CN116087723A - Method, device, equipment and medium for evaluating service life of current transformer oilpaper - Google Patents

Abstract

The application discloses a life evaluation method, device, equipment and medium of oil paper of a current transformer. The method includes: obtaining the oil paper of the current transformer to be detected, determining the equivalent aging time, the test temperature and the test harmonic frequency of the current transformer oil paper, and inputting the equivalent aging time, the test temperature and the test harmonic frequency into the pre-trained life The evaluation model obtains the target breakdown field strength, and the life of the current transformer oil paper is evaluated according to the target breakdown field strength. Among them, by determining the target breakdown field strength through the pre-trained life evaluation model, the insulation performance of the current transformer oil paper can be determined. At the same time, if the target breakdown field strength is equal to the preset value, the target breakdown field strength corresponding to The equivalent aging time is used as the service life of the current transformer oil paper to realize the life evaluation of the current transformer oil paper, avoid the failure of the insulation performance of the current transformer oil paper due to aging due to factors such as time and temperature, and ensure the safety of the current transformer sex and stability.

Description

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

Technical Field

The present application relates to the technical field of oil-paper detection, and in particular to a method, device, equipment and medium for evaluating the life of oil-paper of a current transformer.

Background Art

With the development of power systems, in order to ensure the safety and reliability of power systems, current transformers are generally used to measure and protect power systems.

In the prior art, current transformers can be divided into dry-type current transformers, gas-insulated current transformers and oil-immersed current transformers. Among them, the heat dissipation medium of the oil-immersed current transformer is transformer oil. The heat generated during its operation is conducted to the metal casing through the transformer oil. Therefore, the oil-immersed current transformer has the advantages of uniform heat conduction, fast heat dissipation, and good insulation performance recovery. In addition, due to its simple structure, low manufacturing cost, high reliability and other advantages, the oil-immersed current transformer has been widely used in power systems.

Since the quality of the current transformer oil paper, the main insulation in the oil-immersed current transformer, will affect the normal use of the oil-immersed current transformer, and at the same time, the insulation strength of the current transformer oil paper will continue to decline due to various factors, which will correspondingly 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. However, 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 applications, it is impossible to evaluate the service life of the current transformer oil paper.

Based on this, how to effectively realize the life evaluation of the oil-paper of the current transformer is a technical problem that needs to be solved urgently by those skilled in the art.

Summary of the invention

Based on the above problems, the present application provides a method, device, equipment and medium for evaluating the life of oil-paper of a current transformer, so as to achieve effective life evaluation of the oil-paper of a current transformer.

The embodiments of the present application disclose the following technical solutions:

In a first aspect, an embodiment of the present application provides a method for evaluating the life of an oil-paper of a current transformer, the method comprising:

Determine the equivalent aging time, test temperature and test harmonic frequency of the oil-paper of the current transformer to be tested;

Inputting the equivalent aging time, test temperature and test harmonic frequency into a pre-trained life assessment model to obtain a target breakdown field strength;

The life of the oil-paper of the current transformer is evaluated according to the target breakdown field strength.

Optionally, the inputting 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 comprises:

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

The target breakdown field strength is determined according to the test temperature, the test harmonic frequency, the initial field strength and the initial coefficient.

Optionally, the inputting 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 comprises:

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

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

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

Optionally, the lifespan assessment model is obtained in the following manner:

Perform high temperature aging treatment on the training oil-paper insulation material according to the preset aging temperature;

Using the processed training oil-paper insulation material to prepare multiple identical training samples;

Perform a harmonic breakdown experiment on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and obtain multiple experimental results as an experimental result set;

Multiple sets of experimental results are obtained according to different preset aging temperatures;

Performing three-dimensional fitting on the multiple sets of experimental result sets to obtain a target three-dimensional fitting equation set;

A life assessment model is obtained according to the three-dimensional fitting equation group.

In a second aspect, an embodiment of the present application provides a device for evaluating the life of an oil-paper of a current transformer, the device comprising:

A test data determination module, used to determine the equivalent aging time, test temperature and test harmonic frequency of the oil-paper of the current transformer to be tested;

A target breakdown field strength determination module is used to input the equivalent aging time, test temperature and test harmonic frequency into a pre-trained life assessment model to obtain a target breakdown field strength;

The life evaluation module is used to evaluate the life of the oil-paper of the current transformer according to the target breakdown field strength.

Optionally, the target breakdown field strength determination module is specifically used to:

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

The target breakdown field strength is determined according to the test temperature, the test harmonic frequency, the initial field strength and the initial coefficient.

Optionally, the target breakdown field strength determination module is specifically used to:

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

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

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

Optionally, the lifespan assessment model is obtained in the following manner:

High temperature aging treatment module, used to perform high temperature aging treatment on the training oil-paper insulation material according to the preset aging temperature;

A training sample acquisition module is used to prepare a plurality of identical training samples using the processed training oil-paper insulation material;

An experimental result set determination module is used to perform a harmonic breakdown experiment on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and obtain multiple experimental results as an experimental result set;

A module for determining multiple sets of experimental result sets, used to obtain multiple sets of experimental result sets according to different preset aging temperatures;

A three-dimensional fitting module, used for performing three-dimensional fitting on the multiple sets of experimental results to obtain a target three-dimensional fitting equation group;

The life assessment model determination module is used to obtain the life assessment model according to the three-dimensional fitting equation group.

In a third aspect, an embodiment of the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the life assessment method of the oil-paper of the current transformer as described in the first aspect is implemented.

In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, in which instructions are stored. When the instructions are executed on a terminal device, the terminal device executes the life assessment method of the current transformer oil paper as described in the first aspect.

Compared with the prior art, this application has the following beneficial effects:

The present application obtains the current transformer oil paper to be tested, 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 the pre-trained life assessment model to obtain the target breakdown field strength, and evaluates the life of the current transformer oil paper according to the target breakdown field strength. Among them, 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. At the same time, if the target breakdown field strength is equal to the preset value, it is considered that the current transformer oil paper corresponding to the target breakdown field strength needs to be replaced, so as to realize the life assessment of the current transformer oil paper, avoid the failure caused by the insulation performance of the current transformer oil paper due to aging due to factors such as time and temperature, and ensure the safety and stability of the current transformer.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

FIG1 is a flow chart of a method for evaluating the life of oil-paper of a current transformer provided in an embodiment of the present application;

FIG2 is a flow chart of a method for determining a life assessment model provided in an embodiment of the present application;

3 is a schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of an unaged sample provided in an embodiment of the present application;

FIG4 is a schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of a sample aged for 10 days provided in an embodiment of the present application;

FIG5 is a schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of a sample aged for 30 days provided in an embodiment of the present application;

FIG6 is a schematic diagram of a parameter curve diagram of a three-dimensional fitting equation provided in an embodiment of the present application;

FIG. 7 is a schematic diagram of the structure of a current transformer oil-paper life assessment device provided in an embodiment of the present application.

DETAILED DESCRIPTION

As described above, in the study of current transformer oil paper, it was found that in the prior art, current transformers can be divided into dry current transformers, gas insulated current transformers and oil-immersed current transformers. Among them, the heat dissipation medium of the oil-immersed current transformer is transformer oil. The heat generated during its operation is conducted to the metal casing through the transformer oil. Therefore, the oil-immersed current transformer has the advantages of uniform heat conduction, fast heat dissipation, and good insulation performance recovery. Due to its simple structure, low manufacturing cost, high reliability and other advantages, the oil-immersed current transformer has been widely used in power systems.

Since the quality of the current transformer oil paper, the main insulation in the oil-immersed current transformer, will affect the normal use of the oil-immersed current transformer, and at the same time, the insulation strength of the current transformer oil paper will continue to decline due to various factors, which will correspondingly 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. However, 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 applications, it is impossible to evaluate the service life of the current transformer oil paper.

In order to solve the above problems, the embodiments of the present application provide a method, device, equipment and medium for evaluating the life of a current transformer oil paper. The method comprises: obtaining a current transformer oil paper to be tested, 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.

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 assessment model. At the same time, if the target breakdown field strength is equal to the preset value, it is considered that the current transformer oil paper corresponding to the target breakdown field strength needs to be replaced, thereby realizing the life assessment of the current transformer oil paper, avoiding failures caused by aging of the insulation performance of the current transformer oil paper due to factors such as time and temperature, and ensuring the safety and stability of the current transformer.

In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

Referring to FIG. 1 , which is a flow chart of a method for evaluating the life of a current transformer oil-paper according to an embodiment of the present application, in combination with FIG. 1 , the method for evaluating the life of a current transformer oil-paper according to an embodiment of the present application may include:

S101: Determine the equivalent aging time, test temperature and test harmonic frequency of the oil-paper of the current transformer to be tested.

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

It should be noted that, in this embodiment, the current transformer described in the embodiment of the present application refers to a 220kV oil-immersed current transformer.

The equivalent aging time refers to the time obtained by calculating the actual service life through high-temperature aging.

Specifically, in an achievable implementation, the thermal aging time under experimental conditions can be made to correspond to the operating time of the current transformer oil paper under actual conditions according to the Arrhenius steady-state temperature acceleration model, and the aging acceleration factor is first calculated according to the following formula:

Where _T0 is the actual operating temperature, T is the aging temperature, _Ea is the chemical activation energy, k is the Boltzmann constant (1.380649× ^10-23 J/K), and AF is the accelerated aging factor.

Since the insulation of the current transformer works normally at a maximum temperature of 80°C and the maximum temperature of a fault does not exceed 110°C, the aging time multiplied by the accelerated aging factor equals the actual operating time of the oil-paper insulation of the current transformer. The chemical activation energy of oil-paper insulation is generally 80-100 kJ/mol, and the conservative value is 80 kJ/mol. The aging acceleration factor is calculated to be: AF = 28.72. The corresponding relationship between the aging time and the actual operating time is shown in Table 1 below:

Table 1 Correspondence between aging time and actual running time

130℃ aging time (days) 0 5 10 20 30 80℃ Actual operating time (month) 0 4.79 9.57 19.15 28.72

Test temperature refers to the temperature at which the current transformer oil paper is tested.

The test harmonic frequency refers to the harmonic frequency when the oil-paper breakdown test of the current transformer is carried out.

It should be noted that the test temperature described in the embodiments of the present application refers to the breakdown temperature during the harmonic breakdown experiment, and does not refer to the aging temperature during high-temperature aging.

It should be noted that in the embodiment of the present application, the actual usage time of the current transformer is obtained, and then the actual usage time is equated with the aging time at a preset temperature. By replacing the actual usage time 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 applications is avoided.

S102: Inputting the equivalent aging time, test temperature and test harmonic frequency into a pre-trained life assessment model to obtain a target breakdown field strength.

The pre-trained life assessment model refers to a model that has been trained in advance and can assess the service life of the oil paper of the current transformer.

It should be noted that under the action of a strong electric field, the solid dielectric loses its electrical insulation ability and suddenly changes from an insulating state to a good conductive state, resulting in breakdown. The minimum critical voltage is called the 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 (referred to as the breakdown field strength, also known as dielectric strength), which reflects the electrical strength of the solid dielectric itself (that is, the degree of insulation). Therefore, in this 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 tested is qualified, and its service life can be further evaluated.

As a feasible implementation, step S102 may include:

Step 11: Determine the initial field strength and initial coefficient according to the equivalent aging time through the pre-trained life assessment model.

Step 12: Determine the target breakdown field strength according to the test temperature, test harmonic frequency, initial field strength and initial coefficient.

It should be noted that the target breakdown field strength corresponding to the actual usage time can be determined according to the equivalent aging time, and the pre-trained life assessment model can be used to further predict the service life of the oil-paper of the current transformer. For example, if the equivalent aging time corresponding to the usage time of 11 years is 11 days, the test temperature is 30°C, and the test harmonic frequency is 200Hz, the target breakdown field strength obtained is E=49kV*mm ^-1 , and the preset breakdown field strength is 35kV*mm ^-1 . Then, the target breakdown field strength when the usage time is 20 years can be further predicted, thereby realizing the life assessment of the oil-paper of the current transformer.

It should be noted that, in the embodiment of the present application, the step S102 may further include:

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

Step 22: When the equivalent aging time is less than the preset inflection point time, the equivalent aging time, the test temperature and the test harmonic frequency are input into a pre-trained life assessment model to obtain a second target breakdown field strength;

Step 23: When the equivalent aging time is equal to the preset inflection point time, the equivalent aging time, the test temperature and the test harmonic frequency are input into the pre-trained life assessment model to obtain a third target breakdown field strength.

It should be noted that, as a feasible implementation method, in the embodiment of the present application, the equivalent aging time range is set to [0,30] days. Furthermore, in the process of determining the life assessment model, by fitting the experimental results, when the equivalent aging time is 10 days, an inflection point will appear in the fitting results. Therefore, different fitting equations are set based on the inflection point time to make the life assessment model more accurate.

It should be noted that when the equivalent aging time is greater than the preset inflection point time, the first life assessment 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 assessment 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 assessment equation or the second life assessment equation can be used to determine the third target breakdown field strength, or the first life assessment equation and the second life assessment equation can be 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.

S103: Evaluate the life of the oil-paper of the current transformer according to the target breakdown field strength.

It should be noted that by obtaining the target breakdown field strength, the insulation strength of the current transformer oil paper under actual usage time can be determined. By comparing the target breakdown field strength with the preset breakdown field strength, it can be determined whether the insulation performance of the current transformer oil paper is qualified. If it is unqualified, it needs to be replaced. If it is qualified, the new equivalent aging time corresponding to the preset usage time can be further determined according to the equivalent aging time corresponding to the actual usage time, and the life of the power transformer oil paper can be evaluated.

In a feasible implementation, after determining the equivalent aging time and target breakdown field strength corresponding to the actual usage time of the current transformer oil paper, the target breakdown field strength corresponding to the new continuous equivalent aging time can be further predicted based on the equivalent aging time and target breakdown field strength, and a curve graph of the equivalent aging time and target breakdown field strength can be generated, thereby evaluating and predicting the life of the current transformer oil paper.

The life assessment method of the current transformer oil paper provided in the embodiment of the present application obtains the current transformer oil paper to be tested, 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 the pre-trained life assessment model to obtain the target breakdown field strength, and evaluates the life of the current transformer oil paper according to the target breakdown field strength. Among them, 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. At the same time, if the target breakdown field strength is equal to the preset value, it is considered that the current transformer oil paper corresponding to the target breakdown field strength needs to be replaced, so as to realize the life assessment of the current transformer oil paper, avoid the failure caused by the insulation performance of the current transformer oil paper due to aging due to factors such as time and temperature, and ensure the safety and stability of the current transformer.

Based on the life assessment method of the oil-paper of the current transformer provided in the above embodiment, the embodiment of the present application further provides a method for determining a life assessment model. Referring to FIG. 2 , which is a flow chart of a method for determining a life assessment model provided in the embodiment of the present application, in combination with FIG. 2 , the method for determining a life assessment model provided in the embodiment of the present application may specifically include:

S201: performing high temperature aging treatment on the training oil-paper insulation material according to a preset aging temperature.

Training oil-paper insulation material refers to the insulating oil material used to make current transformer oil paper.

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

S202: Using the processed training oil-paper insulation material to create a plurality of identical training samples.

The training samples refer to oil paper made from processed training oil-paper insulation materials.

It should be noted that in this embodiment, the insulation performance of the training oil-paper insulation material that has been aged at high temperature needs to be evaluated. Therefore, it is necessary to use the training oil-paper insulation material that has been aged at high temperature to make training samples and perform harmonic breakdown experiments on the training samples.

S203: Performing a harmonic breakdown experiment on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and obtaining a plurality of experimental results as an experimental result set.

It should be noted that in this embodiment, during the harmonic breakdown experiment, the temperature under actual working conditions must also be considered, so the impact of the breakdown temperature on the breakdown of the training sample needs to be considered. Among them, the aging temperature and the breakdown temperature in the above-mentioned high-temperature aging treatment are not the same temperature. The aging temperature is to equivalently train the degree of change of the oil-paper insulation material over time at the actual temperature, while the breakdown temperature is to consider the insulation performance of the training sample when working at different actual temperatures.

S204: Obtain multiple groups of experimental result sets according to different preset aging temperatures.

It should be noted that in order to avoid the contingency of the experimental results and increase the reliability of the experimental results, multiple sets of experimental results will be obtained in this embodiment.

S205: Perform three-dimensional fitting on the multiple sets of experimental result sets to obtain a target three-dimensional fitting equation group.

It should be noted that, before executing step S205, the method may further include:

Each experimental result set is subjected to two-dimensional fitting results on breakdown temperature and breakdown harmonic frequency respectively, and then all two-dimensional fitting results are further subjected to three-dimensional fitting with aging time to obtain multiple three-dimensional fitting results, which are then processed to obtain a target three-dimensional fitting equation group.

S206: Obtaining a lifespan assessment model according to the three-dimensional fitting equation group.

It should be noted that the life assessment model provided in the embodiment of the present application can further input the training aging time, and then compare the obtained assessment result with the actual result. When the difference between the assessment result and the actual result is greater than the preset difference, it is necessary to further adjust the parameters of the life assessment model until the output result meets the conditions to complete the training of the life assessment model.

Based on the life assessment method of the current transformer oil-paper provided in the above embodiment, the embodiment of the present application further provides a process for determining a life assessment model in combination with actual conditions, and the determination process may include:

Step 1: High temperature aging treatment.

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

Step 2: Harmonic breakdown experiment.

In this embodiment, the harmonic frequencies selected for the harmonic breakdown experiment are 100Hz, 150Hz, 250Hz, 350Hz, 450Hz, 550Hz, 650Hz, 750Hz, 850Hz, 950Hz, and 1000Hz, and the breakdown temperatures are 20°C, 40°C, 60°C, and 80°C. The breakdown experiment is repeated three times under each condition.

When conducting a harmonic breakdown test, the whole piece of oil paper soaked in the high-temperature aged insulating oil in step 1 needs to be cut into small square samples of about 20mm*20mm.

After the sample reaches the predetermined breakdown temperature, use a micrometer to measure the thickness of the oil-paper insulation sample and record it, then place the oil-paper insulation sample flat on the lower electrode, then move the upper electrode downward until it is pressed together with the lower electrode to compact the sample, put the stage back into the insulating oil tank, adjust the output voltage frequency of the signal generator, confirm that the frequency is correct on the power amplifier screen, and then perform a harmonic breakdown test on the sample. At the moment the sample is broken down, the protection indicator light will light up, and the voltage indication on the screen will be read at this time.

Step 3: Determine the mean and standard deviation of the field strength at different aging temperatures corresponding to different aging times.

Refer to the following Tables 1.1 to 1.4, which are the breakdown data of the unaged samples at different harmonic frequencies at different breakdown temperatures. According to Tables 1.1 to 1.4, Figure 3 is finally obtained, which is a schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of an unaged sample provided in an embodiment of the present application.

Table 1.1 Harmonic breakdown data of unaged samples at 20°C

Table 1.2 Harmonic breakdown data of unaged samples at 40°C

Table 1.3 Harmonic breakdown data of unaged samples at 60°C

Table 1.4 Harmonic breakdown data of unaged samples at 80℃

Refer to Tables 2.1 to 2.4 below, which are breakdown data of unaged samples at different harmonic frequencies at different breakdown temperatures. Based on Tables 2.1 to 2.4, Figure 4 is finally obtained, which is a schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of a sample aged for 10 days provided in an embodiment of the present application.

Table 2.1 Harmonic breakdown data of samples aged for 10 days at 20°C

Table 2.2 Harmonic breakdown data of samples aged for 10 days at 40°C

Table 2.3 Harmonic breakdown data of samples aged for 10 days at 60°C

Table 2.4 Harmonic breakdown data of samples aged for 10 days at 80°C

See Tables 3.1 to 3.4 below, which are breakdown data of unaged samples at different harmonic frequencies at different breakdown temperatures. Based on Tables 3.1 to 3.4, Figure 5 is finally obtained, which is a schematic diagram of the average value and standard deviation of the harmonic breakdown field strength of a sample aged for 30 days provided in an embodiment of the present application.

Table 3.1 Harmonic breakdown data of samples aged for 30 days at 20°C

Table 3.2 Harmonic breakdown data of samples aged for 30 days at 40°C

Table 3.3 Harmonic breakdown data of samples aged for 30 days at 60°C

Table 3.4 Harmonic breakdown data of samples aged for 30 days at 80°C

It should be noted that in step 2, only the tables and field strength average values and standard deviations corresponding to the unaged samples, samples aged for 10 days and samples aged for 30 days are displayed. The samples aged for 5 days and samples aged for 20 days are not displayed, but the same operations can be performed according to the first three data processing processes, which will not be repeated here.

Step 4: Perform two-dimensional fitting on the experimental results.

Since the breakdown field strength of oil-paper insulation material under specific aging days and temperature roughly conforms to the linear relationship with frequency, linear fitting is used to fit the unaged sample, the sample aged for 5 days, the sample aged for 10 days, the sample aged for 20 days and the sample aged for 30 days. The fitting results are shown in the following Tables 4 to 8:

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

Table 5 Two-dimensional fitting results of harmonic breakdown field strength of samples aged for 5 days

Table 6 Two-dimensional fitting results of harmonic breakdown field strength of samples aged for 10 days

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

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

It can be seen from Tables 4 to 8 above that under the same aging days and temperature, the harmonic breakdown field strength of oil-paper insulation always decreases with the increase of harmonic frequency, that is, the slope of the linear fit is negative.

It can also be found from the fitting results that under any aging days, the slope of the fitting curve generally increases first and then decreases with the increase of temperature, while the intercept continues to decrease with the increase of temperature. This change shows that temperature not only has a direct impact on the breakdown field strength, but also affects the correlation between the harmonic frequency and the breakdown field strength.

From Tables 4 to 8 above, we can see that at 20℃ and 80℃, although there is a big difference in the breakdown field strength, the harmonic frequency has little effect on the breakdown field strength, and the slope at 40℃ and 60℃ is significantly greater than the former two. Looking at the two intermediate temperatures of 40℃ and 60℃, we can find that when the aging time is short (no aging and aging for 5 days), the slope of the fitting curve at 60℃ is greater than that at 40℃; and when the aging time is long (aging for 10 days and above), the slope of the fitting curve at 60℃ is less than that at 40℃. And when the aging days are 5 days or less, the different degrees of distinction between the fitting curves are relatively large; when the aging is 10 days or more, the fitting curves at 60℃ and 80℃ are relatively close. This shows that the aging time also has a certain influence on the relationship between temperature and the slope of the fitting curve.

By comparing the fitting curves of different aging times at the same temperature, it can be found that at 20°C, regardless of the aging days, the curve parameters are very close, indicating that the aging days have no obvious effect on the harmonic breakdown field strength of oil-paper insulation at low temperatures.

In summary, the harmonic breakdown field strength of oil-paper insulation always decreases with the increase of harmonic frequency and temperature. However, the effect of aging days on the breakdown field strength is more complicated. Therefore, in step five, the equation of the harmonic breakdown field strength with respect to aging time, temperature and harmonic frequency is obtained through three-dimensional fitting to describe it more accurately.

Step 5: Perform three-dimensional fitting on the two-dimensional fitting results.

Since there is no reliable fitting method in the prior art to directly fit three independent variables and one dependent variable, in this embodiment, three-dimensional fitting is first used to obtain the fitting surface and fitting equation of the oil-paper insulation harmonic breakdown field strength with respect to temperature and harmonic frequency at different aging times, and after obtaining various parameters, two-dimensional fitting is performed on the relationship between these parameters and aging time, so that the target equation can be approximately obtained. The three-dimensional fitting results are shown in Tables 9 to 13.

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

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

equation z＝z ₀ +a*x+b*y+c*x ² +d*y ² z ₀ 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 ^R2 (COD) 0.9012 Adjusted ^R2 0.89107

Table 3.28 Three-dimensional fitting parameters of harmonic breakdown field strength of samples aged for 10 days

equation z＝z ₀ +a*x+b*y+c*x ² +d*y ² z ₀ 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 ^R2 (COD) 0.95236 Adjusted ^R2 0.94748

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

Table 3.3 Three-dimensional fitting parameters of harmonic breakdown field strength of samples aged for 30 days

equation z＝z ₀ +a*x+b*y+c*x ² +d*y ² z ₀ 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 ^R2 (COD) 0.92837 Adjusted ^R2 0.92103

In order to facilitate the subsequent fitting, when selecting the above three-dimensional fitting equation, the simplest equation with a high enough fitting degree (large R ² ) can be selected. The R ² of the five groups of fitting surfaces are all around 0.9, and they can well reflect the variation trend of the harmonic breakdown field strength of oil-paper insulation with temperature and harmonic frequency.

The selected three-dimensional fitting equation has a total of 5 parameters. Five groups of fitting parameters are extracted separately and plotted according to the aging time, as shown in Figure 6, which is a schematic diagram of a parameter curve diagram of a three-dimensional fitting equation provided in an embodiment of the present application.

As shown in Figure 6, all five parameters form an inflection point at 10 days, so we can use the segmented fitting method to fit three parameters in a group of 0-10 days and three parameters in a group of 10-30 days, respectively, using quadratic equations to fit, and we can approximate the fitting equations of the five parameters about the aging time. The fitting parameter results are:

(1) 0-10 days:

(2) 10-30 days:

Where D is the equivalent aging time, the time unit is day. Combined with the original fitting equation z=z ₀ +ax+by+cx ² +dy ² , z ₀ can be expressed as the initial field strength E ₀ , x represents temperature t, y represents harmonic frequency f, and the three-dimensional fitting equation of the harmonic breakdown field strength of oil-paper insulation with respect to aging time D, temperature t and harmonic frequency f can be expressed as follows:

(1) 0-10 days:

(2) 10-30 days:

The three-dimensional fitting equation obtained by the above formula is the desired equation of this embodiment. The above three-dimensional fitting equation is further encapsulated as a life assessment model to determine the breakdown field strength of the current transformer oil paper corresponding to different aging times, that is, to determine the service life of the current transformer oil paper.

Based on the life assessment method of the current transformer oil-paper provided in the above embodiment, the embodiment of the present application further provides a life assessment device for the current transformer oil-paper. Referring to FIG. 7 , the figure is a structural schematic diagram of a life assessment device for the current transformer oil-paper provided in the embodiment of the present application. In combination with FIG. 7 , the device 700 provided in the embodiment of the present application may specifically include:

The test data determination module 701 is used to determine the equivalent aging time, test temperature and test harmonic frequency of the oil-paper of the current transformer to be tested;

A target breakdown field strength determination module 702 is used to input the equivalent aging time, test temperature and test harmonic frequency into a pre-trained life assessment model to obtain a target breakdown field strength;

The life evaluation module 703 is used to evaluate the life of the oil-paper of the current transformer according to the target breakdown field strength.

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

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

The target breakdown field strength is determined according to the test temperature, the test harmonic frequency, the initial field strength and the initial coefficient.

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

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

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

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

As an example, the life assessment model is obtained in the following manner:

High temperature aging treatment module, used to perform high temperature aging treatment on the training oil-paper insulation material according to the preset aging temperature;

A training sample acquisition module is used to prepare a plurality of identical training samples using the processed training oil-paper insulation material;

An experimental result set determination module is used to perform a harmonic breakdown experiment on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and obtain multiple experimental results as an experimental result set;

A module for determining multiple sets of experimental result sets, used to obtain multiple sets of experimental result sets according to different preset aging temperatures;

A three-dimensional fitting module, used for performing three-dimensional fitting on the multiple sets of experimental results to obtain a target three-dimensional fitting equation group;

The life assessment model determination module is used to obtain the life assessment model according to the three-dimensional fitting equation group.

The life assessment device for oil-paper of a current transformer provided in the embodiment of the present application has the same beneficial effects as the life assessment method for oil-paper of a current transformer provided in the above embodiment, and therefore will not be described in detail.

The embodiments of the present application also provide corresponding devices and computer storage media for implementing the solutions provided by the embodiments of the present application.

The device includes a memory and a processor, the memory is used to store instructions or codes, and the processor is used to execute the instructions or codes so that the device executes the life assessment method of current transformer oil paper described in any embodiment of the present application.

The computer storage medium stores codes, and when the codes are executed, the device executing the codes implements the life assessment method of oil-paper of a current transformer as described in any embodiment of the present application.

It should be noted that each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device and equipment embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments. The device and equipment embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components indicated as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. A person of ordinary skill in the art can understand and implement it without paying creative labor.

The "first" and "second" in the names such as "first" and "second" (if any) mentioned in the embodiments of the present application are only used as name identifiers and do not represent the first or second in order.

Through the description of the above implementation methods, it can be known that those skilled in the art can clearly understand that all or part of the steps in the above-mentioned embodiment method can be implemented by means of software plus a general hardware platform. Based on such an understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a storage medium, such as a read-only memory (ROM)/RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network communication device such as a router) to execute the methods described in each embodiment of the present application or some parts of the embodiments.

The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (10)

1. A method for lifetime assessment of current transformer oilpaper, the method comprising:

determining equivalent aging time, test temperature and test harmonic frequency of the current transformer oilpaper to be detected;

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 intensity;

and evaluating the service life of the current transformer oilpaper according to the target breakdown field intensity.

2. The method of claim 1, wherein said inputting the equivalent aging time, test temperature, and test harmonic frequency into a pre-trained life assessment model to obtain a target breakdown field strength comprises:

determining initial field intensity and initial coefficient according to the equivalent aging time through the pre-trained life assessment model;

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

3. The method of claim 1, wherein said inputting the equivalent aging time, test temperature, and test harmonic frequency into a pre-trained life assessment model to obtain a target breakdown field strength comprises:

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

When the equivalent aging time is smaller than the preset inflection point time, inputting the equivalent aging time, the test temperature and the test harmonic frequency into a pre-trained life evaluation model to obtain a second target breakdown field intensity;

and 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 a pre-trained life evaluation model to obtain a third target breakdown field intensity.

4. The method according to claim 1, characterized in that the lifetime assessment model is obtained in particular by:

carrying out high-temperature aging treatment on the training oilpaper insulating material according to a preset aging temperature;

manufacturing a plurality of identical training samples by using the treated training oilpaper insulating material;

carrying out harmonic breakdown experiments on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and taking a plurality of experimental results as an experimental result set;

obtaining a plurality of groups of experimental result sets according to different preset ageing temperatures;

performing three-dimensional fitting on the multiple groups of experimental result sets to obtain a target three-dimensional fitting equation set;

and obtaining a life evaluation model according to the three-dimensional fitting equation set.

5. A lifetime assessment device for a current transformer oiled paper, the device comprising:

The test data determining module is used for determining equivalent aging time, test temperature and test harmonic frequency of the current transformer oilpaper to be detected;

the target breakdown field strength determining module is used for inputting the equivalent aging time, the test temperature and the test harmonic frequency into a pre-trained life evaluation model to obtain the target breakdown field strength;

and the service life evaluation module is used for evaluating the service life of the current transformer oilpaper according to the target breakdown field intensity.

6. The apparatus of claim 5, wherein the target breakdown field strength determination module is specifically configured to:

determining initial field intensity and initial coefficient according to the equivalent aging time through the pre-trained life assessment model;

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

7. The apparatus of claim 5, wherein the target breakdown field strength determination module is specifically configured to:

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

When the equivalent aging time is smaller than the preset inflection point time, inputting the equivalent aging time, the test temperature and the test harmonic frequency into a pre-trained life evaluation model to obtain a second target breakdown field intensity;

and 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 a pre-trained life evaluation model to obtain a third target breakdown field intensity.

8. The apparatus according to claim 5, wherein the lifetime assessment model is obtained in particular by:

the high-temperature aging treatment module is used for carrying out high-temperature aging treatment on the training oilpaper insulating material according to a preset aging temperature;

the training sample acquisition module is used for manufacturing a plurality of identical training samples by using the processed training oilpaper insulating material;

the experiment result set determining module is used for carrying out harmonic breakdown experiments on each training sample according to different breakdown temperatures and breakdown harmonic frequencies, and obtaining a plurality of experiment results as an experiment result set;

the multi-group experimental result set determining module is used for obtaining a plurality of groups of experimental result sets according to different preset aging temperatures;

the three-dimensional fitting module is used for carrying out three-dimensional fitting on the plurality of groups of experimental result sets to obtain a target three-dimensional fitting equation set;

And the life evaluation model determining module is used for obtaining a life evaluation model according to the three-dimensional fitting equation set.

9. A computer device, comprising: a memory, a processor, and a computer program stored on the memory and executable on the processor, which when executed, implements the method for lifetime assessment of current transformer oilpaper according to any one of claims 1-4.

10. A computer readable storage medium, characterized in that the computer readable storage medium has stored therein instructions, which when run on a terminal device, cause the terminal device to perform the lifetime assessment method of a current transformer oilpaper according to any one of claims 1-4.

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