Crosslinked polyethylene insulated aluminum alloy power cable and preparation method thereof

Abstract

The invention belongs to the technical field of electric insulating materials. The invention relates to a cable, in particular to a crosslinked polyethylene insulated aluminum alloy power cable and a preparation method thereof. The product comprises an aluminum alloy conductor; the cross-linked polyethylene insulating layer is coated on the surface of the aluminum alloy conductor; wherein the cross-linked polyethylene insulating layer comprises a cross-linked polyethylene resin matrix and a composite filler dispersed in the cross-linked polyethylene resin matrix; the composite filler is formed by compounding hollow ellipsoidal aluminum oxide and hollow spherical aluminum oxide; the sphericity degree of the hollow ellipsoidal aluminum oxide is 0.5 to 0.6; the sphericity degree of the hollow spherical aluminum oxide is 0.8 to 0.9; the mass ratio of the hollow ellipsoidal aluminum oxide to the hollow spherical aluminum oxide is (1.2-1.6): 1; the dosage of the composite filler is 4-6% of the mass of the crosslinked polyethylene resin matrix; the median particle size of the hollow ellipsoidal aluminum oxide is greater than that of the hollow spherical aluminum oxide.

Description

Technical Field

[0001] This invention belongs to the field of electrical insulation materials technology. More specifically, it relates to a cross-linked polyethylene insulated aluminum alloy power cable and its preparation method. Background Technology

[0002] Power cables with aluminum alloy conductors are widely used in medium and low voltage power distribution due to their advantages such as good conductivity, light weight, and lower cost than pure aluminum and copper cables.

[0003] Polyethylene, especially low-density polyethylene and its derivatives, has long been widely used as insulation material for power cables due to its excellent electrical insulation properties, chemical resistance, ease of processing, and relatively low cost. To further improve the heat distortion resistance and mechanical strength of polyethylene insulation layers, cross-linking technology is widely applied. By transforming the linear molecular structure of polyethylene into a three-dimensional network cross-linked structure through chemical or physical methods, cross-linked polyethylene is formed, which can significantly improve its heat distortion temperature, aging resistance, and resistance to environmental stress cracking, thereby ensuring the reliability of cables during long-term operation.

[0004] However, in specific scenarios where cross-linked polyethylene insulation is applied to aluminum alloy conductor cables, existing preparation methods still face a series of challenges and problems that urgently need to be solved: For example, there are issues with crosslinking uniformity and efficiency: Currently, mainstream chemical crosslinking (such as peroxide crosslinking) requires prolonged heating in high-temperature, high-pressure vulcanization pipes, resulting in high energy consumption. Furthermore, for thicker insulation layers, uneven crosslinking is prone to occur—high crosslinking degree on the surface while insufficient crosslinking in the inner layers. This unevenness leads to inconsistent overall insulation performance and the presence of weak points. Internal stress and defect control in the insulation layer: In existing extrusion, crosslinking, and cooling processes, controlling process parameters is crucial. For example, if the cooling rate after extrusion is too fast, significant internal stress and micropores can easily form within the insulation layer. These internal defects, under the long-term influence of an electric field, may become the starting points for electrical trees, ultimately leading to insulation breakdown and shortening cable lifespan. Summary of the Invention

[0005] The technical problem this invention aims to solve is that existing cross-linked polyethylene alloy cable products suffer from poor cross-linking reactions between the surface and inner layers, particularly leading to internal stress or micropore defects that negatively impact product lifespan. To address these challenges, this invention provides a cross-linked polyethylene insulated aluminum alloy power cable and its preparation method.

[0006] The purpose of this invention is to provide a cross-linked polyethylene insulated aluminum alloy power cable.

[0007] Another objective of this invention is to provide a method for preparing cross-linked polyethylene insulated aluminum alloy power cables.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution: A cross-linked polyethylene insulated aluminum alloy power cable, comprising: Aluminum alloy conductor; And a cross-linked polyethylene insulation layer covering the surface of the aluminum alloy conductor; The cross-linked polyethylene insulation layer includes a cross-linked polyethylene resin matrix and composite fillers dispersed therein. The composite filler is composed of hollow ellipsoidal alumina and hollow spherical alumina.

[0009] The beneficial effects of the above technical solution are as follows: The above technical solution combines hollow ellipsoidal and hollow spherical nano-alumina with two different morphologies in a cross-linked polyethylene resin matrix. On the one hand, it forms a synergistic energy buffer system. Specifically, due to their asymmetric structure, hollow ellipsoidal particles become efficient stress concentration points and energy dissipation centers in a stress field. Their tips and curvature changes can actively induce and terminate crazes and induce shear band yielding, absorbing and dissipating a large amount of energy through complex plastic deformation processes. Hollow spherical particles, with their perfect symmetry, serve as ideal stress homogenization points, uniformly dispersing concentrated stress across the entire particle surface, preventing excessive stress concentration in local areas and the formation of destructive microcracks. The combination of the two constitutes a three-dimensional, multi-layered stress buffer system that can both actively dissipate energy and passively disperse stress. Through multi-layered stress buffering, the microscopic residual stress and defects (such as micropores and crazes) inside the insulation layer are greatly eliminated, significantly improving the material's resistance to environmental stress cracking and fundamentally inhibiting the initiation and growth of electrical trees, thus extending the insulation life. Secondly, the appropriate amount of spherical particles, acting as "balls," effectively mitigates the problem of a sharp increase in system viscosity caused by high content and high specific surface area nanofillers, ensuring excellent processability of the composite masterbatch during extrusion and smooth coating on the conductor surface. Simultaneously, the large specific surface area of ​​the two types of particles provides abundant attachment points for the polyethylene molecular chains, not only enhancing the interfacial bonding between the filler and the matrix but also potentially serving as "heterogeneous nucleation sites" for crosslinking reactions, guiding the formation of a denser and more uniform crosslinked three-dimensional network structure. This significantly improves the thermal conductivity and mechanical integrity of the insulation layer while ensuring the smooth progress of the industrial extrusion coating process. Furthermore, through optimization of the crosslinking network, a high-performance, highly consistent, and long-term reliable aluminum alloy conductor power cable is ultimately produced. Furthermore, the high specific surface area hollow ellipsoidal alumina, through its unique line and surface contact methods, can overlap with each other in the matrix to construct a highly efficient main thermally conductive framework network, much like the main road of a highway. The hollow spherical alumina fills the gaps in these framework networks, acting as "thermal conductive branches" and "bridges," connecting isolated thermally conductive islands. This significantly reduces the interfacial thermal resistance between fillers and between fillers and the matrix, thereby achieving rapid and uniform heat conduction within the insulation layer. It fundamentally reduces the internal and external temperature difference of the insulation layer during cross-linking cooling and current-carrying operation, suppressing macroscopic thermal stress caused by asynchronous thermal expansion and contraction at the source, and improving the cable's current carrying capacity and overload safety margin.

[0010] Furthermore, the sphericity of the hollow ellipsoidal alumina is 0.5-0.6; the sphericity of the hollow spherical alumina is 0.8-0.9.

[0011] Lower ellipsoidal sphericity ensures sufficient asymmetry in the particles to effectively achieve crack deflection and a high specific surface area; while higher sphericity ensures the most uniform stress distribution in spherical particles and minimal impact on melt viscosity.

[0012] Furthermore, the mass ratio of the hollow ellipsoidal alumina to the hollow spherical alumina is 1.2-1.6:1.

[0013] Ellipsoidal particles form the main body, constructing an efficient heat conduction and stress transfer framework; an appropriate amount of spherical particles fill the gaps in the framework, further enhancing heat conduction and optimizing the system's fluidity.

[0014] Furthermore, the amount of the composite filler is 4-6% of the mass of the cross-linked polyethylene resin matrix.

[0015] This amount of filler is sufficient to form a continuous and effective thermal conductivity and stress buffer network, significantly improving material performance; at the same time, it avoids extrusion difficulties, dielectric degradation, and unnecessary cost increases caused by excessive filler.

[0016] Furthermore, the median particle size D50 of the hollow ellipsoidal alumina is 50-200 nm, the median particle size D50 of the hollow spherical alumina is 20-100 nm, and the median particle size of the hollow ellipsoidal alumina is larger than the median particle size of the hollow spherical alumina.

[0017] Larger ellipsoidal particles form the main framework, constructing macroscopic heat conduction and stress dissipation paths; while smaller spherical particles fill the gaps between the larger particles and act on more microscopic stress concentration points.

[0018] Furthermore, the hollow ellipsoidal alumina has a BET specific surface area of ​​120-150 m².2 / g; the BET specific surface area of ​​the hollow spherical alumina is 30-50m². 2 / g; The BET specific surface area was obtained by standard nitrogen adsorption method.

[0019] Hollow particles have two surfaces, an inner and an outer surface, so their specific surface area is usually larger than that of solid particles.

[0020] A method for preparing cross-linked polyethylene insulated aluminum alloy power cables, the specific preparation steps of which include: Preparation of crosslinking masterbatch: After blending polyethylene base material, organic peroxide crosslinking agent and composite filler, the mixture is melt extruded and granulated to obtain crosslinking masterbatch; Conductor coating: After the aluminum alloy conductor is preheated, the cross-linked masterbatch is extruded through an extruder to coat the surface of the aluminum alloy conductor to form an insulating coating layer. Heating crosslinking: An aluminum alloy conductor with an insulating coating is introduced into a cross-linking pipe for a step-by-step heating cross-linking reaction. Gradient cooling: The cross-linked cable is then subjected to a gradient and slow cooling process to obtain a cross-linked polyethylene insulated aluminum alloy power cable.

[0021] Furthermore, the thermal crosslinking also includes: An aluminum alloy conductor with an insulating coating is introduced into the cross-linking conduit, which is then divided into three sections along the direction of travel: In the first section, the temperature is controlled at 150℃-165℃, and the residence time accounts for 30%-40% of the total cross-linking time; In the second section, the temperature rises to 185℃-200℃, and the residence time accounts for 40%-50% of the total cross-linking time; In the third section, the temperature drops to 170℃-175℃, and the residence time accounts for 10%-20% of the total cross-linking time; To carry out a three-gradient stepped heating crosslinking reaction.

[0022] This process precisely matches the decomposition kinetics of the peroxide crosslinking agent with the crosslinking reaction kinetics of polyethylene, ensuring that the crosslinking reaction proceeds uniformly, fully, and smoothly from the inside out.

[0023] Furthermore, the gradient cooling also includes: The cross-linked cable is slowly cooled to 100℃ at a rate of 1.5-3.5℃ / min; Then continue cooling to room temperature at a rate of 6-8℃ / min.

[0024] The extremely slow cooling in the high-temperature zone (above 100°C) provides sufficient energy and time for the molecular chain segments in the polyethylene crosslinking network to rearrange and relax, thereby releasing most of the thermal stress.

[0025] Furthermore, the preparation steps of the hollow ellipsoidal alumina include: using ellipsoidal polystyrene microspheres as templates, depositing an alumina hydrate shell layer on their surface through the hydrolysis of aluminum nitrate, centrifuging, washing, drying, calcining at 500°C to remove the template, and then breaking down and sieving to obtain hollow ellipsoidal alumina; The preparation steps of the hollow spherical alumina include: using spherical polystyrene microspheres as templates, depositing an alumina hydrate shell on their surface by hydrolysis of aluminum nitrate, centrifuging, washing, drying, calcining at 500°C to remove the template, and then breaking down and sieving to obtain hollow spherical alumina. Detailed Implementation

[0026] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0027] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0028] Example 1 Preparation of hollow ellipsoidal alumina: By weight, take 10 parts of ellipsoidal PS microspheres, 180 parts of anhydrous ethanol, 50 parts of deionized water, and 50 parts of aluminum nitrate nonahydrate. Among them, the ellipsoidal PS microspheres were selected with a D50 of 40nm and a sphericity of 0.45. The selection of this particle size and sphericity was a reasonable choice based on the consideration of compensating for calcination shrinkage. First, ellipsoidal PS microspheres are dispersed in anhydrous ethanol to form a uniform suspension; Aluminum nitrate nonahydrate was dissolved in deionized water, and ammonia was added dropwise to adjust the pH to 8, forming a transparent sol. This sol was then added dropwise to the suspension at a rate of 2 mL / min, maintaining the pH at 8. After the addition was complete, the mixture was stirred at 60°C for 4 hours. After the reaction was complete, the product was separated by centrifugation and washed three times with deionized water. The washed product was dried and then transferred to a muffle furnace. In an air atmosphere, the temperature was increased to 500°C at a rate of 2°C / min and calcined for 3 hours to completely remove the PS template and transform the amorphous alumina into a crystalline state. The calcined powder was sieved using a nanoscale vibrating sieve and then lightly dispersed using a soft ball mill to finally obtain hollow ellipsoidal alumina with a sphericity of 0.5, a median particle size D50 of 50 nm, and a BET specific surface area of ​​150 m² / g. Preparation of hollow spherical alumina: The preparation method is basically the same as the preparation method of the above ellipsoidal alumina, the only difference being the sphericity and D50 of the PS microspheres; specifically, the PS microspheres are selected with a D50 of 15nm and a sphericity of 0.75. Hollow spherical alumina was finally obtained, with a sphericity of 0.8, a median particle size D50 of 20 nm, and a BET specific surface area of ​​50 m² / g. Preparation of composite packing: The hollow ellipsoidal alumina and hollow spherical alumina prepared above were accurately weighed at a mass ratio of 1.2:1 and loaded into a three-dimensional motion mixer. They were mixed at a frequency of 30 Hz for 60 min to ensure that the two different morphologies of the fillers were mixed evenly, thus obtaining the composite filler. Preparation of crosslinking masterbatch: Low-density polyethylene (LDPE) base material, an organic peroxide crosslinking agent (dicumyl peroxide, DCP), and a composite filler are blended at high speed. The composite filler is used at 4% of the total mass of the LDPE base material and DCP. The blended material is fed into a twin-screw extruder, melt-blended, extruded, cooled, and pelletized at 120°C to obtain a nano-composite crosslinked polyethylene masterbatch. Conductor coating: The aluminum alloy conductor is heated to 80℃ ± 10℃ by a preheating device, and then the cross-linked masterbatch prepared above is fed into an extruder. After being plasticized in the extruder, it is continuously and uniformly extruded onto the surface of the preheated aluminum alloy conductor to form an insulating coating layer with a thickness of 1.0mm. Heating crosslinking: The insulated cable is immediately introduced into a vertical cross-linking pipe for a stepped temperature-increasing cross-linking reaction. The cross-linking pipe is divided into three precisely temperature-controlled sections along the cable's travel direction: First section: Temperature controlled at 150℃, the cable stays in this section for 30% of the total cross-linking time; Second section: The temperature rises to 185℃, and the cable spends 40% of the total cross-linking time in this section; Third section: The temperature drops to 170℃, and the cable spends 10% of the total cross-linking time in this section; The total heating crosslinking time is 8 minutes; Gradient cooling: After cross-linking, the cable enters a gradient cooling system. First, the cable is slowly cooled to 100°C at a rate of 1.5°C / min. Then, it is cooled to room temperature (approximately 25°C) at a rate of 6°C / min using methods such as air cooling or water mist cooling, thus obtaining the cross-linked polyethylene insulated aluminum alloy power cable.

[0029] Example 2 Preparation of hollow ellipsoidal alumina: By weight, take 11 parts of ellipsoidal PS microspheres, 190 parts of anhydrous ethanol, 55 parts of deionized water, and 55 parts of aluminum nitrate nonahydrate. Among them, the ellipsoidal PS microspheres were selected with a D50 of 100 nm and a sphericity of 0.5. The selection of particle size and sphericity was a reasonable choice based on the consideration of compensating for calcination shrinkage. First, ellipsoidal PS microspheres are dispersed in anhydrous ethanol to form a uniform suspension; Aluminum nitrate nonahydrate was dissolved in deionized water, and ammonia was added dropwise to adjust the pH to 8.6, forming a transparent sol. This sol was then added dropwise to the suspension at a rate of 3 mL / min, maintaining the pH at 8.6. After the addition was complete, the mixture was stirred at 60°C for 4 hours. After the reaction was complete, the product was centrifuged and washed three times with deionized water. The washed product was dried and then transferred to a muffle furnace. In an air atmosphere, the temperature was increased to 500°C at a rate of 2°C / min and calcined for 3 hours to completely remove the PS template and transform the amorphous alumina into a crystalline state. The calcined powder was sieved using a nanoscale vibrating sieve and then lightly dispersed using a soft ball mill to finally obtain hollow ellipsoidal alumina with a sphericity of 0.54, a median particle size D50 of 120 nm, and a BET specific surface area of ​​134 m² / g. Preparation of hollow spherical alumina: The preparation method is basically the same as the preparation method of the above ellipsoidal alumina, the only difference being the sphericity and D50 of the PS microspheres; specifically, the PS microspheres are selected with a D50 of 40nm and a sphericity of 0.8. Hollow spherical alumina was finally obtained, with a sphericity of 0.86, a median particle size D50 of 50 nm, and a BET specific surface area of ​​40 m² / g. Preparation of composite packing: The hollow ellipsoidal alumina and hollow spherical alumina prepared above were accurately weighed at a mass ratio of 1.4:1 and loaded into a three-dimensional motion mixer. They were mixed at a frequency of 30 Hz for 60 min to ensure that the two different morphologies of the fillers were mixed evenly, thus obtaining the composite filler. Preparation of crosslinking masterbatch: Low-density polyethylene (LDPE) base material, organic peroxide crosslinking agent (dicumyl peroxide, DCP), and composite filler are high-speed blended. The composite filler is used at 5% of the total mass of the LDPE base material and DCP. The blended material is fed into a twin-screw extruder, melt-blended, extruded, cooled, and pelletized at 130°C to obtain a nano-composite crosslinked polyethylene masterbatch. Conductor coating: The aluminum alloy conductor is heated to 80℃ ± 10℃ using a preheating device. Then, the crosslinked masterbatch prepared above is fed into an extruder. After plasticizing in the extruder, it is continuously and uniformly extruded onto the surface of the preheated aluminum alloy conductor to form an insulating coating layer with a thickness of 1.1mm. Heating crosslinking: The insulated cable is immediately introduced into a vertical cross-linking pipe for a stepped temperature-increasing cross-linking reaction. The cross-linking pipe is divided into three precisely temperature-controlled sections along the cable's travel direction: First section: Temperature controlled at 155℃, the cable stays in this section for 35% of the total cross-linking time; Second section: The temperature rises to 190℃, and the cable spends 45% of the total cross-linking time in this section; Third section: The temperature drops to 172℃, and the cable spends 15% of the total cross-linking time in this section; The total heating crosslinking time is 8 minutes; Gradient cooling: After cross-linking, the cable enters a gradient cooling system. First, the cable is slowly cooled to 100°C at a rate of 2.5°C / min. Then, it is cooled to room temperature (approximately 25°C) at a rate of 7°C / min using methods such as air cooling or water mist cooling, thus obtaining the cross-linked polyethylene insulated aluminum alloy power cable.

[0030] Example 3 Preparation of hollow ellipsoidal alumina: By weight, take 12 parts of ellipsoidal PS microspheres, 200 parts of anhydrous ethanol, 60 parts of deionized water, and 60 parts of aluminum nitrate nonahydrate. Among them, the ellipsoidal PS microspheres have a D50 of 180nm and a sphericity of 0.55. The selection of this particle size and sphericity is a reasonable choice based on the consideration of compensating for calcination shrinkage. First, ellipsoidal PS microspheres are dispersed in anhydrous ethanol to form a uniform suspension; Aluminum nitrate nonahydrate was dissolved in deionized water, and ammonia was added dropwise to adjust the pH to 9, forming a transparent sol. This sol was then added dropwise to the suspension at a rate of 4 mL / min, maintaining the pH at 9. After the addition was complete, the mixture was stirred at 60°C for 4 hours. After the reaction was complete, the product was centrifuged and washed three times with deionized water. The washed product was dried and then transferred to a muffle furnace. In an air atmosphere, the temperature was increased to 500°C at a rate of 2°C / min and calcined for 3 hours to completely remove the PS template and transform the amorphous alumina into a crystalline state. The calcined powder was sieved using a nanoscale vibrating sieve and then lightly dispersed using a soft ball mill to finally obtain hollow ellipsoidal alumina with a sphericity of 0.6, a median particle size D50 of 200 nm, and a BET specific surface area of ​​120 m² / g. Preparation of hollow spherical alumina: The preparation method is basically the same as the preparation method of the above ellipsoidal alumina, the only difference being the sphericity and D50 of the PS microspheres; specifically, the PS microspheres are selected with a D50 of 90nm and a sphericity of 0.85. Hollow spherical alumina was finally obtained, with a sphericity of 0.9, a median particle size D50 of 100 nm, and a BET specific surface area of ​​30 m² / g. Preparation of composite packing: The hollow ellipsoidal alumina and hollow spherical alumina prepared above were accurately weighed at a mass ratio of 1.6:1 and loaded into a three-dimensional motion mixer. They were mixed at a frequency of 30 Hz for 60 minutes to ensure that the two different morphologies of the fillers were mixed evenly, thus obtaining the composite filler. Preparation of crosslinking masterbatch: Low-density polyethylene (LDPE) base material, organic peroxide crosslinking agent (dicumyl peroxide, DCP), and composite filler are high-speed blended. The composite filler is used at 6% of the total mass of the LDPE base material and DCP. The blended material is fed into a twin-screw extruder, melt-blended, extruded, cooled, and pelletized at 150°C to obtain a nano-composite crosslinked polyethylene masterbatch. Conductor coating: The aluminum alloy conductor is heated to 80℃ ± 10℃ using a preheating device. Then, the crosslinked masterbatch prepared above is fed into an extruder. After plasticizing in the extruder, it is continuously and uniformly extruded onto the surface of the preheated aluminum alloy conductor to form an insulating coating layer with a thickness of 1.2mm. Heating crosslinking: The insulated cable is immediately introduced into a vertical cross-linking pipe for a stepped temperature-increasing cross-linking reaction. The cross-linking pipe is divided into three precisely temperature-controlled sections along the cable's travel direction: First section: Temperature controlled at 165℃, the cable stays in this section for 40% of the total cross-linking time; Second section: The temperature rises to 200℃, and the cable spends 50% of the total cross-linking time in this section; Third section: The temperature drops to 175℃, and the cable spends 20% of the total cross-linking time in this section; The total heating crosslinking time is 8 minutes; Gradient cooling: After cross-linking, the cable enters a gradient cooling system. First, the cable is slowly cooled to 100°C at a rate of 3.5°C / min. Then, it is cooled to room temperature (approximately 25°C) at a rate of 8°C / min using methods such as air cooling or water mist cooling, thus obtaining the cross-linked polyethylene insulated aluminum alloy power cable.

[0031] Example 4 The difference between this embodiment and Embodiment 1 lies in the gradient cooling process, specifically: After cross-linking is completed, the cable enters the gradient cooling system. The cable is cooled directly to room temperature (approximately 25°C) at a rate of 6°C / min using methods such as air cooling or water mist cooling, thus obtaining the cross-linked polyethylene insulated aluminum alloy power cable.

[0032] Example 5 Compared with Example 1, the difference in this embodiment is that the mass ratio of the hollow ellipsoidal alumina to the hollow spherical alumina is 2:1, while the other conditions remain unchanged.

[0033] Example 6 The difference between this embodiment and Embodiment 1 is that the mass ratio of the hollow ellipsoidal alumina to the hollow spherical alumina is 1:1, while the other conditions remain unchanged.

[0034] Comparative Example 1 The difference between this comparative example and Example 1 is that hollow ellipsoidal alumina was not added, while all other conditions remained unchanged.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that hollow spherical alumina was not added, while all other conditions remained unchanged.

[0036] The performance of the products obtained in the above embodiments and comparative examples was tested. The specific test methods and test results are shown below: The insulation layer is peeled off from the finished cable and pressed into a flat sheet; According to standard GB / T 1410, the volume resistivity of the above-mentioned thin film was tested, and the detailed test results are shown in Table 1. In addition, parallel thin films were prepared and subjected to accelerated aging tests. Specifically, after 30 days of accelerated aging at a temperature of 85°C and a relative humidity of 90%, the volume resistivity of the thin films was tested again according to the above standards. The detailed test results are shown in Table 1. Table 1: Product Performance Test Results As can be seen from the test results in Table 1, the product obtained by the present invention has excellent insulation performance. Furthermore, after a long period of accelerated aging test, the insulation performance of the product can be maintained relatively better, which has a better effect on extending the service life of the product.

[0037] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A cross-linked polyethylene insulated aluminum alloy power cable, characterized in that, include: Aluminum alloy conductor; And a cross-linked polyethylene insulation layer covering the surface of the aluminum alloy conductor; The cross-linked polyethylene insulation layer includes a cross-linked polyethylene resin matrix and composite fillers dispersed therein. The composite filler is composed of hollow ellipsoidal alumina and hollow spherical alumina.

2. The cross-linked polyethylene insulated aluminum alloy power cable according to claim 1, characterized in that, The sphericity of the hollow ellipsoidal alumina is 0.5-0.6; the sphericity of the hollow spherical alumina is 0.8-0.

9.

3. The cross-linked polyethylene insulated aluminum alloy power cable according to claim 1, characterized in that, The mass ratio of the hollow ellipsoidal alumina to the hollow spherical alumina is 1.2-1.6:

1.

4. The cross-linked polyethylene insulated aluminum alloy power cable according to claim 3, characterized in that, The amount of the composite filler is 4-6% of the mass of the cross-linked polyethylene resin matrix.

5. The cross-linked polyethylene insulated aluminum alloy power cable according to claim 1, characterized in that, The median particle size D50 of the hollow ellipsoidal alumina is 50-200 nm, the median particle size D50 of the hollow spherical alumina is 20-100 nm, and the median particle size of the hollow ellipsoidal alumina is greater than the median particle size of the hollow spherical alumina.

6. The cross-linked polyethylene insulated aluminum alloy power cable according to claim 5, characterized in that, The hollow ellipsoidal alumina has a BET specific surface area of ​​120-150 m². 2 / g; the BET specific surface area of ​​the hollow spherical alumina is 30-50m². 2 / g; The BET specific surface area was obtained by standard nitrogen adsorption method.

7. A method for preparing a cross-linked polyethylene insulated aluminum alloy power cable according to any one of claims 1-6, characterized in that, The specific preparation steps include: Preparation of crosslinking masterbatch: After blending polyethylene base material, organic peroxide crosslinking agent and composite filler, the mixture is melt extruded and granulated to obtain crosslinking masterbatch; Conductor coating: After the aluminum alloy conductor is preheated, the cross-linked masterbatch is extruded through an extruder to coat the surface of the aluminum alloy conductor to form an insulating coating layer. Heating crosslinking: An aluminum alloy conductor with an insulating coating is introduced into a cross-linking pipe for a step-by-step heating cross-linking reaction. Gradient cooling: The cross-linked cable is then subjected to a gradient and slow cooling process to obtain a cross-linked polyethylene insulated aluminum alloy power cable.

8. The method for preparing a cross-linked polyethylene insulated aluminum alloy power cable according to claim 7, characterized in that, The heating crosslinking also includes: An aluminum alloy conductor with an insulating coating is introduced into the cross-linking conduit, which is then divided into three sections along the direction of travel: In the first section, the temperature is controlled at 150℃-165℃, and the residence time accounts for 30%-40% of the total cross-linking time; In the second section, the temperature rises to 185℃-200℃, and the residence time accounts for 40%-50% of the total cross-linking time; In the third section, the temperature drops to 170℃-175℃, and the residence time accounts for 10%-20% of the total cross-linking time; To carry out a three-gradient stepped heating crosslinking reaction.

9. The method for preparing a cross-linked polyethylene insulated aluminum alloy power cable according to claim 7, characterized in that, The gradient cooling also includes: The cross-linked cable is slowly cooled to 100℃ at a rate of 1.5-3.5℃ / min; Then continue cooling to room temperature at a rate of 6-8℃ / min.

10. The method for preparing a cross-linked polyethylene insulated aluminum alloy power cable according to claim 7, characterized in that, The preparation steps of the hollow ellipsoidal alumina include: using ellipsoidal polystyrene microspheres as templates, depositing an alumina hydrate shell on their surface by hydrolysis of aluminum nitrate, centrifuging, washing, drying, calcining at 500°C to remove the template, and then breaking down and sieving to obtain hollow ellipsoidal alumina. The preparation steps of the hollow spherical alumina include: using spherical polystyrene microspheres as templates, depositing an alumina hydrate shell on their surface by hydrolysis of aluminum nitrate, centrifuging, washing, drying, calcining at 500°C to remove the template, and then breaking down and sieving to obtain hollow spherical alumina.

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