Bending-resistant photovoltaic electrical cable and preparation method thereof

Abstract

The invention discloses an anti-bending photovoltaic electrical cable and a preparation method thereof, and belongs to the technical field of electrical cables, and the cable comprises a conductor core, an insulating layer, a flexible middle layer and an outer sheath layer which are sequentially arranged from inside to outside. And the conductor core adopts a heterostructure formed by layering and twisting an inner layer high-ductility metal wire and an outer layer high-tensile strength metal wire in opposite twisting directions. And the flexible middle layer is made of a thermoplastic elastomer with specific hardness. The outer sheath layer is made of a weather-resistant elastomer composite material reinforced by a composite mineral filler, and the composite mineral filler is a mixture of surface-modified flaky talcum powder and chopped glass fibers. The preparation method of the cable comprises the processes of conductor stranding annealing, insulation irradiation crosslinking, co-extrusion of the flexible middle layer and the outer sheath layer and the like. The cable disclosed by the invention is suitable for dynamic bending occasions such as a photovoltaic tracking bracket and the like, and has excellent anti-bending fatigue life and long-term reliability in a severe environment.

Description

Technical Field

[0001] This invention relates to the field of electrical cable technology, and in particular to a bending-resistant photovoltaic electrical cable and its preparation method. Background Technology

[0002] With the rapid development of photovoltaic power generation technology and the continuous drive for cost reduction and efficiency improvement, photovoltaic tracking bracket systems, which offer advantages in power generation, have been widely used. These systems use a drive mechanism to make photovoltaic modules rotate in real time to follow the sun's position, thereby significantly improving power generation efficiency. However, this motion characteristic places far more stringent requirements on the electrical connection cables, a key component, than on fixed photovoltaic power plants. The cables must be exposed to complex environmental stresses such as ultraviolet radiation, ozone, high and low temperature cycles, rain, and wind and sand for extended periods outdoors, while also withstanding long-term, high-frequency dynamic bending and torsional mechanical stresses generated by the constant rotation of the brackets. This harsh operating condition, coupled with environmental aging and mechanical fatigue, poses a severe challenge to the long-term reliability of traditional photovoltaic cables.

[0003] Currently, static photovoltaic cables are widely used in the industry. The design focus of these cables is on their static current carrying capacity, weather resistance, UV resistance, and flame retardancy. Their conductors typically use a stranded structure of conventional homogeneous materials, while the sheath is often made of cross-linked polyolefins or elastomers, primarily for weather resistance. However, in actual dynamic applications using tracking brackets, the shortcomings of these cables are quickly exposed.

[0004] When conventional stranded conductors of uniform cross-section and homogeneous material are repeatedly bent, the uneven stress on the inner and outer layers of monofilaments easily leads to relative slippage and fretting wear. Long-term effects can cause fatigue fracture of the monofilaments, resulting in increased DC resistance and heat generation in the conductor. In severe cases, this can lead to electrical connection failure and even fire hazards. Existing improvements, such as increasing the conductor strand density or using finer monofilaments, can improve initial flexibility to some extent, but they do not change the wear mechanism of inter-filament friction, thus offering limited improvement in long-term bending fatigue life.

[0005] To ensure electrical safety, the insulation layer typically possesses high modulus and rigidity; while the outer sheath material must exhibit a certain degree of elasticity to meet installation flexibility and environmental protection requirements. During dynamic bending, significant shear stress concentration occurs at the interface between the two materials with significantly different moduli. This periodic stress can easily lead to delamination between the insulation layer and the sheath layer, or cause microcracks within the insulation layer. Delamination compromises the structural integrity, affects heat dissipation, and may introduce moisture; while microcracks in the insulation layer directly impair its electrical insulation performance, posing a safety hazard.

[0006] Furthermore, traditional weather-resistant sheath materials often fall short in terms of tear resistance, abrasion resistance, kerf lengthening resistance, and resistance to permanent deformation. Under the long-term reciprocating motion of the tracking bracket and the potential friction and scratching with the bracket's metal components, the sheath is prone to cracking and damage, losing its protective function for the internal structure and accelerating the aging and failure of the overall cable.

[0007] Existing technical solutions mostly focus on improving single performance indicators or optimizing only under static or quasi-static conditions, lacking a system-wide approach and a collaborative design specifically targeting the core failure mode of dynamic bending fatigue. Therefore, there is an urgent need for a novel cable structure design and material system that can enhance the conductor's fatigue resistance mechanism, interlayer stress buffering mechanism, and the comprehensive protection capability of the outer sheath. Summary of the Invention

[0008] The purpose of this invention is to provide a bend-resistant photovoltaic electrical cable and its manufacturing method to solve the above-mentioned problems.

[0009] This invention provides a bending-resistant photovoltaic electrical cable, comprising, from the inside out: a conductor core, an insulation layer, a flexible intermediate layer, and an outer sheath layer; The conductor core is made of at least two layers of metal wires stranded in opposite directions, wherein the inner layer of metal wire is annealed copper wire or annealed tin-plated copper wire, and the outer layer of metal wire is tin-plated copper alloy wire or tough copper wire with a tensile strength of not less than 350MPa. An insulating layer covers the outside of the conductor core; The flexible interlayer is wrapped around the outside of the insulation layer. Its material is a thermoplastic elastomer with a Shore A hardness of 50-70 degrees. The thermoplastic elastomer is selected from at least one of thermoplastic polyurethane, polyester elastomer or styrene elastomer. The outer sheath layer covers the outside of the flexible intermediate layer. Its material is a weather-resistant elastomer composite material, which includes, by weight: 70-90 parts of polyolefin thermoplastic elastomer, 10-20 parts of ethylene-vinyl acetate copolymer, 15-30 parts of composite mineral filler, 1-2 parts of antioxidant, and 0.5-1.5 parts of light stabilizer. The composite mineral filler is a mixture of flake talc powder modified with silane coupling agent and chopped glass fiber, with a weight ratio of (1.5-3):1.

[0010] Preferably, the stranding structure of the conductor core is as follows: the inner layer consists of 15-25 strands of annealed copper wire with a diameter of 0.10-0.16 mm stranded in a first direction, with a pitch ratio of 12-16; the outer layer consists of 20-35 strands of tin-plated copper alloy wire with a diameter of 0.08-0.13 mm stranded in the opposite direction, with a pitch ratio of 10-14.

[0011] Preferably, in the composite mineral filler of the outer sheath layer, the particle size D50 of the flaky talc powder is 5-15μm and the aspect ratio is greater than 10; the length of the chopped glass fiber is 100-300μm and the diameter is 10-15μm.

[0012] Preferably, the weather-resistant elastomer composite material of the outer sheath layer further includes 5-12 parts by weight of a halogen-free flame retardant, wherein the halogen-free flame retardant is at least one of aluminum hydroxide, magnesium hydroxide, or phosphorus-nitrogen flame retardants.

[0013] Preferably, the insulation layer is an irradiated cross-linked low-smoke halogen-free polyolefin insulation layer with a thickness of 0.6-1.0 mm; the flexible intermediate layer has a thickness of 0.2-0.4 mm, and its material and the material of the outer sheath layer can form a physically fused bonding interface during co-extrusion.

[0014] A method for manufacturing the bending-resistant photovoltaic electrical cable as described above is provided, comprising the following steps: S1. Conductor stranding and annealing: The inner copper wire and the outer copper alloy wire are stranded into a conductor core in opposite directions using a high-speed stranding machine, and the conductor core is continuously annealed online at a temperature of 300-450℃. S2, Insulation layer extrusion and cross-linking: The conductor core obtained in step S1 is extruded with insulating material through an extruder to form an insulating layer, and then immediately enters an electron irradiation cross-linking device for cross-linking and curing; S3, Co-extrusion of flexible intermediate layer and outer sheath layer: a) Preparation of outer sheath material: Polyolefin thermoplastic elastomer and ethylene-vinyl acetate copolymer are melt-blended in an internal mixer at 140-160℃, and then pretreated composite mineral filler, antioxidant and light stabilizer are added. After uniform mixing, the mixture is granulated. b) Using a double-layer co-extrusion machine, the wire core obtained in step S2 is preheated and then extruded simultaneously with the flexible intermediate layer material and the outer sheath material particles obtained in step a). The extrusion temperature of the flexible intermediate layer is 10-20°C lower than that of the outer sheath layer. The core is formed in one piece by a co-extrusion die. S4. Cooling and post-processing: The co-extruded cable is water-cooled or air-cooled for shaping, and then equilibrated at room temperature for more than 24 hours after winding.

[0015] Preferably, in step S2, the dose of electron irradiation crosslinking is 12-16 Mrad.

[0016] Preferably, in step S3 a), the pretreatment method of the composite mineral filler is as follows: preheat the flake talc powder and chopped glass fiber in a high-speed mixer to 90-110°C, add 1.0-2.0% of the total weight of the filler in silane coupling agent ethanol solution, stir at high speed for 10-20 minutes to make it uniformly coated, and then dry.

[0017] Preferably, in step S3 b), the temperature of each section of the extruder for the outer sheath layer (3) material is set as follows: Zone 1 150-160℃, Zone 2 160-170℃, Zone 3 170-180℃, and the die head 175-185℃.

[0018] Preferably, after the irradiation crosslinking is completed in step S2, the surface of the insulating layer (2) is subjected to plasma surface treatment or flame treatment at a processing linear speed of 20-40 m / min.

[0019] As described above, the bending-resistant photovoltaic electrical cable is used on the DC side of the photovoltaic power generation system, especially in the movable connection part of the photovoltaic tracking bracket. The cable can withstand more than 10,000 unidirectional bending or more than 5,000 reciprocating bending tests with a diameter of no less than 6 times the outer diameter of the cable in an environment of -40℃ to 90℃.

[0020] Therefore, this invention employs the aforementioned anti-bending photovoltaic electrical cable and its manufacturing method. Through a unique reverse-stranded heterogeneous conductor structure, it utilizes an inner layer of high-ductility copper wire to absorb deformation energy and an outer layer of high-strength material to provide support. Combined with reverse stranding to suppress structural loosening, the cable can withstand over 10,000 unidirectional or 5,000 reciprocating bends under simulated tracking bracket conditions, with extremely low conductor resistance change rate, fundamentally ensuring long-term stable electrical performance of the dynamic connection. The added flexible intermediate layer serves as a mechanical transition zone; its moderate hardness effectively absorbs and disperses the shear stress between the insulation layer and the rigid sheath layer. Combined with insulation layer surface treatment and co-extrusion processes, a strong physical bond between the layers is achieved, completely avoiding insulation damage or interlayer delamination caused by stress concentration. The outer sheath is made of a weather-resistant elastomer composite material reinforced with specific composite mineral fillers. Flaky talc enhances the sheath's rigidity, dimensional stability, and barrier properties, while chopped glass fiber significantly enhances tensile strength and creep resistance. The two components work synergistically to give the sheath excellent tear resistance, abrasion resistance, scratch resistance, and low permanent deformation rate, while maintaining necessary flexibility and excellent UV and high / low temperature resistance, fully meeting the requirements for long-term dynamic outdoor use. The processes involved, such as conductor continuous annealing, insulation irradiation crosslinking, filler pretreatment, multi-layer co-extrusion, and surface treatment, are all innovative combinations and parameter optimizations of mature technologies. The production process is smooth, quality control points are clearly defined, and it possesses good feasibility for large-scale production.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the anti-bending photovoltaic electrical cable of the present invention. Detailed Implementation

[0023] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0025] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0026] This invention provides a bending-resistant photovoltaic electrical cable, comprising, from the inside out: a conductor core 1, an insulation layer 2, a flexible intermediate layer 4, and an outer sheath layer 3; The conductor core 1 is formed by stranding at least two layers of metal wires in opposite directions, wherein the inner layer of metal wire is annealed copper wire or annealed tin-plated copper wire, and the outer layer of metal wire is tin-plated copper alloy wire or tough copper wire with a tensile strength of not less than 350MPa. Insulating layer 2 covers the outside of conductor core 1; The flexible intermediate layer 4 covers the outside of the insulating layer 2. Its material is a thermoplastic elastomer with a Shore A hardness of 50-70 degrees. The thermoplastic elastomer is selected from at least one of thermoplastic polyurethane, polyester elastomer or styrene elastomer. The outer sheath layer 3 covers the outside of the flexible intermediate layer 4. Its material is a weather-resistant elastomer composite material, which includes, by weight: 70-90 parts of polyolefin thermoplastic elastomer, 10-20 parts of ethylene-vinyl acetate copolymer, 15-30 parts of composite mineral filler, 1-2 parts of antioxidant, and 0.5-1.5 parts of light stabilizer. The composite mineral filler is a mixture of flake talc powder modified with silane coupling agent and chopped glass fiber, with a weight ratio of (1.5-3):1.

[0027] To further optimize the above technical solution, the stranding structure of conductor core 1 is as follows: the inner layer consists of 15-25 strands of annealed copper wire with a diameter of 0.10-0.16mm stranded in the first direction, with a pitch ratio of 12-16; the outer layer consists of 20-35 strands of tin-plated copper alloy wire with a diameter of 0.08-0.13mm stranded in the opposite direction, with a pitch ratio of 10-14.

[0028] To further optimize the above technical solution, in the composite mineral filler of the outer sheath layer 3, the particle size D50 of the flaky talc powder is 5-15μm and the aspect ratio is greater than 10; the length of the short-cut glass fiber is 100-300μm and the diameter is 10-15μm.

[0029] To further optimize the above technical solution, the weather-resistant elastomer composite material of the outer sheath layer 3 also contains 5-12 parts by weight of halogen-free flame retardant, which is at least one of aluminum hydroxide, magnesium hydroxide or phosphorus-nitrogen flame retardant.

[0030] To further optimize the above technical solution, the insulation layer 2 is an irradiated cross-linked low-smoke halogen-free polyolefin insulation layer with a thickness of 0.6-1.0 mm; the flexible intermediate layer 4 has a thickness of 0.2-0.4 mm, and its material and the material of the outer sheath layer 3 can form a physical fusion bonding interface during co-extrusion.

[0031] A method for manufacturing the bending-resistant photovoltaic electrical cable as described above is provided, comprising the following steps: S1. Conductor stranding and annealing: The inner copper wire and the outer copper alloy wire are stranded in opposite directions to form conductor core 1 through a high-speed stranding machine, and conductor core 1 is continuously annealed online at a temperature of 300-450℃. S2, Insulation layer extrusion and cross-linking: The conductor core 1 obtained in step S1 is extruded with insulating material through an extruder to form insulation layer 2, and then immediately enters an electron irradiation cross-linking device for cross-linking and curing. S3, Co-extrusion of flexible intermediate layer and outer sheath layer: a) Preparation of outer sheath material: Polyolefin thermoplastic elastomer and ethylene-vinyl acetate copolymer are melt-blended in an internal mixer at 140-160℃, and then pretreated composite mineral filler, antioxidant and light stabilizer are added. After uniform mixing, the mixture is granulated. b) Using a double-layer co-extrusion machine, the wire core obtained in step S2 is preheated and then extruded simultaneously with the flexible intermediate layer 4 material and the outer sheath material particles obtained in step a). The extrusion temperature of the flexible intermediate layer 4 is 10-20°C lower than that of the outer sheath layer 3. The core is integrally formed by the co-extrusion die. S4. Cooling and post-processing: The co-extruded cable is water-cooled or air-cooled for shaping, and then equilibrated at room temperature for more than 24 hours after winding.

[0032] To further optimize the above technical solution, in step S2, the dose of electron irradiation crosslinking is 12-16 Mrad.

[0033] To further optimize the above technical solution, in step S3 a), the pretreatment method of the composite mineral filler is as follows: preheat the flake talc powder and chopped glass fiber in a high-speed mixer to 90-110°C, add 1.0-2.0% of the total weight of the filler in silane coupling agent ethanol solution, stir at high speed for 10-20 minutes to make it uniformly coated, and then dry.

[0034] To further optimize the above technical solution, in step S3 b), the temperature of each section of the extruder for the outer sheath layer 3 material is set as follows: Zone 1 150-160℃, Zone 2 160-170℃, Zone 3 170-180℃, and the die head 175-185℃.

[0035] To further optimize the above technical solution, after the irradiation crosslinking is completed in step S2, the surface of the insulating layer 2 is subjected to plasma surface treatment or flame treatment at a processing linear speed of 20-40 m / min.

[0036] As described above, the bending-resistant photovoltaic electrical cable is used on the DC side of the photovoltaic power generation system, especially in the movable connection part of the photovoltaic tracking bracket. The cable can withstand more than 10,000 unidirectional bending or more than 5,000 reciprocating bending tests with a diameter of no less than 6 times the outer diameter of the cable in an environment of -40℃ to 90℃.

[0037] To provide a clearer and more detailed description of the bending-resistant photovoltaic electrical cable and its preparation method provided by the embodiments of the present invention, the following description will be based on specific embodiments.

[0038] Example 1 This embodiment provides a bending-resistant cable suitable for photovoltaic tracking brackets in temperate climates. The conductor core 1 consists of 20 strands of soft-state annealed tin-plated copper wire with a diameter of 0.12 mm, twisted in a right-hand direction as the inner layer, and 28 strands of tin-plated copper alloy wire with a diameter of 0.10 mm and a tensile strength ≥380 MPa, twisted in a left-hand direction as the outer layer. After twisting, it is continuously annealed online at 380°C to eliminate internal stress. The insulation layer 2 is made of low-smoke halogen-free flame-retardant irradiated cross-linked polyolefin material. After being directly extruded to a thickness of 0.8 mm outside the conductor core, it is immediately cross-linked by electron irradiation with a dose of 14 Mrad. Subsequently, the surface of the cross-linked insulation layer is subjected to plasma treatment with a power of 3 kW and a line speed of 25 m / min to enhance its surface activity. The flexible intermediate layer 4 is made of polyester thermoplastic elastomer with a Shore A hardness of 60 degrees, and is co-extruded with the outer sheath layer 3.

[0039] The outer sheath layer 3 is prepared using the following process: First, 80 parts by weight of polyolefin thermoplastic elastomer and 15 parts by weight of ethylene-vinyl acetate copolymer are blended in an intensive kneading process at 155°C. Then, 22 parts by weight of composite mineral filler treated with a silane coupling agent are added. This filler consists of 15 parts of flake talc powder with a particle size D50 of 10 μm and 7 parts of chopped glass fibers with a length of 200 μm, as well as antioxidants, light stabilizers, and 8 parts of magnesium hydroxide flame retardant. After uniform mixing, the mixture is granulated. During co-extrusion, the sheath material is plasticized and extruded at temperatures of 155°C in zone one, 165°C in zone two, 175°C in zone three, and 180°C at the die head of the extruder. Simultaneously, the flexible intermediate layer material is extruded at 165°C. The two materials are fused together through the die head and wrapped around the core. After cooling and shaping, the finished cable is obtained.

[0040] This cable employs a 20-strand soft-annealed tin-plated copper inner layer and a 28-strand high-strength tin-plated copper alloy outer layer, twisted in opposite directions and subjected to continuous online annealing at 380°C. This process allows the inner layer to effectively absorb energy through plastic elongation during repeated bending, while the outer layer provides stable mechanical support. The reverse twisting structure suppresses conductor loosening, thus maintaining an extremely low rate of change in conductor resistance during dynamic bending. Insulation layer 2 utilizes a 14Mrad irradiation crosslinking process to form a three-dimensional network structure of low-smoke halogen-free polyolefin material, endowing it with excellent heat deformation resistance and electrical stability. Plasma treatment significantly enhances the surface energy of insulation layer 2, ensuring a robust interface with the subsequent flexible interlayer. The outer sheath is achieved through a 155℃ intensive mixing and double-layer co-extrusion process. In this process, silane-coupling agent-treated flake talc and chopped glass fibers are uniformly dispersed within the TPO / EVA matrix. The flake structure of the talc enhances the sheath's rigidity, dimensional stability, and barrier properties, while the chopped glass fibers strengthen tensile strength and creep resistance. Together, they enable the sheath to maintain flexibility while exhibiting excellent tear resistance, abrasion resistance, and weather resistance. This cable can withstand over 10,000 unidirectional bending tests in environments ranging from -40℃ to 90℃ without structural damage, making it suitable for long-term operation of high-frequency tracking brackets.

[0041] Example 2 This embodiment provides a bending-resistant and highly wear-resistant cable suitable for photovoltaic tracking brackets in cold, windy, and sandy environments. The inner layer of the conductor core 1 uses 18 strands of annealed copper wire with a diameter of 0.14 mm twisted in the right direction, while the outer layer uses 32 strands of high-strength, tough copper wire with a diameter of 0.08 mm twisted in the left direction. The insulation layer 2 is made of silicone rubber material, extruded to a thickness of 1.0 mm, and then cross-linked and cured through a hot air vulcanization channel. The surface of the cross-linked insulation layer is treated with a flame treatment process to improve adhesion. The flexible intermediate layer 4 is made of thermoplastic polyurethane material with a Shore A hardness of 55. The key to the preparation of the outer sheath material lies in the pretreatment of the filler: 20 parts by weight of flake talc powder with a particle size D50 of 8 μm and 8 parts by weight of short glass fibers with a length of 150 μm are preheated in a high-speed mixer at 100°C, followed by spraying with a solution containing a silane and titanate composite coupling agent. After thorough stirring and coating, the mixture is dried to obtain an activated composite mineral filler. The filler, along with 85 parts by weight of polyolefin thermoplastic elastomer, 10 parts by weight of ethylene-vinyl acetate copolymer, 2 parts by weight of antioxidant and light stabilizer compound system, and 10 parts by weight of phosphorus-nitrogen intumescent flame retardant, were melt-blended and granulated in an internal mixer. During co-extrusion molding, to improve the dispersibility of the filler in the matrix, the extrusion temperature of each section of the sheath material was increased by about 5°C compared to the conventional method. The flexible intermediate layer 4 was co-extruded simultaneously with it, ultimately producing a cable with excellent low-temperature resistance and wind and sand abrasion resistance.

[0042] The cable conductor employs a reverse-stranded design with an inner layer of 18-strand annealed copper wire and an outer layer of 32-strand high-strength, tough copper wire, ensuring conductivity while enhancing the overall mechanical strength of the conductor. The insulation layer uses silicone rubber and undergoes hot air vulcanization cross-linking, maintaining elasticity even at -40℃ and preventing embrittlement and cracking. Flame treatment generates active groups on the insulation surface, effectively improving the adhesion reliability with the thermoplastic polyurethane flexible interlayer. In the preparation of the outer sheath material, the composite mineral filler underwent pretreatment: flake talc powder and chopped glass fibers were mixed at high speed at 100℃ and sprayed with a silane / titanium ester composite coupling agent solution. This process significantly enhanced the interfacial bonding force between the filler and the TPV / EVA matrix, fully utilizing the flake barrier effect of talc powder and the reinforcing effect of glass fiber. The co-extrusion temperature of the sheath was appropriately increased by 5℃ to ensure good processability and dispersibility under high filler content. The resulting cable sheath exhibits exceptional abrasion resistance and resistance to wind and sand erosion, while the addition of phosphorus-nitrogen flame retardants ensures flame-retardant safety. This cable is particularly suitable for tracking systems in desert photovoltaic power stations characterized by large diurnal temperature variations and frequent sandstorms, maintaining a service life of over 5,000 cycles of bending even in harsh environments.

[0043] Example 3 This embodiment provides a cost-effective and efficient bending-resistant cable suitable for low-to-medium frequency swing supports. The conductor core 1 consists of 24 strands of annealed tin-plated copper wire with a diameter of 0.10 mm twisted in a right-hand direction as the inner layer, and 25 strands of tin-plated copper alloy wire with a diameter of 0.12 mm twisted in a left-hand direction as the outer layer. The insulation layer 2 is made of irradiated cross-linked low-smoke halogen-free polyolefin material. After extrusion to a thickness of 0.7 mm, it is cross-linked by irradiation with a dose of 15 Mrad. To simplify the process, the additional surface treatment step is omitted. The flexible intermediate layer 4 is made of styrene-based thermoplastic elastomer with a Shore A hardness of 70. The outer sheath layer 3 is composed of 75 parts by weight of polyolefin thermoplastic elastomer, 20 parts by weight of ethylene-vinyl acetate copolymer, 18 parts by weight of composite mineral filler, including 12 parts of modified flake talc and 6 parts of chopped glass fiber, as well as 1 part of antioxidant and 12 parts of aluminum hydroxide flame retardant. All components are blended and then granulated at a relatively reduced process temperature to save energy. During the co-extrusion coating stage, the extrusion temperature of the sheath material is controlled within the range of 170-180℃, while the temperature of the flexible interlayer material is controlled at around 160℃. Both are directly co-extruded onto the insulation layer, and the finished product is obtained after cooling. This solution achieves significant control over production costs by optimizing material ratios and reducing processing requirements while maintaining the core performance structure.

[0044] The cable conductor employs a reverse-stranded structure of 24 strands of annealed tin-plated copper wire and 25 strands of tin-plated copper alloy wire, providing good flexibility and fatigue resistance without excessively pursuing fine individual wires. The insulation layer utilizes a 15Mrad irradiation cross-linking process to form a stable cross-linked network. Although no additional surface treatment is performed, sufficient interfacial bonding is achieved during co-extrusion thanks to the slight tackiness of the irradiated material surface and the flexible interlayer of a styrene-based thermoplastic elastomer. The outer sheath material achieves energy-efficient production by reducing processing temperature, and the total amount of composite mineral filler in its formulation is reduced to 18 parts, lowering raw material costs while maintaining reinforcement. The addition of aluminum hydroxide flame retardant meets basic flame retardant requirements. This simplified process route demonstrates that the core architecture of this invention—heterogeneous conductor, flexible interlayer, and composite mineral filler-reinforced sheath—still imparts significantly superior bending fatigue resistance to the cable compared to traditional photovoltaic cables, even under moderately relaxed process conditions. This cable can stably withstand repeated bending at least six times its outer diameter under normal climatic conditions, providing a cost-effective solution for cost-sensitive low-to-medium dynamic frequency applications.

[0045] The working principle of this invention to improve the bending resistance of cables is as follows: The conductor adopts a reverse stranding structure of "soft inside, hard outside". When the cable bends, the inner annealed copper wire located inside the center of curvature undergoes controlled plastic elongation due to its high elongation, acting as an "energy-absorbing core" to dissipate most of the bending strain energy. Simultaneously, the outer high-strength copper alloy wire located on the outside bears the main tensile stress due to its high modulus, acting like a skeleton to constrain excessive deformation of the conductor as a whole. The opposite stranding directions of the inner and outer layers create a self-locking effect, preventing structural loosening during bending and ensuring that the conductor maintains structural integrity and electrical continuity even after repeated bending. The flexible intermediate layer between the insulation layer and the outer sheath is a key functional interface layer. Its material hardness is between the rigidity of the insulation layer and the reinforcing rigidity of the outer sheath. During bending, this layer undergoes elastic deformation, acting as an elastic gasket. It transforms the localized concentrated shear stress on the surface of the insulation layer into its own uniform compressive-tensile deformation, which is then gently transferred to the outer sheath. This prevents the initiation of microcracks in the brittle insulation material and the hard friction between the rigid sheath and the insulation layer. The outer sheath does not solely pursue high elasticity but is reinforced through a composite of flake talc and chopped glass fibers. The flake talc is parallel-oriented in the matrix, forming a physical barrier that improves the sheath's puncture resistance, dimensional stability, and environmental barrier properties. The chopped glass fibers are uniformly dispersed in the matrix, acting as micro-reinforcements that significantly enhance the material's tensile strength, creep resistance, and fatigue resistance. The synergistic effect of the two fillers allows the sheath to provide sufficient support to prevent excessive deformation when subjected to repeated bending, while also inhibiting crack propagation through the bridging effect between the matrix elasticity and the fibers, exhibiting excellent crack resistance and wear resistance.

[0046] Therefore, this invention employs the aforementioned anti-bending photovoltaic electrical cable and its manufacturing method. Through a unique reverse-stranded heterogeneous conductor structure, it utilizes an inner layer of high-ductility copper wire to absorb deformation energy and an outer layer of high-strength material to provide support. Combined with reverse stranding to suppress structural loosening, the cable can withstand over 10,000 unidirectional or 5,000 reciprocating bends under simulated tracking bracket conditions, with extremely low conductor resistance change rate, fundamentally ensuring long-term stable electrical performance of the dynamic connection. The added flexible intermediate layer serves as a mechanical transition zone; its moderate hardness effectively absorbs and disperses the shear stress between the insulation layer and the rigid sheath layer. Combined with insulation layer surface treatment and co-extrusion processes, a strong physical bond between the layers is achieved, completely avoiding insulation damage or interlayer delamination caused by stress concentration. The outer sheath is made of a weather-resistant elastomer composite material reinforced with specific composite mineral fillers. Flaky talc enhances the sheath's rigidity, dimensional stability, and barrier properties, while chopped glass fiber significantly enhances tensile strength and creep resistance. The two components work synergistically to give the sheath excellent tear resistance, abrasion resistance, scratch resistance, and low permanent deformation rate, while maintaining necessary flexibility and excellent UV and high / low temperature resistance, fully meeting the requirements for long-term dynamic outdoor use. The processes involved, such as conductor continuous annealing, insulation irradiation crosslinking, filler pretreatment, multi-layer co-extrusion, and surface treatment, are all innovative combinations and parameter optimizations of mature technologies. The production process is smooth, quality control points are clearly defined, and it possesses good feasibility for large-scale production.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A bending-resistant electrical cable for photovoltaic applications, characterized in that, It includes, from the inside out, the following components arranged sequentially: conductor core (1), insulation layer (2), flexible intermediate layer (4), and outer sheath layer (3); The conductor core (1) is formed by stranding at least two layers of metal wires in opposite directions, wherein the inner layer of metal wire is annealed copper wire or annealed tin-plated copper wire, and the outer layer of metal wire is tin-plated copper alloy wire or tough copper wire with a tensile strength of not less than 350MPa. The insulating layer (2) covers the outside of the conductor core (1); The flexible intermediate layer (4) is wrapped around the outside of the insulating layer (2). Its material is a thermoplastic elastomer with a Shore A hardness of 50-70 degrees. The thermoplastic elastomer is selected from at least one of thermoplastic polyurethane, polyester elastomer or styrene elastomer. The outer sheath layer (3) covers the outside of the flexible intermediate layer (4). Its material is a weather-resistant elastomer composite material, which includes, by weight: 70-90 parts of polyolefin thermoplastic elastomer, 10-20 parts of ethylene-vinyl acetate copolymer, 15-30 parts of composite mineral filler, 1-2 parts of antioxidant, and 0.5-1.5 parts of light stabilizer. The composite mineral filler is a mixture of flaky talc powder modified with silane coupling agent and chopped glass fiber, with a weight ratio of (1.5-3):

1.

2. The bending-resistant photovoltaic electrical cable according to claim 1, characterized in that, The stranding structure of the conductor core (1) is as follows: the inner layer consists of 15-25 strands of annealed copper wire with a diameter of 0.10-0.16 mm stranded in the first direction, with a pitch ratio of 12-16; the outer layer consists of 20-35 strands of tin-plated copper alloy wire with a diameter of 0.08-0.13 mm stranded in the opposite direction, with a pitch ratio of 10-14.

3. The bending-resistant photovoltaic electrical cable according to claim 1, characterized in that, In the composite mineral filler of the outer sheath layer (3), the particle size D50 of the flaky talc powder is 5-15μm and the aspect ratio is greater than 10; the length of the short-cut glass fiber is 100-300μm and the diameter is 10-15μm.

4. The bending-resistant photovoltaic electrical cable according to claim 1, characterized in that, The weather-resistant elastomer composite material of the outer sheath layer (3) also contains 5-12 parts by weight of halogen-free flame retardant, which is at least one of aluminum hydroxide, magnesium hydroxide or phosphorus-nitrogen flame retardant.

5. The bending-resistant photovoltaic electrical cable according to claim 1, characterized in that, The insulation layer (2) is an irradiated cross-linked low-smoke halogen-free polyolefin insulation layer with a thickness of 0.6-1.0 mm; the flexible intermediate layer (4) has a thickness of 0.2-0.4 mm, and its material and the material of the outer sheath layer (3) can form a physical fusion bonding interface during co-extrusion.

6. A method for preparing a bend-resistant photovoltaic electrical cable as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Conductor stranding and annealing: The inner copper wire and the outer copper alloy wire are stranded in opposite directions to form a conductor core (1) by a high-speed stranding machine, and the conductor core (1) is continuously annealed online at a temperature of 300-450℃. S2, Insulation layer extrusion and crosslinking: The conductor core (1) obtained in step S1 is extruded with insulating material through an extruder to form an insulation layer (2), and then immediately enters an electron irradiation crosslinking device for crosslinking and curing; S3, Co-extrusion of flexible intermediate layer and outer sheath layer: a) Preparation of outer sheath material: Polyolefin thermoplastic elastomer and ethylene-vinyl acetate copolymer are melt-blended in an internal mixer at 140-160℃, and then pretreated composite mineral filler, antioxidant and light stabilizer are added. After uniform mixing, the mixture is granulated. b) Using a double-layer co-extrusion machine, the wire core obtained in step S2 is preheated and then extruded simultaneously with the flexible intermediate layer (4) material and the outer sheath material particles obtained in step a). The extrusion temperature of the flexible intermediate layer (4) is 10-20°C lower than that of the outer sheath layer (3). The core is formed integrally by the co-extrusion die. S4. Cooling and post-processing: The co-extruded cable is water-cooled or air-cooled for shaping, and then equilibrated at room temperature for more than 24 hours after winding.

7. The method for preparing a bending-resistant photovoltaic electrical cable according to claim 6, characterized in that, In step S2, the electron irradiation crosslinking dose is 12-16 Mrad.

8. The method for preparing a bending-resistant photovoltaic electrical cable according to claim 6, characterized in that, In step S3a), the pretreatment method for the composite mineral filler is as follows: preheat the flake talc powder and chopped glass fiber in a high-speed mixer to 90-110°C, add 1.0-2.0% of the total weight of the filler in silane coupling agent ethanol solution, stir at high speed for 10-20 minutes to make it uniformly coated, and then dry.

9. The method for preparing a bending-resistant photovoltaic electrical cable according to claim 6, characterized in that, In step S3b), the temperature of each section of the extruder for the outer sheath layer (3) material is set as follows: Zone 1 150-160℃, Zone 2 160-170℃, Zone 3 170-180℃, and the die head 175-185℃.

10. A method for preparing a bending-resistant photovoltaic electrical cable according to claim 6, characterized in that, After the irradiation crosslinking is completed in step S2, the surface of the insulating layer (2) is subjected to plasma surface treatment or flame treatment at a linear speed of 20-40 m / min.

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