A kind of photovoltaic cable

Abstract

The present invention relates to a photovoltaic cable, which comprises a conductor, an insulating layer and a sheath layer. The insulating layer is coated on the outer side of the conductor, and the sheath layer is coated on the outer side of the insulating layer. The material of the insulating layer comprises the following components by weight: 84-120 parts of a base resin, 110-170 parts of a flame retardant modifier, 1-5 parts of a charring agent, 0.5-2 parts of an antioxidant, 1-3 parts of a lubricant, 0.5-2 parts of a crosslinking agent, and 1-4 parts of a colorant. Among them, the base resin is composed of a first EVA resin, a second EVA resin, polyethylene and a polyolefin elastomer. The VA content in the first EVA resin is 17%-19%, and the VA content in the second EVA resin is 24%-28%. For the photovoltaic cable of the present invention, by adjusting the material ratio of the insulating layer, on the premise that the overall flame retardant performance of the photovoltaic cable meets the CPR flame retardant Dca grade, the flexibility is increased and the water absorption is reduced, and it can meet the UL 854 impact and rolling test and the AD8 waterproof test recognized by European customers.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cables, and particularly to a photovoltaic cable. Background Art

[0002] Photovoltaic power stations are used to convert solar energy into electrical energy, and photovoltaic cables are used to transmit the converted electrical energy. Photovoltaic power stations can be divided into distributed photovoltaic power stations and centralized photovoltaic power stations. Centralized photovoltaic power stations are usually set in areas with rich and stable solar energy resources such as desert areas, and the photovoltaic cables used in them are correspondingly set indoors or underground; while distributed photovoltaic power stations are usually set on the user side, such as on the surface of buildings, so the photovoltaic cables used in them are correspondingly set on the top or around the buildings.

[0003] Existing photovoltaic cables sold to Europe, such as conventional H1Z2Z2-K photovoltaic cables, are usually used in centralized photovoltaic power stations. Taking the H1Z2Z2-K photovoltaic cable as an example, it mainly includes a conductor, an insulating layer and a sheath layer. Among them, both the insulation and the sheath are produced using halogen-free, low-smoke, flame-retardant, irradiated cross-linked polyolefin materials (XLPO). Such photovoltaic cables usually only meet the requirements of single vertical combustion and low-smoke halogen-free in the EN 50618 standard; at the same time, the cable as a whole is hard and brittle and prone to cracking; in addition, the water absorption of the insulating layer and the sheath layer is relatively large.

[0004] When facing distributed photovoltaic power stations, due to the change in the use environment of the photovoltaic cable, the above-mentioned photovoltaic cable cannot meet the performance requirements of Europe for photovoltaic cables in terms of flame retardancy, impact and rolling resistance, and waterproofness. To sum up, it is urgent to develop a photovoltaic cable with better flame retardancy, impact and rolling resistance, and waterproofness. Summary of the Invention

[0005] For this reason, the technical problem to be solved by the present invention is to overcome the fact that the flame retardancy, impact and rolling resistance, and waterproofness of conventional photovoltaic cables cannot meet the requirements at the same time, and to provide a photovoltaic cable with good flame retardancy, good waterproofness and impact and rolling resistance.

[0006] The present invention provides a photovoltaic cable, including a conductor, an insulating layer and a sheath layer. The insulating layer is coated on the outside of the conductor, and the sheath layer is coated on the outside of the insulating layer; the material of the insulating layer includes the following components in parts by weight: 84-120 parts of base resin, 110-170 parts of flame retardant modifier, 1-5 parts of charring agent, 0.5-2 parts of antioxidant, 1-3 parts of lubricant, 0.5-2 parts of cross-linking agent, 1-4 parts of coloring agent; wherein, the base resin is composed of a first EVA resin, a second EVA resin, polyethylene and polyolefin elastomer; the VA content in the first EVA resin is 17%-19%, and the VA content in the second EVA resin is 24%-28%.

[0007] In one embodiment of the present invention, the VA content in the first EVA resin is 18%, and the VA content in the second EVA resin is 26%.

[0008] In one embodiment of the present invention, the weight ratio of the base resin to the flame retardant modifier is 1:(1.1 - 1.3).

[0009] In one embodiment of the present invention, in the base resin, the ratio of the sum of the weights of the first EVA resin and the second EVA resin to the sum of the weights of the polyethylene and the polyolefin elastomer is 1:1.

[0010] In one embodiment of the present invention, in the base resin, the weight ratio of the first EVA resin to the second EVA resin is 1:(0.6 - 0.75); the weight ratio of the polyethylene to the polyolefin elastomer is 1:(0.2 - 0.35).

[0011] In one embodiment of the present invention, in the base resin, the weight ratio of the first EVA resin to the second EVA resin is 30:20; the weight ratio of the polyethylene to the polyolefin elastomer is 40:10.

[0012] In one embodiment of the present invention, the conductor is formed by stranding multiple single wires; when the nominal cross-sectional area of the conductor is 4 mm 2 , the diameter of the single wire is set to 0.2 mm, the number of the single wires is set to 126, and the bunching pitch diameter ratio of the conductor is set to 13 - 15; when the nominal cross-sectional area of the conductor is 6 mm 2 , the diameter of the single wire is set to 0.2 mm, the number of the single wires is set to 175, and the bunching pitch diameter ratio of the conductor is set to 13 - 15; when the nominal cross-sectional area of the conductor is 10 mm 2 , the diameter of the single wire is set to 0.2 mm, the number of the single wires is set to 302, the bunching pitch diameter ratio of the conductor is set to 13 - 15, and the bunching pitch diameter ratio of the double-stranded wire is set to 12 - 14.

[0013] In one embodiment of the present invention, the flame retardant modifier is composed of aluminum hydroxide, magnesium hydroxide, and melamine cyanurate, and the mass ratio of the three is (70 - 90):(30 - 50):(10 - 30).

[0014] In one embodiment of the present invention, the charring agent is set as piperazine pyrophosphate; the antioxidant is set as antioxidant 1010; the lubricant is set as polyethylene wax; the crosslinking agent is set as trimethylolpropane trimethacrylate; the colorant is set as carbon black.

[0015] In one embodiment of the present invention, the preparation method of the material of the insulating layer comprises the following steps:

[0016] S1. Add the base resin, flame retardant modifier, charring agent, antioxidant, lubricant, crosslinking agent, and colorant of all components into a mixer for mixing, and raise the temperature of the mixer.

[0017] S2. When the temperature of the mixer rises to 108°C - 112°C, conduct the first material turning and continue mixing.

[0018] S3. When the temperature of the mixer rises to 148°C - 152°C, conduct the second material turning and continue mixing.

[0019] S4. After 10 minutes of mixing from the second material turning, take out the material from the mixer, and add the material into a twin-screw extruder for plasticization and then into a single-screw extruder for pelletizing to obtain the material for making the insulating layer.

[0020] The above technical solution of the present invention has the following advantages compared with the prior art:

[0021] For the photovoltaic cable of the present invention, the material of the insulating layer is adjusted. The EVA-18 resin in the original insulating layer base is changed to a combination of the first EVA resin and the second EVA resin, and the ratio of each flame retardant auxiliary is correspondingly adjusted. The dispersibility of the inorganic flame retardant material is increased, the proportion of the inorganic flame retardant component is reduced, the oxygen index of the insulating layer is lowered from 24 to 22. Cooperating with the sheath layer, while ensuring that the overall flame retardant performance of the photovoltaic cable meets the CPR flame retardant Dca level, the flexibility of the insulating layer is increased, and the water absorption is reduced at the same time. The photovoltaic cable meets the UL 854 impact and rolling test, as well as the AD8 waterproof test recognized by European customers, that is, the test requirements of Appendix D and Appendix E of EN 50525-2-21. The base resin composed of the first EVA resin, the second EVA resin, polyethylene, and polyolefin elastomer, cooperating with auxiliaries such as antioxidant, flame retardant, lubricant, crosslinking agent, and charring agent, combines the performance of each raw material to make up for each other's deficiencies, and has excellent properties such as aging resistance, low temperature resistance, acid and alkali resistance, low water absorption, impact resistance, and rolling resistance, etc. The flame retardant safety, electrical safety, and service life of the photovoltaic cable are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to make the content of the present invention easier to be clearly understood, the following further describes the present invention in detail according to the specific embodiments of the present invention in conjunction with the drawings, wherein

[0023] Figure 1 is a schematic cross-sectional structure diagram of the photovoltaic cable in the preferred embodiment of the present invention.

[0024] Description of the reference numerals in the drawings: 1. Conductor; 2. Insulating layer; 3. Sheath layer. Detailed implementation manners

[0025] The present invention will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the specific embodiments cited are not intended to limit the present invention.

[0026] Taking the H1Z2Z2-K photovoltaic cable as an example, it is commonly used in centralized photovoltaic power stations and only needs to meet the requirements such as single vertical combustion and low smoke and halogen-free in the EN 50618 standard. For this reason, halogen-free materials are usually selected as the insulating layer. Excessive inorganic flame retardant components in halogen-free materials result in the overall hardness and brittleness of the H1Z2Z2-K photovoltaic cable, making it prone to cracking problems and having weak impact and rolling resistance. At the same time, due to excessive inorganic flame retardant components in the insulating layer and the sheath layer, the water absorption of the H1Z2Z2-K photovoltaic cable is relatively large.

[0027] As for the photovoltaic cable applied to distributed photovoltaic power stations, it is often installed on the top or surrounding areas of buildings. Due to the change in the use environment, compared with the photovoltaic cable of centralized photovoltaic power stations, the photovoltaic cable applied to distributed photovoltaic power stations is more vulnerable to mechanical damage. For this reason, it is necessary to conduct a UL 854 impact and rolling test on the photovoltaic cable, and the conventional H1Z2Z2-K photovoltaic cable obviously cannot meet the test requirements. At the same time, since the photovoltaic cable of distributed photovoltaic power stations is installed outdoors, rainwater is likely to affect it. For this reason, it is necessary for the photovoltaic cable to pass the AD8 level waterproof test recognized by European customers. Specifically, it needs to meet the test requirements of Appendix D and Appendix E of EN 50525-2-21, while the conventional H1Z2Z2-K photovoltaic cable usually can only meet the AD7 waterproof level requirements. The reason for describing it as the AD8 level waterproof test recognized by European customers is that there is no generally recognized test method for the AD8 level waterproof test at present, so the test method and results recognized by European customers shall prevail.

[0028] Refer to Figure 1 As shown, the present invention discloses a photovoltaic cable, which includes a conductor 1, an insulating layer 2 and a sheath layer 3. The insulating layer 2 is coated on the outer side of the conductor 1, and the sheath layer 3 is coated on the outer side of the insulating layer 2.

[0029] The material of the insulating layer 2 includes the following components by weight: 84-120 parts of base resin, 110-170 parts of flame retardant modifier, 1-5 parts of charring agent, 0.5-2 parts of antioxidant, 1-3 parts of lubricant, 0.5-2 parts of crosslinking agent, and 1-4 parts of coloring agent;

[0030] Among them, the base resin is composed of a first EVA resin, a second EVA resin, polyethylene (abbreviated as PE), and a polyolefin elastomer (abbreviated as POE); the VA content in the first EVA resin is 17% - 19%, and the VA content in the second EVA resin is 24% - 28%. VA is the English abbreviation for vinyl acetate, and EVA is the English abbreviation for ethylene-vinyl acetate copolymer.

[0031] For the photovoltaic cable of the present invention, the material of the insulating layer 2 is adjusted. The EVA-18 resin (VA content is 18%) in the original insulating layer base material is changed to a combination of the first EVA resin and the second EVA resin, and at the same time, the ratio of each flame retardant additive is adjusted accordingly. The dispersion of the inorganic flame retardant material is increased, the proportion of the inorganic flame retardant component is reduced, the oxygen index of the insulating layer 2 is lowered from 24 to 22. Cooperating with the sheath layer 3, on the premise of ensuring that the overall flame retardant performance of the photovoltaic cable meets the CPR flame retardant Dca level, the flexibility of the insulating layer 2 is increased, and the water absorption is reduced at the same time. The photovoltaic cable meets the UL 854 impact and rolling test, as well as the AD8 waterproof test, that is, the test requirements of Appendix D and Appendix E of EN 50525-2-21. The base resin composed of the first EVA resin, the second EVA resin, polyethylene, and the polyolefin elastomer, in combination with additives such as antioxidants, flame retardants, lubricants, crosslinking agents, and char-forming agents, combines the performance of each raw material, makes up for each other's advantages and disadvantages, and has excellent aging resistance, low-temperature resistance, acid and alkali resistance, low water absorption, impact resistance, rolling resistance, etc. The flame retardant safety, electrical safety, and service life of the photovoltaic cable are high.

[0032] Preferably, the sheath layer 3 is made of a low-smoke, halogen-free, flame-retardant, irradiated cross-linked polyolefin material, and its performance meets the requirements of the EN 50618 standard.

[0033] The properties of EVA materials are closely related to their VA content. When other conditions are fixed, as the VA content increases, the elasticity, flexibility, and compatibility of EVA materials also increase. Conversely, as the VA content decreases, the rigidity, wear resistance, and electrical insulation of EVA materials improve. The first EVA resin with a VA content of 17% - 19% and the second EVA resin with a VA content of 24% - 28% can ensure that each material is evenly mixed, enabling the various properties of the photovoltaic cable to meet the requirements. When the VA content in the first EVA resin is less than 17%, more of the second EVA resin is required, or the VA content of the second EVA resin needs to be increased, resulting in an increase in production costs. When the VA content in the first EVA resin is greater than 19%, it is difficult to achieve a performance balance by adding the second EVA resin. Similarly, when the VA content in the second EVA resin is less than 24%, it is difficult to achieve a performance balance with the first EVA resin. When the VA content in the second EVA resin is greater than 28% and less than 40%, the second EVA resin will be in an intermediate state similar to rubber. Although the ability to mix materials increases, the cost also increases, and the cost performance is low. When the VA content in the second EVA resin is greater than 40%, it has actually become an EVA elastomer, with properties similar to rubber, and is not suitable as a material for the insulation layer of photovoltaic cables.

[0034] Furthermore, in some embodiments of the photovoltaic cable of the present invention, the VA content in the first EVA resin is 18%, and the VA content in the second EVA resin is 26%. After the first EVA resin and the second EVA resin with such VA contents are kneaded, it can ensure that the properties of the materials reach the best, ensure that each material is fully mixed, and can also control costs.

[0035] In some embodiments of the photovoltaic cable of the present invention, the weight ratio of the base resin to the flame retardant modifier is 1:(1.1 - 1.3). That is, when the weight of the base resin is 100 parts, the weight of the flame retardant modifier is 110 parts - 130 parts. By further restricting the weight ratio of the base resin and the flame retardant modifier, it can ensure better flame retardancy, water resistance, impact resistance, and rolling resistance of the insulation layer 2. When the ratio is greater than 1:1.1, the amount of the flame retardant modifier is too small to ensure flame retardancy. When the ratio is less than 1:1.3, the water absorption of the insulation layer 2 is too large, and the elongation at break decreases, making it difficult to meet the AD8 waterproof grade requirements.

[0036] For the photovoltaic cable of the present invention, in some embodiments, in the base resin, the ratio of the sum of the weights of the first EVA resin and the second EVA resin to the sum of the weights of the polyethylene and the polyolefin elastomer is 1:1. A ratio of 1:1 can ensure that the performance of the insulating layer material is balanced and meets the requirements. When the ratio is less than 1, the amount of EVA resin is small. Although the waterproof property and impact resistance are good, due to excessive strength and insufficient flexibility, it is difficult to pass the anti-rolling test. On the contrary, when the ratio is greater than 1, the amount of EVA resin is excessive, the overall flexibility is high and it is anti-rolled, but the waterproof property and strength are insufficient.

[0037] Furthermore, in some embodiments, in the base resin, the weight ratio of the first EVA resin to the second EVA resin in the base resin is 1:(0.6 - 0.75); the weight ratio of the polyethylene to the polyolefin elastomer is 1:(0.2 - 0.35). When the ratio of the sum of the weights of the first EVA resin and the second EVA resin to the sum of the weights of the polyethylene and the polyolefin elastomer is 1:1, the weights of the four materials in the base resin are further restricted to ensure that the flame retardancy, waterproof property, and anti-impact rolling property of the photovoltaic cable can meet the requirements. Specifically, when the weight ratio of the first EVA resin to the second EVA resin is greater than 1:0.6, the amount of the second EVA resin is relatively small, and it is difficult to meet the requirements for softness and compatibility between different materials; when the weight ratio of the first EVA resin to the second EVA resin is less than 1:0.75, the amount of the second EVA resin is relatively large, and it is difficult to meet the requirements for wear resistance and overall cost performance. Similarly, when the weight ratio of the polyethylene to the polyolefin elastomer is greater than 1:0.2, the amount of the polyolefin elastomer is relatively small, and it is difficult to meet the requirement for toughness; when the weight ratio of the polyethylene to the polyolefin elastomer is less than 1:0.35, it is difficult to meet the requirement for rigidity.

[0038] Furthermore, in some embodiments, in the base resin, the weight ratio of the first EVA resin, the second EVA resin, the polyethylene, and the polyolefin elastomer is 30:20:40:10. This is the best ratio of the base resin. The insulating layer material prepared from the base resin with the above ratio can make the photovoltaic cable have the best performance while meeting the performance requirements.

[0039] Furthermore, in order to improve the overall flexibility of the photovoltaic cable, the conductor 1 is adjusted. The conductor is formed by stranding multiple single wires. By using single wires with a smaller diameter, increasing the number of single wires, and reducing the pitch diameter ratio, the flexibility of the conductor 1 is increased. The structure of the conductor 1 becomes more compact, and it is more difficult for the insulating layer 2 to embed into the conductor 1. Therefore, when subjected to external impact and rolling, the problem of insulation layer damage caused by the embedding of the insulating layer 2 into the conductor 1 is reduced. The following takes the most commonly used nominal cross-sectional areas of 4, 6, and 10 mm for photovoltaic cables 2Take the conductor as an example.

[0040] When the nominal cross-sectional area is 4 mm 2 :

[0041] For a conventional photovoltaic cable, the number of conductors is 56, the diameter of each single wire is 0.29 mm, the arrangement is that 56 conductors are arranged directly, and the bunching pitch ratio is 16 - 18;

[0042] For the photovoltaic cable of the present invention, the number of conductors is 126, the diameter of each single wire is 0.2 mm, the arrangement is composed of a first conductor consisting of 18 single wires and 6 second conductors evenly distributed and arranged around the first conductor, each second conductor consists of 18 single wires, and the bunching pitch ratio is 13 - 15.

[0043] When the nominal cross-sectional area is 6 mm 2 :

[0044] For a conventional photovoltaic cable, the number of conductors is 84, the diameter of each single wire is 0.29 mm, the arrangement is that 84 conductors are arranged directly, and the bunching pitch ratio is 16 - 18;

[0045] For the photovoltaic cable of the present invention, the number of conductors is 175, the diameter of each single wire is 0.2 mm, the arrangement is composed of a first conductor consisting of 25 single wires and 6 second conductors evenly distributed and arranged around the first conductor, each second conductor consists of 25 single wires, and the bunching pitch ratio is 13 - 15.

[0046] When the nominal cross-sectional area is 10 mm 2 :

[0047] For a conventional photovoltaic cable, the number of conductors is 74, the diameter of each single wire is 0.401 mm, the arrangement is composed of a central conductor consisting of 11 single wires and six surrounding conductors arranged around the central conductor. The surrounding conductors each include three first surrounding conductors and three second surrounding conductors. The first surrounding conductor includes 11 single wires and the second surrounding conductor includes 10 single wires. The bunching pitch ratio is 16 - 18 and the stranding pitch ratio is 14 - 16.

[0048] For the photovoltaic cable of the present invention, the number of conductors is 302, the diameter of each single wire is 0.2 mm, the arrangement is composed of a first conductor consisting of 44 single wires and 6 second conductors evenly distributed and arranged around the first conductor, each second conductor consists of 43 single wires, the bunching pitch ratio is 13 - 15 and the stranding pitch ratio is 12 - 14.

[0049] Preferably, conductor 1 adopts the type 5 round stranded tinned copper conductor specified by the IEC 60228 standard to ensure that the surface of the conductor is smooth, without burrs, sharp edges, protrusions or broken single wires that damage the insulation.

[0050] In some embodiments, the flame retardant modifier is composed of aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2) and melamine cyanurate (MCA), and the mass ratio of the three is (70 - 90):(30 - 50):(10 - 30). By adjusting the ratio of the flame retardant additives, the flexibility and waterproofness of the photovoltaic cable are improved on the premise of meeting the flame retardancy requirements. Preferably, the best ratio of the three is 80:35:15. Through the flame retardant modifier with this ratio, the photovoltaic cable with the best performance can be achieved in cooperation with the base resin and other additives.

[0051] In some embodiments, the charring agent is set as piperazine pyrophosphate; the antioxidant is set as antioxidant 1010; the lubricant is set as polyethylene wax; the crosslinking agent is set as trimethylolpropane trimethacrylate (TMPTMA for short); the colorant is set as carbon black. The above materials can ensure that the flame retardancy, impact and rolling resistance, and waterproofness of the photovoltaic cable meet the performance requirements, and the effect is better. Preferably, the amount of antioxidant 1010 is 1.4 parts, the amount of polyethylene wax is 2 parts, the amount of trimethylolpropane trimethacrylate is 1.5 parts, the amount of piperazine pyrophosphate is 3 parts, and the amount of carbon black is 2.5 parts.

[0052] Furthermore, in order to ensure the flame retardancy, waterproofness, and anti-rolling and impact resistance of the material of the insulating layer 2 of the photovoltaic cable described in the present invention, the control of the temperature during its preparation is also very crucial. Turning the materials during mixing at a suitable temperature can make the composition of the materials more uniform, thereby ensuring good flame retardancy, waterproofness, and anti-rolling and impact resistance of the insulating layer 2.

[0053] Specifically, the preparation method of the material of the insulating layer 2 includes the following steps:

[0054] S1. Add all components of the first EVA resin, second EVA resin, polyethylene, polyolefin elastomer, aluminum hydroxide, magnesium hydroxide, melamine cyanurate, antioxidant 1010, polyethylene wax, trimethylolpropane trimethacrylate, piperazine pyrophosphate, and carbon black into a kneader for mixing, and raise the temperature of the kneader.

[0055] S2. When the temperature of the kneader rises to 108°C - 112°C, conduct the first turning and continue mixing.

[0056] S3. When the temperature of the kneader rises to 148°C - 152°C, conduct the second turning and continue mixing.

[0057] S4. After 15 minutes of the second material turnover and kneading, the material is taken out from the internal mixer, and the material is successively added to a twin-screw extruder for plasticization and then added to a single-screw extruder for pelletizing to obtain the material for making the insulating layer.

[0058] By conducting the first material turnover on the material in the internal mixer at 108°C to 112°C, it can ensure that all materials are fully fused, so as to ensure that the obtained insulating layer material is uniform and has good performance. When the temperature is lower than 108°C, some materials may not be fully melted during the turnover, making it difficult to mix. When the temperature is higher than 112°C, the material in the internal mixer has already transformed from a solid state to a rubber state, and at this time, the turnover timing is too late to ensure full mixing of the materials. Conduct the second material turnover on the material in the internal mixer at 148°C to 152°C. This temperature range is the critical point for the material to complete the transformation from a solid state to a rubber state. Conducting the second material turnover in this temperature range ensures that the material in the internal mixer is further mixed evenly and the performance is stable. When the temperature is higher than 152°C, the material has almost completely become rubbery, with high viscosity and it is difficult to conduct further turnover and mixing. When the temperature is lower than 148°C, it is difficult to ensure full mixing of the materials. Preferably, the material turnover is carried out at 110°C and 150°C respectively to ensure the best mixing effect of the materials.

[0059] Examples 1, 2, and 3, and Comparative Examples 1 and 2

[0060] The formulations of the insulating layers of Examples 1, 2, and 3, and Comparative Examples 1 and 2 are shown in Table 1.

[0061] Table 1 Formulations of the materials for the insulating layers in Examples and Comparative Examples

[0062]

[0063] Among them, the VA content of the first EVA resin is 18%, and the VA content of the second EVA resin is 26%. According to the same preparation method as in Example 1, each component in the formulation is prepared into the material for the insulating layer.

[0064] Performance testing

[0065] With reference to the UL 854 impact and rolling test, the tests in Appendices D and E of EN 50525-2-21, and the CPR flame retardant Dca-s1a, d1, a1 grade, the performance of the materials of the insulating layers in Examples and Comparative Examples is tested, and the test results are shown in Table 2.

[0066] Table 2 Performance test results of the materials of the insulating layers in Examples and Comparative Examples

[0067]

[0068] Among them, T1 is the UL 854 impact test result. The test content is the number of lit bulbs at 10 test points, and the standard requires the number ≤ 2. Therefore, Comparative Example 1 and Comparative Example 2 both fail.

[0069] T2 is the UL 854 rolling test result. The test content is the average pressure when the LED bulb is lit, and the standard requires the average pressure ≥ 4.448 kN. Therefore, Comparative Example 1 fails.

[0070] T3 is the withstand voltage test result of immersion in water at 50°C for 100 days in Appendix D of EN 50525-2-21. The standard requires no breakdown. Therefore, Comparative Example 1 and Comparative Example 2 both fail.

[0071] T4 is the volume resistivity of immersion in water at 50°C for 1 day in Appendix D of EN 50525-2-21. The standard requires the volume resistivity ≥ 10 12 Ω·cm;

[0072] T5 is the volume resistivity of immersion in water at 50°C for 14 days in Appendix D of EN 50525-2-21. The standard requires the volume resistivity ≥ 10 11 Ω·cm; Therefore, Comparative Example 1 and Comparative Example 2 both fail.

[0073] T6 is the weight change test result of immersion in water at 50°C for 100 days in Appendix E of EN 50525-2-21. The standard requires the increase ratio ≤ 40%. Therefore, Comparative Example 1 fails.

[0074] T7 is the change rate of tensile strength and elongation at break of immersion in water at 50°C for 100 days and 28 days in Appendix E of EN 50525-2-21. The standard requires the change rate of tensile strength ≤ ±15% and the change rate of elongation at break ≤ ±20%. Therefore, Comparative Example 1 fails.

[0075] T8 is the test result of the CPR Dca test - smoke production & smoke density, specifically the total smoke production, Peak SPR (maximum smoke production per unit time), and light transmittance during 1200 s of combustion. The standard requires the total smoke production ≤ 50 m 2 and the maximum amount ≤ 0.25 m 2 / s, and the light transmittance ≥ 80%;

[0076] T9 is the test result of the CPR Dca test - dripping test, specifically the time for the burning drips / particles to continue burning after falling to the bottom plate of the combustion chamber within 1200 s. The standard requires the maximum number of seconds not to exceed 10 s;

[0077] T10 is the test result of the CPR Dca test - halogen release test, specifically the conductivity and pH value. The standard requires the conductivity to be less than 2.5 μS / mm and the pH value to be greater than 4.3.

[0078] As can be seen from the results in the above table, compared with the comparative example, for the photovoltaic cable of the present invention, the results of the insulating layer material in multiple tests are better than those of the comparative example. In particular, when the material prepared with the formulation of Example 1 is used as the insulating layer of the photovoltaic cable, the photovoltaic cable can have the best performance while meeting the performance requirements.

[0079] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A photovoltaic cable, characterized in that, It includes a conductor, an insulating layer, and a sheath layer. The insulating layer is coated on the outer side of the conductor, and the sheath layer is coated on the outer side of the insulating layer. The material of the insulating layer includes the following components by weight: 84 - 120 parts of base resin, 110 - 170 parts of flame retardant modifier, 1 - 5 parts of charring agent, 0.5 - 2 parts of antioxidant, 1 - 3 parts of lubricant, 0.5 - 2 parts of crosslinking agent, and 1 - 4 parts of colorant. Among them, the base resin is composed of a first EVA resin, a second EVA resin, polyethylene, and a polyolefin elastomer. The VA content in the first EVA resin is 17% - 19%, and the VA content in the second EVA resin is 24% - 28%. In the base resin, the ratio of the sum of the weights of the first EVA resin and the second EVA resin, and the sum of the weights of the polyethylene and the polyolefin elastomer is 1:

1. The weight ratio of the first EVA resin to the second EVA resin is 1:(0.6 - 0.75); the weight ratio of the polyethylene to the polyolefin elastomer is 1:(0.2 - 0.35). The flame retardant modifier is composed of aluminum hydroxide, magnesium hydroxide, and melamine cyanurate, and the mass ratio of the three is (70 - 90):(30 - 50):(10 - 30).

2. The photovoltaic cable according to claim 1, wherein: The VA content in the first EVA resin is 18%, and the VA content in the second EVA resin is 26%.

3. The photovoltaic cable according to claim 1, wherein: The weight ratio of the base resin to the flame retardant modifier is 1:(1.1 - 1.3).

4. The photovoltaic cable according to claim 1, characterized in that: In the base resin, the weight ratio of the first EVA resin to the second EVA resin is 30:20; the weight ratio of the polyethylene to the polyolefin elastomer is 40:

10.

5. The photovoltaic cable according to claim 1, wherein: The conductor is formed by stranding multiple single wires. Among them, the nominal cross-sectional area of the conductor is 4 mm 2 , the diameter of the single wire is set to 0.2 mm, the number of the single wires is set to 126, and the pitch diameter ratio of the bunch-stranded conductor is set to 13-15; Alternatively, the nominal cross-sectional area of the conductor is 6 mm 2 , the diameter of the single wire is set to 0.2 mm, the number of the single wires is set to 175, and the pitch diameter ratio of the stranded conductor is set to 13-15; Alternatively, the nominal cross-sectional area of the conductor is 10 mm 2 , the diameter of the single wire is set to 0.2 mm, the number of the single wires is set to 302, the bunching pitch ratio of the conductor is set to 13 - 15, and the multiple-strand twisting pitch ratio is set to 12 - 14.

6. The photovoltaic cable according to claim 1, wherein: The charring agent is set as piperazine pyrophosphate; the antioxidant is set as antioxidant 1010; the lubricant is set as polyethylene wax; the crosslinking agent is set as trimethylolpropane trimethacrylate; the colorant is set as carbon black.

7. The photovoltaic cable according to any one of claims 1-6, characterized in that, The preparation method of the material of the insulating layer includes the following steps: S1. Add all components of the base resin, flame retardant modifier, charring agent, antioxidant, lubricant, crosslinking agent, and colorant into a mixer and mix, and raise the temperature of the mixer. S2. When the temperature of the mixer rises to 108°C - 112°C, conduct the first material turning and continue mixing. S3. When the temperature of the mixer rises to 148°C - 152°C, conduct the second material turning and continue mixing. S4. After 10 minutes of mixing from the second material turning, take out the material from the mixer, and sequentially add the material into a twin-screw extruder for plasticization and into a single-screw extruder for pelletizing to obtain the material for making the insulating layer.

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