Method and system for analyzing ablation characteristic gas of high-voltage cable buffer layer and grading evaluation of cable state

Abstract

The application belongs to the field of electrical insulation detection of power equipment, and discloses a high-voltage cable buffer layer ablation characteristic gas analysis and cable state grading evaluation method and system. Through rapid analysis of gas components, the ablation phenomenon of the cable can be found early, and potential power failures and safety hazards can be avoided. Through the relationship between gas components and concentration and the ablation degree, accurate evaluation can be provided to help formulate targeted maintenance and replacement plans. The application can timely monitor and evaluate to reduce the risk of accidents caused by cable failures, and enhance the safety and reliability of the power system. By finding problems in advance, the application reduces power outages and maintenance costs caused by sudden failures, thereby improving overall economic benefits. The gas analysis data of the application can provide a basis for long-term monitoring and management of the cable operating state, and support more scientific maintenance strategies.

Description

Technical Field

[0001] This invention belongs to the field of electrical insulation testing of power equipment, specifically involving a method and system for analyzing the characteristic gases of high-voltage cable buffer layer ablation and evaluating cable condition classification. Background Technology

[0002] High-voltage cables are critical equipment in power transmission networks, and their reliability is essential for the safe and stable operation of the power grid. However, after years of operation, various faults frequently occur in cables, with cable faults caused by defects in the cable buffer layer accounting for more than 80% of the total. Therefore, it is of great significance to inspect the condition of the cable buffer layer. Among the methods for inspecting the condition of the cable buffer layer, electrical parameter measurement and X-ray detection have certain limitations. When the main insulation of the cable is not broken down, weak partial discharge signals are difficult to identify effectively, while X-rays are severely affected by the shooting angle and distance, and the testing is complex and difficult to apply.

[0003] Existing research indicates that defects in cable buffer layers are mainly classified as corrosion and overheating. Buffer cotton and the aluminum sheath undergo chemical reactions under conditions of electrical stress, thermal stress, and humidity, generating characteristic gases such as hydrogen, ethane, ethylene, and acetylene. The types and concentrations of these gases differ under different conditions, thus the condition of the buffer layer can be determined by gas detection. However, conventional gas chromatography gas detection methods suffer from drawbacks such as long detection cycles, complex operation, difficult maintenance, and limited on-site testing capabilities. Therefore, finding a rapid, safe detection method and a comprehensive gas analysis system is crucial. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of conventional gas chromatography gas detection methods, such as long detection cycle, complex operation, difficult maintenance, and difficulty in achieving on-site detection, and to provide a method and system for analyzing characteristic gases of high-voltage cable buffer layer ablation and evaluating cable condition.

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

[0006] A method for analyzing characteristic gases of high-voltage cable buffer layer ablation and assessing cable condition includes the following steps:

[0007] Drill holes in the aluminum sheath of the high-voltage cable to extract and collect the gas generated during the ablation process of the cable buffer layer inside the aluminum sheath.

[0008] Infrared spectra of ablation sample gas were collected and analyzed. After filtering and noise reduction, baseline correction, feature variable extraction and quantitative modeling analysis, the concentrations of characteristic components such as methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide and carbon dioxide in the sample gas were obtained. Hydrogen concentration was detected by electrochemical or metal oxide semiconductor sensors.

[0009] The degree of ablation of the cable buffer layer is evaluated by classifying the concentration of characteristic components in the sample gas and using the threshold method or weighting method. It is divided into five states: normal, internal moisture, mild ablation, moderate ablation, and severe ablation.

[0010] The infrared spectra of the ablation sample gas were collected and analyzed. After filtering and noise reduction, baseline correction, characteristic variable extraction, and quantitative modeling analysis, the specific methods for obtaining the concentrations of characteristic components such as methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide, and carbon dioxide in the sample gas are as follows:

[0011] Noise interference in the infrared spectrum is eliminated by using a Savitzky-Golay filter;

[0012] An improved adaptive extended Gaussian peak derivative reweighted least squares method is used to process infrared spectra to solve the baseline drift problem in infrared spectra.

[0013] An extended Gaussian peak is added to the infrared spectrum, a derivative term of the spectral and baseline differences is added during the iteration process, and the penalty coefficient is adaptively adjusted.

[0014] The infrared spectral characteristic variables of ablation characteristic gases were screened by combining variable influence values ​​and cluster analysis. The variables were the spectral data obtained from the scan and the analyte concentration information contained therein. The spectral data were multiplied by a coefficient greater than 1 and less than 1, respectively. Partial least squares models were established for the new variables, and the corresponding root mean square error of cross-validation was obtained. The variable influence value is the difference of the root mean square error of cross-validation.

[0015] Cluster analysis is reflected in the frequency of the occurrence of the optimal model in the variable space. In each iteration, variables with low influence values ​​and low frequency of occurrence in the optimal model are eliminated, thereby realizing the quantitative analysis of the concentration of each component of the ablation characteristic gas.

[0016] The degree of cable buffer layer erosion is assessed based on the concentration of characteristic components in the sample gas. A threshold method or weighted method is used to determine the degree of erosion, categorizing it into five states: normal, internally damp, mild erosion, moderate erosion, and severe erosion. The specific methods are as follows:

[0017] The threshold-based method for classifying and evaluating the state of cable buffer layers is as follows:

[0018] When the volume percentage concentration of hydrogen in the sample gas is greater than T0, it indicates that the cable buffer layer is damp. When the sum of the volume percentage concentrations of ethane, ethylene, and acetylene is lower than T1, the buffer layer is normal. When it is between T1 and T2, it is mild ablation. When it is between T2 and T3, it is moderate ablation. When it is above T3, it is severe ablation.

[0019] The weighted method-based approach for classifying and evaluating the condition of cable buffer layers is as follows:

[0020] The volume percentage concentrations of the three gases detected, namely ethane, ethylene, and acetylene, were C i (i = 1, 2, 3), with weights assigned to W respectively. i (i = 1, 2, 3), the ablation index F is introduced to characterize the state of the cable buffer layer, and the calculation formula is:

[0021]

[0022] When the obtained ablation index F is less than F1, it indicates that the cable buffer layer is normal; when the value is between F1 and F2, it indicates that mild ablation has occurred inside the buffer layer; when the value is between F2 and F3, it indicates that moderate ablation has occurred; and when the value is higher than F3, it indicates that severe ablation has occurred.

[0023] Data from a preset gas database is compared with data from the gas database, with a concentration threshold T0 of 5000 × 10⁻⁶. -6 T1 is 500×10 -6 T2 is taken as 1000×10 -6 T3 is taken as 2000×10 -6 Weights W1 are set to 0.3, W2 to 0.5, and W3 to 0.2; the ablation index F1 is set to 100 × 10⁻⁶. -6 F2 is 500×10 -6 F3 takes 1000×10 -6 .

[0024] A high-voltage cable buffer layer ablation characteristic gas analysis and cable condition classification assessment system includes a gas collection device, a gas analysis device, and a cable monitoring room. The gas collection device and the gas analysis device are integrated into one unit. The gas collection device collects the gas generated during the buffer layer ablation process, and the gas analysis device analyzes the gas composition and corresponding concentration to obtain the gas composition and corresponding concentration. The gas composition and corresponding concentration are transmitted to the cable monitoring room, where the cable monitoring room classifies and assesses the degree of cable ablation based on the type and concentration of the ablation gas.

[0025] The gas collection device includes a drilling module, an extraction module, a drying module, and a gas collection module. These four modules are connected in sequence and can collect gas from the cavity inside the aluminum sheath of the cable by drilling, extraction, and drying in sequence.

[0026] The gas analysis device includes a Fourier transform infrared spectrometer, a hydrogen detection module, a main control module, a data acquisition module, and a data processing module;

[0027] Fourier transform infrared spectrometer is used to collect infrared spectra of methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide, and carbon dioxide.

[0028] The hydrogen detection module uses an electrochemical or metal oxide semiconductor sensor to detect hydrogen concentration;

[0029] The main control module is used to set the parameters of the Fourier transform infrared spectrometer and the hydrogen detection module and to send control commands.

[0030] The data acquisition module uses temperature, humidity, and air pressure sensors to collect temperature, humidity, and air pressure parameters in the gas.

[0031] The data processing module is used to filter and denoise the collected infrared spectra, perform baseline correction, extract feature variables, and perform quantitative modeling analysis to obtain the corresponding gas concentrations and acquire the hydrogen concentration.

[0032] The gas analysis device also includes a power supply module, an environmental monitoring module, a display module, an early warning module, and a wireless communication module;

[0033] The power module is used for power supply;

[0034] The environmental monitoring module includes lighting and a high-definition camera for real-time detection of the cable well site conditions;

[0035] The display module is a touch screen used for human-computer interaction, receiving spectrometer parameter settings and spectral scanning operation commands, and displaying gas detection results;

[0036] The early warning module is a voice alarm controller, which is used to flash the panel indicator light and display and broadcast alarm information when the detection result is abnormal;

[0037] The wireless module, which can be a WiFi module, NB-IoT module, or LoRa module, is used to communicate with the cable compartment.

[0038] The Fourier transform infrared spectrometer first requires initial parameter configuration, with the initial wavenumber set to 4000 cm⁻¹. -1 The termination wavenumber is set to 400cm. -1 Or 500cm -1 The resolution can be set to 1cm. -1 2cm -1 Or 4cm -1 The scanning frequency was set to 4 times. The gas chamber was evacuated to 0.04 MPa by a pressure sensor, or nitrogen or argon gas, which has no absorption peak in the infrared region, was injected into the gas chamber to obtain the background spectrum. Next, the sample gas was ablated by the buffer layer and its absorption spectrum was scanned. At the same time, environmental parameters of the gas, including temperature and pressure, were collected to obtain the compensation coefficient, which was used to compensate for the gas concentration detection value. Finally, the hydrogen concentration was combined and transmitted to the main control module.

[0039] The method for analyzing characteristic gases of high-voltage cable buffer layer ablation and assessing cable condition classification, with the following steps as part of the on-site operation procedure:

[0040] Step S1: Turn on the main power and the system initializes;

[0041] Step S2: After stripping the outer sheath of the cable and drilling an air hole, install the air valve;

[0042] Step S3: The sample gas is drawn into the gas analysis system, and the system performs gas concentration analysis and records various parameters;

[0043] Step S4: The detection data is wirelessly transmitted to the ground cable monitoring room, compared with the gas database, and the status of the cable buffer layer is diagnosed in real time.

[0044] Step S5: Seal and repair the air intake hole, and mark the drilling positions around the outer sheath.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] This invention enables early detection of cable erosion through rapid analysis of gas composition, preventing potential power failures and safety hazards. By analyzing the relationship between gas composition and concentration and the degree of erosion, this invention provides accurate assessments, aiding in the development of targeted maintenance and replacement plans. Timely monitoring and assessment reduce the risk of accidents caused by cable faults, enhancing the safety and reliability of power systems. Early problem detection reduces power outages and repair costs due to sudden failures, thereby improving overall economic efficiency. The gas analysis data from this invention provides a basis for long-term monitoring and management of cable operating conditions, supporting more scientific maintenance strategies. This invention provides feedback for improvements in cable materials and structures, promoting the development of higher-performance cables. In summary, this invention can preliminarily determine the condition of the cable buffer layer, facilitating subsequent maintenance and repair, and is of great significance for the safe and reliable operation of cable power systems. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the system of the present invention;

[0048] Figure 2 This is a flowchart of the process of the present invention;

[0049] Figure 3 This is a flowchart of the on-site operation of the present invention;

[0050] Figure 4 This is a flowchart of the high-voltage cable buffer layer status classification and evaluation method in this invention. Detailed Implementation

[0051] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0052] Example 1:

[0053] A method for analyzing characteristic gases of high-voltage cable buffer layer ablation and assessing cable condition includes the following steps:

[0054] S1. Drill holes in the aluminum sheath of the high-voltage cable to extract and collect the gas generated during the ablation process of the cable buffer layer inside the aluminum sheath.

[0055] S2, collects and analyzes the infrared spectrum of the ablation sample gas. After filtering and noise reduction, baseline correction, feature variable extraction, and quantitative modeling analysis, the concentrations of characteristic components such as methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide, and carbon dioxide in the sample gas are obtained. The hydrogen concentration is detected by an electrochemical or metal oxide semiconductor sensor.

[0056] S3, based on the concentration of characteristic components in the sample gas, classifies and evaluates the degree of ablation of the cable buffer layer using the threshold method or weighting method, and divides it into five states: normal, internal moisture, mild ablation, moderate ablation, and severe ablation.

[0057] Example 2:

[0058] A system for analyzing the characteristic gases of high-voltage cable buffer layer ablation and assessing cable condition includes:

[0059] A gas collection device is used to collect the gas generated during the ablation process of the cable buffer layer.

[0060] A gas analysis device, integrated with a gas collection device, is used to analyze the collected gas to obtain its composition and corresponding concentration.

[0061] The cable monitoring room is used to classify and assess the degree of cable erosion based on the composition and concentration of the gas.

[0062] Example 3:

[0063] The infrared spectra of the ablation sample gas were collected and analyzed. After filtering and noise reduction, baseline correction, characteristic variable extraction, and quantitative modeling analysis, the specific methods for obtaining the concentrations of characteristic components such as methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide, and carbon dioxide in the sample gas are as follows:

[0064] Noise interference in the infrared spectrum is eliminated by using a Savitzky-Golay filter;

[0065] An improved adaptive extended Gaussian peak derivative reweighted least squares method is used to process infrared spectra to solve the baseline drift problem in infrared spectra.

[0066] An extended Gaussian peak is added to the infrared spectrum, a derivative term of the spectral and baseline differences is added during the iteration process, and the penalty coefficient is adaptively adjusted.

[0067] The infrared spectral characteristic variables of ablation characteristic gases were screened by combining variable influence values ​​and cluster analysis. The variables were the spectral data obtained from the scan and the analyte concentration information contained therein. The spectral data were multiplied by a coefficient greater than 1 and less than 1, respectively. Partial least squares models were established for the new variables, and the corresponding root mean square error of cross-validation was obtained. The variable influence value is the difference of the root mean square error of cross-validation.

[0068] Cluster analysis is reflected in the frequency of the occurrence of the optimal model in the variable space. In each iteration, variables with low influence values ​​and low frequency of occurrence in the optimal model are eliminated, thereby realizing the quantitative analysis of the concentration of each component of the ablation characteristic gas.

[0069] Example 4:

[0070] The threshold-based method for classifying and evaluating the state of cable buffer layers is as follows:

[0071] When the volume percentage concentration of hydrogen in the sample gas is greater than T0, it indicates that the cable buffer layer is damp. When the sum of the volume percentage concentrations of ethane, ethylene, and acetylene is lower than T1, the buffer layer is normal. When it is between T1 and T2, it is mild ablation. When it is between T2 and T3, it is moderate ablation. When it is above T3, it is severe ablation.

[0072] The weighted method-based approach for classifying and evaluating the condition of cable buffer layers is as follows:

[0073] The volume percentage concentrations of the three gases detected, namely ethane, ethylene, and acetylene, were C i (i = 1, 2, 3), with weights assigned to W respectively. i (i = 1, 2, 3), the ablation index F is introduced to characterize the state of the cable buffer layer, and the calculation formula is:

[0074]

[0075] When the obtained ablation index F is less than F1, it indicates that the cable buffer layer is normal; when the value is between F1 and F2, it indicates that mild ablation has occurred inside the buffer layer; when the value is between F2 and F3, it indicates that moderate ablation has occurred; and when the value is higher than F3, it indicates that severe ablation has occurred.

[0076] Data from a preset gas database is compared with data from the gas database, with a concentration threshold T0 of 5000 × 10⁻⁶. -6T1 is 500×10 -6 T2 is taken as 1000×10 -6 T3 is taken as 2000×10 -6 Weights W1 are set to 0.3, W2 to 0.5, and W3 to 0.2; the ablation index F1 is set to 100 × 10⁻⁶. -6 F2 is 500×10 -6 F3 takes 1000×10 -6 .

[0077] Example 5:

[0078] See Figure 1 A system for analyzing the ablation characteristics of high-voltage cable buffer layers using gas and assessing cable condition, including a gas collection device, a gas analysis device, and a cable monitoring room.

[0079] The gas collection device and gas analysis device are integrated into one unit, with overall dimensions of 50cm*40cm*30cm. It is equipped with four casters at the bottom and a handle on the side for easy on-site transportation. The gas collection device collects the gas generated during the ablation process of the buffer layer, and the gas analysis device analyzes the gas composition and corresponding concentration. The relevant data is transmitted to the cable monitoring room. Based on the type and concentration of the ablation gas, a graded assessment is performed to determine the degree of cable ablation. The core of the gas analysis device is the gas concentration analysis unit, which includes a Fourier transform infrared spectrometer and a hydrogen detection module. The Fourier transform infrared spectrometer can obtain the infrared spectra of methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide, and carbon dioxide. After filtering, noise reduction, baseline correction, feature variable extraction, and quantitative model establishment, the concentration of each component gas can be obtained. The hydrogen detection module is an electrochemical sensor that can detect hydrogen concentration.

[0080] The gas collection device includes a drilling module, an extraction module, a drying module, and a gas collection module, which are connected in sequence. The drilling module is a limit hand drill with an adjustable exposed drill bit length ranging from 3mm to 6mm, ensuring that the drill bit can penetrate the aluminum sheath of the cable after the outer sheath has been stripped without damaging the buffer layer structure. The extraction module uses a small air pump with a pumping flow rate of 1000ml / min, which can extract the gas from the cavity of the aluminum sheath. The drying module is a drying tube filled with color-changing silica gel and molecular sieves, which can filter and remove moisture and aluminum sheath debris left after drilling, reducing interference. The gas collection module is an adjustable three-way Y-valve, which can be used to pass gas into a gas bag for storage or into a gas analysis device for detection.

[0081] The gas analysis range of the Fourier transform infrared spectrometer is 1×10⁻⁶. -6 ~50000×10 -6 The detection limit is 1×10⁻⁶. -6The maximum relative error for each component is ±20% of the reading value ±5×10. -6 The detection cycle is less than 120 seconds. The hydrogen detection module has a hydrogen detection range of 0–40000 × 10⁻⁶. -6 The resolution is 1×10 -6 The maximum relative error of the detection is ±3% of the reading value ±1×10⁻⁶. -6 .

[0082] The gas analysis device includes a data acquisition module and a data processing module. The data acquisition module consists of temperature, humidity, and pressure sensors, which can collect the temperature, humidity, and pressure of the gas. The temperature detection range is -40℃ to +80℃ with an accuracy of ±0.5℃; the humidity detection range is 0 to 100%RH with an accuracy of 3%RH; and the pressure detection range is 30 to 125kPa with an accuracy of ±8Pa. The data processing module is an STM32 microcontroller with an ARM Cortex-M3 core, which can collect and process gas parameters. The specific process is as follows: the microcontroller communicates with the sensors, sends a fixed request frame to the sensor, receives a response frame, and obtains the actual temperature, humidity, and pressure data according to the data frame format. This data can be used as cable operating status parameters or for correction in subsequent gas concentration analysis.

[0083] The core of the gas analysis device is an embedded industrial control computer that communicates with the data processing module and the gas concentration analysis unit module. It is the control center of the entire system, controlling the system's spectrometer, microcontroller, solenoid valve, and gas pump. It can process the spectral data, temperature, humidity, and pressure data of the analyzed gas, and receive user commands for spectrometer parameter settings, spectral scanning, and sensor detection operations.

[0084] The gas analysis device also includes a power module, an environmental monitoring module, a display module, an early warning module, and a wireless module. The power module is a battery that powers the entire system. The environmental monitoring module consists of a lighting fixture and a high-definition camera, which can be used to detect the on-site conditions of the cable well in real time. The display module is a touch screen that allows for human-machine interaction, receiving user spectrometer parameter settings and spectral scanning operations, and displaying gas detection results. The early warning module is a voice alarm controller; when the detection results are abnormal, the panel indicator light flashes, and an alarm message is displayed and broadcast. The wireless module is an HC-14 wireless module, which is a 433MHz transparent transmission module capable of long-distance transmission up to 3 kilometers and can communicate wirelessly with the cable monitoring room outside the wellhead.

[0085] The gas concentration analysis method follows these steps: First, a Savitzky-Golay filter is used to eliminate noise interference in the original spectrum. Then, an improved adaptive extended Gaussian peak derivative reweighted least squares method is employed to address baseline drift in the spectrum. This method adds an extended Gaussian peak to the spectrum, incorporates the derivative term of the difference between the spectrum and the baseline during iteration, and adaptively adjusts the penalty coefficient. Finally, a combination of variable influence values ​​and cluster analysis is used to screen for infrared spectral characteristic variables of the ablation characteristic gases. The variables are the spectral data obtained from the scan and the analyte concentration information contained therein. The spectral data are multiplied by a factor greater than 1 and less than 1, respectively. The coefficient 1 is used to establish partial least squares models for the new variables, and the corresponding root mean square error of cross-validation is obtained. The influence value of the variable is the difference of the root mean square error of cross-validation. Cluster analysis is reflected in the frequency of the optimal model in the variable space. That is, in each iteration, the influence value and frequency of the variable are calculated at the same time. According to the influence value of the variable, the variable is divided into elite variables and ordinary variables using weighted bootstrap sampling technology. Variables with low frequency are removed from the ordinary variables. This ensures that variables with low influence value and variables with low frequency of occurrence in the optimal model are removed in each iteration, thereby realizing the quantitative analysis of the concentration of each component of the ablation characteristic gas.

[0086] The workflow of a gas analysis system is as follows: Figure 2 As shown, the Fourier transform spectrometer requires initial parameter configuration; the initial wavenumber is set to 4000 cm⁻¹. -1 The termination wavenumber is set to 400cm. -1 Or 500cm -1 The resolution can be set to 1cm. -1 2cm -1 Or 4cm -1 The scanning frequency was set to 4 times. The gas chamber was evacuated to the set value P1 by the gas pressure sensor, or nitrogen or argon gas, which has no absorption peak in the infrared region, was injected into the gas chamber to obtain the background spectrum. Then, the temperature, humidity and gas pressure in the environment were collected and the background spectrum and environmental parameters were saved. After the gas sampling port of the cable was installed, the sample gas was introduced into the buffer layer until the gas pressure reached the set value P2. The gas spectrum was scanned and the gas parameters were collected at the same time. The compensation coefficient was obtained to compensate for the gas concentration detection value. Finally, the data was transmitted to the industrial control computer along with the hydrogen concentration and wirelessly transmitted to the cable monitoring room.

[0087] The compensation coefficient is determined by the gas temperature T and pressure P, and the compensated absorbance A1 is determined by equation (1).

[0088]

[0089] In the formula, A1 is the absorbance after compensation, A0 is the absorbance before compensation, T is the gas temperature in °C, and P is the gas pressure in kPa.

[0090] Example 6:

[0091] See Figure 3 A method for analyzing the characteristic gases of high-voltage cable buffer layer ablation and assessing cable condition includes the following steps:

[0092] Step S1: Turn on the main power supply, preheat the system, and then turn on the vacuum pump to create a vacuum.

[0093] Step S2: After stripping the outer sheath of the cable and drilling an air hole with a limit hand drill, install the adjustable air valve;

[0094] Step S3: The sample gas is drawn into the gas analysis system, and the system performs gas concentration analysis and records various parameters;

[0095] Step S4: Wirelessly transmit the detection data to the ground cable monitoring room for further data visualization and real-time diagnosis of the cable buffer layer status by comparing it with the gas database;

[0096] Step S5: Seal and repair the air intake hole, wrap tape around the outer sheath and mark the punching points.

[0097] The flowchart of the high-voltage cable buffer layer condition classification assessment method is as follows: Figure 4 As shown, firstly, four gases—hydrogen, ethane, ethylene, and acetylene—were extracted from the buffer layer sample as characteristic gases. The state of the buffer layer was then classified and diagnosed using a threshold method or a weighting method, resulting in five states: internal moisture, normal, mild ablation, moderate ablation, and severe ablation.

[0098] The threshold-based method for classifying and evaluating the state of cable buffer layers is as follows:

[0099] When the volume percentage concentration of hydrogen in the sample gas being tested is greater than 5000 × 10⁻⁶ -6 This indicates that the inside of the cable buffer layer is damp;

[0100] When the sum of the volume percentage concentrations (SUM) of the three gases (ethane, ethylene, and acetylene) detected is greater than 500 × 10⁻⁶. -6 ~1000×10 -6 When the temperature is below 50×10, it indicates that mild ablation has occurred inside the buffer layer. -6 This is considered normal; a value higher than 1000×10 is acceptable. -6 But below 2000×10 -6 This indicates moderate ablation, exceeding 2000 × 10⁻⁶. -6 This indicates that severe ablation has occurred;

[0101] The weighted method-based approach for classifying and evaluating the condition of cable buffer layers is as follows:

[0102] The volume percentage concentrations of the three gases detected, namely ethane, ethylene, and acetylene, were C i (i = 1, 2, 3), with weights assigned to W respectively. i (i=1,2,3), based on cable ablation gas detection data, with weights of 0.3, 0.5, and 0.2 respectively, an ablation index is introduced to characterize the state of the cable buffer layer.

[0103] The formula for calculating the ablation index F is:

[0104]

[0105] When the obtained ablation index F is less than 100×10 -6 This indicates that the cable buffer layer is normal; the value is within 100×10. -6 ~500×10 -6 When the value is 500×10, it indicates that mild ablation has occurred inside the buffer layer; the value is within the range of 500×10. -6 ~1000×10 -6 This indicates moderate ablation, exceeding 1000 × 10⁻⁶. -6 This indicates that severe ablation has occurred.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for analyzing characteristic gases of high-voltage cable buffer layer ablation and classifying cable condition, characterized in that, Includes the following steps: Drill holes in the aluminum sheath of the high-voltage cable to extract and collect the gas generated during the ablation process of the cable buffer layer inside the aluminum sheath. Infrared spectra of ablation sample gas were collected and analyzed. After filtering and noise reduction, baseline correction, feature variable extraction and quantitative modeling analysis, the concentrations of characteristic components such as methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide and carbon dioxide in the sample gas were obtained. Hydrogen concentration was detected by electrochemical or metal oxide semiconductor sensors. The degree of ablation of the cable buffer layer is evaluated by classifying the concentration of characteristic components in the sample gas and using the threshold method or weighting method. It is divided into five states: normal, internal moisture, mild ablation, moderate ablation, and severe ablation. The infrared spectra of the ablation sample gas were collected and analyzed. After filtering and noise reduction, baseline correction, characteristic variable extraction, and quantitative modeling analysis, the specific methods for obtaining the concentrations of characteristic components such as methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide, and carbon dioxide in the sample gas are as follows: Noise interference in the infrared spectrum is eliminated by using a Savitzky-Golay filter; An improved adaptive extended Gaussian peak derivative reweighted least squares method is used to process infrared spectra to solve the baseline drift problem in infrared spectra. An extended Gaussian peak is added to the infrared spectrum, a derivative term of the spectral and baseline differences is added during the iteration process, and the penalty coefficient is adaptively adjusted. The infrared spectral characteristic variables of ablation characteristic gases were screened by combining variable influence values ​​and cluster analysis. The variables were the spectral data obtained from the scan and the analyte concentration information contained therein. The spectral data were multiplied by a coefficient greater than 1 and less than 1, respectively. Partial least squares models were established for the new variables, and the corresponding root mean square error of cross-validation was obtained. The variable influence value is the difference of the root mean square error of cross-validation. Cluster analysis is reflected in the frequency of the occurrence of the optimal model in the variable space. In each iteration, variables with low influence values ​​and low frequency of occurrence in the optimal model are eliminated, thereby realizing the quantitative analysis of the concentration of each component of the ablation characteristic gas. The degree of cable buffer layer erosion is assessed based on the concentration of characteristic components in the sample gas. A threshold method or weighted method is used to determine the degree of erosion, categorizing it into five states: normal, internally damp, mild erosion, moderate erosion, and severe erosion. The specific methods are as follows: The threshold-based method for classifying and evaluating the state of cable buffer layers is as follows: When the volume percentage concentration of hydrogen in the sample gas being detected is greater than T A value of 0 indicates that the cable buffer layer is damp; when the sum of the volume percentage concentrations (SUM) of the three gases (ethane, ethylene, and acetylene) is less than 0. T At time 1, the buffer layer is normal. T 1~ T At 2 o'clock, the ablation was mild. T 2~ T At 3 o'clock, the ablation was moderate, higher than T At 3 o'clock, the ablation was severe; The weighted method-based approach for classifying and evaluating the condition of cable buffer layers is as follows: The volume percentage concentrations of the three gases detected, namely ethane, ethylene, and acetylene, were as follows: C i , i =1,2,3, with weights assigned respectively. W i ，i =1,2,3, introducing the ablation index F The formula for characterizing the cable buffer layer condition is as follows: When the ablation index is obtained F The value is less than F A value of 1 indicates that the cable buffer layer is normal; the value is within... F 1~ F At 2, it indicates that mild ablation has occurred inside the buffer layer; the value is in the range of F 2~ F A score of 3 indicates moderate ablation; higher than 3 indicates moderate ablation. F A score of 3 indicates severe ablation.

2. The method for analyzing the characteristic gases of high-voltage cable buffer layer ablation and assessing cable condition according to claim 1, characterized in that, Data from a preset gas database is compared with data from the gas database, and a concentration threshold is set. T 0 is taken as 5000 × 10 -6 , T 1. Take 500 × 10 -6 , T 2. Take 1000 × 10 -6 , T 3. Take 2000 × 10 -6 ; Weight W 1. Take 0.

3. W 2 take 0.5, W 3 is taken as 0.2; ablation index F 1. Take 100 × 10 -6 , F 2. Take 500 × 10 -6 , F 3. Take 1000 × 10 -6 .

3. The method for analyzing the characteristic gases of high-voltage cable buffer layer ablation and assessing cable condition according to claim 1, characterized in that, The on-site operation procedure includes the following steps: Step S1: Turn on the main power and the system initializes; Step S2: After stripping the outer sheath of the cable and drilling an air hole, install the air valve; Step S3: The sample gas is drawn into the gas analysis system, and the system performs gas concentration analysis and records various parameters; Step S4: The detection data is wirelessly transmitted to the ground cable monitoring room, compared with the gas database, and the status of the cable buffer layer is diagnosed in real time. Step S5: Seal and repair the air intake hole, and mark the drilling positions around the outer sheath.

4. A system for analyzing characteristic gases of high-voltage cable buffer layer erosion and classifying cable condition, based on the method for analyzing characteristic gases of high-voltage cable buffer layer erosion and classifying cable condition as described in claim 1, characterized in that... It includes a gas collection device, a gas analysis device, and a cable monitoring room; the gas collection device and the gas analysis device are integrated into one unit. The gas collection device collects the gas generated during the ablation process of the buffer layer, and the gas analysis device analyzes the gas composition and corresponding concentration to obtain the gas composition and corresponding concentration. The gas composition and corresponding concentration are transmitted to the cable monitoring room, and the cable monitoring room performs graded assessment of the degree of cable ablation based on the type and concentration of the ablation gas.

5. The high-voltage cable buffer layer ablation characteristic gas analysis and cable condition classification assessment system according to claim 4, characterized in that, The gas collection device includes a drilling module, an extraction module, a drying module, and a gas collection module. These four modules are connected in sequence and can collect gas from the cavity inside the aluminum sheath of the cable by drilling, extraction, and drying in sequence.

6. The high-voltage cable buffer layer ablation characteristic gas analysis and cable condition classification assessment system according to claim 4, characterized in that, The gas analysis device includes a Fourier transform infrared spectrometer, a hydrogen detection module, a main control module, a data acquisition module, and a data processing module; Fourier transform infrared spectrometer is used to collect infrared spectra of methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide, and carbon dioxide. The hydrogen detection module uses an electrochemical or metal oxide semiconductor sensor to detect hydrogen concentration; The main control module is used to set the parameters of the Fourier transform infrared spectrometer and the hydrogen detection module and to send control commands. The data acquisition module uses temperature, humidity, and air pressure sensors to collect temperature, humidity, and air pressure parameters in the gas. The data processing module is used to filter and denoise the collected infrared spectra, perform baseline correction, extract feature variables, and perform quantitative modeling analysis to obtain the corresponding gas concentrations and acquire the hydrogen concentration.

7. The high-voltage cable buffer layer ablation characteristic gas analysis and cable condition classification assessment system according to claim 6, characterized in that, The gas analysis device also includes a power supply module, an environmental monitoring module, a display module, an early warning module, and a wireless communication module; The power module is used for power supply; The environmental monitoring module includes lighting and a high-definition camera for real-time detection of the cable well site conditions; The display module is a touch screen used for human-computer interaction, receiving spectrometer parameter settings and spectral scanning operation commands, and displaying gas detection results; The early warning module is a voice alarm controller, which is used to flash the panel indicator light and display and broadcast alarm information when the detection result is abnormal; The wireless module, which can be a WiFi module, NB-IoT module, or LoRa module, is used to communicate with the cable compartment.

8. The high-voltage cable buffer layer ablation characteristic gas analysis and cable condition classification assessment system according to claim 6, characterized in that, The Fourier transform infrared spectrometer first requires initial parameter configuration, with the initial wavenumber set to 4000 cm⁻¹. -1 The termination wavenumber is set to 400cm. -1 Or 500cm -1 The resolution can be set to 1cm. -1 2cm -1 Or 4cm -1 The scanning frequency was set to 4 times. The gas chamber was evacuated to 0.04 MPa by a pressure sensor, or nitrogen or argon gas, which has no absorption peak in the infrared region, was injected into the gas chamber to obtain the background spectrum. Next, the sample gas was ablated by the buffer layer and its absorption spectrum was scanned. At the same time, environmental parameters of the gas, including temperature and pressure, were collected to obtain the compensation coefficient, which was used to compensate for the gas concentration detection value. Finally, the hydrogen concentration was combined and transmitted to the main control module.

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