A double-layer insulated photovoltaic cable with synergistic protection effect and a preparation method thereof

Abstract

This invention discloses a double-insulated photovoltaic cable with synergistic protection effect and its preparation method, belonging to the field of wire and cable technology. The cable includes a conductor, a double insulation layer, and a sheath layer. The double insulation layer consists of an inner electrical protection insulation layer and an outer environmental protection insulation layer. The inner insulation layer uses a polyolefin composite material containing rutile nano-titanium dioxide and crosslinking agents to provide high and stable insulation resistance and suppress potential-induced decay of the system. The outer insulation layer uses a polyolefin elastomer containing weather-resistant additives to block ultraviolet rays, water vapor, and oxygen. A tin-bismuth alloy layer is plated on the conductor surface to suppress ion migration. This invention solves the industry problem of single-layer insulation structures being unable to simultaneously achieve high PID resistance and long-term weather resistance through functional layer design and synergistic processes. The resulting cable has the advantages of stable insulation performance, excellent weather resistance, and strong interlayer bonding, which can significantly improve the long-term reliability of photovoltaic systems.

Description

Technical Field

[0001] This invention relates to the field of wires and cables, and in particular to a double-insulated photovoltaic cable with synergistic protection effect and its preparation method. Background Technology

[0002] Photovoltaic DC cables are core transmission components connecting photovoltaic modules, combiner boxes, and inverters. They are exposed to harsh outdoor environments for extended periods, simultaneously enduring strong ultraviolet radiation, high and low temperature cycling (-40℃~90℃), high humidity, diurnal temperature fluctuations, and high DC voltage (up to 1500V). The long-term stability of their insulation performance directly determines the power generation efficiency and operational safety of the photovoltaic system.

[0003] In existing technologies, photovoltaic DC cables mostly employ a single-layer cross-linked polyolefin (XLPO, EVA, etc.) insulation structure. This structure presents a fundamental contradiction in its material formulation design. To improve resistance to potential-induced degradation (PID), extremely high volume resistivity and purity of the material are required, which typically necessitates reducing or avoiding the introduction of polar additives. However, to ensure long-term weather resistance, sufficient amounts of UV absorbers, antioxidants, and other polar additives must be added to resist environmental corrosion. This contradiction leads to the single-layer insulation structure becoming a performance compromise, and is one of the core reasons why the system frequently experiences PID effects and its actual lifespan often falls short of the designed 25-year lifespan.

[0004] While existing technologies involve research on multi-layered insulated cables, they are mostly simple physical superpositions of different materials, lacking a functional synergy design approach, and generally suffer from insufficient interlayer bonding and easy peeling. Therefore, developing a highly reliable photovoltaic cable that can completely resolve these issues and achieve synergistic protection has become an urgent industry need. Summary of the Invention

[0005] The purpose of this invention is to provide a double-insulated photovoltaic cable with synergistic protection effect and its preparation method, so as to solve the problems in the background art.

[0006] To achieve the above objectives, the present invention provides a double-insulated photovoltaic cable with synergistic protection effect, comprising a conductor, an insulation layer, and a sheath layer. The insulation layer is a double-layer composite structure, comprising an inner insulation layer directly covering the surface of the conductor and an outer insulation layer covering the outer surface of the inner insulation layer. The inner insulation layer is made of an electrical protection composite material, and the outer insulation layer is made of an environmental protection composite material.

[0007] Preferably, the electrical protection composite material comprises the following components by weight: The matrix resin comprises 100 parts, 3-8 parts of rutile nano-titanium dioxide modified with silane coupling agent, 0.5-1.5 parts of main antioxidant, and 0.8-1.2 parts of crosslinking aid; the nano-titanium dioxide has a particle size of 20-50 nm, and the amount of silane coupling agent added is 1-3% of the weight of nano-titanium dioxide.

[0008] Preferably, the matrix resin is one or a mixture of ethylene-vinyl acetate copolymer and low-density polyethylene; the VA content of the ethylene-vinyl acetate copolymer is 25%~30%, and the melt index is 2~4 g / 10min; the main antioxidant is a hindered phenolic antioxidant.

[0009] Preferably, the crosslinking aid is trimethylolpropane trimethacrylate.

[0010] Preferably, the environmental protection composite material comprises the following components by weight: 100 parts of polyolefin elastomer, 0.5-1.5 parts of ultraviolet absorber, 0.3-0.8 parts of light stabilizer, and 1-3 parts of polysiloxane hydrophobic agent; The polyolefin elastomer is an ethylene-octene copolymer with an octene content of 20% to 30%.

[0011] Preferably, the ultraviolet absorber is a benzotriazole or benzophenone; the light stabilizer is a hindered amine light stabilizer.

[0012] Preferably, the environmental protection composite material also includes 0.3 to 0.8 parts of auxiliary antioxidant, which is a phosphite antioxidant.

[0013] Preferably, the conductor is a stranded soft copper wire with a tin-bismuth alloy layer plated on its surface; the mass percentage of bismuth in the tin-bismuth alloy layer is 2% to 5%, and the thickness of the alloy layer is 1 to 3 μm.

[0014] Preferably, the thickness of the inner insulating layer accounts for 40% to 60% of the total thickness of the insulating layer; the total thickness of the insulating layer is 0.8 to 1.5 mm.

[0015] This invention provides a method for preparing the above-mentioned double-insulated photovoltaic cable with synergistic protection effect, comprising the following steps: S1. Conductor pretreatment: The conductor is subjected to acid electroplating to coat a tin-bismuth alloy layer, and then washed and dried before use. S2, Double-layer co-extrusion insulation: After drying the inner and outer insulation materials separately, they are fed into two single-screw extruders and simultaneously melted and extruded through a double-layer co-extrusion die, and then coated onto the pre-treated conductor to form a double-layer insulated wire core. S3. Segmented irradiation crosslinking: The double-insulated wire core is crosslinked by irradiation in two stages using an electron beam. The first stage of irradiation dose is 30% to 40% of the total irradiation dose, and the second stage of irradiation dose is 60% to 70% of the total irradiation dose; the total irradiation dose is 12 to 18 Mrad. S4. Sheath Extrusion and Post-processing: The sheath is extruded onto the irradiated cross-linked insulated core, and after segmented cooling, traction, winding and online testing, the finished cable is obtained.

[0016] Preferably, in step S1, the process parameters for acid electroplating are as follows: the acid electroplating solution is a methanesulfonate system, and the electroplating solution contains 20~40 g / L of Sn. 2+ Bi 1~5g / L 3+ The electroplating temperature is 25~30℃, and the current density is 10~15A / dm³. 2 The electroplating time is 3-5 minutes.

[0017] Preferably, in step S2, the extrusion temperature of the inner insulating material is controlled to be 150~170℃, the extrusion temperature of the outer insulating material is controlled to be 130~150℃, and the extrusion temperature of the inner layer is 5~20℃ higher than that of the outer layer. The drying temperature of the inner and outer insulating materials is 80~100℃, and the drying time is 4~6h; the flow channel of the double-layer co-extrusion die has a gradient structure, which is used to guide the inner and outer melts to merge smoothly.

[0018] Preferably, in step S3, by controlling the electron beam energy, beam current and linear velocity, the crosslinking degree of the outer insulating layer after the first irradiation is 60%~70%, and the crosslinking degree of the inner insulating layer after the second irradiation is 85%~95%.

[0019] Preferably, through the above preparation method, the inner insulating layer and the outer insulating layer are melted and fused together through a double-layer co-extrusion process to form a gapless interfacial fusion zone with a thickness of 5~10μm, thus constituting a composite insulation system with synergistic effects of electrical protection and environmental protection.

[0020] Therefore, the double-insulated photovoltaic cable with synergistic protection effect and its preparation method of the present invention have the following beneficial effects: (1) In this invention, the outer insulation layer serves as an environmental barrier, and its highly efficient weather-resistant system effectively blocks ultraviolet radiation and water vapor penetration, providing a stable operating microenvironment for the inner insulation layer. The inner insulation layer serves as the electrical core, and its highly cross-linked dense network structure and functional nanofillers work synergistically to maintain ultra-high and stable insulation resistance under harsh DC voltages, significantly suppressing charge accumulation and the risk of system potential-induced decay (PID). Together, they ensure the reliability of the cable under long-term outdoor complex operating conditions from both physical isolation and electrical stability perspectives.

[0021] (2) The material selection based on the polyolefin family provides a thermodynamic basis for interfacial melting; the customized die head and temperature gradient process promote the interdiffusion of molecular chains at the interface; the segmented irradiation process achieves differentiated crosslinking degrees between the inner and outer layers while forming an interpenetrating crosslinking network in the interface region. These measures work together to enable the double insulation layer to exhibit excellent interfacial adhesion under thermal and mechanical stress, avoiding the problem of interlayer delamination during long-term use.

[0022] (3) The tin-bismuth alloy coating directly inhibits the deposition of copper ions from the conductor surface and the growth of "tin whiskers"; the outer insulating layer acts as the first barrier to prevent the intrusion of external moisture; the highly cross-linked and dense structure of the inner insulating layer further blocks the longitudinal migration of ions. This strategy of "source inhibition + multi-layer barrier" greatly reduces the risk of metal ion contamination of the insulating layer.

[0023] 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

[0024] Figure 1 This is a schematic diagram of the cross-sectional structure of a double-insulated photovoltaic cable according to an embodiment of the present invention; Figure 2 This is a process flow diagram of an embodiment of the present invention; Figure label: 1. Conductor; 2. Inner insulating layer; 3. Outer insulating layer; 4. Sheath layer; 5. Interfacial fusion zone. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0027] This invention provides a double-insulated photovoltaic cable with synergistic protection effect, such as... Figure 1 As shown, it includes a conductor 1, an insulation layer and a sheath layer 4. The insulation layer is a double-layer composite structure and is the core structure, including an inner insulation layer 2 that is directly covered on the surface of the conductor and an outer insulation layer 3 that is covered on the outer surface of the inner insulation layer 2. The thickness of the inner insulation layer 2 accounts for 40% to 60% of the total thickness of the insulation layer. The total thickness of the insulation layer is 0.8 to 1.5 mm.

[0028] The inner insulation layer 2 is made of an electrical protection composite material. Its core function is to maintain ultra-high and stable insulation resistance under harsh operating conditions, suppress charge accumulation, and thus reduce the risk of potential-induced degradation (PID) in photovoltaic systems caused by cable insulation deterioration. The electrical protection composite material comprises the following components by weight: The composition comprises 100 parts of matrix resin, 3-8 parts of rutile nano-titanium dioxide surface-modified with silane coupling agent, 0.5-1.5 parts of main antioxidant, and 0.8-1.2 parts of crosslinking aid; the particle size of the nano-titanium dioxide is 20-50 nm, and the amount of silane coupling agent added is 1-3% of the weight of the nano-titanium dioxide. By selecting the rutile crystal form with low photocatalytic activity and modifying it with silane coupling agent, its potential photocatalytic activity can be effectively suppressed, ensuring that it only serves as a functional filler to improve insulation resistance and corona resistance in the inner layer environment.

[0029] The matrix resin is one or a mixture of ethylene-vinyl acetate copolymer, low-density polyethylene, or both; the VA content of the ethylene-vinyl acetate copolymer is 25%~30%, and the melt index is 2~4 g / 10min; this type of resin has excellent insulation properties and radiation crosslinking adaptability. The main antioxidant is a hindered phenolic antioxidant.

[0030] The crosslinking aid is trimethylolpropane trimethacrylate (TMPTMA).

[0031] After the inner insulating layer 2 is cross-linked by irradiation, the degree of cross-linking is controlled at 85%~95%, forming a dense three-dimensional network structure.

[0032] The outer insulation layer 3 is made of environmental protection composite material. Its core function is to effectively block ultraviolet rays, water vapor and oxygen, providing a stable operating microenvironment for the inner insulation layer 2.

[0033] Environmental protection composite materials, by weight, include the following components: 100 parts of polyolefin elastomer, 0.5-1.5 parts of ultraviolet absorber, 0.3-0.8 parts of light stabilizer, and 1-3 parts of polysiloxane hydrophobic agent.

[0034] The polyolefin elastomer is an ethylene-octene copolymer with an octene content of 20% to 30%. The ethylene-octene copolymer of the outer insulating layer 3 and the matrix resin of the inner insulating layer 2 both belong to the polyolefin family, have similar molecular chain structures, and have good thermodynamic compatibility. This is the material science basis for forming a strong interfacial melting zone through co-extrusion.

[0035] The ultraviolet absorber is a benzotriazole or benzophenone derivative; the light stabilizer is a hindered amine light stabilizer. The environmental protection composite material also includes 0.3 to 0.8 parts of auxiliary antioxidant, which is a phosphite antioxidant.

[0036] After the outer insulating layer 3 is cross-linked by irradiation, the degree of cross-linking is controlled at 60%~70%, which takes into account both excellent flexibility and weather resistance.

[0037] Conductor 1 is a stranded soft copper wire with a tin-bismuth alloy layer plated on its surface; the mass percentage of bismuth in the tin-bismuth alloy layer is 2%~5%, and the thickness of the alloy layer is 1~3μm. This alloy layer can effectively inhibit the growth of "tin whiskers", improve the resistance to damp heat aging, and prevent copper ions from migrating to the insulating layer.

[0038] This invention provides a method for preparing the aforementioned double-insulated photovoltaic cable with synergistic protection effect, such as... Figure 2 As shown, it includes the following steps: S1. Pretreatment of Conductor 1: Conductor 1 is subjected to acid electroplating to deposit a tin-bismuth alloy layer. After washing and drying, it is ready for use. The process parameters for acid electroplating are as follows: the acid electroplating solution is a methanesulfonate system containing 20~40g / L of Sn. 2+ Bi 1~5g / L 3+ The electroplating temperature is 25~30℃, and the current density is 10~15A / dm³. 2 The electroplating time is 3-5 minutes.

[0039] S2. Double-layer co-extrusion insulation: The inner and outer insulation materials are dried separately at 80-100℃ for 4-6 hours. After drying, they are fed into two single-screw extruders and simultaneously melt-extruded through a double-layer co-extrusion die, coating the pre-treated conductor to form a double-layer insulated wire core. The extrusion temperature of the inner insulation material is controlled at 150-170℃, and the extrusion temperature of the outer insulation material is controlled at 130-150℃, with the inner layer extrusion temperature being 5-20℃ higher than the outer layer. This temperature gradient design ensures that the inner layer material is fully plasticized and tightly bonded to the conductor, while allowing the outer layer material to merge with the inner melt at a lower temperature. This promotes the interfacial melting of molecular chains to form an interfacial melting zone and protects the outer anti-aging additives from thermal decomposition.

[0040] The dual-layer co-extrusion die features a gradient flow channel structure. The height and width of the inner and outer flow channels smoothly taper along the extrusion direction before the confluence point, with a taper ratio (inlet section / outlet section) of (2~3):1. The flow channel ends converge at an acute angle of 10~30°, forming a low-shear stress confluence region with a length of not less than 5mm. This structural parameter design is based on mold flow analysis optimization of the melt rheological properties of the inner and outer composite materials, aiming to guide the smooth confluence of the melt and promote the interfacial molecular chain melting.

[0041] S3. Segmented Irradiation Crosslinking: A two-stage irradiation crosslinking process is performed on the double-insulated wire core using an electron beam generated by an electron accelerator with an energy of 1.5~3.0 MeV. Precise control of the differentiated crosslinking degree between the two insulation layers is achieved by coordinating the beam current intensity and the traction speed of the wire core. The first stage uses a lower irradiation dose (e.g., 30%~40% of the total dose) and an appropriate traction speed to allow the outer insulation layer 3 to preferentially reach a crosslinking degree of 60%~70% and achieve initial shaping. The second stage uses a higher irradiation dose (the remaining dose) and a lower traction speed than the first stage (or through multiple irradiations) to fully crosslink the inner insulation layer 2 to 85%~95%.

[0042] The aforementioned differentiated crosslinking is achieved based on: First, the highly efficient crosslinking aid (TMPTMA) in the inner layer formulation significantly enhances its crosslinking reactivity and efficiency compared to the outer layer material without a dedicated crosslinking aid; second, the segmented irradiation process prioritizes moderate crosslinking and shaping of the outer layer with a lower dose, followed by a higher dose to ensure deep crosslinking of the inner layer. The relatively low crosslinking degree requirement of the outer layer material is largely met in the first stage of irradiation, while subsequent irradiations primarily serve the goal of achieving a high degree of crosslinking in the inner layer.

[0043] S4. A halogen-free flame-retardant polyolefin sheath is extruded onto the irradiated cross-linked insulated core, and the finished cable is obtained after segmented cooling, traction, winding and online testing.

[0044] The above technical solution will be explained below with specific examples.

[0045] Example 1 This embodiment prepares a 4mm 2 For a double-insulated photovoltaic cable with a rated voltage of 1500V, the selected materials, by weight, are as follows: Inner insulation layer: EVA (VA 28%, MI=3), 100 parts; KH-550 modified rutile nano TiO2 (40nm), 5 parts; antioxidant 1076, 1 part; trimethylolpropane trimethacrylate, 1.0 part.

[0046] Outer insulation layer: 100 parts of ethylene-octene copolymer (octene content 25%); 1 part of benzotriazole UV absorber UV-327; 0.5 parts of light stabilizer 622; 2 parts of hydroxyl silicone oil; and 0.5 parts of antioxidant 168.

[0047] The specific steps are as follows: S1. First, select 56 wires. 0.30mm soft copper wire stranded into 4mm 2 Conductor. Subsequently, an acidic electroplating process (methanesulfonic acid system plating solution: Sn) is employed. 2+Add 30 g / L of Bi in the form of stannous methanesulfonate. 3+ Added at 3 g / L in the form of bismuth methanesulfonate at 28 °C; current density 12 A / dm³ 2 The process involves coating a 2μm thick Sn-3%Bi alloy layer with deionized water (4 min) and then drying at 80℃ for 12 min.

[0048] S2. First, prepare the inner layer insulation masterbatch and the outer layer insulation masterbatch separately, specifically as follows: 1) Preparation of inner layer insulation masterbatch: According to the formula, ethylene-vinyl acetate copolymer (EVA) particles, rutile nano-titanium dioxide modified with KH-550, and antioxidant 1076 are added to a high-speed mixer and premixed at a low temperature (≤60℃) to prevent premature reaction of the crosslinking aid. Subsequently, the premix is ​​fed into a twin-screw extruder and melt-blended at a temperature range of 120-160℃ and a screw speed of 250 r / min, while simultaneously injecting liquid crosslinking aid trimethylolpropane trimethacrylate through a side-feed system. Vacuum exhaust is activated during extrusion to remove low-molecular-weight volatiles. The melt is water-cooled and pelletized to obtain the inner layer insulation masterbatch.

[0049] 2) Preparation of outer layer insulation masterbatch: Polyolefin elastomer (POE) particles, UV absorber UV-327, light stabilizer 622, and antioxidant 168 are added to a high-speed mixer according to the specified ratio. Hydrophobic silicone oil is premixed with a small amount of POE resin and then added. Premixing is performed at a low temperature (≤50℃) to protect the heat-sensitive weather-resistant additives. Subsequently, the premix is ​​fed into a twin-screw extruder at 180 r / min, and gently melt-blended within a low temperature range of 100~145℃ to avoid additive decomposition. Vacuum degassing is also required during the extrusion process. The melt is air-cooled and pelletized (this helps slow down silicone oil migration) to obtain the outer layer insulation masterbatch.

[0050] The inner and outer insulating masterbatches prepared above were placed in a hot air drying oven. The inner layer particles were dried at 90°C for 4 hours, and the outer layer particles were dried at 80°C for about 4 hours, so that the moisture content of the particles was reduced to below 0.05% for later use.

[0051] The dried inner and outer insulating masterbatches were fed into the hoppers of two single-screw extruders, respectively. The inner layer was extruded at 160℃ and the outer layer at 140℃, through a double-layer co-extrusion die at a linear speed of 8 m / min. The inner layer thickness was 0.5 mm and the outer layer thickness was 0.6 mm. The interfacial melting zone of the double insulation layers can buffer the stress caused by the crosslinking gradient through molecular chain entanglement. After 100 cycles of thermal cycling at -40℃ and 85℃, the interlayer peel strength retention rate was ≥90%, with no cracking.

[0052] S3. Segmented Irradiation Crosslinking: Two-stage irradiation crosslinking was performed using a 2.0 MeV electron accelerator. The process parameters were: first stage irradiation dose 6 Mrad, linear velocity 12 m / min; second stage irradiation dose 9 Mrad, linear velocity 8 m / min. The total absorbed dose was 15 Mrad. The degree of crosslinking was determined using solvent extraction (referring to GB / T2951.41-2008), and the crosslinking degree of the inner layer was found to be 90%, and that of the outer layer was 65%.

[0053] S4. Sheath Extrusion: Extrude a halogen-free flame-retardant polyolefin sheath (0.8mm thick) at an extrusion temperature of 150℃; perform segmented cooling, first with 25℃ warm water spray cooling, then with 8℃ cold water tank cooling, the total length of the cooling water tank is about 40 meters, and the total cooling time is about 8 minutes at a traction speed of 5m / min; then rewind, with a rewind tension of 80N; online testing of parameters such as insulation resistance and withstand voltage performance, and after passing the test, put it into storage.

[0054] Comparative Example 1 This comparative example prepared a single-layer insulated photovoltaic cable of the same specifications. The conductor and sheath were the same as in Example 1. The insulation layer used a commercially available anti-PID crosslinked polyolefin insulation material (its matrix resin is EVA, it does not contain nano-titanium dioxide, and its nominal crosslinking degree is about 75%) that meets the requirements of TUV2Pfg1169 / 08.20 standard, with a thickness of 1.1 mm, and was crosslinked by a single irradiation (dose 15 Mrad). Other process parameters were the same as in Example 1.

[0055] The cables prepared in Example 1 and Comparative Example 1 were subjected to the following performance tests, and the test standards and conditions are as follows: PID test: Under the conditions of temperature 85℃, relative humidity 85%, and DC voltage -1000V, a bias voltage is applied to the insulated conductor for 1000 hours to test the insulation resistance retention rate.

[0056] UV aging: At a black panel temperature of (80±2)℃, using a UVA-340 lamp with an irradiance of 0.76W / (m²), the UV aging process was carried out. 2 After 3000 hours of exposure ( / nm), the elongation at break of the insulation layer was tested to determine its retention rate.

[0057] Humid heat aging: After aging for 3000 hours at 85℃ and 85% relative humidity, the tensile strength retention rate of the insulation layer was tested.

[0058] Insulation layer peel strength: After sampling, the layers are manually peeled to test the peel strength.

[0059] Copper ion content in the insulation layer: After 3000 hours of damp heat aging, insulation layer samples were digested and the copper ion content was determined by ICP-MS.

[0060] The test results are shown in Table 1.

[0061] Table 1: Performance Test Results

[0062] Example 2 In this embodiment, the following components are included by weight: Inner insulation layer: Low-density polyethylene (LDPE, density 0.920 g / cm³) 3 ), 100 parts; KH-550 modified rutile nano TiO2 (40nm), 3 parts; antioxidant 1076, 1 part; trimethylolpropane trimethacrylate, 1.0 part.

[0063] Outer insulation layer: 100 parts of ethylene-octene copolymer (octene content 25%); 1 part of benzophenone-based ultraviolet absorber UV-531; 0.5 parts of light stabilizer 770; 2 parts of hydroxyl silicone oil; and 0.5 parts of antioxidant 168.

[0064] The specific preparation steps are the same as in Example 1.

[0065] Example 3 The components used in this embodiment are the same as those in Example 2, and the preparation steps are the same. The only difference is that in step S3, the first irradiation dose is adjusted to 5.25 Mrad (accounting for 35% of the total dose of 15 Mrad), and the linear velocity is 12 m / min; the second dose is 9.75 Mrad, and the linear velocity is 8 m / min.

[0066] Example 4 The components used in this embodiment are the same as those in Example 1. The thickness of the double-layer insulation extrusion is adjusted so that the inner layer thickness is 0.44 mm and the outer layer thickness is 0.66 mm (total thickness 1.1 mm, with the inner layer accounting for 40%). The preparation steps are the same as in Example 1.

[0067] The products of Examples 2-4 were subjected to the same performance tests as those of Example 1. The results showed that the insulation resistance retention rate of all samples in the PID test was ≥82%, the mechanical property retention rate after UV / damp heat aging was ≥78%, and the interlayer peel strength was ≥7.5 N / cm, all of which were significantly better than Comparative Example 1.

[0068] Therefore, this invention provides a double-insulated photovoltaic cable with synergistic protective effects and its preparation method. Through functional layering and synergistic design, it achieves comprehensive performance that is difficult to achieve with a single insulation layer. Through material compatibility design and a double-layer co-extrusion-segmented irradiation process, it ensures the long-term robustness of the interlayer bond. Through the synergy between the conductor surface alloy plating and the double insulation, a complete ion migration barrier system is constructed. The prepared cable overcomes the technical bottleneck of traditional single-layer insulation structures in balancing anti-PID performance and long-term weather resistance. Under high accelerated aging conditions (such as PID, ultraviolet, and damp heat), the retention rate of key performance (insulation resistance, mechanical properties) is significantly better than that of conventional single-layer insulated cables, and the interlayer bond is strong, which can significantly improve the safety and power generation efficiency of photovoltaic power generation systems throughout their entire life cycle.

[0069] 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 double-insulated photovoltaic cable with synergistic protective effect, comprising a conductor, an insulation layer, and a sheath layer, characterized in that: The insulation layer is a double-layer composite structure, including an inner insulation layer directly covering the surface of the conductor and an outer insulation layer covering the outer surface of the inner insulation layer; the inner insulation layer is made of electrical protection composite material, and the outer insulation layer is made of environmental protection composite material.

2. A double insulated photovoltaic cable with synergistic protection effect according to claim 1, characterized in that, The electrical protection composite material comprises the following components by weight: The matrix resin comprises 100 parts, 3-8 parts of rutile nano-titanium dioxide modified with silane coupling agent, 0.5-1.5 parts of main antioxidant, and 0.8-1.2 parts of crosslinking aid; the nano-titanium dioxide has a particle size of 20-50 nm, and the amount of silane coupling agent added is 1-3% of the weight of nano-titanium dioxide.

3. A double insulated photovoltaic cable with a synergistic barrier effect according to claim 2, characterized in that: The matrix resin is one or a mixture of ethylene-vinyl acetate copolymer and low-density polyethylene; the VA content of the ethylene-vinyl acetate copolymer is 25%~30%, and the melt index is 2~4 g / 10min; the main antioxidant is a hindered phenolic antioxidant.

4. A double insulated photovoltaic cable with synergistic protection effect according to claim 1, characterized in that, The environmental protection composite material comprises the following components by weight: 100 parts of polyolefin elastomer, 0.5-1.5 parts of ultraviolet absorber, 0.3-0.8 parts of light stabilizer, and 1-3 parts of polysiloxane hydrophobic agent; The polyolefin elastomer is an ethylene-octene copolymer with an octene content of 20% to 30%.

5. A double insulated photovoltaic cable with synergic protection effect according to claim 1, characterized in that: The conductor is a stranded soft copper wire with a tin-bismuth alloy layer plated on its surface; the mass percentage of bismuth in the tin-bismuth alloy layer is 2% to 5%, and the thickness of the alloy layer is 1 to 3 μm.

6. A double insulated photovoltaic cable with synergic protection effect according to claim 1, characterized in that: The thickness of the inner insulating layer accounts for 40% to 60% of the total thickness of the insulating layer; the total thickness of the insulating layer is 0.8 to 1.5 mm.

7. A process for the preparation of a double-insulated photovoltaic cable with synergistic shielding effect according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Conductor pretreatment: The conductor is subjected to acid electroplating to coat a tin-bismuth alloy layer, and then washed and dried before use. S2, Double-layer co-extrusion insulation: After drying the inner and outer insulation materials separately, they are fed into two single-screw extruders and simultaneously melted and extruded through a double-layer co-extrusion die, and then coated onto the pre-treated conductor to form a double-layer insulated wire core. S3. Segmented irradiation crosslinking: The double-insulated wire core is crosslinked by irradiation in two stages using an electron beam. The first stage of irradiation dose is 30% to 40% of the total irradiation dose, and the second stage of irradiation dose is 60% to 70% of the total irradiation dose; the total irradiation dose is 12 to 18 Mrad. S4. Sheath Extrusion and Post-processing: The sheath is extruded onto the irradiated cross-linked insulated core, and after segmented cooling, traction, winding and online testing, the finished cable is obtained.

8. The method of claim 7, wherein: In step S1, the process parameters for acidic electroplating are: the electroplating solution contains 20-40 g / L of Sn. 2+ Bi 1~5g / L 3+ The electroplating temperature is 25~30℃, and the current density is 10~15A / dm³. 2 The electroplating time is 3-5 minutes.

9. The method of claim 7, wherein: In S2, the extrusion temperature of the inner insulating material is controlled to be 150~170℃, the extrusion temperature of the outer insulating material is controlled to be 130~150℃, and the extrusion temperature of the inner layer is 5~20℃ higher than that of the outer layer. The drying temperature of the inner and outer insulating materials is 80~100℃, and the drying time is 4~6h; the flow channel of the double-layer co-extrusion die has a gradient structure, which is used to guide the inner and outer melts to merge smoothly.

10. The preparation method according to claim 7, characterized in that: In S3, by controlling the electron beam energy, beam current and linear velocity, the cross-linking degree of the outer insulating layer after the first irradiation is 60%~70%, and the cross-linking degree of the inner insulating layer after the second irradiation is 85%~95%.

Images