On-site detection method for ablation defect of buffer layer of high-voltage cable

Abstract

The invention relates to the technical field of high-voltage cable state detection, and discloses a high-voltage cable buffer layer ablation defect on-site detection method, which comprises the following steps: S1, arranging a plurality of gas taking points on a cable to be detected, and drilling gas taking holes at the gas taking points to enable a gas storage space to be communicated with the outside; s2, the gas sampling end of a gas detection device is in butt joint with any gas taking hole through an airtight connecting piece, gas in the gas storage space is extracted and subjected to infrared spectroscopic analysis, and an analysis result of the concentration of ethane, ethylene, acetylene and carbon monoxide is obtained; s3, comparing the analysis results of the plurality of gas taking points with a preset criterion, and judging the ablation grade of the to-be-detected cable; and S4, the air taking holes are sealed and repaired. According to the on-site detection method, the whole process of gas taking, detection, recovery and rating can be completed under the electrified condition, and multi-component characteristic gas can be accurately measured, so that rapid, accurate and quantitative diagnosis of the ablation defect of the buffer layer of the high-voltage cable is realized.

Description

Technical Field

[0001] This invention relates to the field of high-voltage cable condition testing technology, and in particular to a method for on-site detection of ablation defects in the buffer layer of high-voltage cables. Background Technology

[0002] High-voltage XLPE cables, as core equipment in urban power transmission networks, directly impact the safety and stability of the power grid through their operational reliability. In recent years, the electro-thermal coupling between the corrugated aluminum sheath and the buffer layer has frequently induced localized overheating, leading to the thermal decomposition of the polyester fibers (PET) in the water-blocking buffer layer. This decomposition generates various characteristic gases such as H2, C2H6, C2H4, C2H2, and CO. Statistics show that from 2001 to 2022, over 30 breakdown accidents occurred in 110kV and above cables in China due to this issue. All failures occurred within 10 years of commissioning, far below the 30-year design life.

[0003] To promptly detect and address buffer layer ablation defects, various detection methods have been proposed in the industry, including partial discharge method, broadband impedance spectroscopy, X-ray imaging, infrared thermography, and characteristic gas detection method. However, all of the above methods treat "gas detection" as an offline testing step, resulting in a long testing cycle. Furthermore, these methods have varying degrees of limitations, making accurate defect detection difficult. Specifically: partial discharge methods exhibit weak, intermittent, and phaseless discharge signals in the early stages of ablation, leading to severe electromagnetic noise interference and a high rate of missed detections; broadband impedance spectroscopy only reflects the overall impedance change of the cable, requiring laboratory calibration and making it difficult to distinguish between early ablation and minor moisture defects; X-ray imaging can only identify defects in the later stages of ablation when "white spots" or structural deformation appear, resulting in a short detection length and high radiation protection costs and complex operation; infrared thermal imaging shows a small temperature rise in the early stages of ablation and is easily affected by environmental temperature, humidity, emissivity, and shooting angle, making quantitative judgment of defect levels impossible; among characteristic gas detection methods, gas chromatography-mass spectrometry (GC-MS) offers high accuracy, but the sampling-transportation-laboratory analysis cycle is long, requiring carrier gas and a vacuum system, resulting in poor field adaptability; semiconductor or electrochemical sensors are susceptible to cross-interference, exhibiting large baseline drift, and have detection limits >50 for key components such as C2H2 and CO. ppm is insufficient to meet the needs of early defect detection. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a field detection method for ablation defects in the buffer layer of high-voltage cables. This method can complete the entire process of "gas sampling—detection—recovery—rating" under energized conditions and can accurately measure multi-component characteristic gases, thereby enabling rapid, accurate, and quantitative diagnosis of ablation defects in the buffer layer of high-voltage cables.

[0005] The specific technical solution of this invention is as follows: a method for on-site detection of ablation defects in the buffer layer of a high-voltage cable, wherein the high-voltage cable includes a buffer layer and a corrugated aluminum sheath arranged from the inside out, and a gas storage space for storing decomposition gas of the buffer layer is formed between the buffer layer and the corrugated aluminum sheath. The on-site detection method includes the following steps: S1: Set up a gas sampling point on the cable to be tested, and drill a gas sampling hole at the gas sampling point; S2: Connect the gas sampling end of the gas detection device to the gas intake port through the airtight connector, extract the gas in the gas storage space and perform infrared spectroscopy analysis to obtain the analysis results of the concentration of ethane, ethylene, acetylene and carbon monoxide. S3: Compare the analysis results of the gas sampling point with the preset criteria to determine the ablation level of the cable under test; S4: Perform sealing and repair treatment on the air intake hole; The gas detection device is equipped with an infrared spectroscopy unit.

[0006] Traditional detection methods, such as partial discharge testing and X-ray imaging, either require contact with the internal structure of the cable or disassembly of the joint after power outage, which seriously affects the reliability of power grid supply and easily damages the cable insulation integrity. This invention, however, employs an innovative design of "external opening - airtight gas sampling - rapid repair," operating entirely outside the cable without altering its energized operating state. The entire detection process does not damage the cable's main insulation structure, eliminating the risk of electric shock. The entire process of "gas sampling - detection - recovery - rating" can be completed under energized conditions. Furthermore, this invention utilizes infrared spectroscopy detection technology, unaffected by the on-site electromagnetic environment, enabling accurate and rapid measurement of multi-component characteristic gases to meet the detection needs of defects at each stage. In addition, by comparing the analysis results from several gas sampling points with preset criteria, this invention can achieve rapid, accurate, and quantitative diagnosis of ablation defects in the buffer layer of high-voltage cables.

[0007] Optionally, the preset criterion is: a) If ethane, ethylene, and acetylene are all <10 ppm, it is determined that there is no ablation; b) If ethane and ethylene concentrations are 10–100 ppm, the condition is considered a suspected ablation. c) If ethane and ethylene concentrations are >100 ppm, it is considered that ablation has occurred and the product should be included in the maintenance plan; d) If ethane and ethylene concentrations are greater than 500 ppm and carbon monoxide concentrations are greater than 10,000 ppm, the cable is considered severely ablated and replacement is recommended.

[0008] The aforementioned technical solution establishes a threshold system that correlates the concentration of multiple characteristic gases with the ablation level: ethane and ethylene, as the main products of buffer layer thermal decomposition, directly reflect ablation progress through concentration changes. Low-concentration acetylene confirms pure ablation defects without severe discharge, while high-concentration CO indicates that ablation has triggered severe thermal decomposition. Ethane and ethylene serve as the core indicators for ablation judgment, with acetylene assisting in eliminating interference, and carbon monoxide as an intensifying indicator of severe ablation, forming a scientifically rigorous quantitative basis for judgment. This system completely overcomes the limitations of traditional detection methods that rely on the experience of maintenance personnel, providing clear and unified operational standards for on-site work. It effectively avoids early defect omissions or over-repair due to judgment errors, ensuring timely intervention at critical stages of ablation defect development, minimizing the risk of cable breakdown, and preventing the loss of the optimal maintenance window.

[0009] Optionally, the cable under test is provided with at least 3 gas sampling points. According to the preset criteria, if 3 or more consecutive gas sampling points on the cable under test reach b), c), or d), line-level processing should be initiated according to the corresponding risk level; otherwise, local targeted processing should be carried out according to the single-point risk level.

[0010] The above technical solution achieves a three-dimensional balance of "safety assurance, operation and maintenance efficiency, and cost control" by defining the boundaries between line-level and single-point defects. It not only accurately prevents and controls the safety risks of systemic defects, but also optimizes the allocation of operation and maintenance resources for local defects, providing key technical support for the long-term management of high-voltage cable buffer layer ablation defects.

[0011] Optionally, the cable under test is provided with several gas sampling points. The gas sampling points are set up as follows: the first gas sampling point starts from a distance of ≥10 m from the cable joint under test, and one point is arranged every 80~120 m along the cable route.

[0012] In the above technical solution, the gas sampling point is set at a distance of ≥10m from the cable joint to be tested. This avoids structural interference and electric field distortion areas near the joint. Subsequent gas sampling points are flexibly arranged at intervals of 80~120m along the cable route. This avoids missing early defects due to excessive spacing and also prevents unnecessary maintenance costs and workload due to excessively close spacing, thus achieving a balance between detection accuracy and maintenance costs.

[0013] Optionally, in step S1, an air intake hole is drilled using an electric drill, and the electric drill is equipped with a limiting ring to restrict the drilling depth in order to avoid damaging the buffer layer.

[0014] In the above technical solution, a hand drill with a limit ring is used to drill the air intake hole in one step. The limit ring strictly controls the drilling depth within a safe range that does not touch the inner buffer layer and the main insulation layer, eliminating the risk of damage to the buffer layer and the main insulation layer caused by excessive drilling. At the same time, the limit ring can realize the standardization and safety of drilling operation.

[0015] Optionally, the gas detection device may also include a hydrogen sensor.

[0016] In the above technical solution, since the more severe the cable erosion, the higher the H2 concentration, a hydrogen sensor is set up to capture the H2 concentration signal, supplement the detection blind zone of the infrared spectrum, form a multi-dimensional gas monitoring system, and avoid defect misjudgment caused by the omission of a single component.

[0017] Optionally, the gas detection device may also include a pressure sensor.

[0018] In the above technical solution, a pressure sensor is set up to verify the airtightness of the gas sampling channel and ensure the effectiveness of the sampling.

[0019] Optionally, in step S2, the airtight connector includes a silicone nozzle that is sealed to the air intake hole, and a flexible tube with one end connected to the silicone nozzle and the other end connected to the gas sampling end of the gas detection device.

[0020] In the above technical solution, the silicone nozzle has excellent elastic deformation capability, which can tightly fit the hole wall and the surrounding aluminum sheath surface through its own deformation to form a reliable sealing interface; the flexible hose connects the silicone nozzle and the gas detection device, which is highly flexible and avoids the limitation of operating space caused by rigid connection.

[0021] Optionally, in step S4, the sealing and repair process is as follows: insert a repair aluminum nail into the air intake hole, fill it with a waterproof metal repair agent, and then cover it with water-blocking insulating tape and PVC tape in sequence to seal the air intake hole.

[0022] In the above technical solution, the core area of ​​the repaired aluminum nail filling hole is reinforced, possessing excellent rigidity and structural stability. Once installed, it strengthens the aluminum sheath structure at the air intake. A waterproof metal repair agent fills the tiny gaps between the aluminum nail and the air intake wall, forming a dense, rigid sealing layer after curing. The lower layer of water-blocking insulating tape provides both water resistance and insulation, while the upper layer of PVC tape provides protection and reinforcement. This multi-layered sealing structure, working together, meets the short-term sealing restoration needs of the cable after testing while ensuring the safety and reliability of long-term energized operation. This sealing repair process is simple and can complete a single-hole repair within 5 minutes.

[0023] Optionally, the total thickness of the water-blocking insulating tape and PVC tape covering is ≥1.5 mm.

[0024] In the above technical solution, this thickness can effectively resist moisture penetration in long-term immersion and humid environments, ensuring that the repaired area meets the IP68 waterproof rating requirements.

[0025] Compared with the prior art, the present invention has at least the following advantages: (1) This invention sets up several gas sampling points on the cable under test and drills gas sampling holes that only act on the corrugated aluminum sheath. The sampling end of the gas detection device is connected to the gas sampling hole with the gas-tight connector. The device extracts the gas in the gas storage space through its built-in infrared spectroscopy unit and gives the concentration of ethane, ethylene, acetylene and carbon monoxide at one time. The analysis results of several gas sampling points are compared with the four-level preset criteria to achieve quantitative assessment of the ablation level. Finally, the gas sampling hole is sealed and repaired. The whole process is carried out outside the cable and does not change its energized operation state, so there is no risk of electric shock. Moreover, the infrared spectroscopy detection technology overcomes the electromagnetic interference on site and achieves accurate and rapid measurement of multi-component characteristic gases, which can meet the detection needs of defects at each stage. At the same time, quantitative diagnosis and rapid response are achieved by comparing data from multiple gas sampling points and classifying by preset criteria. It can achieve rapid, accurate and quantitative diagnosis of ablation defects in the buffer layer of high-voltage cables. (2) The time control of each step of the present invention is ≤4min for drilling, ≤1min for detection and ≤5min for repair. The entire process of “drilling-gas sampling-detection-sealing” can be completed within 10min under energized conditions, realizing rapid detection and recovery on energized site. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the gas intake point distribution of the present invention; Figure 2 This is a flowchart of the on-site detection method for ablation defects in the buffer layer of high-voltage cables according to the present invention; Figure 3 This invention provides a diagnostic standard for the severity of defects based on the concentration of characteristic gases. Detailed Implementation

[0027] The present invention will now be described through specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of the inventive concept are included in the present invention, and the scope of protection of the present invention is defined by the appended claims and any equivalents thereof.

[0028] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Unless otherwise specified, the raw materials and equipment used in this invention are conventional in the art and can be obtained through conventional commercial means; unless otherwise specified, the methods used in this invention are conventional methods in the art.

[0029] Example 1: Reference Figure 1 to Figure 3As shown, this invention provides a method for on-site detection of ablation defects in the buffer layer of a high-voltage cable. The high-voltage cable includes a buffer layer, a corrugated aluminum sheath, and an outer sheath arranged from the inside out. A gas storage space for storing decomposition gases from the buffer layer is formed between the buffer layer and the corrugated aluminum sheath. The on-site detection method includes the following steps: S1: Mark three or more air sampling points on the cable to be tested using a positioning marking tool. Remove the outer sheath with a length of 8-12 cm at the air sampling points to expose the corrugated aluminum sheath, and drill air sampling holes at the crests of the corrugated aluminum sheath. S2: Connect the gas sampling end of the gas detection device to the gas intake port through the airtight connector, extract the gas in the gas storage space and perform infrared spectroscopy analysis to obtain the analysis results of the concentration of ethane, ethylene, acetylene and carbon monoxide. The number of gas detection devices corresponds to the number of gas intake ports. S3: Compare the analysis results of several gas sampling points with preset criteria, and quantitatively diagnose the ablation status into four levels: no ablation, suspected ablation, ablation present or severe ablation, and give corresponding treatment suggestions: no treatment required, planned maintenance or replacement recommended. S4: After the test is completed, the air intake hole is sealed and repaired to restore the seal of the outer sheath.

[0030] like Figure 3 As shown, the preset criterion is: a) If ethane, ethylene, and acetylene are all <10 ppm, it is determined that there is no ablation; b) If ethane and ethylene concentrations are 10–100 ppm, the condition is considered a suspected ablation. c) If ethane and ethylene concentrations are >100 ppm, it is considered that ablation has occurred and the product should be included in the maintenance plan; d) If ethane and ethylene concentrations are greater than 500 ppm and carbon monoxide concentrations are greater than 10,000 ppm, the cable is considered severely ablated and replacement is recommended.

[0031] Furthermore, if three or more consecutive gas sampling points on the same cable under test reach the levels of b), c), or d), line-level treatment should be initiated according to the corresponding risk level; otherwise, localized targeted treatment should be carried out according to the single-point risk level.

[0032] This invention employs an innovative design of "external opening - airtight gas sampling - rapid repair," allowing the entire process to be performed outside the cable without altering its energized operating state. The entire inspection process does not damage the cable's main insulation structure, eliminating the risk of electric shock. It can complete the entire process of "gas sampling - inspection - recovery - rating" under energized conditions. Furthermore, this invention utilizes infrared spectroscopy detection technology, unaffected by the on-site electromagnetic environment, enabling precise and rapid measurement of multi-component characteristic gases to meet the detection needs of defects at each stage. In addition, by comparing the analysis results from several gas sampling points with preset criteria, this invention can achieve rapid, accurate, and quantitative diagnosis of ablation defects in the buffer layer of high-voltage cables.

[0033] This invention also constructs a threshold system that corresponds one-to-one between the concentration of multi-component characteristic gases and the ablation level: ethane and ethylene, as the main products of thermal decomposition of the buffer layer, have concentration changes that directly reflect the ablation progress. Low-concentration acetylene can confirm pure ablation defects without severe discharge, while high-concentration CO indicates that ablation has triggered severe thermal decomposition. Ethane and ethylene are used as the core indicators for ablation judgment, acetylene is used to help eliminate interference, and carbon monoxide is used as an indicator of severe ablation, forming a scientifically rigorous quantitative judgment basis. This system completely eliminates the limitations of traditional detection relying on the experience of maintenance personnel, providing clear and unified operational standards for on-site operations. It effectively avoids early defect omissions or over-repair due to judgment errors, ensuring timely intervention at critical stages of ablation defect development, minimizing the risk of cable breakdown, and avoiding missing the optimal maintenance window. Meanwhile, by defining the boundaries between line-level and single-point defects, a three-dimensional balance of "safety assurance, operation and maintenance efficiency, and cost control" has been achieved. This not only accurately prevents and controls the safety risks of systemic defects, but also optimizes the allocation of operation and maintenance resources for local defects, providing key technical support for the long-term management of high-voltage cable buffer layer ablation defects.

[0034] In this invention, the gas detection device is a portable FTIR-electrochemical composite detector, which integrates an infrared spectroscopy unit, a hydrogen sensor, and a pressure sensor. The infrared spectroscopy unit analyzes and provides the concentrations of ethane, ethylene, acetylene, and carbon monoxide, and provides the analysis results in one go. Since the more severe the cable erosion, the higher the H2 concentration, a hydrogen sensor is set up to capture the H2 concentration signal, supplementing the detection blind spot of the infrared spectrum and forming a multi-dimensional gas monitoring system to avoid defective misjudgments caused by the omission of a single component. A pressure sensor is set up to verify the sealing of the gas sampling channel and ensure the effectiveness of sampling.

[0035] Further, in step S1, the gas sampling points are set up as follows: the first gas sampling point starts at a distance of ≥10 m from the cable joint to be tested, and one point is arranged every 80~120 m along the cable route. Using "≥10 m from the cable joint to be tested" as the starting point avoids structural interference and electric field distortion areas near the joint. Subsequent gas sampling points are flexibly arranged at intervals of 80~120 m along the cable route. This avoids early defect omissions due to excessive spacing, and also prevents unnecessary maintenance costs and workload increases due to excessively dense spacing, achieving a balance between detection accuracy and maintenance costs. As an example, Figure 1 shows one arrangement of gas sampling points: gas sampling points start at a distance of 10 m from the cable joint and are arranged sequentially every 100 m along the cable route.

[0036] Furthermore, in step S1, an air intake hole is drilled using an electric drill. The electric drill is equipped with a limiting ring to restrict the drilling depth, thereby preventing damage to the buffer layer. The air intake hole is drilled in one pass using a hand-held electric drill with a limiting ring. The limiting ring strictly controls the drilling depth within a safe range that does not touch the inner buffer layer and the main insulation layer, eliminating the risk of damage to the buffer layer and the main insulation layer caused by excessive drilling. At the same time, the limiting ring enables standardized and safe drilling operations.

[0037] Furthermore, in step S2, the airtight connector includes a silicone nozzle that is sealed to the air intake port, and a flexible tube with one end connected to the silicone nozzle and the other end connected to the gas sampling end of the gas detection device. The silicone nozzle has excellent elastic deformation capability and can tightly fit the hole wall and the surrounding aluminum sheath surface through its own deformation to form a reliable sealing interface; the flexible tube connects the silicone nozzle and the gas detection device, providing high flexibility and avoiding the limitation of operating space imposed by rigid connections.

[0038] Further, in step S4, the sealing and repair process involves: inserting a repair aluminum nail into the air intake hole, filling it with a waterproof metal repair agent, and then sequentially covering it with water-blocking insulating tape and PVC tape to seal the air intake hole. The repair aluminum nail fills the core area of ​​the hole and possesses excellent rigidity and structural stability, reinforcing the strength of the aluminum sheath structure at the air intake hole after its insertion; the waterproof metal repair agent fills the tiny gaps between the repair aluminum nail and the air intake hole wall, forming a dense, rigid sealing layer after curing; the lower water-blocking insulating tape provides water blocking and insulation, while the upper PVC tape provides protection and reinforcement. The multi-layered sealing structure formed by these two layers meets the short-term sealing and restoration requirements of the cable after testing and ensures the safety and reliability of long-term energized operation. This sealing and repair process is simple and can complete a single-hole repair within 5 minutes.

[0039] To ensure that the repaired area meets the IP68 waterproof rating requirement, the total thickness of the water-blocking insulating tape and PVC tape covering should be ≥1.5 mm.

[0040] To facilitate understanding of the above content, as an example, in one specific implementation, a YJLW03-1×800 mm type power supply with an operating voltage of 110 kV is selected. 2 The XLPE corrugated aluminum sheathed cable has a total length of approximately 1.2 km and two sets of intermediate joints. The on-site detection method for ablation defects in the buffer layer of this high-voltage cable is as follows: S1: Select gas sampling points on the cable to be tested. Starting from 10 m from the A end of the connector, one gas sampling point is arranged every 100 m along the cable route, for a total of 8 gas sampling points, numbered Q1 to Q8, covering the entire high-risk area of ​​the cable section. At each gas sampling point, use a cable outer sheath stripping tool to cut off a 10 cm length of the PVC outer sheath to expose the surface of the corrugated aluminum sheath. After cleaning up the debris, mark the drilling position at the highest point of the corrugated aluminum sheath with a marker. Use a hand drill with a 4 mm limit ring and a Φ3 mm carbide drill bit to drill through the corrugated aluminum sheath in one go to connect the gas storage space with the outside. The depth of the gas sampling hole is 4 mm, and the hole opening is neat and burr-free. S2: Immediately screw the Φ3 mm silicone nozzle into the gas intake port. Connect the nozzle tail to a 6 mm polyurethane tubing via a quick-connect fitting. Connect the other end of the tubing to the gas inlet of the gas detection device, ensuring a tight connection. Extract gas from the storage space and perform infrared spectroscopy analysis. Before detection, perform a background scan: Open the "Background" solenoid valve, extract ambient air for 20 seconds, and click "Scan Background" to obtain a reference spectrum. Then switch to the "Test" valve, extract gas from the port for 20 seconds, and click "Scan Spectrum." The instrument operates within the wavenumber range of 4000–400 cm⁻¹. -1 Resolution 4 cm -1 The sample spectrum was acquired under four scan conditions, and the hydrogen concentration and pressure values ​​were read simultaneously. The system automatically integrated the characteristic absorption peaks and output the concentrations of ethane, ethylene, acetylene, and CO within 30 seconds.

[0041] S3: Compare the analysis results of several gas sampling points with preset criteria, and quantitatively diagnose the ablation status into four levels: no ablation, suspected ablation, ablation present or severe ablation, and give corresponding treatment suggestions: no treatment required, planned maintenance or replacement recommended. S4: After inspection, the borehole is sealed and repaired. First, aluminum shavings are cleaned from the air intake opening, wiped with acetone and dried. Then, a Φ3×5 mm aluminum alloy repair nail is inserted, with the nail head flush with the surface of the aluminum sheath. Epoxy aluminum powder waterproof metal repair agent is then injected, and the filling is completed and smoothed within 3 minutes. The repair agent initially sets within 15 minutes and reaches sealing strength within 2 hours. After the repair agent has cured, three layers of water-blocking insulating tape (25 mm wide, 50% overlap) and three layers of PVC self-adhesive tape are wrapped in sequence, with a total thickness ≥1.5 mm, restoring the sealing performance of the outer sheath and meeting the IP68 protection level requirements. Finally, the insulation resistance between the repair nail and the aluminum sheath is tested with a 1 kV megohmmeter, and all values ​​are greater than 500 MΩ, meeting the on-site operation requirements.

[0042] The preset criterion is: a) If ethane, ethylene, and acetylene are all <10 ppm, it is determined that there is no ablation; b) If ethane and ethylene concentrations are 10–100 ppm, the condition is considered a suspected ablation, and further verification is performed using infrared thermography. c) If ethane and ethylene concentrations are greater than 100 ppm, ablation is considered to be present; d) If ethane and ethylene concentrations are greater than 500 ppm and CO concentrations are greater than 10,000 ppm, the cable is considered severely eroded and replacement is recommended.

[0043] In this embodiment, the detection results at point Q3 are: ethane concentration 85 ppm, ethylene concentration 78 ppm, acetylene concentration 6 ppm, and carbon monoxide concentration 4200 ppm; the detection results at point Q6 are: ethane concentration 520 ppm, ethylene concentration 480 ppm, acetylene concentration 12 ppm, and carbon monoxide concentration 12000 ppm; at all other points, the ethane and ethylene concentrations are all below 50 ppm, and the carbon monoxide concentration is below 3000 ppm.

[0044] In this embodiment, although points Q3 and Q6 are abnormal, they are not continuous and there are only two points, so they do not constitute line-level diagnostic conditions. They are temporarily treated as single-point defects, and the subsequent detection cycle will be shortened to 3 months.

[0045] This embodiment is completed entirely under energized conditions, with an average operation time of 10 minutes per point, including 4 minutes for drilling, 1 minute for inspection, and 5 minutes for repair. It enables rapid, quantitative, and on-site detection and reliable recovery of ablation defects in the buffer layer of high-voltage cables. It is suitable for live inspection and condition assessment in complex environments such as cable wells, tunnels, and cable trays, and is of great significance for ensuring the safe operation of high-voltage cables.

[0046] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for on-site detection of ablation defects in the buffer layer of a high-voltage cable, wherein the high-voltage cable comprises a buffer layer and a corrugated aluminum sheath arranged from the inside out, and a gas storage space for storing decomposition gases of the buffer layer is formed between the buffer layer and the corrugated aluminum sheath, characterized in that, The on-site testing method includes the following steps: S1: Set up a gas sampling point on the cable to be tested, and drill a gas sampling hole at the gas sampling point; S2: Connect the gas sampling end of the gas detection device to the gas intake port through the airtight connector, extract the gas in the gas storage space and perform infrared spectroscopy analysis to obtain the analysis results of the concentration of ethane, ethylene, acetylene and carbon monoxide. S3: Compare the analysis results of the gas sampling point with the preset criteria to determine the ablation level of the cable under test; S4: Perform sealing and repair treatment on the air intake hole; The gas detection device is equipped with an infrared spectroscopy unit.

2. The method for on-site detection of ablation defects in the buffer layer of a high-voltage cable according to claim 1, characterized in that, The preset criterion is: a) If ethane, ethylene, and acetylene are all <10 ppm, it is determined that there is no ablation; b) If ethane and ethylene concentrations are 10–100 ppm, the condition is considered a suspected ablation. c) If ethane and ethylene concentrations are >100 ppm, it is considered that ablation has occurred and the product should be included in the maintenance plan; d) If ethane and ethylene concentrations are greater than 500 ppm and carbon monoxide concentrations are greater than 10,000 ppm, the cable is considered severely ablated and replacement is recommended.

3. The method for on-site detection of ablation defects in the buffer layer of a high-voltage cable according to claim 2, characterized in that, The cable under test has at least 3 gas sampling points. According to the preset criteria, if 3 or more consecutive gas sampling points on the cable under test reach b), c), or d), line-level processing should be initiated according to the corresponding risk level; otherwise, local targeted processing should be carried out according to the single-point risk level.

4. A method for on-site detection of ablation defects in the buffer layer of a high-voltage cable according to claim 1, characterized in that, The cable under test is provided with several gas sampling points. The gas sampling points are set up as follows: the first gas sampling point starts from a distance of ≥10 m from the joint of the cable under test, and one point is arranged every 80~120 m along the cable route.

5. The method for on-site detection of ablation defects in the buffer layer of a high-voltage cable according to claim 1, characterized in that, In step S1, an air intake hole is drilled using an electric drill. The electric drill is equipped with a limiting ring to restrict the drilling depth in order to avoid damaging the buffer layer.

6. The method for on-site detection of ablation defects in the buffer layer of a high-voltage cable according to claim 1, characterized in that, The gas detection device is also equipped with a hydrogen sensor.

7. The method for on-site detection of ablation defects in the buffer layer of a high-voltage cable according to claim 1, characterized in that, The gas detection device is also equipped with a pressure sensor.

8. The method for on-site detection of ablation defects in the buffer layer of a high-voltage cable according to claim 1, characterized in that, In step S2, the airtight connector includes a silicone nozzle that is sealed to the air intake hole, and a flexible tube with one end connected to the silicone nozzle and the other end connected to the gas sampling end of the gas detection device.

9. A method for on-site detection of ablation defects in the buffer layer of a high-voltage cable according to any one of claims 1 to 8, characterized in that, In step S4, the sealing and repair process is as follows: insert a repair aluminum nail into the air intake hole, fill it with waterproof metal repair agent, and then wrap it with water-blocking insulating tape and PVC tape in sequence to seal the air intake hole.

10. A method for on-site detection of ablation defects in the buffer layer of a high-voltage cable according to claim 9, characterized in that, The total thickness of the water-blocking insulating tape and PVC tape covering is ≥1.5 mm.

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