A gas detection device and method for high-voltage cable joints

Abstract

This invention discloses a gas detection device and method for high-voltage cable joints. It includes a photoacoustic cell, a detection module, a light source, an FPGA core control and demodulation system, and a display and analysis module. The photoacoustic cell stores the gas escaping from the high-voltage cable joint. The light source emits a light beam with a characteristic wavelength to illuminate the gas stored in the photoacoustic cell. The detection module receives the emitted gas to generate a photoacoustic signal and determines the type and concentration of the gas based on the signal. The FPGA core control and demodulation system processes the gas type and concentration information to obtain a demodulated digital signal. The display and analysis module analyzes the demodulated digital signal to determine whether the high-voltage cable joint has defects and the type of defect. This invention features high sensitivity, high reliability, and a high defect detection rate.

Description

Technical Field

[0001] This invention belongs to the field of optical inspection technology for high-voltage cable joints, specifically relating to a gas detection device and method for high-voltage cable joints. Background Technology

[0002] 110kV and above high-voltage transmission cables serve as the incoming and outgoing lines of major substations in urban areas and important power supply connections between key users and substations. Their safe operation is a crucial guarantee for the reliable power supply of the power grid. In recent years, the number and scope of cables used in new construction projects have expanded rapidly. However, the understanding of high-voltage cable applications among design, operation, and management personnel remains insufficient. Practices such as rushing cable laying and installing cable joints without proper certification are widespread, leading to frequent cable faults. High-voltage cable joints, in particular, have become a high-risk area for faults, seriously affecting the safe and reliable operation of the power grid, causing significant economic losses and severe social impact. Therefore, the condition of high-voltage cable joints directly determines whether the high-voltage cable system can operate safely and stably.

[0003] Currently, high-voltage cable joints are installed on-site by construction personnel or manufacturers. However, the high environmental cleanliness requirements, complex internal structure, and difficulty in controlling key processes of cable joint insulation prefabrication make it easy for potential insulation defects to occur during installation, such as impurities, dimensional deviations, and substandard insulation shielding. These defects are difficult to detect and highly concealed, typically requiring 1-5 years of gradual development within the insulation prefabrication before detectable partial discharges or abnormal heating appear. Furthermore, during operation, joints are often laid in underground passages such as tunnels, ducts, and cable trenches, leading to frequent problems like moisture and water ingress. Due to the large insulation design margin of cable joints and the limited number of effective detection methods, potential defects generated during installation are often difficult to detect through power outage tests such as insulation resistance and AC withstand voltage. Existing live-line detection technologies for high-voltage cable joints, such as partial discharge detection, sheath circulation monitoring, and infrared thermography, are not sensitive enough to detect common problems like water ingress and early insulation defects, exhibiting limitations such as low defect detection rates and susceptibility to electromagnetic interference. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the above-mentioned background technology and provide a gas detection device and method for high-voltage cable joints.

[0005] The technical solution adopted in this invention is: a gas detection device for high-voltage cable joints, comprising a photoacoustic cell, a detection module, a light source, an FPGA core control and demodulation system, and a display and analysis module.

[0006] The photoacoustic cell is used to store the gas escaping from the high-voltage cable joint. The light source is used to emit a light beam with a characteristic wavelength and illuminate the gas escaping from the high-voltage cable joint stored in the photoacoustic cell. The detection module is used to receive the gas escaping and generate a photoacoustic signal. Based on the photoacoustic signal, the type and concentration information of the escaping gas are determined. The FPGA core control and demodulation system is used to process the type and concentration information of the escaping gas to obtain the demodulated digital signal. The display and analysis module is used to analyze the demodulated digital signal to determine whether there are defects in the high-voltage cable joint and the type of defects.

[0007] It also includes a detection interface, a solenoid valve, and an air pump. The detection interface is used to connect to the detection hole of the protective copper shell of the high-voltage cable connector. The air pump is connected to the detection interface to pump the gas escaping from inside the protective copper shell into the photoacoustic cell. The solenoid valve is connected between the detection interface and the air pump to control the flow direction and on / off of the escaping gas. The FPGA core control and demodulation system is used to control the opening and closing of the light source, the opening degree of the solenoid valve, and the opening and closing of the air pump.

[0008] It also includes an AD conversion module, which is connected between the detection module and the FPGA core control and demodulation system to process the type and concentration information of the escaped gas to obtain a digital signal.

[0009] The display analysis module compares the concentration of each type of gas escaping from the high-voltage cable joint with the corresponding gas threshold. If the concentration of that type of gas is greater than or equal to the gas threshold, it determines that there is a defect in the high-voltage cable joint.

[0010] The types of gases that escape include CO2, CO, CH4, C2H2, C2H4, C2H6, and H2O.

[0011] Calculate the gas ratios between various gas types based on the concentration of each gas type in the escaping gas: R1 = CO concentration / CO2 concentration, R2 = C2H2 concentration / C2H4 concentration, R3 = C2H2 concentration / CH4 concentration, R4 = C2H6 concentration / C2H2 concentration, and R5 = CO2 concentration / H2O concentration. Determine the defect type of the high-voltage cable joint based on the range of gas ratios between various gas types. R1 to R5 are the first gas ratio, the second gas ratio, the third gas ratio, the fourth gas ratio, and the fifth gas ratio, respectively.

[0012] The defect types include overheating, partial discharge, arcing failure, and moisture.

[0013] If R1 > K 1high If R2 < K2, R3 < K3, and R4 > K4, then it is determined to be an overheating defect;

[0014] If R1 < K 1lowIf R3 < K3 and R4 > K4, then it is determined to be a partial discharge defect;

[0015] If K 1low ≤R1≤K 1high K 2low ≤R2≤K 2high If R3≥K3 and R4<K4, then it is judged to be an arc fault defect;

[0016] If K 1low ≤R1≤K 1high If R4≥K4 and R5≤K5, it is judged as a moisture defect;

[0017] Among them, K 1low K is the first set lower limit of the range. 1high Set the upper limit of the range for the first; K 2low K is the second set lower limit of the range. 2high K1 is the upper limit of the second set range; K2 is the second set value; K3 is the third set value; K4 is the fourth set value; K5 is the fifth set value.

[0018] A method for detecting gas escaping from a high-voltage cable joint, including

[0019] The light source emits a beam of light with a characteristic wavelength and irradiates the gas escaping from the high-voltage cable joint stored in the photoacoustic pool. The emitted gas is excited to generate a photoacoustic signal. The type and concentration information of the emitted gas are determined based on the photoacoustic signal. The type and concentration information of the emitted gas are processed to obtain a demodulated digital signal. The demodulated digital signal is analyzed to determine whether there are defects in the high-voltage cable joint and the type of defect.

[0020] The concentration of each type of gas escaping from the high-voltage cable joint is compared with the corresponding gas threshold. If the concentration of that type of gas is greater than or equal to the gas threshold, the high-voltage cable joint is determined to be defective.

[0021] The types of gases that escape include CO2, CO, CH4, C2H2, C2H4, C2H6, and H2O.

[0022] Calculate the gas ratios between various gas types based on the concentration of each gas type in the escaping gas: R1 = CO concentration / CO2 concentration, R2 = C2H2 concentration / C2H4 concentration, R3 = C2H2 concentration / CH4 concentration, R4 = C2H6 concentration / C2H2 concentration, and R5 = CO2 concentration / H2O concentration. Determine the defect type of the high-voltage cable joint based on the range of gas ratios between various gas types. R1 to R5 are the first gas ratio, the second gas ratio, the third gas ratio, the fourth gas ratio, and the fifth gas ratio, respectively.

[0023] The defect types include overheating, partial discharge, arcing failure, and moisture.

[0024] If R1 > K 1high If R2 < K2, R3 < K3, and R4 > K4, then it is judged as an overheating defect; if R1 < K... 1low If R3 < K3 and R4 > K4, then it is judged to be a partial discharge defect; if K 1low ≤R1≤K 1high K 2low ≤R2≤K 2high If R3≥K3 and R4<K4, then it is judged as an arc fault defect; if K 1low ≤R1≤K 1high If R4 ≥ K4 and R5 ≤ K5, then it is judged as a moisture defect, where K 1low K is the first set lower limit of the range. 1high Set the upper limit of the range for the first; K 2low K is the second set lower limit of the range. 2high K1 is the upper limit of the second set range; K2 is the second set value; K3 is the third set value; K4 is the fourth set value; K5 is the fifth set value.

[0025] The mechanism of gas generation in the high-voltage cable joint of this invention is as follows: When the high-voltage cable joint has partial discharge defects, overheating defects, and the material inside the joint is damp or aged, the cable and the various components of the joint will undergo pyrolysis reactions and release gaseous products. XLPE is a macromolecular polymer composed of carbon chains of different lengths. The carbon chains will break to different degrees at different temperatures, eventually generating various small-molecule hydrocarbons. Its pyrolysis reaction equation can be expressed as equation (1):

[0026]

[0027] When the pyrolysis zone contains a certain amount of oxygen (such as a small amount of oxygen molecules adsorbed in the amorphous region of the polymer, oxygen and water molecules in the porous structure of the water-blocking buffer layer), CO and CO2 will also be generated, and their output mainly depends on the amount of oxygen. Therefore, when there are defects in the cable joint, gases such as acetylene, ethane, methane, ethylene, carbon monoxide, carbon dioxide, and water will escape.

[0028] The gas detection principle of this invention is as follows: Escaped gas is stored in a sealed photoacoustic cell. When a beam of light in a specific infrared band irradiates the escaped gas molecules, the molecules selectively absorb light energy in a portion of the band. After absorbing the incident light, the escaped gas molecules in the photoacoustic cell are excited from a low-energy state to a high-energy state, and then return to the low-energy state through spontaneous emission and non-radiative transitions. During the non-radiative transition, the energy is converted into translational and rotational kinetic energy, causing the temperature of the escaped gas to rise. With a constant volume of escaped gas, the increased temperature leads to increased pressure. If the intensity or wavelength of the incident light is modulated, the temperature of the escaped gas will change at the same frequency, resulting in periodic changes in the gas pressure. If the modulation frequency is within the acoustic frequency range, the periodic changes in gas pressure will generate a photoacoustic signal. Detecting this signal through the detection module allows us to obtain information about the type and concentration of the escaped gas.

[0029] This invention enables distributed sensing and alarming of partial discharge defects, overheating defects, and material aging within high-voltage cable joints. It also enables detection of gases escaping from high-voltage cable joints with low cross-sensitivity, high sensitivity, high resolution, and resistance to electromagnetic interference, thereby improving the safe operation level of cable lines.

[0030] Implementing this invention has the following beneficial effects: The gas detection device escaping from high-voltage cable joints features high sensitivity, high reliability, and a high defect detection rate. It identifies the insulation status and defect types of cable joints, significantly improving the lean management level of cable lines and reducing the occurrence of cable joint failures. It greatly enhances the monitoring and early warning capabilities of high-voltage cable line joint conditions, improving the safe operation level of equipment. Attached Figure Description

[0031] Figure 1 This is a flowchart of the detection method;

[0032] Figure 2 This is a structural block diagram of the gas detection device escaping from the high-voltage cable joint of the present invention;

[0033] Figure 3 This is a schematic diagram of the photoacoustic sensor structure of the TU-shaped microcantilever beam structure of the present invention;

[0034] Figure 4 Another embodiment of a gas detection device escaping from a high-voltage cable joint is shown in the structural block diagram.

[0035] Figure 5 A schematic diagram of the structure for protecting the copper shell. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but these descriptions do not constitute a limitation on the present invention.

[0037] Example 1:

[0038] like Figure 2 As shown, this invention provides a gas detection device for high-voltage cable joints, comprising a photoacoustic cell 4, a detection module 5, a light source 7, an FPGA core control and demodulation system 8, and a display and analysis module 10.

[0039] In the above technical solution, the photoacoustic cell 4 is used to store the gas escaping from the high-voltage cable joint A, the light source 7 is used to emit a light beam with a characteristic wavelength and irradiate the gas escaping from the high-voltage cable joint A stored in the photoacoustic cell 4, the detection module 5 is used to receive the gas escaping to generate a photoacoustic signal, and determine the type and concentration information of the escaping gas based on the photoacoustic signal, the FPGA core control and demodulation system 8 is used to process the type and concentration information of the escaping gas to obtain a demodulated digital signal, and the display and analysis module 10 is used to analyze the demodulated digital signal to determine whether there is a defect in the high-voltage cable joint A and the type of defect.

[0040] The above technical solution also includes a detection interface 1, a solenoid valve 2, an air pump 3, an AD conversion module 6, a communication module 9, and a power supply 11. The detection interface 1 is used to connect to the detection hole C of the protective copper shell B of the high-voltage cable connector A. The air pump 3 is connected to the detection interface 1 to pump the gas escaping from inside the protective copper shell B into the photoacoustic cell 4. The solenoid valve 2 is connected between the detection interface 1 and the air pump 3 to control the flow direction and on / off of the escaping gas. The AD conversion module 6 is used to process the type and concentration information of the escaping gas to obtain a digital signal. The FPGA core control and demodulation system 8 is used to control the opening and closing of the light source 7, the opening degree of the solenoid valve 2, and the opening and closing of the air pump 3.

[0041] In the above technical solution, the detection interface 1 is connected to the photoacoustic pool 4, the detection module 5 is located inside the photoacoustic pool 4, the light source 7 is located outside the photoacoustic pool 4 and connected to the FPGA core control and demodulation system 8, and the detection module 5, D conversion module 6, light source 7, FPGA core control and demodulation system 8, communication module 9 and display analysis module 10 are connected in sequence.

[0042] In the above technical solution, the solenoid valve 2 is located between the detection interface 1 and the photoacoustic cell 4 and is connected to the FPGA core control and demodulation system 8 to control the flow direction and switching of the escaping gas.

[0043] In the above technical solution, the air pump 3 is located between the detection interface 1 and the photoacoustic cell 4 and is connected to the FPGA core control and demodulation system 8. It is used to pump the gas escaping from the inside of the protective copper shell B into or out of the photoacoustic cell 4.

[0044] In the above technical solution, the photoacoustic cell 4 is used to store the gas to be tested that has escaped.

[0045] In the above technical solution, the detection module 5 is used to detect photoacoustic signals and determine the type and concentration of the escaped gas.

[0046] In the above technical solution, the AD conversion module 6 is used to convert analog signals into digital signals.

[0047] In the above technical solution, the light source 7 is used to provide light of the wavelength used to detect the escaping gas in the photoacoustic cell 4.

[0048] In the above technical solution, the FPGA core control and demodulation system 8 is used to control the working status and sequence of the light source 7, solenoid valve 2, air pump 3, AD conversion module 6 and communication module 9 and demodulate the digital signal.

[0049] In the above technical solution, the communication module 9 is used to transmit the demodulated digital signal to the display and analysis module 10.

[0050] In the above technical solution, the display analysis module 10 is used to determine whether there is a defect in the high-voltage cable joint A by comparing the type and concentration of the escaping gas with the gas threshold. If there is a defect, the defect type of the high-voltage cable joint A is determined and displayed based on the gas ratio.

[0051] In the above technical solution, the power supply 11 is connected to the FPGA core control and demodulation system 8 and the display analysis module 10 respectively, and is used to supply power to the FPGA core control and demodulation system 9 and the display analysis module 10.

[0052] The display analysis module 10 compares the concentration of each type of gas escaping from the high-voltage cable joint A with the corresponding gas threshold. If the concentration of that type of gas is greater than or equal to the gas threshold, it determines that the high-voltage cable joint A has a defect.

[0053] The types of gases that escape include CO2, CO, CH4, C2H2, C2H4, C2H6, and H2O.

[0054] Calculate the gas ratios between various gas types based on the concentration of each gas type in the escaping gas: R1 = CO concentration / CO2 concentration, R2 = C2H2 concentration / C2H4 concentration, R3 = C2H2 concentration / CH4 concentration, R4 = C2H6 concentration / C2H2 concentration, and R5 = CO2 concentration / H2O concentration. Determine the defect type of high-voltage cable joint A based on the range of gas ratios between various gas types. R1 to R5 are the first gas ratio, the second gas ratio, the third gas ratio, the fourth gas ratio, and the fifth gas ratio, respectively.

[0055] Defect types include overheating, partial discharge, arcing failure, and moisture.

[0056] If R1 > K1high If R2 < K2, R3 < K3, and R4 > K4, then it is judged as an overheating defect; if R1 < K... 1low If R3 < K3 and R4 > K4, then it is judged to be a partial discharge defect; if K 1low ≤R1≤K 1high K 2low ≤R2≤K 2high If R3≥K3 and R4<K4, then it is judged as an arc fault defect; if K 1low ≤R1≤K 1high If R4 ≥ K4 and R5 ≤ K5, then it is judged as a moisture defect; where K 1low K is the first set lower limit of the range. 1high Set the upper limit of the range for the first; K 2low K is the second set lower limit of the range. 2high K1 is the upper limit of the second set range; K2 is the second set value; K3 is the third set value; K4 is the fourth set value; K5 is the fifth set value.

[0057] Preferably, a photoacoustic sensor with a TU-shaped microcantilever beam structure is designed as the detection module 5 for measurement. The structure is as follows: Figure 3 As shown:

[0058] The analytical expression for the first natural frequency of the TU-shaped microcantilever beam is obtained through theoretical analysis, as follows:

[0059]

[0060] Take the elastic modulus E = 1.124e + 0.11 N / m 2 Mass density ρ = 2330 kg / m³ 3 Given h = 0.01 mm, b1 = 0.8 mm, b2 = 1 mm, b3 = 0.5 mm, l1 = 0.8 mm, l2 = 0.4 mm, and l3 = 1 mm, the first natural frequency is calculated to be f = 5257.39 Hz.

[0061] Light source 7 is used to provide light of a wavelength for detecting the escaping gas. Preferably, a mid-infrared wavelength light source is selected, and the light source characteristics corresponding to the gas are shown in Table 1.

[0062] Table 1 Light source characteristics of different escaping gases

[0063]

[0064] Preferably, a battery is used to power the device in the live detection mode, and an AC power supply is used to power the device in the online monitoring mode.

[0065] Example 2:

[0066] like Figure 1As shown, the present invention provides a method for detecting gas escaping from a high-voltage cable joint, comprising: a light source 7 emitting a light beam with a characteristic wavelength and irradiating the gas escaping from the high-voltage cable joint A stored in a photoacoustic cell 4; receiving and exciting the escaping gas to generate a photoacoustic signal; determining the type and concentration information of the escaping gas based on the photoacoustic signal; processing the type and concentration information of the escaping gas to obtain a demodulated digital signal; and analyzing the demodulated digital signal to determine whether the high-voltage cable joint A has a defect and the type of defect.

[0067] Connect the detection interface 1 of the device to the detection hole C of the high-voltage cable connector A to form a closed air path. Turn on the air pump 3 to allow gas to enter the photoacoustic cell 4. Detect the type and concentration of gas escaping from the high-voltage cable connector in the photoacoustic cell 4 at different times to determine the defect type of the high-voltage cable connector A.

[0068] The discrimination method is:

[0069] The presence of defects is determined using various gas threshold values; these threshold values ​​are typically selected within ±30% of the initial measurement at high-voltage cable connector A. Preferably, the data in Table 2 can be used. If the concentration of a particular type of gas is greater than or equal to the gas threshold value, a defect exists. The types of gases emitted include CO2, CO, CH4, C2H2, C2H4, C2H6, and H2O.

[0070] Table 2 Thresholds of 7 Characteristic Gases in Normal High-Voltage Cable Joints

[0071]

[0072] Calculate the gas ratio to identify the type of defect inside the high-voltage cable joint.

[0073] Preferably, the identification of internal overheating, partial discharge, arcing faults, and moisture in the joint is performed using gas ratios: (R1 = CO concentration / CO2 concentration), (R2 = C2H2 concentration / C2H4 concentration), (R3 = C2H2 concentration / CH4 concentration), (R4 = C2H6 concentration / C2H2 concentration), and (R5 = CO2 concentration / H2O concentration). In this embodiment,

[0074] Table 3. Diagnostic Criteria for Ratio

[0075] Defect types R1 R2 R3 R4 R5 overheat ＞0.5 ＜0.75 ＜0.3 ＞0.4 / Partial discharge ＜0.2 / ＜0.3 ＞0.4 / Arc fault ≥0.2～≤0.5 ≥0.01～≤0.1 ≥0.3 ＜0.4 / Moisture ≥0.2～≤0.5 / / ≥0.4 ≤0.05

[0076] Example 3:

[0077] like Figure 4 , Figure 5As shown, this invention provides a method for detecting gas escaping from a high-voltage cable joint. The method involves connecting the first detection interface 1-1 and the second detection interface 1-2 (two detection interfaces in this embodiment) of the device to the first detection hole C1 and the second detection hole C2 (two detection holes in this embodiment) of the protective copper shell B, forming a closed gas path. The FPGA core control and demodulation system 8 sequentially controls the solenoid valves 2 (first solenoid valve 2-1, second solenoid valve 2-2) and the air pump 3 to pump the gas escaping from the high-voltage cable joint A inside the protective copper shell B into the photoacoustic cell 4. Then, the light source is controlled to emit a light beam with a characteristic wavelength. The light beam enters the photoacoustic cell 4, exciting the escaping gas to generate a photoacoustic signal. This signal is received by the detection module 5, and after passing through the AD conversion module 6, a digital signal is acquired and transmitted to the FPGA core control and demodulation system 8 for real-time calculation. Then, it is uploaded to the display and analysis module 10 via the communication module 9 for processing and analysis. The display and analysis module 10 displays the type and concentration of the gas escaping from the high-voltage cable joint A at the detection time. Figure 4 As shown, the device power supply 11 is battery powered, and the working mode is a handheld device to perform live testing on high-voltage cable joints.

[0078] Table 4 shows the seven characteristic gases of the high-voltage cable joint in this embodiment.

[0079]

[0080] Calculate the gas ratio to identify the type of defect inside the high-voltage cable joint. R1 = 0.8, R2 = 0.2, R3 = 0.27, R4 = 0.75, R5 = 1. According to Table 3, the defect type is identified as overheating, and the defect type is displayed through the display analysis module 10.

[0081] The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims

1. A gas detection device for high-voltage cable joints, characterized in that: It includes a photoacoustic cell (4), a detection module (5), a light source (7), an FPGA core control and demodulation system (8), and a display and analysis module (10). The photoacoustic cell (4) is used to store the gas escaping from the high-voltage cable joint (A). The light source (7) is used to emit a light beam with a characteristic wavelength and irradiate the gas escaping from the high-voltage cable joint (A) stored in the photoacoustic cell (4). The detection module (5) is used to receive the gas escaping and generate a photoacoustic signal. Based on the photoacoustic signal, the type and concentration information of the gas escaping are determined. The FPGA core control and demodulation system (8) is used to process the type and concentration information of the gas escaping to obtain the demodulated digital signal. The display and analysis module (10) is used to analyze the demodulated digital signal to determine whether there is a defect in the high-voltage cable joint (A) and the type of defect. The display analysis module (10) compares the concentration of each type of gas escaping from the high-voltage cable joint (A) with the corresponding gas threshold. If the concentration of that type of gas is greater than or equal to the gas threshold, it is determined that the high-voltage cable joint (A) has a defect. The types of gases that escape include CO2, CO, CH4, C2H2, C2H4, C2H6, and H2O; Calculate the gas ratios between various gas types based on the concentration of each gas type in the escaping gas: R1 = CO concentration / CO2 concentration, R2 = C2H2 concentration / C2H4 concentration, R3 = C2H2 concentration / CH4 concentration, R4 = C2H6 concentration / C2H2 concentration, and R5 = CO2 concentration / H2O concentration. Determine the defect type of the high-voltage cable joint (A) based on the range of the gas ratios between various gas types. R1~R5 are the first gas ratio, the second gas ratio, the third gas ratio, the fourth gas ratio, and the fifth gas ratio, respectively. The defect types include overheating, partial discharge, arcing failure, and moisture. If R1 > K 1high If R2 < K2, R3 < K3, and R4 > K4, then it is determined to be an overheating defect; If R1 < K 1low If R3 < K3 and R4 > K4, then it is determined to be a partial discharge defect; If K 1low ≤R1≤K 1high K 2low ≤R2≤K 2high If R3≥K3 and R4<K4, then it is judged to be an arc fault defect; If K 1low ≤R1≤K 1high If R4≥K4 and R5≤K5, it is judged as a moisture defect; Among them, K 1low K is the first set lower limit of the range. 1high Set the upper limit of the range for the first; K 2low K is the second set lower limit of the range. 2high K1 is the upper limit of the second set range; K2 is the second set value; K3 is the third set value; K4 is the fourth set value; K5 is the fifth set value.

2. The gas detection device escaping from a high-voltage cable joint according to claim 1, characterized in that: It also includes a detection interface (1), a solenoid valve (2) and an air pump (3). The detection interface (1) is used to connect to the detection hole (C) of the protective copper shell (B) of the high-voltage cable connector (A). The air pump (3) is connected to the detection interface (1) to pump the gas escaping from the protective copper shell (B) into the photoacoustic cell (4). The solenoid valve (2) is connected between the detection interface (1) and the air pump (3) to control the flow direction and switching of the escaping gas. The FPGA core control and demodulation system (8) is used to control the opening and closing of the light source (7), the opening degree of the solenoid valve (2), and the opening and closing of the air pump (3).

3. The gas detection device for high-voltage cable joints according to claim 2, characterized in that: It also includes an AD conversion module (6), which is connected between the detection module (5) and the FPGA core control and demodulation system (8) to process the type and concentration information of the escaping gas to obtain a digital signal.

4. A method for detecting gas escaping from a high-voltage cable joint, characterized in that: include The light source (7) emits a beam of light with a characteristic wavelength and irradiates the gas escaping from the high-voltage cable joint (A) stored in the photoacoustic pool (4). The emitted gas is excited to generate a photoacoustic signal. The type and concentration information of the emitted gas are determined based on the photoacoustic signal. The type and concentration information of the emitted gas are processed to obtain a demodulated digital signal. The demodulated digital signal is analyzed to determine whether there is a defect in the high-voltage cable joint (A) and the type of defect. The concentration of each type of gas escaping from the high-voltage cable joint (A) is compared with the corresponding gas threshold. If the concentration of that type of gas is greater than or equal to the gas threshold, it is determined that the high-voltage cable joint (A) has a defect. The types of gases that escape include CO2, CO, CH4, C2H2, C2H4, C2H6, and H2O; Calculate the gas ratios between various gas types based on the concentration of each gas type in the escaping gas: R1 = CO concentration / CO2 concentration, R2 = C2H2 concentration / C2H4 concentration, R3 = C2H2 concentration / CH4 concentration, R4 = C2H6 concentration / C2H2 concentration, and R5 = CO2 concentration / H2O concentration. Determine the defect type of the high-voltage cable joint (A) based on the range of the gas ratios between various gas types. R1~R5 are the first gas ratio, the second gas ratio, the third gas ratio, the fourth gas ratio, and the fifth gas ratio, respectively. The defect types include overheating, partial discharge, arcing failure, and moisture. If R1 > K 1high If R2 < K2, R3 < K3, and R4 > K4, then it is determined to be an overheating defect; If R1 < K 1low If R3 < K3 and R4 > K4, then it is determined to be a partial discharge defect; If K 1low ≤R1≤K 1high K 2low ≤R2≤K 2high If R3≥K3 and R4<K4, then it is judged to be an arc fault defect; If K 1low ≤R1≤K 1high If R4≥K4 and R5≤K5, it is judged as a moisture defect; Among them, K 1low K is the first set lower limit of the range. 1high Set the upper limit of the range for the first; K 2low K is the second set lower limit of the range. 2high K1 is the upper limit of the second set range; K2 is the second set value; K3 is the third set value; K4 is the fourth set value; K5 is the fifth set value.

Images