Pyrolysis experiment system for cable outer sheath

Abstract

The invention provides a cable outer sheath pyrolysis experiment system. The cable outer sheath pyrolysis experiment system comprises a pyrolysis tank body, a gas detection device, a temperature control device and a pressure control device, a heating device is arranged in the pyrolysis tank body; the temperature control device is used for acquiring temperature control information and controlling the heating device to heat the cable outer sheath based on the temperature control information, and the temperature control information comprises set heating time and a set heating temperature value; the pressure control device is used for acquiring air pressure control information and controlling the air pressure in the pyrolysis tank body based on the air pressure control information; and the gas detection device is used for detecting pyrolysis gas generated by heating the cable outer sheath to obtain a detection result. According to the device, the pyrolysis time, temperature and air pressure of the cable outer sheath can be accurately controlled, so that detection results of gas generated by the cable outer sheath under different pyrolysis conditions can be accurately obtained, and better data support is provided for a cable fire early warning scheme.

Description

Technical Field

[0001] The present application relates to the technical field of cable fire warning, and particularly relates to a pyrolysis experiment system for cable outer sheaths. Background Art

[0002] For cable lines, the cable outer sheath mainly serves to achieve electrical isolation between the metal sheath and the grounding electrode, and at the same time forms physical protection for the internal structure of the cable. When the structure of the cable outer sheath is damaged, it is very easy to generate heat at the locally damaged part. If these heat sources are not discovered in time, the cable will develop from local overheating to a cable fire. Existing cable fire detection technologies are difficult to quickly and accurately detect these cable fire hazard points. The cable outer sheath is mostly composed of polymers, and when they are heated, they will decompose to generate gases related to temperature and rarely seen in the air. By studying the correlation between these pyrolysis characteristic gases of the cable outer sheath and temperature, early warning of cable fires can be carried out.

[0003] Currently, there is still a lack of an effective method to understand the pyrolysis characteristics of cable outer sheaths under different pyrolysis conditions. Summary of the Invention

[0004] In view of this, the purpose of the present application is to provide a pyrolysis experiment system for cable outer sheaths, which can achieve precise control of pyrolysis time, temperature, and air pressure, so as to accurately obtain the detection results of the gases generated by the cable outer sheath under different pyrolysis conditions, and provide better data support for the early warning scheme of cable fires.

[0005] In a first aspect, the present application provides a pyrolysis experiment system for cable outer sheaths, the system includes: a pyrolysis tank body, a gas detection device, a temperature control device, and a pressure control device; a heating device is arranged inside the pyrolysis tank body;

[0006] The temperature control device is used to obtain temperature control information, and based on the temperature control information, control the heating device to heat the cable outer sheath, wherein the cable outer sheath is placed on the heating device, and the temperature control information includes a set heating time and a set heating temperature value;

[0007] The pressure control device is used to obtain air pressure control information and control the air pressure in the pyrolysis tank body based on the air pressure control information;

[0008] The gas detection device is used to detect the pyrolysis gas generated by heating the cable outer sheath and obtain a detection result.

[0009] Optionally, the temperature control device includes: a temperature measurement circuit and an arithmetic circuit;

[0010] The temperature measurement circuit is used to measure the first actual temperature value of the heating device;

[0011] The arithmetic circuit is configured to compare the first actual temperature value with the set heating temperature value to obtain a first difference value.

[0012] The arithmetic circuit is further configured to perform an operation based on the first difference value according to the proportional-integral-derivative control algorithm to determine an adjustment parameter.

[0013] The arithmetic circuit is further configured to adjust the output power of the heating module based on the adjustment parameter to heat the outer sheath of the cable based on the set heating temperature.

[0014] Optionally, the temperature measurement circuit is further configured to obtain a temperature compensation value.

[0015] Based on the temperature compensation value, the first actual temperature value is corrected to obtain the second actual temperature value.

[0016] The arithmetic circuit is further configured to compare the second actual temperature value with the set heating temperature value to obtain a second difference value.

[0017] The arithmetic circuit is further configured to perform an operation based on the second difference value according to the proportional-integral-derivative control algorithm to determine the adjustment parameter.

[0018] Optionally, the arithmetic circuit includes a solid-state relay, and the heating device includes a heating wire; the adjustment parameter includes: the conduction time of the solid-state relay and / or the conduction ratio of the heating wire.

[0019] Optionally, the pyrolysis tank body is of a cylindrical structure, made of ordinary austenitic stainless steel 304, with an inner diameter of 300 mm, a height of 300 mm, and a wall thickness of 3 mm.

[0020] Optionally, an opening is provided at the top of the pyrolysis tank body, and the pyrolysis tank body adopts a sealed groove with a flexible graphite metal-sealing ring structure, and is sealed through a flange and bolts.

[0021] Optionally, the heat source of the heating device is a nickel-chromium alloy heating wire.

[0022] Optionally, the gas detection device includes a Fourier transform infrared spectrometer and a gas chromatograph.

[0023] Optionally, a pillar with a predetermined height is provided at the bottom of the pyrolysis tank body, and the heating device is arranged on the pillar.

[0024] Optionally, the system further includes: a three-way valve and an experimental atmosphere gas device. The first end of the three-way valve is connected to the pyrolysis tank body, the second end of the three-way valve is connected to the gas detection device, and the third end of the three-way valve is connected to the experimental atmosphere gas device;

[0025] The experimental atmosphere gas device is used to input experimental atmosphere gas into the pyrolysis tank body.

[0026] It can be seen that a cable outer sheath pyrolysis experiment system disclosed in an embodiment of the present application includes: a pyrolysis tank body, a gas detection device, a temperature control device, and a pressure control device; a heating device is arranged inside the pyrolysis tank body; the temperature control device is used to obtain temperature control information and control the heating device to heat the cable outer sheath based on the temperature control information, wherein the cable outer sheath is placed on the heating device, and the temperature control information includes a set heating time and a set heating temperature value; the pressure control device is used to obtain air pressure control information and control the air pressure in the pyrolysis tank body based on the air pressure control information; the gas detection device is connected to the pyrolysis tank body and is used to detect the pyrolysis gas generated by heating the cable outer sheath to obtain a detection result. The above devices can achieve precise control of the pyrolysis time, temperature, and air pressure of the cable outer sheath, so as to accurately obtain the detection results of the gas generated by the cable outer sheath under different pyrolysis conditions, providing better data support for the early warning scheme of cable fires. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application, and those of ordinary skill in the art can also obtain other drawings based on these drawings.

[0028] Figure 1 is a schematic structural diagram of a cable outer sheath pyrolysis experiment system provided by an embodiment of the present application;

[0029] Figure 2 is a control principle diagram of a temperature control device provided by an embodiment of the present application;

[0030] Figure 3 is a schematic diagram of the temperature field distribution simulation of a high-voltage cable body under different arrangement modes provided by an embodiment of the present application;

[0031] Figure 4 is a schematic diagram of the change curve of the ambient temperature and the maximum temperature of the high-voltage cable provided by an embodiment of the present application;

[0032] Figure 5 is a schematic diagram of the geometric model of a pyrolysis tank body provided by an embodiment of the present application;

[0033] Figure 6 It is a schematic diagram of the temperature field distribution of a heating device inside a pyrolysis tank body provided by an embodiment of the present application at different surface temperatures;

[0034] Figure 7 It is a schematic structural diagram of another cable outer sheath pyrolysis experiment system provided by the present application;

[0035] Figure 8 It is a schematic structural diagram of a pyrolysis tank body provided by an embodiment of the present application;

[0036] Figure 9 It is a schematic diagram of a temperature measurement circuit provided by an embodiment of the present application;

[0037] Figure 10 It is a schematic diagram of a full-bridge control and output circuit provided by an embodiment of the present application;

[0038] Figure 11 It is a schematic diagram of a display and key control circuit provided by an embodiment of the present application;

[0039] Figure 12 It is a three-dimensional surface diagram corresponding to the pyrolysis tank body temperature field simulation data at 250°C provided by an embodiment of the present application;

[0040] Figure 13 It is a schematic diagram of the temperature field distribution of a pyrolysis tank body at a fault temperature of 250°C provided by an embodiment of the present application. Detailed implementation manners

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0042] To facilitate understanding of the technical solutions provided by the present invention, the background technology related to the present utility will be described below first.

[0043] The outer sheath of a cable is mostly composed of polymers. When the temperature is too high, it is prone to decompose and generate a series of gases related to temperature and rarely seen in the air. By studying the correlation between the pyrolysis characteristic gases of the cable outer sheath and temperature, an early warning strategy for cable fires based on the characteristic information of the pyrolysis gases of the outer sheath can be finally established, effectively ensuring power supply safety. Therefore, it is very important to analyze and study the gas production characteristics of the cable outer sheath during pyrolysis. At present, there is still a lack of an effective method or equipment to master the pyrolysis gas production characteristics of the cable outer sheath under different pyrolysis conditions. The applicant found through research that the generation of pyrolysis gases from the cable outer sheath is affected by factors such as temperature, time, and air pressure.

[0044] For this reason, a pyrolysis experiment system for a cable outer sheath provided in this application includes: a pyrolysis tank body, a gas detection device, a temperature control device, and a pressure control device; a heating device is arranged inside the pyrolysis tank body; the temperature control device is used to obtain temperature control information and control the heating device to heat the cable outer sheath based on the temperature control information. Among them, the cable outer sheath is placed on the heating device, and the temperature control information includes the set heating time and the set heating temperature value; the pressure control device is used to obtain air pressure control information and control the air pressure in the pyrolysis tank body based on the air pressure control information; the gas detection device is used to detect the pyrolysis gases generated by heating the cable outer sheath and obtain a detection result. The above devices can achieve precise control of the pyrolysis time, temperature, and air pressure, so as to accurately obtain the detection results of the gases generated by the cable outer sheath under different pyrolysis conditions, providing better data support for the early warning plan of cable fires.

[0045] To facilitate understanding of the technical solution provided in this application, the following will describe a pyrolysis experiment system for a cable outer sheath provided in this application with reference to the drawings. See Figure 1 , Figure 1 is a schematic structural diagram of a pyrolysis experiment system for a cable outer sheath provided in an embodiment of this application. The system includes: a pyrolysis tank body 101, a gas detection device 102, a temperature control device 103, and a pressure control device 104; a heating device 105 is arranged inside the pyrolysis tank body 101.

[0046] The temperature control device 103 is used to obtain temperature control information and control the heating device to heat the cable outer sheath based on the temperature control information. Among them, the cable outer sheath is placed on the heating device 105, and the temperature control information includes the set heating time and the set heating temperature value.

[0047] In the embodiment of this application, the temperature control device 103 can be connected to the heating device 105 inside the pyrolysis tank body 101 through a temperature control circuit to achieve temperature control of the heating device.

[0048] In the embodiments of the present application, the cable outer sheath can be a high-voltage cable outer sheath, a medium-voltage cable outer sheath, etc.

[0049] The present application does not limit the specific manner in which the temperature control device obtains temperature control information. As an example, the temperature control device 103 of the present application may include a display panel. During the experiment, the experimenter can input temperature control information through the display panel. It can be understood that the set heating time is used to indicate how long the heating device needs to be heated, and the set heating temperature value is used to indicate the temperature to which the heating device needs to be heated. As another example, the temperature control device can also receive the temperature control information sent by the user through the network. It can be understood that the experimenter can set the temperature control information on the smart device through relevant software and send it to the temperature control device so that the temperature control device can obtain the temperature control information.

[0050] The pressure control device 104 is used to obtain air pressure control information and control the air pressure in the pyrolysis tank body 101 based on the air pressure control information.

[0051] In the embodiments of the present application, the pressure control device can be connected to the pyrolysis tank body to control the air pressure in the pyrolysis tank body. The present application does not limit the specific manner of obtaining air pressure control information, and the manner of obtaining air pressure control information can be the same as the manner of obtaining temperature control information, which will not be elaborated here.

[0052] The present application does not limit the specific content of the pressure control device. As an example, the pressure control device may include a pressure gauge and an air pump. The pressure gauge can be used to observe the pressure change in the pyrolysis tank body to facilitate pressure adjustment, and the air pump can increase or decrease the pressure in the closed space of the tank body to control the pressure in the pyrolysis tank body.

[0053] The gas detection device 102 is used to detect the pyrolysis gas generated by the heating cable outer sheath and obtain a detection result.

[0054] In the embodiments of the present application, the gas detection device 102 can be connected to the pyrolysis tank body 101 to receive the pyrolysis gas generated by the heating cable outer sheath, thereby detecting the pyrolysis gas. The present application does not limit the specific content of the detection result. The detection result may include the type of gas and the gas concentration.

[0055] The present application does not limit the specific content of the gas detection device. As an example, the gas detection device includes a Fourier transform infrared spectrometer and a gas chromatograph. The detection result of the gas can be accurately obtained through the Fourier transform infrared spectrometer and the gas chromatograph.

[0056] As a possible implementation manner, the gas detection device further includes a computer, and the computer can perform fine processing on the obtained data to better obtain the detection result of the gas.

[0057] Through the above device, accurate control of the pyrolysis time, temperature, and air pressure can be achieved based on the temperature control information and air pressure control information, so as to accurately obtain the detection results of the gases generated by the cable outer sheath under different pyrolysis conditions, providing better data support for the early warning scheme of cable fires.

[0058] As a possible implementation manner, a temperature control device provided in this application includes: a temperature measurement circuit and an arithmetic circuit.

[0059] The temperature measurement circuit is used to measure the first actual temperature value of the heating device.

[0060] In the embodiment of this application, the temperature measurement circuit can be provided with a measurement element to measure the first actual temperature value of the heating device. It can be understood that the first actual temperature value can refer to the working temperature on the surface of the heating device. As an example, the measurement element can include a K-type thermocouple.

[0061] The arithmetic circuit is used to compare the first actual temperature value with the set heating temperature value to obtain a first difference.

[0062] In the embodiment of this application, the first difference can be obtained by calculating the absolute value of the first actual temperature value minus the heating temperature value. The first difference is used to indicate the gap between the actual temperature value of the heating device and the required set heating temperature value.

[0063] The arithmetic circuit is further used to perform an operation based on the first difference according to the proportional-integral-derivative control algorithm to determine an adjustment parameter.

[0064] In the embodiment of this application, after the first difference is determined, the proportional-integral-derivative control algorithm (PID) can be used to perform an operation to determine the adjustment parameter. The specific content of the adjustment parameter is not limited in this application. As an example, the arithmetic circuit includes a solid-state relay, and the heating device includes a heating wire; the adjustment parameters include: the conduction time of the solid-state relay and / or the conduction ratio of the heating wire.

[0065] It can be understood that the heating wire is the heat source of the heating module. As a possible implementation manner, the heat source of the heating device is a nickel-chromium alloy heating wire. This application can accurately simulate the local overheating fault of the cable by passing a low-voltage large current, with the temperature upper limit set at 350 °C, and can effectively simulate the temperature range of 90 - 250 °C. This application can better meet the temperature range requirements of the heating device through the nickel-chromium alloy heating wire, improving the practicality of the device.

[0066] The arithmetic circuit is also used to adjust the output power of the heating module based on the adjustment parameter, so as to heat the cable outer sheath based on the set heating temperature.

[0067] It can be understood that in this application, by adjusting the conduction time of the solid-state relay, that is, by controlling the conduction and cut-off of the solid-state relay, and / or by controlling the conduction ratio of the heating wire, the output power of the heating device can be effectively controlled, and the pyrolysis temperature of the heating module can be accurately controlled to achieve accurate heating.

[0068] In the embodiment of this application, the control principle of the temperature control device can be as Figure 2 shown, Figure 2 This is the control principle diagram of a temperature control device provided by the embodiment of this application. During the experiment, the set temperature, that is, the set heating temperature value recorded above, is set by the experimenter through the buttons on the display panel. This application can also set the heating time through the display panel. The temperature control system uses the E-type thermocouple installed on the surface of the heating device as a measuring element to monitor the working temperature of the heating device in real time. The system compares the set temperature with the real-time working temperature, then performs calculations according to the PID control strategy, and controls the conduction time of the solid-state relay in the original acid circuit by outputting a pulse signal, so as to control the average output power of the heating device in the controlled object and achieve precise control of the temperature of the pyrolysis device.

[0069] As a possible implementation manner, the temperature measurement circuit is also used to obtain a temperature compensation value;

[0070] Based on the temperature compensation value, the first actual temperature value is corrected to obtain a second actual temperature value.

[0071] In the embodiment of this application, the specific manner of obtaining the temperature compensation value is not limited in this application. As an example, this application can pre-establish the correspondence between the measuring element and the temperature compensation value. After determining the measuring element, such as an E-type thermocouple, a K-type thermocouple, etc., the temperature compensation value can be directly determined.

[0072] After this application determines the temperature compensation value, the temperature compensation value can be added to the first actual temperature value to obtain the second actual temperature value.

[0073] The arithmetic circuit is also used to compare the second actual temperature value with the set heating temperature value to obtain a second difference.

[0074] The arithmetic circuit is also used to perform calculations based on the second difference according to the proportional-integral-derivative control algorithm to determine the adjustment parameter.

[0075] The specific method for determining the second difference in this application, and the specific method for determining the adjustment parameter based on the second difference according to the proportional-integral-derivative control algorithm are the same as the method for determining the first difference and the method for performing operations based on the first difference according to the proportional-integral-derivative control algorithm described above, and will not be elaborated here. By obtaining the temperature compensation value to correct the temperature, this application can ensure the accuracy of the measured temperature.

[0076] As a possible implementation, the pyrolysis tank body is of a cylindrical structure, made of ordinary austenitic stainless steel 304, with an inner diameter of 300 mm, a height of 300 mm, and a wall thickness of 3 mm.

[0077] It can be understood that in order to enable the pyrolysis tank body to more accurately simulate the actual fault situation of the cable, it is necessary to conduct research and design on the shape, material, volume, thickness, etc. of the pyrolysis tank body. Based on research and analysis, and based on finite element multi-physical field analysis, the applicant conducts a temperature field simulation study of different temperature gradients inside the proposed pyrolysis tank body, so as to design and determine the relevant parameters such as the shape of the pyrolysis tank body.

[0078] This application takes the pyrolysis of the outer sheath of high-voltage cables as an example for research and analysis. First, a simulation study of the temperature field of the high-voltage cable body is conducted. The applicant establishes a simulation of the temperature field of the high-voltage cable body according to the heat conduction, heat convection, and heat radiation calculation equations and the control equations of fluid mechanics. The general structure of the high-voltage cable from the inside to the outside is generally a copper core conductor, an inner conductor shield layer, a cross-linked polyethylene main insulation layer, an insulation shield layer, a water-blocking buffer layer, a corrugated aluminum sheath, and an outer sheath layer. The structural parameters of the 110KV cable are shown in Table 1 below.

[0079] Table 1 Typical structural parameters of 110kV cables

[0080] Cable Structure Material Thickness (mm) Outer Diameter (mm) Copper Core Conductor Copper - 42.0 Conductor Inner Shield Semiconductor Material 2.0 46.0 Main Insulation Layer XLPE 17.4 80.8 Insulation Shield Semiconductor Material 2.0 84.8 Water Blocking Buffer Layer Polypropylene 4.3 93.4 Corrugated Aluminum Sheath Aluminum 3.8 101.0 Outer Sheath PE 5.3 111.6

[0081] The applicant's research found that the high-voltage cables laid in tunnels are mainly arranged in three ways: up-and-down straight, horizontal triangle, and vertical straight. They are placed at equal intervals above the brackets in the high-voltage cable tunnel. The high-voltage cable tunnel is laid in the soil, and the medium in the tunnel is natural convection air. The simulation of the temperature field of the high-voltage cable body mainly involves the calculation of electromagnetic-thermal coupling. Parameters such as thermal conductivity, constant-pressure heat capacity, and density are used to calculate the heat conduction of the high-voltage cable body. Parameters such as relative permittivity, relative magnetic permeability, and resistivity are used to calculate the electromagnetic heat of the high-voltage cable body. The material parameters of the high-voltage cable body are shown in Table 2.

[0082] Table 2 Material parameter table of the simulation model of the high-voltage cable body

[0083]

[0084] The temperature field of the medium around the high-voltage cable laid in the tunnel mainly involves the calculation of heat-fluid coupling. The soil thermal conductivity, the external ambient temperature, the convective heat transfer coefficient, and the soil temperature are used to calculate the heat conduction of the high-voltage cable laying environment. The tunnel laying environment parameters are shown in Table 3

[0085] Table 3 Tunnel laying environment parameters of high-voltage cables

[0086] Laying Conditions Parameter Value Unit Soil Thermal Conductivity 1 W / (m·K) Ambient Temperature 25 ℃ Convective Heat Transfer Coefficient 10 W / (m2·K) Soil Temperature 20 ℃

[0087] Under the parameter experimental conditions of the above Table 1, Table 2 and Table 3, the applicant carried out simulation calculations on the temperature field of the high-voltage cable body under different arrangement modes. As Figure 3 shown, Figure 3 This is a schematic diagram of the simulation of the temperature field distribution of the high-voltage cable body under different arrangement modes provided by the embodiment of the present application

[0088] Figure 3 (a) shows the temperature field distribution when the temperature of the horizontally arranged conductor is 90°C, Figure 3 (b) shows the temperature field distribution when the temperature of the horizontally arranged conductor is 90°C, Figure 3 (c) shows the temperature field distribution when the temperature of the triangularly arranged conductor is 90°C, Figure 3 (d) shows the temperature field distribution when the temperature of a certain phase conductor of the triangle is 250°C, Figure 3 (e) shows the temperature field distribution when the temperature of the vertically arranged conductor is 90°C, Figure 3 (f) shows the temperature field distribution when the temperature of a certain phase conductor of the vertical arrangement is 250°C. It can be seen that when the horizontal position of the cable is the same, the middle-phase cable reaches the thermal stability limit first. The temperatures transferred from the conductor to the outer sheath under different arrangement modes are also different

[0089] At the same time, the ambient temperature is an important factor affecting the temperature field distribution of the high-voltage cable in the tunnel. In order to study the relationship between the two, when the maximum value of the steady-state temperature field distribution reaches 90°C, the applicant calculated the variation law of the ambient temperature and the maximum temperature of the high-voltage cable in the double-circuit tunnel laying under different arrangement modes, and the results are as Figure 4 shown, Figure 4 This is a schematic diagram of the change curve of the ambient temperature and the maximum temperature of the high-voltage cable provided by the embodiment of the present application

[0090] From Figure 4As can be seen, as the ambient temperature increases, the maximum temperature of the high-voltage cable shows a linear increasing trend. Since the cable generates heat due to losses, there is a temperature difference between the soil area due to heat generation and the outside. When the ambient temperature is higher, the temperature difference between the soil and the external ambient air is smaller, and the convective heat transfer capacity decreases, which is not conducive to the heat dissipation of the system, resulting in an increase in the overall temperature of the high-voltage cable tunnel. When the ambient temperature is between 5 and 25 °C, the maximum temperature of the high-voltage cable in the horizontal arrangement is higher than the other two arrangements. However, when the ambient temperature is between 25 and 35 °C, the maximum temperature of the high-voltage cable in the horizontal arrangement is lower than the other two arrangements. This shows that the temperature fields of different arrangements are greatly affected by the ambient temperature.

[0091] After the temperature field simulation calculation of the cables in the tunnel in this application, the temperature field of the pyrolysis tank will also be simulated to achieve a comparison, so as to determine information such as the structure and material of the pyrolysis tank.

[0092] First, the applicant compares the compressive strengths of different structures, combines the actual working conditions simulated by the pyrolysis tank, considers relevant influences such as wear resistance, easy processing, corrosion resistance, and high temperature resistance, and the characteristic that the viscosity of the PE outer sheath material is high after pyrolysis. The material is selected as ordinary austenitic stainless steel 304 as the base material, and the structure is selected as a cylindrical structure with good pressure-bearing capacity, good heat and mass transfer effect, and short residence time of pyrolysis products. Since the pyrolysis experiment of the PE outer sheath has repeatability, the pyrolysis tank needs to consider disassembly and the convenience of disassembly. In addition, since the pyrolysis tank is enclosed, the airtightness of the pyrolysis tank needs to be ensured. The pyrolysis tank is designed with an open top, and a sealing groove is used in combination with a flexible graphite-clamped metal sealing ring structure, and the seal is achieved through a flange in combination with bolts. This structure is simple, convenient for disassembly and installation, and meets the sealing requirements.

[0093] Combined with the actual engineering situation and considering a certain margin, the maximum air pressure borne by the pyrolysis tank is set to 0.20 MPa. According to the previous experimental results and actual requirements, the volume of the pyrolysis tank is determined to be 20.00 L, the internal diameter is 300.00 mm, and the height is 300.00 mm. The specific dimensions of the pyrolysis tank are designed as follows:

[0094] Under the action of the internal gas pressure of the pyrolysis tank, the wall thickness satisfies S1:

[0095]

[0096] In the formula, S1 is the wall thickness of the pyrolysis tank when bearing the internal pressure; p is the allowable pressure, determined to be 0.30 MPa; the diameter D of the pyrolysis tank is determined to be 0.40 m; C is the additional thickness, determined to be 0.01 m;

[0097] [σ] is the allowable stress of the material, determined to be 82.00.

[0098] When under the action of the external air pressure of the pyrolysis tank body, the wall thickness satisfies S 2 :

[0099]

[0100] In the formula: S 2 is the wall thickness of the pyrolysis tank body when bearing the external pressure; P 0 is the atmospheric pressure, P 0 is 0.10 MPa; the diameter D of the pyrolysis tank body is determined to be 0.40 m; the elastic modulus E of 304 stainless steel is taken as 200.00 GPa.

[0101] Considering that the heat generated during the experiment will cause the air pressure to rise and the corrosion of the decomposition products, it is necessary to reserve a sufficient margin. From the above formulas (1)(2), S 1 = 1.07 mm, S 2 = 2.44 mm. Adding a certain margin, the wall thickness of the pyrolysis tank body is finally determined to be 3.00 mm. For the sealing part, due to the too high temperature, considering the margin and ensuring that the pyrolysis tank body does not deform, the sealing thickness is finally determined to be 10.00 mm.

[0102] During the temperature field simulation process, for the convenience of calculation, the pyrolysis tank body is reasonably simplified, and small structures such as mounting holes, terminal posts, and bolts that have no influence on the results are simplified. The designed pyrolysis tank body is cylindrical, and the designed heating device is located on the central axis of the pyrolysis tank body. The pyrolysis tank body is a typical axisymmetric structure, so the pyrolysis tank body can be simplified into a two-dimensional axisymmetric model. The geometric model of the pyrolysis tank body established is as Figure 5 shown, Figure 5 which is a schematic diagram of the geometric model of a pyrolysis tank body provided by an embodiment of the present application.

[0103] The simulation of the temperature field of the pyrolysis tank body mainly involves the thermal radiation and heat conduction of the heating device to the surrounding environment, as well as the natural convection and thermal radiation between the outer wall of the pyrolysis tank body and the outside air. The outside ambient temperature is set to 25 °C and the internal temperature of the pyrolysis tank body is set to 20 °C. The gas pressure in the sealed tank body is 0.15 MPa, and the air parameters are set to the default values. According to the material properties of stainless steel 304, such as thermal conductivity, density, constant pressure heat capacity, electrical conductivity, etc., they are set and added, as shown in Table 4, and other simulation methods remain unchanged.

[0104] Table 4 Parameter settings of stainless steel 304

[0105]

[0106]

[0107] The applicant conducts a simulation calculation of the temperature field in the pyrolysis tank body under the conditions of Table 4, as Figure 6 .Figure 6 Schematic diagram of the temperature field distribution of a heating device inside a pyrolysis tank body provided in an embodiment of the present application at different surface temperatures. That is, from Figure 6 (a)- Figure 6 (i) respectively show the temperature field distribution of the heating device at surface temperatures of 90°C, 110°C, 130°C, 150°C, 170°C, 190°C, 210°C, 230°C, and 250°C.

[0108] Figure 6 There are pillars with a predetermined height provided at the bottom of the pyrolysis tank body shown in. The heating device is arranged on the pillars. The bottom of the tank refers to the bottom inside the pyrolysis tank body. By heating on the pillars provided on the bottom of the tank, the danger caused by too high temperature at the bottom of the tank wall of the pyrolysis tank body can be effectively avoided.

[0109] From Figure 6 it can be seen that when the surface temperature of the heating device model is 90°C, due to the thermal resistance effect of the air inside the tank, the outer surface temperature of the pyrolysis tank is almost 25°C, which is the same as the outside ambient temperature. From Figure 6 (b), it can be known that when the surface temperature of the heating device model rises from 90°C to 110°C, due to the heat transfer of the heating device model and the convective heat transfer with the air, the outer surface temperature of the pyrolysis tank rises to 37°C. When the temperature of the heating device model rises from 110°C to 230°C all the time, as Figure 6 (b)~6(h) show, the outer surface temperature of the pyrolysis tank gradually rises from 37°C to 55°C. The high-temperature area of the pyrolysis tank body is mainly concentrated around the heating device, and the overall temperature distribution trend is the same.

[0110] The temperature field distribution inside the pyrolysis tank body when the heating device is at 250°C is elaborated in detail. The gas near the pyrolysis failure model forms a continuous upward air flow under the influence of temperature rise, thereby transferring the heat near the heating device layer by layer to the upper half of the pyrolysis tank body, which results in the temperature distribution in the upper part of the pyrolysis tank body being higher than that in the lower part. In addition, the heat of the heating device is transferred to the bottom surface of the pyrolysis tank through the pillars by heat conduction, and the temperature at each height of the pillars decreases as the distance from the heating device increases. From Figure 6 (i), it can be known that only a high temperature is formed in the area near the heating device of the pyrolysis tank body, and the overall temperature inside the pyrolysis tank body does not increase significantly, which successfully forms a local high-temperature effect. In addition, under the action of heat convection, the highest surface temperature of the pyrolysis tank body can reach 50.9°C, which is much lower than the reaction temperature of the internal gas and the pyrolysis tank body, and the decomposition reaction of the pyrolysis tank body will not occur.

[0111] Comparing the temperature field of the above pyrolysis tank body with the temperature field of the cables in the tunnel, it is found that when the core temperature of the high-voltage cable body is 90.0 °C, in the horizontal arrangement, analyzing the temperature field of the outer sheath vertex of the B-phase cable with the highest conductor temperature, the temperature of the outer sheath vertex of the B-phase cable is 88.3 °C. For the temperature field distribution of the pyrolysis tank body heating device at 90.0 °C, the cable outer sheath is 5.3 mm thick, and the temperature at an axial distance of 5.3 mm from the pyrolysis fault model in the pyrolysis tank is 86.5 °C, with a temperature difference of approximately 1.8 °C between the two. In the triangular arrangement, the temperature of the outer sheath vertex of the cable is 88.9 °C, which differs from the corresponding point temperature of the pyrolysis tank body by 2.4 °C. In the vertical arrangement, the temperature of the outer sheath vertex of the cable is 87.7 °C, which differs from the corresponding point temperature of the pyrolysis tank body by 1.2 °C.

[0112] When the core temperature of a certain phase of the high-voltage cable body is 250.0 °C, in the horizontal arrangement, analyzing the temperature field of the outer sheath vertex of the cable with the highest conductor temperature, the temperature of the outer sheath vertex of this phase of the cable is 239.8 °C. For the temperature field distribution of the pyrolysis tank body model at 250.0 °C, the cable outer sheath is 5.3 mm thick, and the temperature at an axial distance of 5.3 mm from the heating device in the pyrolysis tank is 237.6 °C, with a temperature difference of approximately 2.2 °C between the two. In the triangular arrangement, the temperature of the outer sheath vertex of the cable is 238.9 °C, which differs from the corresponding point temperature of the pyrolysis tank body by 1.3 °C. In the vertical arrangement, the temperature of the outer sheath vertex of the cable is 238.7 °C, which differs from the corresponding point temperature of the pyrolysis tank body by 1.1 °C.

[0113] The simulation calculation results of the temperature field of the high-voltage cable body are close to the temperature field of the pyrolysis tank body. The maximum difference is when the core temperature is 90.0 °C, and in the triangular arrangement, the temperature difference between the corresponding points of the high-voltage cable body and the pyrolysis tank body is 2.4 °C. The average error of the overall temperature field is 1.6 °C. This proves the correctness of the finite element simulation calculation results of the high-voltage cable PE outer sheath pyrolysis tank body, indicating that the temperature field of the actual high-voltage cable fault is consistent with the temperature field distribution of the pyrolysis tank body.

[0114] Therefore, according to the simulation results, the material of the pyrolysis tank body is ordinary austenitic stainless steel 304, the volume is determined to be 20.00 L, the inner diameter is 300.00 mm, the height is 300.00 mm, and the wall thickness is 3.00 mm. To meet the requirements of airtightness, pressure corrosion resistance, and high temperature resistance during pyrolysis. The designed pyrolysis tank body through the above analysis and processing can effectively simulate the early latent overheating faults inside the high-voltage cables laid in the tunnel.

[0115] The applicant also verifies whether the designed pyrolysis tank meets the requirements by calculating the heat dissipation power of the pyrolysis tank. The designed pyrolysis tank of this application needs to ensure that the overall temperature inside the pyrolysis tank does not rise during the experiment, and ensure that the heat dissipation power between the pyrolysis tank and the outside air is greater than the heat dissipation power of the heating device inside the pyrolysis tank.

[0116] It can be learned from the data that the specific heat capacity of PE is 2.3 J / (g·°C). If it takes 5 minutes to heat 100 g of the PE of the cable outer sheath from room temperature of 25°C to 250°C, the heat loss Q is:

[0117] Q = cmΔt (3);

[0118] In the formula, Q represents the heat loss, c is the specific heat capacity of the material, m is the mass of the material, and Δt is the temperature difference.

[0119] Considering factors such as heating time and heating device thermal efficiency:

[0120] Q = Ptη (4);

[0121] In the formula, t represents the heating time, η represents the thermal efficiency of the heating device. Under the above conditions, the heat loss Q = 51.75 kJ, t = 5 min, and η = 0.9. From formulas (3) and (4), the power P of the heating device inside the pyrolysis tank is obtained as 192 W.

[0122] The heat dissipation power includes two parts, namely the radiation heat dissipation power and the convective heat dissipation power. The radiation heat dissipation power is based on the Stefan-Boltzmann law:

[0123] Q r = εσST 4 (5);

[0124] In the formula, Q r is the radiation power of the heating device; the surface heat generation rate ε of the heating device takes values from 0 to 1; the Stefan-Boltzmann constant σ takes 5.6697×10-8 W / (m 2 ·K 4 ); S is the surface area of the heating device; T is the absolute temperature scale.

[0125] For the convective heat dissipation power, the qualitative temperature t m is:

[0126]

[0127] In the formula, t s is the surface temperature, t ∞ is the ambient temperature. The natural convection average heat transfer coefficient N um is:

[0128]

[0129] In the formula, V m is the viscosity; g is the acceleration due to gravity; β is the expansion coefficient of the gas; C is the empirical coefficient; M is the non-linear correction factor; P rf is the Prandtl number. According to the gas physical property table, the convective heat dissipation power Q c can be obtained from equations (6) and (7) as follows:

[0130]

[0131] In the formula, λ m is the thermal conductivity of the ambient gas, l represents the characteristic length, and the other parameters are the same as those described above and will not be elaborated here.

[0132] The surface temperature of the heating device is 250 °C, ε = 0.3, and the radiative heat dissipation power Q r1 of the heating device is obtained from equation (5) as 2.97 W. The surface temperature of the heating device is 250 °C, the experimental ambient temperature is 25 °C, C = 0.1, M = 0.333, t m = 373 K, N um = 278.8, and the convective heat dissipation power Qc1 of the heating device is obtained from equation (8) as 29.4 W.

[0133] According to the simulation of the temperature field of the pyrolysis tank body, the surface temperature of the pyrolysis tank body is 50.9 °C. The pyrolysis tank body is approximated as a cylinder, and the surface area S = 0.7065 m 2 , ε = 0.3, the ambient temperature is 25 °C, and the temperature of the pyrolysis tank body is 50.9 °C. The radiative heat dissipation power Q r2 of the pyrolysis tank body is obtained from equation (5) as 116.2 W. According to the surface temperature of the pyrolysis tank body of 50.9 °C, the ambient temperature of 25 °C, t m = 41.3 °C, C = 0.59, M = 0.25, N um = 79.9, and the convective heat dissipation power Q c2 of the pyrolysis tank body is obtained from equation (8) as 36.3 W.

[0134] In summary, at the highest experimental temperature of 250 °C, the heat dissipation power of the pyrolysis tank body is Q r2 + Q c2 = 152.5 W, which is greater than the heat dissipation power Q r1 + Q c1 = 32.37 W of the heating device. This indicates that there will be no overall temperature increase trend inside the pyrolysis tank body, which means that the pyrolysis tank body designed in this application can well meet the heating requirements.

[0135] As a possible implementation, an opening is provided at the top of the pyrolysis tank body 101. The pyrolysis tank body adopts a sealed groove combined with a flexible graphite sandwich metal sealing ring structure, and is sealed by a flange and bolts.

[0136] In the embodiment of the present application, the cable outer sheath to be heated can be taken through the opening provided at the top of the pyrolysis tank body to achieve flexible measurement. Moreover, the pyrolysis tank body is provided with a sealed groove and a sealing ring, and is also provided with a flange and bolt sealing, which can better ensure the sealing performance of the pyrolysis tank body.

[0137] As a possible implementation, a system provided by the present application further includes: a three-way valve and an experimental atmosphere gas device. The first end of the three-way valve is connected to the pyrolysis tank body, the second end of the three-way valve is connected to the gas detection device, and the third end of the three-way valve is connected to the experimental atmosphere gas device.

[0138] The experimental atmosphere gas device is used to input experimental atmosphere gas into the pyrolysis tank body.

[0139] In the embodiment of the present application, the cable outer sheath pyrolysis experiment system further includes a three-way valve, and the three-way valve has three ends. It can be understood that when it is necessary to input experimental atmosphere gas into the pyrolysis tank body, the first end and the third end of the three-way valve can be opened, and the second end of the three-way valve can be closed. When it is necessary to obtain the detection result, the first end and the second end of the three-way valve can be opened, and the third end of the three-way valve can be closed, so that the pyrolysis gas in the pyrolysis tank body is transmitted to the gas detection device through the three-way valve.

[0140] The present application does not limit the specific content of the experimental atmosphere gas. The experimental atmosphere gas can be ordinary air or different gases such as nitrogen. By inputting experimental atmosphere gas into the pyrolysis tank body, the present application can obtain the detection results of the gases generated by the pyrolysis of the cable outer sheath in different experimental atmosphere gas environments.

[0141] See Figure 7 , Figure 7 FIG. is a schematic structural diagram of another cable outer sheath pyrolysis experiment system provided by the present application. The system is composed of a power supply device, a temperature control system, a pyrolysis tank body and a gas detection device. There is a heating physical model in the pyrolysis tank body, and this heating physical model is the heating device described above.

[0142] The power supply device is a switching power supply driven by a 220V AC voltage, providing stable and reliable power support for the experiment.

[0143] The temperature control system can control the output power of the heating physical model to achieve precise control of the heating temperature. Specifically, the temperature control system can include a temperature measurement circuit, a power control circuit, a full-bridge control and output circuit, and a display and button control circuit. The temperature control system can use the 51 series single-chip microcomputer 12C5A60S2 as the main control chip, use the thermocouple as the temperature acquisition element, achieve precise temperature measurement through the temperature compensation circuit, and achieve closed-loop temperature control by controlling the conduction and cut-off of the solid-state relay. The temperature control system mainly collects the feedback information of the output voltage and current through the AD port of the single-chip microcomputer control unit, so as to form a closed-loop control. The digital IO port includes a full-bridge control circuit to control the generation of high-frequency pulses and PWM to control the output voltage.

[0144] The gas detection device can include a collection device, a Fourier transform infrared spectrometer, a gas chromatograph, and a computer. The collection device can include a gas sampling bag, which can perform precise qualitative and quantitative analysis on the pyrolysis gas collected.

[0145] The pyrolysis tank body of the cable outer sheath pyrolysis experiment system can be as Figure 8 shown Figure 8 This is a schematic structural diagram of a pyrolysis tank body provided by an embodiment of the present application. A heating device is arranged inside the pyrolysis tank body. The heating device uses an electric heating wire as the heat source, provides power for the electric heating wire through a power cord, and transmits the measured temperature signal through a signal wire. The top of the pyrolysis tank body is sealed through a flange and a sealing ring. And a pressure gauge is arranged on the top to monitor the air pressure inside the pyrolysis tank body. The maximum pressure-bearing value of the safety valve is 0.2 MPa, which is used to ensure the safety of the experiment. The pyrolysis tank body is of a cylindrical structure, with an inner diameter of 300.00 mm, a height of 300.00 mm, and a wall thickness of 3.00 mm. Pillars are arranged at the bottom of the tank, and the height of the pillars is 106.00 mm.

[0146] As Figure 9 shown Figure 9Schematic diagram of a temperature measurement circuit provided by an embodiment of the present application. This circuit is a temperature measurement system based on the single-chip microcomputer MAX6675, which can accurately measure high temperatures through a thermocouple. The thermocouple is connected to the T+ and T- pins of the MAX6675 for measuring the target temperature. The thermocouple generates a tiny voltage signal during the measurement process, and the MAX6675 will amplify and convert these signals into digital signals. To ensure the accuracy of the measurement, a cold junction compensation circuit is integrated inside the MAX6675, which can automatically compensate for the temperature change of the cold junction of the thermocouple, that is, the temperature change of the connection point, which is the temperature compensation value that can be obtained and used to correct the temperature as described above. The MAX6675 communicates with external devices through the SPI interface. Among them, the K / SCK pin provides a clock signal to synchronize data transmission, the K / CS pin is used as a chip select signal to enable or disable the MAX6675, and the K / SO pin is used to send temperature data. The MAX6675 outputs the temperature data in a 12-bit digital form, with a resolution of up to 0.25 °C. External devices read and process these data through the SPI interface. To ensure the stable operation of the circuit, the 5V power supply powers the MAX6675, and at the same time, capacitors C8 and C9 are used to filter out power supply noise. The accurate measurement of the temperature of the pyrolysis tank can be realized.

[0147] As Figure 10 shown, Figure 10 Schematic diagram of a full-bridge control and output circuit provided by an embodiment of the present application. This circuit controls the switching state of the full-bridge circuit through a Pulse Width Modulation (PWM) signal. The duty cycle of the PWM signal determines the average value of the output voltage or current. After the PWM signal is filtered and conditioned through a resistor network (R7, R8) and capacitors (C3, C4), it is amplified or adjusted by an operational amplifier (LM358) to generate a signal suitable for driving the full-bridge circuit. The conditioned signal drives the full-bridge circuit to control the switching state of the switching devices. The LC2A filter is used to smooth the high-frequency components of the PWM signal and convert it into a stable DC voltage or current. The inductor and capacitor work together to filter out high-frequency noise to ensure the smoothness of the output signal. By adjusting the duty cycle of the PWM signal, the output magnitude can be accurately controlled, and the feedback network (R10, R11) of the operational amplifier may be used to adjust the output characteristics. The power supply voltage range (0.8 - 4.6V) provides the working voltage for the circuit, and capacitor C5 is used for power supply decoupling to ensure the stable operation of the circuit. Through this circuit, the voltage of the heating wire in the heating device can be accurately controlled, thereby accurately controlling the pyrolysis temperature.

[0148] As Figure 11 shown, Figure 11A schematic diagram of a display and button control circuit provided by an embodiment of the present application. The circuit includes two major modules: LCD display drive and button control. The LCD module communicates with the master device through pins such as CS (chip select), RST (reset), RS (register select), SCK (clock), and SDA (data) to achieve the display function. The button part consists of four switches (SW1 - SW4), which are respectively connected to the KEY1 - KEY4 pins for user input. When a button is pressed, the corresponding KEY pin is grounded, and the master device can detect this change and perform corresponding operations. The entire circuit is powered by a 5V power supply, and GND is the ground wire. Through the above circuit structure, the function of the temperature control device can be accurately realized, the voltage of the heating wire in the heating device can be precisely controlled, and thus the pyrolysis temperature can be accurately controlled.

[0149] As a possible implementation, in order to make the pyrolysis tank provided in the present application meet the experimental requirements, the present application will first conduct an empty - load heating experiment on the pyrolysis device for the heating model. In order to verify whether the actual distribution of the thermal field in the pyrolysis tank is consistent with the simulation results of the temperature field of the pyrolysis tank, taking the case of the maximum simulated temperature of 250 °C as an example, the Figure 6 temperature - field simulation data of the pyrolysis tank at 250 °C shown in (i) is converted into the Figure 12 three - dimensional surface graph shown. As Figure 12 shown, Figure 12 is a three - dimensional surface graph corresponding to the temperature - field simulation data of the pyrolysis tank at 250 °C provided by an embodiment of the present application. Figure 12 The three - dimensional coordinates in

[0150] are respectively the distance of the measurement point from the center axis of the tank, the distance of the measurement point from the bottom of the tank, and the temperature of the measurement point. Figure 13 shown.

[0151] As Figure 13 shown, Figure 13 is a schematic diagram of the temperature - field distribution of the pyrolysis tank at the fault temperature of 250 °C provided by an embodiment of the present application. In the range where the distance of the measurement point from the center axis of the tank is 0 - 60 mm, the temperature is stable at 250 °C, and then in the range where the distance of the measurement point from the center axis of the tank is 60 - 140 mm, the temperature gradually decreases. According to Figure 13From the actual measurement results of the temperature distribution of the tank body, it can be seen that within the range of 0 - 60 mm from the center axis of the tank, the temperature is stable at 245 °C, and within the range of 60 - 140 mm, the temperature decreases with the increase of the distance. By comparing the actual measurement results of the temperature distribution of the pyrolysis tank body with the simulation results, it can be seen that the temperature distribution trends of the simulation and the actual measurement are basically the same. There is only an obvious temperature rise around the heating device, and the overall temperature inside the pyrolysis tank body does not increase. The maximum temperature deviation between the actual measurement value and the simulation result is 3.1 °C, and this error is within the allowable range, which shows the accuracy of the simulation analysis results of the pyrolysis tank body and further verifies the reliability of the designed pyrolysis tank body. This also further shows that the cable outer sheath pyrolysis experimental system designed in this application can meet the requirements of local high-temperature effects and can effectively simulate the early latent overheating faults inside the cables laid in tunnels.

[0152] It should be understood that in this application, "at least one (item)" means one or more, and "multiple" means two or more. "And / or" is used to describe the association relationship of associated objects and indicates that there can be three relationships. For example, "A and / or B" can mean: only A exists, only B exists, and both A and B exist at the same time. Among them, A and B can be singular or plural. The character " / " generally means that the associated objects before and after are in an "or" relationship. "At least one (piece) of the following" or its similar expression refers to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, at least one (piece) of a, b, or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0153] It should also be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising a..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the said element.

[0154] In this article, specific examples are used to illustrate the principle and implementation of this application. The description of the above embodiments is only to help understand the method and its core idea of this application. It should be noted that for those of ordinary skill in the art, without departing from the principle of this application, several improvements and modifications can still be made to this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A cable outer sheath pyrolysis experimental system, characterized in that: The system comprises: a pyrolysis tank, a gas detection device, a temperature control device and a pressure control device; a heating device is arranged inside the pyrolysis tank; The temperature control device is used to obtain temperature control information and control the heating device to heat the cable outer sheath based on the temperature control information, wherein the cable outer sheath is placed on the heating device, and the temperature control information includes a set heating time and a set heating temperature value; The pressure control device is used to obtain air pressure control information and control the air pressure in the pyrolysis tank based on the air pressure control information; The gas detection device is used to detect the pyrolysis gas generated by heating the outer sheath of the cable to obtain a detection result.

2. The system according to claim 1, characterized in that The temperature control device comprises: a temperature measurement circuit and an operation circuit; The temperature measurement circuit is used to measure a first actual temperature value of the heating device; The operation circuit is used for comparing the first actual temperature value and the set heating temperature value to obtain a first difference value; The operation circuit is further used to perform operation according to a proportional-integral-differential control algorithm based on the first difference to determine an adjustment parameter; The operation circuit is further used to adjust the output power of the heating module based on the adjustment parameter, so as to heat the cable outer sheath based on the set heating temperature.

3. The device according to claim 2, characterized in that The temperature measurement circuit is also used to obtain a temperature compensation value; Correcting the first actual temperature value based on the temperature compensation value to obtain the second actual temperature value; The operation circuit is further used for comparing the second actual temperature value and the set heating temperature value to obtain a second difference value; The operation circuit is further used to perform operation according to a proportional-integral-differential control algorithm based on the second difference to determine the adjustment parameter.

4. The system according to claim 2, characterized in that The operation circuit includes a solid-state relay, and the heating device includes a heating wire; the adjustment parameters include: the conduction time of the solid-state relay and / or the conduction ratio of the heating wire.

5. The system according to claim 1, characterized in that The pyrolysis tank is a cylindrical structure, made of ordinary austenitic stainless steel 304, with an inner diameter of 300 mm, a height of 300 mm, and a wall thickness of 3 mm.

6. The system according to claim 1, characterized in that An opening is arranged on the top of the pyrolysis tank body. The pyrolysis tank body adopts a sealing groove and a flexible graphite metal sealing ring structure, and sealing is achieved by a flange and bolts.

7. The system according to claim 1, characterized in that The heat source of the heating device is a nickel-chromium alloy heating wire.

8. The system according to claim 1, characterized in that The gas detection device comprises a Fourier infrared spectrometer and a gas chromatograph.

9. The system according to claim 1, characterized in that The tank bottom of the pyrolysis tank is provided with pillars of a predetermined height, and the heating device is arranged on the pillars.

10. The system according to claim 1, characterized in that The system further comprises: a three-way valve and an experimental atmosphere gas device, wherein a first end of the three-way valve is connected to the pyrolysis tank, a second end of the three-way valve is connected to the gas detection device, and a third end of the three-way valve is connected to the experimental atmosphere gas device; The experimental atmosphere gas device is used to input experimental atmosphere gas into the pyrolysis tank.

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