, obtaining the scales of the two factors according to their importance, and using the matrix formed by the scales as the judgment matrix;

[0058] S3, calculating the consistency index of the judgment matrix, and obtaining the corresponding average random consistency index, and calculating the consistency ratio based on the consistency index of the judgment matrix and the corresponding average random consistency index;

[0059] S4. If the consistency ratio is less than the preset threshold, proceed to step S5; otherwise, return to step S2 to re-acquire the scale in the judgment matrix;

[0060] S5. Obtain the corresponding eigenvector according to the maximum eigenvalue in the current judgment matrix, and obtain the corresponding weight vector W;

[0061] S6, obtaining parameter values ​​for evaluating the aging state of the main insulation of the motor stator bar and normalizing them to obtain a characteristic parameter matrix P;

[0062] S7. Multiply the characteristic parameter matrix P by the weight vector W to obtain the motor stator wire bar main insulation aging score S, and perform an evaluation to obtain the motor stator wire bar main insulation aging status.

[0063] Example 2

[0064] This embodiment further elaborates and supplements the implementation mode of the present invention on the basis of Embodiment 1.

[0065] In step S2, the scales of the two factors are obtained according to their importance, and the matrix formed by the scales is used as the judgment matrix M:

[0066]

[0067] Where m uv It is the ratio of the influence degree of the uth factor affecting the aging of the main insulation of the motor stator bar to the vth factor affecting the aging of the main insulation of the motor stator bar in the judgment matrix M. If the scale of factor u / factor v is m uv , then the scale of factor v / factor u is 1 / m uv , where u=1, 2, 3...n, v=1, 2, 3...n.

[0068] Example 3

[0069] This embodiment further elaborates and supplements the implementation mode of the present invention on the basis of Embodiment 1 or Embodiment 2.

[0070] The S3 step includes the following steps:

[0071] S3.1. Obtain the maximum eigenvalue λ in the judgment matrix max And order n, calculate the consistency index CI of the judgment matrix according to formula 1:

[0072]

[0073] S3.2, then search the average random consistency index RI table to obtain the RI value corresponding to the order n, as shown in Table 1, where the order n is not greater than 9;

[0074] Table 1 Average random consistency index RI table

[0075]

[0076] S3.3. Calculate the consistency ratio CR according to formula 2:

[0077]

[0078] Furthermore, in step S4, the preset threshold is 0.1. When the consistency ratio CR is less than the preset threshold 0.1, the next step is entered, otherwise the step S2 is returned to re-acquire the judgment matrix.

[0079] Example 4

[0080] This embodiment further elaborates and supplements the implementation manner of the present invention on the basis of Embodiment 1, Embodiment 2 or Embodiment 3.

[0081] The S5 steps are as follows:

[0082] S5.1. Obtain the eigenvector corresponding to the maximum eigenvalue in the current judgment matrix T = [t1 t2 … t J ]; where the value of J is equal to the number of evaluation parameters;

[0083] S5.2. Calculate the j-th element value w of the weight vector according to formula 3 j ; where t j is the jth element in the eigenvector corresponding to the maximum eigenvalue in the current judgment matrix,

[0084]

[0085] S5.3, obtain the corresponding weight vector W according to the element value obtained in step S5.2,

[0086] W=[w1 w2 … w j ].

[0087] Example 5

[0088] This embodiment further elaborates and supplements the implementation manner of the present invention on the basis of Embodiment 1, Embodiment 2, Embodiment 3 or Embodiment 4.

[0089] As an implementation method of this embodiment, the specific steps of establishing the feature parameter matrix in step S6 are as follows:

[0090] S6.1. Obtaining the initial value of each evaluation parameter for the aging degree of the main insulation of the motor stator bar and the current value of the evaluation parameter at different aging stages;

[0091] S6.2. If the initial value of the parameter used for evaluating the aging status of the main insulation of the motor stator bar is A0 and the current value is A1, and the parameter increases with the aging degree of the main insulation of the motor stator bar, then the normalized value is If the initial value of the parameter used for evaluating the aging status of the main insulation of the motor stator bar is B0, the current value is B1, and the parameter decreases with the aging degree of the main insulation of the motor stator bar, then the normalized value is

[0092] S6.3. Construct the characteristic parameter matrix P:

[0093]

[0094] Where y represents the type of evaluation parameter, and x represents the different aging stages of the evaluation parameter; the element values ​​of the first row of the characteristic parameter matrix P correspond to the normalized values ​​of the initial values ​​of each evaluation parameter, and the remaining rows correspond to the normalized values ​​of the current values ​​of each evaluation parameter at different aging stages.

[0095] As another implementation of this embodiment, in the step S7, the score S is less than 1, and the main insulation of the motor stator bar is aged; the score is shown in Formula 4:

[0096] S=P×W formula 4.

[0097] The lower the score S, the worse the aging condition of the main insulation of the motor stator bars and the lower the insulation performance.

[0098] Example 6

[0099] This embodiment further elaborates and supplements the implementation mode of the present invention on the basis of Embodiment 1, Embodiment 2, Embodiment 3, Embodiment 4 and Embodiment 5.

[0100] As an implementation of this embodiment, in step S1, the evaluation parameters include DC conductivity σ, 0.1Hz polarization dielectric loss tanδ pol , dielectric loss deviation index D and depolarization charge Q depol Considering that the increase ratio of DC conductivity and the increase ratio of 0.1Hz polarization dielectric loss are similar (the increase ratio here refers to the value after aging divided by the initial value, and the same applies to the following text), the importance of the two is close, so DC conductivity σ / 0.1Hz polarization dielectric loss tanδ pol The scale of is set to 1; considering that the increase ratio of DC conductivity is greater than the increase ratio of deviation index, and the dielectric loss deviation index is an important parameter reflecting the interface polarization strength, the scale of DC conductivity σ / dielectric loss deviation index D is set to 1 / 3; considering that the increase ratio of DC conductivity is much greater than the depolarization quantity, and for some samples with internal defects, only the depolarization quantity can be characterized, the DC conductivity σ / depolarization quantity Q depol The scale is set to 1 / 6; the increase in loss is accompanied by an increase in the dielectric loss deviation index, but the latter is not as obvious as the former, so the 0.1Hz polarization dielectric loss tanδ pol / The scale of dielectric loss deviation index D is set to 1 / 2; 0.1Hz polarization dielectric loss tanδ pol / Depolarization quantity Q depol The scale is set to 1 / 6; dielectric loss deviation index D / depolarization charge Q depol The scale of is set to 1 / 3, and then the corresponding judgment matrix M is obtained:

[0101]

[0102] As an example, the DC conductivity σ and 0.1Hz polarization dielectric loss tanδ of the thermal aging sample of the motor stator bar main insulation pol , dielectric loss deviation index D, depolarization charge Q depolThe initial values ​​of these four evaluation parameters and the current values ​​of each evaluation parameter at different aging stages are shown in Table 2:

[0103] Table 2

[0104]

[0105] The DC conductivity σ and 0.1Hz polarization dielectric loss tanδ of the thermal aging samples of the motor stator bar main insulation in Table 2 are pol , dielectric loss deviation index D, depolarization charge Q depol The initial values ​​of these four evaluation parameters and the current values ​​of each evaluation parameter at different aging stages are normalized to obtain the following characteristic parameter matrix P:

[0106]

[0107] Since at 0h, the initial value of each evaluation parameter is the same as the current value, the normalized value is 1.

[0108] The corresponding thermal aging sample scores are shown in Table 3:

[0109] Table 3 Thermal aging sample scores

[0110]

[0111] It can be seen from Table 3 that when the thermal aging is 10 to 15 days, the score of the thermal aging samples of the motor stator wire bar main insulation is greater than 1, indicating that the curing phenomenon of the epoxy resin in the early stage of thermal aging causes the insulation performance to change. As the thermal aging continues, the score of the thermal aging samples of the motor stator wire bar main insulation decreases and the insulation performance declines.

[0112] In order to directly obtain the degradation of insulation performance of thermal aging samples, this embodiment uses Nicolet 6700 infrared spectrometer to sample the thermal aging samples of the main insulation of the motor stator bar with different thermal aging time for Fourier transform infrared spectroscopy (FTIR). The sampling method is to take a layer of mica paper on the surface of the main insulation, and the test method is attenuated total reflection (ATR). The main group contained in epoxy mica insulation is carbonyl -C=O, and the wave number of its absorption peak is 1700~1750cm -1 , and hydroxyl -OH, with a wave number of 3621 cm -1 During the thermal aging process of the main insulation of the motor stator bar, the epoxy resin molecular chain will also generate free carbonyl and carboxyl groups under the oxidation effect of oxygen contained in the air, causing the insulation performance to deteriorate. Figure 2As shown in the figure, the FTIR spectrum does not show an obvious increase in the carbonyl index and the hydroxyl index. This is because the free radicals continue to react with oxygen to generate gas escape. The present invention considers using a wave number of 2924cm -1 The CH asymmetric stretching vibration peak is used to characterize the insulation state of the sample. In the early stage of thermal aging, the absorbance of this peak increases, indicating that the curing makes the small molecules inside the main insulation cross-linked into large molecules, and the insulation performance improves. In the late stage of thermal aging, the molecular chain breaks inside the main insulation, 2924cm -1 The absorbance of the CH asymmetric stretching vibration peak decreases, and the insulating properties decrease.

[0113] As another example, under high voltage 31.5 kV, the DC conductivity σ, 0.1 Hz polarization dielectric loss tanδ of the motor stator bar main insulation electrical aging sample pol , dielectric loss deviation index D, depolarization charge Q depol The initial values ​​of these four evaluation parameters and the current values ​​of each evaluation parameter at different aging stages are shown in Table 4:

[0114] Table 4

[0115]

[0116] The corresponding characteristic parameter matrix P is shown below:

[0117]

[0118] Since at 0h, the initial value of each evaluation parameter is the same as the current value, the normalized value is 1.

[0119] Under 31.5kV high voltage, the electrical aging sample scores are shown in Table 5:

[0120] Table 531.5kV electrical aging sample scores

[0121]

[0122]

[0123] It can be seen from Table 5 that with the increase of electrical aging time, the score of the main insulation of the motor stator bar decreases, the aging state of the electrical aging samples of the main insulation of the motor stator bar gradually deepens, and the insulation performance gradually decreases.

[0124] As another example, at a high voltage of 47.25 kV, the DC conductivity σ, 0.1 Hz polarization dielectric loss tanδ of the motor stator bar main insulation electrical aging sample pol , dielectric loss deviation index D, depolarization charge Q depolThe initial values ​​of these four evaluation parameters and the current values ​​of each evaluation parameter at different aging stages are shown in Table 6:

[0125] Table 6

[0126]

[0127] The corresponding characteristic parameter matrix P is as follows:

[0128]

[0129] Since at 0h, the initial value of each evaluation parameter is the same as the current value, the normalized value is 1.

[0130] Under 47.25kV high voltage, the electrical aging sample scores are shown in Table 7:

[0131] Table 747.25kV electrical aging sample scores

[0132]

[0133] It can be seen from Table 7 that with the increase of electrical aging time, the score decreases, the aging state of the electrical aging samples of the motor stator bar main insulation gradually deepens, and the insulation performance gradually decreases. Since the electrical aging voltage is 3U0 at this time, the higher electric field causes the motor stator bar main insulation to age more seriously. Compared with 2U0, the score drops more sharply.

[0134] Nicolet 6700 infrared spectrometer was used to test the samples of two different aging voltages for Fourier transform infrared spectroscopy (FTIR). The sampling method was to take a layer of mica paper from the main insulation surface, and the test method was attenuated total reflection (ATR). The FTIR spectra of the stator bar samples with electrical aging voltages of 2U0=31.5kV and 3U0=47.25kV are shown in Figure 2. Figure 3 shown.

[0135] According to the test results, the polar groups in epoxy mica insulation - wave number is 1700 ~ 1750cm -1 The carbonyl -C=O and the wave number are 3621cm -1 The absorbance of hydroxyl -OH increases with the progress of electrical aging. The higher the aging voltage, the more free radicals are generated. At the same time, the wave number representing the degree of cross-linking of the molecular chain is 2924cm -1The CH asymmetric stretch-contraction vibration peak, the absorbance after aging also decreases. Under the high voltage of 47.25kV, the absorbance of the electrical aging sample of the main insulation of the motor stator wire rod is already very low. The test results of FTIR show that under the condition of electrical aging, the high electric field impacts the molecular chain structure of epoxy mica, causing the molecular chain to break and generate more free polar groups. The dielectric properties of the broken molecular chain decrease, and the free polar groups will also form a path that is conducive to carrier migration, and the insulation performance decreases. In the above situation, the electrical aging of the main insulation of the motor stator wire rod under the high voltage of 47.25kV is more severe than that under the high voltage of 31.5kV, and the insulation performance decreases more significantly. Correspondingly, under the same electrical aging time obtained by this method, the degree of electrical aging of the main insulation of the motor stator wire rod under the high voltage of 47.25kV is greater than that under the high voltage of 31.5kV. It can be seen that the evaluation results of this method are consistent with the actual situation.

[0136] As another example, the DC conductivity σ, 0.1Hz polarization dielectric loss tanδ of the motor stator bar main insulation defect-free sample and the motor stator bar main insulation high-resistance paint damaged sample pol , dielectric loss deviation index D, depolarization charge Q depol The parameter values ​​of these four evaluation parameters are shown in Table 8:

[0137] Table 8

[0138]

[0139] The corresponding characteristic parameter matrix P is as follows:

[0140]

[0141] Since the initial value of each evaluation parameter is the same as the current value when there is no defect, the normalized value is 1.

[0142] The evaluation results are shown in Table 9:

[0143] Table 9 Scoring of damaged samples of high resistance paint

[0144]

[0145] It can be seen from Table 9 that the comprehensive evaluation result of the PDC test results of the samples with damaged high-resistance paint on the main insulation of the motor stator bar is that the damage of the high-resistance paint will basically not affect the insulation performance of the test section (the test section is low-resistance paint).

[0146] As another example, the DC conductivity σ and 0.1Hz polarization dielectric loss tanδ of the damaged sample of the low-resistance paint of the stator bar main insulation of the motor are pol , dielectric loss deviation index D, depolarization charge Q depol The parameter values ​​of these four evaluation parameters are shown in Table 10:

[0147] Table 10

[0148]

[0149] The corresponding characteristic parameter matrix P is as follows:

[0150]

[0151] Since there are no defects, the initial value of each evaluation parameter is the same as the current value, so the normalized value is 1.

[0152] The evaluation results are shown in Table 11:

[0153] Table 11 Scoring of damaged samples of low-resistance paint

[0154]

[0155] It can be seen from Table 11 that slight damage to the low-resistance paint will not affect the overall insulation score, while the increase in the insulation score caused by severe damage to the low-resistance paint is because the geometric capacitance of the sample segment is reduced, resulting in a decrease in the discharge charge of the sample during the depolarization process, which has no effect on the performance of the sample's main insulation.

[0156] In one embodiment of the present invention, the DC conductivity σ, 0.1Hz polarization dielectric loss tanδ of the motor stator bar main insulation defect-free sample, the low-resistance paint slightly damaged sample internal defect, and the low-resistance paint seriously damaged sample internal defect are pol , dielectric loss deviation index D, depolarization charge Q depol The parameter values ​​are shown in Table 12:

[0157] Table 12

[0158]

[0159] The corresponding characteristic parameter matrix P is as follows:

[0160]

[0161] Since the initial value of each evaluation parameter is the same as the current value when there is no defect, the normalized value is 1.

[0162] The evaluation results are shown in Table 13:

[0163] Table 13 Scoring of damaged paint samples

[0164]

[0165] It can be seen from Table 13 that this method can better evaluate the internal defects of the sample. This is because the internal defects significantly increase the depolarization charge of the sample, which accounts for a large proportion in the evaluation algorithm. When other evaluation parameters are not significantly increased compared to defect-free samples, the insulation state of the sample can still be well evaluated.

[0166] To sum up, although the present invention cannot effectively evaluate the degradation conditions such as damage of high-resistance paint and low-resistance paint, it can better evaluate the degradation of the main insulation of the motor stator wire rod (including thermal aging, electrical aging, and internal defects). Therefore, the present invention can quickly obtain the aging status of the main insulation of the motor stator wire rod and provide data for the life estimation of the motor.

Claims

1. A method for evaluating the aging state of the main insulation of the stator bar of a motor by using the hierarchical analysis method, characterized in that: The steps include: S1. Select factors for evaluating the aging state of the main insulation of the stator bar of the motor, i.e., evaluation parameters; S2. Indicating the importance of each factor in the criterion layer by using the pairwise comparison method and the 1-9 point scale method, obtaining the scales of the two factors according to their importance, and using the matrix formed by the scales as the judgment matrix; S3, calculating the consistency index of the judgment matrix, and obtaining the corresponding average random consistency index, and calculating the consistency ratio based on the consistency index of the judgment matrix and the corresponding average random consistency index; S4. If the consistency ratio is less than the preset threshold, proceed to step S5; Otherwise, return to step S2 to re-acquire the scale in the judgment matrix; S5. Obtain the corresponding eigenvector according to the maximum eigenvalue in the current judgment matrix, and obtain the corresponding weight vector W; S6, obtaining parameter values ​​for evaluating the aging state of the main insulation of the motor stator bar and normalizing them to obtain a characteristic parameter matrix P; S7. Multiply the characteristic parameter matrix P by the weight vector W to obtain the motor stator wire bar main insulation aging score S, and perform an evaluation to obtain the motor stator wire bar main insulation aging status.

2. The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the analytic hierarchy process as claimed in claim 1, characterized in that: In step S2, the scales of the two factors are obtained according to their importance, and the matrix formed by the scales is used as the judgment matrix M: Where m uv It is the ratio of the influence degree of the uth factor affecting the aging of the main insulation of the motor stator bar to the vth factor affecting the aging of the main insulation of the motor stator bar in the judgment matrix M. If the scale of factor u / factor v is m uv , then the scale of factor v / factor u is 1 / m uv , where u=1, 2, 3...n, v=1, 2, 3...n.

3. The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the analytic hierarchy process as claimed in claim 2, characterized in that: The S3 step includes the following steps: S3.

1. Obtain the maximum eigenvalue λ in the judgment matrix max And order n, calculate the consistency index CI of the judgment matrix according to formula 1: S3.2, then search the average random consistency index RI table to obtain the RI value corresponding to the order n, where the order n is not greater than 9; S3.

3. Calculate the consistency ratio CR according to formula 2:

4. The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the analytic hierarchy process as claimed in claim 1, characterized in that: In the step S4, the preset threshold is 0.

1.

5. The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the analytic hierarchy process as claimed in claim 1, characterized in that: The S5 steps are as follows: S5.

1. Obtain the eigenvector corresponding to the maximum eigenvalue in the current judgment matrix T = [t1 t2 … t J ]; where the value of J is equal to the number of evaluation parameters; S5.

2. Calculate the j-th element value w of the weight vector according to formula 3 j ; where t j is the jth element in the eigenvector corresponding to the maximum eigenvalue in the current judgment matrix, S5.3, obtain the corresponding weight vector W according to the element value obtained in step S5.2, In=[in1 in2 … in j ]。 6. The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the analytic hierarchy process according to claim 1, characterized in that: The specific steps for establishing the characteristic parameter matrix in step S6 are as follows: S6.

1. Obtaining the initial value of each evaluation parameter for the aging degree of the main insulation of the motor stator bar and the current value of the evaluation parameter at different aging stages; S6.

2. If the initial value of the parameter used for evaluating the aging status of the main insulation of the motor stator bar is A0 and the current value is A1, and the parameter increases with the aging degree of the main insulation of the motor stator bar, then the normalized value is If the initial value of the parameter used for evaluating the aging status of the main insulation of the motor stator bar is B0, the current value is B1, and the parameter decreases with the aging degree of the main insulation of the motor stator bar, then the normalized value is S6.

3. Construct the characteristic parameter matrix P: Where y represents the type of evaluation parameter, and x represents the different aging stages of the evaluation parameter; The element values ​​of the first row of the characteristic parameter matrix P correspond to the normalized values ​​of the initial values ​​of each evaluation parameter, and the remaining rows correspond to the normalized values ​​of the current values ​​of each evaluation parameter at different aging stages.

7. The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the hierarchical analysis method according to any one of claims 1 to 6, characterized in that: In the step S7, if the score S is less than 1, the main insulation of the motor stator bar is aged; the score is shown in formula 4: S=P×W Formula 4.

8. The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the analytic hierarchy process as claimed in claim 7, characterized in that: The lower the score S, the worse the aging condition of the main insulation of the motor stator bars and the lower the insulation performance.

9. The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the analytic hierarchy process as claimed in claim 8, characterized in that: In the step S1, the evaluation parameters include DC conductivity σ, 0.1Hz polarization dielectric loss tanδ pol , dielectric loss deviation index D and depolarization charge Q depol .

10. The method for evaluating the aging state of the main insulation of the stator bar of a motor by using the hierarchical analysis method according to claim 9, characterized in that: DC conductivityσ / 0.1Hz Polarization dielectric loss tanδ pol The scale of is set to 1; the scale of DC conductivity σ / dissipation deviation index D is set to 1 / 3; the scale of DC conductivity σ / depolarization charge Q depol The scale is set to 1 / 6; 0.1Hz polarization dielectric loss tanδ pol / The scale of dielectric loss deviation index D is set to 1 / 2; 0.1Hz polarization dielectric loss tanδ pol / Depolarization quantity Q depol The scale is set to 1 / 6; dielectric loss deviation index D / depolarization charge Q depol The scale of is set to 1 / 3, and then the corresponding judgment matrix M is obtained:

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