High-voltage cable buffer layer ablation characteristic gas analysis and cable state grading evaluation method and system

Abstract

The invention 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, which can discover the ablation phenomenon of a cable as soon as possible and avoid potential power failure and potential safety hazards through rapid analysis of gas components. Accurate evaluation can be provided through the relation between the gas composition and concentration and the ablation degree, and making of targeted maintenance and replacement plans is helped. According to the invention, timely monitoring and evaluation can be realized, the accident risk caused by cable faults can be reduced, and the safety and reliability of a power system are enhanced. By discovering problems in advance, power failure and maintenance cost caused by sudden faults are reduced, and therefore the overall economic benefits are improved. The gas analysis data can provide a basis for long-term monitoring and management of the operation state of the cable, and a more scientific maintenance strategy is supported.

Description

Technical Field

[0001] The present invention belongs to the field of electrical insulation detection of power equipment, and in particular relates to a method and system for analyzing characteristic gas ablation of a high-voltage cable buffer layer and grading and evaluating cable status. Background Art

[0002] High-voltage cables are key equipment in the power transmission network of the power system, and their reliability is crucial to the safe and stable operation of the power grid. However, after years of operation, various types of cable failures frequently occur, of which cable failures caused by defects in the cable buffer layer account for more than 80% of the total. Therefore, it is of great significance to detect the status of the cable buffer layer. Among the cable buffer layer status detection methods, electrical parameter and X-ray detection have certain limitations. When the main insulation of the cable is not broken down, the weak partial discharge signal is difficult to effectively identify, and X-rays are seriously affected by the shooting angle and distance, and the test is complex and difficult to apply.

[0003] Existing research shows that the defects of the cable buffer layer are mainly corrosion and overheating. The buffer cotton and aluminum sheath will react chemically under conditions such as electrical stress, thermal stress and humidity to generate characteristic gases represented by hydrogen, ethane, ethylene and acetylene. The type and concentration of the gas are different under different conditions, so the state of the buffer layer can be judged by detecting the gas. However, the conventional gas chromatography gas detection method has the disadvantages of long detection cycle, complex operation, difficult maintenance, and difficulty in on-site detection. It is crucial to find a fast and safe detection method and a comprehensive gas analysis system. Summary of the invention

[0004] The purpose of the present 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 on-site detection, and to provide a method and system for analyzing the characteristic gas of ablation of a high-voltage cable buffer layer and grading and evaluating the cable status.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] The method for analyzing the characteristic gas of ablation of the high-voltage cable buffer layer and grading and evaluating the cable status 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 of the cable buffer layer inside the aluminum sheath;

[0008] The infrared spectrum of the ablated sample gas is collected and analyzed. After filtering and denoising, baseline correction, characteristic 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 using an electrochemical or metal oxide semiconductor sensor.

[0009] According to the concentration of characteristic components in the sample gas, a graded assessment is carried out, and the threshold method or weight method is used to obtain the degree of ablation of the cable buffer layer, which is divided into five states: normal, internal moisture, mild ablation, moderate ablation, and severe ablation.

[0010] The infrared spectrum of the ablated sample gas is collected and analyzed. After filtering and denoising, baseline correction, characteristic variable extraction and quantitative modeling analysis, the specific method for obtaining the concentrations of characteristic components of methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide and carbon dioxide in the sample gas is as follows:

[0011] Eliminate noise interference in infrared spectrum through Savitzky-Golay filter;

[0012] The improved adaptive extended Gaussian peak derivative reweighted least square 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 spectrum and baseline difference is added in an iterative process, and the penalty coefficient is adaptively adjusted;

[0014] The infrared spectrum characteristic variables of ablation characteristic gas are screened by combining variable influence value with cluster analysis. The variables are the spectral data obtained by scanning and the analyte concentration information contained therein. The spectral data are multiplied by a coefficient greater than 1 and less than 1 respectively. Partial least squares models are established for the new variables to obtain the corresponding cross-validation root mean square error. The variable influence value is the difference of the cross-validation root mean square error.

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

[0016] According to the concentration of characteristic components in the sample gas, the ablation degree of the cable buffer layer is obtained by using the threshold method or weight method. The specific method is divided into five states: normal, internal moisture, mild ablation, moderate ablation, and severe ablation.

[0017] The cable buffer layer status classification evaluation method based on the threshold method is as follows:

[0018] When the volume percentage concentration of hydrogen in the sample gas detected is greater than T 0 When the sum of the volume percentage concentrations of ethane, ethylene and acetylene detected is lower than T 1 The buffer layer is normal at T 1 ~T 2 When it is mild ablation, T 2 ~T3 When it is moderate ablation, it is higher than T 3 When it is severe ablation;

[0019] The cable buffer layer status grading assessment method based on the weight method is as follows:

[0020] The volume percentage concentrations of the three gases ethane, ethylene and acetylene detected are C i (i=1,2,3), the weights are assigned to W 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 ablation index F is less than F 1 When F 1 ~F 2 When F 2 ~F 3 It indicates that moderate ablation has occurred; above F 3 It means severe ablation has occurred;

[0023] Preset the data in the gas database, compare the data in the gas database, concentration threshold T 0 Take 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 Take 0.2; ablation index F 1 Take 100×10 -6 、F 2 Take 500×10 -6 、F 3 Take 1000×10 -6 .

[0024] A high-voltage cable buffer layer ablation characteristic gas analysis and cable status grading assessment system includes a gas collection device, a gas analysis device and a cable monitoring room; the gas collection device is integrated with the gas analysis device, 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, and the cable monitoring room grades and assesses the degree of cable ablation according to the type and concentration of the ablation gas.

[0025] The gas collection device includes a punching module, a vacuum module, a drying module, and a gas collection module. The four modules are tightly connected in sequence, and the gas in the cavity of the cable aluminum sheath can be collected by punching, vacuuming, 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, used to collect infrared spectra of methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide and carbon dioxide;

[0028] The hydrogen detection module uses electrochemical or metal oxide semiconductor sensors 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 send control instructions;

[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 spectrum, perform baseline correction, extract characteristic variables, and conduct quantitative modeling analysis to obtain the corresponding gas concentration and hydrogen concentration.

[0032] The gas analysis device also includes a power 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] Environmental monitoring module, including lighting and high-definition cameras, for real-time detection of cable well site conditions;

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

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

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

[0038] The Fourier transform infrared spectrometer first needs to be initialized and the starting wave number is set to 4000cm -1 , the end wave number is set to 400cm -1 or 500cm -1, the resolution can be set to 1cm -1 , 2cm -1 or 4cm -1 The number of scans is set to 4. The air pressure sensor monitors the air chamber to be evacuated to 0.04MPa, or nitrogen or argon with no absorption peak in the infrared region is injected into the air chamber, and the background spectrum is obtained by scanning. Secondly, the buffer layer is ablated and the sample gas is introduced to scan its absorption spectrum. At the same time, the environmental parameters of the gas including temperature and pressure are collected to obtain the compensation coefficient, which is used to compensate for the gas concentration detection value. Finally, it is transmitted to the main control module together with the hydrogen concentration.

[0039] Analysis of characteristic gases of ablation of high-voltage cable buffer layer and classification assessment of cable status. The on-site operation process includes the following steps:

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

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

[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: wirelessly transmit the detection data to the ground cable monitoring room, compare it with the gas database, and diagnose the cable buffer layer status in real time;

[0044] Step S5: seal and repair the air extraction holes, and mark the drilling positions around the outer sheath.

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

[0046] The present invention can detect the ablation of the cable early through rapid analysis of the gas composition, thereby avoiding potential power failures and safety hazards. The present invention can provide an accurate assessment through the relationship between the gas composition and concentration and the degree of ablation, and help formulate targeted maintenance and replacement plans. The present invention 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. The present invention reduces power outages and maintenance costs caused by sudden failures by discovering problems in advance, thereby improving the overall economic benefits. The gas analysis data of the present invention can provide a basis for long-term monitoring and management of the cable operating status and support more scientific maintenance strategies. The present invention can provide feedback for the improvement of cable materials and structures, and promote the research and development of higher performance cables. In summary, the present invention can preliminarily judge the state of the cable buffer layer, facilitate subsequent maintenance and overhaul, and is of great significance to the safe and reliable operation of the cable power system. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0048] Figure 2 It is a work flow chart of the present invention;

[0049] Figure 3 It is a flow chart of the on-site operation of the present invention;

[0050] Figure 4 It is a flow chart of the method for grading and evaluating the state of the buffer layer of a medium- and high-voltage cable according to the present invention. DETAILED DESCRIPTION

[0051] In order to further understand the content of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the embodiments are only for explaining the present invention and are not intended to limit it.

[0052] Embodiment 1:

[0053] The method for analyzing the characteristic gas of ablation of the high-voltage cable buffer layer and grading and evaluating the cable status includes the following steps:

[0054] S1, drilling 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 ablated sample gas. After filtering and denoising, baseline correction, characteristic 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 using an electrochemical or metal oxide semiconductor sensor.

[0056] S3, based on the concentration of characteristic components in the sample gas, a graded assessment is performed, and the degree of ablation of the cable buffer layer is obtained using the threshold method or the weight method, which is divided into five states: normal, internal moisture, mild ablation, moderate ablation, and severe ablation.

[0057] Embodiment 2:

[0058] High-voltage cable buffer layer ablation characteristic gas analysis and cable status grading assessment system, including:

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

[0060] The gas analysis device is integrated with the gas collection device and is used to analyze the collected gas to obtain the gas composition and corresponding concentration;

[0061] The cable monitoring room is used to conduct graded assessment based on the composition of the gas and its corresponding concentration to obtain the degree of cable ablation.

[0062] Embodiment 3:

[0063] The infrared spectrum of the ablated sample gas is collected and analyzed. After filtering and denoising, baseline correction, characteristic variable extraction and quantitative modeling analysis, the specific method for obtaining the concentrations of characteristic components of methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide and carbon dioxide in the sample gas is as follows:

[0064] Eliminate noise interference in infrared spectrum through Savitzky-Golay filter;

[0065] The improved adaptive extended Gaussian peak derivative reweighted least square 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 spectrum and baseline difference is added in an iterative process, and the penalty coefficient is adaptively adjusted;

[0067] The infrared spectrum characteristic variables of ablation characteristic gas are screened by combining variable influence value with cluster analysis. The variables are the spectral data obtained by scanning and the analyte concentration information contained therein. The spectral data are multiplied by a coefficient greater than 1 and less than 1 respectively. Partial least squares models are established for the new variables to obtain the corresponding cross-validation root mean square error. The variable influence value is the difference of the cross-validation root mean square error.

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

[0069] Embodiment 4:

[0070] The cable buffer layer status classification evaluation method based on the threshold method is as follows:

[0071] When the volume percentage concentration of hydrogen in the sample gas detected is greater than T 0 When the sum of the volume percentage concentrations of ethane, ethylene and acetylene detected is lower than T 1 The buffer layer is normal at T 1 ~T 2 When it is mild ablation, T 2 ~T 3 When it is moderate ablation, it is higher than T 3 When it is severe ablation;

[0072] The cable buffer layer status grading assessment method based on the weight method is as follows:

[0073] The volume percentage concentrations of the three gases ethane, ethylene and acetylene detected are C i(i=1,2,3), the weights are assigned to W 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 ablation index F is less than F 1 When F 1 ~F 2 When F 2 ~F 3 It indicates that moderate ablation has occurred; above F 3 This indicates severe ablation.

[0076] Preset the data in the gas database, compare the data in the gas database, concentration threshold T 0 Take 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 Take 0.2; ablation index F 1 Take 100×10 -6 、F 2 Take 500×10 -6 、F 3 Take 1000×10 -6 .

[0077] Embodiment 5:

[0078] See also Figure 1 , a high-voltage cable buffer layer ablation characteristic gas analysis and cable status grading evaluation system, including a gas collection device, a gas analysis device and a cable monitoring room.

[0079] The gas collection device is integrated with the gas analysis device, with an overall size of 50cm*40cm*30cm. It is equipped with four universal wheels at the bottom and handles 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 composition and corresponding concentration are analyzed by the gas analysis device. The relevant data are transmitted to the cable monitoring room, and the degree of cable ablation is judged by graded evaluation based on the type and concentration of the ablation gas. The core of the gas analysis device is a gas concentration analysis unit, including a Fourier transform infrared spectrometer and a hydrogen detection module. The Fourier transform infrared spectrometer can obtain infrared spectra of methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide, and carbon dioxide. The concentration of each component gas can be obtained through filtering and denoising, baseline correction, characteristic variable extraction, and quantitative model establishment. The hydrogen detection module is an electrochemical sensor, which can detect the hydrogen concentration.

[0080] The gas collection device includes a drilling module, a vacuum module, a drying module, and a gas collection module. The four modules are tightly connected in sequence. The drilling module is a limited hand drill. The exposed drill bit length is adjustable within the adjustment range of 3mm to 6mm, which can ensure that the aluminum sheath of the cable with the outer sheath stripped off is penetrated without damaging the buffer layer structure. The vacuum module adopts a small air pump with a vacuum flow rate of 1000ml / min, which can extract the gas in the aluminum sheath cavity. The drying module is a drying tube filled with color-changing silica gel and molecular sieves, which can filter and remove moisture in the gas and aluminum sheath debris left over from drilling to reduce interference. The gas collection module is an adjustable three-way Y-type valve, which can be passed into an air bag for retention, or passed into a gas analysis device for detection.

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

[0082] The gas analysis device includes a data acquisition module and a data processing module. The data acquisition module is a temperature, humidity, and air pressure sensor, which can collect temperature, humidity, and air pressure in the gas. The temperature detection range is -40°C to +80°C, with an accuracy of ±0.5°C, the humidity detection range is 0 to 100%RH, with an accuracy of 3%RH, and the air pressure detection range is 30 to 125kPa, with an accuracy of ±8Pa. The data processing module is an ARM Cortex-M3 core series STM32 microcontroller, which can collect and process gas parameters. The specific process is: communicate with the sensor through the microcontroller, the microcontroller sends a fixed request frame to the sensor, receives a response frame, and obtains the real temperature, humidity, and air pressure data according to the data frame format. The data can be used as a cable operation status parameter, and can also be corrected for subsequent gas concentration analysis.

[0083] The core of the gas analysis device is the embedded industrial control all-in-one computer, which communicates with the data processing module and the gas concentration analysis unit module. It is the control center of the entire system and controls the system's spectrometer, single-chip microcomputer, solenoid valve and air pump. It can process and analyze the spectral data and temperature, humidity and air pressure data of the gas and receive the user's spectrometer parameter settings, spectral scanning, and sensor detection operation instructions.

[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 can power the entire system; the environmental monitoring module is a lighting lamp and a high-definition camera that can be used to detect the on-site conditions of the cable well in real time; the display module is a touch screen that can perform human-computer interaction, receive the user's spectrometer parameter settings, scan spectrum operations, and display gas detection results; the early warning module is a language alarm controller, and when the detection result is abnormal, the panel indicator light flashes, and the alarm information is displayed and broadcast; the wireless module is an HC-14 wireless module, which is 433MHz transparent transmission, can achieve 3 kilometers long-distance transmission, and can perform wireless data communication with the cable monitoring room outside the wellhead.

[0085] The process of the gas concentration analysis method is as follows: first, the Savitzky-Golay filter is used to eliminate the noise interference in the original spectrum; then, the improved adaptive extended Gaussian peak derivative reweighted least squares method is used to solve the baseline drift problem in the spectrum. This method adds the extended Gaussian peak to the spectrum, adds the derivative term of the spectrum and baseline difference in the iterative process, and adaptively adjusts the penalty coefficient; finally, the infrared spectrum characteristic variables of the ablation characteristic gas are screened by combining the variable influence value with cluster analysis. The variables are the spectral data obtained by scanning and the analyte concentration information contained therein, and the spectral data are multiplied by a value greater than 1 and a value less than 1 respectively. The coefficient of 1 is used to establish partial least squares models for the new variables, and the corresponding interactive validation root mean square error is obtained. The variable influence value is the difference of the interactive validation root mean square error. 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 variable influence value, the weighted bootstrap sampling technology is used to divide the variables into elite variables and ordinary variables, and the variables with low frequency are eliminated from the ordinary variables. This ensures that the variables with low variable influence value and low frequency in the optimal model are eliminated in each iteration, thereby realizing the quantitative analysis of the concentration of each component of the ablation characteristic gas.

[0086] Gas analysis system workflow Figure 2 As shown in the figure, the Fourier transform spectrometer needs to be initialized and the starting wave number is set to 4000cm -1 , the end wave number is set to 400cm -1 or 500cm -1 , the resolution can be set to 1cm -1 , 2cm -1 or 4cm -1 The number of scans is set to 4, and the air pressure sensor monitors the vacuum of the air chamber to the set value P 1 , or the gas chamber is injected with nitrogen or argon that has no absorption peak in the infrared region, and the background spectrum is obtained by scanning; then the temperature, humidity and air pressure in the environment are collected, and the background spectrum and environmental parameters are saved; when the cable air hole is installed, the buffer layer ablation sample gas is introduced until the air pressure reaches the set value P 2 , scan the gas spectrum, collect gas parameters at the same time, obtain the compensation coefficient to compensate the gas concentration detection value; finally, transmit it to the industrial computer together with the hydrogen concentration and transmit the data wirelessly to the cable monitoring room.

[0087] The compensation coefficient is determined by the temperature T and pressure P of the gas. The compensated absorbance A 1 Determined by formula (1)

[0088]

[0089] In the formula, A 1is the absorbance after compensation, A 0 is the absorbance before compensation, T is the gas temperature in °C, and P is the gas pressure in kPa.

[0090] Embodiment 6:

[0091] See also Figure 3 , a method for analyzing the characteristic gas of ablation of a high-voltage cable buffer layer and grading and evaluating the cable status, comprising the following steps:

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

[0093] Step S2: stripping off the outer sheath of the cable, drilling an air hole with a limited hand drill, and then installing an adjustable air extraction 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 compare with the gas database to diagnose the cable buffer layer status in real time;

[0096] Step S5: seal and repair the air extraction hole, wrap tape around the outer sheath and mark the punching point.

[0097] The flow chart of the high voltage cable buffer layer status classification assessment method is as follows Figure 4 As shown, firstly, hydrogen, ethane, ethylene and acetylene are extracted from the sample gas of the buffer layer as characteristic gases, and the buffer layer state is graded and diagnosed using the threshold method or the weight method, which is divided into five states: internal moisture, normal, mild ablation, moderate ablation and severe ablation;

[0098] The cable buffer layer status classification evaluation method based on the threshold method is as follows:

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

[0100] When the sum of the volume percentage concentrations of ethane, ethylene and acetylene is 500×10 -6 ~1000×10 -6 , indicating that slight ablation occurred inside the buffer layer, less than 50×10 -6 Normal, higher than 1000×10 -6 But less than 2000×10 -6 This indicates moderate ablation, which is higher than 2000×10 -6 It means severe ablation has occurred;

[0101] The cable buffer layer status grading assessment method based on the weight method is as follows:

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

[0103] The calculation formula of ablation index F is:

[0104]

[0105] When the ablation index F is less than 100×10 -6 When the cable buffer layer is normal, the value is 100×10 -6 ~500×10 -6 When , it indicates that slight ablation occurs inside the buffer layer; when the value is 500×10 -6 ~1000×10 -6 This indicates moderate ablation, which is higher than 1000×10 -6 This indicates severe ablation.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does 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. Analysis of characteristic gas for ablation of high-voltage cable buffer layer and classification and evaluation method for cable status, characterized in that: The following steps are involved: Drill holes in the aluminum sheath of the high-voltage cable to extract and collect the gas generated during the ablation of the cable buffer layer inside the aluminum sheath; The infrared spectrum of the ablated sample gas is collected and analyzed. After filtering and denoising, baseline correction, characteristic 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 using an electrochemical or metal oxide semiconductor sensor. According to the concentration of characteristic components in the sample gas, a graded assessment is carried out, and the threshold method or weight method is used to obtain the degree of ablation of the cable buffer layer, which is divided into five states: normal, internal moisture, mild ablation, moderate ablation, and severe ablation.

2. The method for analyzing characteristic gas of high-voltage cable buffer layer ablation and evaluating cable status by graded method according to claim 1 is characterized in that: The infrared spectrum of the ablated sample gas is collected and analyzed. After filtering and denoising, baseline correction, characteristic variable extraction and quantitative modeling analysis, the specific method for obtaining the concentrations of characteristic components of methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide and carbon dioxide in the sample gas is as follows: Eliminate noise interference in infrared spectrum through Savitzky-Golay filter; The improved adaptive extended Gaussian peak derivative reweighted least square 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 spectrum and baseline difference is added in an iterative process, and the penalty coefficient is adaptively adjusted; The infrared spectrum characteristic variables of ablation characteristic gas are screened by combining variable influence value with cluster analysis. The variables are the spectral data obtained by scanning and the analyte concentration information contained therein. The spectral data are multiplied by a coefficient greater than 1 and less than 1 respectively. Partial least squares models are established for the new variables to obtain the corresponding cross-validation root mean square error. The variable influence value is the difference of the cross-validation root mean square error. Cluster analysis is reflected in the frequency of occurrence of the optimal model in the variable space. In each iteration, variables with low variable influence values ​​and low frequency of occurrence in the optimal model are eliminated, thereby achieving quantitative analysis of the concentrations of each component of the ablation characteristic gas.

3. The method for analyzing characteristic gas of high-voltage cable buffer layer ablation and evaluating cable status by graded evaluation according to claim 1 is characterized in that: According to the concentration of characteristic components in the sample gas, the ablation degree of the cable buffer layer is obtained by using the threshold method or weight method. The specific method is divided into five states: normal, internal moisture, mild ablation, moderate ablation, and severe ablation. The cable buffer layer status classification evaluation method based on the threshold method is as follows: When the volume percentage concentration of hydrogen in the sample gas detected 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 detected is lower than T1, the buffer layer is normal, and it is slightly ablated when it is between T1 and T2, moderately ablated when it is between T2 and T3, and severely ablated when it is higher than T3; The cable buffer layer status grading assessment method based on the weight method is as follows: The volume percentage concentrations of the three gases ethane, ethylene and acetylene detected are C i (i=1,2,3), the weights are assigned to W 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: 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 slight ablation has occurred inside the buffer layer; when the value is between F2 and F3, it indicates that moderate ablation has occurred; and when it is higher than F3, it indicates that severe ablation has occurred.

4. The method for analyzing characteristic gas of ablation of high-voltage cable buffer layer and evaluating cable status by graded method according to claim 3 is characterized in that: The data in the preset gas database are compared with the data in the gas database. The concentration threshold T0 is 5000×10 -6 、T1 takes 500×10 -6 , T2 takes 1000×10 -6 、T3 takes 2000×10 -6 ; Weight W1 is 0.3, W2 is 0.5, W3 is 0.2; Ablation index F1 is 100×10 -6 、F2 takes 500×10 -6 、F3 takes 1000×10 -6 .

5. High-voltage cable buffer layer ablation characteristic gas analysis and cable status classification evaluation system, characterized by: 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, 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 the corresponding concentration to obtain the gas composition and the corresponding concentration. The gas composition and the corresponding concentration are transmitted to the cable monitoring room, and the cable monitoring room evaluates the degree of cable ablation according to the type and concentration of the ablation gas.

6. The high-voltage cable buffer layer ablation characteristic gas analysis and cable status grading evaluation system according to claim 5 is characterized in that: The gas collection device includes a punching module, a vacuum module, a drying module, and a gas collection module. The four modules are tightly connected in sequence, and the gas in the cavity of the cable aluminum sheath can be collected by punching, vacuuming, and drying in sequence.

7. The high-voltage cable buffer layer ablation characteristic gas analysis and cable status classification evaluation system according to claim 5 is 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, used to collect infrared spectra of methane, ethane, propane, ethylene, propylene, acetylene, propyne, carbon monoxide and carbon dioxide; The hydrogen detection module uses electrochemical or metal oxide semiconductor sensors 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 send control instructions; 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 spectrum, perform baseline correction, extract characteristic variables, and conduct quantitative modeling analysis to obtain the corresponding gas concentration and hydrogen concentration.

8. The high-voltage cable buffer layer ablation characteristic gas analysis and cable status classification evaluation system according to claim 5 is characterized in that: The gas analysis device also includes a power 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; Environmental monitoring module, including lighting and high-definition cameras, for real-time detection of cable well site conditions; The display module is a touch screen used for human-computer interaction, receiving spectrometer parameter settings, scanning spectrum operation instructions, and displaying gas detection results; The early warning module is a voice alarm controller, which is used to flash the panel indicator light, display and broadcast the alarm information when the detection result is abnormal; The wireless module is a WiFi module, NB-IoT module or LoRa module, which is used to communicate with the cable room.

9. The high-voltage cable buffer layer ablation characteristic gas analysis and cable status classification evaluation system according to claim 7 is characterized in that: The Fourier transform infrared spectrometer first needs to be initialized and the starting wave number is set to 4000cm -1 , the end wave number is set to 400cm -1 or 500cm -1 , the resolution can be set to 1cm -1 , 2cm -1 or 4cm -1 The number of scans is set to 4. The air pressure sensor monitors the air chamber to be evacuated to 0.04MPa, or nitrogen or argon with no absorption peak in the infrared region is injected into the air chamber, and the background spectrum is obtained by scanning. Secondly, the buffer layer is ablated and the sample gas is introduced to scan its absorption spectrum. At the same time, the environmental parameters of the gas including temperature and pressure are collected to obtain the compensation coefficient, which is used to compensate for the gas concentration detection value. Finally, it is transmitted to the main control module together with the hydrogen concentration.

10. High-voltage cable buffer layer ablation characteristic gas analysis and cable status classification evaluation method, characterized in that: The on-site operation process includes the following steps: Step S1: Turn on the main power and initialize the system; Step S2: After stripping the outer sheath of the cable and drilling the air hole, the air extraction valve is installed; 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: wirelessly transmit the detection data to the ground cable monitoring room, compare it with the gas database, and diagnose the cable buffer layer status in real time; Step S5: seal and repair the air extraction holes, and mark the drilling positions around the outer sheath.

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