A method and device for detecting air gap inside composite insulator

Abstract

The present invention discloses a method and device for detecting air gap inside a composite insulator, the method comprising: obtaining a set of terahertz reflection waves of the normal sample and the defective sample, and formulating a two-norm comparison table; obtaining the terahertz reflection wave at the interface of the composite insulator to be tested, and calculating the difference two-norm of the terahertz reflection wave at each defective sample interface and the terahertz reflection wave at the normal sample interface to obtain an actual difference two-norm; if the actual difference two-norm is less than a preset threshold, there is no internal air gap in the composite insulator to be tested; the actual difference two-norm is greater than or equal to the preset threshold, and the internal air gap size of the composite insulator to be tested is confirmed according to the two-norm comparison table and the actual difference two-norm. The present invention is adopted to realize non-destructive detection of air gap defects inside composite insulators based on terahertz, with simple operation and high detection accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of composite insulator detection, and in particular to a method and a device for detecting an internal air gap of a composite insulator. Background Art

[0002] Composite insulators have been used in power grids since the 1960s. With their excellent anti-pollution flashover performance, light weight, and easy installation, their application scale is increasing day by day. At present, there are about 7 million composite insulators used in power systems in my country, of which China Southern Power Grid has used more than 1.4 million composite insulators. In other words, the reliable operation of composite insulators is of great significance to the stable operation of power systems.

[0003] During actual operation, composite insulators frequently experience abnormal temperature rise, internal insulation breakdown, fracture and other fault defects. Studies have shown that the above-mentioned fault defects such as heating, breakdown and fracture are related to defects inside the composite insulator, and most of its internal defects are air gap defects. Therefore, it is of great significance to carry out internal air gap detection of composite insulators for the safe and reliable operation of composite insulators. As a hidden defect, the internal air gap defect is usually detected by infrared imaging in existing production and maintenance methods. However, it can only be detected when the air gap defect develops to a serious stage, partial discharge occurs inside, and material corrosion and aging produce obvious temperature rise. Other detection methods currently being explored in the laboratory include ultrasound and X-ray, but they all have limitations: the ultrasonic detection method is cumbersome to operate and has poor applicability to composite insulator detection; the X-ray detection method is harmful to the human body and is not very suitable for composite insulators made of composite materials. Summary of the invention

[0004] The embodiment of the present invention provides a method and device for detecting the internal air gap of a composite insulator, and discloses a method and device for quantitatively detecting the internal air gap based on the difference-two norm, which can conveniently and accurately detect the internal air gap of the composite insulator.

[0005] To achieve the above-mentioned purpose, a first aspect of an embodiment of the present application provides a method for detecting an air gap inside a composite insulator, comprising:

[0006] According to the surface material and internal structure of the composite insulator to be tested, a plurality of composite insulator samples with the same sheath thickness, sheath material and internal structure are manufactured;

[0007] A composite insulator sample is selected as a normal sample, and air gaps of different sizes are made inside other composite insulator samples as defective samples;

[0008] Obtaining a set of terahertz reflected waves of the normal sample and the defective sample, and formulating a two-norm comparison table;

[0009] Acquire the terahertz reflected wave at the interface of the composite insulator to be tested, calculate the difference bi-norm of the terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface, and obtain the actual difference bi-norm;

[0010] If the actual difference two-norm is less than the preset threshold, there is no internal air gap in the composite insulator to be tested; if the actual difference two-norm is greater than or equal to the preset threshold, the internal air gap size of the composite insulator to be tested is confirmed according to the two-norm comparison table and the actual difference two-norm.

[0011] In a possible implementation manner of the first aspect, acquiring the terahertz reflected wave sets of the normal sample and the defective sample and formulating a two-norm comparison table specifically includes:

[0012] The terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface are obtained, and a plurality of defect difference second norms are obtained for the terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface, respectively, to obtain a second norm comparison table.

[0013] In a possible implementation manner of the first aspect, confirming the internal air gap size of the composite insulator to be tested according to the two-norm comparison table and the actual difference two-norm specifically includes:

[0014] A defect difference second norm having the smallest absolute difference with the actual difference second norm is found in the second norm comparison table, and the internal air gap size of the defective sample corresponding to the defect difference second norm is used as the internal air gap size of the composite insulator to be tested.

[0015] In a possible implementation manner of the first aspect, the terahertz reflected wave is a time domain wave.

[0016] In a possible implementation manner of the first aspect, the air gap sizes in the defective samples are all smaller than 5 mm.

[0017] A second aspect of an embodiment of the present application provides a composite insulator internal air gap detection device, comprising:

[0018] The sample preparation module is used to prepare multiple composite insulator samples with the same sheath thickness, sheath material and internal structure according to the surface material and internal structure of the composite insulator to be tested; select one composite insulator sample as a normal sample, and prepare air gaps of different sizes inside other composite insulator samples as defective samples;

[0019] A comparison table formulation module, used to obtain the terahertz reflected wave sets of the normal sample and the defective sample, and formulate a two-norm comparison table;

[0020] The measuring module is used to obtain the terahertz reflected wave at the interface of the composite insulator to be measured, calculate the difference of the terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface, and obtain the actual difference of the terahertz reflected wave;

[0021] The judgment module is used to determine if the actual difference two-norm is less than a preset threshold value, and if the actual difference two-norm is greater than or equal to the preset threshold value, confirm the internal air gap size of the composite insulator to be tested according to the two-norm comparison table and the actual difference two-norm.

[0022] In a possible implementation manner of the second aspect, the comparison table formulation module is specifically used to:

[0023] The terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface are obtained, and a plurality of defect difference second norms are obtained for the terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface, respectively, to obtain a second norm comparison table.

[0024] In a possible implementation manner of the second aspect, confirming the internal air gap size of the composite insulator to be tested according to the two-norm comparison table and the actual difference two-norm specifically includes:

[0025] A defect difference second norm having the smallest absolute difference with the actual difference second norm is found in the second norm comparison table, and the internal air gap size of the defective sample corresponding to the defect difference second norm is used as the internal air gap size of the composite insulator to be tested.

[0026] In a possible implementation manner of the second aspect, the terahertz reflected wave is a time domain wave.

[0027] In a possible implementation manner of the second aspect, the air gap sizes in the defective samples are all smaller than 5 mm.

[0028] Compared with the prior art, the embodiment of the present invention provides a method and device for detecting air gaps inside a composite insulator. Since the second norm of the values ​​in the air gap defect and the nearby area will increase significantly, the embodiment of the present invention first preliminarily screens out the possibility of faults based on the measured difference second norm. If there is an air gap, the size is judged in combination with the second norm comparison table. Since the second norm comparison table contains the defect difference second norms of air gap defect samples and normal samples of various sizes, it is only necessary to select the air gap size corresponding to the defect difference second norm that is closest to the measured difference second norm as the air gap size detection result. In summary, the present invention can accurately and quickly find the hidden air gap inside the composite insulator. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic flow chart of a method for detecting an air gap inside a composite insulator provided by an embodiment of the present invention;

[0030] Figure 2 is a graph of the second norm value in a composite insulator detection area in one embodiment of the present invention;

[0031] Figure 3 It is a difference curve diagram between the defect difference second norm and the actual difference second norm in one embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1 An embodiment of the present invention provides a method for detecting an air gap inside a composite insulator, comprising:

[0034] S10. According to the surface material and internal structure of the composite insulator to be tested, a plurality of composite insulator samples with the same sheath thickness, sheath material and internal structure are manufactured.

[0035] S11. Select one composite insulator sample as a normal sample, and make air gaps of different sizes inside other composite insulator samples as defective samples.

[0036] S12. Obtain a set of terahertz reflected waves of the normal sample and the defective sample, and formulate a two-norm comparison table.

[0037] S13, obtaining the terahertz reflected wave at the interface of the composite insulator to be tested, calculating the difference bi-norm of the terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface, and obtaining an actual difference bi-norm.

[0038] S14. If the actual difference second norm is less than a preset threshold, there is no internal air gap in the composite insulator to be tested; if the actual difference second norm is greater than or equal to the preset threshold, the internal air gap size of the composite insulator to be tested is confirmed based on the second norm comparison table and the actual difference second norm.

[0039] Since air gap defects will change the conduction process of terahertz electromagnetic waves, the terahertz detection waveform of defective samples with defective parts is significantly different from that of normal samples—there are reflection peaks of defects, such as Figure 2The area marked in the box.

[0040] The embodiment of the present invention firstly produces defect samples with different air gap sizes through an artificial simulation method, collects terahertz reflected waves to form a waveform data set of different air gap defect sizes, and then when the waveform is actually measured, the difference bi-norm of the waveform at the corresponding interface is obtained to evaluate the degree of consistency with the defect waveform, thereby determining whether there is an interface defect and quantitatively analyzing the size of the defect.

[0041] Compared with the prior art, the embodiment of the present invention provides a method for detecting air gaps inside composite insulators. Since the two norms of the values ​​in the air gap defect and the nearby area will increase significantly, the embodiment of the present invention first preliminarily screens out the possibility of faults based on the measured difference two norms. If there is an air gap, the size is judged in combination with the two norm comparison table. Since the two norm comparison table contains the defect difference two norms of air gap defect samples and normal samples of various sizes, it is only necessary to select the air gap size corresponding to the defect difference two norm that is closest to the measured difference two norm as the air gap size detection result. In summary, the present invention can accurately and quickly find the hidden air gap inside the composite insulator.

[0042] Exemplarily, the step of obtaining the terahertz reflected wave sets of the normal sample and the defective sample and formulating a two-norm comparison table specifically includes:

[0043] The terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface are obtained, and a plurality of defect difference second norms are obtained for the terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface, respectively, to obtain a second norm comparison table.

[0044] In this embodiment, the size of each defect difference second norm in the second norm comparison table represents the degree of difference between the defect sample corresponding to the defect difference second norm and the normal sample.

[0045] Since defects will change the conduction process of terahertz electromagnetic waves, the terahertz detection waveform of defective parts will have obvious differences in waveform compared with non-defective parts, that is, normal parts. The judgment standard or process is to calculate the second norm. If the difference second norm exceeds a certain value, it is judged that there is a suspected defect; since the size of each defect difference second norm in the two-norm comparison table represents the degree of difference between the defect sample corresponding to the defect difference second norm and the normal sample, "finding the closest defect difference second norm in the two-norm comparison table" is equivalent to comparing the waveforms of artificially manufactured air gap defects of different scales to see which scale of air gap is most consistent, so as to finally determine the size of the air gap defect. Through this judgment process, what needs to be measured in the end is the size of the air gap corresponding to each defect sample. By comparing the degree of difference in the difference second norm of the waveform of the artificially manufactured air gap defect of different scales, a two-norm comparison table is made after obtaining multiple defect difference second norms.

[0046] Exemplarily, the determining the internal air gap size of the composite insulator to be tested according to the two-norm comparison table and the actual difference two-norm specifically includes:

[0047] A defect difference second norm having the smallest absolute difference with the actual difference second norm is found in the second norm comparison table, and the internal air gap size of the defective sample corresponding to the defect difference second norm is used as the internal air gap size of the composite insulator to be tested.

[0048] Take the sheath thickness and sheath material of 6mm silicone rubber patch as an example. Figure 3 The data in the figure show that the absolute value of the difference between the actual difference second norm and the sample with air gap defects is the smallest when the air gap is 0.155mm, indicating that the measured waveform is well consistent with the reflected waveform at the air gap size of 0.155mm. The deviation between the interface reflection wave of the normal sample and the waveform with an air gap of 0 in the data set is the smallest. Therefore, it is preliminarily judged that the air gap size of the sample with air gap defects is 0.155mm. Among them, it is difficult to analyze the accuracy of the test of the corrosion defect because it is difficult to directly measure the thickness. The air gap size is measured by a thickness gauge and the thickness is 0.148mm, which is less than the numerical deviation determined by the detection method of this embodiment. Therefore, this method can be effectively used for quantitative diagnosis of internal air gap defect sizes.

[0049] Exemplarily, the terahertz reflected wave is a time domain wave.

[0050] The curve set of the terahertz reflected wave at the composite insulator interface can be saved as a three-dimensional coordinate graph, where the x, y, and z axes are time, air gap, and amplitude, respectively.

[0051] Exemplarily, the air gap sizes in the defective samples are all less than 5 mm.

[0052] Because the internal air gap defect is large enough to a certain extent, such as 1mm, it can be identified by the eyes without detection. Therefore, in theory, it is only necessary to select multiple sets of data for encrypting the test of air gaps with defect sizes less than 1mm, which can be effectively used to determine the size of the air gap defect.

[0053] In general, the embodiments of the present invention propose a method for quantitatively detecting the internal air gap based on the difference-two norm, which solves the problem that the current quantitative detection method for the internal air gap of the composite insulator is relatively inadequate.

[0054] A second aspect of an embodiment of the present application provides a composite insulator internal air gap detection device, including a sample preparation module, a comparison table formulation module, a measurement module and a determination module.

[0055] The sample making module is used to make multiple composite insulator samples with the same sheath thickness, sheath material and internal structure according to the surface material and internal structure of the composite insulator to be tested; one composite insulator sample is selected as a normal sample, and air gaps of different sizes are made inside other composite insulator samples as defective samples.

[0056] The comparison table formulation module is used to obtain the terahertz reflected wave sets of the normal sample and the defective sample and formulate a two-norm comparison table.

[0057] The measuring module is used to obtain the terahertz reflected wave at the interface of the composite insulator to be measured, calculate the difference bi-norm of the terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface, and obtain the actual difference bi-norm.

[0058] The judgment module is used to determine if the actual difference two-norm is less than a preset threshold value, and if the actual difference two-norm is greater than or equal to the preset threshold value, confirm the internal air gap size of the composite insulator to be tested according to the two-norm comparison table and the actual difference two-norm.

[0059] In a possible implementation manner of the second aspect, the comparison table formulation module is specifically used to:

[0060] The terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface are obtained, and a plurality of defect difference second norms are obtained for the terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface, respectively, to obtain a second norm comparison table.

[0061] In a possible implementation manner of the second aspect, confirming the internal air gap size of the composite insulator to be tested according to the two-norm comparison table and the actual difference two-norm specifically includes:

[0062] A defect difference second norm having the smallest absolute difference with the actual difference second norm is found in the second norm comparison table, and the internal air gap size of the defective sample corresponding to the defect difference second norm is used as the internal air gap size of the composite insulator to be tested.

[0063] In a possible implementation manner of the second aspect, the terahertz reflected wave is a time domain wave.

[0064] In a possible implementation manner of the second aspect, the air gap sizes in the defective samples are all smaller than 5 mm.

[0065] Compared with the prior art, the embodiment of the present invention provides a composite insulator internal air gap detection device. Since the second norm of the value in the air gap defect and the nearby area will increase significantly, the embodiment of the present invention first preliminarily screens out the possibility of fault according to the measured difference second norm. If there is an air gap, it is combined with the second norm comparison table for size judgment. Since the second norm comparison table contains the defect difference second norms of air gap defect samples and normal samples of various sizes, it is only necessary to select the air gap size corresponding to the defect difference second norm that is closest to the measured difference second norm as the air gap size detection result. In summary, the present invention can accurately and quickly find the hidden air gap inside the composite insulator.

[0066] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be described again here.

[0067] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for detecting air gap inside a composite insulator, It is characterized in that include: According to the surface material and internal structure of the composite insulator to be tested, a plurality of composite insulator samples with the same sheath thickness, sheath material and internal structure are manufactured; A composite insulator sample is selected as a normal sample, and air gaps of different sizes are made inside other composite insulator samples as defective samples; Acquire a set of terahertz reflection waves of the normal sample and the defective sample, and formulate a two-norm comparison table; wherein, the acquisition of the set of terahertz reflection waves of the normal sample and the defective sample, and the formulation of the two-norm comparison table specifically includes: acquiring the terahertz reflection wave at each defective sample interface and the terahertz reflection wave at the normal sample interface, respectively obtaining a plurality of defect difference two-norms for the terahertz reflection wave at each defective sample interface and the terahertz reflection wave at the normal sample interface, and obtaining a two-norm comparison table; Acquire the terahertz reflected wave at the interface of the composite insulator to be tested, calculate the difference bi-norm of the terahertz reflected wave at each defective sample interface and the terahertz reflected wave at the normal sample interface, and obtain the actual difference bi-norm; If the actual difference two-norm is less than a preset threshold, the composite insulator to be tested does not have an internal air gap; if the actual difference two-norm is greater than or equal to the preset threshold, the internal air gap size of the composite insulator to be tested is confirmed according to the two-norm comparison table and the actual difference two-norm; wherein, confirming the internal air gap size of the composite insulator to be tested according to the two-norm comparison table and the actual difference two-norm specifically includes: finding a defect difference two-norm in the two-norm comparison table whose absolute value of difference with the actual difference two-norm is the smallest, and taking the internal air gap size of the defective sample corresponding to the defect difference two-norm as the internal air gap size of the composite insulator to be tested.

2. The method for detecting air gap inside a composite insulator according to claim 1, It is characterized in that The terahertz reflected wave is a time domain wave.

3. The method for detecting air gap inside a composite insulator according to claim 1, It is characterized in that The air gap sizes in the defective samples are all less than 5 mm.

4. A composite insulator internal air gap detection device, It is characterized in that include: The sample preparation module is used to prepare multiple composite insulator samples with the same sheath thickness, sheath material and internal structure according to the surface material and internal structure of the composite insulator to be tested; select one composite insulator sample as a normal sample, and prepare air gaps of different sizes inside other composite insulator samples as defective samples; A comparison table formulation module is used to obtain the terahertz reflection wave set of the normal sample and the defective sample, and formulate a two-norm comparison table; wherein the comparison table formulation module is specifically used to: obtain the terahertz reflection wave at each defective sample interface and the terahertz reflection wave at the normal sample interface, respectively obtain multiple defect difference two-norms for the terahertz reflection wave at each defective sample interface and the terahertz reflection wave at the normal sample interface, and obtain a two-norm comparison table; The actual measurement module is used to obtain the terahertz reflection wave at the interface of the composite insulator to be measured, and calculate the difference of the terahertz reflection wave at the interface of each defective sample and the terahertz reflection wave at the interface of the normal sample to obtain the actual difference of the norm; A judgment module, used for determining that if the actual difference two-norm is less than a preset threshold value, there is no internal air gap in the composite insulator to be tested; if the actual difference two-norm is greater than or equal to the preset threshold value, the internal air gap size of the composite insulator to be tested is confirmed according to the two-norm comparison table and the actual difference two-norm; wherein, confirming the internal air gap size of the composite insulator to be tested according to the two-norm comparison table and the actual difference two-norm specifically includes: finding a defect difference two-norm in the two-norm comparison table whose absolute value of difference with the actual difference two-norm is the smallest, and taking the internal air gap size of the defective sample corresponding to the defect difference two-norm as the internal air gap size of the composite insulator to be tested.

5. The composite insulator internal air gap detection device as claimed in claim 4, It is characterized in that The terahertz reflected wave is a time domain wave.

6. The composite insulator internal air gap detection device as claimed in claim 4, It is characterized in that The air gap sizes in the defective samples are all less than 5 mm.

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