A wet-wound water-resistant cable and a production process thereof

Abstract

The application discloses a wet-winding water-resistant cable and a production process thereof, and the cable comprises a cable conductor, a semi-conductive layer, an insulating layer and a waterproof sheath material arranged in sequence; components of the insulating layer comprise ethylene-vinyl acetate copolymer, tri (methacrylic acid) trimethylolpropane ester, pyrazole 1, 3, 5-triazine and / or 6, 8-diamino-7-nitro-tetrazol [1, 5-b] pyridazine, an absorption type light stabilizer, a polymer of succinic acid and 4-hydroxy-2, 2, 6, 6-tetramethyl-1-piperidinol and the like; components of the semi-conductive layer comprise ethylene-butyl acrylate copolymer, metal organic framework modified conductive carbon black, graphene oxide powder, trimethylolpropane and the like. The insulating layer material adopted by the application has excellent radiation resistance, insulation, heat resistance, mechanical properties and water tree resistance, and only 2.0 mm can reach the standard strength, and the semi-conductive layer and the waterproof sheath material with excellent water resistance are assembled to have a good shielding effect, so that the cable of the application can meet the working environment requirements in the wet-winding motor nuclear main pump.

Description

Technical Field

[0001] This invention relates to special cables, specifically to a wet-winding water-resistant cable and its manufacturing process. Background Technology

[0002] The reactor coolant pump (nuclear main pump) is the "heart" of a nuclear power plant and the only active component in the reactor loop, holding an irreplaceable position in a nuclear power unit. The wet-wound motor nuclear main pump is a high-power, high-efficiency main pump developed based on the shaft-sealed main pump of pressurized water reactor and the shaftless main pump of boiling water reactor, and it performs exceptionally well in improving energy utilization efficiency.

[0003] However, the working environment and operating conditions of wet-wound motor nuclear main pumps are harsher than those of other nuclear main pumps. They often face various adverse factors such as radiation, high temperature, high pressure, and especially water corrosion. The cables used in wet-wound motor nuclear main pumps must also be able to withstand these adverse factors. Due to moisture, electrical stress, and other inducing factors such as impurities, protrusions, space charges, or ions in the cable insulation layer, microchannels resembling tree branches can form in the insulation layer, a phenomenon known as water treeing, which significantly affects the cable's lifespan. Cables used in wet-wound motor nuclear main pumps must be resistant to water treeing to extend their service life. On the other hand, according to GB / T 12706.2, 16mm² cables for nuclear power... 2 The insulation layer thickness of the cable should be no less than 3.4mm to meet the insulation requirements. In addition, the cable also needs to add a shielding layer to eliminate the problem of partial discharge between the cable core and the insulation layer. This further increases the diameter of the cable, which is unfavorable for cable laying and the narrow working environment of wet-wound motors and main pumps. Summary of the Invention

[0004] To address the problem that ordinary cables are difficult to use in nuclear main pumps with wet-winding motors, this invention provides a wet-winding water-resistant cable and its manufacturing process. This wet-winding water-resistant cable can prevent water tree growth and also has excellent resistance to high temperature, electrical aging, radiation, and water pressure. Furthermore, it has a smaller diameter and is suitable for use in nuclear main pumps with wet-winding motors.

[0005] To achieve the above objectives, the present invention provides a wet-winding water-resistant cable, which comprises the following components: a cable conductor, a semi-conductive layer, an insulation layer, and a waterproof sheath layer;

[0006] The insulating layer, by weight, is made from raw materials comprising the following components: 5-8 parts of ethylene-vinyl acetate copolymer, 75-85 parts of metallocene linear low-density polyethylene, 0-5 parts of high-density polyethylene, 3-7 parts of maleic anhydride-grafted metallocene polyethylene-vinyl acetate copolymer, 1-3 parts of high-temperature antioxidant, 1-4 parts of tris(methacrylate)trimethylolpropane ester, 0.1-0.3 parts of polycyclic aromatic hydrocarbon nucleating agent, 0.5-1.2 parts of absorption-type light stabilizer, and 0.3-0.8 parts of a polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol; wherein the polycyclic aromatic hydrocarbon nucleating agent is pyrazolo-1,3,5-triazine and / or 6,8-diamino-7-nitro-tetrazo[1,5-b]pyridazine;

[0007] The semiconductive layer, by weight, is made from raw materials comprising the following components: 90-93 parts of ethylene-butyl acrylate copolymer, 2-3 parts of linear low-density polyethylene, 2-4 parts of ethylene-vinyl acetate copolymer, 10-13 parts of metal-organic framework modified conductive carbon black, 5-7 parts of graphene oxide powder, and 2-3 parts of trimethylolpropane.

[0008] The insulation layer of this cable incorporates polycyclic aromatic hydrocarbon nucleating agents to produce finer polyethylene crystal particles, which better inhibits water tree growth. The synergistic effect of other components also results in excellent heat resistance, radiation resistance, high-temperature resistance, and mechanical properties of the insulation layer. The semi-conductive layer uses metal-organic framework-modified conductive carbon black, leading to a more uniform electric field distribution and better electromagnetic shielding within the cable. The waterproof sheath further enhances the cable's water resistance and water tree resistance. The integrated assembly of all components allows the cable to meet the operating environment requirements of wet-wound motors and nuclear main pumps.

[0009] Preferably, the high-temperature resistant antioxidant is selected from one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dilauryl thiodipropionate, tris[2,4-di-tert-butylphenyl]phosphite, N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester.

[0010] Preferably, the absorbent light stabilizer is selected from one or more of phenyl benzoate, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-(2-hydroxy-5-methylphenyl)benzotriazole and 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole.

[0011] The beneficial effects of this preferred method are as follows: phenyl benzoate, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-(2-hydroxy-5-methylphenyl)benzotriazole and 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole work differently from the polymers of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol. By compounding them, the absorption of radiation can be enhanced, and the radiation resistance of the insulating layer can be improved.

[0012] Preferably, the waterproof sheath layer is made of nylon 12.

[0013] The beneficial effect of this preferred method is that nylon 12 is hydrophobic, which can increase the water resistance and water tree resistance of the cable.

[0014] Preferably, a composite water-blocking adhesive is further filled between the insulating layer and the waterproof sheath layer.

[0015] The beneficial effect of this preferred method is that the composite water-blocking adhesive can further increase the water resistance of the cable.

[0016] The present invention also provides a manufacturing process for the above-mentioned wet-wound water-resistant cable, the manufacturing process comprising the following steps:

[0017] (1) The semiconductive layer and the insulating layer are extruded sequentially onto the surface of the cable conductor, wherein the thickness of the insulating layer is ≤2.0mm, to obtain an insulated wire core;

[0018] (2) The waterproof sheath layer is extruded over the insulated core to obtain the wet winding water-resistant cable.

[0019] Preferably, the thickness of the semiconductive layer is ≤0.2mm.

[0020] Preferably, the thickness of the waterproof sheath layer is ≤0.3mm.

[0021] Preferably, the cable conductor is made by drawing copper rods into wires through a nitriding polishing die and then annealing them at high temperature and low pressure.

[0022] Preferably, the nitriding polishing includes the following steps:

[0023] (1) Heat the clean mold to 1000~1100℃ for 20~24h;

[0024] (2) The mold is nitrided with a nitrogen-hydrogen mixture containing 10-20% hydrogen gas for 8-9 hours at a pressure of 0.5-1.5 bar.

[0025] (3) After the mold has cooled to room temperature, clean the surface impurities to complete the nitriding polishing.

[0026] The advantages of this preferred method are: the mold structure of the nitriding polishing is more refined, the drawn copper wire conductor is smoother, and there are no defects such as burrs.

[0027] Preferably, the process parameters for the high-temperature low-pressure annealing are: vacuum pressure ≤ -0.1MPa, gas charging pressure 0.35~0.45MPa, heating temperature 420~440℃, holding time 4~6h, and cooling time 18~26h.

[0028] The beneficial effects of this preferred method are: high-temperature and low-pressure annealing can optimize the hardness of copper wire and further improve the flexibility of cable conductor.

[0029] Preferably, the extrusion temperature of the semiconductive layer is set sequentially to 135±5℃, 150±5℃, 160±5℃, 170±5℃, 175±5℃, 180±5℃, and 185±5℃.

[0030] The advantages of this preferred method are: the temperature setting allows the semiconductive layer material to be fully plasticized, resulting in a smooth and round surface, thus improving the electrical performance of the cable.

[0031] Preferably, the extrusion temperature of the insulating layer is set sequentially to 160±5℃, 170±5℃, 175±5℃, 185±5℃, 190±5℃, 195±5℃, and 205±5℃.

[0032] The advantages of this preferred method are: the temperature setting allows the insulating layer material to be fully plasticized, and the temperature is higher than the extrusion temperature of the semiconductive layer, resulting in a tighter bond with the semiconductive layer.

[0033] Preferably, the extrusion temperature of the waterproof sheath layer is set sequentially to 265±5℃, 265±5℃, 275±5℃, 275±5℃, 275±5℃, 265±5℃, and 270±5℃.

[0034] The advantage of this preferred method is that the temperature of 260~280℃ allows nylon 12 to be extruded without problems such as bubbling.

[0035] Through the above technical solution, the present invention achieves the following beneficial effects:

[0036] 1. The insulation material used in this invention has excellent radiation resistance, insulation, heat resistance, mechanical properties and water tree resistance. Only 2.0mm is needed to achieve the standard strength. When combined with a semi-conductive layer with good shielding effect and a waterproof sheath material with excellent water resistance, the cable of this invention can meet the working environment requirements of wet winding motors and nuclear main pumps.

[0037] 2. Under the premise of meeting the performance requirements of the cable, the present invention minimizes the thickness of the semiconductive layer, insulation layer and waterproof sheath layer, so that the overall diameter of the cable is smaller and the cable is lightweight. Detailed Implementation

[0038] The specific embodiments of the present invention will be described in detail below with reference to examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0039] In the following embodiments and comparative examples, the screw used for extruding the insulating layer is an improved type 65 screw with a thread diameter of 65±0.1mm. It includes a feeding section, a compression section, and a homogenization section. The screw diameter of the feeding section is 51±0.3mm, and the pitch is 60mm±0.1mm. The screw diameter of the compression section is 59±0.2mm, with a double thread structure, a thread pitch of 65mm±0.1mm, and a thread pitch between threads of 60mm±0.1mm. The screw diameter of the homogenization section is 59±0.2mm, and the pitch is 60mm±0.1mm.

[0040] Example 1:

[0041] The manufacturing process of wet-wound water-resistant cables is as follows:

[0042] (1) Prepare cable conductors.

[0043] The mold was cleaned with sulfuric acid; it was then placed in a heating furnace and heated at 1000℃ for 20 hours; a nitrogen-hydrogen mixture with a hydrogen gas fraction of 10% was introduced into the furnace to nitrid the mold for 8 hours at a pressure of 0.5 bar, resulting in a surface hardness of 900~1000 HV; after nitriding, the mold was removed and surface impurities were cleaned after the furnace temperature cooled to room temperature; the copper rod was drawn into copper wire through the mold; the copper wire was then subjected to high-temperature low-pressure annealing, with the vacuum pressure controlled at ≤-0.1MPa, the gas pressure at 0.35MPa, the heating temperature at 420℃, the holding time at 4 hours, and the cooling time at 18 hours, to obtain the cable conductor.

[0044] (2) Prepare the insulated wire core.

[0045] The semiconductive layer material is made from the following raw materials: 90g of ethylene-butyl acrylate copolymer, 2g of linear low-density polyethylene, 2g of ethylene-vinyl acetate copolymer, 10g of metal-organic framework modified conductive carbon black, 5g of graphene oxide powder, and 2g of trimethylolpropane.

[0046] The insulating layer material is made from the following raw materials: 5g of ethylene-vinyl acetate copolymer, 75g of metallocene linear low-density polyethylene, 5g of high-density polyethylene, 3g of maleic anhydride-grafted metallocene polyethylene-vinyl acetate copolymer, 1g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1g of tris(methacrylate)trimethylolpropane ester, 0.1g of pyrazolo-1,3,5-triazine, 0.5g of phenyl phthalate, and 0.3g of a polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol.

[0047] Semiconductor and insulation layers are extruded sequentially around the cable conductor using semiconductor and insulation materials, with an interval of no more than 10 seconds. The extrusion temperatures of the semiconductor layers are set sequentially to 130℃, 145℃, 155℃, 165℃, 170℃, 175℃, and 180℃, with a screw speed of 90 r / min, ensuring that the thickness of the semiconductor layer is ≤0.2 mm. The extrusion temperatures of the insulation layers are set sequentially to 155℃, 165℃, 170℃, 180℃, 185℃, 190℃, and 200℃, with a screw speed of 120 r / min, ensuring that the thickness of the insulation layer is ≤2.0 mm, thus obtaining an insulated wire core.

[0048] (3) Prepare a wet-winding water-resistant cable.

[0049] A layer of Nylon 12 waterproof sheath is extruded over the insulated core. The extrusion temperatures are set sequentially to 260℃, 260℃, 270℃, 270℃, 270℃, 260℃, and 265℃, ensuring that the thickness of the waterproof sheath is ≤0.3mm. DZ-107 composite water-blocking adhesive is used to fill the gap between the waterproof sheath and the insulation layer, resulting in a wet-winding water-resistant cable.

[0050] Example 2:

[0051] A type of wet-wound water-resistant cable, manufactured using the following process:

[0052] (1) Prepare cable conductors.

[0053] The mold was cleaned with sulfuric acid; it was then placed in a heating furnace and heated to 1050℃ for 22 hours; a nitrogen-hydrogen mixture with a hydrogen gas fraction of 15% was introduced into the furnace to nitrid the mold for 8.5 hours at a pressure of 1 bar, resulting in a surface hardness of 900~1000 HV; after nitriding, the mold was removed and surface impurities were cleaned after the furnace temperature cooled to room temperature; the copper rod was drawn into copper wire through the mold; the copper wire was then subjected to high-temperature low-pressure annealing, with the vacuum pressure controlled at ≤-0.1MPa, the gas pressure at 0.4MPa, the heating temperature at 430℃, the holding time at 5 hours, and the cooling time at 22 hours, to obtain the cable conductor.

[0054] (2) Prepare the insulated wire core.

[0055] The semiconductive layer material is made from the following raw materials: 91.5g of ethylene-butyl acrylate copolymer, 2.5g of linear low-density polyethylene, 3g of ethylene-vinyl acetate copolymer, 11.5g of metal-organic framework modified conductive carbon black, 6g of graphene oxide powder, and 2.5g of trimethylolpropane.

[0056] The insulating layer material is made from the following raw materials: 6.5g of ethylene-vinyl acetate copolymer, 80g of metallocene linear low-density polyethylene, 2.5g of high-density polyethylene, 5g of maleic anhydride-grafted metallocene polyethylene-vinyl acetate copolymer, 1g of dilaurate thiodipropionate, 1g of tris[2,4-di-tert-butylphenyl]phosphite, 2.5g of tris(methacrylate)trimethylolpropane, 0.1g of pyrazolo-1,3,5-triazine, 0.1g of 6,8-diamino-7-nitro-tetrazo[1,5-b]pyridazine, 0.4g of 2-hydroxy-4-n-octyloxybenzophenone, 0.45g of 2-hydroxy-4-methoxybenzophenone, and 0.55g of a polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol.

[0057] Semiconductor and insulation layers are extruded sequentially onto the outside of the cable conductor using semiconductor and insulation materials, with an interval of no more than 10 seconds. The extrusion temperatures of the semiconductor layers are set sequentially to 135℃, 150℃, 160℃, 170℃, 175℃, 180℃, and 185℃, with a screw speed of 90 r / min, ensuring that the thickness of the semiconductor layer is ≤0.2mm. The extrusion temperatures of the insulation layers are set sequentially to 160℃, 170℃, 175℃, 185℃, 190℃, 195℃, and 205℃, with a screw speed of 120 r / min, ensuring that the thickness of the insulation layer is ≤2.0mm, thus obtaining an insulated wire core.

[0058] (3) Prepare a wet-winding water-resistant cable.

[0059] A layer of Nylon 12 waterproof sheath is extruded over the insulated core. The extrusion temperatures are set sequentially to 265℃, 265℃, 275℃, 275℃, 275℃, 265℃, and 270℃, ensuring the thickness of the waterproof sheath layer is ≤0.3mm. DZ-107 composite water-blocking adhesive is used to fill the gap between the waterproof sheath layer and the insulation layer, resulting in a wet-winding water-resistant cable.

[0060] Example 3:

[0061] A type of wet-wound water-resistant cable, manufactured using the following process:

[0062] (1) Prepare cable conductors.

[0063] The mold was cleaned with sulfuric acid; it was then placed in a heating furnace and heated at 1100℃ for 24 hours; a nitrogen-hydrogen mixture with a hydrogen gas fraction of 20% was introduced into the furnace to nitrid the mold for 9 hours at a pressure of 1.5 bar, resulting in a surface hardness of 900~1000 HV; after nitriding, the mold was removed after the furnace temperature cooled to room temperature, and surface impurities were cleaned; the copper rod was drawn into copper wire through the mold; the copper wire was then subjected to high-temperature low-pressure annealing, with the vacuum pressure controlled at ≤-0.1MPa, the gas pressure at 0.45MPa, the heating temperature at 440℃, the holding time at 6 hours, and the cooling time at 26 hours, to obtain the cable conductor.

[0064] (2) Prepare the insulated wire core.

[0065] The semiconductive layer material is made from the following raw materials: 93g of ethylene-butyl acrylate copolymer, 3g of linear low-density polyethylene, 4g of ethylene-vinyl acetate copolymer, 13g of metal-organic framework modified conductive carbon black, 7g of graphene oxide powder, and 3g of trimethylolpropane.

[0066] The insulating layer material is made from the following raw materials: 8g of ethylene-vinyl acetate copolymer, 85g of metallocene linear low-density polyethylene, 7g of maleic anhydride-grafted metallocene polyethylene-vinyl acetate copolymer, 1g of tris[2,4-di-tert-butylphenyl]phosphite, 1g of N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, 1g of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol, 4g of tris(methacrylate)trimethylolpropane, 0.3g of 6,8-diamino-7-nitro-tetrazo[1,5-b]pyridazine, 0.6g of 2-(2-hydroxy-5-methylphenyl)benzotriazole, 0.6g of 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, and 0.8g of a polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol.

[0067] Semiconductor and insulation materials are extruded sequentially onto the outside of the cable conductor, with an interval of no more than 10 seconds. The extrusion temperatures of the semiconductor are set sequentially to 140℃, 155℃, 165℃, 175℃, 175±5℃, 185℃, and 190℃, with a screw speed of 90 r / min, so that the thickness of the semiconductor is ≤0.2mm. The extrusion temperatures of the insulation are set sequentially to 165℃, 175℃, 180℃, 190℃, 195℃, 200℃, and 210℃, with a screw speed of 120 r / min, so that the thickness of the insulation is ≤2.0mm, resulting in an insulated wire core.

[0068] (3) Prepare a wet-winding water-resistant cable.

[0069] A layer of Nylon 12 waterproof sheath is extruded over the insulated core. The extrusion temperatures are set sequentially to 270℃, 270℃, 280℃, 280℃, 280℃, 270℃, and 275℃, ensuring that the thickness of the waterproof sheath is ≤0.3mm. DZ-107 composite water-blocking adhesive is used to fill the gap between the waterproof sheath and the insulation layer, resulting in a wet-winding water-resistant cable.

[0070] Comparative Example 1: Other conditions were the same as in Example 1, except that the pyrazolo-1,3,5-triazine in the raw materials for making the insulating layer material was replaced with sodium 2,2'-methylene-bis(4,6-di-tert-butylphenyl)phosphate.

[0071] Comparative Example 2: Other conditions were the same as in Example 1, except that the polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol in the raw materials for making the insulating layer material was replaced with [(2,2,6,6-tetramethyl-4-piperidin)imine].

[0072] Comparative Example 3: Other conditions are the same as in Example 1, except that the raw materials used to make the insulating layer material do not contain ethylene-vinyl acetate copolymer.

[0073] Comparative Example 4: Other conditions are the same as in Example 1, except that the insulating layer material is replaced with cross-linked polyethylene.

[0074] Comparative Example 5: Other conditions are the same as in Example 1, except that the metal-organic framework modified conductive carbon black in the raw materials of the semiconductive layer material is replaced with ordinary conductive carbon black.

[0075] Comparative Example 6: Other conditions are the same as in Example 1, except that the material of the water-blocking sheath layer, nylon 12, is replaced with nylon 6.

[0076] Comparative Example 7: Other conditions are the same as in Example 1, except that the screw used for extruding the insulation layer is a common 65 type screw, the screw diameter in the feeding section is changed to 43±0.3mm, the screw diameter in the compression section is changed to 56±0.2mm, and the screw diameter in the homogenization section is changed to 59±0.2mm.

[0077] The wet-wound water-resistant cables obtained in the above embodiments and comparative examples were subjected to performance tests, and the test methods and standards are as follows:

[0078] Radiation resistance: According to IEEE 323 and IEEE 383, the energy absorption of the cable when the cumulative radiation metering reaches the specified requirements is measured;

[0079] Heat resistance aging: According to IEEE 323, the cumulative heat exposure time of the cable at 125℃ is measured; the Arrhenius formula can be used to predict the life of the cable. Based on the conservative activation energy of 110kJ / mol, the maximum operating temperature of the conductor of 68℃, the expected service life of 60 years, and the aging time margin of 10%, the accelerated heat aging time at 125℃ is calculated to be 2245h. This time can reflect the life under high temperature environment, that is, the heat resistance aging.

[0080] Electrical aging resistance: According to GB / T 29311, the maximum voltage that the cable can withstand under 16 hours of electrical stress loading simulation is determined;

[0081] Water pressure resistance: According to YD / T 2283-2011, after the cable is bathed in a water bath at 15.5MPa and 60℃ for 24 hours, a step withstand voltage test (HVTT) is performed. If the insulation does not break down, it is considered qualified; otherwise, it is unqualified.

[0082] Water tree resistance: ICEA S-94-649-2004, simulates the environment that induces water treeing in a wet winding pump. After the cable is cyclically operated for 120~360 days, a step withstand voltage test (HVTT) is performed. If the insulation does not break down, it is considered qualified; otherwise, it is unqualified.

[0083] The test results are shown in Table 1.

[0084] Table 1: Performance test results of wet-wound water-resistant cables obtained in the examples and comparative examples

[0085] Radiation resistance (kGy) Heat resistance aging (h) Electrical aging resistance (kV) Water pressure resistance Water-resistant trees Example 1 119 2037 24 qualified qualified Example 2 120 2041 25 qualified qualified Example 3 125 2245 26 qualified qualified Comparative Example 1 116 2013 24 Unqualified Unqualified Comparative Example 2 100 2037 25 qualified qualified Comparative Example 3 120 1702 20 qualified qualified Comparative Example 4 98 1634 18 Unqualified Unqualified Comparative Example 5 125 2145 21 qualified Unqualified Comparative Example 6 121 1957 24 Unqualified Unqualified

[0086] First, it should be noted that, normally, the extrusion volume of an extruder can be adjusted by controlling the screw speed. However, if the speed is too low, the material cannot be extruded properly, and other methods must be used to reduce the extrusion volume. The screw used in Comparative Example 7, due to its smaller diameter and deeper thread, extrudes a larger amount of plastic, making it impossible to extrude an insulation layer ≤2.0mm thick. The screw used in Example 1, through improvement, can reduce the extrusion volume without reducing the speed, thereby reducing the thickness of the insulation layer.

[0087] As shown in Table 1, Comparative Example 1, due to the replacement of the polycyclic aromatic hydrocarbon nucleating agent pyrazolo-1,3,5-triazine with the common nucleating agent 2,2'-methylene-bis(4,6-di-tert-butylphenyl)phosphate, failed to meet the standard requirements for water pressure resistance and water tree resistance. Comparative Example 2, by replacing the polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol with [(2,2,6,6-tetramethyl-4-piperidin)imine], resulted in a cable with significantly lower radiation resistance than that of Example 1. The ethylene-vinyl acetate copolymer has a significant impact on the thermal and electrical aging resistance of the cable. Comparative Example 3, which did not include ethylene-vinyl acetate copolymer, had lower thermal aging time and lower electrical aging voltage than Example 1. In Example 1, the insulation layer thickness is ≤2.0mm. This is because the insulation material used has superior performance. If the insulation material is replaced with cross-linked polyethylene, then under the same thickness, all the performance characteristics of the insulation layer will fail to meet the standards, as verified by Comparative Example 4. In Comparative Example 5, the metal-organic framework modified conductive carbon black in the semi-conductive layer material was replaced with ordinary conductive carbon black. There was no difference in radiation resistance and heat aging resistance. However, once subjected to strong voltage or strong water pressure, internal instability factors would occur, leading to a decrease in the cable's resistance to electrical aging, water pressure, and water treeing. Comparative Example 6 shows that Nylon 6 has worse water-blocking performance, making it easier for water to penetrate into the cable, resulting in a decrease in water treeing resistance. The Nylon 12 material used in Example 1 is superior.

[0088] As can be seen from the above description, the present invention has the following advantages: the cable has excellent resistance to radiation, heat aging, electrical aging, water pressure and water treeing, and can meet the performance requirements of wet winding pumps.

[0089] The preferred embodiments of the present invention have been described in detail above with reference to the examples. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0091] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A water-resistant cable with wet windings, characterized in that, It includes, in sequence, a cable conductor, a semi-conductive layer, an insulation layer, and a waterproof sheath layer; The insulating layer, by weight, is made from raw materials comprising the following components: 5-8 parts of ethylene-vinyl acetate copolymer, 75-85 parts of metallocene linear low-density polyethylene, 0-5 parts of high-density polyethylene, 3-7 parts of maleic anhydride-grafted metallocene polyethylene-vinyl acetate copolymer, 1-3 parts of high-temperature antioxidant, 1-4 parts of tris(methacrylate)trimethylolpropane ester, 0.1-0.3 parts of polycyclic aromatic hydrocarbon nucleating agent, 0.5-1.2 parts of absorption-type light stabilizer, and 0.3-0.8 parts of a polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol; wherein the polycyclic aromatic hydrocarbon nucleating agent is pyrazolo-1,3,5-triazine and / or 6,8-diamino-7-nitro-tetrazo[1,5-b]pyridazine; The semiconductive layer, by mass, is made from raw materials comprising the following components: 90-93 parts of ethylene-butyl acrylate copolymer, 2-3 parts of linear low-density polyethylene, 2-4 parts of ethylene-vinyl acetate copolymer, 10-13 parts of metal-organic framework modified conductive carbon black, 5-7 parts of graphene oxide powder, and 2-3 parts of trimethylolpropane.

2. The wet-winding water-resistant cable according to claim 1, characterized in that, The high-temperature resistant antioxidant is selected from one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dilauryl thiodipropionate, tris[2,4-di-tert-butylphenyl]phosphite, N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; the absorbing light stabilizer is selected from one or more of phenyl benzoate, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-(2-hydroxy-5-methylphenyl)benzotriazole, and 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole.

3. The wet-winding water-resistant cable according to claim 1, characterized in that, The waterproof sheath layer is made of nylon 12.

4. The wet-winding water-resistant cable according to claim 1, characterized in that, A composite water-blocking adhesive is also filled between the insulating layer and the waterproof sheath layer.

5. The manufacturing process of the wet-wound water-resistant cable according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) The semiconductive layer and the insulating layer are extruded sequentially onto the surface of the cable conductor, wherein the thickness of the insulating layer is ≤2.0mm, to obtain an insulated wire core; (2) The waterproof sheath layer is extruded over the insulated core to obtain the wet winding water-resistant cable.

6. The production process according to claim 5, characterized in that, The thickness of the semiconductive layer is ≤0.2mm; the thickness of the waterproof sheath layer is ≤0.3mm.

7. The production process according to claim 5, characterized in that, The cable conductor is made by drawing copper rods into wires through a nitriding polishing mold and then annealing them at high temperature and low pressure. The nitriding polishing includes the following steps: (1) Heat the clean mold to 1000~1100℃ for 20~24h; (2) The mold is nitrided with a nitrogen-hydrogen mixture containing 10-20% hydrogen gas for 8-9 hours at a pressure of 0.5-1.5 bar. (3) After the mold has cooled to room temperature, clean the surface impurities to complete the nitriding polishing; The process parameters for the high-temperature low-pressure annealing are: vacuum pressure ≤ -0.1MPa, gas charging pressure 0.35~0.45MPa, heating temperature 420~440℃, holding time 4~6h, and cooling time 18~26h.

8. The production process according to claim 5, characterized in that, The extrusion temperatures of the semiconductive layer are set sequentially to 135±5℃, 150±5℃, 160±5℃, 170±5℃, 175±5℃, 180±5℃, and 185±5℃.

9. The production process according to claim 5, characterized in that, The extrusion temperatures of the insulating layer are set sequentially to 160±5℃, 170±5℃, 175±5℃, 185±5℃, 190±5℃, 195±5℃, and 205±5℃.

10. The production process according to claim 5, characterized in that, The extrusion temperatures of the waterproof sheath layer are set sequentially to 265±5℃, 265±5℃, 275±5℃, 275±5℃, 275±5℃, 265±5℃, and 270±5℃.