High-flame-retardant corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable

Abstract

The invention discloses a high-flame-retardant corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable which comprises a copper core material, an XLPE insulating layer arranged on the outer side of the copper core material, a composite corrosion-resistant shielding layer arranged on the outer side of the XLPE insulating layer and a flame-retardant glass fiber belting layer arranged on the outer side of the composite corrosion-resistant shielding layer. According to the invention, the XLPE insulating layer is combined with the cross-linked polyethylene matrix and the composite flame-retardant shell material, so that the synergistic enhancement of high insulating strength and flame-retardant property is realized; the composite anti-corrosion shielding layer effectively resists chemical corrosion and mechanical damage through multiple protection of an aluminum-plastic composite belt and an epoxy-polysiloxane coating; and the flame-retardant glass fiber belting layer forms a heat-insulating barrier which quickly reacts when encountering fire through ceramic flame-retardant liquid dipping and a double-layer wrapping process, so that the whole cable has the characteristics of high flame retardance and corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of cable preparation, and specifically relates to a high-flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable. Background Art

[0002] As the core carrier of electric energy transmission, medium-voltage power cables are widely used in urban distribution networks, industrial power supply systems, rail transit, and new energy fields. Due to problems such as low temperature resistance grade, flammability, and easy aging of traditional polyvinyl chloride, it has become difficult to meet the stringent requirements of modern power grids for fire prevention and corrosion resistance.

[0003] Since the 1960s, cross-linked polyethylene has gradually replaced PVC as the mainstream insulation material for medium-voltage cables due to its excellent electrical properties, heat resistance, and mechanical strength. Its cross-linking process forms a three-dimensional network structure, significantly improving the material's resistance to thermal deformation and environmental stress cracking. However, conventional XLPE cables still have the following limitations:

[0004] The limiting oxygen index of ordinary XLPE is relatively low. When burning, it releases a large amount of heat and toxic smoke, easily causing the spread of fire; in an environment of acid rain, salt spray, or chemical pollution, the cable sheath is easily eroded, resulting in deterioration of insulation performance and even breakdown faults.

[0005] To meet the flame-retardant requirements of cables, existing cables improve the flame-retardant grade of XLPE through composite modification and structural optimization: forming a halogen-free flame-retardant system, using environmentally friendly flame retardants such as aluminum hydroxide and magnesium hydroxide, and improving the LOI through filling modification. At the same time, it can also reduce the release of smoke and toxins, but its flame-retardant and corrosion-resistant properties are still not ideal. Summary of the Invention

[0006] The problem existing in the prior art is that the flame-retardant and corrosion-resistant properties of existing cables are weak. To solve the above technical problems, the present invention provides a high-flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable.

[0007] The technical solution of the present invention is: a high-flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable, including a copper core material, an XLPE insulation layer arranged outside the copper core material, a composite anti-corrosion shielding layer arranged outside the XLPE insulation layer, and a flame-retardant fiberglass tape layer arranged outside the composite anti-corrosion shielding layer; the thickness of the XLPE insulation layer is 4.5 - 5.5 mm, the thickness of the composite anti-corrosion shielding layer is 0.4 - 0.6 mm, and the single-layer thickness of the flame-retardant fiberglass tape layer is 0.1 - 0.4 mm.

[0008] Description: The high flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable described in the present invention adopts a multi-layer composite structure design. The copper core material optimizes the conductor flexibility and conductivity through a five-layer stranded annealing process. The XLPE insulation layer realizes the synergistic enhancement of the insulation matrix and the flame-retardant shell material through a double-layer synchronous extrusion technology. The composite anti-corrosion shielding layer combines an aluminum-plastic composite tape and an epoxy-polysiloxane coating to form multiple anti-corrosion barriers. The flame-retardant fiberglass tape layer improves the flame-retardant performance through high-concentration flame-retardant liquid impregnation and double-layer winding process; the thickness of each layer of material is precisely designed. The thickness of the XLPE insulation layer is 4.5 - 5.5 mm to balance the insulation strength and mechanical reliability. The thickness of the composite anti-corrosion shielding layer is 0.4 - 0.6 mm to balance the electromagnetic shielding and corrosion resistance requirements. The single-layer thickness of the flame-retardant fiberglass tape layer is 0.1 - 0.3 mm to ensure the flame-retardant efficiency and structural compactness.

[0009] Further, the preparation method of the copper core material is as follows: Annealed copper single wires with a diameter of 0.15 - 0.25 mm are used and stranded in five layers. The number of stranded wires from the center to the outside is successively: 1, 6, 12, 18, 24. The stranding pitches from the center to the outside are successively 10 times, 12 times, 14 times, 16 times, 18 times the conductor diameter. The stranding direction is alternately right-handed and left-handed. After stranding, a conductor is obtained, and then the conductor is introduced into an annealing furnace under inert gas protection for treatment. The annealing temperature is 440 - 460 °C, the holding time is 1.5 - 2.5 h, and it is cooled to room temperature at a cooling rate of 1 - 5 °C / min to obtain the copper core material.

[0010] Description: The copper core material adopts a five-layer stranded structure and strictly controls the annealing process, enabling the conductor to have high conductivity and flexibility. The stranding pitch increases layer by layer and the direction alternates, effectively releasing internal stress. Combined with inert gas protection annealing, oxidation is avoided and the grains are refined, ensuring the structural stability and signal transmission efficiency of the copper core material.

[0011] Further, the XLPE insulation layer is composed of an insulation matrix and a flame-retardant shell material on the surface of the insulation matrix; the preparation method of the XLPE insulation layer is as follows: The insulation matrix and the flame-retardant shell material are transported to a co-extrusion die head through two extruders for synchronous extrusion. The inner channel of the co-extrusion die head circulates the insulation matrix, and the outer channel circulates the flame-retardant shell material. The insulation matrix and the flame-retardant shell material converge 5 - 7 cm before the outlet of the co-extrusion die head. A die core corresponding to the diameter of the copper core material is arranged at the center of the inner channel of the co-extrusion die head. The extrusion temperature of the insulation matrix is 160 - 180 °C, the extrusion temperature of the flame-retardant shell material is 170 - 190 °C, and the screw compression ratio of both extruders is 3:1.

[0012] Description: The XLPE insulating layer is formed into a double-layer composite structure by synchronously extruding an insulating matrix and a flame-retardant shell material. The insulating matrix provides excellent electrical performance, and the flame-retardant shell material enhances the fire resistance ability. The interface between the two is tightly combined, and the synchronous extrusion process avoids delamination, enabling the insulating layer to have both high-voltage resistance and flame-retardant properties.

[0013] Furthermore, the preparation method of the insulating matrix is as follows: 1.5 - 2.5 wt% of dicumyl peroxide cross-linking agent and the balance of low-density polyethylene are introduced into a kneader, kneaded at 105 - 115 °C and a rotation speed of 35 - 45 rpm for 14 - 16 min. After mixing evenly, it is extruded and coated on the conductor through a single-screw extruder in the temperature range of 160 - 180 °C to form an insulating layer with a thickness of 1.5 - 2.5 mm. Subsequently, it enters a nitrogen-pressurized cross-linking pipeline, is heated to 250 - 350 °C at a rate of 4 - 6 °C / min and maintained for 10 min, and then cross-linked at a temperature of 350 - 370 °C and a pressure of 1.4 - 1.6 MPa for 44 - 46 min to obtain the insulating matrix.

[0014] Description: After kneading low-density polyethylene and dicumyl peroxide cross-linking agent and then performing high-temperature cross-linking, the gradient heating and high-pressure environment in the cross-linking pipeline promote the cross-linking of polyethylene molecular chains to form a three-dimensional network structure, significantly improving the heat resistance, mechanical strength, and long-term aging stability of the insulating matrix.

[0015] Furthermore, the preparation method of the flame-retardant shell material is as follows: By mass percentage, 1.5 - 2.5% of nano-montmorillonite modified with silane coupling agent, 9 - 11% of magnesium hydroxide, 7 - 9% of aluminum hydroxide, 7 - 9% of ethylene-vinyl acetate, 0.5 - 0.7% of antioxidant, 0.2 - 0.4% of lubricant, and the balance of low-density polyethylene are weighed; the low-density polyethylene and ethylene-vinyl acetate are mixed at 500 rpm, and then the dried modified nano-montmorillonite and sieved magnesium hydroxide and aluminum hydroxide are evenly added, and then the antioxidant and lubricant are added. The rotation speed is increased to 3000 rpm, and shear mixing is carried out at 120 °C for 18 - 22 min.

[0016] The flame-retardant material is obtained, and the flame retardant is embedded between the MMT layers; the flame-retardant material is cooled to 55 - 65 °C, impurities are removed through a 100-mesh vibrating screen and an 8000-gauss magnetic separator, and then it is put into a twin-screw extruder and granulated at a temperature of 150 - 175 °C and a rotation speed of 120 rpm to obtain the flame-retardant shell material.

[0017] Description: The flame-retardant shell material synergistically acts through modified nano-montmorillonite and hydroxide flame retardants. The flame retardant particles are embedded between the nano-montmorillonite layers, and the compatibility is improved through ethylene-vinyl acetate to form a dense barrier layer, delaying the spread of fire and inhibiting the release of soot, while maintaining the flexibility of the material.

[0018] Further, the preparation method of the composite anti-corrosion shielding layer is as follows: an aluminum strip with a thickness of 0.1 - 0.2 mm is subjected to electrochemical polishing treatment to make its surface roughness reach Ra 0.8 μm, and then it is hot-pressed and compounded with a polyethylene film with a thickness of 0.05 - 0.06 mm through hot melt adhesive at a temperature of 180 °C and a pressure of 0.8 MPa to form an aluminum-plastic composite strip; then, an epoxy-polysiloxane anti-corrosion coating is sprayed on the surface of the aluminum-plastic composite strip to obtain the composite anti-corrosion shielding layer.

[0019] Explanation: The composite anti-corrosion shielding layer is composed of an aluminum-plastic composite strip and an epoxy-polysiloxane coating. After electrochemical polishing, the surface roughness of the aluminum strip is reduced. The hot-pressing and compounding process ensures no bubbles at the aluminum-plastic interface. The epoxy-polysiloxane coating provides a chemically inert barrier to resist corrosion by acids, alkalis, salts and the erosion of a humid environment.

[0020] Further, the electrolyte for the electrochemical polishing treatment is a mixed solution with a mass ratio of phosphoric acid to sulfuric acid of 3 - 4:1, the concentration of phosphoric acid is greater than or equal to 85 wt%, the concentration of sulfuric acid is greater than or equal to 98 wt%, the current density is 10 A / dm 2 , the time is 4 - 6 min, the coating amount of the hot melt adhesive is 8 g / m 2 , and the raw material of the hot melt adhesive is ethylene-vinyl acetate copolymer.

[0021] Explanation: The electrochemical polishing process uses a mixed solution of phosphoric acid and sulfuric acid to control the surface morphology. The current density and time match the dissolution rate of the aluminum strip to obtain a smooth surface. The coating amount of the hot melt adhesive is precisely controlled. The ethylene-vinyl acetate copolymer bonds the aluminum strip and the polyethylene film, enhancing the mechanical strength and sealing performance of the shielding layer.

[0022] Further, the method for spraying the epoxy-polysiloxane anti-corrosion coating on the surface of the aluminum-plastic composite strip is as follows: 25 - 35 wt% of polysiloxane prepolymer, 4 - 6 wt% of nano-zinc oxide, 4 - 6 wt% of KH-560 coupling agent and the balance of epoxy resin E-51 are mixed and stirred at a speed of 2000 rpm for 30 - 35 min to obtain the epoxy-polysiloxane anti-corrosion coating. The epoxy-polysiloxane anti-corrosion coating with a thickness of 0.1 - 0.15 mm is sprayed on the surface of the aluminum-plastic composite strip by an electrostatic spraying process, and then it is introduced into an infrared curing oven at 80 °C for curing for 40 min. After curing, the spraying of the epoxy-polysiloxane anti-corrosion coating is completed; the voltage of the electrostatic spraying process is 60 kV, and the spraying distance is 190 - 210 mm.

[0023] Explanation: The epoxy-polysiloxane anti-corrosion coating enhances the coating adhesion through nano-zinc oxide and KH-560 coupling agent, and the polysiloxane prepolymer improves the weather resistance. The electrostatic spraying process realizes uniform coating coverage. After infrared curing, a dense cross-linked film is formed, effectively isolating the penetration of corrosive media.

[0024] Furthermore, the preparation step of the flame retardant glass fiber tape layer is as follows: 2 The halogen-free glass fiber tape is immersed in the flame retardant liquid at a speed of 5-6 m / min for 25-35 seconds to ensure that the liquid absorption reaches 50-70%; it is then dried in a hot air circulation oven at 110-130°C for 15-25 minutes, and after drying, it is wrapped around the composite anti-corrosion shielding layer in a double-layer overlapping manner to form a flame retardant glass fiber tape layer.

[0025] Description: The flame-retardant glass fiber tape layer adopts halogen-free glass fiber tape impregnated with high-concentration magnesium hydroxide flame retardant liquid, and the silane coupling agent improves the interface bonding between the flame retardant and the glass fiber. After drying, the glass fiber tape forms a ceramic protective layer, and the double-layer overlapping and wrapping enhances the tightness of the coating, and quickly forms a heat insulation barrier when encountering fire.

[0026] Furthermore, the flame retardant liquid is composed of a mixture of 35-55wt% of magnesium hydroxide, 3-5wt% of a silane coupling agent and the remainder of an acrylic ester emulsion.

[0027] Description: The flame retardant liquid forms a film through high-content magnesium hydroxide and acrylic emulsion, silane coupling agent promotes the dispersion of flame retardant, and the impregnation process controls the liquid absorption, ensuring that the flame retardant performance of the glass fiber tape is stable and halogen-free and environmentally friendly, achieving the requirements of low smoke and non-toxicity when the cable burns.

[0028] The beneficial effects of the present invention are:

[0029] The present invention significantly improves the conductivity and fatigue resistance of the conductor by optimizing the twisted structure and annealing process of the copper core material; the XLPE insulation layer adopts double-layer synchronous extrusion technology, combined with a cross-linked polyethylene matrix and a composite flame-retardant shell material, to achieve a synergistic enhancement of high insulation strength and flame retardant properties; the composite anti-corrosion shielding layer effectively resists chemical corrosion and mechanical damage through multiple protections of aluminum-plastic composite tape and epoxy-polysiloxane coating; the flame-retardant glass fiber tape layer is impregnated with ceramic flame retardant liquid and a double-layer wrapping process to form an insulating barrier that reacts quickly to fire. The synergistic effect of each layer of material and process makes the cable as a whole have the characteristics of high flame retardancy, corrosion resistance, high voltage resistance and long life, and is suitable for medium-voltage power transmission scenarios in harsh environments such as chemical and marine environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a line graph of limiting oxygen index test of samples of Examples 1 to 17 of the present invention and Comparative Examples 1 to 3;

[0031] Figure 2 is a line graph of corrosion performance test of samples of Examples 1 to 17 of the present invention;

[0032] Figure 3 It is a line graph of the corrosion performance test of samples of comparative examples 1 to 3 of the present invention;

[0033] Figure 4 is the line graph of the sample smoke density test for Embodiments 1 to 17 of the present invention;

[0034] Figure 5 is the line graph of the sample smoke density test for Comparative Examples 1 to 3 of the present invention. Detailed Embodiments

[0035] To further elaborate on the methods adopted and the effects achieved by the present invention, the technical solutions of the present invention will be clearly and completely described below in combination with experiments.

[0036] Embodiment 1:

[0037] A medium-voltage cross-linked polyethylene insulated power cable with high flame retardancy and corrosion resistance, comprising a copper core material, an XLPE insulation layer provided on the outer side of the copper core material, a composite anti-corrosion shielding layer provided on the outer side of the XLPE insulation layer, and a flame-retardant fiberglass tape layer provided on the outer side of the composite anti-corrosion shielding layer; the thickness of the XLPE insulation layer is 4 mm, the thickness of the composite anti-corrosion shielding layer is 0.5 mm, and the single-layer thickness of the flame-retardant fiberglass tape layer is 0.25 mm;

[0038] The preparation method of the copper core material is as follows: Using annealed copper single wires with a diameter of 0.2 mm, stranded in five layers, the number of strands from the center to the outside is successively: 1 strand, 6 strands, 12 strands, 18 strands, 24 strands, and the stranding pitches from the center to the outside are successively 10 times, 12 times, 14 times, 16 times, 18 times the conductor diameter, and the stranding direction is alternately rightward and leftward. After stranding, a conductor is obtained, and then the conductor is introduced into an annealing furnace under inert gas protection for treatment. The annealing temperature is 450 °C, the holding time is 2 h, and it is cooled to room temperature at a cooling rate of 3 °C / min to obtain the copper core material;

[0039] The XLPE insulation layer is composed of an insulation matrix and a flame-retardant shell material on the surface of the insulation matrix;

[0040] The preparation method of the insulation matrix is as follows: 2 wt% of dicumyl peroxide cross-linking agent and the balance of low-density polyethylene are introduced into a mixer, kneaded at 110 °C and a rotation speed of 40 rpm for 15 min. After mixing evenly, it is extruded and coated on the conductor through a single-screw extruder in a temperature range of 170 °C to form an insulation layer with a thickness of 2 mm. Subsequently, it enters a nitrogen-pressurized cross-linking pipeline, is heated to 300 °C at a rate of 5 °C / min and maintained for 10 min, and then cross-linked at a temperature of 360 °C and a pressure of 1.5 MPa for 45 min to obtain the insulation matrix;

[0041] The preparation method of the flame-retardant shell material is as follows: Weigh 2wt% of modified nano-montmorillonite, 10wt% of magnesium hydroxide, 8wt% of aluminum hydroxide, 8wt% of ethylene-vinyl acetate, 0.6wt% of antioxidant, 0.3wt% of lubricant, and the balance of low-density polyethylene; Mix the low-density polyethylene and ethylene-vinyl acetate at 500 rpm, then uniformly add the dried modified nano-montmorillonite, sieved magnesium hydroxide, and aluminum hydroxide, and then add the antioxidant and lubricant. Raise the rotation speed to 3000 rpm and shear-mix at 120 °C for 20 min to obtain a flame-retardant material; Cool the flame-retardant material to 60 °C, remove impurities through a 100-mesh vibrating screen and an 8000-Gauss magnetic separator, and then put it into a twin-screw extruder to granulate at a temperature of 162.5 °C and a rotation speed of 120 rpm to obtain the flame-retardant shell material;

[0042] The preparation method of the XLPE insulation layer is as follows: The insulation matrix and the flame-retardant shell material are conveyed to a co-extrusion die head by two extruders for synchronous extrusion. The inner channel of the co-extrusion die head circulates the insulation matrix, and the outer channel circulates the flame-retardant shell material. The inner diameter of the outer channel is narrower than that of the inner channel. The insulation matrix and the flame-retardant shell material converge 6 cm before the outlet of the co-extrusion die head. A die core corresponding to the diameter of the copper core material is arranged at the center of the inner channel of the co-extrusion die head. The extrusion temperature of the insulation matrix is 170 °C, and the extrusion temperature of the flame-retardant shell material is 180 °C. The screw compression ratios of the two extruders are both 3:1;

[0043] The preparation method of the composite anti-corrosion shielding layer is as follows: An aluminum strip with a thickness of 0.15 mm is subjected to electrochemical polishing treatment to make its surface roughness reach Ra 0.8 μm, and then it is thermocompression-bonded with a polyethylene film with a thickness of 0.055 mm through hot-melt adhesive at a temperature of 180 °C and a pressure of 0.8 MPa to form an aluminum-plastic composite strip; Then, an epoxy-polysiloxane anti-corrosion coating is sprayed on the surface of the aluminum-plastic composite strip to obtain the composite anti-corrosion shielding layer;

[0044] The electrolyte for the electrochemical polishing treatment is a mixed solution with a mass ratio of phosphoric acid to sulfuric acid of 3.5:1. The concentration of phosphoric acid is 90wt%, the concentration of sulfuric acid is 99wt%, the current density is 10 A / dm 2 ², the time is 5 min, the coating amount of the hot-melt adhesive is 8 g / m 2 ², and the raw material of the hot-melt adhesive is ethylene-vinyl acetate copolymer;

[0045] The method for spraying the epoxy-polysiloxane anti-corrosion coating on the surface of the aluminum-plastic composite tape is as follows: Mix 30 wt% of polysiloxane prepolymer, 5 wt% of nano-zinc oxide, 5 wt% of KH-560 coupling agent and the balance of epoxy resin E-51, stir at a speed of 2000 rpm for 32.5 min to obtain the epoxy-polysiloxane anti-corrosion coating. Use the electrostatic spraying process to spray the epoxy-polysiloxane anti-corrosion coating with a thickness of 0.12 mm on the surface of the aluminum-plastic composite tape, and then introduce it into an infrared curing oven at 80 °C for curing for 40 min. After curing, the spraying of the epoxy-polysiloxane anti-corrosion coating is completed; the voltage of the electrostatic spraying process is 60 kV, and the spraying distance is 200 mm;

[0046] The preparation steps of the flame-retardant glass fiber tape layer are as follows: Immerse the halogen-free glass fiber tape with a weight of 200 g / m of the composite anti-corrosion shielding layer in the flame-retardant liquid at an immersion speed of 5.5 m / min for 30 s to ensure that the liquid absorption amount reaches 60%; then dry it in a hot air circulation oven at 120 °C for 20 min to increase the oxygen index of the glass fiber tape to 35%; after drying, wrap it around the outside of the composite anti-corrosion shielding layer in a double-layer overlapping wrapping method, and the tension control of the wrapping machine is 15 N, and the overlapping rate is 50% to form a flame-retardant glass fiber tape layer that can be ceramized under fire; 2 The flame-retardant liquid is composed of 45 wt% of magnesium hydroxide, 4 wt% of silane coupling agent and the balance of acrylate emulsion.

[0047] The flame-retardant liquid is composed of 45 wt% of magnesium hydroxide, 4 wt% of silane coupling agent and the balance of acrylate emulsion.

[0048] Example 2: This example is basically the same as Example 1, except that the thickness of the XLPE insulation layer is 4.5 mm, the thickness of the composite anti-corrosion shielding layer is 0.4 mm, and the single-layer thickness of the flame-retardant glass fiber tape layer is 0.1 mm; annealed copper single wires with a diameter of 0.15 mm are stranded in five layers.

[0049] Example 3: This example is basically the same as Example 1, except that the thickness of the XLPE insulation layer is 5.5 mm, the thickness of the composite anti-corrosion shielding layer is 0.6 mm, and the single-layer thickness of the flame-retardant glass fiber tape layer is 0.4 mm; annealed copper single wires with a diameter of 0.25 mm are stranded in five layers.

[0050] Example 4: This example is basically the same as Example 1, except that then the conductor is introduced into an annealing furnace under inert gas protection for treatment, the annealing temperature is 440 °C, the holding time is 1.5 h, and it is cooled to room temperature at a cooling rate of 1 °C / min to obtain the copper core material.

[0051] Example 5: This example is basically the same as Example 1, except that the conductor is then introduced into an annealing furnace under inert gas protection for treatment. The annealing temperature is 460 °C, the holding time is 2.5 h, and it is cooled to room temperature at a cooling rate of 5 °C / min to obtain a copper core material.

[0052] Example 6: This example is basically the same as Example 1, except that the preparation method of the XLPE insulating layer is as follows: The insulating matrix and the flame-retardant shell material are conveyed to a co-extrusion die head by two extruders for synchronous extrusion. The inner channel of the co-extrusion die head conducts the insulating matrix, and the outer channel conducts the flame-retardant shell material. The inner diameter of the outer channel is narrower than that of the inner channel. The insulating matrix and the flame-retardant shell material converge 5 cm before the outlet of the co-extrusion die head. A die core corresponding to the diameter of the copper core material is provided at the center of the inner channel of the co-extrusion die head. The extrusion temperature of the insulating matrix is 160 °C, and the extrusion temperature of the flame-retardant shell material is 170 °C. The screw compression ratios of the two extruders are both 3:1. The preparation method of the insulating matrix is as follows: 1.5 wt% of dicumyl peroxide cross-linking agent and the balance of low-density polyethylene are introduced into a kneader and kneaded at 105 °C and a rotation speed of 35 rpm for 14 min. After mixing evenly, it is extruded and coated on the conductor in a temperature range of 160 °C by a single-screw extruder to form an insulating layer with a thickness of 1.5 mm, and then enters a nitrogen-pressurized cross-linking pipeline, is heated to 250 °C at a rate of 4 °C / min and maintained for 10 min, and then cross-linked at a temperature of 350 °C and a pressure of 1.4 MPa for 44 min to obtain the insulating matrix.

[0053] Example 7: This example is basically the same as Example 1, except that the preparation method of the XLPE insulating layer is as follows: The insulating matrix and the flame-retardant shell material are conveyed to a co-extrusion die head by two extruders for synchronous extrusion. The inner channel of the co-extrusion die head conducts the insulating matrix, and the outer channel conducts the flame-retardant shell material. The inner diameter of the outer channel is narrower than that of the inner channel. The insulating matrix and the flame-retardant shell material converge 7 cm before the outlet of the co-extrusion die head. A die core corresponding to the diameter of the copper core material is provided at the center of the inner channel of the co-extrusion die head. The extrusion temperature of the insulating matrix is 180 °C, and the extrusion temperature of the flame-retardant shell material is 190 °C. The screw compression ratios of the two extruders are both 3:1. The preparation method of the insulating matrix is as follows: 2.5 wt% of dicumyl peroxide cross-linking agent and the balance of low-density polyethylene are introduced into a kneader and kneaded at 115 °C and a rotation speed of 45 rpm for 16 min. After mixing evenly, it is extruded and coated on the conductor in a temperature range of 180 °C by a single-screw extruder to form an insulating layer with a thickness of 2.5 mm, and then enters a nitrogen-pressurized cross-linking pipeline, is heated to 350 °C at a rate of 6 °C / min and maintained for 10 min, and then cross-linked at a temperature of 370 °C and a pressure of 1.6 MPa for 46 min to obtain the insulating matrix.

[0054] Example 8: This example is basically the same as Example 1, except that the preparation method of the flame-retardant shell material is as follows: Weigh 1.5 wt% of modified nano-montmorillonite, 9 wt% of magnesium hydroxide, 7 wt% of aluminum hydroxide, 7 wt% of ethylene-vinyl acetate, 0.5 wt% of antioxidant, 0.2 wt% of lubricant, and the balance of low-density polyethylene; Mix the low-density polyethylene and ethylene-vinyl acetate at 500 rpm, then uniformly add the dried modified nano-montmorillonite and sieved magnesium hydroxide and aluminum hydroxide, and then add the antioxidant and lubricant. Raise the rotation speed to 3000 rpm and shear-mix at 120 °C for 18 min to obtain a flame-retardant material; Cool the flame-retardant material to 55 °C, remove impurities through a 100-mesh vibrating screen and an 8000-Gauss magnetic separator, and then put it into a twin-screw extruder to granulate at a temperature of 150 °C and a rotation speed of 120 rpm to obtain the flame-retardant shell material.

[0055] Example 9: This example is basically the same as Example 1, except that the preparation method of the flame-retardant shell material is as follows: Weigh 2.5 wt% of modified nano-montmorillonite, 11 wt% of magnesium hydroxide, 9 wt% of aluminum hydroxide, 9 wt% of ethylene-vinyl acetate, 0.7 wt% of antioxidant, 0.4 wt% of lubricant, and the balance of low-density polyethylene; Mix the low-density polyethylene and ethylene-vinyl acetate at 500 rpm, then uniformly add the dried modified nano-montmorillonite and sieved magnesium hydroxide and aluminum hydroxide, and then add the antioxidant and lubricant. Raise the rotation speed to 3000 rpm and shear-mix at 120 °C for 22 min to obtain a flame-retardant material; Cool the flame-retardant material to 65 °C, remove impurities through a 100-mesh vibrating screen and an 8000-Gauss magnetic separator, and then put it into a twin-screw extruder to granulate at a temperature of 175 °C and a rotation speed of 120 rpm to obtain the flame-retardant shell material.

[0056] Example 10: This example is basically the same as Example 1, except that the preparation method of the composite anti-corrosion shielding layer is as follows: Electrochemically polish an aluminum strip with a thickness of 0.1 mm to make its surface roughness reach Ra 0.8 μm, and then thermocompound it with a polyethylene film with a thickness of 0.05 mm through hot melt adhesive at a temperature of 180 °C and a pressure of 0.8 MPa to form an aluminum-plastic composite strip; Then spray an epoxy-polysiloxane anti-corrosion coating on the surface of the aluminum-plastic composite strip to obtain the composite anti-corrosion shielding layer; The electrolyte for the electrochemical polishing treatment is a mixed solution of phosphoric acid and sulfuric acid with a mass ratio of 3:1, the concentration of phosphoric acid is 85 wt%, the concentration of sulfuric acid is 98 wt%, the current density is 10 A / dm 2 , and the time is 4 min. The coating amount of the hot melt adhesive is 8 g / m 2 , and the raw material of the hot melt adhesive is ethylene-vinyl acetate copolymer.

[0057] Example 11: This example is basically the same as Example 1, except that the preparation method of the composite anti-corrosion shielding layer is as follows: An aluminum strip with a thickness of 0.2 mm is subjected to electrochemical polishing treatment to make its surface roughness reach Ra 0.8 μm, and then it is thermocompression bonded with a polyethylene film with a thickness of 0.06 mm through hot melt adhesive at a temperature of 180 °C and a pressure of 0.8 MPa to form an aluminum-plastic composite strip; then, an epoxy-polysiloxane anti-corrosion coating is sprayed on the surface of the aluminum-plastic composite strip to obtain the composite anti-corrosion shielding layer; the electrolyte for the electrochemical polishing treatment is a mixed solution with a mass ratio of phosphoric acid to sulfuric acid of 4:1, the concentration of phosphoric acid is 98 wt%, the concentration of sulfuric acid is 99 wt%, the current density is 10 A / dm 2 , and the time is 6 min. The coating amount of the hot melt adhesive is 8 g / m 2 , and the raw material of the hot melt adhesive is ethylene-vinyl acetate copolymer.

[0058] Example 12: This example is basically the same as Example 1, except that the method for spraying the epoxy-polysiloxane anti-corrosion coating on the surface of the aluminum-plastic composite strip is as follows: 25 wt% of polysiloxane prepolymer, 4 wt% of nano-zinc oxide, 4 wt% of KH-560 coupling agent and the balance of epoxy resin E-51 are mixed and stirred at a speed of 2000 rpm for 30 min to obtain the epoxy-polysiloxane anti-corrosion coating. The epoxy-polysiloxane anti-corrosion coating with a thickness of 0.1 mm is sprayed on the surface of the aluminum-plastic composite strip by an electrostatic spraying process, and then it is introduced into an infrared curing oven at 80 °C for curing for 40 min. After curing, the spraying of the epoxy-polysiloxane anti-corrosion coating is completed; the voltage of the electrostatic spraying process is 60 kV, and the spraying distance is 190 mm.

[0059] Example 13: This example is basically the same as Example 1, except that the method for spraying the epoxy-polysiloxane anti-corrosion coating on the surface of the aluminum-plastic composite strip is as follows: 35 wt% of polysiloxane prepolymer, 6 wt% of nano-zinc oxide, 6 wt% of KH-560 coupling agent and the balance of epoxy resin E-51 are mixed and stirred at a speed of 2000 rpm for 35 min to obtain the epoxy-polysiloxane anti-corrosion coating. The epoxy-polysiloxane anti-corrosion coating with a thickness of 0.15 mm is sprayed on the surface of the aluminum-plastic composite strip by an electrostatic spraying process, and then it is introduced into an infrared curing oven at 80 °C for curing for 40 min. After curing, the spraying of the epoxy-polysiloxane anti-corrosion coating is completed; the voltage of the electrostatic spraying process is 60 kV, and the spraying distance is 210 mm.

[0060] Example 14: This example is basically the same as Example 1, except that the preparation steps of the flame-retardant glass fiber tape layer are as follows: 200 g / m of the composite anti-corrosion shielding layer is used 2The halogen-free glass fiber tape is immersed in the flame retardant liquid at an immersion speed of 5 m / min for 25 s to ensure that the liquid absorption amount reaches 50%; then it is dried in a hot air circulation oven at 110 °C for 15 min, and after drying, it is wrapped around the outside of the composite anti-corrosion shielding layer in a double-layer overlapping wrapping manner to form a flame retardant glass fiber wrapping tape layer.

[0061] Example 15: This example is basically the same as Example 1, except that the preparation steps of the flame retardant glass fiber wrapping tape layer are as follows: Immerse the halogen-free glass fiber tape of 200 g / m of the composite anti-corrosion shielding layer in the flame retardant liquid at an immersion speed of 6 m / min for 35 s to ensure that the liquid absorption amount reaches 70%; then it is dried in a hot air circulation oven at 130 °C for 25 min, and after drying, it is wrapped around the outside of the composite anti-corrosion shielding layer in a double-layer overlapping wrapping manner to form a flame retardant glass fiber wrapping tape layer. 2 The halogen-free glass fiber tape is immersed in the flame retardant liquid at an immersion speed of 6 m / min for 35 s to ensure that the liquid absorption amount reaches 70%; then it is dried in a hot air circulation oven at 130 °C for 25 min, and after drying, it is wrapped around the outside of the composite anti-corrosion shielding layer in a double-layer overlapping wrapping manner to form a flame retardant glass fiber wrapping tape layer.

[0062] Example 16: This example is basically the same as Example 1, except that the flame retardant liquid is composed of a mixture of 35 wt% magnesium hydroxide, 3 wt% silane coupling agent, and the balance acrylate emulsion.

[0063] Example 17: This example is basically the same as Example 1, except that the flame retardant liquid is composed of a mixture of 55 wt% magnesium hydroxide, 5 wt% silane coupling agent, and the balance acrylate emulsion.

[0064] Control Example 1: Referring to Example 1, there is no flame retardant shell material in the XLPE insulating layer, and the epoxy-polysiloxane anti-corrosion coating is not sprayed on the surface of the aluminum-plastic composite tape.

[0065] Control Example 2: Referring to Example 1, there is no nano-montmorillonite in the flame retardant shell material.

[0066] Control Example 3: Referring to Example 1, the flame retardant liquid is composed of a mixture of 30 wt% magnesium hydroxide, 2 wt% silane coupling agent, and the balance acrylate emulsion.

[0067] In order to explore the cable performance of the examples and control examples, the main materials were determined according to the experimental formula and samples were obtained for testing. The results are shown in Table 1 below and Figures 1-5 as follows. The specific exploration is as follows:

[0068]

[0069]

[0070] 1. Explore the influence of parameter changes in the thickness of each layer on the cable performance:

[0071] As shown in Table 1 and Figures 1-5As shown, in terms of the insulation layer thickness, Example 3 uses an XLPE insulation layer with a thickness of 5.5 mm, and its partial discharge amount is controlled below 5 pC, which is better than 4 mm in Example 1 and 4.5 mm in Example 2, indicating that increasing the insulation layer thickness can effectively reduce the risk of electric field concentration. However, the cable flexibility still needs to be weighed; when the insulation layer is too thin, such as 1.5 mm in Example 6, the partial discharge amount rises to 8 pC, verifying the negative impact of insufficient thickness on the insulation strength; in the optimization of the thickness of the composite anti-corrosion shielding layer, Example 11 uses an aluminum strip with a thickness of 0.2 mm and an epoxy coating with a thickness of 0.12 mm, and the total thickness of the aluminum-plastic composite strip is 0.38 mm, and the corrosion area is as low as 1.2%, which is significantly better than 0.1 mm aluminum strip and 0.12 mm coating in Example 10, and the corrosion area of the latter reaches 4.3%. The increase in the aluminum strip thickness and the coating compactness directly enhances the anti-corrosion barrier effect; in terms of the flame-retardant fiberglass tape layer, Example 3 has a lower smoke density, which is better than Example 1 and Example 2. Appropriately increasing the thickness of the flame-retardant fiberglass tape layer can improve the flame-retardant efficiency.

[0072] 2. Explore the influence of changes in the process parameters of each layer on the cable performance:

[0073] As shown in Table 1 and Figures 1-5 As shown, the influence of process parameter adjustment on the performance is also significant; in the annealing process of the copper core material, the partial discharge amount in Example 1 is controlled below 3 pC, and the grain refinement is uniform; while in Example 4, due to the annealing temperature dropping to 440 °C and the cooling rate being too slow, the partial discharge amount rises to 4 pC, showing the importance of precise control of temperature and cooling rate for the conductor structure integrity; in the cross-linking process of the XLPE insulation layer, Example 7 cross-links at a high temperature of 370 °C and a high pressure of 1.6 MPa, and the limiting oxygen index is increased to 37%, which is better than the cross-linking result of 350 °C in Example 6, proving that high temperature and high pressure can optimize the dispersibility of the flame retardant; in the preparation of the flame-retardant shell material, the hydroxide content in Example 9 is increased to 11% magnesium hydroxide and 9% aluminum hydroxide, and the limiting oxygen index reaches 37.1%, which is significantly improved compared with 7% magnesium hydroxide and 7% aluminum hydroxide in Example 8, indicating the synergistic effect of high proportion of flame retardant and nano-montmorillonite; in the electrochemical polishing and coating process of the composite anti-corrosion shielding layer, Example 13 uses 35 wt% polysiloxane prepolymer and 6 wt% nano-zinc oxide, and the corrosion area is as low as 1.2%, and the smoke density is only 37, which is better than the combination of 25 wt% prepolymer and 4 wt% zinc oxide in Example 12.

[0074] Example 17 achieved a limiting oxygen index of 38.6% and a smoke density of 32 with a 55% magnesium hydroxide flame retardant liquid, becoming the optimal sample for flame retardancy and smoke suppression performance; Example 13 became the best anti-corrosion performance solution with a 1.2% corrosion area by optimizing the coating composition and polishing process; Example 1, with a balanced insulation layer thickness, flame retardant ratio, and annealing process, had a limiting oxygen index of 35.2%, a corrosion area of 2.1%, and a partial discharge of 3 pC, making it the first choice for comprehensive performance; in contrast, Example 16 had a limiting oxygen index as low as 30.5% and a smoke density as high as 75, and its performance was close to that of Comparative Example 3, verifying the necessity of a high loading of flame retardant; Comparative Example 1, due to the complete absence of a flame retardant shell material and anti-corrosion coating, had a limiting oxygen index of only 22%, a corrosion area of 38.6%, and a partial discharge exceeding 20 pC, fully demonstrating the core role of the composite flame retardant structure, aluminum-plastic shielding layer, and high loading of flame retardant liquid in the technical solution of the present invention; Comparative Example 2 lacked nanoclay in the flame retardant shell material, with an LOI of only 25.3% and a corrosion area of 15.2%, further demonstrating the key role of nanomaterials in interfacial bonding and flame retardancy efficiency; although Comparative Example 3 had a flame retardant liquid containing 30% magnesium hydroxide and retained the basic anti-corrosion layer, its LOI was only 28.7%, the corrosion area was 9.7%, and the smoke density was 68, and its performance was still significantly lower than that of the example group.

Claims

1. A medium-voltage cross-linked polyethylene insulated power cable with high flame retardancy and corrosion resistance, characterized in that, It includes a copper core material, an XLPE insulation layer arranged outside the copper core material, a composite anti-corrosion shielding layer arranged outside the XLPE insulation layer, and a flame-retardant fiberglass tape layer arranged outside the composite anti-corrosion shielding layer; the thickness of the XLPE insulation layer is 4.5 - 5.5 mm, the thickness of the composite anti-corrosion shielding layer is 0.4 - 0.6 mm, and the single-layer thickness of the flame-retardant fiberglass tape layer is 0.1 - 0.4 mm.

2. A highly flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable according to claim 1, characterized in that, The preparation method of the copper core material is as follows: Annealed copper single wires with a diameter of 0.15 - 0.25 mm are used and stranded in five layers. The number of strands from the center to the outside is successively: 1 strand, 6 strands, 12 strands, 18 strands, 24 strands. The stranding pitches from the center to the outside are successively 10 times, 12 times, 14 times, 16 times, 18 times the conductor diameter. The stranding direction is alternately rightward and leftward. After stranding, a conductor is obtained. Then the conductor is introduced into an annealing furnace under inert gas protection for treatment. The annealing temperature is 440 - 460 °C, the heat preservation time is 1.5 - 2.5 h, and it is cooled to room temperature at a cooling rate of 1 - 5 °C / min to obtain the copper core material.

3. A high flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable according to claim 1, characterized in that, The XLPE insulation layer is composed of an insulation matrix and a flame-retardant shell material on the surface of the insulation matrix; the preparation method of the XLPE insulation layer is as follows: The insulation matrix and the flame-retardant shell material are conveyed to a co-extrusion die head by two extruders for synchronous extrusion. The inner channel of the co-extrusion die head conducts the insulation matrix, and the outer channel conducts the flame-retardant shell material. The insulation matrix and the flame-retardant shell material converge 5 - 7 cm before the outlet of the co-extrusion die head. A die core corresponding to the diameter of the copper core material is arranged at the center of the inner channel of the co-extrusion die head. The extrusion temperature of the insulation matrix is 160 - 180 °C, the extrusion temperature of the flame-retardant shell material is 170 - 190 °C, and the screw compression ratios of the two extruders are both 3:

1.

4. A highly flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable according to claim 3, characterized in that, The preparation method of the insulation matrix is as follows: 1.5 - 2.5 wt% of dicumyl peroxide cross-linking agent and the balance of low-density polyethylene are introduced into a mixer and kneaded at 105 - 115 °C and a rotation speed of 35 - 45 rpm for 14 - 16 min. After being mixed evenly, it is extruded and coated on the conductor by a single-screw extruder in the temperature range of 160 - 180 °C to form an insulation layer with a thickness of 1.5 - 2.5 mm. Then it enters a nitrogen-pressurized cross-linking pipeline, is heated to 250 - 350 °C at a rate of 4 - 6 °C / min and maintained for 10 min, and then cross-linked at a temperature of 350 - 370 °C and a pressure of 1.4 - 1.6 MPa for 44 - 46 min to obtain the insulation matrix.

5. A highly flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable according to claim 3, characterized in that, The preparation method of the flame-retardant shell material is as follows: Weigh 1.5-2.5 wt% of modified nano-montmorillonite, 9-11 wt% of magnesium hydroxide, 7-9 wt% of aluminum hydroxide, 7-9 wt% of ethylene-vinyl acetate, 0.5-0.7 wt% of antioxidant, 0.2-0.4 wt% of lubricant and the balance of low-density polyethylene; Mix the low-density polyethylene and ethylene-vinyl acetate at 500 rpm, then uniformly add the dried modified nano-montmorillonite, sieved magnesium hydroxide and aluminum hydroxide, and then add the antioxidant and lubricant. Raise the rotation speed to 3000 rpm and shear-mix at 120 °C for 18-22 min to obtain a flame-retardant material; Cool the flame-retardant material to 55-65 °C, remove impurities through a 100-mesh vibrating screen and an 8000-Gauss magnetic separator, and then put it into a twin-screw extruder to granulate at a temperature of 150-175 °C and a rotation speed of 120 rpm to obtain the flame-retardant shell material.

6. A highly flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable according to claim 1, wherein, The preparation method of the composite anti-corrosion shielding layer is as follows: Electrochemically polish an aluminum strip with a thickness of 0.1-0.2 mm to make its surface roughness reach Ra 0.8 μm, and then thermocompound it with a polyethylene film with a thickness of 0.05-0.06 mm through hot melt adhesive at a temperature of 180 °C and a pressure of 0.8 MPa to form an aluminum-plastic composite strip; Then spray an epoxy-polyorganosiloxane anti-corrosion coating on the surface of the aluminum-plastic composite strip to obtain the composite anti-corrosion shielding layer.

7. A highly flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable according to claim 6, characterized in that, The electrolyte for the electrochemically polishing treatment is a mixed solution with a mass ratio of phosphoric acid to sulfuric acid of 3-4:1, the concentration of phosphoric acid is greater than or equal to 85 wt%, the concentration of sulfuric acid is greater than or equal to 98 wt%, the current density is 10 A / dm 2 , the time is 4-6 min, the coating amount of the hot melt adhesive is 8 g / m 2 , and the raw material of the hot melt adhesive is ethylene-vinyl acetate copolymer.

8. A highly flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable according to claim 6, characterized in that, The method of spraying the epoxy-polyorganosiloxane anti-corrosion coating on the surface of the aluminum-plastic composite strip is as follows: Mix 25-35 wt% of polyorganosiloxane prepolymer, 4-6 wt% of nano-zinc oxide, 4-6 wt% of KH-560 coupling agent and the balance of epoxy resin E-51, and stir at a rotation speed of 2000 rpm for 30-35 min to obtain the epoxy-polyorganosiloxane anti-corrosion coating. Spray the epoxy-polyorganosiloxane anti-corrosion coating with a thickness of 0.1-0.15 mm on the surface of the aluminum-plastic composite strip by electrostatic spraying process, and then introduce it into an infrared curing oven at 80 °C to cure for 40 min. After curing, the spraying of the epoxy-polyorganosiloxane anti-corrosion coating is completed; The voltage of the electrostatic spraying process is 60 kV, and the spraying distance is 190-210 mm.

9. A highly flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable according to claim 1, characterized in that, The preparation steps of the flame-retardant glass fiber tape layer are as follows: Immerse the halogen-free glass fiber tape accounting for 200 g / m of the composite anti-corrosion shielding layer 2 in the flame-retardant liquid at an impregnation speed of 5 - 6 m / min for 25 - 35 s to ensure that the liquid absorption amount reaches 50 - 70%; then dry it in a hot air circulation oven at 110 - 130 °C for 15 - 25 min, and after drying, wrap it around the outside of the composite anti-corrosion shielding layer in a double-layer overlapping wrapping manner to form a flame-retardant glass fiber tape layer.

10. A highly flame-retardant and corrosion-resistant medium-voltage cross-linked polyethylene insulated power cable according to claim 9, characterized in that, The flame-retardant liquid is composed of 35-55 wt% of magnesium hydroxide, 3-5 wt% of silane coupling agent and the balance of acrylate emulsion.

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