Reinforced thermal wave nondestructive testing method for mixed porcelain insulator
By applying photothermal excitation to the hybrid porcelain insulator and analyzing the temperature distribution using a thermal imager, the problem of difficult detection of internal defects in hybrid porcelain insulators was solved, achieving rapid and accurate non-destructive testing.
Patent Information
- Application Number
- CN202511161843.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-19
- Publication Date
- 2025-12-05
AI Technical Summary
Existing non-destructive testing methods are difficult to effectively detect defects and surface cracks at the porcelain-silicone rubber interface inside hybrid porcelain insulators, and infrared detection is not effective, is easily affected by the environment, and has a high rate of misdiagnosis.
An enhanced thermal wave non-destructive testing method is adopted. By applying photothermal excitation to the hybrid porcelain insulator, the surface temperature of the silicone rubber layer is increased. Thermal images are taken using a thermal imager, and the defect area is determined based on the temperature distribution. A thermal wave reflection model is constructed to calculate the temperature difference between the defective and normal areas.
It enables rapid and accurate detection of defects in hybrid porcelain insulators regardless of environmental changes, and the detection results are intuitive and visual, improving the accuracy and efficiency of detection, and is suitable for daily operation and maintenance.
Smart Images
Figure CN121068693A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of insulator nondestructive testing, in particular to a mixed porcelain insulator reinforced thermal wave nondestructive testing method. BACKGROUND
[0002] At present, the new disc type suspension mixed porcelain insulator is composed of a complete disc type suspension porcelain insulator and a high-temperature vulcanized silicone rubber layer coating, the HTV coating layer is formed on the surface of the core by using the injection high-temperature vulcanization one-step forming process, and the end part accessories are glued, so that the disc type suspension mixed porcelain insulator not only retains the excellent mechanical properties of the porcelain insulator and the excellent anti-pollution flashover capability of the composite insulator, but also has more and more extensive application in various extreme environments of power transmission lines.
[0003] The existing nondestructive testing methods for insulators mainly include infrared imaging method, ultrasonic testing method, ray testing method, microwave testing method and terahertz wave testing method. Among them, the infrared thermal imaging method belongs to a passive detection method, is greatly affected by environmental interference, and has a high false detection rate; the ultrasonic testing method needs to coat a coupling agent on the surface of the insulator; the ray testing method is sensitive to volume type defects, and is harmful to human body during testing; the microwave testing method and the terahertz testing method are new testing methods, and there is no field application example.
[0004] Among them, the mixed porcelain insulator needs to cooperate with the requirements of operation and maintenance work when it is operated in the power grid. However, the material structure of the mixed porcelain insulator is relatively complex, many detection methods continued from the porcelain and the composite insulator and the mature nondestructive testing methods in other industries are not applicable to the detection of the mixed porcelain insulator. The infrared temperature measurement nondestructive testing method commonly used for the composite insulator is not obvious when used on the mixed porcelain insulator, because the internal defect degree of the mixed porcelain insulator is small and the depth is large, and there is no obvious heating phenomenon on the surface. The infrared inspection effect is not obvious, and the infrared observation result is greatly affected by the environment and the monitoring condition, and fluctuates greatly, which easily causes misdiagnosis. Especially, the mixed porcelain insulator retains the advantages of the porcelain and the composite insulator, and also inevitably brings some new problems, such as the internal porcelain-silicone rubber interface defect, the cavity which is not easy to detect but may cause bonding failure, and the crack on the surface of the porcelain insulating part which is shielded by the silicone rubber layer and cannot be clearly seen by naked eyes. Therefore, a nondestructive testing method for the mixed insulator is urgently needed. SUMMARY
[0005] In view of the defects in the prior art, the purpose of the present application is to provide a mixed porcelain insulator reinforced thermal wave nondestructive testing method, which has the advantages of being able to calculate the surface temperature difference between the defect area and the normal area to judge the defect area of the mixed porcelain insulator, ignoring environmental changes, convenient detection, fast detection speed, intuitive and visual detection result, and high detection accuracy.
[0006] The above invention purpose of the present application is realized by the following technical scheme: a mixed porcelain insulator reinforced thermal wave nondestructive detection method, comprising the following steps:
[0007] Light-thermal excitation is applied to the mixed porcelain insulator, so that the surface temperature of the silicone rubber layer in the mixed porcelain insulator rises;
[0008] After the light-thermal excitation is applied to the mixed porcelain insulator for a preset time length, the thermal image of the mixed porcelain insulator taken by the thermal imager, according to the temperature distribution of the thermal image of the mixed porcelain insulator, it is judged whether the mixed porcelain insulator has defects, if the temperature distribution of the thermal image of the mixed porcelain insulator is uneven, the interface of the mixed porcelain insulator has defects; if the temperature distribution of the thermal image of the mixed porcelain insulator is uniform, the interface of the mixed porcelain insulator has no defects.
[0009] Preferably, the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the present application, the light-thermal excitation is applied to the mixed porcelain insulator, so that the surface temperature of the silicone rubber layer in the mixed porcelain insulator rises, comprising: applying light-thermal excitation to the mixed porcelain insulator, and heat wave penetrating through the surface of the silicone rubber layer of the mixed porcelain insulator, when reaching the silicone rubber-porcelain insulator interface, a part of the heat wave will be reflected at the silicone rubber layer-porcelain insulator interface, and the reflected heat wave will be reflected again at the silicone rubber surface-air interface, and the energy of the heat wave will be transmitted to the silicone rubber layer, causing the surface temperature of the silicone rubber layer to rise.
[0010] Preferably, the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the present application, the reflection coefficient of the interface air gap defect is greater than the reflection coefficient of the silicone rubber-porcelain insulator interface, so that the temperature rise of the defect area of the mixed porcelain insulator will be higher than that of the non-defect area, so as to judge whether the mixed porcelain insulator has defects according to the temperature distribution of the thermal image of the mixed porcelain insulator.
[0011] Preferably, the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the present application, the temperature rise of the silicone rubber layer of different diameter size defects is different, the larger the size of the defect, the more heat accumulated by the silicone rubber layer, and the more obvious the display in the thermal image of the mixed porcelain insulator.
[0012] Preferably, the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the present application, the preset time length ranges from 25 min to 35 min.
[0013] Preferably, the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the application comprises the following steps: after a preset time length of light-thermal excitation is applied to the mixed porcelain insulator, a thermal image of the mixed porcelain insulator is captured by a thermal imager, and whether the mixed porcelain insulator has defects is judged according to the temperature distribution of the thermal image of the mixed porcelain insulator; and a mixed porcelain insulator interface temperature upper division model is constructed according to a heat conduction differential equation of a light-thermal excitation source and a thermal wave reflection process, and the detection structure is verified.
[0014] Preferably, the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the application, according to the Fourier heat conduction law, the heat conduction differential equation of the light-thermal excitation source is as follows:
[0015]
[0016] In formula (1), alpha = lambda / (rho * c) represents the thermal diffusivity of the material; rho is the density; c is the specific heat capacity; z is the one-dimensional coordinate system direction; T is the temperature; and t is the time.
[0017] Preferably, the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the application adopts pulse excitation for heating, and formula (1) is obtained according to Laplace transform, and the surface temperature change formula of the silicon rubber layer is as follows:
[0018]
[0019] In formula (2), Q0 is the pulse excitation amplitude; t is the time; T0 is the initial temperature of the system; rho is the density; c is the specific heat capacity; z is the one-dimensional coordinate system direction; and alpha represents the thermal diffusivity of the material.
[0020] Preferably, the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the application, the thermal wave circulates in the silicon rubber layer, so that the temperature function of the silicon rubber layer in the actual light-thermal excitation source irradiation is considered to be the superposition of different reflected thermal waves, and the surface temperature change formula of the silicon rubber layer considering reflection is derived from the silicon rubber layer temperature under the pulse excitation of formula (2):
[0021]
[0022] In formula (3), r s is the reflection coefficient of the silicon rubber-porcelain insulating part interface of the mixed porcelain insulator; r g is the reflection coefficient of the surface silicon rubber-air interface; h is the thickness of the silicon rubber layer of the mixed porcelain insulator; n is a natural number from 1 to infinity; Q0 is the pulse excitation amplitude; t is the time; T0 is the initial temperature of the system; rho is the density; c is the specific heat capacity; and alpha represents the thermal diffusivity of the material.
[0023] Preferably, the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the application has the advantages that the high-order thermal wave component has a smaller contribution to the surface temperature of the mixed porcelain, the reflection coefficient of the gas-solid interface is 1, the temperature formula of the defect-free area of the mixed porcelain insulator is:
[0024]
[0025] In formula (4), r s is the reflection coefficient of the silicone rubber-porcelain insulating part interface of the mixed porcelain insulator; T0 is the initial temperature of the system; p is the density; c is the specific heat capacity; a represents the thermal diffusivity of the material; Q0 is the pulse excitation amplitude; t is the time; and h is the thickness of the silicone rubber layer of the mixed porcelain insulator.
[0026] Similarly, the temperature formula of the defect area of the mixed porcelain insulator is:
[0027]
[0028] In formula (5), T0 is the initial temperature of the system; p is the density; c is the specific heat capacity; a represents the thermal diffusivity of the material; Q0 is the pulse excitation amplitude; t is the time; and h is the thickness of the silicone rubber layer of the mixed porcelain insulator.
[0029] In summary, the application provides a mixed porcelain insulator reinforced thermal wave nondestructive detection method, which comprises the following steps: applying a photo-thermal excitation to the mixed porcelain insulator to cause the surface temperature of the silicone rubber layer in the mixed porcelain insulator to rise; after applying the photo-thermal excitation for a preset time length, capturing a thermal image of the mixed porcelain insulator by a thermal imager, and judging whether the mixed porcelain insulator has defects according to the temperature distribution of the thermal image of the mixed porcelain insulator; if the temperature distribution of the thermal image of the mixed porcelain insulator is uneven, the interface of the mixed porcelain insulator has defects; and if the temperature distribution of the thermal image of the mixed porcelain insulator is uniform, the interface of the mixed porcelain insulator has no defects; the method has the advantages of additional photo-thermal excitation to the mixed porcelain insulator, detection of infrared radiation parameters of different areas, calculation of the surface temperature difference between the defect area and the normal area, judgment of the defect area of the mixed porcelain insulator, environmental change invisibility, convenient detection, fast detection speed, intuitive and visual detection results, and high detection accuracy. BRIEF DESCRIPTION OF DRAWINGS
[0030] Figure 1 is a flowchart of the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the embodiment of the application.
[0031] Figure 2 is a mixed porcelain insulator reinforced thermal wave nondestructive detection schematic diagram in the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the embodiment of the application.
[0032] Figure 3 is the thermal image of the interface defect-free mixed porcelain insulator in the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the embodiment of the application Figure 1 .
[0033] Figure 4 is the thermal image of the interface defect-free mixed porcelain insulator in the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the embodiment of the application Figure 2 .
[0034] Figure 5 is the thermal image of the interface defect-free mixed porcelain insulator in the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the embodiment of the application Figure 1 .
[0035] Figure 6 is the thermal image of the interface defect-free mixed porcelain insulator in the mixed porcelain insulator reinforced thermal wave nondestructive detection method provided by the embodiment of the application Figure 2 . DETAILED DESCRIPTION
[0036] The application will be further described in detail below with reference to the accompanying drawings. Referring to Figure 1 and Figure 2 , the application discloses a mixed porcelain insulator reinforced thermal wave nondestructive detection method, which comprises the following steps:
[0037] S101, applying photo-thermal excitation to the mixed porcelain insulator to make the surface temperature of the silicon rubber layer in the mixed porcelain insulator rise;
[0038] S102, after the photo-thermal excitation with a preset time length is applied to the mixed porcelain insulator, judging whether the mixed porcelain insulator has defects according to the temperature distribution of the thermal image of the mixed porcelain insulator taken by a thermal imager, if the temperature distribution of the thermal image of the mixed porcelain insulator is uneven, the interface of the mixed porcelain insulator has defects, and if the temperature distribution of the thermal image of the mixed porcelain insulator is uniform, the interface of the mixed porcelain insulator has no defects; in this way, by additionally applying photo-thermal excitation to the mixed porcelain insulator, the infrared radiation parameters of different regions are detected, the surface temperature difference between the defect region and the normal region is calculated to judge the defect region of the mixed porcelain insulator, and the mixed porcelain insulator has the advantages of being not affected by environmental changes, convenient to detect, fast in detection speed, intuitive and visual in detection result, high in detection accuracy, not needing power transmission lines to be powered off for cooperation, and being convenient for finding mixed porcelain insulator defects in daily operation and maintenance.
[0039] Further, in the embodiment, S101, the light-thermal excitation is applied to the mixed porcelain insulator, so that the surface temperature of the silicone rubber layer in the mixed porcelain insulator rises, which comprises: applying light-thermal excitation to the mixed porcelain insulator, and the thermal wave penetrates through the surface of the silicone rubber layer of the mixed porcelain insulator, when reaching the silicone rubber-porcelain insulator interface, a part of the thermal wave will be reflected at the silicone rubber layer-porcelain insulator interface, and the reflected thermal wave will be reflected again at the silicone rubber layer-air interface, according to this rule, the energy of the thermal wave will be transmitted to the silicone rubber layer, causing the surface temperature of the silicone rubber layer to rise; by additionally applying light-thermal excitation to the mixed porcelain insulator, the complex conditions such as the requirement that there should be no precipitation weather one day before the operation, the weather should be good and dry on the operation day, and the operation should be carried out in overcast days or before sunrise, after sunset and at night, etc. can be ignored, and the detection can be carried out regardless of environmental changes, except for the influence of the surface heating of the mixed porcelain insulator caused by environmental factors such as humidity and contamination, the accuracy of defect detection is improved; in addition, compared with the conventional 50mm focal length unmanned aerial vehicle infrared equipment, the test distance should not exceed 20m, the mixed porcelain insulator reinforced thermal wave nondestructive detection method can efficiently realize the detection of the mixed porcelain insulator interface air gap defect within a range of 100 meters, and the detection distance is greatly improved.
[0040] The parameters of the light-thermal excitation source are shown in Table 1.
[0041] Table 1: Parameters of the light-thermal excitation source
[0042] Infrared wavelength 850 nm ± 2 nm Light source 8 x 10 W laser + 16 x 10 W dot array chip Power ＜240W Irradiation distance 2-50 meters Light exit angle 15～90° Duration 60 min
[0043] In the embodiment, the reflection coefficient of the interface air gap defect is greater than the reflection coefficient of the silicone rubber-porcelain insulator interface, so that the temperature rise of the defect area of the mixed porcelain insulator will be higher than that of the non-defect area, and the temperature distribution of the mixed porcelain insulator thermal image is used to determine whether the mixed porcelain insulator has defects.
[0044] Specifically, the light-thermal excitation is additionally applied to the mixed porcelain insulator by the external light-thermal excitation source, and the difference in reflection coefficients between the defect area and the non-defect area affects the internal heat transfer, so that there is a difference in the surface temperature of the silicone rubber layer in different areas, and then it is determined whether the mixed porcelain insulator has defects.
[0045] In which, the temperature rise of the silicone rubber layer of different diameter size defects is different, the larger the size of the defect, the more heat accumulated in the silicone rubber layer, and the more obvious the display in the mixed porcelain insulator thermal image.
[0046] Specifically, the preset time range is 25-35 minutes. In the embodiment, the preset time is 30 minutes.
[0047] Specifically, the mixed porcelain insulator with no defects and the mixed porcelain insulator with defects are respectively subjected to the strengthening thermal wave nondestructive detection, and the thermal imagers are used to shoot the mixed porcelain insulator thermal image of the mixed porcelain insulator with no defects and the mixed porcelain insulator thermal image of the mixed porcelain insulator with defects after the light-thermal excitation source lasts for 30 minutes, the surface temperature of the mixed porcelain insulator with no defects is uniform, as shown in Figure 3 and Figure 4 , and the surface temperature distribution of the mixed porcelain insulator with defects is uneven, as shown in Figure 4 and Figure 5 .
[0048] Specifically, the temperature of the edge silicon rubber layer close to the iron cap and the steel foot area is obviously greater than the temperature of the umbrella skirt silicon rubber layer, the temperature difference is 10 degrees, and it can be considered that the mixed porcelain insulator has a more serious defect.
[0049] Further, after the light-thermal excitation source is applied to the mixed porcelain insulator for a preset length of time, the mixed porcelain insulator thermal image is shot by the thermal imager, and whether the mixed porcelain insulator has defects is determined according to the temperature distribution of the mixed porcelain insulator thermal image, and then the method further comprises: a mixed porcelain insulator interface temperature distribution model is constructed according to the heat conduction differential equation of the light-thermal excitation source and the thermal wave reflection process, and the detection structure is verified.
[0050] According to the Fourier heat conduction law, the heat conduction differential equation of the light-thermal excitation source is as follows:
[0051]
[0052] In formula (1), α = λ / (ρc) represents the thermal diffusivity of the material; ρ is the density; c is the specific heat capacity; z is the one-dimensional coordinate system direction; T is the temperature; and t is the time.
[0053] The formula (1) is obtained according to the Laplace transform, and the surface temperature change formula of the silicon rubber layer is:
[0054]
[0055] In formula (2), Q0 is the pulse excitation amplitude; t is the time; T0 is the initial temperature of the system; ρ is the density; c is the specific heat capacity; z is the one-dimensional coordinate system direction; and α represents the thermal diffusivity of the material.
[0056] As shown in Figure 1 , the thermal wave circulates in the silicon rubber layer, so that the silicon rubber layer temperature function in the actual light-thermal excitation source irradiation is considered to be the superposition of different reflected thermal waves, and the silicon rubber surface layer temperature change formula considering reflection is derived from the silicon rubber layer temperature under the pulse excitation of formula (2):
[0057]
[0058] in formula (3), r s is the reflection coefficient of the interface between the silicone rubber and the porcelain insulator; r g is the reflection coefficient of the interface between the silicone rubber and the air; h is the thickness of the silicone rubber layer of the composite porcelain insulator; n is a natural number from 1 to infinity; Q0 is the amplitude of the pulse excitation; t is the time; T0 is the initial temperature of the system; p is the density; c is the specific heat capacity; and a represents the thermal diffusivity of the material.
[0059] In view of the fact that the higher-order thermal wave components have a small contribution to the temperature of the composite porcelain, the 3rd and higher-order components are ignored in the calculation, and the reflection coefficient of the gas-solid interface is 1, the temperature formula of the defect-free region of the composite porcelain insulator is:
[0060]
[0061] in formula (4), r s is the reflection coefficient of the interface between the silicone rubber and the porcelain insulator; T0 is the initial temperature of the system; p is the density; c is the specific heat capacity; a represents the thermal diffusivity of the material; Q0 is the amplitude of the pulse excitation; t is the time; and h is the thickness of the silicone rubber layer of the composite porcelain insulator.
[0062] Similarly, the temperature formula of the defect region of the composite porcelain insulator is:
[0063]
[0064] in formula (5), T0 is the initial temperature of the system; p is the density; c is the specific heat capacity; a represents the thermal diffusivity of the material; Q0 is the amplitude of the pulse excitation; t is the time; and h is the thickness of the silicone rubber layer of the composite porcelain insulator.
[0065] The surface temperature difference formula between the defect region and the normal region of the composite porcelain insulator can be obtained from formula (4) and formula (5):
[0066]
[0067] in formula (6), r s is the reflection coefficient of the interface between the silicone rubber and the porcelain insulator; p is the density; c is the specific heat capacity; a represents the thermal diffusivity of the material; Q0 is the amplitude of the pulse excitation; t is the time; and h is the thickness of the silicone rubber layer of the composite porcelain insulator.
[0068] In actual detection, the photo-thermal excitation source is not a pulse excitation, but has a relatively long duration, usually 20-30 min, and therefore the thermal excitation function is represented as:
[0069]
[0070] The surface temperature of the mixed porcelain insulator is the convolution of the pulse heat response and the heat excitation function, and the surface temperature formula of the interface defect region of the mixed porcelain insulator under the continuous light heat excitation is:
[0071]
[0072] When the surface temperature difference of the mixed porcelain insulator in the thermal imager is greater than 5K, it is considered that the mixed porcelain insulator has interface defects.
[0073] The application provides a mixed porcelain insulator reinforced thermal wave nondestructive detection method, including the following steps: applying light heat excitation to the mixed porcelain insulator to make the surface temperature of the silicon rubber layer in the mixed porcelain insulator rise; after the mixed porcelain insulator is applied with light heat excitation for a preset time length, the thermal image of the mixed porcelain insulator is shot by a thermal imager, whether the mixed porcelain insulator has defects is judged according to the temperature distribution of the thermal image of the mixed porcelain insulator, if the temperature distribution of the thermal image of the mixed porcelain insulator is uneven, the interface of the mixed porcelain insulator has defects; if the temperature distribution of the thermal image of the mixed porcelain insulator is uniform, the interface of the mixed porcelain insulator has no defects; in this way, the light heat excitation is additionally applied to the mixed porcelain insulator, the infrared radiation parameters of different regions are detected, the surface temperature difference between the defect region and the normal region is calculated to judge the defect region of the mixed porcelain insulator, and the method has the advantages of being not affected by environmental changes, convenient to detect, fast in detection speed, intuitive and visual in detection result, and high in detection accuracy.
[0074] It should be noted that the relational terms herein such as first and second and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises... a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.
[0075] Finally, it should be noted that: obviously, the above embodiments are only examples for clearly illustrating the present application, and are not limitations on the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.
Claims
1. A method for reinforcing the thermal wave non-destructive testing of composite porcelain insulators, characterized in that: The method comprises the following steps: applying light-thermal excitation to the mixed porcelain insulator, so that the surface temperature of the silicone rubber layer in the mixed porcelain insulator rises; After the mixed porcelain insulator is subjected to the light-thermal excitation for the preset time length, the thermal image of the mixed porcelain insulator is captured by a thermal imager, and whether the mixed porcelain insulator has defects is determined according to the temperature distribution of the thermal image of the mixed porcelain insulator; if the temperature distribution of the thermal image of the mixed porcelain insulator is uneven, the interface of the mixed porcelain insulator has defects; if the temperature distribution of the thermal image of the mixed porcelain insulator is uniform, the interface of the mixed porcelain insulator has no defects.
2. The method of claim 1, wherein the mixed porcelain insulator is a composite insulator. The method for applying light-thermal excitation to the mixed porcelain insulator, so that the surface temperature of the silicone rubber layer in the mixed porcelain insulator rises, comprises the following steps: The mixed porcelain insulator is subjected to light-thermal excitation, and thermal waves penetrate through the surface of the silicone rubber layer of the mixed porcelain insulator; when reaching the silicone rubber-porcelain insulator interface, a part of the thermal waves is reflected at the silicone rubber layer-porcelain insulator interface, and the reflected thermal waves are reflected again at the silicone rubber layer surface-air interface; the energy of the thermal waves is transmitted to the silicone rubber layer, causing the surface temperature of the silicone rubber layer to rise.
3. The method of claim 2, wherein the mixed porcelain insulator is a composite insulator. The reflection coefficient of the interface air gap defect is greater than the reflection coefficient of the silicone rubber-porcelain insulator interface, so that the temperature of the defect area of the mixed porcelain insulator rises higher than that of the non-defect area, and whether the mixed porcelain insulator has defects is determined according to the temperature distribution of the thermal image of the mixed porcelain insulator.
4. The method of claim 3, wherein the method further comprises: The temperature rise degree of the silicone rubber layer of different diameter size defects is different; the larger the size of the defect is, the more heat the silicone rubber layer accumulates, and the more obvious the defect is displayed in the thermal image of the mixed porcelain insulator.
5. The method of claim 1, wherein the mixed porcelain insulator is a hybrid porcelain insulator. The preset time length ranges from 25 min to 35 min.
6. The method of claim 1, wherein the mixed porcelain insulator is a post insulator. After the mixed porcelain insulator is subjected to the light-thermal excitation for the preset time length, the thermal image of the mixed porcelain insulator is captured by a thermal imager, and whether the mixed porcelain insulator has defects is determined according to the temperature distribution of the thermal image of the mixed porcelain insulator; if the temperature distribution of the thermal image of the mixed porcelain insulator is uneven, the interface of the mixed porcelain insulator has defects; if the temperature distribution of the thermal image of the mixed porcelain insulator is uniform, the interface of the mixed porcelain insulator has no defects. According to the heat conduction differential equation of the light-thermal excitation source and the thermal wave reflection process, a mixed porcelain insulator interface temperature distribution model is constructed, and the detection structure is verified.
7. The method of thermographic non-destructive testing of a composite porcelain insulator according to claim 6, characterized in that: According to the Fourier heat conduction law, the heat conduction differential equation of the light-thermal excitation source is as follows: In formula (1), α = λ / (ρc) represents the thermal diffusivity of the material; ρ is the density; c is the specific heat capacity; z is the one-dimensional coordinate system direction; T is the temperature; and t is the time.
8. The method of thermographic non-destructive testing of a composite porcelain insulator according to claim 7, characterized in that: The formula (1) is obtained according to the Laplace transform under the pulse excitation heating, and the surface temperature change formula of the silicone rubber layer is as follows: In formula (2), Q0 is the pulse excitation amplitude; t is the time; T0 is the initial temperature of the system; ρ is the density; c is the specific heat capacity; z is the one-dimensional coordinate system direction; and α represents the thermal diffusivity of the material.
9. The method of thermographic non-destructive testing of a composite porcelain insulator according to claim 8, characterized in that: The thermal waves circulate in the silicone rubber layer, so that the temperature function of the silicone rubber layer in the actual light-thermal excitation source irradiation is considered to be the superposition of different reflected thermal waves, and the surface temperature change formula of the silicone rubber layer under the consideration of reflection is derived from the silicone rubber layer temperature under the pulse excitation of formula (2). In formula (3), r s is the reflection coefficient of the interface between the silicone rubber and the porcelain insulator of the composite porcelain insulator; r g is the reflection coefficient of the interface between the surface silicone rubber and air; h is the thickness of the silicone rubber layer of the composite porcelain insulator; n is a natural number from 1 to infinity; Q0 is the amplitude of the pulse excitation; t is time; T0 is the initial temperature of the system; p is the density; c is the specific heat capacity; and a represents the thermal diffusivity of the material.
10. The method of thermographic non-destructive testing of a composite porcelain insulator according to claim 9, characterized in that: The high order thermal wave component contributes less to the surface temperature of the mixed porcelain, and the reflection coefficient of the gas-solid interface is 1, so the temperature formula of the mixed porcelain insulator without defects is: In formula (4), r s is the reflection coefficient of the interface between the silicone rubber and the porcelain insulator of the mixed porcelain insulator; T0 is the initial temperature of the system; p is the density; c is the specific heat capacity; a represents the thermal diffusivity of the material; Q0 is the amplitude of the pulse excitation; and t is the time. h is the thickness of the silicone rubber layer of the mixed porcelain insulator; Similarly, the temperature formula of the mixed porcelain insulator with defects is: In formula (5), T0 is the initial temperature of the system; ρ is the density; c is the specific heat capacity; α represents the thermal diffusivity of the material; Q0 is the amplitude of the pulse excitation; t is the time; and h is the thickness of the silicone rubber layer of the mixed porcelain insulator.