High-voltage cable production process based on moisture-proof technology

Abstract

The invention belongs to the technical field of smog moisture content measurement, and discloses a high-voltage cable production process based on a moisture-proof technology, which comprises the following specific steps: step 1, pretreating an insulating raw material, reducing the moisture content of the insulating raw material, carrying out moisture-proof treatment on a conductor and a shielding material, and carrying out drying and dehumidification treatment before raw material processing; and step 2, carrying out moisture-proof strengthening on the key process, and establishing a multi-stage moisture-proof insulating layer. According to the high-voltage cable production process based on the moisture-proof technology, through full-dimensional modification and pretreatment of insulation, conductor and shielding materials, a moisture adsorption path is blocked from the source, materials such as nano montmorillonite and a water repellent agent are added into an XLPE insulation base material, and moisture adsorption is reduced by means of dual effects of physical barrier and chemical hydrophobicity; in cooperation with high-temperature drying treatment, air holes are prevented from being generated during extrusion, and the conductor is subjected to electrolytic polishing to remove an oxide layer and is synchronously coated with a water-blocking material.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of cable production, in particular to a high-voltage cable production process based on moisture-proof technology. BACKGROUND

[0002] As the core carrier of power transmission in the power system, high-voltage cables are widely used in ultra-high voltage power transmission projects, new energy grid connection (such as wind power and photovoltaic power), urban rail transit and submarine cables, and the long-term stable operation of the high-voltage cables directly determines the power supply reliability and safety of the power system. In actual use environment, the high-voltage cables often face complex working conditions such as moisture, rain, high humidity and underwater, and moisture intrusion is one of the core causes of performance degradation and failure of the high-voltage cables.

[0003] However, the existing high-voltage cable production process still has many technical limitations in actual application.

[0004] The preparation process of the temperature-resistant high-voltage cable disclosed in the patent application No. CN202310773551.0 belongs to the technical field of cables and comprises the following steps: step S1, preparation of a temperature-resistant conductor; step S2, wrapping a temperature-resistant insulation layer on the surface of the temperature-resistant conductor by a plastic extruder to obtain a high-voltage cable core; step S3, twisting a plurality of cable cores according to the specification requirements, then wrapping a temperature-resistant filling material outside the twisted cable core to obtain a filled high-voltage cable core; and step S4, wrapping a temperature-resistant shielding layer outside the filled high-voltage cable core, then extruding a temperature-resistant sheath material outside the temperature-resistant shielding layer by a plastic extruder to obtain a temperature-resistant high-voltage cable.

[0005] However, when the existing high-voltage cables are used in a humid environment, they are prone to insulation breakdown, shielding layer corrosion, terminal heating and other failures, which not only shortens the service life of the cables, but also may cause power failure accidents and cause huge economic losses.

[0006] Therefore, it is a key requirement to develop a full-process moisture-proof strengthening process from raw material pretreatment to terminal sealing to solve the problem of the service of high-voltage cables in a humid environment. SUMMARY

[0007] The application aims to provide a high-voltage cable production process based on moisture-proof technology to solve the problem that the existing high-voltage cables are prone to insulation breakdown, shielding layer corrosion, terminal heating and other failures when they are used in a humid environment, which not only shortens the service life of the cables, but also may cause power failure accidents and cause huge economic losses.

[0008] To achieve the above-mentioned purpose, the application provides the following technical scheme: a high-voltage cable production process based on moisture-proof technology, and the specific steps comprise:

[0009] Step one, insulation raw material pretreatment, reduce the moisture content of insulation raw materials, conductor and shielding material moisture-proof treatment, raw material processing drying and dehumidification treatment, insulation raw materials add nano hydrophobic modifier;

[0010] Step two, moisture-proof strengthening of key processes, establish multi-level moisture-proof insulation layer;

[0011] S1, water resistance strengthening of conductor and inner shielding layer;

[0012] S2, improvement of insulation layer extrusion process;

[0013] S3, moisture barrier of shielding layer and sheath layer;

[0014] Step three, cable gap filling and online detection;

[0015] Step four, terminal sealing after cabling, blocking moisture intrusion at the end of the cable.

[0016] Preferably, the step one is specifically: adding nano montmorillonite and hydrophobic agent in XLPE insulation base, the amount of nano montmorillonite is 1% to 3%, the content of fluorosilane coupling agent is less than or equal to 1%, the addition of nano montmorillonite and hydrophobic agent realizes hydrophobic effect and reduces water adsorption.

[0017] By using the above technical solution, the layered physical barrier of nano montmorillonite and the surface "hydrophobic film" formed by fluorosilane coupling agent strengthen the hydrophobic ability of the material itself from physical and chemical dimensions, greatly reduce water adsorption, ensure the stability of the core insulation performance of high-voltage cable in humid environment, and reduce the risk of insulation breakdown.

[0018] Preferably, the raw material is dried and dehumidified before processing, the modified XLPE insulation base is treated by "vacuum drying and hot air circulation" before extrusion, the vacuum degree is less than or equal to-0.095MPa, the temperature is 80-90℃, the time is 2-3h, the water content of the particles is less than 0.02%, and the pores formed by water evaporation during extrusion are avoided.

[0019] By using the above technical solution, the two-stage process is used to realize deep dehumidification, avoid processing defects from the source, and low water content can avoid the formation of pores due to water evaporation during the extrusion of the base material, which ensures that there is no internal gap after the subsequent insulation layer is formed, and lays a foundation for high-quality materials for subsequent extrusion molding.

[0020] Preferably, S1 is specifically: the conductor is polished by electrolytic polishing before being twisted, and the surface oxide layer is removed, and a high-performance composite water-blocking material is coated simultaneously during the conductor twisting process, carbon nanotubes and hydrophobic additives are added to the semi-conductive shielding base material, the carbon nanotubes can improve the uniformity of the conductor, the hydrophobic additives can reduce the adsorption of moisture by the shielding layer, the volume resistivity of the shielding layer is less than or equal to 10Ω·cm, the water absorption rate is less than or equal to 0.1%, and 24h immersion test is required.

[0021] Preferably, the composite water-blocking material is a colloid of superabsorbent polymer nanoparticles and hydrophobic polymer, the hydrophobic polymer being silicone, fluoropolymer.

[0022] With the above technical solution, the conductor electrolytic polishing completely removes the surface oxide layer, eliminates the problem of poor interface contact caused by the oxide layer, and creates a clean adhesion surface for subsequent coating of the water-blocking material, avoiding the corrosion of the conductor caused by the combined action of the oxide layer and moisture. The coated composite water-blocking material can fill the conductor strand gap in real time, block the moisture channel in the gap, and double the moisture absorption by adding a hydrophobic additive in the semiconductive shielding base material. The addition of carbon nanotubes effectively improves the uniformity of the shielding layer, ensuring that the electromagnetic shielding effectiveness of the shielding layer meets the standards. The low water absorption rate also avoids the degradation of the shielding performance caused by moisture.

[0023] Preferably, the multi-level moisture-proof insulation layer in S2 is composed of an inner dense XLPE, a middle moisture-resistant layer, and an outer weather-resistant XLPE;

[0024] The inner dense XLPE is extruded at a low temperature, with an extruder die temperature of 200-210°C to reduce molecular chain breakage and the generation of internal pores, a screw speed of 15-20 r / min, and segmented control of cooling water temperature to maintain an inner layer XLPE porosity of ≤0.05%;

[0025] The middle moisture-resistant layer is simultaneously extruded with a thickness of 0.1-0.2 mm of EVOH, which is tightly combined with the inner XLPE using a hot melt lamination process to avoid interlayer air gaps;

[0026] The outer layer is extruded with weather-resistant XLPE, with the simultaneous addition of antioxidants and ultraviolet absorbers, and the thickness is adjusted according to the voltage level to balance weather resistance and mechanical protection.

[0027] With the above technical solution, the multi-layer extrusion process of the insulation layer forms a three-dimensional moisture-proof system with dense leakage prevention, core moisture resistance, and outer protection, ensuring that the multi-layer structure is tight and suitable for multiple application scenarios, meeting the insulation needs of cables of different voltage levels, and being able to resist external environmental erosion for a long time, ensuring the moisture-proof stability and service life of high-voltage cables under various working conditions.

[0028] Preferably, the shielding layer in S3 includes a semiconductive shielding layer and a metal shielding layer:

[0029] The semiconductive shielding layer is extruded using a longitudinal wrapping and extrusion wrapping composite process, with the modified semiconductive tape wrapped around the insulation layer, a lap rate of ≥20%, and the lap joint sealed with hot melt glue, and then extruding modified semiconductive material to ensure that the shielding layer is free of joints and bubbles, preventing moisture from seeping in through the joints;

[0030] The metal shielding layer is selected to be a double-layer structure of aluminum-plastic composite tape and copper wire braid, the aluminum-plastic composite tape is longitudinally wrapped, the lap joint rate is greater than or equal to 30%, after longitudinal wrapping, the lap joint edges are sealed by laser welding, and the welding strength is greater than or equal to 15 N / cm;

[0031] The outer layer is braid with copper wire, and the braid density is greater than or equal to 90%, so that the shielding effectiveness and the moisture blocking effect are ensured.

[0032] By adopting the above technical scheme, the composite semi-conductive shielding layer winding process is combined with hot melt glue sealing to form a seamless continuous shielding layer, and moisture is prevented from penetrating into the joint, the metal shielding layer adopts a double-layer barrier to form a physical barrier and further intercept moisture penetration.

[0033] Preferably, the sheath layer in S3 is composed of a butyl rubber and an HDPE composite sheath, the inner layer is extruded with butyl rubber, the thickness is 0.5 mm to 1 mm, the outer layer is extruded with high-density polyethylene, the thickness is 2 mm to 3 mm, and hot melt glue is injected at the lap joint of the sheath during extrusion to maintain the complete sealing property of the sheath.

[0034] By adopting the above technical scheme, the sealing structure formed by the sheath can block the invasion of moisture, the hot melt glue is combined to realize the filling of the lap joint gap, and various working conditions such as outdoor rain, soil moisture, acid and alkali environment and the like can be resisted, meanwhile, the thickness design of the double-layer structure takes into account the light weight and the protection strength, and the service life of the cable during outdoor or buried laying is prolonged.

[0035] Preferably, the cable gap filling material in the step three is high-temperature-resistant silane resin, and the filling rate is greater than or equal to 90%, so that the moisture channel formed in the conductor gap is blocked.

[0036] After the insulation layer and the sheath layer are extruded, vacuum detection is performed, the vacuum degree of the vacuum cavity is less than or equal to -0.098 MPa, a small amount of helium gas is filled into the cable, and helium mass spectrometry is used to detect leakage, so that no pinhole, gap or leakage rate less than or equal to 1 x 10-6 Pa·m3 / s is ensured. 9 Pa·m 3 / s.

[0037] By adopting the above technical scheme, the high-temperature-resistant silane resin fills the conductor gap, blocks the gap formed by conductor stranding, utilizes the chemical stability and high-temperature resistance of the silane resin, avoids the generation of gaps due to the shrinkage of traditional filling materials caused by temperature changes, and long-term blocks the channel for moisture penetration along the gap, so that potential moisture-proof hidden dangers are eliminated from the internal structure, and all possible moisture invasion paths are thoroughly investigated before leaving the factory by combining with the detection structure.

[0038] Preferably, the step four specifically includes inner sealing and outer sealing, the inner sealing is that the conductor end is sleeved into a water-absorbing sealing sleeve, a built-in montmorillonite water absorbent is used, and then epoxy resin is poured for sealing, and the outer sealing is that a heat-shrinkable moisture-proof terminal is used, the inner layer is hot melt glue, the outer layer is weather-resistant heat-shrinkable tube, and after heat shrinkage, butyl rubber sealing glue is used to seal the joint between the terminal and the cable sheath.

[0039] By adopting the technical scheme, the inner sealing realizes active moisture absorption and rigid plugging, the built-in water absorbent can actively absorb the trace moisture immersed, and rigid sealing is realized in cooperation with the resin, and the outer sealing adopts a heat-shrinkable sealing mode, can be closely attached to the surface of the cable, and the heat-shrinkable tube can resist external erosion such as ultraviolet rays and rainwater.

[0040] Compared with the prior art, the beneficial effects of the present application are that the high-voltage cable production process based on the moisture-proof technology;

[0041] 1. The cable production process blocks the moisture absorption path from the root by modifying and pretreating the insulation, conductor and shielding material, adds nanometer montmorillonite and hydrophobic agent and other materials in the XLPE insulation base material, reduces moisture absorption by physical barrier and chemical hydrophobic double action, cooperates with high-temperature drying treatment to avoid air holes during extrusion, and the conductor removes the oxide layer by electrolytic polishing and synchronously coats water-blocking material, the above design makes the material itself have moisture resistance, effectively avoids problems such as insulation dielectric loss increase and shielding performance degradation caused by moisture, guarantees the stability of core parameters such as volume resistivity and dielectric loss of the cable in a humid environment, and provides high-quality material support for subsequent structure forming;

[0042] 2. The process forms a multi-layer moisture-proof system by multi-level structure design, greatly improves the overall moisture resistance of the cable, and the multi-layer structure is closely connected without joints and air gaps, forming a three-dimensional moisture-proof system of dense leakage prevention, core moisture resistance and outer protection, which can not only physically block moisture penetration, but also resist erosion in complex environments such as outdoors and buried ground, and adapt to different voltage grade requirements;

[0043] 3. The process realizes a complete moisture-proof system of prevention, detection and plugging through gap filling, high-precision detection and terminal double sealing, uses the resin structure to block the gap between the conductors, cooperates with the double sealing structure to actively absorb trace moisture and block the invasion of the end, and the design eliminates potential moisture channels from the production end and strengthens protection from the end weakness, greatly reducing the risk of cable insulation breakdown, terminal heating and other faults. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The present application is a high-voltage cable production process based on moisture-proof technology. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0046] Please refer toFigure 1 The application provides a technical scheme: a high-voltage cable production process based on moisture-proof technology, and specific steps include:

[0047] Step one, pretreatment of insulation raw materials, reducing the moisture content of insulation raw materials, moisture-proof treatment of conductors and shielding materials, drying and dehumidifying treatment before raw material processing, and adding nano hydrophobic modifier to insulation raw materials;

[0048] Step one is specifically: adding nano montmorillonite and hydrophobic agent to the XLPE insulation base material, the amount of nano montmorillonite is 1% to 3%, and the content of fluorosilane coupling agent is ≤1%, the addition of nano montmorillonite and hydrophobic agent forms a surface hydrophobic film to reduce the adsorption of moisture;

[0049] Drying and dehumidifying treatment is performed before raw material processing, the modified XLPE insulation base material is subjected to "vacuum drying and hot air circulation" double-stage treatment before extrusion operation, the vacuum degree is ≤-0.095 MPa, the temperature is 80-90 DEG C, and the time is 2-3 h, so that the water content of particles is reduced to below 0.02%, internal voids of the subsequent insulation layer are prevented after molding, and water evaporation to form pores during extrusion is avoided.

[0050] Step two, moisture-proof strengthening of key processes, and establishment of a multi-stage moisture-proof insulation layer;

[0051] S1, water blocking strengthening of a conductor and an inner shielding layer;

[0052] S1 is specifically: the conductor is subjected to electrolytic polishing before stranding to remove the surface oxide layer, and high-performance composite water blocking material is coated synchronously in the conductor stranding process, the electrolytic polishing of the conductor can remove the surface oxide layer and provide a clean adhesion surface for the water blocking material;

[0053] Carbon nanotubes and hydrophobic aids are added to the semi-conductive shielding base material, the carbon nanotubes can improve the uniformity of conduction, the hydrophobic aids can reduce the adsorption of moisture by the shielding layer, the volume resistivity of the shielding layer is ≤10 Ω·cm, the water absorption rate is ≤0.1%, and 24 h immersion test is needed;

[0054] The composite water blocking material is a colloid composed of superabsorbent polymer nanoparticles and hydrophobic polymers, and the hydrophobic polymers are silicone and fluoropolymer.

[0055] S2, improvement of an extrusion process of an insulation layer;

[0056] The multi-stage moisture-proof insulation layer in S2 is composed of an inner dense XLPE, an intermediate moisture-proof layer and an outer weather-resistant XLPE;

[0057] The inner dense XLPE is extruded at low temperature, the die temperature of the extruder is 200-210℃, the screw rotation speed is 15-20r / min, and the cooling water temperature is controlled in stages to keep the porosity of the inner XLPE layer ≤0.05%;

[0058] The intermediate moisture-proof layer is synchronously extruded to a thickness of 0.1-0.2mm EVOH, which is tightly combined with the inner XLPE layer by hot melt lamination process to avoid air gap between the layers;

[0059] The outer layer is extruded with weather-resistant XLPE, and antioxidants and ultraviolet absorbers are synchronously added, and the thickness is adjusted according to the voltage level to balance the weather resistance and mechanical protection;

[0060] The design of the multi-layer insulation layer meets the insulation requirements of cables of different voltage levels and can resist external environmental erosion for a long time to ensure the moisture-proof stability and service life of high-voltage cables under various working conditions.

[0061] S3, moisture-proof barrier of the shielding layer and the sheath layer;

[0062] The shielding layer in S3 includes a semi-conductive shielding layer and a metal shielding layer:

[0063] The semi-conductive shielding layer is longitudinally wrapped and extrusion-coated with a modified semi-conductive tape, the overlap rate is ≥20%, the overlap joint is sealed with hot melt glue, and then the modified semi-conductive material is extruded to ensure that the shielding layer is free of joints and bubbles and to prevent moisture from penetrating through the joints;

[0064] The metal shielding layer is a double-layer structure of aluminum-plastic composite tape and copper wire braid, the aluminum-plastic composite tape is longitudinally wrapped, and the overlap rate is ≥30%, and the longitudinally wrapped layer is sealed with laser welding after the overlap joint, and the welding strength is ≥15N / cm;

[0065] The outer layer is braided with copper wire, and the braiding density is ≥90% to ensure the shielding effectiveness and moisture blocking effect;

[0066] The sheath layer is composed of a butyl rubber and a HDPE composite sheath, the inner layer is extruded with butyl rubber with a thickness of 0.5mm-1mm, and the outer layer is extruded with high-density polyethylene with a thickness of 2-3mm, hot melt glue is injected at the overlap joint during extrusion to maintain the complete sealing of the sheath, and the double shielding structure forms a physical barrier to improve the moisture interception effect.

[0067] Step three, cable gap filling and online detection;

[0068] The cable gap filling material in step three is high-temperature resistant silane resin with a filling rate of ≥90% to block the moisture channel formed in the conductor gap;

[0069] After the insulation layer and the sheath layer are extruded, vacuum detection is performed, the vacuum degree of the vacuum cavity is less than or equal to-0.098 MPa, a trace amount of helium is filled in the cable, and helium mass spectrometry is used to ensure that there are no pinholes, gaps, and the leakage rate is less than or equal to 1*10- 9 Pa·m 3 / s.

[0070] Step four, sealing of the terminal after cabling, blocking the moisture from entering the end of the cable;

[0071] Step four specifically includes internal sealing and external sealing. The internal sealing is that the conductor end is sleeved into a water-absorbing sealing sleeve, a built-in montmorillonite water absorbent is used, and then epoxy resin is filled, so that the internal sealing realizes active moisture absorption and rigid plugging, and the built-in water absorbent can actively absorb a trace amount of moisture.

[0072] The external sealing is that a heat-shrinkable moisture-proof terminal is used, the inner layer is a hot melt adhesive, the outer layer is a weather-resistant heat-shrinkable tube, after heat shrinkage, butyl rubber sealing glue is used to seal the joint between the terminal and the cable sheath, the external sealing uses a heat-shrinkable sealing method, can tightly fit the surface of the cable, and the heat-shrinkable tube can resist external erosion such as ultraviolet rays and rainwater.

[0073] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

[0074] In addition, any combination of the various embodiments of the present application can also be made, as long as it does not deviate from the idea of the present application, it should also be considered as disclosed by the present application.

[0075] In summary, the above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high voltage cable production process based on moisture-proof technology, characterized in that: The specific steps include: Step 1: Pre-treat the insulating raw materials, reduce the moisture content of the insulating raw materials, moisture-proof the conductors and shielding materials, dry and dehumidify the raw materials before processing, and add nano-hydrophobic modifiers to the insulating raw materials; Step 2: Strengthen moisture-proofing of key processes and establish a multi-level moisture-proof insulation layer; S1, Conductor and inner shielding layer water-blocking reinforcement; S2. Improvement of the extrusion process of the insulation layer; S3, moisture barrier of shielding layer and sheath layer; Step 3: Cable gap filling and online testing; Step 4: Seal the terminal after cabling to prevent moisture from entering the cable end.

2. A high-voltage cable production process based on moisture-proof technology according to claim 1, characterized in that: The step 1 specifically comprises: adding nano-montmorillonite and a hydrophobic agent to the XLPE insulation base material, wherein the amount of nano-montmorillonite is 1% to 3% and the content of fluorosilane coupling agent is ≤1%. The addition of nano-montmorillonite and the hydrophobic agent realizes a hydrophobic effect and reduces the adsorption of water.

3. A high voltage cable production process based on moisture proof technology according to claim 2, characterized in that: The raw materials are dried and dehumidified before processing. The modified XLPE insulation base material is subjected to a double-stage treatment of "vacuum drying and hot air circulation" before extrusion, with a vacuum degree of ≤-0.095MPa, a temperature of 80-90°C, and a time of 2-3h, thereby reducing the moisture content of the particles to below 0.02% and preventing the formation of pores due to evaporation of water during extrusion.

4. A high voltage cable production process based on moisture proof technology according to claim 1, characterized in that: S1 specifically includes: the conductors are electrolytically polished before twisting to remove the surface oxide layer. During the conductor twisting process, high-performance composite water-blocking materials are simultaneously coated. Carbon nanotubes and hydrophobic additives are added to the semi-conductive shielding base material. Carbon nanotubes can improve the uniformity of conductivity, and hydrophobic additives can reduce the adsorption of moisture by the shielding layer, maintaining the volume resistivity of the shielding layer ≤10Ω·cm and the water absorption rate ≤0.1%. A 24-hour immersion test is required.

5. A high voltage cable production process based on moisture proof technology according to claim 4, characterized in that: The composite water-blocking material is a colloid formed by super absorbent polymer nanoparticles and hydrophobic polymers, wherein the hydrophobic polymers include silicone and fluoropolymers.

6. A high voltage cable production process based on moisture proof technology according to claim 1, characterized in that: The multi-level moisture-proof insulation layer in S2 is composed of: inner layer of dense XLPE, middle layer of moisture barrier, and outer layer of weather-resistant XLPE; The inner layer of dense XLPE is extruded at low temperature, with the extruder die temperature of 200-210℃ to reduce molecular chain breakage and the generation of internal pores. The screw speed is 15-20r / min, and the cooling water temperature is controlled in stages to maintain the porosity of the inner layer XLPE ≤0.05%; The middle moisture barrier layer is extruded with 0.1-0.2mm thick EVOH, which is tightly bonded to the inner layer of XLPE using a hot melt bonding process to avoid air gaps between layers. The outer layer is extruded with weather-resistant XLPE, with antioxidants and UV absorbers added simultaneously. The thickness is adjusted according to the voltage level, taking into account both weather resistance and mechanical protection.

7. A high voltage cable production process based on moisture proof technology according to claim 1, characterized in that: The shielding layer in S3 includes a semi-conductive shielding layer and a metallic shielding layer: Semi-conductive shielding layer: Using a composite process of longitudinal wrapping and extrusion, the modified semi-conductive tape is longitudinally wrapped around the insulating layer with an overlap rate of ≥20%. The overlap seams are sealed with hot melt adhesive, and then the modified semi-conductive material is extruded to ensure that the shielding layer is seamless and free of bubbles, preventing moisture from penetrating through the seams. The metal shielding layer adopts a double-layer structure of aluminum-plastic composite tape and copper wire braiding. The aluminum-plastic composite tape is longitudinally wrapped with an overlap rate of ≥30%. After longitudinal wrapping, the overlap edge is sealed by laser welding with a welding strength of ≥15N / cm; The outer layer is braided with copper wire, and the braiding density is ≥90%, ensuring the shielding effectiveness and moisture blocking effect.

8. A high voltage cable production process based on moisture proof technology according to claim 1, characterized in that: The sheath layer of S3 is composed of a composite sheath of butyl rubber and HDPE. The inner layer is extruded with butyl rubber with a thickness of 0.5mm to 1mm, and the outer layer is extruded with high-density polyethylene with a thickness of 2 to 3mm. During extrusion, hot melt adhesive is injected into the overlap of the sheath to keep the sheath completely sealed.

9. A high voltage cable production process based on moisture proof technology according to claim 1, characterized in that: The cable gap filler in step 3 is a high-temperature resistant silane resin with a filling rate of ≥90%, which prevents the formation of moisture channels in the conductor gaps; After the insulation layer and the sheath layer are extruded, vacuum testing is carried out. The vacuum degree of the vacuum chamber is ≤-0.098MPa. A small amount of helium is filled inside the cable. Helium mass spectrometry is used to detect leaks to ensure that there are no pinholes or gaps. The leakage rate is ≤1×10- 9 Pa·m 3 / s.

10. A high voltage cable production process based on moisture proof technology according to claim 1, characterized in that: Step four specifically includes internal sealing and external sealing. Internal sealing: the conductor end is put into a water-absorbing sealing sleeve with a built-in montmorillonite water absorbent, and then sealed with epoxy resin. External sealing: a heat-shrinkable moisture-proof terminal is used, with an inner layer of hot melt adhesive and an outer layer of weather-resistant heat shrink tube. After heat shrinkage, butyl rubber sealant is used to seal the joint between the terminal and the cable sheath.

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