Method for diagnosing insulation condition of cvt based on apparent life deviation

Abstract

This invention belongs to the field of electrical insulation testing technology for power equipment, and discloses a method for diagnosing the insulation condition of CVTs based on apparent life deviation. First, multiple insulation characteristic quantities of the CVT under test are acquired; then, each insulation characteristic quantity is normalized; next, a weighted sum of the insulation characteristic quantities is performed to obtain an insulation condition score for the CVT under test; based on the score, the apparent service life of the CVT under test is obtained; finally, the insulation condition of the CVT under test is diagnosed using the deviation between the apparent service life and the actual service life. This invention combines various online and offline test data to determine the apparent service life, and then determines the CVT insulation condition by the deviation between the apparent service life and the actual service life. This effectively judges the insulation condition of the CVT and whether maintenance is required, improving the accuracy and reliability of CVT insulation condition detection.

Description

Technical Field

[0001] This invention belongs to the field of electrical insulation testing technology for power equipment, and relates to the insulation condition testing of capacitive voltage transformers (CVTs), and particularly to a method for diagnosing the insulation condition of CVTs based on apparent life deviation. Background Technology

[0002] Capacitor voltage transformers (CVTs) are crucial high-voltage monitoring devices in power transmission networks, and their safe and stable operation is closely related to the economic benefits and safety of the power system. In power grids with voltage levels of 110kV and above, the CVT failure rate is 0.0539%, approximately 10 times that of electromagnetic voltage transformers. Among these CVT failures, insulation faults account for as much as 76%.

[0003] To address the aforementioned CVT insulation issues, conventional power outage tests are commonly used for diagnosis and evaluation, such as capacitance measurement, insulation resistance measurement, and power frequency withstand voltage tests. However, considering that these tests are conducted under non-operating voltage conditions and the outage period is relatively long, the results often fail to reflect insulation faults in operating CVTs in a timely manner. To ensure the safe and stable operation of CVTs, it is necessary to promptly grasp the insulation status of operating CVTs and, based on this, provide early warnings for CVT insulation faults to prevent problems before they occur. Therefore, it is urgent to conduct research on simulated aging characteristic testing of capacitive voltage transformers to achieve the diagnosis of insulation performance in operating CVTs.

[0004] Patent application CN202310586721.4 discloses an online assessment method for CVT internal insulation anomalies based on self-supervised learning. This method uses CVT voltage measurements to construct and standardize a CVT voltage measurement sequence, then converts it into a time series window to establish a self-supervised learning model. It detects the CVT voltage anomaly score corresponding to the CVT voltage measurements, thereby assessing the CVT's internal insulation condition. However, this patent only assesses the CVT's internal insulation condition based on voltage measurements, lacking direct consideration of CVT internal insulation parameters, making it difficult to guarantee the effectiveness and accuracy of CVT internal insulation condition detection. Summary of the Invention

[0005] The purpose of this invention is to address the current technical limitations of existing methods in effectively detecting the insulation condition of CVTs by providing a CVT insulation condition diagnosis method based on apparent life deviation. This method obtains the apparent life based on multiple characteristic parameters that characterize CVT insulation faults, and diagnoses the CVT insulation condition by analyzing the deviation of the apparent life, thereby improving the accuracy of CVT insulation diagnosis.

[0006] The invention concept is as follows: based on the values ​​and variability of various insulation characteristic parameters inside the CVT under different aging conditions, different weights are assigned to different characteristic parameters. The insulation condition inside the CVT is quantitatively scored by multiplying the weights with the normalized characteristic parameters, thereby establishing a scoring standard. Based on the difference between the apparent life and the actual operating life obtained from the scoring, the insulation condition inside the CVT and whether maintenance is required are effectively evaluated.

[0007] To achieve the above objectives, the present invention employs the following technical solutions.

[0008] This invention provides a method for diagnosing the insulation condition of CVTs based on apparent life deviation, which includes the following steps:

[0009] S1 acquires multiple insulation characteristics of the CVT under test;

[0010] S2 normalizes each insulation characteristic quantity;

[0011] S3 performs a weighted summation of each insulation characteristic quantity to obtain the insulation status score of the CVT under test;

[0012] Based on the score, S4 calculates the apparent service life of the CVT under test according to the following formula:

[0013] a * =kS * +b

[0014] In the formula, a * S indicates the apparent service life. * This represents the insulation condition score of the CVT under test, where k and b are constants.

[0015] S5 uses the deviation between the apparent service life of the CVT under test and its actual service life to diagnose the insulation condition of the CVT under test.

[0016] In step S1 above, the insulation characteristics include total capacitance, high voltage capacitor dielectric loss, depolarization dielectric loss, third branch time constant, current-voltage phase difference, and apparent impedance change.

[0017] In step S2 above, the corresponding insulation characteristic quantities are normalized based on their maximum and minimum values. The maximum and minimum values ​​of each insulation characteristic quantity are obtained based on historical data or through measurements from a constructed insulation aging test.

[0018] In step S3 above, the weights of each insulation characteristic are obtained using the CRITIC method. In a specific implementation, the CRITIC method is used to objectively assign weights to multiple insulation characteristics; this includes the following steps:

[0019] M1 performs dimensionless processing on matrix A, which is composed of insulation characteristic quantities under different aging cycles, to obtain matrix B;

[0020] M2 obtains a comparative analysis of various insulation characteristic quantities;

[0021] The contradiction in obtaining various insulation characteristic quantities by M3;

[0022] M4 acquires information carrying capacity for various insulation characteristic quantities;

[0023] M5 obtains the weights of each insulation characteristic quantity.

[0024] In step M1 above, since the insulation characteristic quantities are all of the type where smaller is better, they are standardized to their minimum values ​​according to formula (1).

[0025]

[0026] In the formula, x ij Let x' be the element in the i-th row and j-th column of matrix A. ij The element in the i-th row and j-th column of matrix A is the normalized value after taking the minimum value. This is equivalent to the element in the i-th row and j-th column of matrix B, whose value is between 0 and 1. max(x) j Let be the maximum value in the j-th column of matrix A, and min(x) j ) represents the minimum value among the elements in the j-th column of matrix A.

[0027] In step M2 above, the comparison of various insulation characteristic quantities is calculated using equation (2);

[0028]

[0029] In the formula, σ j The comparative magnitude of the j-th insulation characteristic is given by n, where n represents the number of aging cycles. The average value of the elements in column j.

[0030] In step M3 above, the contradictions of each insulation characteristic quantity are calculated using equation (3);

[0031]

[0032] In the formula, f j For the magnitude of the contradiction in the j-th insulation characteristic, The average value of the elements in the l-th column. is the average value of the elements in the j-th column, and m represents the number of insulation characteristics.

[0033] In step M4 above, the information carrying capacity of each insulation characteristic quantity is calculated using equation (4);

[0034] C j =σj ×f j (4)

[0035] In the formula, C j is the information carrying capacity of the j-th insulation characteristic quantity.

[0036] In the above step M5, the objective weight assignment of each insulation characteristic quantity is calculated using formula (5);

[0037]

[0038] In the formula, w j is the weight of the j-th insulation characteristic quantity.

[0039] In the above step S3, taking the insulation condition score of the CVT without aging, that is, at 0 aging cycles, as the standard, the scores at other aging cycles are converted to a percentage system to obtain the percentage system score S of the insulation condition of the待测 CVT (to be determined CVT). * .

[0040] In the above step S4, based on historical data, for CVTs with different apparent operating years, calculate their insulation condition scores; then perform linear fitting based on different apparent operating years and insulation condition scores to obtain k and b, thereby determining the relationship between the apparent operating years and insulation condition scores of the CVT, that is: a * = kS * + b.

[0041] In the above step S5, the deviation of the apparent operating years of the待测 CVT (to be determined CVT) from the actual operating years is calculated according to the following formula:

[0042]

[0043] In the formula, W is the apparent life deviation of the CVT, a * is the apparent operating years of the CVT, and a is the actual operating years of the CVT.

[0044] In the present invention, according to the magnitude of the apparent life deviation W, the insulation condition of the CVT is divided into 4 grades:

[0045] W ≤ 0, meeting the insulation condition under the actual operating years, and the insulation condition needs to be identified according to the actual operating years;

[0046] 0 < W ≤ 1, slightly not meeting the insulation condition under the actual operating years, or there may be a fault, and attention needs to be paid;

[0047] 1 < W ≤ 2, not meeting the insulation condition under the actual operating years, there is a fault, and power outage maintenance needs to be arranged in a timely manner;

[0048] W>2 indicates a serious insulation failure that does not meet the actual operating life requirements, necessitating an immediate power outage for repair.

[0049] Compared with the prior art, the CVT insulation condition diagnosis method based on apparent life deviation provided by the present invention has the following advantages:

[0050] This invention combines various online and offline test data to determine the apparent service life of the CVT, and then determines the insulation condition of the CVT by the deviation between the apparent service life and the actual service life. This can effectively judge the insulation condition of the CVT and whether it needs maintenance, thus improving the accuracy and reliability of CVT insulation condition detection. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the process for determining the insulation condition rating of a CVT according to Embodiment 1 of the present invention;

[0052] Figure 2 This is a schematic diagram of a CVT live testing circuit.

[0053] Figure 3 This is a schematic diagram of the CVT insulation condition diagnosis method based on apparent life deviation provided in Embodiment 2 of the present invention. Detailed Implementation

[0054] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0055] Example 1

[0056] This embodiment takes a 35kV capacitive voltage transformer as the research object and provides a method for determining the insulation condition rating of a CVT, such as... Figure 1 As shown, it includes the following steps:

[0057] S1′ obtains multiple insulation characteristic quantities of CVTs with different aging cycles.

[0058] In this embodiment, the insulation characteristics include total capacitance, high voltage capacitor dielectric loss, depolarization dielectric loss, third branch time constant, current-voltage phase difference, and apparent impedance change.

[0059] Three CVTs with a rated voltage of 35kV were subjected to combined electro-thermal aging in the laboratory. The aging conditions are shown in the table below.

[0060] Table 1 CVT Aging Conditions

[0061]

[0062] According to the Arrhenius equation, the chemical reaction rate constant changes with temperature. At the same temperature, the reaction rate constant is negatively correlated with the apparent activation energy, while at the same temperature difference, the rate of change of the reaction rate constant is positively correlated with the apparent activation energy. Among CVT insulation materials, polypropylene film has the highest apparent activation energy, at 123.4 kJ / mol. Therefore, under the aging conditions in Table 1, the polypropylene film exhibits the greatest change in aging reaction rate, and after the same aging time, its lifespan changes the most. Thus, when performing time-temperature equivalent conversion, the apparent activation energy of the polypropylene film should be used as the benchmark to characterize the overall aging degree of the CVT.

[0063] Under normal operating conditions, the internal oil temperature of the CVT is approximately 55–65°C. Taking the midpoint, we consider the internal oil temperature of the CVT under operating conditions to be 60°C. According to the Arrhenius equation, a time-temperature equivalent conversion is performed on the CVT aging degree under 105°C and operating conditions. This shows that the CVT lifespan under aging conditions in this embodiment is only 1 / 202 of that under operating conditions, meaning 20 aging cycles correspond to 29.52 years of normal operating life. The service life of electrical equipment is generally designed to be 30 years. However, considering the many influencing factors during normal operation, most equipment cannot operate for 30 years. Therefore, during normalization, the data for the unaged CVT is set to a maximum value of 1, and the data for the CVT after 20 aging cycles is set to a minimum value of 0. This standard is used to normalize the CVT data for different aging cycles to better reflect reality.

[0064] Every 5 aging cycles, dielectric loss and capacitance tests, polarization-depolarization current tests, and voltage and current tests were performed on the three CVTs, and the average values ​​of the test data were taken, as shown in the table below.

[0065] Table 2 CVT Aging Test Data

[0066]

[0067] Note: (1) The capacitance and dielectric loss of CVT are tested by dielectric loss meter, and the total capacitance and high voltage capacitor dielectric loss are extracted as insulation characteristic quantities to judge the insulation status of CVT (see Su Chenyun, Huang Zhen. Analysis of dielectric loss and capacitance measurement methods of UHV capacitor voltage transformer [J]. China Electric Power, 2012, 45(04): 38-41);

[0068] (2) Polarization-depolarization test was performed on the CVT, and the depolarization dielectric loss and the time constant of the third branch were calculated and extracted as insulation characteristic quantities for judging the insulation status of the CVT (see Zhang Han, Wan Baoquan, Hu Wei, et al. Evaluation of moisture status of dry bushing impregnated paper insulation based on PDC method [J]. Electric Power Engineering Technology, 2022, 41(03): 178-185 and Yun Hao, Gao Xuan, Wang Liang, et al. Study on irradiation aging of nuclear power plant XLPE cable based on PDC method [J]. Insulation Materials, 2020, 53(02): 64-70);

[0069] (3) Perform live testing on the CVT (i.e., secondary side voltage and primary side current testing). The CVT test circuit is as follows: Figure 2 As shown; the current-voltage phase difference and apparent impedance change are calculated and extracted as insulation characteristic quantities for judging the insulation condition of the CVT; the current-voltage phase difference is the phase difference between the primary current measured by the current sensor and the secondary output voltage across the damper; the apparent impedance value is the ratio of the effective value of the primary voltage to the primary current of the CVT, and the apparent impedance change value refers to the change in apparent impedance value compared to the value before aging.

[0070] S2′ obtains the weights of each insulation characteristic.

[0071] This embodiment uses the CRITIC method to objectively weight multiple insulation characteristics, specifically including the following steps:

[0072] M1 performs dimensionless processing on matrix A, which is composed of insulation characteristic quantities under different aging cycles, to obtain matrix B.

[0073] Since the insulation characteristic quantities are all of the type where smaller is better, they are standardized to their minimum values ​​according to formula (1);

[0074]

[0075] In the formula, x ij Let x' be the element in the i-th row and j-th column of matrix A. ij The element in the i-th row and j-th column of matrix A is the normalized value after taking the minimum value. This is equivalent to the element in the i-th row and j-th column of matrix B, whose value is between 0 and 1. max(x) j Let be the maximum value in the j-th column of matrix A, and min(x) j ) represents the minimum value among the elements in the j-th column of matrix A.

[0076] In this embodiment, all six insulation characteristics are optimized for smaller values; therefore, they are normalized to their minimum values, and the minimum value normalization matrix B is constructed as follows:

[0077]

[0078] M2 obtains a comparison of various insulation characteristics.

[0079] This step uses equation (2) to calculate the comparison of various insulation characteristic quantities;

[0080]

[0081] In the formula, σ j The comparative magnitude of the j-th insulation characteristic is given by n, where n represents the number of aging cycles. The average value of the elements in column j.

[0082] In this embodiment, the comparative σ of each insulation characteristic quantity is obtained by using the above formula (2):

[0083] σ=[0.38520.38230.3834 0.3906 0.3812 0.4055]

[0084] The contradiction in obtaining various insulation characteristic quantities by M3.

[0085] This step uses equation (3) to calculate the contradictions of each insulation characteristic quantity;

[0086]

[0087] In the formula f j For the magnitude of the contradiction in the j-th insulation characteristic, The average value of the elements in the l-th column. is the average value of the elements in the j-th column, and m represents the number of insulation characteristics.

[0088] In this embodiment, the contradiction f of each insulation characteristic quantity is obtained through the above equation (3):

[0089] f=[0.07250.06130.2011 0.0945 0.0760 0.1374].

[0090] M4 carries information about various insulation characteristics.

[0091] This step uses equation (4) to calculate the information carrying capacity of each insulation characteristic quantity;

[0092] C j =σ j ×f j (4)

[0093] In the formula, C j Let j represent the amount of information carried by the insulation characteristic quantity j.

[0094] In this embodiment, the carrying capacity c of each insulation characteristic quantity is obtained by using the above formula (4):

[0095] C=[0.02790.02340.0771 0.0369 0.0290 0.0557]

[0096] M5 obtains the weights of each insulation characteristic quantity.

[0097] This step uses equation (5) to calculate the objective weight assignment of each insulation characteristic quantity;

[0098]

[0099] In the formula, w j The weight of the j-th insulation feature is denoted as .

[0100] In this embodiment, the weights w of each insulation characteristic quantity are obtained using the above formula (5):

[0101] w=[0.117 0.0938 0.3029 0.1476 0.1158 0.2229]

[0102] S3′ obtains the insulation condition score of CVTs with different aging cycles.

[0103] In this step, we first use equation (6) to multiply the weight w with the transpose of the matrix B standardized according to the minimum value to obtain the CVT insulation condition score.

[0104]

[0105] In the formula, S i The insulation condition of the CVT is scored during the i-th aging cycle.

[0106] Then, using equation (7), the CVT insulation condition score under the unaged condition (i.e., 0 aging cycles) is used as the standard to convert the scores under other aging cycles into a percentage system, thus obtaining the CVT insulation condition percentage score S. * ;

[0107]

[0108] In this embodiment, the insulation condition score S of CVT under different aging cycles is obtained by multiplying the weight w of each insulation characteristic quantity with the transpose of the minimum value normalization matrix B and converting the result to a percentage system. * :

[0109] S * =[100 66.2947 48.7253 24.1582 0]

[0110] S4′ obtains the relationship between the insulation condition score of CVTs with different aging cycles and their apparent service life.

[0111] This step uses equation (8) to calculate the CVT insulation condition score S. * Relationship with aging duration h;

[0112] S * =k′h+b′(8)

[0113] In the formula, k′ and b′ are the CVT insulation condition scores S. * The slope and intercept obtained by linear fitting with the aging time h are both constants.

[0114] In this embodiment, the relationship between thermal aging time and insulation score is fitted and calculated to obtain k′ and b′. Based on the correspondence between thermal aging time and apparent operating time (i.e., 1 hour of thermal aging is approximately equal to 202 hours of apparent operating time), the apparent operating life 'a' can be calculated. * CVT insulation condition rating S * The relationship, i.e., a * =kS * +b, as shown below:

[0115] a * =29.33477-0.30474S *

[0116] Calculate the apparent service life a * The difference between the actual operating years 'a' of the CVT and the actual operating years 'a', then according to... The apparent life deviation W is obtained, and based on the magnitude of the apparent life deviation W, the internal insulation condition of the CVT under test is divided into four levels, as shown in Table 3. By comparing the apparent life deviation W of the CVT under test with each level, the internal insulation condition of the CVT can be obtained.

[0117] Table 3 CVT Insulation Status Rating Levels

[0118]

[0119] Example 2

[0120] refer to Figure 3 This embodiment focuses on a CVT with a rated voltage of 35kV that has been in operation for 5 years. The internal insulation condition is assessed using the CVT insulation condition diagnosis method based on apparent life deviation provided by this invention. The specific steps include:

[0121] S1 acquires multiple insulation characteristics of the CVT under test.

[0122] During periodic maintenance, dielectric loss and capacitance tests, as well as polarization-depolarization current tests, are performed on the CVT under test to obtain its total capacitance, high-voltage capacitor dielectric loss, depolarization dielectric loss, and third branch time constant. During CVT operation, the current-voltage phase difference and apparent impedance change are calculated based on real-time monitoring data. The total capacitance, high-voltage capacitor dielectric loss, depolarization dielectric loss, third branch time constant, current-voltage phase difference, and apparent impedance change are used as characteristic parameters for judging its internal insulation condition, and their values ​​are shown in Table 4.

[0123] Table 4 Test data of insulation characteristic quantities of the CVT under test

[0124]

[0125] S2 normalizes each insulation characteristic quantity.

[0126] The corresponding insulation characteristics are normalized based on their maximum and minimum values. The maximum and minimum values ​​of each insulation characteristic are obtained from historical data or through measurements obtained from a constructed insulation aging test.

[0127] In this embodiment, the maximum and minimum values ​​of each insulation characteristic quantity in Table 2 obtained in Example 1 are used as the standard to normalize the data of the CVT under test. The normalized data is shown in Table 5:

[0128] Table 5. Insulation characteristics after normalization.

[0129]

[0130] S3 performs a weighted summation of each insulation characteristic quantity to obtain the insulation condition score of the CVT under test.

[0131] Using the insulation condition score of the CVT under no aging (i.e., 0 aging cycles) as the standard, the scores under other aging cycles are converted to a percentage system to obtain the percentage score S of the insulation condition of the CVT under test. * .

[0132] In this embodiment, the normalized data is multiplied by the weights of each insulation characteristic obtained in Example 1, and then converted to a percentage score, resulting in an insulation condition score of 35.8348 for the CVT under test.

[0133] Based on the score, S4 calculates the apparent service life of the CVT under test according to the following formula:

[0134] a * =kS * +b

[0135] In the formula, a * S indicates the apparent service life. *The value represents the insulation condition score of the CVT under test, and k and b represent constants. According to Example 1, b = 29.33477 and k = -0.30474.

[0136] Based on the relationship between insulation score and apparent service life, its apparent service life a is obtained. * It was 18.41 years ago.

[0137] S5 uses the deviation between the apparent service life of the CVT under test and its actual service life to diagnose the insulation condition of the CVT under test.

[0138] The deviation between the apparent service life and the actual service life of the CVT under test is calculated using the following formula:

[0139]

[0140] In the formula, W represents the apparent life deviation of the CVT, and a * 'a' represents the apparent operating years of the CVT, and 'a' represents the actual operating years of the CVT.

[0141] In this embodiment, the calculated apparent life deviation is 2.682. According to Table 3, the insulation condition is determined to be severely inconsistent with the expected service life, indicating a serious fault that requires immediate power outage and maintenance. An unpacking inspection of the CVT confirmed this assessment, proving the effectiveness of this method.

[0142] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0143] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for diagnosing the insulation condition of a CVT based on apparent life deviation, characterized in that, Includes the following steps: S1 acquires multiple insulation characteristics of the CVT under test; the insulation characteristics include total capacitance, high voltage capacitor dielectric loss, depolarization dielectric loss, third branch time constant, current-voltage phase difference and apparent impedance change value; S2 normalizes each insulation characteristic quantity; S3 performs a weighted summation of each insulation characteristic to obtain the insulation condition score of the CVT under test; the CRITIC method is used to objectively assign weights to multiple insulation characteristics; specifically, the following steps are included: M1 performs dimensionless processing on matrix A, which consists of insulation characteristic quantities under different aging cycles, to obtain matrix B; M2 obtains a comparison of various insulation characteristic quantities; The contradiction in obtaining various insulation characteristic quantities by M3; M4 carries information about various insulation characteristics; M5 obtains the weights of each insulation characteristic quantity; Based on the score, S4 calculates the apparent service life of the CVT under test according to the following formula: ； In the formula, a * S indicates the apparent service life. * This represents the insulation condition score of the CVT under test, where k and b are constants. S5 uses the deviation between the apparent service life of the CVT under test and its actual service life to diagnose the insulation condition of the CVT under test. Specifically, the deviation between the apparent service life and the actual service life of the CVT under test is calculated using the following formula: ； In the formula, W represents the apparent life deviation of the CVT, and a * 'a' represents the apparent operating years of the CVT, and 'a' represents the actual operating years of the CVT.

2. The CVT insulation condition diagnosis method based on apparent life deviation according to claim 1, characterized in that, In step S2, the corresponding insulation characteristic quantities are normalized based on the maximum and minimum values ​​of each insulation characteristic quantity.

3. The CVT insulation condition diagnosis method based on apparent life deviation according to claim 1, characterized in that, In step M2, the comparison of various insulation characteristic quantities is calculated using equation (2); (2)； In the formula, σ j The comparative magnitude of the j-th insulation characteristic is given by n, where n represents the number of aging cycles. The average value of the elements in column j.

4. The CVT insulation condition diagnosis method based on apparent life deviation according to claim 3, characterized in that, In step M3, the inconsistencies of each insulation characteristic quantity are calculated using equation (3); (3)； In the formula, f j For the magnitude of the contradiction in the j-th insulation characteristic, The average value of the elements in the l-th column. is the average value of the elements in the j-th column, and m represents the number of insulation characteristics.

5. The CVT insulation condition diagnosis method based on apparent life deviation according to claim 4, characterized in that, In step M4, the information carrying capacity of each insulation characteristic quantity is calculated using equation (4); (4)； In the formula, C j Let j represent the amount of information carried by the insulation characteristic quantity j.

6. The CVT insulation condition diagnosis method based on apparent life deviation according to claim 5, characterized in that, In step M5, the objective weights of each insulation characteristic quantity are calculated using equation (5); (5)； In the formula, w j The weight of the j-th insulation feature is denoted as .

7. The CVT insulation condition diagnosis method based on apparent life deviation according to claim 5, characterized in that, In step S3, the insulation condition score of the CVT under no aging (i.e., 0 aging cycles) is used as the standard, and the scores under other aging cycles are converted to a percentage system to obtain the percentage score S of the insulation condition of the CVT under test. * .

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