A method, device, equipment and medium for evaluating the service life of current transformer oil paper

Abstract

The application discloses a kind of current transformer oil paper life evaluation method, device, equipment and medium.The method comprises: obtaining the current transformer oil paper to be detected, the equivalent aging time of current transformer oil paper, test temperature and test harmonic frequency, the equivalent aging time, test temperature and test harmonic frequency are input into the pre-trained life evaluation model to obtain target breakdown field strength, according to target breakdown field strength, the life of current transformer oil paper is evaluated.Wherein, by the pre-trained life evaluation model to determine target breakdown field strength, i.e. the insulation performance of current transformer oil paper can be determined, and if target breakdown field strength is equal to preset value, the equivalent aging time corresponding to the target breakdown field strength can be used as the service life of current transformer oil paper, the life of current transformer oil paper is evaluated, to avoid the insulation performance of current transformer oil paper is aged after time and temperature and other factors, to ensure the safety and stability of current transformer.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of oil paper detection, in particular to a life evaluation method, device, equipment and medium for oil paper of a current transformer. BACKGROUND

[0002] With the development of the power system, in order to ensure the safety and reliability of the power system, a current transformer is generally used to measure and protect the power system.

[0003] In the prior art, the current transformer can be divided into a dry-type current transformer, a gas insulated current transformer and an oil-immersed current transformer. Among them, the heat dissipation medium of the oil-immersed current transformer is transformer oil, and the heat generated during the operation of the oil-immersed current transformer is conducted to the metal shell through the transformer oil, so that the oil-immersed current transformer has the advantages of uniform heat conduction, fast heat dissipation and good recovery of insulation performance, and due to the advantages of simple structure, low manufacturing cost and high reliability, the oil-immersed current transformer has been widely applied in the power system.

[0004] Since the quality of the current transformer oil paper of the main insulation in the oil-immersed current transformer will affect the normal use of the oil-immersed current transformer, at the same time, the insulation strength of the current transformer oil paper will be continuously reduced by various factors, which will correspondingly cause an increase in the failure of the oil-immersed current transformer, therefore, in order to ensure the stability and reliability of the oil-immersed current transformer, it is necessary to ensure that the insulation strength of the current transformer oil paper is greater than the preset insulation strength, but since the current transformer oil paper can be used for a long time, and it is difficult to monitor the main insulation inside the oil-immersed current transformer in actual application, the service life of the current transformer oil paper cannot be evaluated.

[0005] Therefore, how to effectively evaluate the service life of the current transformer oil paper is a technical problem to be solved by those skilled in the art. SUMMARY

[0006] Based on the above problems, the application provides a life evaluation method, device, equipment and medium for current transformer oil paper, to effectively evaluate the service life of the current transformer oil paper.

[0007] The embodiments of the application disclose the following technical solutions:

[0008] In a first aspect, the embodiments of the application provide a life evaluation method for current transformer oil paper, and the method comprises the following steps:

[0009] determining the equivalent aging time, the test temperature and the test harmonic frequency of the current transformer oil paper to be detected;

[0010] inputting the equivalent aging time, the test temperature and the test harmonic frequency into a pre-trained life evaluation model to obtain a target breakdown field strength;

[0011] evaluate the life of the current transformer oil paper according to the target breakdown field strength.

[0012] Optionally, the inputting the equivalent aging time, the test temperature and the test harmonic frequency into the pre-trained life evaluation model to obtain the target breakdown field strength comprises:

[0013] determining an initial field strength and an initial coefficient according to the equivalent aging time through the pre-trained life evaluation model;

[0014] determining the target breakdown field strength according to the test temperature, the test harmonic frequency, the initial field strength and the initial coefficient.

[0015] Optionally, the inputting the equivalent aging time, the test temperature and the test harmonic frequency into the pre-trained life evaluation model to obtain the target breakdown field strength comprises:

[0016] when the equivalent aging time is greater than a preset inflection point time, inputting the equivalent aging time, the test temperature and the test harmonic frequency into the pre-trained life evaluation model to obtain a first target breakdown field strength;

[0017] when the equivalent aging time is less than the preset inflection point time, inputting the equivalent aging time, the test temperature and the test harmonic frequency into the pre-trained life evaluation model to obtain a second target breakdown field strength;

[0018] when the equivalent aging time is equal to the preset inflection point time, inputting the equivalent aging time, the test temperature and the test harmonic frequency into the pre-trained life evaluation model to obtain a third target breakdown field strength.

[0019] Optionally, the life evaluation model is obtained by the following way:

[0020] high-temperature aging treatment is performed on the training oil paper insulation material according to a preset aging temperature;

[0021] a plurality of same training samples are made by using the processed training oil paper insulation material;

[0022] harmonic breakdown experiments are performed on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and a plurality of experimental results are obtained as an experimental result set;

[0023] a plurality of experimental result sets are obtained according to different preset aging temperatures;

[0024] three-dimensional fitting is performed on the plurality of experimental result sets to obtain a target three-dimensional fitting equation set;

[0025] According to the three-dimensional fitting equation set, a life evaluation model is obtained.

[0026] In a second aspect, the embodiments of the present application provide a life evaluation device for current transformer oil paper, the device comprising:

[0027] A test data determination module is configured to determine an equivalent aging time, a test temperature, and a test harmonic frequency of the current transformer oil paper to be detected.

[0028] A target breakdown field strength determination module is configured to input the equivalent aging time, the test temperature, and the test harmonic frequency into a pre-trained life evaluation model to obtain a target breakdown field strength.

[0029] A life evaluation module is configured to evaluate the life of the current transformer oil paper according to the target breakdown field strength.

[0030] Optionally, the target breakdown field strength determination module is specifically configured to:

[0031] determine an initial field strength and an initial coefficient according to the equivalent aging time through the pre-trained life evaluation model;

[0032] determine the target breakdown field strength according to the test temperature, the test harmonic frequency, the initial field strength, and the initial coefficient.

[0033] Optionally, the target breakdown field strength determination module is specifically configured to:

[0034] when the equivalent aging time is greater than a preset inflection point time, input the equivalent aging time, the test temperature, and the test harmonic frequency into the pre-trained life evaluation model to obtain a first target breakdown field strength;

[0035] when the equivalent aging time is less than the preset inflection point time, input the equivalent aging time, the test temperature, and the test harmonic frequency into the pre-trained life evaluation model to obtain a second target breakdown field strength;

[0036] when the equivalent aging time is equal to the preset inflection point time, input the equivalent aging time, the test temperature, and the test harmonic frequency into the pre-trained life evaluation model to obtain a third target breakdown field strength.

[0037] Optionally, the life evaluation model is specifically obtained by the following way:

[0038] A high-temperature aging processing module is configured to perform high-temperature aging processing on training oil paper insulation materials according to a preset aging temperature.

[0039] A training sample acquisition module is configured to manufacture a plurality of identical training samples by using the processed training oil paper insulation materials.

[0040] An experimental result set determination module is configured to perform a harmonic breakdown experiment on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and obtain a plurality of experimental results as an experimental result set;

[0041] A plurality of experimental result set determination modules are configured to obtain a plurality of experimental result sets according to different preset aging temperatures;

[0042] A three-dimensional fitting module is configured to perform three-dimensional fitting on the plurality of experimental result sets to obtain a target three-dimensional fitting equation set;

[0043] A life assessment model determination module is configured to obtain a life assessment model according to the three-dimensional fitting equation set.

[0044] In a third aspect, an embodiment of the present application provides a computer device, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the life assessment method of the current transformer oil paper when executing the computer program.

[0045] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium, which stores instructions, and when the instructions are executed on a terminal device, the terminal device executes the life assessment method of the current transformer oil paper.

[0046] Compared with the prior art, the present application has the following beneficial effects:

[0047] The present application obtains the current transformer oil paper to be detected, determines the equivalent aging time, test temperature and test harmonic frequency of the current transformer oil paper, inputs the equivalent aging time, test temperature and test harmonic frequency into a pre-trained life assessment model to obtain a target breakdown field strength, and assesses the life of the current transformer oil paper according to the target breakdown field strength. Since the target breakdown field strength can determine the insulation performance of the current transformer oil paper, the insulation performance of the current transformer oil paper can be determined by determining the target breakdown field strength through the pre-trained life assessment model. If the target breakdown field strength is equal to a preset value, it is considered that the current transformer oil paper corresponding to the target breakdown field strength needs to be replaced, the life of the current transformer oil paper is assessed, the failure caused by the aging of the insulation performance of the current transformer oil paper due to factors such as time and temperature is avoided, and the safety and stability of the current transformer are ensured. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0049] Figure 1 A flow chart of a life evaluation method of a current transformer oil paper provided by the embodiments of the present application;

[0050] Figure 2 A flow chart of a determination method of a life evaluation model provided by the embodiments of the present application;

[0051] Figure 3 A schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of an unaged sample provided by the embodiments of the present application;

[0052] Figure 4 A schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of a 10-day aged sample provided by the embodiments of the present application;

[0053] Figure 5 A schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of a 30-day aged sample provided by the embodiments of the present application;

[0054] Figure 6 A schematic diagram of a parameter curve of a three-dimensional fitting equation provided by the embodiments of the present application;

[0055] Figure 7 A structural schematic diagram of a life evaluation device of a current transformer oil paper provided by the embodiments of the present application. DETAILED DESCRIPTION

[0056] As described above, in the research on the current transformer oil paper, it is found that in the prior art, the current transformer can be divided into a dry-type current transformer, a gas insulated current transformer and an oil-immersed current transformer. Among them, the heat dissipation medium of the oil-immersed current transformer is transformer oil, and the heat generated during the operation of the oil-immersed current transformer is conducted to the metal shell through the transformer oil, so that the oil-immersed current transformer has the advantages of uniform heat conduction, fast heat dissipation and good recovery of insulation performance, and due to the advantages of simple structure, low manufacturing cost and high reliability, the oil-immersed current transformer has been widely applied in power systems.

[0057] The quality of the current transformer oil paper of the main insulation in the oil-immersed current transformer will affect the normal use of the oil-immersed current transformer, meanwhile, the insulation strength of the current transformer oil paper will be continuously reduced by various factors, which will lead to an increase in the failure of the oil-immersed current transformer, therefore, in order to ensure the stability and reliability of the oil-immersed current transformer, it is necessary to ensure that the insulation strength of the current transformer oil paper is greater than the preset insulation strength, but since the current transformer oil paper can be used for a long time, and it is difficult to monitor the main insulation inside the oil-immersed current transformer in actual application, the service life of the current transformer oil paper cannot be evaluated.

[0058] In order to solve the above problems, the embodiment of the present application provides a current transformer oil paper life evaluation method, device, equipment and medium. The method comprises: obtaining a current transformer oil paper to be detected, determining the equivalent aging time, test temperature and test harmonic frequency of the current transformer oil paper, inputting the equivalent aging time, test temperature and test harmonic frequency into a pre-trained life evaluation model to obtain a target breakdown field strength, and evaluating the life of the current transformer oil paper according to the target breakdown field strength.

[0059] In this way, since the target breakdown field strength can determine the insulation performance of the current transformer oil paper, the insulation performance of the current transformer oil paper can be determined by determining the target breakdown field strength through the pre-trained life evaluation model, and if the target breakdown field strength is equal to a preset value, it is considered that the current transformer oil paper corresponding to the target breakdown field strength needs to be replaced, the life evaluation of the current transformer oil paper is realized, the failure caused by the aging of the insulation performance of the current transformer oil paper due to factors such as time and temperature is avoided, and the safety and stability of the current transformer are ensured.

[0060] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0061] Referring to Figure 1 , the figure is a flowchart of a current transformer oil paper life evaluation method provided by the embodiment of the present application, in combination with Figure 1 , the current transformer oil paper life evaluation method provided by the embodiment of the present application can comprise:

[0062] S101: Determine the equivalent aging time, test temperature and test harmonic frequency of the current transformer oil paper to be detected.

[0063] Current transformer oil paper refers to a composite insulating material made of fiber paper impregnated with insulating oil, used in current transformers.

[0064] It should be noted that, in this embodiment, the current transformer mentioned in this application refers to a 220kV oil-immersed current transformer.

[0065] Equivalent aging time refers to the time obtained after equivalent calculation of the actual service life through high-temperature aging.

[0066] Specifically, in one feasible implementation, the thermal aging time under experimental conditions can be correlated with the operating time of the current transformer oil paper under actual conditions, based on the Arrhenius steady-state temperature acceleration model. First, the aging acceleration factor is calculated using the following formula:

[0067]

[0068] Where T0 is the actual operating temperature, T is the aging temperature, and E is the aging temperature. a The chemical activation energy is given by k, where k is the Boltzmann constant (1.380649 × 10⁻⁶). -23 J / K), AF is an aging-accelerating factor.

[0069] Since the insulation of a current transformer normally operates at a maximum temperature of 80℃ and the fault temperature does not exceed 110℃, multiplying the aging time by the accelerated aging factor equals the actual operating time of the current transformer's oil paper insulation. The chemical activation energy of oil paper insulation is generally 80–100 kJ / mol, conservatively taken as 80 kJ / mol. The aging acceleration factor is calculated to be: AF = 28.72. The correspondence between aging time and actual operating time is shown in Table 1 below:

[0070] Table 1. Correspondence between aging time and actual operating time

[0071] 130°C aging time (days) 0 5 10 20 30 80°C actual run time (months) 0 4.79 9.57 19.15 28.72

[0072] Test temperature refers to the temperature at which the current transformer's oil paper is tested.

[0073] The term "harmonic frequency test" refers to the harmonic frequency detected during a breakdown test of the oil paper in a current transformer.

[0074] It should be noted that the test temperature mentioned in the embodiments of this application refers to the breakdown temperature during harmonic breakdown testing, and not the aging temperature during high-temperature aging.

[0075] It should be noted that in the embodiment of the present application, the actual use time length of the current transformer is obtained, and then the actual use time length is equivalent to the aging time at a preset temperature. By replacing the actual use time length with the equivalent aging time, the problem that the oil paper of the current transformer can be used for a long time and it is difficult to monitor the oil paper of the current transformer in actual application is avoided.

[0076] S102: input the equivalent aging time, test temperature and test harmonic frequency into the pre-trained life evaluation model to obtain a target breakdown field strength.

[0077] The pre-trained life evaluation model means a model that can evaluate the use time length of the oil paper of the current transformer.

[0078] It should be noted that under the action of a strong electric field, a solid dielectric loses its electrical insulation ability and suddenly changes from an insulating state to a good conductive state, resulting in the lowest critical voltage of breakdown, which is called breakdown voltage. In a uniform electric field, the ratio of the breakdown voltage to the thickness of the solid dielectric is called the breakdown electric field strength (simply referred to as the breakdown field strength, also called the dielectric strength), which reflects the electrical strength (i.e. insulation degree) of the solid dielectric itself. Therefore, in the embodiment, by determining the target breakdown field strength, it is determined whether the insulation performance of the oil paper of the current transformer to be detected is qualified, and the service life thereof can be further evaluated.

[0079] As an implementable embodiment, the step S102 can include:

[0080] Step 11: determining an initial field strength and an initial coefficient according to the equivalent aging time through the pre-trained life evaluation model.

[0081] Step 12: determining a target breakdown field strength according to the test temperature, test harmonic frequency, initial field strength and initial coefficient.

[0082] It should be noted that the target breakdown field strength corresponding to the actual use time length can be determined according to the equivalent aging time, and the service life of the oil paper of the current transformer can be further predicted by using the pre-trained life evaluation model. For example, if the equivalent aging time corresponding to the use time length of 11 years is 11 days, the test temperature is 30°C, the test harmonic frequency is 200 Hz, and the target breakdown field strength obtained is E = 49 kV*mm -1 , the preset breakdown field strength is 35 kV*mm -1 , then the target breakdown field strength when the use time length is 20 years can be further predicted, so as to realize the life evaluation of the oil paper of the current transformer.

[0083] It should be noted that in the embodiment of the present application, the step S102 can further include:

[0084] Step 21: when the equivalent aging time is greater than the preset inflection point time, inputting the equivalent aging time, the test temperature and the test harmonic frequency into the pre-trained life evaluation model to obtain a first target breakdown field strength;

[0085] Step 22: when the equivalent aging time is less than the preset inflection point time, inputting the equivalent aging time, the test temperature and the test harmonic frequency into the pre-trained life evaluation model to obtain a second target breakdown field strength;

[0086] Step 23: when the equivalent aging time is equal to the preset inflection point time, inputting the equivalent aging time, the test temperature and the test harmonic frequency into the pre-trained life evaluation model to obtain a third target breakdown field strength.

[0087] It should be noted that, as an implementable embodiment, in the embodiments of the present application, the equivalent aging time range is set to [0, 30] days, and further, in the determination process of the life evaluation model, when the equivalent aging time is 10 days, the fitting result will appear an inflection point, therefore, different fitting equations are set based on the inflection point time, so that the life evaluation model is more accurate.

[0088] It should be noted that, when the equivalent aging time is greater than the preset inflection point time, the first life evaluation equation is used to determine the first target breakdown field strength; correspondingly, when the equivalent aging time is less than the preset inflection point time, the second life evaluation equation is used to determine the second target breakdown field strength; when the equivalent aging time is equal to the preset inflection point time, the first life evaluation equation or the second life evaluation equation can be used to determine the third target breakdown field strength, or the first life evaluation equation and the second life evaluation equation are used to determine the first field strength and the second field strength respectively, and the average of the first field strength and the second field strength is calculated as the third target breakdown field strength.

[0089] S103: evaluating the life of the current transformer oil paper according to the target breakdown field strength.

[0090] It should be noted that, by obtaining the target breakdown field strength, the insulation strength of the current transformer oil paper under the actual use time length can be determined, and by comparing the target breakdown field strength with the preset breakdown field strength, whether the insulation performance of the current transformer oil paper is qualified can be determined, if not qualified, the current transformer oil paper needs to be replaced, and if qualified, the new equivalent aging time corresponding to the preset use time length can be determined according to the equivalent aging time corresponding to the actual use time length, and the life of the power transformer oil paper is evaluated.

[0091] In an implementable embodiment, after determining the equivalent aging time corresponding to the actual service time of the current transformer oil paper and the target breakdown field strength, the target breakdown field strength corresponding to a new continuous equivalent aging time can be further predicted according to the equivalent aging time and the target breakdown field strength, a curve graph about the equivalent aging time and the target breakdown field strength is generated, and the life of the current transformer oil paper is evaluated and predicted.

[0092] The life evaluation method of the current transformer oil paper provided by the embodiments of the present application comprises the following steps: obtaining a current transformer oil paper to be detected; determining an equivalent aging time, a test temperature and a test harmonic frequency of the current transformer oil paper; inputting the equivalent aging time, the test temperature and the test harmonic frequency into a pre-trained life evaluation model to obtain a target breakdown field strength; and evaluating the life of the current transformer oil paper according to the target breakdown field strength. Since the target breakdown field strength can determine the insulation performance of the current transformer oil paper, the insulation performance of the current transformer oil paper can be determined by determining the target breakdown field strength through the pre-trained life evaluation model. If the target breakdown field strength is equal to a preset value, it is considered that the current transformer oil paper corresponding to the target breakdown field strength needs to be replaced, the life evaluation of the current transformer oil paper is realized, the failure caused by the aging of the insulation performance of the current transformer oil paper due to factors such as time and temperature is avoided, and the safety and stability of the current transformer are ensured.

[0093] Based on the life evaluation method of the current transformer oil paper provided in the above embodiments, the embodiments of the present application further provide a determination method of a life evaluation model. Referring to Figure 2 , the flowchart of the determination method of the life evaluation model provided by the embodiments of the present application is shown, and the determination method of the life evaluation model provided by the embodiments of the present application can specifically comprise: Figure 2

[0094] S201: High-temperature aging treatment is performed on the training oil paper insulation material according to a preset aging temperature.

[0095] The training oil paper insulation material means an insulation oil material used for manufacturing the current transformer oil paper.

[0096] It should be noted that, in actual working conditions, the insulation performance of the current transformer oil paper will be affected by temperature and will decrease with time. In order to evaluate the service life of the current transformer oil paper, high-temperature aging needs to be performed to simulate the natural aging time under the actual working temperature.

[0097] S202: A plurality of same training samples are manufactured by using the processed training oil paper insulation material.

[0098] The training sample means an oil paper made of the processed training oil paper insulation material. ​

[0099] It should be noted that in the present embodiment, the insulation performance of the high-temperature aged training oil paper insulation material needs to be evaluated, and therefore the training sample needs to be made of the high-temperature aged training oil paper insulation material, and the harmonic breakdown experiment needs to be performed on the training sample.

[0100] S203: Perform the harmonic breakdown experiment on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and obtain multiple experimental results as the experimental result set.

[0101] It should be noted that in the present embodiment, the breakdown temperature is also considered in the harmonic breakdown experiment, and therefore the influence of the breakdown temperature on the training sample needs to be considered. The aging temperature in the above high-temperature aging process is not the same as the breakdown temperature, and the aging temperature is used to equivalent the change degree of the training oil paper insulation material over time at the actual temperature, while the breakdown temperature is used to consider the insulation performance of the training sample when working at different actual temperatures.

[0102] S204: Obtain multiple experimental result sets according to different preset aging temperatures.

[0103] It should be noted that in order to avoid the randomness of the experimental results and increase the reliability of the experimental results, multiple experimental result sets are obtained in the present embodiment.

[0104] S205: Perform three-dimensional fitting on the multiple experimental result sets to obtain a target three-dimensional fitting equation set.

[0105] It should be noted that before step S205 is performed, the method can further include:

[0106] Each experimental result set is subjected to two-dimensional fitting with respect to the breakdown temperature and the breakdown harmonic frequency, and then all the two-dimensional fitting results are further subjected to three-dimensional fitting with respect to the aging time to obtain multiple three-dimensional fitting results, and the multiple three-dimensional fitting results are processed to obtain the target three-dimensional fitting equation set.

[0107] S206: Obtain a life assessment model according to the three-dimensional fitting equation set.

[0108] It should be noted that the life assessment model provided in the present embodiment can further be trained by inputting the training aging time, comparing the obtained assessment result with the actual result, adjusting the parameters of the life assessment model when the difference between the assessment result and the actual result is greater than a preset difference, and outputting the result until the output result meets the condition.

[0109] Based on the life evaluation method of the current transformer oil paper provided in the above embodiment, the determination process of the life evaluation model combined with the actual situation provided in the embodiment of the application can include:

[0110] Step one: high temperature aging treatment.

[0111] The equivalent aging time selected in the embodiment is 5 days, 10 days, 20 days, 30 days, and the unaged sample as a control group, wherein the high temperature aging temperature is set to 130 DEG C, and the oil paper insulation material used is the insulation oil of a 220 kV oil-immersed current transformer.

[0112] Step two: harmonic breakdown experiment.

[0113] In the embodiment, the harmonic frequency selected in the harmonic breakdown experiment is 100 Hz, 150 Hz, 250 Hz, 350 Hz, 450 Hz, 550 Hz, 650 Hz, 750 Hz, 850 Hz, 950 Hz, and 1000 Hz, and the breakdown temperature is 20 DEG C, 40 DEG C, 60 DEG C, and 80 DEG C, and three breakdown experiments are repeated under each condition.

[0114] When performing the harmonic breakdown experiment, the whole piece of the oil paper obtained by soaking the insulation oil subjected to the high temperature aging in step one is cut into a square small piece of about 20 mm*20 mm.

[0115] After waiting for the sample to reach the predetermined breakdown temperature, the thickness of the oil paper insulation sample is measured by using a micrometer and recorded, then the oil paper insulation sample is placed flat on the lower electrode, then the upper electrode is moved downward until the sample is pressed tightly with the lower electrode, the sample is placed back into the insulation oil tank, the output voltage frequency of the signal generator is adjusted, and the frequency is confirmed on the power amplifier screen, then the harmonic breakdown experiment is performed on the sample. At the moment when the sample is broken down, the protection indicator light will light up, and at this time the voltage reading on the screen is read.

[0116] Step three: determine the average value and standard deviation of the field strength under different aging temperatures corresponding to different aging times.

[0117] Referring to Tables 1.1-1.4, the breakdown data of the unaged sample under different harmonic frequencies at different breakdown temperatures is obtained according to Tables 1.1-1.4 Figure 3 The graph is a schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of the unaged sample provided in the embodiment of the application.

[0118] Table 1.1 Unaged sample 20 DEG C harmonic breakdown data

[0119]

[0120] Table 1.2 Breakdown data for unaged samples at 40°C

[0121]

[0122]

[0123] Table 1.3 Breakdown data for unaged samples at 60°C

[0124]

[0125] Table 1.4 Breakdown data for unaged samples at 80°C

[0126]

[0127]

[0128] Referring to Tables 2.1-2.4 below, breakdown data for unaged samples at different breakdown temperatures and different harmonic frequencies are shown. From Tables 2.1-2.4, the following is obtained: Figure 4 The figure is an average value and standard deviation of harmonic breakdown field strength of a 10-day aged sample provided in an embodiment of the present application.

[0129] Table 2.1 Breakdown data for 10-day aged samples at 20°C

[0130]

[0131] Table 2.2 Breakdown data for 10-day aged samples at 40°C

[0132]

[0133]

[0134] Table 2.3 Breakdown data for 10-day aged samples at 60°C

[0135]

[0136]

[0137] Table 2.4 Breakdown data for 10-day aged samples at 80°C

[0138]

[0139] Referring to Tables 3.1-3.4 below, breakdown data for unaged samples at different breakdown temperatures and different harmonic frequencies are shown. From Tables 3.1-3.4, the following is obtained: Figure 5 The figure is an average value and standard deviation of harmonic breakdown field strength of a 30-day aged sample provided in an embodiment of the present application.

[0140] Table 3.1 Harmonic breakdown data of 20℃ for 30-day aged samples

[0141]

[0142]

[0143] Table 3.2 Harmonic breakdown data of 40℃ for 30-day aged samples

[0144]

[0145] Table 3.3 Harmonic breakdown data of 60℃ for 30-day aged samples

[0146]

[0147]

[0148] Table 3.4 Harmonic breakdown data of 80℃ for 30-day aged samples

[0149]

[0150] It should be noted that only the tables and field strength average values and standard deviations corresponding to the unaged samples, 10-day aged samples and 30-day aged samples are shown in Step Two, and the 5-day aged samples and 20-day aged samples are not shown, but the same operation can be performed according to the processing process of the first three kinds of data, and this will not be repeated here.

[0151] Step Four: Two-dimensional fitting of experimental results.

[0152] Since the breakdown field strength of oil-paper insulation material at a specific aging time and temperature changes with frequency roughly in a linear relationship, linear fitting is adopted, and the unaged samples, 5-day aged samples, 10-day aged samples, 20-day aged samples and 30-day aged samples are fitted respectively, and the fitting results are shown in Tables 4-8 as follows:

[0153] Table 4 Two-dimensional fitting results of harmonic breakdown field strength of unaged samples

[0154]

[0155] Table 5 Two-dimensional fitting results of harmonic breakdown field strength of 5-day aged samples

[0156]

[0157] Table 6 Two-dimensional fitting results of harmonic breakdown field strength of 10-day aged samples

[0158]

[0159]

[0160] Table 7 Two-dimensional fitting results of harmonic breakdown field strength of samples aged for 20 days

[0161]

[0162] Table 8 Two-dimensional fitting results of harmonic breakdown field strength of samples aged for 30 days

[0163]

[0164] From the above Tables 4-8, it can be seen that, at the same aging time and temperature, the harmonic breakdown field strength of oil-paper insulation always decreases with the increase of harmonic frequency, i.e., the slope of linear fitting is negative.

[0165] From the fitting results, it can also be found that, at any aging time, the slope of fitting curve generally first increases and then decreases with the increase of temperature, while the intercept continuously decreases with the increase of temperature. This change indicates that temperature not only has a direct impact on the breakdown field strength, but also affects the correlation degree of harmonic frequency and breakdown field strength.

[0166] From the above Tables 4-8, it can be seen that, at 20℃ and 80℃, although there is a big gap in the breakdown field strength, the influence of harmonic frequency on the breakdown field strength is small, while the slope at 40℃ and 60℃ is obviously larger than the former two. By observing the two intermediate temperatures of 40℃ and 60℃, it can be found that, when the aging time is short (unaged and aged for 5 days), the slope of fitting curve at 60℃ is larger than that at 40℃, while when the aging time is long (aged for 10 days and above), the slope of fitting curve at 60℃ is smaller than that at 40℃. Moreover, when the aging time is 5 days or less, the mutual distinction of each fitting curve is relatively large, while when the aging time is 10 days or more, the fitting curves at 60℃ and 80℃ are relatively close. This indicates that the aging time also has a certain influence on the relationship between temperature and the slope of fitting curve.

[0167] By comparing the fitting curves of different aging times at the same temperature, it can be found that, at 20℃, the curve parameters are very close regardless of the aging time, indicating that the aging time has little effect on the harmonic breakdown field strength of oil-paper insulation at low temperature.

[0168] In summary, the harmonic breakdown field strength of oil-paper insulation always decreases with the increase of harmonic frequency and temperature, but the influence of aging time on the breakdown field strength is relatively complex, so in step five, the equation of harmonic breakdown field strength with respect to aging time, temperature and harmonic frequency is obtained by three-dimensional fitting to more accurately describe it.

[0169] Step five: three-dimensional fitting of the two-dimensional fitting results.

[0170] Since there is no reliable fitting method in the existing technology to directly fit three independent variables and one dependent variable, this embodiment first uses three-dimensional fitting to obtain the fitting surface and fitting equation of the harmonic breakdown field strength of the oil-paper insulation with respect to temperature and harmonic frequency under different aging times. After obtaining each parameter, the relationship between these parameters and aging time is then fitted in two dimensions, so that the target equation can be approximately obtained. The three-dimensional fitting results are shown in Tables 9 to 13.

[0171] Table 3.26 Three-dimensional fitting parameters of harmonic breakdown field strength of unaged samples

[0172]

[0173]

[0174] Table 3.27 Three-dimensional fitting parameters of harmonic breakdown field strength of samples aged for 5 days

[0175] Equation z = z0 + a * x + b * y + c * x 2 + d * y 2 ]]> ​ 68.15808±3.37828 a -0.70396±0.13184 b -0.0248±0.00786 c 0.0033±0.0013 d 7.87657E-6 ± 6.97148E-6 [R 2 (COD)]]> 0.9012 adjusted R 2 ]] 0.89107

[0176] Table 3.28 Three-dimensional fitting parameters of harmonic breakdown field strength of samples after 10 days of aging

[0177] Equation [z = z0 + a*x + b*y + c*x 2 +d*y 2 ]]> ​ 72.91998±2.46393 a -0.97001±0.09616 b -0.03465±0.00573 c 0.00553±9.46539E-4 d 1.86774E-5 ± 5.08461E-6 [R 2 (COD)]]> 0.95236 adjusted R 2 ]] 0.94748

[0178] Table 3.29 Three-dimensional fitting parameters of harmonic breakdown field strength of samples aged for 20 days

[0179]

[0180]

[0181] Table 3.30 Three-dimensional fitting parameters of harmonic breakdown field strength of samples aged for 30 days.

[0182] Equation z = z0 + a * x + b * y + c * x 2 + d * y 2 ]]> ​ 70.91491±3.53955 a -1.01253±0.13813 b -0.01068±0.00823 c 0.00488±0.00136 d 1.24199E-6 ± 7.30427E-6 [R 2 (COD)]]> 0.92837 adjusted R 2 ]] 0.92103

[0183] To facilitate subsequent fitting, when selecting the above three-dimensional fitting equation, we can choose an equation with a sufficiently high goodness of fit (Rfit). 2 The simplest equation when (larger) the surface area is reached. R5 for five sets of fitted surfaces. 2 All values ​​are around 0.9, and they can all reflect the trend of harmonic breakdown field strength of oil-paper insulation with temperature and harmonic frequency.

[0184] The selected three-dimensional fitting equation has five parameters. By extracting these five sets of fitting parameters individually and plotting them according to the aging time, we can obtain... Figure 6 As shown, this figure is a schematic diagram of the parameter curve of a three-dimensional fitting equation provided in an embodiment of this application.

[0185] Among them, combined Figure 6As shown, 5 parameters form an inflection point at 10 days, so a piecewise fitting method can be used, with 3 parameters for 0-10 days and 3 parameters for 10-30 days, and a quadratic equation is used for fitting, so that the fitting equation of the five parameters about the aging time can be obtained. The fitting parameter results are:

[0186] (1) 0-10 days:

[0187]

[0188] (2) 10-30 days:

[0189]

[0190] wherein D is the equivalent aging time, the time unit is day, and the original fitting equation z=z0+ax+by+cx+dy 2 2 , z0 can represent the initial field strength E0, x represents the temperature t, and y represents the harmonic frequency f, so the three-dimensional fitting equation of the harmonic breakdown field strength of the oil paper insulation about the aging time D, the temperature t and the harmonic frequency f can be expressed as:

[0191] (1) 0-10 days:

[0192]

[0193] (2) 10-30 days:

[0194]

[0195] The three-dimensional fitting equation obtained by the above formula is the equation obtained in the embodiment, and further packaging the three-dimensional fitting equation as a life evaluation model can determine the breakdown field strength of the current transformer oil paper under different aging times, that is, determine the service life of the current transformer oil paper.

[0196] Based on the life evaluation method of the current transformer oil paper provided in the above embodiment, the embodiment of the present application further provides a life evaluation device of the current transformer oil paper, referring to Figure 7 , which is a structure schematic diagram of a life evaluation device of the current transformer oil paper provided in the embodiment of the present application, and Figure 7 as shown, the device 700 provided in the embodiment of the present application can specifically include:

[0197] The test data determination module 701 is configured to determine the equivalent aging time, the test temperature and the test harmonic frequency of the current transformer oil paper to be detected.

[0198] ​The target breakdown field strength determination module 702 is configured to input the equivalent aging time, the test temperature, and the test harmonic frequency into a pre-trained life assessment model to obtain a target breakdown field strength.

[0199] The life assessment module 703 is configured to assess the life of the current transformer oil paper according to the target breakdown field strength.

[0200] As an example, the target breakdown field strength determination module 702 is specifically configured to:

[0201] determine an initial field strength and an initial coefficient according to the equivalent aging time through the pre-trained life assessment model;

[0202] determine the target breakdown field strength according to the test temperature, the test harmonic frequency, the initial field strength, and the initial coefficient.

[0203] As an example, the target breakdown field strength determination module 702 is specifically configured to:

[0204] when the equivalent aging time is greater than a preset inflection point time, input the equivalent aging time, the test temperature, and the test harmonic frequency into the pre-trained life assessment model to obtain a first target breakdown field strength;

[0205] when the equivalent aging time is less than the preset inflection point time, input the equivalent aging time, the test temperature, and the test harmonic frequency into the pre-trained life assessment model to obtain a second target breakdown field strength;

[0206] when the equivalent aging time is equal to the preset inflection point time, input the equivalent aging time, the test temperature, and the test harmonic frequency into the pre-trained life assessment model to obtain a third target breakdown field strength.

[0207] As an example, the life assessment model is specifically obtained by the following way:

[0208] The high-temperature aging processing module is configured to perform high-temperature aging processing on the training oil paper insulation material according to a preset aging temperature.

[0209] The training sample acquisition module is configured to use the processed training oil paper insulation material to manufacture a plurality of identical training samples.

[0210] The experimental result set determination module is configured to perform harmonic breakdown experiments on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and obtain a plurality of experimental results as an experimental result set.

[0211] The multiple sets of experimental result set determination module is configured to obtain multiple sets of experimental result sets according to different preset aging temperatures.

[0212] a three-dimensional fitting module configured to perform three-dimensional fitting on the multiple sets of experimental result sets to obtain a target three-dimensional fitting equation set;

[0213] a life evaluation model determination module configured to obtain a life evaluation model according to the three-dimensional fitting equation set.

[0214] The life evaluation device for the current transformer oil paper provided by the embodiments of the present application has the same beneficial effects as the life evaluation method for the current transformer oil paper provided by the above embodiments, and thus will not be described again.

[0215] The embodiments of the present application further provide a corresponding device and a computer storage medium for implementing the schemes provided by the embodiments of the present application.

[0216] The device includes a memory and a processor, the memory is configured to store instructions or codes, and the processor is configured to execute the instructions or codes to enable the device to perform the life evaluation method for the current transformer oil paper provided by any of the embodiments of the present application.

[0217] The computer storage medium stores codes, and when the codes are executed, the device executing the codes implements the life evaluation method for the current transformer oil paper provided by any of the embodiments of the present application.

[0218] It should be noted that each of the embodiments in the present specification is described in a progressive manner, and the same or similar parts of each of the embodiments can be referred to each other, and each of the embodiments mainly describes the difference from other embodiments. Especially, the device and equipment embodiments are basically similar to the method embodiments, so the description is relatively simple, and the relevant parts can be referred to the part of the method embodiments. The device and equipment embodiments described above are only schematic, and the units described as separate components can be or can not be physically separated, and the components prompted as units can be or can not be physical units, that is, they can be located in one place, or can be distributed on multiple network units. According to the actual needs, part or all of the modules can be selected to achieve the purpose of the embodiments of the present application. Those skilled in the art can understand and implement without creative labor.

[0219] The "first", "second" in the names mentioned in the embodiments of the present application are only used for name identification, and do not represent the first and second in order.

[0220] Those skilled in the art can clearly understand the above-mentioned all or part of the steps in the embodiment method can be realized by means of software and general hardware platform from the description of the above embodiments. Based on such understanding, the technical solutions of the present application can be embodied in the form of software products. The computer software product can be stored in a storage medium, such as a read-only memory (English: read-only memory, ROM) / RAM, a magnetic disk, an optical disk, etc., and includes a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network communication device such as a router) execute the method described in various embodiments or some parts of the embodiments of the present application.

[0221] The above is only one specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for assessing the lifespan of the oil paper in a current transformer, characterized in that, The method includes: Determine the equivalent aging time, test temperature, and test harmonic frequency of the oil paper of the current transformer to be tested; The equivalent aging time, test temperature, and test harmonic frequency are input into a pre-trained lifetime assessment model to obtain the target breakdown field strength, including: The pre-trained lifetime assessment model includes a first lifetime assessment equation and / or a second lifetime assessment equation; the first lifetime assessment equation is different from the second lifetime assessment equation; the inflection point in the preset inflection point time is the inflection point between the fitting parameters and time corresponding to the pre-trained lifetime assessment model. When the equivalent aging time is greater than the preset inflection point time, the equivalent aging time, test temperature and test harmonic frequency are input into the first lifetime assessment equation to obtain the first target breakdown field strength. When the equivalent aging time is less than the preset inflection point time, the equivalent aging time, test temperature and test harmonic frequency are input into the second lifetime assessment equation to obtain the second target breakdown field strength. When the equivalent aging time is equal to the preset inflection point time, the equivalent aging time, test temperature and test harmonic frequency are input into the first lifetime assessment equation or the second lifetime assessment equation to obtain the third target breakdown field strength. The lifespan of the current transformer oil paper is evaluated based on the target breakdown field strength; wherein the target breakdown field strength is the first target breakdown field strength, the second target breakdown field strength, or the third target breakdown field strength.

2. The method according to claim 1, characterized in that, The step of inputting the equivalent aging time, test temperature, and test harmonic frequency into a pre-trained lifetime assessment model to obtain the target breakdown field strength includes: The initial field strength and initial coefficients are determined based on the equivalent aging time using the pre-trained lifetime assessment model. The target breakdown field strength is determined based on the test temperature, test harmonic frequency, initial field strength, and initial coefficient.

3. The method according to claim 1, characterized in that, The life assessment model is obtained in the following way: The training oil-paper insulation material was subjected to high-temperature aging treatment at a preset aging temperature. Multiple identical training samples were made using the treated training paper insulation material. Harmonic breakdown experiments were conducted on each training sample at different breakdown temperatures and breakdown harmonic frequencies, and multiple experimental results were obtained as an experimental result set. Multiple sets of experimental results were obtained according to different preset aging temperatures; The multiple sets of experimental results are subjected to three-dimensional fitting to obtain the target three-dimensional fitting equation set; The life assessment model is obtained based on the three-dimensional fitting equations.

4. A device for assessing the lifespan of current transformer oil paper, characterized in that, The device includes: The test data determination module is used for: Determine the equivalent aging time, test temperature, and test harmonic frequency of the oil paper of the current transformer to be tested; The target breakdown field strength determination module is used to input the equivalent aging time, test temperature, and test harmonic frequency into a pre-trained lifetime assessment model to obtain the target breakdown field strength, including: The pre-trained lifetime assessment model includes a first lifetime assessment equation and / or a second lifetime assessment equation; the first lifetime assessment equation is different from the second lifetime assessment equation; the inflection point in the preset inflection point time is the inflection point between the fitting parameters and time corresponding to the pre-trained lifetime assessment model. When the equivalent aging time is greater than the preset inflection point time, the equivalent aging time, test temperature and test harmonic frequency are input into the first lifetime assessment equation to obtain the first target breakdown field strength. When the equivalent aging time is less than the preset inflection point time, the equivalent aging time, test temperature and test harmonic frequency are input into the second lifetime assessment equation to obtain the second target breakdown field strength. When the equivalent aging time is equal to the preset inflection point time, the equivalent aging time, test temperature and test harmonic frequency are input into the first lifetime assessment equation or the second lifetime assessment equation to obtain the third target breakdown field strength. The life assessment module is used for: The lifespan of the current transformer oil paper is evaluated based on the target breakdown field strength; wherein the target breakdown field strength is the first target breakdown field strength, the second target breakdown field strength, or the third target breakdown field strength.

5. The apparatus according to claim 4, characterized in that, The target breakdown field strength determination module is specifically used for: The initial field strength and initial coefficients are determined based on the equivalent aging time using the pre-trained lifetime assessment model. The target breakdown field strength is determined based on the test temperature, test harmonic frequency, initial field strength, and initial coefficient.

6. The apparatus according to claim 4, characterized in that, The life assessment model is obtained in the following way: The high-temperature aging treatment module is used to perform high-temperature aging treatment on the training oil paper insulation material according to the preset aging temperature. The training sample acquisition module is used to create multiple identical training samples using the processed training oil paper insulation material. The experimental result set determination module is used to conduct harmonic breakdown experiments on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and obtain multiple experimental results as an experimental result set. The module for determining multiple sets of experimental results is used to obtain multiple sets of experimental results according to different preset aging temperatures. The three-dimensional fitting module is used to perform three-dimensional fitting on the multiple sets of experimental results to obtain the target three-dimensional fitting equation system. The life assessment model determination module is used to obtain the life assessment model based on the three-dimensional fitting equation system.

7. A computer device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the life assessment method for current transformer oil paper as described in any one of claims 1-3.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions that, when executed on a terminal device, cause the terminal device to perform the life assessment method for current transformer oil paper as described in any one of claims 1-3.

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