Cable degassing monitoring method and system based on hot air circulation

Abstract

The embodiment of the present application belongs to the technical field of cable testing, and particularly relates to a cable degassing monitoring method and system based on hot air circulation, wherein a degassing room forms a closed heating space; the hot air circulation system comprises an air inlet unit located at the bottom and an air outlet unit located at the top, and forms a circulating air flow from bottom to top; a plurality of through ventilation holes are formed in the side plate and / or the barrel of the cable reel for guiding the circulating air flow to penetrate between the internal layers of cables; the sensor module comprises an air inlet temperature sensor, an air outlet temperature sensor and a methane concentration sensor; the monitoring terminal is connected with the sensor module, and is used for receiving and displaying temperature and methane concentration data. The present application breaks the closed barrier of the traditional reel to the internal air flow through the design of the ventilation holes of the cable reel, forces the hot air to penetrate between the cable layers and quickly take the escaped methane to the air outlet unit, and realizes real-time and accurate monitoring under the premise of not damaging the cable and not interrupting the process in combination with the sensor arrangement at the air outlet unit.

Description

Technical Field

[0001] This invention relates to the field of cable testing technology, specifically to a cable degassing monitoring method and system based on hot air circulation. Background Technology

[0002] After the cross-linking process of high-voltage cables, residual byproducts (mainly methane) in the insulation layer need to be removed through a degassing process to improve the electrical performance and service life of the cable. Currently, cable degassing generally involves placing the entire cable reel in a sealed degassing chamber and heating it with hot air at around 70°C for several days to cause the methane to escape from the insulation layer.

[0003] Currently, determining the degassing endpoint mainly relies on manual sampling and testing. Operators must pause heating, wait for the degassing chamber to cool down, and then enter to cut samples from the cable reel for methane content testing. This method requires interrupting the process and cooling down, resulting in significant energy waste, extended production cycles, and a prominent contradiction between energy consumption and efficiency. Furthermore, sampling and testing are discrete point checks, making it impossible to monitor the degassing progress in real time, and manual operation in high-temperature environments poses safety hazards such as benzene poisoning and burns.

[0004] If we try to apply industrial remote monitoring technology to the degassing process to monitor temperature and methane concentration changes during cable degassing, the degassing endpoint can be determined by combining empirical formulas or fitting models. However, this method requires sufficiently accurate monitoring data. Conventional temperature and gas concentration sensors are mostly suspended directly in the degassing chamber. Due to the large volume of the degassing chamber and the enclosed structure of the cable reel itself, there are dead zones in the hot air circulation (especially below the cable reel and between cable layers), making it difficult for the sensor measurements to accurately reflect the true degassing state inside the cable insulation layer. The representativeness and accuracy of the measurement data are insufficient, and it cannot be used as a reliable input parameter to guide production or establish an accurate degassing model. Summary of the Invention

[0005] This invention provides a cable degassing monitoring method and system based on hot air circulation. It is a system and method that can acquire temperature and methane concentration parameters in real time and accurately during the degassing process without damaging the cable or interrupting the process, providing reliable data support for the scientific determination of the degassing endpoint.

[0006] The first aspect of this invention discloses a cable degassing monitoring system based on hot air circulation, comprising: The degassing chamber forms a sealed heating space; A hot air circulation system, installed inside the degassing chamber, includes an air inlet unit located at the bottom of the degassing chamber and an air outlet unit located at the top of the degassing chamber, used to form a bottom-up circulating airflow inside the degassing chamber; The cable reel, located inside the degassing chamber, is used to support the cable to be tested. Several through ventilation holes are provided on the side plate and / or cylinder of the cable reel to guide the circulating airflow from the outside of the cable reel to the spaces between the internal layers of cables. The sensor module includes an inlet air temperature sensor located at the inlet air unit, an outlet air temperature sensor located at the outlet air unit, and a methane concentration sensor. The monitoring terminal, connected to the sensor module, is used to receive and display temperature and methane concentration data.

[0007] Furthermore, the air inlet unit includes a first air inlet unit disposed at the bottom of the rear wall of the degassing chamber and a second air inlet unit disposed at the bottom of the side walls of the degassing chamber; the air outlet unit includes a first air outlet unit disposed at the top of the rear wall of the degassing chamber and a second air outlet unit disposed at the top of the side walls of the degassing chamber.

[0008] Furthermore, the first air inlet unit has at least one air inlet, and the second air inlet unit has multiple air inlets; the first air outlet unit has at least one air outlet, and the second air outlet unit has multiple air outlets; the air inlet temperature sensor and the methane concentration sensor are respectively installed at each air inlet, and the air outlet temperature sensor and the methane concentration sensor are respectively installed at each air outlet.

[0009] Furthermore, multiple sets of ventilation holes are arranged along the circumference on the side plate, each set of ventilation holes including multiple ventilation holes arranged in parallel and pointing towards the center of the side plate; multiple sets of ventilation holes are arranged along the circumference on the cylinder, each set of ventilation holes including multiple ventilation holes arranged in parallel.

[0010] Furthermore, multiple ventilation holes are evenly distributed on the side plates and cylinder.

[0011] Furthermore, rubber sheets are attached to the side plates and inner sides of the cable reel, and ventilation holes penetrate the cable reel and the rubber sheets.

[0012] Furthermore, the rubber sheet adopts a full-fitting method, with through holes corresponding to the positions of the openings in the disc.

[0013] Furthermore, the air outlet unit is connected to a gas recovery pipe for transporting methane-containing gas to the combustion treatment device.

[0014] Furthermore, the air intake unit is located outside the degassing chamber and is used to heat the air entering the degassing chamber.

[0015] A second aspect of this invention discloses a method for monitoring cable degassing based on hot air circulation, comprising the following steps: The cable to be degassed is wound around a cable reel with several through ventilation holes, and the cable reel is placed inside the degassed chamber. When the hot air circulation system is started, hot air is sent in through the bottom air inlet unit, passes through the ventilation holes on the surface of the cable reel to the spaces between the internal layers of cables, carries away the escaping methane and is discharged through the top air outlet unit, forming a bottom-up circulating airflow. By using an inlet air temperature sensor installed at the inlet air unit, an outlet air temperature sensor installed at the outlet air unit, and a methane concentration sensor, the inlet air temperature, outlet air temperature, and methane concentration data of the outlet air unit are collected in real time. The collected data is transmitted to the monitoring terminal for display.

[0016] Compared with existing technologies, one or more of the above technical solutions have the following beneficial effects: By designing ventilation holes on the side plates and cylinder of the cable reel, the traditional closed-off airflow of the cable reel is broken, allowing hot air to be forced to penetrate between the cable layers and quickly carry the methane escaping from inside to the air outlet unit. At the same time, the methane concentration sensor is placed at the air outlet unit, which is the airflow gathering node. This solves the problem that the measurement value cannot truly reflect the degassing status inside the cable because the sensor is directly suspended in the degassing chamber space in the traditional monitoring method. This enables real-time and accurate monitoring of the degassing process without damaging the cable or interrupting the process. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 A schematic diagram of a cable degassing monitoring system based on hot air circulation provided for one or more embodiments of the present invention; Figure 2 A top view of a cable degassing monitoring system based on hot air circulation provided for one or more embodiments of the present invention; Figure 3 A schematic diagram of a duct in a cable degassing monitoring system based on hot air circulation, provided for one or more embodiments of the present invention; Figure 4 This is a schematic diagram of the main structure of a cable reel provided in one or more embodiments of the present invention; Figure 5 This is a side view of a cable reel structure provided in one or more embodiments of the present invention; Figure 6 A schematic diagram of heat flow velocity streamline distribution provided for one or more embodiments of the present invention; Figure 7 A schematic diagram illustrating the temperature change of the degassing chamber over time, provided for one or more embodiments of the present invention; Figure 8This is a schematic diagram illustrating the change of the average methane concentration in the insulating layer with degassing time at different temperatures, provided for one or more embodiments of the present invention. Figure 9 This is a schematic diagram illustrating the variation of the average methane concentration in the insulation layer of a 110kV cable with degassing time under different nominal cross-sections, provided in one or more embodiments of the present invention.

[0019] In the diagram: 1 First air outlet unit, 2 First air inlet unit, 3 Second air outlet unit, 4 Second air inlet unit, 5 Air duct, 10 Side plate, 11 Cylinder. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] Terminology Explanation: The cable degassing test refers to the process of placing the entire reel of high-voltage cable in a specific temperature environment and continuously heating it after the cross-linking is completed, so as to promote the full release of the residual cross-linking byproducts (mainly methane gas) in the insulation layer, so as to make the electrical performance of the cable reach a stable state.

[0023] In cable degassing experiments, the following methods are mainly used to determine the degassing endpoint: The laboratory sampling analysis method involves taking insulation samples from cable reels and using a gas chromatograph to quantitatively test the residual methane concentration, with the endpoint criterion being whether it reaches a standard threshold (e.g., ≤50ppm). The empirical formula method sets a fixed degassing time based on cable specifications and previous process verification (e.g., 7 days for 110kV cable degassing). Auxiliary characterization methods, such as heating the sample in an oil cup and observing the escape of bubbles, are used to make a rough qualitative judgment.

[0024] However, the sampling analysis method requires interruption of heating and cooling before operation, which not only damages the cable integrity but also has high energy consumption and low efficiency; the empirical formula method is an open-loop control that cannot cope with batch differences in materials and is prone to under-degassing or over-degassing; the auxiliary characterization method is highly subjective, cannot be quantitative, and lacks reliability. None of these three methods can achieve real-time and accurate monitoring of the degassing process inside the cable without interrupting the degassing process.

[0025] The purpose of this solution is to provide a system and method that can acquire temperature and methane concentration parameters in real time and accurately during the degassing process without damaging the cable or interrupting the process, so as to provide reliable data support for the scientific determination of the degassing endpoint.

[0026] To achieve the above objectives, this solution provides a cable degassing monitoring method and system based on hot air circulation. A hot air penetration path is constructed through the cable reel's perforated structure, allowing the escaping gas inside to quickly enter the circulating airflow. At the same time, sensors are deployed at key airflow nodes to achieve accurate acquisition of temperature and methane concentration in a large space, providing reliable input parameters for the subsequent degassing endpoint determination model.

[0027] Example 1: A cable degassing monitoring system based on hot air circulation includes: The degassing chamber forms a sealed heating space; A hot air circulation system, installed inside the degassing chamber, includes an air inlet unit located at the bottom of the degassing chamber and an air outlet unit located at the top of the degassing chamber, used to form a bottom-up circulating airflow inside the degassing chamber; The cable reel, located inside the degassing chamber, is used to support the cable to be tested. Several through ventilation holes are provided on the side plate and / or cylinder of the cable reel to guide the circulating airflow from the outside of the cable reel to the spaces between the internal layers of cables. The sensor module includes an inlet air temperature sensor located at the inlet air unit, an outlet air temperature sensor located at the outlet air unit, and a methane concentration sensor. The monitoring terminal, connected to the sensor module, is used to receive and display temperature and methane concentration data.

[0028] The degassing chamber forms a sealed heated space. A hot air circulation system is installed inside the degassing chamber, including an air inlet unit at the bottom and an air outlet unit at the top, to create an upward circulating airflow within the chamber. Cable reels are arranged inside the degassing chamber to carry the cables under test. The sensor module includes an inlet air temperature sensor at the air inlet unit, an outlet air temperature sensor at the outlet unit, and a methane concentration sensor. A monitoring terminal is connected to the sensor module to receive and display temperature and methane concentration data.

[0029] like Figures 1 to 3 As shown, the degassing chamber is equipped with air ducts 5, which are located at the top and bottom of the rear wall, as well as the top and bottom of the left and right side walls. Among them, the air ducts located at the top of the rear wall and the two side walls are air outlet ducts, and the air ducts located at the bottom of the rear wall and the two side walls are air inlet ducts.

[0030] A first air outlet unit 1 is installed on the air outlet duct located on the rear wall. The first air outlet unit 1 has one air outlet, which is equipped with a methane concentration sensor and a temperature sensor. Second air outlet units 3 are installed on the air outlet ducts located on the two side walls. Each second air outlet unit 3 has three air outlets (three air outlets per side wall), and each air outlet is equipped with a methane concentration sensor and a temperature sensor.

[0031] A first air inlet unit 2 is installed on the air inlet duct located on the rear wall. The first air inlet unit 2 has one air inlet, which is equipped with a methane concentration sensor and a temperature sensor. Second air inlet units 4 are installed on the air inlet ducts located on the two side walls. Each second air inlet unit 4 has three air inlets (three air inlets per side wall), and each air inlet is equipped with a methane concentration sensor and a temperature sensor.

[0032] All air intake units heat the air outside the degassing chamber before sending it into the chamber. All methane-containing gases recovered by the exhaust units are transported through pipelines and then burned to meet environmental protection requirements.

[0033] like Figure 4 and Figure 5 As shown, the cable reel includes a cylindrical body 11 and side plates 10 connected to both ends of the cylindrical body 11. The side plates 10 have multiple sets of ventilation holes arranged circumferentially, each set including multiple parallel ventilation holes pointing towards the center of the side plate 10. The cylindrical body 11 also has multiple sets of parallel ventilation holes arranged circumferentially.

[0034] Specifically, the ventilation holes have a diameter of 50mm. Eight rows of ventilation holes, ten holes per row, are evenly distributed on the cylinder 11. Three rows of ventilation holes, ten holes per row, are evenly distributed on the side plate 10. The opening size is designed to be relatively small to avoid indentations when cables come into contact with the edges of the openings.

[0035] The ventilation holes on the cable reel are distributed according to a specific pattern. The distribution density, hole size and opening angle of the ventilation holes are optimized by fluid dynamics simulation to form a controllable micro-positive pressure airflow field inside the reel. This allows hot air to penetrate the cable winding layer by layer at a predetermined flow rate and direction, forming a uniform forced convection boundary layer on the surface of each cable layer.

[0036] After the opening is made, a rubber sheet is attached to the side plate of the cable tray and the inner side of the cylinder. For example, a 2cm thick EVA rubber sheet is attached to the side plate of the cable tray and the inner side of the cylinder, and the opening penetrates through the cable tray and the EVA sheet. The EVA rubber sheet is fully bonded, and through holes are made at the corresponding positions of the openings in the cable tray. The Shore hardness of the EVA rubber sheet is 60 to 100, and the temperature resistance rating is 90℃.

[0037] Depending on the thickness of the disc cylinder, the size and location of the holes, the opening area in this embodiment is 5%-10% (e.g., 8%). If the opening area is too small, the airflow resistance will be high, the static pressure will drop sharply, and the air volume at the terminal will be insufficient. If the opening area is too large, the static pressure inside the pipe will be insufficient, resulting in uneven airflow distribution and a much larger air volume at the front end than at the terminal end. The overall flow velocity will be too low, affecting the heat coverage efficiency.

[0038] The opening area is calculated as 5%. Taking a 4000mm×2600mm×2300mm disc as an example, the cross-sectional area of ​​the disc cylinder is S=πDL=3.14×2.6×2.3=18.79m. 2 The area of ​​a single hole is S1 = πr 2 =3.14 × 0.025 × 0.025 = 0.01963m 2 The number of openings N = S × 8% / S1 = 18.79 × 0.08 / 0.01963 = 76.6.

[0039] By designing openings in the cable reel, the traditional "flow around" process, confined to the outside of the reel, is upgraded to a "penetrating flow" that runs through the cable layers. For example... Figure 6 As shown in the heat flow velocity streamline distribution inside the degassing chamber, when the cable reel is not perforated, the heat flow passes through the cylindrical part of the cable reel and circulates around it, causing heat to be gradually transferred from the outer layer cable to the inner layer cable (the cable reel is usually wrapped with multiple layers of cable), resulting in uneven heating. Some experimental data after the perforation is made are shown in Table 1, where T1-T4 are the temperature sensors during the experiment.

[0040] Table 1 Experimental data after opening the hole

[0041] After the cable under test is wound onto the cable reel, it is pushed into the degassing chamber along the axial direction of the reel. The radial openings on the side plate of the cable reel break the path of the hot air rising along the wall, causing it to form a radial jet under pressure difference, forcibly entering the gaps between the cable layers. The axial openings on the cable reel cylinder create longitudinal microchannels, generating a negative pressure suction effect between the cable layers using Bernoulli's principle. This combination fundamentally solves the problem of hot air short-circuiting caused by traditional enclosed reels, ensuring that the hot air no longer only exchanges heat with the outer surface of the reel but directly washes over the surface of each layer of cable insulation, significantly increasing the effective heat exchange area.

[0042] This qualitative change in fluid dynamics brings dual process advantages. On the one hand, forced convection ensures the uniformity of the temperature field across the cable reel cross-section, eliminating the temperature gradient of "external heat and internal cold" in traditional processes, making the degassing rates of the inner and outer cable layers more consistent, and avoiding the quality risks of local overheating or insufficient degassing. On the other hand, the negative pressure suction effect can forcibly "pull out" the methane gas deposited between the cable layers due to its high density, allowing it to quickly enter the mainstream circulating airflow, solving the degassing bottleneck caused by internal gas accumulation, thereby significantly improving degassing efficiency and shortening the process cycle.

[0043] Meanwhile, this structure lays the physical foundation for accurate sensor measurements. By allowing sufficient escape and mixing of the internal gas through the openings, the methane concentration at the outlet can represent the average escape amount of the entire cable reel, establishing a stable mapping relationship with the actual concentration inside the cable. Simultaneously, the uniform temperature field enables the selected sensor at the top of the degassing chamber to reliably reflect the average temperature of the cable itself, providing accurate input parameters for subsequent temperature compensation and degassing endpoint determination. In short, the opening structure makes the core concept of "using spatial measurements to invert the internal state" technically feasible.

[0044] Hot circulating air is blown into the degassing chamber through the air inlet unit below, and after being turbulent by the cable reel, it is discharged from the air outlet unit at the top. In traditional solutions, the hot air mainly carries away the by-products escaping from the surface of the cable reel, while the area below the cable reel is relatively enclosed, where by-products tend to accumulate and are difficult to be carried away by the hot air.

[0045] In this embodiment, after ventilation holes are opened on the cable reel, hot circulating air can pass through the holes in the side plate and the cylinder and enter between the layers of cables inside the cable reel, forming an overall air convection, which promptly carries away the by-products escaping from the insulation core of each layer of cable, significantly improving the degassing efficiency.

[0046] Regarding sensor placement, if sensors are placed directly inside, in the middle, or on the outer layer of the cable reel, sensors in the inner and middle layers will fail due to pressure from the outer cable, and the sensors may also cause indentations on the cable surface, affecting cable quality. When sensors are placed on the outer layer, it is difficult to meet the requirements for repeated testing due to the different placement positions in the 360° direction of the outer layer, resulting in poor quality consistency.

[0047] To address the aforementioned issues, this embodiment employs an indirect measurement method, placing sensors at the air outlet unit to monitor the overall temperature and byproduct concentration within the degassing chamber to reflect the degassing status inside the cable. To achieve this, a mapping relationship needs to be established beforehand between the overall concentration within the degassing chamber and the byproduct concentration in the middle layer of the cable reel.

[0048] The process for establishing the mapping relationship is as follows: For 110kV high-voltage cables, within a degassing cycle (e.g., 5 days), the methane concentration in the degassing chamber is monitored at a fixed time each day, and simultaneously, the concentration of cross-linking byproducts is tested by sampling the middle layer of the cable reel. The two sets of data are then correlated. This experiment is repeated multiple times, the data are processed, and the average value is taken to establish a mapping relationship from 0 to 5 days. For high-voltage cables of 220kV and above, the same method is used to establish a mapping relationship based on the actual degassing cycle (e.g., 12 days).

[0049] Regarding the sensor placement: In the formal system structure section (this solution), the sensor module includes an inlet air temperature sensor installed at each air inlet, an outlet air temperature sensor installed at each air outlet, and a methane concentration sensor installed at each air outlet.

[0050] To verify that the outlet temperature sensor readings accurately reflect the temperature of the cable reel, preliminary experiments involved placing temperature sensors at different locations on the top of the degassing chamber. These sensors were compared with thermocouples arranged on the outer layer of the cable reel, and the location with the best consistency was selected as a reference point to establish a mapping relationship between the outlet temperature and the cable reel temperature. Experiments showed that after correction using the mapping relationship, the error between the outlet temperature sensor readings and the actual temperature of the cable reel could be controlled within ±1.5℃.

[0051] Figures 7 to 9 The data compares the temperature of the temperature sensor with the temperature of the outer layer of the cable reel at different locations. In this embodiment, the location with the best temperature consistency was ultimately selected for sensor installation.

[0052] The monitoring terminal connects to the sensor module to receive and display in real-time data on inlet air temperature, outlet air temperature, and methane concentration at the outlet. All data is transmitted to a display screen in the information center for centralized monitoring.

[0053] If the methane concentration still does not meet the acceptable standard after the pre-set degassing time, the operator can extend the degassing time until the concentration meets the standard. The alarm function can be configured or not configured according to actual needs.

[0054] This embodiment utilizes ventilation holes on the cable reel side plate and cylinder to transform hot air from a "circumferential flow" to a "penetrating flow," forcing it into the cable layers for thorough heat exchange and rapidly carrying the escaping methane to the outlet. Simultaneously, temperature and methane concentration sensors are positioned at key airflow points such as the inlet and outlet, resolving the issue of traditional monitoring methods where sensors directly suspended in the degassing chamber fail to accurately reflect the internal degassing status of the cable. By pre-establishing a mapping relationship, operators can indirectly determine the true degassing progress inside the cable based on the measured concentration at the outlet, achieving real-time and accurate monitoring without damaging the cable or interrupting the process.

[0055] Example 2: A cable degassing monitoring method based on hot air circulation includes the following steps: The cable to be degassed is wound around a cable reel with several through ventilation holes, and the cable reel is placed inside the degassed chamber. When the hot air circulation system is started, hot air is sent in through the bottom air inlet unit, passes through the ventilation holes on the surface of the cable reel to the spaces between the internal layers of cables, carries away the escaping methane and is discharged through the top air outlet unit, forming a bottom-up circulating airflow. By using an inlet air temperature sensor installed at the inlet air unit, an outlet air temperature sensor installed at the outlet air unit, and a methane concentration sensor, the inlet air temperature, outlet air temperature, and methane concentration data of the outlet air unit are collected in real time. The collected data is transmitted to the monitoring terminal for display.

[0056] By designing ventilation holes on the side plates and cylinder of the cable reel, the traditional closed-off airflow of the cable reel is broken, allowing hot air to be forced to penetrate between the cable layers and quickly carry the methane escaping from inside to the air outlet unit. At the same time, the methane concentration sensor is placed at the air outlet unit, which is the airflow gathering node. This solves the problem that the measurement value cannot truly reflect the degassing status inside the cable because the sensor is directly suspended in the degassing chamber space in the traditional monitoring method. This enables real-time and accurate monitoring of the degassing process without damaging the cable or interrupting the process.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cable degassing monitoring system based on hot air circulation, characterized in that, include: The degassing chamber forms a sealed heating space; A hot air circulation system is installed inside the degassing chamber, including an air inlet unit located at the bottom of the degassing chamber and an air outlet unit located at the top of the degassing chamber, for forming a bottom-up circulating airflow inside the degassing chamber; A cable reel is arranged inside the degassing chamber to support the cable to be tested; the side plate and / or cylinder of the cable reel are provided with several through ventilation holes to guide the circulating airflow from the outside of the cable reel to the spaces between the internal layers of cables; The sensor module includes an inlet air temperature sensor disposed at the air inlet unit, an outlet air temperature sensor disposed at the air outlet unit, and a methane concentration sensor. The monitoring terminal is connected to the sensor module and is used to receive and display temperature and methane concentration data.

2. The cable degassing monitoring system based on hot air circulation as described in claim 1, characterized in that, The air intake unit includes a first air intake unit disposed at the bottom of the rear wall of the degassing chamber and a second air intake unit disposed at the bottom of the side walls of the degassing chamber; the air outlet unit includes a first air outlet unit disposed at the top of the rear wall of the degassing chamber and a second air outlet unit disposed at the top of the side walls of the degassing chamber.

3. The cable degassing monitoring system based on hot air circulation as described in claim 2, characterized in that, The first air inlet unit has at least one air inlet, and the second air inlet unit has multiple air inlets; the first air outlet unit has at least one air outlet, and the second air outlet unit has multiple air outlets; the air inlet temperature sensor is correspondingly disposed at each air inlet, and the air outlet temperature sensor and the methane concentration sensor are correspondingly disposed at each air outlet.

4. The cable degassing monitoring system based on hot air circulation as described in claim 1, characterized in that, The ventilation holes are arranged in multiple groups along the circumference on the side plate, and each group of ventilation holes includes multiple ventilation holes arranged in parallel and pointing towards the center of the side plate; the ventilation holes are also arranged in multiple groups along the circumference on the cylinder, and each group of ventilation holes includes multiple ventilation holes arranged in parallel.

5. The cable degassing monitoring system based on hot air circulation as described in claim 1 or 4, characterized in that, Multiple ventilation holes are evenly distributed on the side plate and the cylinder.

6. The cable degassing monitoring system based on hot air circulation as described in claim 1, characterized in that, The side plate and inner side of the cable reel are fitted with rubber plates, and the ventilation holes penetrate the cable reel and the rubber plates.

7. The cable degassing monitoring system based on hot air circulation as described in claim 6, characterized in that, The rubber sheet is fully bonded, and through holes are made at the corresponding positions of the openings in the disc.

8. The cable degassing monitoring system based on hot air circulation as described in claim 1, characterized in that, The air outlet unit is connected to a gas recovery pipeline for transporting methane-containing gas to the combustion treatment device.

9. The cable degassing monitoring system based on hot air circulation as described in claim 1, characterized in that, The air intake unit is located outside the degassing chamber and is used to heat the air entering the degassing chamber.

10. A method for monitoring cable degassing based on the cable degassing monitoring system according to claim 1, characterized in that, Includes the following steps: The cable to be degassed is wound around a cable reel with several through ventilation holes, and the cable reel is placed inside the degassed chamber. When the hot air circulation system is started, hot air is sent in through the bottom air inlet unit, passes through the ventilation holes on the surface of the cable reel to the spaces between the internal layers of cables, carries away the escaping methane and is discharged through the top air outlet unit, forming a bottom-up circulating airflow. By using an inlet air temperature sensor installed at the inlet air unit, an outlet air temperature sensor installed at the outlet air unit, and a methane concentration sensor, the inlet air temperature, outlet air temperature, and methane concentration data of the outlet air unit are collected in real time. The collected data is transmitted to the monitoring terminal for display.

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