A method for evaluating the moisture and heat resistance performance of composite insulators

Abstract

This application belongs to the technical field of insulators, and particularly relates to a method for evaluating the moisture and heat resistance performance of composite insulators. The evaluation method provided in this application first fits according to the interface polarization time, direct current conductance, and low-frequency dispersion to obtain the interface polarization activation energy Ek, the conductance activation energy Ea, and the low-frequency dispersion activation energy Epeak. Then, it calculates based on the interface polarization activation energy Ek, the conductance activation energy Ea, and the low-frequency dispersion activation energy Epeak to obtain the evaluation parameter for the moisture and heat resistance performance of the composite insulator. The evaluation parameter for the moisture and heat resistance performance of the composite insulator reflects the dielectric loss caused by the change in charge distribution, the movement of charge carriers, and the free jump of charges in the composite insulator. The larger the evaluation parameter for the moisture and heat resistance performance of the composite insulator, the smaller the dielectric loss, and the stronger the moisture and heat resistance performance of the composite insulator, and it is more suitable to be used as a composite insulator in electrical equipment, solving the technical problem of the lack of a method for evaluating the moisture and heat resistance performance of composite insulators in the prior art.

Description

[0001] This application claims priority. The filing date of the prior application is: August 28, 2023, the application number is: 2023110880789, and the invention title is: A method for evaluating the moisture and heat resistance performance of composite insulators. Technical Field

[0002] This application belongs to the technical field of insulators, and particularly relates to a method for evaluating the moisture and heat resistance performance of composite insulators. Background Art

[0003] Insulators mainly include ceramic materials, glass materials, and composite materials. Among the composite material insulators, the main ones are composite insulators made of materials such as silicone rubber. Composite insulators are required as insulators in electrical equipment such as transmission lines, substations, urban rail transit vehicles, wind farms, and solar power plants. However, in recent years, with the extension of the operation time of composite insulators in electrical equipment, abnormal temperature rise phenomena have occurred in composite insulators. After statistics, it is found that the locations of the abnormal temperature rise phenomena are seasons with coexistence of high humidity and high temperature. Thus, it is determined that the moisture and heat factors should be an important cause for the abnormal temperature rise of composite insulators.

[0004] The basic structure of a composite insulator is the support member in the middle and the umbrella skirt sheath material made of silicone rubber on the outside. As an important component for protecting the core rod of the composite insulator, the moisture and heat aging resistance performance of the umbrella skirt sheath material is crucial. However, currently, for the moisture and heat environment, it is still unclear which factors of the composite insulator change to cause its abnormal temperature rise, so there is a lack of relevant evaluation methods. At the same time, since the moisture and heat resistance performance of the composite insulator is not known in advance, corresponding technical means are needed to accelerate the moisture and heat aging of the composite insulator. Due to the wide application of composite insulators in electrical equipment, it is necessary to propose an effective method for evaluating the moisture and heat resistance performance of silicone rubber materials for composite insulators, which helps to evaluate the quality of composite insulators in high humidity and high temperature environments, so as to select composite insulators with excellent moisture and heat resistance performance to be used as insulators in electrical equipment. Summary of the Invention

[0005] In view of this, this application provides a method for evaluating the moisture and heat resistance performance of composite insulators to solve the technical problem of the lack of a method for evaluating the moisture and heat resistance performance of composite insulators in the prior art.

[0006] The first aspect of this application provides a method for evaluating the moisture and heat resistance performance of composite insulators, including the steps:

[0007] Step S1: Conduct an accelerated moisture and heat aging test on the composite insulator to obtain the composite insulator after moisture and heat aging;

[0008] Step S2: Successively sample and test the composite insulator after moisture and heat aging with a broadband dielectric spectrometer to obtain the dielectric spectrum of the composite insulator after moisture and heat aging;

[0009] Step S3: Fit according to the dielectric spectrum of the composite insulator after hydrothermal aging to obtain the interfacial polarization time, direct current conductance, low-frequency dispersion, and correction parameters;

[0010] Step S4: Fit according to the interfacial polarization time, direct current conductance, and low-frequency dispersion to obtain the interfacial polarization activation energy E k , the conductance activation energy E a , and the low-frequency dispersion activation energy E peak ;

[0011] Step S5: Calculate according to the interfacial polarization activation energy E k , the conductance activation energy E a , and the low-frequency dispersion activation energy E peak to obtain the evaluation parameters of the hydrothermal resistance performance of the composite insulator.

[0012] Preferably, in Step S5: Calculate according to the interfacial polarization activation energy E k , the conductance activation energy E a , and the low-frequency dispersion activation energy E peak to obtain the evaluation parameters of the hydrothermal resistance performance of the composite insulator. The formula used in the calculation is:

[0013] T = 0.6E k + 0.1E peak + 0.3E a Equation 1.

[0014] Preferably, in Step S4: Fit according to the interfacial polarization time, direct current conductance, and low-frequency dispersion to obtain the interfacial polarization activation energy E k , obtain the conductance activation energy E a , and the low-frequency dispersion activation energy E peak . The formula used in the fitting is Equation 2-4:

[0015]

[0016] In Equation 2-4, τ is the parameter of the interfacial polarization time, σ dc is the parameter of the direct current conductance, ζ is the parameter of the low-frequency dispersion, E k is the parameter of the interfacial polarization activation energy, E a is the parameter of the conductance activation energy, E peak is the parameter of the low-frequency dispersion activation energy, σ c and τ peak are constants; A is the proportionality coefficient; E peak is the activation energy of relaxation 1; k b is the Boltzmann constant; ε0 is the vacuum permittivity; T is the thermodynamic temperature, σ c and τ peakis a constant. The parameters are obtained by fitting the temperature change curve through parameters. The parameters are all obtained by performing nonlinear curve fitting on the real and imaginary parts of the dielectric spectra at different temperatures.

[0017] Preferably, in step S3, fitting is performed according to the dielectric spectrum of the composite insulator after damp-heat aging to obtain the interfacial polarization time, direct current conductance, low-frequency dispersion, and correction parameters. The formula used for the fitting is Formula 5-7;

[0018]

[0019] In Formula 5, X s is the parameter of interfacial polarization in the correction parameters, n is the parameter of the interfacial polarization shape in the correction parameters, γ is the parameter of the low-frequency dispersion shape in the correction parameters, χ * (ω) is the electric susceptibility of silicone rubber, is the interfacial polarization component in the electric susceptibility, is the direct current conductance polarization component in the electric susceptibility; is the hopping conductance polarization component in the electric susceptibility, j is the unit of the mathematical complex number, the square root of -1. For experimental data, curve fitting is performed according to the formula to obtain the numerical values of the above parameters.

[0020] The parameter X of interfacial polarization in the correction parameters s , the parameter n of the interfacial polarization shape, and the parameter γ of the low-frequency dispersion shape are calculated by Formulas 6-7;

[0021]

[0022] In Formulas 6-7, R is the phase angle, is the real part of the electric susceptibility, and is the imaginary part of the electric susceptibility.

[0023] Preferably, in step S1, the process of the damp-heat aging acceleration test is: boiling in 0.1 wt% NaCl aqueous solution for 100 h.

[0024] Preferably, in step S2, the sample preparation is: successively drying, cutting, and surface metallizing the composite insulator after damp-heat aging.

[0025] Preferably, the diameter of the composite insulator after damp-heat aging after cutting is 30 mm, and the thickness is 1 mm.

[0026] Preferably, the temperatures measured by the broadband dielectric spectrometer are: measuring the composite insulator after damp-heat aging at 25 °C, 50 °C, 75 °C, and 100 °C respectively.

[0027] Preferably, the frequencies measured by the broadband dielectric spectrometer are: 10 -7 Hz to 10 -1Hz, and the test voltage is 3.0V rms.

[0028] In summary, the present application provides a method for evaluating the moisture and heat resistance performance of composite insulators. The evaluation method provided by the present application calculates the evaluation parameters for the moisture and heat resistance performance of composite insulators based on the interfacial polarization activation energy E k , the conductivity activation energy E a , and the low-frequency dispersion activation energy E peak . Then, the moisture and heat resistance performance of the composite insulator is directly evaluated according to the evaluation parameters for the moisture and heat resistance performance of the composite insulator. The larger the evaluation parameters for the moisture and heat resistance performance of the composite insulator, the stronger the moisture and heat resistance performance of the composite insulator, and the more suitable it is to be used as a composite insulator in electrical equipment. The activation energy reflects the threshold value of polarization of the composite insulator in the electrical equipment under the moisture and heat environment. The higher the activation energy, the more difficult it is for the composite insulator to polarize, the smaller the dielectric loss, and the less heat is generated by the composite insulator in the moisture and heat environment. The evaluation method provided by the present application comprehensively considers the interfacial polarization activation energy E k , the conductivity activation energy E a , and the low-frequency dispersion activation energy E peak in the calculation, which reflects the heat generated by the change of the charge distribution, the movement of charge carriers, and the consumption of electric energy by the free jump of charges in the composite insulator in the electrical equipment. The reliability of the evaluation method for the moisture and heat resistance performance is high, thus solving the technical problem of the lack of an evaluation method for the moisture and heat resistance performance of composite insulators in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 It is a schematic flow chart of the method for evaluating the moisture and heat resistance performance of the composite insulator provided by the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present application provides a method for evaluating the moisture and heat resistance performance of composite insulators to solve the technical problem of the lack of an evaluation method for the moisture and heat resistance performance of composite insulators in the prior art.

[0032] The following will clearly and completely describe the technical solutions of the present application with reference to the drawings. Obviously, the described embodiments are some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0033] Example 1

[0034] In view of the fact that it is currently impossible to pre-evaluate the abnormal temperature rise phenomenon of composite insulators in a humid and hot environment and there is a lack of a method for evaluating the humidity and heat resistance performance of composite insulators, Example 1 of this application provides a method for evaluating the humidity and heat resistance performance of composite insulators; the method for evaluating the humidity and heat resistance performance of composite insulators first fits according to the interface polarization time, direct current conductance, and low-frequency dispersion to obtain the interface polarization activation energy E k and obtains the conductance activation energy E a and the low-frequency dispersion activation energy E peak , and then calculates according to the interface polarization activation energy E k , the conductance activation energy E a and the low-frequency dispersion activation energy E peak to obtain the evaluation parameters for the humidity and heat resistance performance of composite insulators.

[0035] Among them, the composite insulator in a humid environment will absorb moisture under the action of an electro-thermal coupling field. The moisture is concentrated in the interface region and affects the direct current conductance and low-frequency dispersion phenomena of the material at the same time. The moisture will polarize and heat under an alternating electric field, and the dielectric loss of the material will also increase significantly after humidity and heat aging. Therefore, the humidity and heat resistance aging performance of silicone rubber materials can be evaluated by extracting characteristic parameters through the dielectric properties of composite insulators after humidity and heat aging; in a humid and hot environment, the dielectric loss of composite insulators in electrical equipment is mainly caused by the dielectric loss caused by the change in the charge distribution between different phases or interfaces in the composite insulator, the dielectric loss caused by the movement of charge carriers, and the dielectric loss caused by the free jump of charges in the restricted channels. Therefore, this application introduces the interface polarization activation energy E k to reflect the threshold that needs to be exceeded for the time when the charge distribution between different phases or interfaces in the composite insulator changes, and also introduces the direct current conductance activation E a in the composite insulator to reflect the energy barrier required for the movement of charge carriers in the composite insulator. The low-frequency dispersion activation energy E peak reflects the slow change in the charge distribution in the composite insulator and the threshold that needs to be exceeded for the free jump of charges in the restricted channels. However, according to the interface polarization activation energy E k , the direct current conductance activation energy E a and the low-frequency dispersion activation energy E peakThe evaluation parameters for the moisture and heat resistance performance of composite insulators are calculated. The moisture and heat resistance performance evaluation parameters provided in this application reflect the dielectric loss caused by the change in charge distribution between different phases or interfaces, the dielectric loss caused by the movement of charge carriers, and the dielectric loss caused by the free jump of charges in the restricted channels. Therefore, the moisture and heat resistance performance of composite insulators can be directly evaluated based on the moisture and heat resistance performance evaluation parameters of composite insulators. The larger the moisture and heat resistance performance evaluation parameters of composite insulators, the smaller the dielectric loss, and the stronger the moisture and heat resistance performance of composite insulators, and the more suitable it is to be used as a composite insulator in electrical equipment.

[0036] Preferably, the formula for the moisture and heat resistance performance evaluation parameter is: T = 0.6E k + 0.1E peak + 0.3E a Formula 1.

[0037] It should be noted that under the action of an external electric field, the change in charge distribution between different phases or interfaces in the composite insulator is the main cause of interfacial polarization and dielectric loss. Therefore, the activation energy required to reflect the change in charge distribution in the composite insulator under the action of an external electric field is used as the main factor in the moisture and heat resistance performance evaluation, and the activation energies required for the movement of charge carriers and the free jump of charges are comprehensively considered.

[0038] Preferably, the interfacial polarization activation energy E k , the obtained conductivity activation energy E a and the low-frequency dispersion activation energy E peak The fitting formula used is Formulas 2-4:

[0039]

[0040] In Formulas 2-4, τ is the parameter of the interfacial polarization time, σ dc is the parameter of the direct current conductivity, ζ is the parameter of the low-frequency dispersion, E k is the parameter of the interfacial polarization activation energy, E a is the parameter of the conductivity activation energy, E peak is the parameter of the low-frequency dispersion activation energy, σ c and τ peak are constants; A is the proportionality coefficient; E peak is the activation energy of relaxation 1; k b is the Boltzmann constant; ε0 is the vacuum permittivity; T is the thermodynamic temperature, σ c and τ peak are constants, and the parameters are solved by fitting the temperature change curve with parameters. The parameters are all obtained by non-linear curve fitting of the real and imaginary parts of the dielectric spectrum at different temperatures.

[0041] Example 2

[0042] Example 2 of this application is an example of the interfacial polarization time, DC conductivity, and low-frequency dispersion of the composite insulator described in Example 1. The example includes the steps of a composite insulator damp-heat accelerated aging test, a composite insulator sample preparation step, a composite insulator sample testing step, and a calculation step.

[0043] Among them, the steps of the composite damp-heat accelerated aging test include: cutting 5 specimens with a length of 50 mm, a width of 50 mm, and a thickness of 2 - 4 mm from a silicone rubber composite insulator, and then boiling the specimens in deionized water with 0.1 wt% NaCl for 100 h to conduct a damp-heat accelerated aging test;

[0044] The composite insulator sample preparation step includes: after drying the moisture on the surface of the specimen, cutting it into a cylindrical specimen with a diameter of 30 mm and a thickness of 1 mm, and then spraying gold on the upper and lower surfaces of the cylindrical specimen to obtain 5 composite insulator samples; among them, to improve the accuracy of the test, the 5 specimens should have no defects such as scratches, protrusions, pits, bubbles, marks, repairs, etc.

[0045] The composite insulator sample testing step includes: using a broadband dielectric spectrometer to test the dielectric spectra of the composite insulator samples at temperature gradients of 25 °C, 50 °C, 75 °C, and 100 °C at a voltage of 3.0 V rms and a frequency of 10 -7 Hz - 10 -1 Hz.

[0046] The calculation step includes: using Equation 5, that is, the modified Cole model, to perform fitting analysis on the dielectric spectra measured at temperatures of 25 °C, 50 °C, 75 °C, and 100 °C to extract the interfacial polarization parameter X s , the interfacial polarization time parameter τ, the interfacial polarization shape parameter n, the DC conductivity parameter σ dc , the low-frequency dispersion parameter ζ, and the low-frequency dispersion shape parameter γ;

[0047] Among them, the modified Cole model is

[0048]

[0049] In Equation 5, the interfacial polarization parameter X s can be numerically decomposed through Equations 6 - 7;

[0050]

[0051]

[0052] In Equations 5 - 7, X S is the parameter of interfacial polarization in the correction parameters, n is the parameter of the interfacial polarization shape in the correction parameters, γ is the parameter of the low-frequency dispersion shape in the correction parameters. In Equation 5, X sis the parameter for correcting the interfacial polarization in the parameters, n is the parameter for the shape of the interfacial polarization in the correction parameters, γ is the parameter for the shape of the low-frequency dispersion in the correction parameters, χ * (ω) is the electric susceptibility of silicone rubber, is the interfacial polarization component in the electric susceptibility, is the direct current conductance polarization component in the electric susceptibility; is the hopping conductance polarization component in the electric susceptibility, j is the unit of the mathematical symbol for the imaginary number, the square root of -1, R is the phase angle, is the real part of the electric susceptibility, is the imaginary part of the electric susceptibility. Curve fitting is performed on the experimental data according to the formula to obtain the numerical values of the above parameters.

[0053] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for evaluating the moisture and heat resistance performance of a composite insulator, characterized in that, Including the steps: Step S1: Conduct a damp-heat aging acceleration test on the composite insulator to obtain the composite insulator after damp-heat aging; Step S2: Successively sample and test the composite insulator after damp-heat aging with a broadband dielectric spectrometer to obtain the dielectric spectrum of the composite insulator after damp-heat aging; Step S3: Fit according to the dielectric spectrum of the composite insulator after damp-heat aging to obtain the interface polarization time, direct current conductance, low-frequency dispersion, and correction parameters; Step S4: Fit according to the interfacial polarization time, direct current conductance, and low-frequency dispersion to obtain the interfacial polarization activation energy E k , the conductance activation energy E a , and the low-frequency dispersion activation energy E peak ; Step S5. Calculate according to the interfacial polarization activation energy E k , the conductivity activation energy E a , and the low-frequency dispersion activation energy E peak to obtain the evaluation parameter of the wet heat resistance performance of the composite insulator. The formula used for the calculation is as follows: t = 0.6E k + 0.1E peak + 0.3E a Equation 1; Fitting is performed based on the interface polarization time, direct current conductance, and low-frequency dispersion to obtain the interface polarization activation energy E k and the conductance activation energy E a as well as the low-frequency dispersion activation energy E peak In this case, the formula used is Equation 2-4: In Equation 2-4, τ is the parameter of the interfacial polarization time, σ dc is the parameter of the direct current conductance, ζ is the parameter of the low-frequency dispersion, E k is the parameter of the interfacial polarization activation energy, E a is the parameter of the conductance activation energy, E peak is the parameter of the low-frequency dispersion activation energy, τ peak and σ c are constants; A is the proportionality coefficient; k b is the Boltzmann constant; ε0 is the vacuum permittivity; T is the thermodynamic temperature; When fitting according to the dielectric spectrum of the composite insulator after damp-heat aging to obtain the interface polarization time, direct current conductance, low-frequency dispersion, and correction parameters, the formula used is Equation 5; In Equation 5, X s is the parameter of interface polarization in the correction parameters, n is the parameter of the interface polarization shape in the correction parameters, γ is the parameter of the low-frequency dispersion shape in the correction parameters, χ * (ω) is the electric susceptibility of silicone rubber, is the interface polarization component in the electric susceptibility, is the direct current conductance polarization component in the electric susceptibility; is the hopping conductance polarization component in the electric susceptibility, ω is the angular frequency, and j is the unit of the imaginary number in mathematics; When fitting according to the dielectric spectrum of the composite insulator after damp-heat aging to obtain the interface polarization time, direct current conductance, low-frequency dispersion, and correction parameters, the formulas for obtaining the interface polarization parameter Xs, the interface polarization shape parameter n, and the low-frequency dispersion shape parameter γ in the correction parameters are Equations 6 - 7; In Equations 6 - 7, R is the phase angle, χ′(ω) is the real part of the electric susceptibility, χ″(ω) is the imaginary part of the electric susceptibility. Curve fitting of the experimental data according to the formula can obtain the numerical values of the above parameters.

2. The method for evaluating the moisture and heat resistance performance of a composite insulator according to claim 1, wherein In Step S1, the process of the damp-heat aging acceleration test is: boiling in a 0.1 wt% NaCl aqueous solution for 100 h.

3. The method for evaluating the moisture and heat resistance performance of a composite insulator according to claim 1, wherein In Step S2, the sampling is: successively drying, cutting, and surface metallizing the composite insulator after damp-heat aging.

4. A method for evaluating the moisture and heat resistance performance of a composite insulator according to claim 1, characterized in that, In Step S2, the temperatures measured in the broadband dielectric spectrometer test are: measuring the composite insulator after damp-heat aging at 25°C, 50°C, 75°C, and 100°C respectively.

5. The method for evaluating the moisture and heat resistance performance of a composite insulator according to claim 1, characterized in that, The measurement frequency of the broadband dielectric spectrometer test is: 10 -7 Hz to 10 -1 Hz, and the test voltage is 3.0V rms.

6. The method for evaluating the moisture and heat resistance performance of a composite insulator according to claim 3, wherein The diameter of the composite insulator after damp-heat aging after cutting is 20 - 40 mm, and the thickness is 0.5 - 2 mm.

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