A multi-field coupling non-uniform aging simulation device and method for high-voltage cable insulation material

Abstract

This invention discloses a multi-field coupled non-uniform aging simulation device and method for high-voltage cable insulation materials, comprising an upper vessel and a lower vessel connected by a sample sealing clamping assembly, with the internal spaces of the upper and lower vessels physically isolated from each other. Heating modules are installed in both the upper and lower vessels, each electrically connected to a temperature control module host computer. Both the upper and lower vessels have air inlets and outlets, with the air inlets connected to air source modules, each electrically connected to an atmosphere control host computer. The temperature control module host computer and the atmosphere control host computer are mounted on the outer walls of the upper and lower vessels. This invention, through the dual experimental chamber configuration, simultaneously and independently controls the temperature gradient and oxygen concentration gradient, enabling equivalent simulation of the long-term service characteristics of the insulation layer under various complex temperature conditions and cable structures, thus solving the problem of discrepancies between traditional oven methods and actual failure modes.

Description

Technical Field

[0001] This invention belongs to the field of insulation materials for high-voltage power equipment, and in particular, it relates to a multi-field coupled non-uniform aging simulation device and method for high-voltage cable insulation materials. Background Technology

[0002] In modern power systems, cross-linked polyethylene (XLPE) power cables are widely used in high-voltage and ultra-high-voltage transmission networks due to their excellent electrical, mechanical, and heat resistance properties. During long-term operation, the cable insulation not only withstands high-intensity electrical stress but also faces the combined aging effects of heat, oxygen, and other factors. Changes in its insulation performance directly affect the safe and stable operation of the power system. Existing aging tests for cable insulation materials mainly employ constant-temperature forced-air ovens to conduct accelerated thermo-oxidative aging experiments on standard slices or dumbbell-shaped samples. This traditional method typically sets a uniform temperature and oxygen concentration environment. Under specific experimental conditions at relatively low temperatures, the insulation material undergoes relatively uniform oxidative degradation from the surface inwards. In this case, the oven experiment can effectively simulate the uniform and slow thermal aging process that occurs throughout the cable insulation layer.

[0003] However, the aging behavior of high-voltage cables under actual, complex operating conditions does not perfectly match that in the laboratory. In real-world conditions, high-voltage cables are encased in a metal sheath. Under long-term operation and thermal expansion and contraction cycles, the sealing performance of this sheath is not consistently excellent, and different metal sheath structures exhibit varying degrees of gas barrier effectiveness. The yellowing and discoloration of the insulation layer discovered during actual dissections also confirms that the cable is actually still in a low-oxygen environment containing trace amounts of oxygen.

[0004] Furthermore, the aging of the insulation layer is not always uniform. On the one hand, under normal operating loads, the insulation layer exhibits a uniform aging characteristic with changes in color between both the inner and outer layers. On the other hand, when there are microscopic defects or poor contact at the cable termination leading to localized overheating, the XLPE main insulation layer will show significant non-uniform characteristics. Specifically, the insulation layer near the shielding layer will turn noticeably yellow or even reddish-brown, while the inner portion of the insulation layer will have a lighter aging color. Simultaneously, the semi-conductive shielding layer in areas of significant discoloration often exhibits stickiness, reduced thickness, and even adhesion to the insulation layer that is difficult to peel off.

[0005] While existing conventional thermal aging ovens can meet the simulation requirements for uniform aging, they struggle to construct controllable coupling of multi-gradient fields distributed along the insulation layer thickness. The following problems arise in general: 1. It is impossible to achieve independent control of low oxygen on one side and oxygen deficiency on the other side on the same sample, so it is difficult to reproduce the aging situation of different oxygen concentrations in the cable environment caused by metal armor of different states and structures.

[0006] 2. It is impossible to achieve independent control of high temperature on one side and low temperature on the other side on the same sample, so it is impossible to reproduce the uneven aging phenomenon caused by the temperature gradient between the surface of the cable shield and the internal insulation layer.

[0007] 3. It is difficult to conduct zonal studies on the aging of the shielding layer and the body on the same sample, so it is impossible to accurately distinguish the migration and diffusion of the aging degradation products of the shielding layer material to the insulation layer, and the oxidation of the insulation layer itself.

[0008] Therefore, there is an urgent need for an experimental device that can perform zoned control and gradient simulation of aging conditions in order to optimize traditional aging test conditions. Summary of the Invention

[0009] The purpose of this invention is to provide a multi-field coupled non-uniform aging simulation device and method for high-voltage cable insulation materials, which solves the problem that existing technologies cannot perform zoned control and gradient simulation of aging conditions.

[0010] To achieve the above objectives, the present invention employs the following technical solution: A multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials includes an upper vessel and a lower vessel, which are connected by a sample sealing clamping assembly, and the internal spaces of the upper and lower vessels are physically isolated from each other. Heating modules are installed in both the upper and lower vessel bodies. Each heating module is electrically connected to a temperature control module host computer. Both the upper and lower vessel bodies have air inlets and outlets. The air inlets are connected to air source modules. Each air source module is electrically connected to an atmosphere control host computer. The temperature control module host computer and the atmosphere control host computer are installed on the outer walls of the upper and lower vessel bodies.

[0011] Furthermore, the top of the upper vessel body is connected to the upper vessel cover by flange bolts, and the bottom of the lower vessel body is connected to the lower vessel cover by flange bolts. An upper vessel cover sealing ring is provided between the upper vessel cover and the upper vessel body, and a lower vessel cover sealing ring is provided between the lower vessel cover and the lower vessel body. The upper vessel body, lower vessel body, upper vessel cover, and lower vessel cover are all made of alloy materials that are resistant to high temperature, high pressure, and corrosion.

[0012] Furthermore, the sample sealing clamping assembly includes an upper sample sealing clamping ring and a lower sample sealing clamping ring. A vessel body slot is provided between the upper vessel body and the lower vessel body. Both the upper sample sealing clamping ring and the lower sample sealing clamping ring are installed in the vessel body slot. An outer sealing ring is installed on the outside of the vessel body slot. A miniature vacuum pump is installed at the interlayer interface of the vessel body slot.

[0013] Furthermore, the heating module includes a resistance thermometer wire and a thermocouple wire. The resistance thermometer wire is spirally installed or embedded in the inner sidewalls of the upper and lower vessel bodies, and the thermocouple wire is installed on the upper and lower vessel covers. Both the resistance thermometer wire and the thermocouple wire are electrically connected to the host computer of the temperature control module via high-temperature resistant signal lines.

[0014] Furthermore, the gas source module includes a high-temperature oxygen concentration sensor and a high-pressure nitrogen-oxygen source. The high-temperature oxygen concentration sensor is installed on the inner sidewalls of the upper and lower vessels. The high-pressure nitrogen-oxygen source is connected to the air inlet through a nitrogen-oxygen pipeline. Both the high-temperature oxygen concentration sensor and the high-pressure nitrogen-oxygen source are connected to the atmosphere control host computer.

[0015] Furthermore, a high-pressure nitrogen-oxygen pump, a gas pressurization valve, and a mass flow controller are sequentially installed on the nitrogen-oxygen pipeline. The high-pressure nitrogen-oxygen pump, the gas pressurization valve, and the mass flow controller are all electrically connected to the atmosphere control host computer.

[0016] Furthermore, air holes are provided on the side walls of the upper and lower vessel bodies on the side of the air inlet, and electronic back pressure valves are installed on the air holes. The electronic back pressure valves are electrically connected to the atmosphere control host computer.

[0017] Furthermore, a safety relief valve is installed at the air outlet, and the safety relief valve is electrically connected to the atmosphere control host computer.

[0018] Furthermore, a saddle-shaped adapter block is provided at the bottom of the upper vessel body. The saddle-shaped adapter block can be detachably installed between the upper sample sealing clamping ring and the lower sample sealing clamping ring. The saddle-shaped adapter block is inserted into the vessel body slot, and a clamp is fixedly installed on the outside of the vessel body slot.

[0019] A method for simulating multi-field coupled non-uniform aging of high-voltage cable insulation materials using the aforementioned device, comprising: The test sample or test cable is fixedly installed through the upper sample sealing clamp ring and the lower sample sealing clamp ring to seal the upper and lower reactor bodies; The atmosphere control host computer controls the gas source module to inject gases with different nitrogen-oxygen ratios into the upper and lower reactor bodies. The temperature control host computer controls the heating module to heat the upper and lower reactor bodies at different temperatures, establishing a stable temperature gradient, oxygen concentration gradient and pressure field in the upper and lower reactor bodies. Heat and oxygen diffuse non-uniformly within the upper and lower vessel bodies under pressure. The temperature control module and atmosphere control module adjust the temperature and oxygen concentration in real time and record various parameters during the aging process. After the test, once the upper and lower reactor bodies have cooled and depressurized to a safe range, the test sample or cable is removed, and aging analysis is performed based on the various parameters during the aging process.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials. The upper and lower reactor bodies are connected by a sample sealing clamping assembly, physically isolating their internal spaces. This provides a structural basis for constructing temperature, oxygen concentration, and pressure gradients, solving the core problem of existing devices' inability to create a non-uniform environment. Heating modules are installed in both the upper and lower reactor bodies, each electrically connected to a temperature control module host computer. Both bodies have air inlets and outlets, with the inlets connected to a gas source module, which is electrically connected to an atmosphere control host computer. This enables independent control and coordinated operation of temperature and atmosphere, ensuring precise control of parameters during aging and improving the reliability of test data. The temperature control module host computer and the atmosphere control host computer are mounted on the outer walls of the upper and lower reactor bodies, simplifying the wiring and layout, reducing external environmental interference to the control modules, and improving the device's integration and ease of operation. This invention, through a dual-chamber experimental setup, achieves for the first time a gradient aging simulation of a single sample in a dual-environment laboratory setting. It allows for independently controlled application of temperature and atmosphere to the upper and lower surfaces of the sample, as well as independent control of temperature and oxygen concentration gradients. This decouples the contribution weights of temperature and oxygen to aging, accurately replicating the oxygen permeation and heat conduction process from the outside in during cable operation. It enables equivalent simulation of the long-term service characteristics of insulation layers under various complex temperature conditions and cable structures. It can also be used for the research and development of aging-resistant cable insulation materials and for cable insulation life assessment. In particular, it helps to quantitatively study the catalytic or migration-penetration effects of semiconductive shielding layers on insulation aging under high temperature and pressure, solving the problem of discrepancies between traditional oven methods and actual failure modes.

[0021] Furthermore, the upper vessel cover is connected to the upper vessel body, and the lower vessel cover is connected to the lower vessel body via flange bolts, and is equipped with a special sealing ring, which significantly improves the sealing performance of the chamber. At the same time, the vessel body and vessel cover are made of high-temperature resistant, high-pressure resistant, and corrosion-resistant alloy materials, which are suitable for complex aging conditions such as high pressure, high temperature, and oxidation. This solves the problem of ordinary materials being prone to deformation and corrosion in harsh environments, extends the service life of the device, and can meet the needs of accelerated aging experiments of different intensities.

[0022] Furthermore, the multi-stage sealing structure, consisting of the upper sample sealing clamping ring, the lower sample sealing clamping ring, the outer sealing ring, and the micro vacuum pump, serves two purposes: firstly, the main sealing ring secures the sample and separates the chambers; secondly, the micro vacuum pump extracts gas from the interlayer gaps to create negative pressure, cutting off leakage paths and achieving absolute physical isolation between the upper and lower chambers, ensuring the gradient environment is not disrupted. The vessel body slot provides precise positioning for the sealing clamping assembly, ensuring the sample is installed flat and preventing gas short-circuit leakage due to sample misalignment. This forces gas to permeate only through the sample body, realistically replicating the non-uniform aging process of the insulating material.

[0023] Furthermore, the resistance heating wire adopts a spiral installation or embedded design, closely fitting the inner wall of the vessel to achieve rapid and uniform heating within the chamber, avoiding localized temperature deviations. The thermocouple wire is installed on the vessel lid and extends deep into the center of the chamber, enabling precise temperature acquisition of the core area and improving the accuracy of temperature monitoring. The resistance heating wire, thermocouple wire, and temperature control module host computer are electrically connected via high-temperature resistant signal lines, forming a PID closed-loop control system. This system can provide real-time feedback and adjust the temperature, ensuring that the temperature gradient between the upper and lower chambers remains stable within the set range, thus solving the problems of large temperature fluctuations and difficulty in maintaining the gradient in existing devices.

[0024] Furthermore, a high-temperature resistant oxygen concentration sensor is directly installed on the inner wall of the reactor, enabling real-time monitoring of oxygen concentration changes within the chamber and transmitting the data to the atmosphere control host computer. This allows for dynamic adjustment of the oxygen concentration, ensuring the stability of the oxygen concentration gradient. A high-pressure nitrogen-oxygen source is connected to the inlet via nitrogen-oxygen pipelines, providing oxygen-nitrogen mixtures or single gases in varying proportions to meet the oxygen concentration requirements of different aging scenarios. This broadens the applicability of the device and allows for the simulation of cable aging processes under different environments.

[0025] Furthermore, a high-pressure nitrogen-oxygen pump, a gas pressurization valve, and a mass flow controller connected in series on the nitrogen-oxygen pipeline form a multi-stage control mechanism. This mechanism can precisely control the gas pressure and flow rate, ensuring that the pressure in the chamber remains stable at the set threshold and preventing imbalances in the oxygen concentration gradient caused by pressure fluctuations. All valves and pumps are connected to the atmosphere control system's host computer, enabling automated control of gas proportioning and pressure regulation. This reduces manual intervention, simplifies operation, and improves the repeatability and reliability of the experiment.

[0026] Furthermore, an electronic back pressure valve is installed at the air inlet side, which can adjust the back pressure in the chamber in real time to ensure that the pressure remains stable within the design limits, avoiding equipment damage due to excessive pressure and ensuring the safety of the experimental process. The electronic back pressure valve is connected to the atmosphere control host computer and can dynamically adjust the back pressure according to changes in oxygen concentration and flow rate, ensuring the coordinated stability of the oxygen concentration gradient and pressure field, and improving the consistency of the multi-field coupling environment.

[0027] Furthermore, a safety relief valve is installed at the outlet. When the pressure inside the chamber exceeds the design limit, it automatically releases pressure, forming a double safety guarantee in conjunction with the electronic back pressure valve. This effectively protects core components such as the vessel body and valves, reducing the risk of equipment failure. The safety relief valve is connected to the atmosphere control host computer, which can provide real-time feedback of abnormal pressure signals, allowing operators to promptly detect and handle problems, while avoiding safety hazards caused by untimely manual pressure relief.

[0028] Furthermore, the saddle-shaped adapter block features a detachable design. Its lower surface, with a saddle-shaped concave surface, can accommodate cables of different outer diameters. Combined with a clamp for fixation, it enables in-situ aging testing of actual cables without cutting them, preserving the cable's original structure and resulting in test results that more closely reflect real-world operating conditions. The saddle-shaped adapter block snaps into the vessel body's slot and is locked in place by the clamp, ensuring a tight fit between the device and the cable surface. Combined with the pressure-driven self-tightening effect of the sealing clamp ring, reliable sealing under high-pressure conditions is achieved, solving the problem of difficult sealing in actual in-situ cable testing.

[0029] This invention also provides a multi-field coupled non-uniform aging simulation method for high-voltage cable insulation materials. Through the coordinated control of the atmosphere control host computer and the temperature control module host computer, a stable temperature gradient, oxygen concentration gradient, and pressure field are simultaneously constructed. These three interact to form a multi-field coupled environment. Heat and oxygen diffuse non-uniformly along the sample thickness / cable radial direction under pressure, completely replicating the actual aging characteristics of high-voltage cable insulation layers: "external heat and internal cold, external high oxygen and internal low oxygen." This solves the core defect of existing methods that can only simulate a single uniform environment and cannot reflect the non-uniformity of aging. During the aging process, the temperature control module host computer and the atmosphere control host computer monitor temperature and oxygen concentration changes in real time and make dynamic adjustments to avoid gradient field imbalance caused by environmental fluctuations. This ensures the continuous stability of the multi-field coupled environment, making the aging process always conform to the preset working conditions and improving the reliability of the simulation results. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a longitudinal section view of the structure of the high-voltage cable insulation material multi-field coupling non-uniform aging simulation device of the present invention.

[0032] Figure 2 This is a top view of the multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials according to the present invention.

[0033] Figure 3 This is a top view of the upper (lower) vessel body of the present invention.

[0034] Figure 4 This is a schematic diagram of the device assembly for the in-situ cable testing mode of the present invention.

[0035] Figure 5 This is a cross-sectional view of the saddle-shaped adapter block of the present invention.

[0036] Figure 6 This is a Fourier transform infrared spectrum of Embodiment 1 of the present invention.

[0037] Among them: 1-Flange bolt, 2-Upper vessel cover sealing ring, 3-Upper vessel cover, 4-Safety pressure relief valve, 5-Thermocouple wire, 6-Upper vessel body, 7-Thermocouple wire, 8-High temperature oxygen concentration sensor, 9-Temperature control module host computer, 10-Atmosphere control module host computer, 11-Mass flow controller, 12-Gas pressure reducing valve, 13-High pressure nitrogen and oxygen source, 14-Electronic back pressure valve, 15-Upper sample sealing clamping ring, 16-Sample to be tested, 17-Nitrogen and oxygen pipeline, 18-Outer sealing ring, 19-Miniature vacuum pump, 20-Vessel body slot, 21-Lower sample sealing clamping ring, 22-Cable to be tested, 23-Saddle-shaped adapter block, 24-Clamping hoop. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0039] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0040] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0041] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0042] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0043] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0044] The present invention will now be described in further detail with reference to the accompanying drawings: See Figure 1 This invention provides a multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials. Through a dual-chamber structure and multi-module collaboration, a controllable temperature gradient, oxygen concentration gradient, and pressure field are constructed to achieve non-uniform aging simulation. The device includes a chamber assembly, a sample sealing and clamping assembly, a heating and temperature control unit, an atmosphere and pressure control unit, a saddle-shaped adapter assembly, and a host computer control module.

[0045] The chamber assembly comprises an upper vessel body 6 and a lower vessel body, connected by high-strength bolts to form a vertically distributed reactor structure. The internal spaces are physically isolated, forming two physically isolated independent chambers, with heat transfer and gas micro-permeation achieved solely through the sample body. The upper and lower vessel bodies constitute a high-strength closed reaction chamber, providing the test sample 16 or the test cable 22 with an accelerated aging experimental environment capable of withstanding high-pressure oxidation conditions. Figure 2 As shown, the top of the upper vessel body 6 is connected to the upper vessel cover 3 via flange bolts 1, and the bottom of the lower vessel body is connected to the lower vessel cover via flange bolts 1. Multiple flange bolts 1 apply force evenly along the flange circumference to rigidly lock the vessel cover and vessel body together, ensuring absolute sealing under high-pressure conditions. An upper vessel cover sealing ring 2 is embedded between the upper vessel cover 3 and the upper vessel body 6, and a lower vessel cover sealing ring is embedded between the lower vessel cover and the lower vessel body to prevent gas leakage and ensure chamber sealing performance. The upper vessel body 6, lower vessel body, upper vessel cover 3, and lower vessel cover are all precision-machined from high-temperature, high-pressure, and corrosion-resistant alloy materials, capable of withstanding accelerated aging test environments under high-pressure oxidation conditions. Both the upper vessel body 6 and the lower vessel body have air inlets and outlets on their side walls. The air inlets are used to introduce gases with different nitrogen-oxygen ratios, and the air outlets are used for exhaust and pressure regulation. Figure 3 As shown, the bottom of the upper vessel body 6 and the top of the lower vessel body are respectively provided with vessel body slots 20, which are used to install the sample sealing clamping assembly and achieve mechanical positioning.

[0046] The sample sealing and clamping assembly, as the core sealing component, includes an upper sample sealing and clamping ring 15, a lower sample sealing and clamping ring 21, an outer sealing ring 18, and a miniature vacuum pump 19. Both the upper sample sealing and clamping ring 15 and the lower sample sealing and clamping ring 21 are installed within the vessel body slot 20 to fix the sample and separate the upper and lower chambers. The upper sample sealing and clamping ring 15 and the lower sample sealing and clamping ring 21 employ U-shaped lip seals, made of materials with a thermal expansion coefficient similar to XLPE or specially thermally matched. The U-shaped opening faces the inside of the high-pressure chamber, utilizing the high gas pressure inside the chamber to generate a pressure self-tightening effect, compensating for creep gaps after sample heating, preventing gas short-circuiting and leakage along the sample edge, and forcing gas to permeate only through the sample's interior. The outer sealing ring 18 is made of high-temperature resistant fluororubber O-ring, which forms an isolation space with the upper sample sealing clamping ring 15 and the lower sample sealing clamping ring 21. The space is filled with gas by a miniature vacuum pump 19 installed at the interface between the layers of the vessel body slot 20, forming a negative pressure environment of -0.08 to -0.09 MPa. This environment serves to both adsorb and fix the device, and to cut off and extract any trace amounts of gas that may leak from the vessel body, thus achieving zero leakage to the external environment.

[0047] The heating module includes a resistance thermometer wire 5 and a thermocouple wire 7, which are connected to the host computer 9 of the temperature control module via a high-temperature resistant signal line to form a PID closed-loop temperature control system. The resistance thermometer wire 5 is spirally installed close to the inner sidewalls of the upper and lower vessel bodies 6, or embedded in the vessel structure, serving as the core heat source to achieve rapid and uniform heating of the chamber. Thermocouple wire 7 is installed on the upper and lower vessel covers 3, with a probe extending deep into the geometric center of the chamber for real-time acquisition of chamber temperature data. The host computer 9 of the temperature control module is installed on the outer walls of the upper and lower vessel bodies 6, receives the temperature signal transmitted by the thermocouple wire 7, and controls the heating power of the resistance thermometer wire 5 through PID calculations, maintaining the set temperature in the upper and lower chambers respectively, thereby forming a stable temperature gradient in the sample thickness direction or the cable radial direction.

[0048] The gas source module includes a high-temperature resistant oxygen concentration sensor 8 and a high-pressure nitrogen-oxygen source 13, which, together with the atmosphere control host computer 10, achieve precise regulation and stable maintenance of oxygen concentration and pressure. The high-pressure nitrogen-oxygen source 13 is connected to the air inlets of the upper vessel 6 and the lower vessel via nitrogen-oxygen pipelines 17, providing high-purity oxygen, high-purity nitrogen, or a specific ratio of oxygen-nitrogen mixture. A high-pressure nitrogen-oxygen pump, a gas pressurization valve 12, and a mass flow controller 11 are sequentially installed on the nitrogen-oxygen pipeline 17 to regulate gas pressure and flow. The high-temperature resistant oxygen concentration sensor 8 is installed on the inner sidewall of the upper and lower vessel, with a miniature zirconia probe monitoring the oxygen concentration in the chamber in real time. Air vents are provided on the sidewalls of the upper and lower vessel on the side of the air inlet, and electronic back pressure valves 14 are installed on these vents for precise control of the chamber pressure. Safety pressure relief valves 4 are installed at the air outlets of the upper and lower vessel; they automatically release pressure when the chamber pressure exceeds the design limit to prevent equipment damage. The atmosphere control host computer 10 is installed on the outer wall of the reactor body and is electrically connected to the high-pressure nitrogen and oxygen source 13, the high-pressure nitrogen and oxygen pump, the gas pressurization valve 12, the mass flow controller 11, the high-temperature oxygen concentration sensor 8, the electronic back pressure valve 14, and the safety pressure relief valve 4 to realize the automatic adjustment and monitoring of gas ratio, pressure, and oxygen concentration.

[0049] The saddle-shaped adapter assembly, a key component for in-situ testing of actual cables, is made of high-temperature resistant, high-strength special engineering plastic (polyetheretherketone, PEEK) and is a detachable module. For example... Figure 4 and 5 As shown, the saddle-shaped adapter block 23 is installed between the upper sample sealing clamping ring 15 and the lower sample sealing clamping ring 21, and is positioned within the vessel body slot 20. Its upper surface is a flat surface adapted to the vessel body, connected to the upper vessel body 6 via the sample sealing clamping ring 15. Its lower surface is an arc surface adapted to the cable 22 under test, directly contacting the cable via the specially shaped lower sample sealing clamping ring 21. A clamp 24 is fixedly installed on the outside of the vessel body slot 20, encircling the cable to lock the entire device onto the cable 22 under test. By replacing the saddle-shaped adapter block 23 with different curvatures and the corresponding lower sample sealing clamping ring 21, high-voltage cables 22 with different outer diameters from 110 to 500 kV can be adapted.

[0050] The host computer control module includes a temperature control host computer 9 and an atmosphere control host computer 10. The two work together to achieve real-time monitoring, adjustment, and recording of various parameters during the aging process. The temperature control host computer 9 focuses on establishing and stabilizing the temperature gradient, while the atmosphere control host computer 10 is responsible for the precise control of oxygen concentration and pressure. Both have data storage functions and can completely record key parameters such as temperature, oxygen concentration, and pressure during the aging process.

[0051] Based on the above-mentioned device, this invention provides two methods for simulating multi-field coupled non-uniform aging of high-voltage cable insulation materials, respectively adapted to sheet samples and actual cables. The specific steps are as follows: First method: Gradient simulation experiment for sheet-like samples S1: Sample preparation: Cut a composite sheet sample 16 containing a semi-conductive shielding layer and an insulating layer from the high-voltage cable, or prepare a pure XLPE sheet sample with a shielding layer material.

[0052] S2: Sample loading and sealing: Place the sample 16 to be tested between the upper sample sealing clamping ring 15 and the lower sample sealing clamping ring 21, ensuring that the shielding layer side faces the upper vessel body 6 (high potential energy simulation area) and the insulating layer side faces the lower vessel body (low potential energy simulation area); install the outer sealing ring 18 on the outside of the vessel body slot 20, and rigidly lock the upper vessel body 6 and the lower vessel body with flange bolts 1; start the micro vacuum pump 19 to extract the air gap gas between the outer sealing ring 18 and the upper sample sealing clamping ring 15 and the lower sample sealing clamping ring 21, establish a negative pressure protection barrier of -0.08~-0.09MPa, and complete the airtightness test.

[0053] S3: Gradient Field Construction: The temperature of the upper vessel 6 is set to T_high (first set temperature) and the temperature of the lower vessel is set to T_low (second set temperature, T_low < T_high) by the host computer 9 of the temperature control module. The heating module is started to establish a stable temperature gradient in the sample thickness direction. The gas source module is controlled by the host computer 10 of the atmosphere control to fill the upper vessel 6 with high-purity oxygen or a specific ratio of oxygen-nitrogen mixture, and a first pressure threshold P1 is established by the gas pressurization valve 12, the mass flow controller 11 and the electronic back pressure valve 14. High-purity nitrogen is filled into the lower vessel to maintain normal pressure or slightly positive pressure P2 (P2 < P1) to establish a stable oxygen concentration gradient and pressure gradient in the sample thickness direction.

[0054] S4: Aging test operation: Under the set multi-field coupling gradient environment, heat and oxygen diffuse non-uniformly from the shielding layer side to the insulation layer side under pressure, and continue to run for a predetermined time; during the experiment, thermocouple wire 7 monitors the chamber temperature in real time, and high-temperature oxygen concentration sensor 8 monitors the oxygen concentration in real time. The data is synchronously transmitted to the corresponding temperature control module host computer 9 and atmosphere control host computer 10. Temperature control module host computer 9 and atmosphere control host computer 10 realize the dynamic adjustment of temperature, oxygen concentration and pressure through PID closed-loop control, and record the change curves of various parameters.

[0055] S5: Product Analysis: After the experiment, once the chamber has cooled and depressurized to a safe range, disassemble the device and remove the test sample 16. Use micro-infrared spectroscopy, differential scanning calorimetry or broadband dielectric spectrometry to scan and analyze the carbonyl index, melting behavior or dielectric loss layer by layer along the sample thickness direction, plot the aging degree distribution curve, and complete the non-uniform aging assessment.

[0056] The second method is the in-situ gradient simulation experiment of the cable. S1: Adapter installation: Based on the outer diameter of the cable 22 to be tested, select a saddle-shaped adapter block 23 with matching curvature and a corresponding lower sample sealing clamping ring 21; install and fix the saddle-shaped adapter block 23 in the vessel body slot 20 at the bottom of the upper vessel body 6, and embed the lower sample sealing clamping ring 21 to ensure that the lower surface of the saddle-shaped adapter block 23 fits against the outer diameter of the cable 22 to be tested.

[0057] S2: Sealing Loading: Embed the U-shaped lip seal ring into the inner groove of the saddle-shaped adapter block 23, ensuring that the opening faces inward; fasten the assembled upper vessel body 6 component to the target position of the insulation layer of the cable to be tested 22, and use the clamp 24 to initially fix the device on the cable to be tested 22; start the micro vacuum pump 19 to extract the air in the outer sealing ring 18 to establish negative pressure, and with the help of the pressure self-tightening effect and negative pressure adsorption force, make the saddle-shaped adapter block 23 tightly fit with the surface of the cable to be tested 22 to ensure high pressure airtightness.

[0058] S3: Gradient field construction: High-pressure oxygen is introduced into the upper vessel 6 through the atmosphere control host computer 10, pressurized to the set pressure threshold P, and the upper vessel 6 is heated to the set temperature T_high through the heating module; so that the conductor of the cable under test 22 is kept cold or the current is maintained at a low temperature T_low, and a non-uniform multi-field coupling environment with external heat and internal cold, external high pressure oxygen and internal low oxygen is established in the radial direction of the cable insulation layer.

[0059] S4: Aging test operation: The test runs continuously for a predetermined time under the set gradient field. During this time, the temperature control module host computer 9 and the atmosphere control host computer 10 record the changes in various parameters such as temperature, oxygen concentration, and pressure in real time to ensure the stability of the gradient environment.

[0060] S5: Aging Analysis: After the experiment, the test cable 22 is removed by the disassembly device, and radial layer sampling is performed on the insulation layer. The degree of aging at different radial positions is evaluated by physicochemical analysis, and the actual service life of the cable insulation layer is inferred.

[0061] The technical solution of the present invention will be further described in detail below through specific embodiments: Example 1: In-situ gradient aging simulation of cable body based on saddle-shaped adapter like Figure 4 As shown, this embodiment simulates in-situ localized aging of a 110kV cross-linked polyethylene (XLPE) finished cable in a non-operational state. The experiment aims to reproduce the non-uniform aging process of oxygen permeating from the outside (shielding layer) to the inside (insulation layer) during actual operation of the cable.

[0062] Step 1: Device Installation and Adaptation Select a section with a length of 2 meters and a cross-section of 400 mm. 2 The 110kV XLPE cable is used. Based on the cable's outer diameter, a matching saddle-shaped adapter block 23 is selected. This saddle-shaped adapter block 23 is made of high-temperature resistant PEEK material, and its lower surface curvature closely fits the outer surface of the cable insulation (shielding layer). The upper sample sealing clamping ring 15 is embedded into the vessel slot 20 of the upper vessel body 6, and the lower sample sealing clamping ring 21 and the outer sealing ring 18 are installed at the bottom of the saddle-shaped adapter block 23. A miniature vacuum pump 19 evacuates air from between the layers of the saddle-shaped adapter block 23 through the air extraction port on the outer sealing ring 18, using negative pressure to initially adsorb and position the saddle-shaped adapter block 23 at the predetermined position on the cable. Subsequently, a clamp 24 is used to lock the upper vessel body 6 and the saddle-shaped adapter block 23 onto the cable, ensuring good airtightness.

[0063] Step 2: Construction of a multi-field coupled gradient environment Set the experimental parameters using the host computer control system: (1) Temperature gradient construction: The heating module inside the upper body 6 is controlled to maintain the temperature of the upper surface (shielding layer) of the cable insulation at 135°C; at the same time, the current flowing through the cable conductor is controlled to establish a temperature gradient on the cable from the outside to the inside.

[0064] (2) Construction of oxygen and atmospheric pressure environment: Oxygen-nitrogen mixed gas is introduced into the upper part of the vessel body 6 through the air inlet to simulate an oxygen-rich environment; at this time, the lower surface and interior of the cable are in a normal pressure natural environment.

[0065] Step 3: Aging test and sampling The device was operated continuously for 360 hours under the gradient environment set above. After the experiment, the clamp 24, the saddle-shaped adapter block 23, and the vessel body were removed. A section of cable was cut from the experimental area, and a thin sheet sample with a thickness of 0.5 mm was cut radially to prepare a slice for Fourier transform infrared spectroscopy (FTIR) testing.

[0066] Step 4: Microscopic Physicochemical Property Analysis and Result Verification. The above slices were scanned and analyzed using a micro-infrared spectroscopy system. Special attention was paid to the aging characteristic peak of XLPE material—the carbonyl peak (1720 cm⁻¹). -1 The carbonyl index (CI) is a key indicator characterizing the degree of oxidative aging of materials, and its calculation formula is as follows:

[0067] Among them, A 1720 1720cm -1 The absorbance of the carbonyl absorption peak, A 2020 2020cm -1 The absorbance at the reference peak.

[0068] Experimental results are as follows Figure 6 As shown, Figure 6 The FTIR spectra obtained from different depths of the test cable slice are shown. Curve (A) corresponds to the upper region of the cable insulation layer, i.e., the side directly exposed to the oxygen-rich environment of the upper reactor 6. As can be seen from the figure, at 1720 cm⁻¹... -1 A very strong absorption peak appeared near the wavenumber, indicating that a vigorous oxidation reaction occurred in this region, generating a large number of carbonyl products such as ketones, acids, and esters. Curve (B) corresponds to the lower layer of the cable insulation, that is, the side closer to the conductor and not in direct contact with high-pressure oxygen. This region has an absorption peak at 1720 cm⁻¹. -1 The absorption peak at that point is very weak, close to the level of non-aging.

[0069] Quantitative data analysis: Calculations showed that the carbonyl index of the upper aging region was 1.39, while the carbonyl index of the lower region was only 1.25. This significant difference (△CI=0.14) quantitatively confirms the effectiveness of the device of the present invention. 1. Successfully simulated the phenomenon of more severe aging in the upper layer (the side closer to the shielding layer): Data shows that in the area with higher temperature and direct contact with oxygen, the degree of XLPE molecular chain breakage and oxidation is much higher than in the interior. This is completely consistent with the mechanism of non-uniform aging caused by oxygen permeation from the outside to the inside under actual working conditions.

[0070] 2. Gradient simulation successful: The device successfully created significant aging differences along the insulation thickness of the same cable, verifying the excellent performance of the localized pressurization structure of the saddle-shaped adapter block 23 in isolating oxygen penetration and controlling aging variables. By comparing data from the upper and lower layers, the accelerating factors of temperature and oxygen concentration on insulation life can be accurately assessed.

[0071] 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 multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials, characterized in that, It includes an upper vessel body (6) and a lower vessel body, which are connected by a sample sealing clamping assembly. The internal spaces of the upper vessel body (6) and the lower vessel body are physically isolated from each other. Heating modules are installed in both the upper vessel body (6) and the lower vessel body. The heating modules are electrically connected to the temperature control module host computer (9). The upper vessel body (6) and the lower vessel body are provided with air inlets and air outlets. The air inlets are connected to the air source module. The air source module is electrically connected to the atmosphere control host computer (10). The temperature control module host computer (9) and the atmosphere control host computer (10) are installed on the outer walls of the upper vessel body (6) and the lower vessel body.

2. The multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials according to claim 1, characterized in that, The top of the upper vessel body (6) is connected to the upper vessel cover (3) by flange bolts, and the bottom of the lower vessel body is connected to the lower vessel cover by flange bolts. An upper vessel cover sealing ring (2) is provided between the upper vessel cover (3) and the upper vessel body (6), and a lower vessel cover sealing ring is provided between the lower vessel cover and the lower vessel body. The upper vessel body (6), lower vessel body, upper vessel cover (3), and lower vessel cover are all made of high-temperature resistant, high-pressure resistant, and corrosion-resistant alloy materials.

3. The multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials according to claim 1, characterized in that, The sample sealing clamping assembly includes an upper sample sealing clamping ring (15) and a lower sample sealing clamping ring (22). A vessel body slot (20) is provided between the upper vessel body (6) and the lower vessel body. The upper sample sealing clamping ring (15) and the lower sample sealing clamping ring (21) are both installed in the vessel body slot (20). An outer sealing ring (18) is installed on the outside of the vessel body slot (20). A micro vacuum pump (19) is installed at the interlayer interface of the vessel body slot (20).

4. The multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials according to claim 1, characterized in that, The heating module includes a resistance wire (5) and a thermocouple wire (7). The resistance wire (5) is spirally installed or embedded in the inner side wall of the upper vessel body (6) and the lower vessel body. The thermocouple wire (7) is installed on the upper vessel cover (3) and the lower vessel cover. Both the resistance wire (5) and the thermocouple wire (7) are electrically connected to the host computer (9) of the temperature control module through a high-temperature resistant signal line.

5. The multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials according to claim 1, characterized in that, The gas source module includes a high-temperature oxygen concentration sensor (8) and a high-pressure nitrogen and oxygen source (13). The high-temperature oxygen concentration sensor (8) is installed on the inner side wall of the upper vessel (6) and the lower vessel. The high-pressure nitrogen and oxygen source (13) is connected to the gas inlet through a nitrogen and oxygen pipeline. Both the high-temperature oxygen concentration sensor (8) and the high-pressure nitrogen and oxygen source (13) are electrically connected to the atmosphere control host computer (10).

6. The multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials according to claim 5, characterized in that, A high-pressure nitrogen-oxygen pump, a gas pressurization valve (12), and a mass flow controller (11) are installed sequentially on the nitrogen-oxygen pipeline. The high-pressure nitrogen-oxygen pump, the gas pressurization valve (12), and the mass flow controller (11) are all electrically connected to the atmosphere control host computer (10).

7. The multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials according to claim 1, characterized in that, Air holes are provided on the side walls of the upper vessel body (6) and the lower vessel body on the side of the air inlet. An electronic back pressure valve (14) is installed on the air hole. The electronic back pressure valve (14) is electrically connected to the atmosphere control host computer (10).

8. The multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials according to claim 1, characterized in that, A safety relief valve (4) is installed at the air outlet, and the safety relief valve (4) is electrically connected to the atmosphere control host computer (10).

9. The multi-field coupled non-uniform aging simulation device for high-voltage cable insulation materials according to claim 1, characterized in that, The bottom of the upper vessel body (6) is provided with a saddle-shaped adapter block (23). The saddle-shaped adapter block (23) is detachably installed between the upper sample sealing clamping ring (15) and the lower sample sealing clamping ring (21). The saddle-shaped adapter block (23) is inserted into the vessel body slot (20). A clamp (24) is fixedly installed on the outside of the vessel body slot (20).

10. A method for simulating multi-field coupled non-uniform aging of high-voltage cable insulation materials using the apparatus described in any one of claims 1 to 9, characterized in that, include: The test sample (16) or the test cable (22) is fixedly installed through the upper sample sealing clamping ring (15) and the lower sample sealing clamping ring (21) to seal the upper vessel body (6) and the lower vessel body; The atmosphere control host computer (10) controls the gas source module to inject gases with different nitrogen-oxygen ratios into the upper and lower reactor bodies (6). The temperature control host computer (9) controls the heating module to heat the upper and lower reactor bodies (6) at different temperatures, thereby establishing a stable temperature gradient, oxygen concentration gradient and pressure field in the upper and lower reactor bodies (6). Heat and oxygen diffuse non-uniformly in the upper and lower vessel bodies under pressure. The temperature control module host computer (9) and the atmosphere control host computer (10) adjust the temperature and oxygen concentration in real time and record various parameters during the aging process. After the test is completed, wait for the upper vessel (6) and lower vessel to cool down and depressurize to a safe range, then remove the test sample (16) or the test cable (22) and perform aging analysis based on the parameters during the aging process.

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