Equivalent transformation method for resistivity of solid nonlinear insulating medium under different thicknesses

Abstract

The invention discloses an equivalent transformation method for resistivity of a solid nonlinear insulating medium under different thicknesses, and relates to the technical field of electrical insulation testing. In order to solve the technical problem of lack of a method for realizing equivalent conversion of the resistivity of a nonlinear insulating medium under different thickness conditions in the prior art, the method comprises the following steps: acquiring polarization current time-domain spectrums of samples with different thicknesses under various electric fields; fitting the spectrum, and extracting a steady-state current value; calculating a conducting current density based on the electrode area; establishing a function relation curve of the current density and the thickness; substituting the target thickness into the function, and extrapolating the corresponding current density; and calculating the insulation resistivity under the target thickness according to the electric field and the current density. The method can be used for evaluating the resistivity parameter of the nonlinear insulating material in power equipment.

Description

Technical Field

[0001] It relates to the field of electrical insulation testing technology, specifically to the equivalent transformation of the resistivity of solid nonlinear insulating media at different thicknesses. Background Art

[0002] With the development of high-voltage direct current power transmission, lightweight electrical equipment, and intelligent power grid systems, the performance requirements for insulating materials are increasing day by day. Although traditional linear insulating materials exhibit good insulating properties under general working conditions, when facing extreme working conditions such as high voltage, strong field gradient, and complex electric field distribution, their electric field regulation ability is weak, and problems such as local electric field concentration are likely to occur, which may further lead to insulation failure phenomena such as local breakdown and tree discharge.

[0003] Therefore, in recent years, more and more research has focused on nonlinear insulating dielectric materials. The remarkable feature of such materials is that their conductivity or resistivity shows a nonlinear response with the change of the applied electric field intensity. They maintain a high-resistance state under low electric fields and have enhanced conduction ability in high-electric-field regions, thus possessing the ability to self-equilibrate the electric field. Typical nonlinear materials such as silicon carbide-filled polymers and zinc oxide ceramics have been applied to power equipment such as cable accessories, field strength regulation layers, and nonlinear resistor chips.

[0004] In the performance characterization of nonlinear insulating materials, the characteristic curve of the direct current resistivity or conduction current density varying with the electric field is one of the key parameters, which is usually obtained through polarization current testing means. In existing research, experimental personnel generally prepare several thin insulating specimens, apply a series of direct current electric fields with different intensities, measure their current responses, and calculate the resistivity or conductivity of the materials accordingly. This method has the advantages of simple experimental equipment and strong controllability, and is suitable for carrying out comparative research and material screening under laboratory conditions.

[0005] However, since the thickness of the experimental samples is usually much smaller than the thickness of the insulating structures in actual engineering applications (for example, the experimental samples are 0.1 - 0.3 mm, while the main insulation or composite insulation layer of a cable may reach several millimeters to centimeters), the resistivity is significantly affected by the thickness. Existing experiments have proved that even under the same electric field conditions, nonlinear insulating material samples with different thicknesses may still show differences of several orders of magnitude in their conductive properties. This phenomenon is mainly due to the changes in the carrier migration paths, charge trapping and release mechanisms, and interface effects inside the material with the thickness.

[0006] For example, some studies have shown that due to problems such as uneven filler distribution and interface polarization delay in filled polymer nonlinear materials under large thickness conditions, their conductive behavior cannot be simply equated with that of thin specimens. Therefore, directly using the resistivity values measured in the laboratory for engineering structure design is likely to lead to design errors and safety hazards.

[0007] Furthermore, existing literature and engineering applications lack a method for unifying resistivity data for samples of varying thicknesses onto a comparable scale, nor do they offer effective mathematical models for modeling and extrapolating the current density variations across different thicknesses. This limitation directly limits the large-scale application of nonlinear insulating materials in engineering and increases the trial-and-error costs of experimental verification and structural design.

[0008] In summary, existing technologies have yet to provide a method that effectively converts laboratory-measured sheet resistivity to the resistivity of a target thickness structure without relying on extensive testing of sample thicknesses. Therefore, a universal, highly accurate, and easily implemented equivalent conversion method is urgently needed to address the parameter disconnect between experiments and engineering, and to provide accurate and reliable electrical parameter support for the application design of nonlinear insulating materials. Summary of the Invention

[0009] In order to solve the technical defect in the prior art that the prior art generally lacks a method for equivalent conversion of the resistivity of nonlinear insulating media under different thickness conditions, the technical solution provided by the present invention is as follows:

[0010] A method for equivalent transformation of the resistivity of a solid nonlinear insulating medium at different thicknesses, comprising:

[0011] The steps of obtaining nonlinear insulating medium samples of different thicknesses and measuring the polarization current time domain spectrum of each sample under multiple electric field strength conditions;

[0012] The step of fitting the polarization current time domain spectrum to extract the steady-state current value of each sample under the corresponding electric field strength;

[0013] The step of calculating the steady-state conduction current density of each sample under the corresponding electric field strength based on the electrode area and the steady-state current value;

[0014] The step of establishing a functional relationship curve between the conduction current density corresponding to each electric field intensity and the sample thickness based on the conduction current density data at multiple thicknesses;

[0015] Substituting the target thickness to be measured into the functional relationship curve to obtain the conduction current density at the target thickness;

[0016] The step of calculating the insulation resistivity of the nonlinear insulating medium at the target thickness based on the conduction current density at the target thickness and the known electric field strength.

[0017] Furthermore, a preferred embodiment is provided in which the polarization current time domain spectrum is fitted using a least squares method.

[0018] Further, a preferred embodiment is provided, wherein the steady-state conduction current density is calculated by dividing the steady-state current obtained by fitting by the effective area of the sample electrode.

[0019] Further, a preferred embodiment is provided, wherein the functional relationship curve is established by linear fitting in double logarithmic coordinates, and the fitting results include two parameters: slope and intercept.

[0020] Further, a preferred embodiment is provided, wherein the fitting model selected in the fitting work includes a superposition model of a steady-state current component and a component decaying with time.

[0021] Further, a preferred embodiment is provided, wherein the measured electric field strength ranges from 5 kV / mm to 30 kV / mm.

[0022] Based on the same inventive concept, the present invention further provides an equivalent transformation device for the resistivity of a solid nonlinear insulating medium at different thicknesses, comprising:

[0023] a module for obtaining nonlinear insulating medium samples with different thicknesses and measuring the polarization current time-domain spectra of each sample under multiple electric field strength conditions;

[0024] a module for fitting the polarization current time-domain spectra and extracting the steady-state current values of each sample at the corresponding electric field strength;

[0025] a module for calculating the steady-state conduction current density of each sample at the corresponding electric field strength based on the electrode area and the steady-state current value;

[0026] a module for establishing a functional relationship curve between the conduction current density corresponding to each electric field strength and the sample thickness according to the conduction current density data at multiple thicknesses;

[0027] a module for substituting the target thickness to be measured into the functional relationship curve to obtain the conduction current density at the target thickness;

[0028] a module for calculating the insulation resistivity of the nonlinear insulating medium at the target thickness based on the conduction current density at the target thickness and the known electric field strength.

[0029] Based on the same inventive concept, the present invention further provides a computer storage medium for storing a computer program, and when the computer program is read by a computer, the computer executes the method.

[0030] Based on the same inventive concept, the present invention further provides a computer, comprising a processor and a storage medium, and when the processor reads the computer program stored in the storage medium, the computer executes the method.

[0031] Based on the same inventive concept, the present invention also provides a computer program product. As a computer program, when the computer program is executed, the above-mentioned method is implemented.

[0032] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0033] Solve the interference problem of sample thickness on the resistivity test result: Most of the existing insulation resistivity test methods are based on thin sheet samples, ignoring the influence of thickness on the conductance path, charge polarization and conduction behavior, resulting in the measured results being unable to accurately reflect the electrical performance of large-thickness insulation structures in actual engineering. The present invention realizes the equivalent conversion between different thicknesses by establishing a mathematical model between the conduction current density and the thickness, eliminates the structural deviation of the sample thickness on the test result, and makes the experimental result more applicable to engineering and valuable for reference.

[0034] Reduce the experimental cost and improve the test efficiency: If the traditional method needs to obtain the resistivity parameters at different thicknesses, it usually needs to prepare multiple batches of thickness samples and test them one by one, which is a cumbersome process and has a high cost. The present invention can obtain the electrical parameters at any thickness by fitting and extrapolating the data of a limited number of thin sheet samples, greatly reducing the workload of experimental sample preparation and testing, improving the data acquisition efficiency, and being applicable to batch material screening and rapid parameter estimation in engineering application scenarios.

[0035] Improve the accuracy and robustness of current density extraction: The present invention uses the least square method to fit the polarization current time domain spectrum, which can effectively eliminate factors such as capacitor charging, polarization instability stage in the initial stage of the experiment and interference of the test system, and accurately extract the steady-state conduction current. Compared with the traditional method of taking the current value at a certain time point, this method has a more reasonable model and more stable parameters, which helps to obtain more reliable conduction characteristic data.

[0036] Establish a unified thickness-current density function model, which has universality and scalability: The modeling method of the double logarithmic function relationship between current density and thickness proposed by the present invention does not depend on the specific material type and is applicable to nonlinear insulating materials with various filler systems or matrix structures. By fitting the function model and updating the parameters, different material systems can be flexibly adapted, and it has good versatility and scalability, which is beneficial to constructing a material database and establishing a parameter prediction model.

[0037] Improve the scientificity and accuracy of material parameter selection in engineering design: The present invention connects the laboratory data with the engineering application scenario through the function model, so that the thin sheet resistivity parameters measured in the experiment can be accurately equivalent to the design thickness resistivity required for the actual structure, avoiding electrical safety problems caused by distorted parameter selection, and providing more scientific and real data support for the simulation analysis, process optimization and failure assessment of nonlinear insulation structures.

[0038] It has good application prospects and industrial promotion value: The present invention can be widely applied to multiple electrical and electronic fields such as high-voltage direct current transmission, cable accessories, composite insulation structures, and electric field regulation materials, and can provide key parameter support in material performance evaluation, insulation structure design, and electric field simulation analysis, having significant engineering application value and industrial promotion potential.

[0039] It can be applied to the resistivity parameter conversion and evaluation of nonlinear insulating materials in the insulation structure design of power equipment. Brief Description of the Drawings

[0040] Figure 1 It is a schematic diagram of the polarization current time-domain spectrum test system;

[0041] Figure 2 It is the polarization current time-domain spectrum;

[0042] Figure 3 It is the conduction current density j of specimens with different thicknesses under different electric field conditions DC And the relationship curve with the thickness d Detailed Embodiment

[0043] To make the advantages and beneficial effects of the technical solution provided by the present invention more clearly manifested, the technical solution provided by the present invention will be further described in detail with reference to the drawings. Specifically:

[0044] Embodiment 1. This embodiment provides an equivalent transformation method for the resistivity of a solid nonlinear insulating medium at different thicknesses, including:

[0045] The step of obtaining nonlinear insulating medium specimens with different thicknesses and measuring the polarization current time-domain spectra of each specimen under multiple electric field intensity conditions;

[0046] The step of fitting the polarization current time-domain spectrum and extracting the steady-state current values of each specimen under the corresponding electric field intensity;

[0047] The step of calculating the steady-state conduction current density of each specimen under the corresponding electric field intensity based on the electrode area and the steady-state current value;

[0048] The step of establishing a function relationship curve between the conduction current density corresponding to each electric field intensity and the specimen thickness according to the conduction current density data at multiple thicknesses;

[0049] The step of substituting the target thickness to be measured into the function relationship curve to obtain the conduction current density at the target thickness;

[0050] The step of calculating the insulation resistivity of the nonlinear insulating medium at the target thickness based on the conduction current density at the target thickness and the known electric field intensity.

[0051] Embodiment 2: This embodiment further limits an equivalent transformation method for the resistivity of a solid nonlinear insulating medium at different thicknesses provided in Embodiment 1. The fitting of the polarization current time-domain spectrum is performed by the least squares method.

[0052] Embodiment 3: This embodiment further limits an equivalent transformation method for the resistivity of a solid nonlinear insulating medium at different thicknesses provided in Embodiment 1. The steady-state conduction current density is calculated by dividing the steady-state current obtained by fitting by the effective area of the specimen electrode.

[0053] Embodiment 4: This embodiment further limits an equivalent transformation method for the resistivity of a solid nonlinear insulating medium at different thicknesses provided in Embodiment 1. The functional relationship curve is established by linear fitting in double logarithmic coordinates, and the fitting results include two parameters: slope and intercept.

[0054] Embodiment 5: This embodiment further limits an equivalent transformation method for the resistivity of a solid nonlinear insulating medium at different thicknesses provided in Embodiment 1. The fitting model selected in the fitting work includes a superposition model of a steady-state current component and a component that decays with time.

[0055] Embodiment 6: This embodiment further limits an equivalent transformation method for the resistivity of a solid nonlinear insulating medium at different thicknesses provided in Embodiment 1. The measurement electric field strength range is from 5 kV / mm to 30 kV / mm.

[0056] Embodiment 7: This embodiment provides an equivalent transformation device for the resistivity of a solid nonlinear insulating medium at different thicknesses, including:

[0057] a module for obtaining nonlinear insulating medium specimens with different thicknesses and measuring the polarization current time-domain spectra of each specimen under multiple electric field strength conditions;

[0058] a module for fitting the polarization current time-domain spectrum and extracting the steady-state current values of each specimen at the corresponding electric field strength;

[0059] a module for calculating the steady-state conduction current density of each specimen at the corresponding electric field strength based on the electrode area and the steady-state current value;

[0060] a module for establishing a functional relationship curve between the conduction current density corresponding to each electric field strength and the specimen thickness according to the conduction current density data at multiple thicknesses;

[0061] a module for substituting the target thickness to be measured into the functional relationship curve to obtain the conduction current density at the target thickness;

[0062] A module for calculating the insulation resistivity of the nonlinear insulating medium at the target thickness based on the conduction current density and the known electric field strength at the target thickness.

[0063] Embodiment 8: This embodiment provides a computer storage medium for storing a computer program. When the computer program is read by a computer, the computer executes the method provided in Embodiment 1.

[0064] Embodiment 9: This embodiment provides a computer, including a processor and a storage medium. When the processor reads the computer program stored in the storage medium, the computer executes the method provided in Embodiment 1.

[0065] Embodiment 10: This embodiment provides a computer program product. As a computer program, when the computer program is executed, it implements the method provided in Embodiment 1.

[0066] Embodiment 11: This embodiment further elaborates on the technical solution provided in Embodiment 1. Specifically:

[0067] A resistivity equivalent conversion method applicable to solid nonlinear insulating media can establish an equivalent conduction relationship between different thicknesses by measuring a limited number of thin-film specimens under laboratory conditions, and finally convert to obtain the insulation resistivity at any target thickness. This method has a clear technical process, which specifically includes the following steps:

[0068] The first step: Measure the polarization current time-domain spectrum of specimens with different thicknesses

[0069] The purpose of this step is to obtain the current response characteristic curves of the nonlinear insulating material at different thicknesses and electric field strengths. Specifically, select several nonlinear insulating medium specimens with different thicknesses, such as 100mm, 150mm, 200mm, 250mm, and 300mm, etc. The specimens can be prepared into circular or rectangular sheets by die pressing or cutting methods, ensuring that the upper and lower surfaces are smooth and flat, and pasting electrodes with equal areas. It is recommended to use metal foil electrodes or vacuum evaporation electrodes to ensure good contact between the electrodes and the specimens.

[0070] The electric field range applied to the specimens can be from 5 kV / mm to 30 kV / mm, and the voltage source should have good stability and low ripple characteristics. Under each electric field strength condition, record the time-varying curve of the polarization current through a highly sensitive current acquisition device. It is recommended that the sampling time range be from 10 seconds to 1000 seconds, and the sampling frequency is not less than 10 Hz to ensure capturing the complete polarization and steady-state conduction processes. The output of this step is: the current-time data curves of specimens with different thicknesses under different electric fields, that is, the polarization current time-domain spectrum.

[0071] The second step: Fit the polarization current time-domain spectrum and extract the steady-state current component

[0072] This step aims to accurately extract the current value of the material during the steady-state conduction stage from the experimental data. Import the polarization current time-domain spectrum into mathematical modeling software such as Origin, MATLAB, or Python, and use the least squares method to fit the data. The fitting model can choose the combination form of "steady-state component + exponential decay polarization component", or a double-exponential model can be selected according to the material characteristics.

[0073] The "steady-state current" parameter obtained by fitting is the long-term conduction current of the material under the conditions of this electric field and thickness, which can effectively eliminate the early-stage capacitor charging, electrode polarization, and transient interference components, and improve the test accuracy. The output of this step is: the steady-state current value under each thickness and electric field condition.

[0074] Step 3: Calculate the steady-state conduction current density

[0075] In this step, the steady-state conduction current density is obtained by dividing the steady-state current value obtained in the previous step by the electrode area, that is, the current intensity conducted per unit area. The electrode area should be accurately measured according to the electrode size. For example, if the electrode is a circular electrode with a diameter of 20 mm, the area is approximately 3.14 cm 2 (or 3.14×10 -4 m 2 ), and the units need to be unified during the calculation.

[0076] As an important parameter characterizing the conductivity of the material, the current density is the key variable for establishing the thickness relationship model in the follow-up. It is recommended to repeat the measurement more than 3 times and take the average for each group of data under the same electric field to improve the data stability. The output of this step is: the steady-state current density data corresponding to different thickness specimens under each electric field condition.

[0077] Step 4: Establish the functional relationship between the conduction current density and the thickness

[0078] In this step, regression analysis is performed on multiple groups of thickness and current density data pairs obtained in the third step. To more intuitively observe its variation law, a double logarithmic coordinate (log-log) plot is used to observe the distribution trend of the data points in the logarithmic coordinate, which usually shows a linear relationship.

[0079] Based on the linear relationship, linear fitting is performed to obtain fitting parameters, including the slope and intercept. The slope of the fitting curve represents the sensitivity of the current density to the thickness, while the intercept reflects the conductivity of the material at the reference thickness. Function models are established separately under different electric field intensities to form a set of mapping functions of electric field-thickness-current density, providing a mathematical expression for the next step. The output of this step is: the functional relationship expression between the current density and the thickness under each electric field condition.

[0080] Step 5: Extrapolate the current density at the target thickness and convert it to resistivity

[0081] According to the function model obtained in Step 4, substitute the required target thickness (such as the thickness actually used in engineering insulation design) to calculate the predicted current density value under this thickness condition. To ensure accuracy, the target thickness should be in the extrapolation extension range of the fitting range to avoid excessive extrapolation.

[0082] Furthermore, combined with the known applied electric field strength, divide the electric field value by the predicted current density to obtain the equivalent insulation resistivity under the target thickness condition. This conversion process has physical consistency, ensuring the rationality of the data and its practicality for engineering modeling. The final result can be used as an input parameter for engineering design to achieve an effective conversion from laboratory data to engineering applications.

[0083] In practical applications, the method of the present invention has been successfully applied to the resistivity conversion of SiC / LDPE nonlinear composites. Specimens of composites with a filler concentration of 5 phr were prepared and tested at multiple electric field strengths. A thickness-current density model was established through the above five-step method, and the resistivity values at engineering actual thicknesses such as 5 mm and 10 mm were successfully extrapolated, verifying the reliability and applicability of the model. The fitting correlation coefficient R 2 is higher than 0.94, indicating excellent model fitting.

[0084] Embodiment 12. Combination Figures 1 - 3 This embodiment will further describe the above-provided technical solution in detail through specific examples. Specifically:

[0085] In order to overcome the problem of non-equivalence between the insulation resistivity of a nonlinear insulating medium under laboratory conditions and the resistivity of the insulating medium in an insulation structure in the actual engineering field due to the thickness factor, the present invention provides a method for eliminating the influence of thickness on the measurement result of insulation resistivity and accurately obtaining the insulation resistivity of nonlinear insulating media with different thicknesses.

[0086] The present invention is achieved through the following technical solutions:

[0087] First, measure the polarization current time-domain spectrum of the test specimens with different thicknesses, and obtain the steady-state conduction current density j of the specimens with different thicknesses d under different electric fields E by performing least-squares fitting on the polarization current time-domain spectrum DC ; then, plot the relationship curve between the conduction current density j DC and the thickness d in a double-logarithmic coordinate system, fit the j DC -d curve to obtain the corresponding fitting parameters, and extrapolate the conduction current density j of the nonlinear insulating medium under the required thickness condition based on the function fitting relationship of the obtained j DC -d curve DC, finally, through the formula the insulation resistivity r is obtained by conversion.

[0088] Using Figure 1 the polarization current time-domain spectrum test system shown in the figure, measure the polarization current time-domain spectrum of the specimen under different thicknesses and different electric fields, and then use a suitable fitting formula to fit the measured polarization current time-domain spectrum, as shown in Figure 2 the figure. Among them, Figure 2 the current fitting formula used in

[0089] i(t) = A·t -n + i DC (1)

[0090] In the formula: i(t) is the measured current time-domain spectrum; A, n are fitting coefficients, t is time; i DC is the direct current conduction current.

[0091] After fitting, knowing that the effective area of the electrode is S, the direct current conduction current density j of the tested specimen under the corresponding conditions can be obtained DC . Plot the relationship curve between the conduction current density j DC of specimens with different thicknesses under different electric field conditions and the thickness d, as shown in Figure 3 the figure.

[0092] According to Figure 3 it can be found that in the double logarithmic coordinate system, there is an approximately linear relationship between the conduction current density and the thickness, that is:

[0093] lgj DC = n·lgd + k (2)

[0094] In the formula: n and k are constants respectively.

[0095] Converting Equation (2) into the form in the linear coordinate system, it is:

[0096]

[0097] Therefore, through Equation (3), the direct current conduction current density corresponding to the specimen at different thicknesses under the corresponding electric field conditions can be extrapolated, and further according to the insulation resistivity r of the specimen can be obtained by conversion.

[0098] Example:

[0099] The insulating medium in this embodiment is a silicon carbide / polyethylene (SiC / LDPE) nonlinear insulating medium with a filler concentration of 5 phr. The thicknesses of the prepared specimens are 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm respectively; the effective diameter of the electrodes used in the current time-domain spectrum measurement is 20 mm; the applied electric fields for measurement are 5 kV / mm, 10 kV / mm, 15 kV / mm, 20 kV / mm, 25 kV / mm, and 30 kV / mm respectively.

[0100] Figure 3 is the DC conduction current density j obtained after fitting DC The relationship curve with the thickness d. Equation (3) is used to Figure 3 Fit the experimental data in, and the fitting results are shown in the data in the fitting results of the j DC -d curve of SiC / LDPE nonlinear insulating media with different thicknesses.

[0101] Table 1

[0102] <![CDATA[Electric field strength / kV·mm -1 > n value K value <![CDATA[R 2 > 5 1.04 <![CDATA[8.53×10 -7 > 0.97 10 1.01 <![CDATA[7.95×10 -7 > 0.98 15 0.95 <![CDATA[6.20×10 -7 > 0.99 20 1.02 <![CDATA[1.04x10 -6 > 0.98 25 0.94 <![CDATA[1.26×10 -6 > 0.94 30 0.74 <![CDATA[7.97×10- 7 > 0.99

[0103] The insulation resistivity of the nonlinear insulating medium used in this example at different thicknesses can be extrapolated from the fitting parameters in Table 1.

[0104] The technical solutions provided by the present invention are further described in detail through several specific embodiments to highlight the advantages and beneficial effects of the technical solutions provided by the present invention. However, the above-mentioned several specific embodiments are not used as limitations on the present invention. Any reasonable modifications and improvements, combinations of embodiments, and equivalent substitutions based on the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An equivalent transformation method for the resistivity of a solid nonlinear insulating medium at different thicknesses, characterized in that, Including: Steps of obtaining nonlinear insulating dielectric specimens with different thicknesses and measuring the polarization current time-domain spectra of each specimen under multiple electric field strength conditions; Steps of fitting the polarization current time-domain spectra and extracting the steady-state current values of each specimen under the corresponding electric field strength; Steps of calculating the steady-state conduction current density of each specimen under the corresponding electric field strength based on the electrode area and the steady-state current value; Steps of establishing a function relationship curve between the conduction current density corresponding to each electric field strength and the specimen thickness according to the conduction current density data at multiple thicknesses; Steps of substituting the thickness of the target to be measured into the function relationship curve to obtain the conduction current density at the target thickness; Steps of calculating the insulation resistivity of the nonlinear insulating dielectric at the target thickness based on the conduction current density at the target thickness and the known electric field strength.

2. The equivalent transformation method of the resistivity of a solid nonlinear insulating medium under different thicknesses according to claim 1, characterized in that, The fitting of the polarization current time-domain spectra is performed by the least squares method.

3. An equivalent transformation method for the resistivity of a solid nonlinear insulating medium at different thicknesses according to claim 1, characterized in that The calculation of the steady-state conduction current density is obtained by dividing the steady-state current obtained by fitting by the effective area of the specimen electrode.

4. A method for equivalent transformation of the resistivity of a solid nonlinear insulating medium at different thicknesses according to claim 1, characterized in that The function relationship curve is established by linear fitting in double logarithmic coordinates, and the fitting results include two parameters: slope and intercept.

5. The equivalent transformation method of the resistivity of a solid nonlinear insulating medium under different thicknesses according to claim 1, characterized in that The fitting model selected in the fitting work includes a superposition model of a steady-state current component and a component decaying with time.

6. The equivalent transformation method of the resistivity of a solid nonlinear insulating medium under different thicknesses according to claim 1, characterized in that, The measured electric field strength range is from 5 kV / mm to 30 kV / mm.

7. An equivalent transformation device for the resistivity of a solid nonlinear insulating medium at different thicknesses, characterized in that Including: A module for obtaining nonlinear insulating dielectric specimens with different thicknesses and measuring the polarization current time-domain spectra of each specimen under multiple electric field strength conditions; A module for fitting the polarization current time-domain spectra and extracting the steady-state current values of each specimen under the corresponding electric field strength; A module for calculating the steady-state conduction current density of each specimen under the corresponding electric field strength based on the electrode area and the steady-state current value; A module for establishing a function relationship curve between the conduction current density corresponding to each electric field strength and the specimen thickness according to the conduction current density data at multiple thicknesses; A module for substituting the thickness of the target to be measured into the function relationship curve to obtain the conduction current density at the target thickness; A module for calculating the insulation resistivity of the nonlinear insulating dielectric at the target thickness based on the conduction current density at the target thickness and the known electric field strength.

8. A computer storage medium for storing a computer program, characterized in that, When the computer program is read by a computer, the computer executes the method described in claim 1.

9. A computer, comprising a processor and a storage medium, characterized in that, When the processor reads the computer program stored in the storage medium, the computer executes the method described in claim 1.

10. A computer program product, as a computer program, characterized in that When the computer program is executed, the method described in claim 1 is implemented.

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