Composite insulator abnormal heating area detection method based on Raman spectrum

Abstract

The invention relates to the technical field of composite insulator detection, and particularly discloses a Raman spectrum-based method for detecting an abnormal heating area of a composite insulator, which is suitable for a composite insulator with a silicone rubber sheath dyed by using ferric oxide as a pigment. The method comprises the following steps: firstly, selecting a to-be-detected sample, and performing spectrum acquisition on a to-be-detected area on the surface of the silicone rubber sheath by using a Raman spectrometer without applying operating voltage; then processing the spectral data, respectively extracting the characteristic peak intensities of ferric oxide in Raman shift ranges at 223 + / -8cm and 292 + / -12cm, and calculating the ratio of the two characteristic peak intensities; the obtained ratio is compared with a preset threshold value, whether an abnormal heating history exists in the to-be-detected area in the network hanging operation period or not is judged, and the preset threshold value is determined through establishment of a standard sample library and statistical analysis. The detection result is objective and is not interfered by electric field and environmental factors.

Description

Technical Field

[0001] This invention relates to the field of composite insulator testing technology, and more specifically, to a method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy. Background Technology

[0002] Composite insulators are high-voltage insulation devices made of a glass fiber reinforced epoxy resin core rod wrapped with a silicone rubber sheath and sheds. They are core insulation components for transmission and transformation lines and large-scale power equipment and facilities. During long-term operation in the power grid, composite insulators may exhibit localized temperatures significantly higher than normal locations during maintenance; this phenomenon is called abnormal heating. Abnormal heating in composite insulators significantly increases the probability of power failures and is a significant hidden danger affecting the safe operation of the power grid. Therefore, accurately detecting and locating the abnormal heating areas of composite insulators is crucial for ensuring the safe and stable operation of the power grid.

[0003] Currently, the industry commonly uses infrared thermography to monitor the temperature distribution of composite insulators in operation. However, this method has two inherent drawbacks in practical applications. First, it is limited by electric field factors: composite insulators only exhibit abnormal heating when connected to a high-voltage electric field. Composite insulators that are out of service or removed from operating lines cannot be detected for heating using infrared thermometers. Furthermore, changes in electric field strength alter the infrared thermography results, leading to instability. Second, it is limited by environmental factors: the temperature of abnormally heated areas in composite insulators is affected by ambient temperature, humidity, light, and airflow. Infrared thermography results vary under different meteorological conditions, and detection is impossible in environments with high humidity or strong sunlight. These drawbacks severely limit the applicability of existing infrared thermography technology in detecting abnormal heating in composite insulators, making it difficult to guarantee the objectivity and reliability of the detection results. There is an urgent need to develop a detection technology that is not limited by the operating status of composite insulators and on-site environmental conditions, and can accurately identify abnormally heated areas in composite insulators. Summary of the Invention

[0004] To overcome the aforementioned shortcomings of existing technologies, this invention provides a method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy. The method involves acquiring the Raman spectrum of the silicone rubber sheath of a composite insulator dyed with ferric oxide as a pigment, obtaining a value at 223±8 cm⁻¹. 292±12cm The intensity of two characteristic peaks is measured and the peak intensity ratio is calculated. Based on a preset threshold, it is determined whether there is a history of abnormal heating in the area under test. This invention overcomes the shortcomings of existing infrared thermometry technology, which requires detection under operating voltage and whose detection results are easily affected by ambient temperature, humidity, light, and airflow.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy includes the following steps:

[0007] Step S1: Select the composite insulator sample to be tested. The silicone rubber sheath of the composite insulator sample is dyed with ferric oxide as pigment during the production process.

[0008] Step S2: Use a Raman spectrometer to collect Raman spectra of the test area on the surface of the silicone rubber sheath of the composite insulator sample. No operating voltage is applied to the composite insulator sample during the acquisition process.

[0009] Step S3: Process the collected Raman spectral data and obtain the intensity of the first characteristic peak and the intensity of the second characteristic peak in the characteristic Raman spectrum of ferric oxide. The intensity of the first characteristic peak decreases with the increase of thermal aging, while the intensity of the second characteristic peak remains stable with the change of thermal aging.

[0010] Step S4: Calculate the ratio of the intensity of the first characteristic peak to the intensity of the second characteristic peak to obtain the peak intensity ratio;

[0011] Step S5: Compare the peak intensity ratio with a preset threshold to determine whether there is a history of abnormal heating in the area under test during the operation of the composite insulator sample on the grid.

[0012] As a further aspect of the present invention, in step S3, the intensity of the first characteristic peak is such that the Raman shift is 223±8 cm⁻¹. The intensity of the second characteristic peak is within the range of Raman shift at 292±12 cm⁻¹. The intensity of spectral peaks within the range.

[0013] During the thermal aging process, ferric oxide reaches 223±8cm. The intensity of the spectral peaks within the Raman shift range decreases slowly with increasing thermal aging, while the intensity at 292±12 cm⁻¹ decreases... The peak intensity within the Raman shift range remains stable with changes in the degree of thermal aging; therefore, the peak intensity ratio can be used as an analytical parameter to characterize the degree of thermal aging of ferric oxide. During operation in the grid, the silicone rubber sheath of the composite insulator in the abnormally heated area is subjected to thermal effects higher than the normal operating temperature for an extended period, resulting in a deeper degree of thermal aging of the ferric oxide pigment in the silicone rubber sheath in this area, and a smaller peak intensity ratio compared to the normal area.

[0014] As a further aspect of the present invention, in step S5, the determination rule for the preset threshold is as follows: when the peak intensity ratio is less than 0.56, it is determined that the area under test has abnormal heating during grid connection operation, and the temperature difference between the temperature of the area under test under operating voltage and the normal area temperature of the same composite insulator is greater than 1K; when the peak intensity ratio is greater than 0.65, it is determined that the area under test does not have abnormal heating during grid connection operation; when the peak intensity ratio is greater than or equal to 0.56 and less than or equal to 0.65, it is determined that the area under test has slight heating signs during grid connection operation, and the temperature difference between the temperature of the area under test under operating voltage and the normal area temperature of the same composite insulator is less than 1K.

[0015] As a further aspect of the present invention, in step S3, the intensity of the first characteristic peak and the intensity of the second characteristic peak are both the peak intensity of the spectral peak within the corresponding Raman shift range, or both are the integral area intensity of the spectral peak within the corresponding Raman shift range.

[0016] As a further aspect of the present invention, a step of establishing a standard sample library to determine a preset threshold is included before step S5, specifically:

[0017] Step A1: Select composite insulator samples with different service years as calibration samples. The silicone rubber sheath of the calibration samples is dyed with pigment containing ferric oxide.

[0018] Step A2: Apply an operating voltage to the calibration sample using infrared thermal imaging technology and measure the temperature to identify the known heating area and the normal area in the calibration sample.

[0019] Step A3: Raman spectroscopy is performed on the known heating area and the normal area using a dense array method. The position of each sampling point at 223±8 cm⁻¹ of ferric oxide is calculated. 292±12cm The characteristic peak intensity ratio at Raman shift was used to establish a mapping database between the peak intensity ratio and the heating state;

[0020] Step A4: Analyze the peak intensity ratio data in the mapping database using statistical analysis methods to determine the preset threshold.

[0021] As a further aspect of the present invention, in step S1, the composite insulator sample is a decommissioned operating sample, a currently operating sample, or a sample that has undergone accelerated aging test treatment.

[0022] As a further embodiment of the present invention, in step S2, the Raman spectrometer is a portable Raman spectrometer or a benchtop Raman spectrometer.

[0023] Compared with existing technologies, the advantages of this invention's method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy are as follows:

[0024] This invention detects ferric oxide in the silicone rubber sheath at 223±8 cm⁻¹ 292±12cm The ratio of the Raman characteristic peak intensities at two locations is used to characterize the degree of thermal aging in the tested area. Since thermal aging is a physicochemical change that occurs in a material under long-term thermal action, this change is solidified within the material, and the detection results directly reflect the aging state of the material itself. Compared with existing infrared thermometry, the detection results of this method do not depend on whether the composite insulator is connected to operating voltage, nor are they affected by the ambient temperature, humidity, light, and airflow conditions at the testing site. This fundamentally eliminates the instability of detection results caused by changes in electric field conditions and environmental factors in infrared thermometry.

[0025] This invention does not limit the use of the Raman spectrometer. It can be used with a portable Raman spectrometer for direct, in-situ sampling of the silicone rubber sheath surface at the composite insulator's operational site, or it can be sent to a laboratory for testing using a benchtop Raman spectrometer after the sample has been decommissioned or disassembled. Both methods yield valid results. Compared to existing infrared thermometry techniques, which can only be used for on-site testing of composite insulators under operating electric fields, this method is applicable to on-site testing of in-operation samples, laboratory analysis of decommissioned samples, and testing of samples after accelerated aging experiments, significantly expanding the scope of applicable testing scenarios. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of a method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy, according to the present invention.

[0027] Figure 2 These are laboratory pressure-resistant infrared thermal imaging images of some samples from Example 1 of this invention.

[0028] Figure 3 For some samples in Example 1 of this invention, the temperature was 223±8cm. The Raman spectral peak at that location.

[0029] Figure 4 For some samples in Example 1 of this invention, the temperature was 292±12 cm. The Raman spectral peak at that location.

[0030] Figure 5 This is an infrared thermography photo taken at the power grid operation site of the 500kV line composite insulator in Embodiment 2 of the present invention.

[0031] Figure 6 This is a laboratory infrared thermograph taken after the 500kV line composite insulator was disassembled in Embodiment 2 of the present invention. Detailed Implementation

[0032] The technical solutions of this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] This invention provides a method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy, applicable to composite insulator samples with silicone rubber sheaths dyed with ferric oxide as a pigment during the production process. The technical principle of this invention is based on the following principle: during the thermal aging process of ferric oxide, the Raman shift is approximately 223±8 cm. The spectral peak intensity within the range gradually decreases with increasing thermal aging, while the Raman shift is within 292±12 cm⁻¹. The peak intensity within the range remains stable with changes in the degree of thermal aging. During the operation of the composite insulator, the silicone rubber sheath in the abnormal heating area is subjected to heat above the normal operating temperature for a long time, resulting in a deeper degree of thermal aging of the ferric oxide pigment in this area, thus the peak intensity ratio is smaller than that in the normal area. This invention utilizes the above principle to accurately determine the history of abnormal heating of the composite insulator by detecting the changes in the Raman spectral characteristic peak intensity of ferric oxide in the silicone rubber sheath. This does not require applying an operating voltage to the composite insulator sample, and the detection results are unaffected by ambient temperature, humidity, light, and airflow conditions.

[0034] The detection method of the present invention is performed according to the following steps.

[0035] Step S1: Select the composite insulator sample to be tested and confirm that the silicone rubber sheath of the composite insulator sample was dyed with ferric oxide as pigment during the production process. The composite insulator sample can be a decommissioned operating sample, a sample currently in operation, or a sample that has undergone accelerated aging test treatment. All three types of samples are applicable to the testing method of this invention.

[0036] Step S2: Use a Raman spectrometer to collect Raman spectra of the test area on the surface of the silicone rubber sheath of the composite insulator sample. No operating voltage needs to be applied to the composite insulator sample during the acquisition process. The Raman spectrometer can be a portable Raman spectrometer or a benchtop Raman spectrometer. When using a portable Raman spectrometer, in-situ acquisition of data can be performed directly on the surface of the silicone rubber sheath at the site of the composite insulator's operation. When using a benchtop Raman spectrometer, the sample can be tested in a laboratory.

[0037] Step S3: Process the acquired Raman spectral data, and obtain the intensity of the first characteristic peak and the intensity of the second characteristic peak in the characteristic Raman spectrum of ferric oxide, wherein the intensity of the first characteristic peak is the Raman shift at 223±8 cm⁻¹. The spectral peak intensity is within the range, and the intensity of the second characteristic peak is Raman shifted at 292±12 cm⁻¹. The intensity of the spectral peak within the range. The intensity of both the first and second characteristic peaks can be taken as the peak intensity or the integral area intensity of the spectral peak. Both values ​​can be used for subsequent peak intensity ratio calculations.

[0038] Step S4: Calculate the ratio of the intensity of the first characteristic peak to the intensity of the second characteristic peak to obtain the peak intensity ratio. The formula for calculating the peak intensity ratio is:

[0039] ;

[0040] In the formula, R is the peak intensity ratio. The intensity of the first characteristic peak. The intensity of the second characteristic peak.

[0041] Step S5: Compare the peak intensity ratio with a preset threshold to determine whether the tested area has a history of abnormal heating during the operation of the composite insulator sample. Specifically, when the peak intensity ratio is less than 0.56, it is determined that the tested area has abnormal heating during operation, and the temperature difference between the tested area under operating voltage and the normal area temperature of the same composite insulator is greater than 1K; when the peak intensity ratio is greater than 0.65, it is determined that the tested area does not have abnormal heating during operation; when the peak intensity ratio is greater than or equal to 0.56 and less than or equal to 0.65, it is determined that the tested area has slight heating signs during operation, and the temperature difference between the tested area under operating voltage and the normal area temperature of the same composite insulator is less than 1K.

[0042] The preset threshold used in step S5 above is determined by establishing a standard sample library. The process of establishing the standard sample library is performed before step S5 and specifically includes the following steps:

[0043] Step A1: Select composite insulator samples with different service years as calibration samples. The silicone rubber sheath of the calibration samples is dyed with pigment containing ferric oxide.

[0044] Step A2: Apply an operating voltage to the calibration sample using infrared thermal imaging technology and measure the temperature to calibrate the known heating area and the normal area in the calibration sample.

[0045] Step A3: Raman spectroscopy is performed on the known heating area and the normal area using a dense dot matrix method, and the position of each sampling point at 223±8 cm⁻¹ of ferric oxide is calculated. 292±12cm The characteristic peak intensity ratio at Raman shift was used to establish a mapping database between the peak intensity ratio and the heating state;

[0046] Step A4: Analyze the peak intensity ratio data in the mapping database using statistical analysis methods to determine the preset threshold.

[0047] Example 1

[0048] This embodiment uses systematic testing of decommissioned samples to experimentally verify the detection method and preset threshold of the present invention. In step S1, a total of 75 composite insulator samples decommissioned after grid operation were collected. The voltage levels of the samples covered three categories: 110kV, 220kV, and 500kV, with an operating life of 5-25 years. The samples came from 12 manufacturers, and the silicone rubber sheaths of all samples were dyed with ferric oxide pigment, meeting the applicable conditions of the method of the present invention. In the stage of establishing a standard sample library, a power frequency withstand voltage test device was used to apply power frequency voltage to the 75 composite insulator samples. At the same time, an infrared thermal imager was used to record the temperature distribution of each sample under the power frequency electric field, thereby calibrating the known abnormal heating area and normal area of ​​each sample. The test results showed that 20 of the 75 samples showed abnormal heating at different locations and to different degrees. The infrared thermal images of some samples are shown below. Figure 2 As shown.

[0049] In step S2, a portable in-situ Raman spectrometer was used to collect Raman spectra of the silicone rubber sheaths of 75 samples, with the Raman shift range being 200-800 cm⁻¹. The sampling locations included three regions for each sample: near the high-pressure end, the middle region, and near the low-pressure end. These regions covered both the abnormally heating areas and the normal non-heating areas identified during the establishment of the standard sample library, with intensive sampling performed on the heating areas. A total of 310 Raman spectral data points were collected, including 155 data points from the non-heating areas and 155 data points from the abnormally heating areas.

[0050] In steps S3 and S4, the Raman displacement is 223±8cm Within the specified range, the highest peak intensity of each spectrum was defined as the first characteristic peak intensity, at a Raman shift of 292±12 cm⁻¹. The highest peak intensity of each spectrum within the specified range is used as the second characteristic peak intensity, and the peak intensity ratio is calculated. For some samples, the intensity is within 223±8 cm⁻¹. and 292±12cm Raman spectra at such locations Figure 3 and Figure 4As shown, the vertical axis represents the Raman signal intensity, and the horizontal axis represents the wavenumber.

[0051] In step S5, the peak intensity ratios of the 310 data points are correlated with the calibrated heating states during the establishment of the standard sample library. Statistical results show that the peak intensity ratios corresponding to abnormal heating areas with a temperature difference greater than 1K from the normal operating area are all less than 0.56; the peak intensity ratios corresponding to the normal area are all greater than 0.65; and the peak intensity ratios R corresponding to the edges of abnormal heating areas and slightly heated areas with a temperature difference less than 1K from the normal operating area are between 0.56 and 0.65. The above analysis results correspond completely to the infrared thermal imaging calibration results during the establishment of the standard sample library, verifying the accuracy of the preset threshold of the present invention.

[0052] Example 2

[0053] This embodiment uses the on-site inspection of in-service composite insulators in actual operating lines as a background to further verify the advantages of the method of the present invention compared with existing infrared thermometry technology. During the operation and maintenance of a 500kV transmission line, on-site infrared thermometry revealed overheating in the sheath area between the 6th and 14th sheds of a composite insulator from the high-voltage end. The on-site infrared thermometry photograph is shown below. Figure 5 As shown. After being removed from the power line, the sample was sent to the laboratory, where a 500kV power frequency voltage was applied and it was tested using an infrared thermal imager. The test results showed that the sample exhibited heating near the high-voltage end. However, the sheath area between the 6th and 14th umbrella skirts, which showed heating during on-site observation, did not exhibit heating during the laboratory withstand voltage test. The laboratory infrared thermogram is shown below. Figure 6 As shown.

[0054] A portable Raman spectrometer was used to collect Raman spectra of the sheath region between the 6th and 14th umbrella skirts. This process did not require applying an operating voltage to the sample. The intensity of the first characteristic peak was measured to be 0.42 au, and the intensity of the second characteristic peak was 0.98 au, with a calculated peak intensity ratio of 0.43. According to the preset threshold judgment rule of this invention, a peak intensity ratio of 0.43 is less than 0.56, indicating that the tested area has a history of abnormal heating during grid operation, and the operating temperature difference between the tested area and the normal area of ​​the same composite insulator is greater than 1 K. The Raman spectroscopy detection results of this embodiment are consistent with the on-site infrared thermography results, while overcoming the problem of misjudgment of infrared thermography results caused by differences in laboratory and on-site working conditions and environments.

[0055] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0056] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy, characterized in that, Includes the following steps: Step S1: Select the composite insulator sample to be tested. The silicone rubber sheath of the composite insulator sample is dyed with ferric oxide as pigment during the production process. Step S2: Use a Raman spectrometer to collect Raman spectra of the test area on the surface of the silicone rubber sheath of the composite insulator sample. No operating voltage is applied to the composite insulator sample during the acquisition process. Step S3: Process the collected Raman spectral data and obtain the intensity of the first characteristic peak and the intensity of the second characteristic peak in the characteristic Raman spectrum of ferric oxide, respectively. Step S4: Calculate the ratio of the intensity of the first characteristic peak to the intensity of the second characteristic peak to obtain the peak intensity ratio; Step S5: Compare the peak intensity ratio with a preset threshold to determine whether the area to be tested has a history of abnormal heating during the operation of the composite insulator sample on the grid.

2. The method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy according to claim 1, characterized in that, In step S3, the first characteristic peak intensity is the spectral peak intensity with a Raman shift in the range of 223±8 cm⁻¹; the second characteristic peak intensity is the spectral peak intensity with a Raman shift in the range of 292±12 cm⁻¹.

3. The method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy according to claim 1, characterized in that, In step S5, the determination rule for the preset threshold is as follows: when the peak intensity ratio is less than 0.56, it is determined that the area under test has abnormal heating during grid connection operation, and the temperature difference between the temperature of the area under test under operating voltage and the normal area temperature of the same composite insulator is greater than 1K; when the peak intensity ratio is greater than 0.65, it is determined that the area under test does not have abnormal heating during grid connection operation; when the peak intensity ratio is greater than or equal to 0.56 and less than or equal to 0.65, it is determined that the area under test has slight heating signs during grid connection operation, and the temperature difference between the temperature of the area under test under operating voltage and the normal area temperature of the same composite insulator is less than 1K.

4. The method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy according to claim 1, characterized in that, In step S3, the intensity of the first characteristic peak and the intensity of the second characteristic peak are both the peak intensity of the spectral peak within the corresponding Raman shift range, or both are the integral area intensity of the spectral peak within the corresponding Raman shift range.

5. The method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy according to claim 1, characterized in that, Before step S5, a step of establishing a standard sample library to determine the preset threshold is also included, specifically: Step A1: Select composite insulator samples with different service years as calibration samples. The silicone rubber sheath of the calibration samples is dyed with pigment containing ferric oxide. Step A2: Apply an operating voltage to the calibration sample using infrared thermal imaging technology and measure the temperature to calibrate the known heating area and the normal area in the calibration sample. Step A3: Raman spectroscopy is performed on the known heating area and the normal area using a dense dot matrix method. The ratio of the characteristic peak intensity at the Raman shifts of 223±8 cm⁻¹ and 292±12 cm⁻¹ for each sampling point is calculated, and a mapping database between the peak intensity ratio and the heating state is established. Step A4: Analyze the peak intensity ratio data in the mapping database using statistical analysis methods to determine the preset threshold.

6. The method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy according to claim 1, characterized in that, In step S1, the composite insulator sample is a decommissioned operating sample, a currently operating sample, or a sample that has undergone accelerated aging test treatment.

7. The method for detecting abnormal heating regions in composite insulators based on Raman spectroscopy according to claim 1, characterized in that, In step S2, the Raman spectrometer is a portable Raman spectrometer or a benchtop Raman spectrometer.

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