Nanocomposite insulation materials, insulated cables and robots for repairing insulation defects

Abstract

This invention relates to insulating materials, specifically to nanocomposite insulating materials, insulated cables, and an insulation defect repair robot. The nanocomposite insulating material comprises core-shell particles with a core and a shell, modified montmorillonite, and cross-linked polyethylene. The insulated cable uses this nanocomposite insulating material as its insulating layer. The insulation defect repair robot can use this material to repair cracks and defects in the insulation layer of the cable. This material can automatically repair cracks under the influence of electric and thermal fields, achieving more than five repeated repairs. During cable operation, it can autonomously repair micro-defects ≤100μm, reducing unplanned power outages by 90% and lowering the total life-cycle failure cost by 60%.

Description

Technical Field

[0001] This invention relates to insulating materials, specifically to nanocomposite insulating materials, insulated cables, and robots for repairing insulation defects. Background Technology

[0002] Insulated cables are the core unit of power transmission systems, and the performance of their insulation layer directly determines the cable's transmission efficiency, safety, stability, and service life. During long-term operation, cable insulation layers are susceptible to factors such as electric fields, temperature, mechanical stress, and environmental corrosion, leading to defects such as electrical treeing, localized cracking, increased dielectric loss, and even breakdown. Statistics show that over 60% of cable faults are caused by insulation failure, resulting not only in large-scale power outages but also potential fires and other safety accidents, causing significant economic losses.

[0003] Currently, cross-linked polyethylene (XLPE) remains the mainstream cable insulation material. While it possesses certain insulation properties, it suffers from three major limitations: First, it is difficult to balance dielectric properties and thermal stability. XLPE has a breakdown field strength of approximately 50 kV / mm and a heat distortion temperature of only 110°C. Under high voltage (≥110 kV) and high load operating conditions, it is prone to accelerated aging due to localized overheating. Second, it lacks self-healing capabilities. Once electrical treeing or microcracks occur, the defects will continue to expand, requiring manual excavation and replacement, resulting in high maintenance costs (accounting for 40% of the cable's total lifespan cost) and long repair cycles (average repair time of 48 hours). Third, it has poor material compatibility. Existing nano-modified XLPE materials (such as nano-SiO2 / XLPE and nano-Al2O3 / XLPE) can improve some performance, but the nanoparticle aggregation rate is as high as 35%, causing the dielectric loss factor (at 1 kHz) to rise above 0.005, and the viscosity to exceed 3000 mPa·s. This makes it unsuitable for the precise conveying requirements of continuous extrusion molding processes and automated repair equipment for cables.

[0004] Furthermore, existing cable defect repair methods largely rely on the traditional "power outage-excavation-section replacement" model, which is not only inefficient but also poses safety risks due to manual operation. Even the few automated repair devices available lack suitable high-performance insulation materials, resulting in cable insulation lifespan recovery to only 60% of the original lifespan after repair. Therefore, developing a nanocomposite insulation material that combines high dielectric properties, repetitive self-healing capabilities, and compatibility with cable manufacturing and automated repair, combined with a matching repair robot, to achieve efficient cable defect management has become an urgent need for the power industry. Summary of the Invention

[0005] The purpose of this invention is to provide an insulated cable based on nanocomposite insulation material and a matching repair robot, which solves the problems of insufficient dielectric thermal stability, lack of self-healing ability, poor adaptability and low repair efficiency of existing cable insulation materials, and achieves long-term protection of cable insulation layer and accurate and rapid repair of defects.

[0006] In a first aspect, the present invention provides a process for preparing a nanocomposite insulating material, comprising:

[0007] Organomontmorillonite, cross-linked polyethylene, and γ-iron oxide nanoparticles were pretreated respectively.

[0008] The pretreated modified γ-iron oxide nanoparticles were added to an ethanol dispersion containing graphene quantum dots, stirred and sonicated, the ethanol was removed by rotary evaporation, and the powder was dried under vacuum to obtain Fe2O3@GQDs core-shell structure powder.

[0009] Cross-linked polyethylene, organomontmorillonite, Fe2O3@GQDs core-shell structure powder, PEG-400, and vinyltriethoxysilane were added to a twin-screw extruder for twin-screw extrusion and pelletized to obtain composite masterbatch.

[0010] The composite masterbatch was mixed with dicumyl peroxide and extruded by a single screw extruder, and then subjected to gamma ray irradiation.

[0011] The irradiated material was kept at 120°C for 2 hours and then cooled to room temperature at a rate of 5°C / h.

[0012] Specifically, in the process of preparing Fe2O3@GQDs core-shell structure powder, the mass ratio of γ-iron oxide nanoparticles to graphene quantum dots was 3:1, and the concentration of the ethanol dispersion of graphene quantum dots was 25 g / L.

[0013] Specifically, the weight ratio of cross-linked polyethylene, organomontmorillonite, Fe2O3@GQDs core-shell structure powder, PEG-400, vinyltriethoxysilane, and dicumyl peroxide is 96.65:0.8:1.5:0.4:0.6:0.05.

[0014] Specifically, the twin-screw extrusion process includes:

[0015] The temperatures of each section of the twin-screw extruder are set as follows: Zone 1 150℃, Zone 2 160℃, Zone 3 170℃, Zone 4 180℃, and Die Head 175℃; Screw speed 80 r / min, vacuum degree 0.09 MPa;

[0016] Pretreated cross-linked polyethylene, pretreated organomontmorillonite, and Fe2O3@GQDs core-shell structure powder are added to the main hopper of a twin-screw extruder to allow the materials to be initially mixed.

[0017] When the pre-mixed material enters the second heating zone of the twin-screw extruder at a temperature of 160°C, PEG-400 is precisely injected at a rate of 0.04 kg / h through the side feeder, and VTMO is injected at a main feed rate of 0.06 kg / h. After melting, shearing, and mixing, the material is extruded from the die head as a strip melt. After water cooling, it is pelletized to obtain composite masterbatch.

[0018] Specifically, the gamma ray irradiation dose is controlled at 10-15 kGy, and the irradiation time is 20-30 min.

[0019] Specifically, the preparation process further includes heating and melting the composite masterbatch and then adding PEG-400, with the amount of PEG-400 added being 12.5% ​​to 25% by weight of the original amount. The viscosity of the composite melt after heating and melting is adjusted by adding PEG-400; for example, if used for injection, the viscosity is adjusted to below 1200 mPa·s, and if used for spraying, the viscosity is adjusted to 1500-1800 mPa·s or below.

[0020] Specifically, the pretreatment steps for organo-montmorillonite include: placing the organo-montmorillonite in a vacuum drying oven and drying it at 80℃ for 12 hours to remove adsorbed moisture; then pulverizing it for 5 minutes using a high-speed pulverizer (10000 r / min) and passing it through a 200-mesh sieve to ensure uniform particle dispersion and avoid agglomeration. The organo-montmorillonite is montmorillonite modified with hexadecyltrimethylammonium bromide, with an interlayer spacing increased to over 5 nm, allowing it to synergistically construct a three-dimensional barrier network with Fe2O3@GQDs.

[0021] Specifically, the pretreatment steps for cross-linked polyethylene include: drying the cross-linked polyethylene particles in a 60°C forced-air drying oven for 8 hours, controlling the moisture content to below 0.05% to prevent the generation of bubbles during melt blending. Cross-linked polyethylene (XLPE) is produced by cross-linking polyethylene with dicumyl peroxide (DCP, 0.05% by mass), thereby improving the mechanical properties of the material.

[0022] Specifically, the pretreatment steps for γ-iron oxide nanoparticles include: taking 1.5 kg of γ-Fe2O3 nanoparticles, dispersing them in 50 L of toluene, and sonicating them for 30 min (power 1000 W, frequency 20 kHz) to form a suspension; adding 45 g of KH-560 (3% of the mass of γ-Fe2O3), and refluxing the reaction in an 80℃ constant temperature water bath for 4 h, during which the stirring speed is maintained at 300 r / min; after the reaction is completed, the modified γ-Fe2O3 is collected by centrifugation (speed 8000 r / min, time 15 min), washed 3 times with toluene, and vacuum dried at 60℃ for 8 h for later use.

[0023] The nano-insulating material provided by this invention has a dual-drive self-healing mechanism, which breaks through the limitations of existing materials that are "single-time repair and dependent on external repair agents". It can automatically repair insulation defects under the dual drive of electric field and temperature, and is adapted to the electric field and temperature environment in cable operation.

[0024] The repair principle of the nano-insulating material provided by this invention is as follows: When electrical tree defects or mechanical microcracks occur in the cable insulation layer, for example, when the crack width is ≤100μm: ① Electric field driven: The electric field (≥8kV / mm) of the cable operation induces the π-π conjugated structure of the GQDs shell to induce the directional rearrangement of XLPE molecular chains, with a migration rate of 1.0μm / s, thereby achieving the closure of the insulation defect; ② Temperature driven: The Joule heating of the electrical tree (80-100℃) triggers the magnetocaloric effect of the Fe2O3 core layer, accelerating the movement of XLPE molecular chain segments and promoting the formation of CO-Fe covalent bonds and hydrogen bonds at the crack, thereby achieving the closure of the insulation defect.

[0025] During the above preparation process, the aggregation rate of Fe2O3@GQDs core-shell structure was observed by TEM. If the aggregation rate exceeded 5%, the ultrasonic time in the ethanol dispersion was increased by 30 min for every 1% increase in aggregation rate.

[0026] During the above preparation process, the melt flow rate of the composite masterbatch after heating and melting should reach more than 8g / 10min; if it is lower than this value, 0.1% PEG-400 should be added for every 1g / 10min decrease.

[0027] In the above preparation process, the degree of crosslinking of the insulating material is controlled by gel content testing (Soxhlet extraction method, toluene as solvent, reflux for 24 hours). If the degree of crosslinking is <75%, for every 5% decrease in the degree of crosslinking, the irradiation dose can be increased by 1 kGy or the post-crosslinking time can be extended by 30 min.

[0028] In a second aspect, the present invention provides a nanocomposite insulating material obtained in the first aspect.

[0029] In a third aspect, the present invention provides a process for preparing an insulated cable, comprising: preparing a composite masterbatch according to the method of the first aspect; mixing the composite masterbatch with dicumyl peroxide and adding it to a single-screw extruder, wherein the extruder temperature settings for each section are: zone 1 165°C, zone 2 175°C, zone 3 185°C, and die head 180°C; the screw speed is 50 r / min, and the melt pressure is controlled at 15 MPa; a copper conductor with a diameter of 10-50 mm passes through the extrusion die at a speed of 2-5 m / min, such that the composite melt uniformly coats the conductor, forming a cable with an insulation layer; subjecting the cable with the insulation layer to gamma irradiation; and after irradiation, keeping the cable at 120°C for 2 h, cooling it to room temperature at a cooling rate of 5°C / h.

[0030] A fourth aspect of this invention provides the application of the nanocomposite insulating material prepared in the first aspect in the detection of insulation defects using an insulation defect repair robot. The insulation defect repair robot includes a detection unit, a repair execution unit, and a control unit. The detection unit includes an electric field distortion detection module, an ultrasonic detection module, an infrared thermography module, an imaging module, and a data acquisition module. The repair execution unit includes an electric field module, a heating module, a micro-volume delivery module, and a UV module. The application includes:

[0031] When the electric field distortion detection module detects a local electric field distortion value ≥0.5kV / m in the device under test, it triggers partial discharge detection and infrared thermal imaging detection.

[0032] If a partial discharge signal of 5pC is detected, the insulation defect area is located based on the discharge signal. If the infrared thermography detects that the temperature of the insulation defect area is 3°C higher than the surrounding area, the insulation defect area is determined to be a partial discharge defect caused by insulation aging. The insulation defect includes electrical tree defects and / or mechanical microcracks.

[0033] The imaging module captures images of the insulation defect area, and the data acquisition module constructs a three-dimensional model of the defect based on the acquired electric field distortion value, the identification of microcracks inside the nanocomposite insulation material, local temperature changes, and the images of the insulation defect area, and generates a defect judgment result.

[0034] The data acquisition module calculates the surface spraying amount and internal injection amount of the nanocomposite insulating material required for the insulation defect area based on the density of the nanocomposite insulating material, the design thickness of the repair layer, and the three-dimensional model of the defect. The material injection amount for electrical tree defects is calculated as 1.2 times the defect volume.

[0035] The heating module preheats the nanocomposite insulating material to 35°C, reducing the material viscosity to below 900 mPa·s;

[0036] The control unit generates a delivery command for the nanocomposite insulating material, the delivery command including a delivery rate of 0.2 mL / min during the surface spraying stage and a delivery rate of 0.1 mL / min during the internal injection stage;

[0037] The micro-delivery module receives the delivery command and injects preheated nanocomposite insulating material into the electrical tree channel of the insulation defect region; and / or sprays preheated nanocomposite insulating material onto the mechanical microcracks of the insulation defect region.

[0038] When the pressure in the insulation defect area is detected to rise from the initial 0.05 MPa to 0.15 MPa, it is determined that the electrical tree channel has been filled and injection is stopped; or when the mechanical microcrack is detected to have formed a 0.5 mm repair layer, injection is stopped.

[0039] The UV module is activated, and a 365nm wavelength, 50W UV light source is used to irradiate the repair area for 40 seconds, allowing the material to initially cure until the insulation resistance reaches 10 ohms. 13 Ω;

[0040] The electric field module is activated to apply a global electric field of 8kV / mm and superimpose a local enhanced electric field of 2kV / mm, so that the total electric field in the defect area reaches 10kV / mm. The heating module is then activated to raise the temperature of the defect area to 90~100℃ and keep it at that temperature for 60 minutes, triggering dual-drive self-repair.

[0041] Furthermore, during the spraying process, the imaging module monitors the spraying range in real time to ensure that the material covers the entire insulation defect area and the thickness deviation is controlled within ±0.05mm.

[0042] Furthermore, during the self-repair process, the robot also monitors the temperature of the defect area in real time through thermocouples and feeds it back to the heating module controller to achieve closed-loop temperature control with a temperature deviation of ±2℃.

[0043] Beneficial effects:

[0044] The nanocomposite insulation material provided by this invention has a breakdown field strength of up to 82kV / mm, a heat distortion temperature of 145℃, and an insulation performance retention rate of 90% after 1000h aging. The cable service life is extended to more than twice that of the original XLPE cable, which can meet the high voltage transmission requirements of 110kV-500kV.

[0045] The nanocomposite insulation material provided by this invention can self-repair using an electric field and / or infrared heating, achieving more than 5 repeated repairs. During cable operation, it can autonomously repair micro-defects ≤100μm, reducing unplanned power outages by 90% and lowering the total life-cycle failure cost by 60%.

[0046] This invention also enables the detection and repair of insulation defect areas by using a robot with the nanocomposite insulation material. The whole process is intelligent, shortening the time by 98% compared to traditional manual repair, and the cable insulation life recovery rate after repair is ≥95%. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0048] Figure 1 The schematic diagram illustrates the dual-repair mechanism of the nanocomposite insulating material provided by this invention.

[0049] Figure 2 The structural block diagram of the insulation defect repair robot provided by the present invention.

[0050] Figure 3 The images show the morphology of electrical tree cracks in the nanocomposite insulating material provided by this invention before and after double repair. Detailed Implementation

[0051] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0052] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0053] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text implies three parallel solutions, such as "A and / or B," but this must be based on the ability of a person skilled in the art to implement the solution. The technical solution may include solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other. If such combinations result in contradictions or are impossible to implement, it should be considered that such combinations of technical solutions do not exist and are not within the scope of protection claimed by this invention.

[0054] Example 1: Preparation of Nanocomposite Insulating Materials

[0055] The nanocomposite insulating material provided by this invention includes core-shell particles having a core layer and a shell layer, modified montmorillonite, and cross-linked polyethylene.

[0056] The core layer is formed by 50-100nm γ-iron oxide nanoparticles, and the shell layer is formed by 2-5nm graphene quantum dots. The core-shell interface is bonded through a silane coupling agent to form the Fe2O3@GQDs core-shell structure.

[0057] Among them, montmorillonite, after being modified with hexadecyltrimethylammonium bromide, has an interlayer spacing of more than 5 nm, and can synergistically construct a three-dimensional barrier network with Fe2O3@GQDs.

[0058] The matrix is ​​cross-linked polyethylene (XLPE), which is cross-linked by a peroxide cross-linking agent to improve the mechanical properties of the material.

[0059] The nanocomposite insulation material provided by this invention features a GQDs shell that reduces the agglomeration rate of Fe2O3 from 35% to below 5%, and an organomontmorillonite three-dimensional network that blocks oxygen and moisture penetration, reducing the permeability coefficient to 60%. These three elements work synergistically to achieve breakthroughs in performance characterized by "high dielectric constant, low dielectric loss, high temperature resistance, and anti-aging properties." Testing shows that this nanocomposite insulation material achieves a breakdown field strength of 82kV / mm, a 64% improvement over pure cross-linked polyethylene and a 22% improvement over existing nano-Fe2O3 / XLPE. Its dielectric loss factor at 1kHz is only 0.0018, a 40% reduction compared to XLPE. The heat distortion temperature is increased to 145℃, a 35℃ increase compared to XLPE. Furthermore, after 1000 hours of thermo-oxidative aging testing, the breakdown field strength retention rate reaches 90% (compared to only 75% for existing materials). The nanocomposite insulation material provided by this invention is suitable for manufacturing insulated cables.

[0060] The preparation process of the nanocomposite insulating material and cable provided by this invention:

[0061] 1. Raw material list

[0062] Table 1

[0063] Raw material name Specifications Cross-linked polyethylene (XLPE) Melt flow index: 2.0 g / 10 min (190℃ / 2.16 kg) <![CDATA[γ-Iron Oxide Nanoparticles (Fe2O3)]]> Particle size 50-100nm, purity ≥99.5% Graphene quantum dots (GQDs) Particle size 2-5 nm, oxygen content 10-15% Organomontmorillonite (OMMT) The original interlayer spacing was 1.2 nm, which was modified by hexadecyltrimethylammonium bromide. Dicumyl peroxide (DCP) Purity ≥ 98%, half-life 1 min (175℃) Polyether plasticizer (PEG-400) Number average molecular weight 380-420, viscosity 110-130 mPa·s (25℃) Vinyltriethoxysilane (VTMO) Purity ≥ 97%, Vinyl content ≥ 30% Silane coupling agent (KH-560) Purity ≥ 98%, epoxy value 0.85-0.95 mol / 100g Toluene, ethanol Analytical grade, moisture content ≤0.1%

[0064] 2. Raw material pretreatment steps

[0065] OMMT pretreatment: The modified OMMT was placed in a vacuum drying oven and dried at 80°C for 12 hours to remove adsorbed moisture; then it was pulverized for 5 minutes by a high-speed pulverizer (10,000 r / min) and passed through a 200-mesh sieve to ensure uniform particle dispersion and avoid agglomeration.

[0066] XLPE pretreatment: Dry XLPE granules in a 60℃ forced-air drying oven for 8 hours, controlling the moisture content to below 0.05% to prevent the generation of bubbles during melt blending.

[0067] Fe2O3 surface modification: 1.5 kg of Fe2O3 nanoparticles were dispersed in 50 L of toluene and ultrasonically treated for 30 min (power 1000 W, frequency 20 kHz) to form a suspension; 45 g of KH-560 (3% of Fe2O3 mass) was added and refluxed in an 80 °C constant temperature water bath for 4 h, during which the stirring speed was maintained at 300 r / min; after the reaction was completed, the modified Fe2O3 was collected by centrifugation (speed 8000 r / min, time 15 min), washed 3 times with toluene, and vacuum dried at 60 °C for 8 h for later use.

[0068] 3. Preparation of Fe2O3@GQDs core-shell particles

[0069] Preparation of GQDs dispersion: Take 0.5 kg of GQDs, add 20 L of anhydrous ethanol, and sonicate for 1 h (power 800 W, frequency 25 kHz) to form a GQDs ethanol dispersion with a concentration of 25 g / L, ensuring no obvious precipitation.

[0070] Core-shell composite structure: 1.5 kg of pretreated modified Fe2O3 was added to an ethanol dispersion of GQDs and stirred at 30 °C for 2 h (stirring speed 500 r / min); then ultrasonically treated for 2 h (power 1200 W, frequency 20 kHz) to allow GQDs to tightly bond with the Fe2O3 surface through π-π conjugation; finally, the ethanol was removed by rotary evaporation (temperature 50 °C, vacuum degree 0.08 MPa) to obtain Fe2O3@GQDs core-shell structure powder, which was then vacuum dried at 60 °C for 6 h for later use.

[0071] 4. Blending composite melt

[0072] Basic component mixing: In the main hopper of a twin-screw extruder (length to diameter ratio 40:1), add 96.65 kg XLPE, 0.8 kg pretreated OMMT, and 1.5 kg Fe2O3@GQDs core-shell structure powder in proportion, and start low-speed feeding (feeding speed 10 kg / h) to allow the materials to be initially mixed.

[0073] Addition of plasticizer and silane crosslinking agent: When the base components enter the second heating zone (temperature 160℃) of the twin-screw extruder, 0.4kg of PEG-400 is precisely injected at a rate of 0.04kg / h through the side feeder, and 0.6kg of VTMO is injected at a main feed rate of 0.06kg / h to ensure uniform dispersion of the additives and avoid excessively high local concentrations.

[0074] Melt blending: Set the temperatures of each section of the twin-screw extruder as follows: Zone 1 150℃, Zone 2 160℃, Zone 3 170℃, Zone 4 180℃, and Die head 175℃; Screw speed 80 r / min, vacuum degree 0.09 MPa (excluding volatiles); After the material is melted, sheared, and mixed, it is extruded into strip-shaped melt from the die head, cooled by water (water temperature 25℃), and then cut into composite masterbatch with a particle size of 3mm×3mm by a pelletizer (speed 300 r / min) for later use.

[0075] 5. Cable insulation layer forming

[0076] Melt extrusion coating: The composite masterbatch and 0.05 kg of DCP (peroxide crosslinking agent) are added to the hopper of a single-screw extruder (model: SJ-65, length-to-diameter ratio 30:1). The temperature settings for each section of the extruder are: Zone 1 165℃, Zone 2 175℃, Zone 3 185℃, and die head 180℃; the screw speed is 50 r / min, and the melt pressure is controlled at 15 MPa; the copper conductor (diameter 10-50 mm, after drawing and annealing) passes through the extrusion die at a speed of 2-5 m / min, and the composite melt is uniformly coated on the outside of the conductor to form an insulation layer with a thickness of 2-5 mm (the thickness is adjusted by the die size and conductor speed, with a deviation of ≤ ±0.1 mm).

[0077] Gamma-ray irradiation crosslinking: The cable covered with insulation is sent into a gamma-ray irradiation device (cobalt-60 source), the irradiation dose is controlled at 10-15 kGy (adjusted according to the cable thickness: 10 kGy for 2 mm insulation layer, 15 kGy for 5 mm insulation layer), and the irradiation time is 20-30 min, so that the XLPE molecular chains form a three-dimensional crosslinking network, which improves the mechanical properties and thermal stability of the insulation layer.

[0078] Post-crosslinking and annealing: The irradiated cable was placed in a hot air circulating oven and held at 120℃ for 2 hours to complete the crosslinking reaction; then cooled to room temperature at a rate of 5℃ / h to eliminate internal stress and prevent insulation layer cracking; finally, a nanocomposite insulated cable was obtained with an insulation layer density of 1.05-1.08 g / cm³. 3 Shore hardness (Type D) 65-70.

[0079] 6. Adjustment of insulation repair materials

[0080] If this material is used for cable defect repair rather than cable body molding, the composite masterbatch needs to undergo secondary processing:

[0081] Masterbatch remelting: Take 10 kg of composite masterbatch, add it to a 10 L reactor, heat it to 170 °C to melt it (stirring speed 200 r / min), keep it at that temperature for 30 min, and ensure that the melt is uniform.

[0082] Viscosity fine-tuning: Add 0.05-0.1 kg of PEG-400 according to the repair scenario requirements (injection or spraying). If used for injection, the viscosity needs to be reduced to below 1200 mPa·s; if used for spraying, the viscosity needs to be reduced to 1500-1800 mPa·s. After stirring for 30 minutes, measure the viscosity using a rotational rheometer (temperature 25℃, shear rate 10 s⁻). 1 After testing the viscosity and confirming that it meets the standard, the material can be loaded into the robot's material storage tank for defect repair.

[0083] Example 2: Oxygen and moisture permeability coefficient test of nanocomposite insulating material particles

[0084] 1. Testing Method

[0085] Sample preparation: The nanocomposite insulating material prepared in Example 1 (without secondary remelting) was used as the experimental group, and pure XLPE was used as control group 1. The materials of the experimental group and control group 1 were respectively made into circular samples with a diameter of 50 mm and a thickness of 2 mm. The edges were polished stepwise with sandpaper (1000 grit → 2000 grit) to ensure that the surface roughness Ra ≤ 0.1 μm and that there were no bubbles or scratches. The samples were vacuum dried at 100℃ for 12 h to remove internal moisture.

[0086] Test equipment and standards: ① Oxygen permeability coefficient test: A differential pressure gas permeameter was used, according to GB / T1038-2000 "Test Method for Gas Permeability of Plastic Films and Sheets - Differential Pressure Method". The test temperature was 23℃±1℃, the upstream oxygen pressure was 0.1MPa±0.005MPa, the downstream vacuum was 0.001MPa±0.0001MPa, and after an equilibration time of 12h, the oxygen permeation within 1h was recorded; ② Moisture permeability coefficient test: A cup-type water vapor transmission rate tester (PERME-W3 / 031, Jinan Langguang) was used, according to GB / T1037-1988 "Test Method for Water Vapor Permeability of Plastic Films and Sheets - Cup Method". The test temperature was 38℃±0.5℃, the relative humidity was 90%±2%, the test time was 24h, and the weight gain of the desiccant in the cup was recorded.

[0087] Oxygen permeability coefficient: P O2 =Q×d / A×t×Δp (unit: cm) 3 •cm / (cm) 2 ・s・Pa))

[0088] Water permeability coefficient: P H2O =Q×d / A×t×Δp H2O (Unit: g・cm / (cm)) 2 ・s・Pa))

[0089] Where Q is the permeability (cm³) 3 (or g), d is the sample thickness (cm), and A is the test area (cm²).2 ), t is the test time (s), Δp is the oxygen pressure difference (Pa), Δp H2O The difference in partial pressure of water vapor (Pa).

[0090] 2. Test Results

[0091] Table 2

[0092] Sample type <![CDATA[P O2 ]]> <![CDATA[P H2O ]]> <![CDATA[P O2 Reduction rate (%) <![CDATA[P H2O Reduction rate (%) Control group 1 8.5 7.2 - - experimental group 3.4 2.9 60.0 59.7 (approximately 60%)

[0093] As shown in Table 2, the oxygen permeability coefficient of the experimental group was reduced by 60% and the moisture permeability coefficient was reduced by about 60% compared with pure XLPE, and its ability to block oxygen and moisture was significantly better than that of pure XLPE material.

[0094] Pure XLPE has linearly arranged molecular chains with relatively large intermolecular gaps, allowing oxygen and water molecules to directly permeate through these "molecular channels." However, in this invention, the organomontmorillonite modified with hexadecyltrimethylammonium bromide increases the interlayer spacing from 1.2 nm to over 5 nm, enabling it to be uniformly dispersed within the XLPE matrix, forming a "three-dimensional layered barrier network." Oxygen and water molecules must navigate through these organomontmorillonite layers, creating a "zigzag path" more than three times longer than that of pure XLPE, significantly increasing the permeation resistance. Simultaneously, the tight interfacial bonding between the Fe2O3@GQDs core-shell structure and the XLPE matrix reduces the permeation channels created by "interfacial voids," further lowering the permeability coefficient.

[0095] Oxygen and moisture are the core factors leading to the oxidative degradation of XLPE. The ternary composite insulation material provided by this invention reduces the permeability coefficient by 60%, which can reduce the oxidative aging rate of the material by more than 50%, providing support for improving the performance of subsequent 1000h thermo-oxidative aging. For directly buried cables, moisture penetration easily leads to "water treeing aging." The low moisture permeability of the ternary composite insulation material provided by this invention can reduce the probability of water treeing defects and extend the service life of the cable to more than twice that of the original XLPE cable.

[0096] Example 3: Breakdown Field Strength Test of Nanocomposite Insulating Materials

[0097] 1. Testing Method

[0098] Sample preparation: The material formed by mixing existing uncoated GQDs nano Fe2O3 with XLPE (Fe2O3 mass ratio 1.5%) and then extruding it by twin screw extrusion was used as control group 2.

[0099] The materials from the experimental group, control group 1, and control group 2 were made into thin sheet samples with a diameter of 20 mm and a thickness of 0.2 mm. The surface was wiped three times with anhydrous ethanol to remove oil stains. The samples were then vacuum dried at 50°C for 8 hours to avoid moisture affecting the breakdown performance.

[0100] Test equipment and standards: A high-voltage breakdown tester (YDQ-50kV, Shanghai High Voltage Research Institute) was used, in accordance with GB / T1408.1-2016 "Test Methods for Electrical Strength of Insulating Materials - Part 1: Tests at Power Frequency". The electrode system consisted of brass flat electrodes (15mm in diameter, with a 2mm chamfered edge to avoid electric field concentration at the edges). The test medium was transformer oil (breakdown field strength ≥70kV / mm, excluding oil breakdown interference). The "stepwise voltage ramping method" was used, with a ramping rate of 1kV / s. The voltage value at sample breakdown was recorded, and the breakdown field strength was calculated (breakdown field strength = breakdown voltage / sample thickness).

[0101] Data processing: Each sample group was tested 10 times. The maximum and minimum values ​​were removed and the average value was taken to ensure data validity.

[0102] 2. Test Results

[0103] Table 3

[0104] Sample type Breakdown field strength (kV / mm) - Single value Average value (kV / mm) Increase compared to control group 1 (%) Increase compared to control group 2 (%) Control group 1 48,50,49,51,52,47,50,48,51,49 49.5 - - Control group 2 58,62,60,61,59,63,60,57,61,59 60.0 21.2 - experimental group 80,83,81,84,82,79,82,81,83,80 82.0 65.7 (approximately 64%) 36.7 (approximately 22%)

[0105] 3. Test Results

[0106] The experimental group achieved a breakdown field strength of 82 kV / mm, which is about 64% higher than that of pure XLPE (49.5 kV / mm) and more than 35% higher than that of existing nano Fe2O3 / XLPE (60 kV / mm), demonstrating significantly better breakdown resistance than the comparison sample.

[0107] The improved breakdown field strength of the nanocomposite insulating material provided by this invention originates from the synergistic effect of Fe2O3@GQDs, organomontmorillonite, and XLPE. In the core-shell structure of Fe2O3@GQDs, the Fe2O3 core layer (dielectric constant ≈ 15) can capture free charges, reducing space charge accumulation. The space charge density is reduced from 100 C / m³ in pure XLPE. 3 Reduced to 30C / m 3 The π-π conjugated structure of the GQDs shell can uniformly disperse the electric field, avoiding local electric field concentration. In the three-dimensional network of organomontmorillonite, the organomontmorillonite sheets (dielectric constant ≈ 8) can block the development path of electrical trees. When electrical trees sprout, the sheet structure can "cut off" the electrical tree channel, delaying the breakdown process. In addition, GQDs inhibit Fe2O3 agglomeration, avoiding "local weak areas" caused by agglomeration, and ensuring consistent overall breakdown resistance of the material.

[0108] The nanocomposite insulation material provided by this invention has a breakdown field strength of 82kV / mm, which can meet the insulation requirements of 110kV-500kV high-voltage cables. Compared with existing nanoFe2O3 / XLPE materials, the insulation layer thickness can be reduced from 3mm to 2mm at the same voltage level, reducing cable weight and cost, and reducing laying difficulty.

[0109] Example 4: Dielectric loss factor test of nanocomposite insulating materials

[0110] 1. Testing Method

[0111] Sample preparation: The materials of the experimental group and control group 1 were respectively made into circular samples with a diameter of 30 mm and a thickness of 1 mm. The surface was polished to a roughness Ra≤0.1 μm by a polishing machine (Metaserv2000). Silver electrodes (diameter of 20 mm and thickness of 100 nm) were deposited on the upper and lower surfaces of the samples using a vacuum evaporation instrument to ensure that the electrodes were tightly bonded to the samples.

[0112] Test equipment and parameters: A precision LCR tester (Agilent E4980A) was used, with a test frequency of 1kHz (typical frequency during cable operation), a test voltage of 1V (to avoid electric field breakdown of the sample), and a test temperature of 25℃±1℃. Before testing, the samples were vacuum dried at 100℃ for 12h to eliminate the influence of moisture on dielectric loss. Each group of samples was tested 5 times, and the average value was taken.

[0113] 2. Test Data

[0114] Table 4

[0115] Sample type Number of tests Dielectric loss factor (at 1 kHz) - single value Average value (tanδ) Reduction in percentage compared to pure XLPE (%) Control group 1 5 0.0030,0.0029,0.0031,0.0030,0.0029 0.0030 - experimental group 5 0.0018,0.0017,0.0019,0.0018,0.0018 0.0018 40.0

[0116] 3. Test Results

[0117] As shown in Table 4, the dielectric loss factor of the experimental group at 1 kHz is only 0.0018, which is 40% lower than that of pure XLPE (0.0030), and the dielectric loss control capability is significantly better than that of pure XLPE.

[0118] Dielectric loss mainly stems from polarization loss and conductivity loss. The dielectric loss of pure XLPE primarily originates from polarization loss caused by molecular chain segment motion. However, the experimental group exhibits high conductivity (≈10⁻⁻⁶) in the GQDs shell. 3 (S / m) can suppress interfacial polarization. GQDs form a conductive transition layer at the Fe2O3 and XLPE interface, reducing interfacial charge accumulation and lowering interfacial polarization loss; organomontmorillonite sheets can restrict the movement of XLPE molecular chain segments (the glass transition temperature increases from -20℃ to -10℃ for pure XLPE), reducing molecular polarization loss; the synergistic effect of both reduces the total dielectric loss by 40%.

[0119] Low dielectric loss can reduce dielectric loss heating during cable operation. Taking a 110kV cable as an example, when the current carrying capacity is 400A, the dielectric loss heating power of the experimental group is reduced by 40% compared with pure XLPE, which can avoid accelerated insulation aging caused by local overheating, and at the same time reduce the energy loss of the cable. It can save about 5000kWh of electricity per kilometer of cable per year.

[0120] Example 5: Thermal Deformation Test of Nanocomposite Insulating Materials

[0121] 1. Testing Method

[0122] Sample preparation: The materials of the experimental group and control group 1 were prepared into standard specimens using an injection molding machine. The specimens were 12.7 mm long × 12.7 mm wide × 6.4 mm high. The injection temperature was 190℃ and the holding pressure was 50 MPa to avoid the formation of bubbles and cracks inside the specimens. The specimens were annealed at 120℃ for 2 hours to eliminate internal stress.

[0123] Test equipment and standards: A heat distortion Vicat softening point temperature tester (XRW-300A, Chengde Testing Machine) was used, according to GB / T1633-2000 "Determination of Vicat softening temperature (VST) of thermoplastic plastics". A load of 50N±0.5N was applied, and the heating rate was 50℃ / h±2℃ / h. The temperature at which the sample deformation reached 1mm was recorded as the heat distortion temperature. Each group of samples was tested 3 times, and the average value was taken.

[0124] 2. Test Data

[0125] Table 5

[0126] Sample type Number of tests Heat distortion temperature (°C) - single value Average value (°C) Improvement compared to pure XLPE (°C) Increase in percentage compared to pure XLPE (%) Control group 1 3 109,110,111 110 - - experimental group 3 134,135,136 135 25 22.7

[0127] 3. Test Results

[0128] As shown in Table 5, the heat distortion temperature of the experimental group reached 135℃, which is 25℃ higher than that of pure XLPE (110℃), representing an increase of 22.7%. The deformation resistance under high temperature conditions is significantly better than that of pure XLPE.

[0129] The heat distortion temperature depends on the rigidity of the material's molecular chains and the strength of the interfacial bonding. Pure XLPE molecular chains have a linear structure and strong segment mobility, resulting in significant deformation at around 110℃. In the experimental group, the Fe2O3@GQDs core-shell structure forms a strong interfacial bond (Si-OC bond) with the XLPE matrix, restricting the sliding of molecular chain segments. The organomontmorillonite sheets, acting as a rigid reinforcing phase, anchor the XLPE molecular chains, further enhancing the overall rigidity of the material.

[0130] Dynamic mechanical analysis (DMA) tests showed that the storage modulus (25℃) of the experimental group reached 2.5GPa, which was 38.9% higher than that of pure XLPE (1.8GPa). The resistance to molecular chain movement increased significantly, ultimately raising the heat distortion temperature to 135℃.

[0131] The nanocomposite insulated cable provided by this invention can maintain an insulation layer temperature of 90-120℃ during high-load operation in summer. Its heat distortion temperature of 135℃ ensures that the insulation layer does not undergo plastic deformation, avoiding uneven insulation thickness and electric field concentration caused by deformation. Therefore, the nanocomposite insulation material provided by this invention can be used for cable laying in high-temperature areas (such as deserts and tropical regions), improving environmental adaptability by more than 30% compared to pure XLPE cables.

[0132] Example 6: 1000h thermo-oxidative aging test of nanocomposite insulating materials

[0133] 1. Testing Method

[0134] Sample preparation: The materials of the experimental group and control group 2 were used to prepare samples for the breakdown field strength test (diameter 20mm × thickness 0.2mm). 20 samples were prepared for each group to ensure sample consistency (thickness deviation ≤ ±0.01mm).

[0135] Aging conditions: A thermo-oxidative aging chamber was used, with the aging temperature set at 135℃±1℃ to simulate the accelerated conditions of long-term cable aging. Compressed air was introduced at a flow rate of 20L / h±2L / h to ensure sufficient oxygen, and the aging time was 1000h. During the aging process, 5 samples were taken out every 200h and cooled for 2h at room temperature (25℃) and relative humidity of 40% to eliminate thermal stress before testing the breakdown field strength.

[0136] Performance Testing and Data Calculation: The breakdown field strength of the aged samples was determined using the "breakdown field strength test" method. The breakdown field strength retention rate was calculated as (average breakdown field strength after aging / average initial breakdown field strength × 100%). Simultaneously, the carbonyl index (1715 cm⁻¹) of the samples was measured using a Fourier transform infrared spectroscopy (FTIR, Nicoleti S50). 1 absorbance at 2020 cm⁻ 1 The ratio of absorbance at different locations characterizes the degree of oxidative degradation.

[0137] 2. Test Data

[0138] Table 6

[0139] Sample type Initial breakdown electric field strength (kV / mm) Breakdown field strength (kV / mm) after 1000h aging Breakdown field strength retention rate (%) Carbonyl index after 1000h aging Control group 2 60.0 45.0 75.0 0.85 experimental group 82.0 73.8 90.0 0.42

[0140] 3. Test Results

[0141] As shown in Table 6, after 1000 hours of thermo-oxidative aging, the breakdown field strength retention rate of the experimental group reached 90%, which was significantly higher than that of the control group 2 (75%). At the same time, the carbonyl index of the experimental group (0.42) was only 49.4% of that of the control group 2 (0.85), and the degree of oxidative degradation was much lower than that of existing materials.

[0142] The core of thermo-oxidative aging is the oxygen-induced chain breakage of XLPE molecules, generating oxidized groups such as carbonyl and hydroxyl groups. The improved anti-aging performance of the experimental group stems from a dual protection mechanism. Firstly, the oxygen barrier effect of the organomontmorillonite reduces the oxygen permeability coefficient by 60%, decreasing the probability of contact between oxygen and XLPE molecules and slowing down the oxidation reaction rate. Secondly, the free radical scavenging effect of Fe2O3@GQDs. The Fe core layer of Fe2O3... 3 ⁺ It can capture hydroxyl radicals (・OH) and alkoxy radicals (・OR) generated in the oxidation reaction. The conjugated structure of the GQDs shell can stabilize free radicals through electron transfer. The two work together to reduce the oxidation degradation rate by more than 50% and significantly reduce the carbonyl index, ultimately ensuring a breakdown field strength retention rate of 90%.

[0143] Therefore, it can be seen that the cable prepared using the nanocomposite insulation material provided by the present invention has a high breakdown field strength retention rate, which means that the material ages slowly and the expected service life can reach more than 40 years, which is 33% longer than the existing nano Fe2O3 / XLPE cable (25-30 years). This further reduces the frequency of cable replacement. Taking a 100km 110kV cable as an example, each reduction in replacement can save about 20 million yuan in costs.

[0144] Example 7: Dual-Drive Self-Healing Performance Test

[0145] 1. Sample preparation for testing (adapting to cable insulation structure)

[0146] Sample specifications: A sample with the same insulation layer as the 110kV cable was prepared, with a Φ20mm copper conductor as the core and a 2mm thick nanocomposite insulation material as prepared in Example 1 as the outer layer. After cross-linking by 15kGy γ-ray irradiation and curing at 120℃ for 2h, an insulated cable with a length of 100mm was made.

[0147] Defect pre-fabrication: Two typical defects (simulating common damage during cable operation) were etched on the insulation surface using a pulsed laser etcher (LPKFProtoLaserU4). Electrical treeing defect: A dendritic crack with a depth of 1.5 mm and a maximum width of 50 μm (laser power 5W, etching rate 0.5 mm / s). Mechanical microcrack: A linear crack with a length of 5 mm, a width of 30 μm, and a depth of 0.8 mm (laser power 3W, etching rate 1 mm / s).

[0148] Sample pretreatment: Dry the sample in a vacuum drying oven at 100℃ for 12 hours to remove internal moisture; wipe the surface with anhydrous ethanol to avoid impurities affecting the repair effect. 2. Test environment setup (recreating cable operating conditions)

[0149] Electric field environment configuration: A high-voltage AC power supply (Spellman SL1000) is used to apply an AC electric field of 10kV / mm to the sample through a brass plate electrode (50mm in diameter, with a chamfered edge of R5mm) (the electric field range of 110kV cable operation is 8-12kV / mm). A 0.1mm thick polytetrafluoroethylene film is placed between the electrode and the sample (to avoid direct contact and damage to the sample).

[0150] Temperature environment control: A constant temperature heating stage (accuracy ±0.5℃) is used to hold the sample and stabilize the temperature of the defect area of ​​the sample at 90℃ (simulating the local overheating temperature of the cable under high load). The temperature of the defect area is monitored in real time by thermocouples (resolution 0.01℃) and fed back to the heating stage controller to achieve closed-loop temperature control.

[0151] Ensuring a safe observation environment: Tests were conducted in a laboratory with a constant temperature of 25℃ and a constant humidity of 40% to avoid dust and humidity affecting the accuracy of observations; an optical platform was set up above the sample to fix a scanning electron microscope (SEM, Zeiss Sigma 300) and an optical microscope (Olympus BX53) to ensure that the observation angle was directly facing the defect area.

[0152] 3. Description of the robot structure for adaptation testing

[0153] The insulation defect repair robot includes a detection unit 10, a repair execution unit 20, and a control unit 30. The detection unit 10 includes an electric field distortion detection module 101, an ultrasonic detection module 102, an infrared thermal imaging module 103, an imaging module 104, and a data acquisition module 105. The repair execution unit 20 includes an electric field module 203, a heating module 204, a micro-volume delivery module 201, and a UV module 202.

[0154] (1) Detection unit

[0155] The electric field distortion detection module 101 is used to detect the electric field distortion value before and after repair with the nanocomposite insulation material. The ultrasonic detection module 102 is used to identify microcracks inside the nanocomposite insulation material. The infrared thermography module 103 is used to detect local temperature changes during the repair process using the nanocomposite insulation material. The imaging module 104 is used to capture images of the insulation defect area.

[0156] Electric field distortion refers to the deviation between the actual electric field strength in a defective area and the normal operating electric field strength when defects (such as electrical treeing, mechanical micro-cracks, or localized aging) occur in the cable insulation layer. Simply put, it is the difference between the electric field in the defective area and the electric field in the normal area, measured in units consistent with electric field strength (commonly V / m or kV / m). The core significance of determining or detecting electric field distortion lies in the fact that the essence of insulation defects is the disruption of the homogeneity of the insulating medium (e.g., the medium changes from insulating material to air at the crack, and air has a much lower dielectric constant than insulating material). This disruption of homogeneity causes the electric field to "concentrate" or "distort" at the defect location, resulting in distortion. Therefore, electric field distortion is a key indicator for determining whether latent defects exist in the insulation layer. When the distortion value reaches a certain threshold, it means that the defect has developed to the point where it may affect the safe operation of the cable, requiring further detection (such as partial discharge or infrared thermography) for confirmation.

[0157] The data acquisition module 105 is electrically connected to the electric field distortion detection module 101, the ultrasonic detection module 102, the infrared thermal imaging module 103, and the imaging module 104. The data acquisition module 105 generates three-dimensional coordinates of the insulation defect area and defect judgment results based on the acquired electric field distortion values, identification of microcracks inside the nanocomposite insulation material, local temperature changes, and images of the insulation defect area. This data is then transmitted to the control unit 20 via optical fiber. The data acquisition module 105 also integrates a time synchronizer, which associates and stores electric field sensor data, temperature data, ultrasonic detection data, insulation defect area images, and robot transport operation commands. These commands include parameters such as transport rate and curing parameters, facilitating subsequent analysis of the correspondence between self-repair and operation parameters.

[0158] (2) Repair execution unit

[0159] The micro-volume delivery module 201 includes a twin-screw precision delivery pump, a spray gun, and an injection needle. The spray gun and injection needle are connected to the twin-screw precision delivery pump. The twin-screw precision delivery pump has a screw diameter of 3mm, a pitch of 1mm, and a minimum delivery volume of 0.001mL, suitable for micro-filling requirements of micro-cracks (30-50μm). A pressure sensor (accuracy ±0.001MPa) is installed at the end of the delivery line to monitor the injection pressure in real time and prevent excessive pressure from damaging the sample. The spray gun is used to spray the nanocomposite insulating material onto the surface of the insulation defect area. The injection needle is used to inject the nanocomposite insulating material into the insulation defect area.

[0160] UV module 202 is used to irradiate the sprayed or injected nanocomposite insulating material, causing initial curing of the material. While the injected material (such as electrical tree channels) may not be completely penetrated by UV light, the UV light can act on the material at the defect entry point and within the shallow channels, causing initial curing (insulation resistance up to 10 ohms). 13Ω), forming a sealing barrier to prevent the deep uncured material from flowing outward under subsequent heating (90-100℃) or electric field, ensuring that the deep material remains inside the defect.

[0161] The electric field module 203 is used to generate an electric field in the insulation defect area. Specifically, a micro electric field enhancer (composed of two sets of ring electrodes, 15mm in diameter) is integrated at the front end of the repair actuator. It can superimpose a local electric field in the insulation defect area (the enhancement amplitude is adjustable from 0-5kV / mm). With the help of an external high-voltage power supply, it can realize a dual electric field environment of global electric field and local enhanced electric field, which meets the requirement of electric field threshold ≥5kV / mm for dual-drive self-repair.

[0162] The heating module 204 is used to heat the insulation defect area. Specifically, the heating module 204 consists of an annular heating coil and a point heating head. The annular heating coil is a heating metal body with a diameter of 30mm and a power of 80W, used for overall temperature rise of the defect area, with temperature control between 50-100℃. The point heating head is a cylindrical heating body with a diameter of 5mm and a power of 20W. Its position is finely adjusted by a robotic arm to precisely heat the crack tip, with a temperature deviation of ±2℃, triggering the Fe2O3 core-layer magnetocaloric effect.

[0163] (3) Control unit

[0164] The control unit 30 has a built-in "dual-drive self-healing test" program, which can preset parameters such as electric field strength (5-15kV / mm), temperature (60-120℃), and repair time (0-120min), and supports timed trigger detection and observation commands (such as automatically starting SEM shooting every 5min).

[0165] Data visualization interface: The touch screen adds a "self-healing dynamic curve" display function, which plots the changes in crack width, electric field intensity, and temperature over time in real time, making it easier for testers to intuitively judge the self-healing process;

[0166] Emergency protection procedure: When the electric field sensor detects a value exceeding 15kV / mm (to prevent material breakdown), the temperature exceeds 120℃ (to prevent material degradation), or the injection pressure exceeds 0.2MPa (to prevent sample damage), the shutdown command is automatically triggered, cutting off the high-voltage power supply and material delivery.

[0167] 4. Robot adaptation to testing scenarios

[0168] Robot positioning: Fix the insulation defect repair robot next to the optical platform, adjust the position of the moving unit track to make the axis of the repair actuator coaxial with the defect area of ​​the sample (deviation ≤0.1mm); capture the sample marking points through the robot vision positioning system (4K camera) (positioning stickers are pasted on both ends of the sample in advance) to complete the initial positioning (positioning accuracy ±0.5mm).

[0169] Detection unit calibration: The robot electric field sensor (EFS-01) is placed close to the sample surface (1mm away) to calibrate the electric field detection accuracy—compare the output electric field of the high voltage power supply (10kV / mm) with the sensor detection value (error must be ≤5%); the ultrasonic probe (10MHz) is coupled with special silicone oil and then attached to the defect area to pre-scan the three-dimensional coordinates of the defect and store them in the control unit database;

[0170] Material preparation: Inject nanocomposite insulating repair material (viscosity 1200mPa・s, 25℃) into the robot material storage tank (500mL), start the tank heating jacket to preheat the material to 35℃ (viscosity reduced to 900mPa・s), run the screw pump unloaded for 30s to remove air bubbles in the pipeline and ensure smooth delivery.

[0171] 5. The robot performs a self-repair operation.

[0172] (1) Self-repair operation of electrical tree defects

[0173] Step 1: Defect Location and Parameter Setting

[0174] The robot activates the ultrasonic detection module to scan the three-dimensional coordinates of the electrical tree defect (depth 1.5mm, maximum width 50μm). The control unit automatically matches the self-healing parameters: electric field strength 10kV / mm (global electric field 8kV / mm + local enhanced electric field 2kV / mm), temperature 90℃, material injection volume 0.3mL (calculated based on 1.2 times the defect volume), and UV curing time 40s.

[0175] The robot adjusts the posture of the repair actuator: the injection needle (0.8mm in diameter) is aligned with the entrance of the electrical tree defect, the needle position is finely adjusted by visual positioning (deviation ≤0.1mm), the annular heating ring is placed around the defect area, and the point heating head is aligned with the crack tip.

[0176] Step 2: Building a Dual-Drive Environment

[0177] The control unit issues the following commands: the high-voltage power supply is activated, applying a global electric field of 8kV / mm; the robot electric field enhancer is activated, superimposing a local electric field of 2kV / mm to ensure that the total electric field in the defect area reaches 10kV / mm; at the same time, the annular heating coil and the point heating head are activated to raise the temperature of the defect area to 90℃ (thermocouple feedback temperature control, heating rate 5℃ / min), and hold the temperature for 5 minutes to stabilize the temperature.

[0178] Step 3: Material Injection and Self-Healing Trigger

[0179] The screw pump injects material at a rate of 0.1 mL / min. When the injection pressure increases from the initial 0.05 MPa to 0.15 MPa (based on pressure sensor feedback), it is determined that the electrical tree channel is filled and the injection is stopped (actual injection volume: 0.32 mL).

[0180] The UV module (365nm, 50W) was activated and irradiated for 40 seconds, resulting in initial curing of the material (insulation resistance reaching 10). 13 (Ω); then the UV light source was turned off, and the electric field and temperature environment were maintained to trigger dual-drive self-repair. The electric field induced the GQDs shell to promote the rearrangement of XLPE molecular chains, and the temperature triggered the magnetocaloric effect of the Fe2O3 core to accelerate molecular motion, and the self-repair continued for 60 min.

[0181] (2) Self-healing operation of mechanical microcracks

[0182] Step 1: Defect Location and Parameter Setting

[0183] Robotic ultrasonic testing of mechanical microcracks (5mm in length, 30μm in width, and 0.8mm in depth). Control unit matching parameters: electric field strength 8kV / mm (global electric field only, no local reinforcement required), temperature 100℃, material spraying amount 0.2mL (covering the crack and the surrounding 2mm area), UV curing time 30s;

[0184] The robot switches to spraying mode, adjusts the spray gun angle to 45°, keeps it 5mm away from the defect surface, and covers the cracked area with a ring heating coil.

[0185] Step 2: Building a Dual-Drive Environment

[0186] A global electric field of 8kV / mm is applied by a high-voltage power supply, and the annular heating coil is activated to raise the temperature of the defect area to 100℃ (heating rate 5℃ / min) and hold it at that temperature for 5min. At this time, due to the increase in temperature, the magnetocaloric effect of the Fe2O3 core layer at the crack tip is enhanced, laying the foundation for temperature-driven self-healing.

[0187] Step 3: Material spraying and self-healing triggering

[0188] The screw pump delivers material at a rate of 0.2 mL / min. The spray gun is started and moves at a constant speed (5 mm / min) along the crack length to ensure that the material evenly covers the crack area (thickness 0.5 mm).

[0189] After UV curing for 30 seconds, the UV light source is turned off, and the electric field and temperature environment are maintained for 60 minutes. The temperature drives the rapid movement of XLPE molecular chains, and the electric field assists in directional migration, thereby achieving crack closure.

[0190] 6. Electrical performance verification (core insulation index testing)

[0191] A high-voltage breakdown tester was used to take a sample from the repair area, with a diameter of 10 mm and a thickness of 2 mm, and to test the breakdown field strength.

[0192] Before the electrical tree defect was repaired, the material's breakdown electric field strength was 45 kV / mm, a 45% reduction due to the defect. After repair, the material's breakdown electric field strength was 78 kV / mm, a recovery rate of 95%, close to the original material's 82 kV / mm. Using the same material from control group 2, the breakdown electric field strength before repair was 39 kV / mm, and after repair, it was 41 kV / mm, indicating almost no repair.

[0193] Before mechanical microcrack repair, the material's breakdown field strength was 52 kV / mm, a decrease of 36%. After repair, the material's breakdown field strength was 80 kV / mm, with a recovery rate of 97%. Using the same material as control group 2, the breakdown field strength before mechanical microcrack repair was 38.4 kV / mm, and the field strength after repair was 39 kV / mm, indicating almost no repair.

[0194] The dielectric loss factor at 1 kHz was measured using a precision LCR meter. Before repair, the dielectric loss in the electrical tree defect area was 0.005, which increased by 178% due to the defect. After repair, it decreased to 0.0021, with a deviation of ≤17% from the original material's 0.0018. In the mechanical microcrack area, the dielectric loss decreased from 0.004 to 0.002 before and after repair, with a deviation of ≤11%.

[0195] 7. Mechanical property verification (interfacial bonding and material strength)

[0196] Interface bonding strength test: The bonding strength between the repair layer and the substrate was tested by using a universal testing machine (Instron5969) and a "90° peel test": the bonding strength after repairing electrical tree defects was 4.5MPa, and the bonding strength after repairing mechanical microcracks was 4.8MPa, both of which meet the design requirements (≥4MPa).

[0197] Tensile strength test: Samples were taken from the repaired area (standard tensile specimen, 25mm long, 4mm wide, and 2mm thick) and the tensile strength was tested: the tensile strength before repair was 20MPa (reduced by 20%) due to the defect, and after repair it was restored to 24MPa (close to the original material's 25MPa, with a recovery rate of 96%).

[0198] 8. Long-term effectiveness verification (simulating long-term operation)

[0199] Accelerated aging test: The repaired sample was placed in a thermo-oxidative aging chamber (135℃, compressed air flow rate 20L / h) and aged for 1000h. The breakdown field strength was tested: the breakdown field strength of the electrical tree defect repair area was 75kV / mm (retention rate 96%), and the breakdown field strength of the mechanical microcrack repair area was 78kV / mm (retention rate 98%), both of which are higher than the retention rate of existing materials after aging (75%).

[0200] Cyclic self-healing test: The pre-crack-repair operation was repeated 5 times in the same defect area. The breakdown field strength recovery rate was ≥90% after each repair, which proved that the dual-drive self-healing mechanism has repeatability and no repair capacity decay.

[0201] Therefore, the nanocomposite insulating material provided by this invention can repair 50μm wide electrical tree defects and 30μm wide mechanical microcracks to below 5μm within 60 minutes under the dual driving conditions of a 10kV / mm electric field and a 90℃ temperature, with a repair efficiency of ≥90%. The electrical properties (breakdown field strength recovery rate ≥95%, dielectric loss ≤0.0021) and mechanical properties (bonding strength ≥4.5MPa, tensile strength recovery rate ≥96%) of the repaired material are close to the level of the original material.

[0202] Long-term performance tests have demonstrated that the nanocomposite insulation material provided by this invention has the ability to repeatedly self-repair, and its performance retention rate after aging is significantly better than that of existing materials. The precise control of the robot provides key support for the efficient performance of the dual-drive self-repair mechanism. The two work together to meet the long-term repair needs of high-voltage cable insulation defects.

[0203] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A process for the preparation of a nanocomposite insulating material, characterized in that, Comprising: The organic montmorillonite, crosslinked polyethylene and γ-iron oxide nanoparticles are pretreated respectively; the organic montmorillonite is montmorillonite modified by hexadecyl trimethyl ammonium bromide, and the interlayer spacing is expanded to 5 nm or more, which can be used to construct a three-dimensional barrier network with Fe2O3@GQDs; The pretreated modified γ-iron oxide nanoparticles are added into the ethanol dispersion liquid containing graphene quantum dots, stirred and ultrasonically treated, ethanol is removed by rotary evaporation, and vacuum drying is performed to obtain Fe2O3@GQDs core-shell structure powder; The crosslinked polyethylene, organic montmorillonite, Fe2O3@GQDs core-shell structure powder, PEG-400 and vinyl triethoxy silane are added into a double screw extruder for double screw extrusion, and pelletization is performed to obtain a composite master batch; After the composite master batch is mixed with dicumyl peroxide and then single screw extruded, γ-ray irradiation is performed; After the irradiated material is kept at 120 DEG C for 2 h and then cooled to room temperature at a cooling rate of 5 DEG C / h.

2. The manufacturing process according to claim 1, characterized in that, During the preparation of the Fe2O3@GQDs core-shell structure powder, the mass ratio of γ-iron oxide nanoparticles to graphene quantum dots is 3:1, and the concentration of the ethanol dispersion liquid of graphene quantum dots is 25 g / L.

3. The manufacturing process of claim 1, wherein, The crosslinked polyethylene, organic montmorillonite, Fe2O3@GQDs core-shell structure powder, PEG-400, vinyl triethoxy silane and dicumyl peroxide are added in a weight ratio of 96.65:0.8:1.5:0.4:0.6:0.

05.

4. The manufacturing process of claim 1, wherein, The process of double screw extrusion comprises: The temperature of each section of the double screw extruder is set as follows: zone 1, 150 DEG C; zone 2, 160 DEG C; zone 3, 170 DEG C; zone 4, 180 DEG C; and the die head, 175 DEG C; the screw rotation speed is 80 r / min, and the vacuum degree is 0.09 MPa; The pretreated crosslinked polyethylene, pretreated organic montmorillonite and Fe2O3@GQDs core-shell structure powder are added into the main hopper of the double screw extruder to preliminarily mix the materials; When the preliminarily mixed materials enter the second heating zone of the double screw extruder, i.e., the temperature is 160 DEG C, PEG-400 is precisely injected at a speed of 0.04 kg / h through a side feeding device, and vinyl triethoxy silane is injected at a main material feeding speed of 0.06 kg / h, the materials are melted, sheared and mixed, and then extruded from the die head in the form of a strip, cooled in water and pelletized to obtain a composite master batch.

5. The manufacturing process of claim 1, wherein, The γ-ray irradiation dose is controlled at 10-15 kGy, and the irradiation time is 20-30 min.

6. The manufacturing process of claim 1, wherein, Further comprising: After the composite master batch is heated and melted, PEG-400 is added, and the amount of PEG-400 added is 12.5-25% of the original amount.

7. The nanocomposite insulating material prepared by the process according to any one of claims 1-6.

8. A process for the production of an insulated electrical cable, characterized in that, Comprising: The organic montmorillonite, crosslinked polyethylene and γ-iron oxide nanoparticles are pretreated respectively; The pretreated modified γ-iron oxide nanoparticles are added into the ethanol dispersion liquid containing graphene quantum dots, stirred and ultrasonically treated, ethanol is removed by rotary evaporation, and vacuum drying is performed to obtain Fe2O3@GQDs core-shell structure powder; The cross-linked polyethylene, organic montmorillonite, Fe2O3@GQDs core-shell structure powder, PEG-400 and vinyl triethoxysilane are added into a double screw extruder for double screw extrusion, and pelletization is carried out to obtain a composite master batch; The composite master batch is mixed with dicumyl peroxide and added into a single screw extruder, and the temperature of each section of the extruder is set as follows: 165 DEG C in the first section, 175 DEG C in the second section, 185 DEG C in the third section, and 180 DEG C in the head; the screw rotation speed is 50 r / min, the melt pressure is controlled at 15 MPa; a 10-50 mm diameter copper conductor is passed through the extrusion die at a speed of 2-5 m / min, so that the composite melt is uniformly coated on the conductor to form a cable with a wrapping insulation layer; The cable with the wrapping insulation layer is subjected to gamma ray irradiation; After the irradiation, the cable is kept at 120 DEG C for 2 h and then cooled to room temperature at a cooling rate of 5 DEG C / h.

9. The use of the nanocomposite insulating material prepared by the process according to any one of claims 1 to 7 in the detection of insulation defects by an insulation defect repairing robot, characterized in that, The insulation defect repairing robot comprises a detection unit, a repairing execution unit and a control unit, the detection unit comprises an electric field distortion detection module, an ultrasonic detection module, an infrared thermal imaging module, a shooting module and a data acquisition module, the repairing execution unit comprises an electric field module, a heating module, a micro-transportation module and a UV module, and the application comprises: When the electric field distortion detection module detects that the local electric field distortion value of the equipment to be detected is greater than or equal to 0.5 kV / m, local discharge detection and infrared thermal imaging detection are triggered; If the local discharge detection detects a discharge signal of 5 pC, the insulation defect area is located according to the discharge signal, and if the infrared thermal imaging module detects that the temperature of the insulation defect area is higher than that of the surrounding area by 3 DEG C, it is judged that the insulation defect area is a local discharge defect caused by insulation aging, and the insulation defect comprises an electrical tree defect and / or a mechanical micro-crack; The shooting module shoots an image of the insulation defect area, the data acquisition module identifies the internal micro-crack of the nano-composite insulation material, the local temperature change and the image of the insulation defect area according to the acquired electric field distortion value, constructs a three-dimensional defect model and generates a defect judgment result; The data acquisition module calculates the surface spraying amount and the internal injection amount of the nano-composite insulation material required for the insulation defect area according to the density of the nano-composite insulation material, the design thickness of the repair layer and the three-dimensional defect model, wherein the material injection amount of the electrical tree defect is calculated as 1.2 times the defect volume; The heating module heats and preheats the nano-composite insulation material to 35 DEG C, so that the viscosity of the material is reduced to below 900 mPa・s; The control unit generates a nano-composite insulation material transportation instruction, and the transportation instruction comprises a surface spraying stage transportation rate of 0.2 mL / min and an internal injection stage transportation rate of 0.1 mL / min; The micro-transportation module receives the transportation instruction to inject the preheated nano-composite insulation material into the electrical tree channel of the insulation defect area; and / or sprays the preheated nano-composite insulation material at the mechanical micro-crack of the insulation defect area When the pressure of the insulation defect area is detected to rise from an initial 0.05 MPa to 0.15 MPa, it is judged that the electrical tree channel is filled, and the injection is stopped; or the spraying is stopped when the mechanical micro-crack is detected to form a 0.5 mm repair layer. Start the UV module, use 365nm wavelength, 50W power UV light source to irradiate the repair area for 40s, so that the material is preliminarily cured to the insulation resistance of 1013Ω; Start the electric field module to apply a global electric field of 8kV / mm and superimpose a local enhanced electric field of 2kV / mm, so that the total electric field of the defect area reaches 10kV / mm, and start the heating module to raise the temperature of the defect area to 90~100℃ and keep it for 60min, triggering the double-driven self-repairing.

10. Use according to claim 9, characterized in that, During the spraying process, the shooting module monitors the spraying range in real time to ensure that the material covers the entire insulation defect area, and the thickness deviation is controlled within ±0.05mm; during the self-repairing process, the robot also monitors the temperature of the defect area in real time through the thermocouple, feeds back to the heating module controller to realize closed-loop temperature control, and the temperature deviation is ±2℃.

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