Corrosion-resistant power cable and preparation method thereof

Abstract

The invention relates to the technical field of special cable manufacturing, in particular to a corrosion-resistant power cable and a preparation method thereof.The corrosion-resistant power cable is composed of a copper conductor, a conductor shielding layer, a crosslinked polyethylene insulating layer, an insulating shielding layer, a metal shielding layer, a lining layer, an armor layer and an outer sheath; the surface of the copper conductor is plated with a nickel-phosphorus alloy, and the outer sheath contains low-density polyethylene, an ethylene-vinyl acetate copolymer, nano zinc oxide, a rare earth cerium compound and a silane coupling agent; the insulating layer is prepared through silane crosslinking, the armor layer is a galvanized steel strip or a steel wire, the metal shielding layer is wrapped by a copper strip or a copper wire, and the lining layer is made of polyethylene or a halogen-free material. The outer sheath is high in corrosion resistance, the conductors are resistant to oxidation, the insulation eccentricity is low, the stability is improved through the shielding and armoring structure, the insulation performance is optimized through the cross-linking technology, the preparation technology is suitable for industrial production, the qualified rate of finished products is high, and cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of special cable manufacturing, in particular to a corrosion-resistant power cable and a preparation method thereof. Background Art

[0002] In the power transmission sector, extruded insulated power cables with rated voltages from 0.6 / 1kV to 26 / 35kV are widely used, but existing technologies have significant shortcomings. Traditional cable sheaths, often made of polyvinyl chloride (PVC) or polyethylene (PE), are susceptible to cracking and aging when exposed to corrosive environments such as salt spray, acids, and alkalis. This can lead to insulation degradation and even electrical leakage. Furthermore, the copper conductor surface is susceptible to oxidation in humid environments, affecting its conductivity. Existing coating processes lack sufficient adhesion, making them incapable of long-term conductor protection.

[0003] The cable manufacturing process also faces challenges. In the conventional three-layer co-extrusion process, the insulation layer's eccentricity is poorly controlled, which can easily cause partial discharge, especially in high-voltage cables. The metal shielding layer's overlap is unstable, resulting in uneven electromagnetic shielding. The armor layer's gap ratio is too large, making it ineffective against external mechanical damage. Furthermore, the warm water cross-linking time and temperature control lack systematic optimization, resulting in unstable thermal expansion properties of the insulation layer, which affects the cable's service life.

[0004] Existing corrosion-resistant cable technologies often focus on a single protective method, such as improving the outer sheath material alone, without integrating multiple dimensions such as conductor plating, shielding structure, and insulation process into the design. This makes it difficult to meet the demands of complex operating conditions. Furthermore, mold selection and parameter control in the manufacturing process rely heavily on experience and lack standardized procedures, resulting in poor product consistency and low industrial production efficiency. Summary of the Invention

[0005] (1) Technical problems solved In view of the deficiencies in the prior art, the present invention provides a corrosion-resistant power cable and a preparation method thereof.

[0006] (2) Technical solution A corrosion-resistant power cable comprises, from the inside out, a copper conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, a metal shielding layer, an inner lining layer, an armor layer, and an outer sheath; the outer sheath is composed of the following components in parts by weight: 60-70 parts of low-density polyethylene, 15-20 parts of ethylene-vinyl acetate copolymer, 5-8 parts of nano zinc oxide, 3-5 parts of a rare earth cerium compound, and 2-4 parts of a silane coupling agent.

[0007] Preferably, the copper conductor is wrapped with 1-2 layers of mica tape, the wrapping direction is right, the overlap rate is 10-15%, 6mm² and below use Class 1 solid conductor, 10-35mm² use Class 2 non-compacted structure, and 50mm² and above use Class 2 compacted structure.

[0008] Preferably, the conductor shielding layer is an extruded semi-conductive layer with a resistivity of ≤800Ω·m and a thickness of 0.8-1.0mm. The nominal thickness of the insulating shielding layer is 0.8-1.0mm, and the thickness at the thinnest point is not less than 0.7mm.

[0009] Preferably, the metal shielding layer is a double-layer copper tape wrapping, the inner copper tape has a thickness of 0.1-0.15 mm, the outer copper tape has a thickness of 0.15-0.2 mm, the overlap rate is 15-20%, and the copper tape is made of TU1 type soft copper tape.

[0010] Preferably, the armor layer is a double-layer galvanized steel strip or round steel wire armor; when using steel strip, it is wrapped with a left-hand gap, and the gap rate is ≤50%; when using steel wire, the steel wire diameter is 0.8-1.2mm, the armor direction is left-hand, and the pitch-to-diameter ratio is 9-12.

[0011] Preferably, the eccentricity of the cross-linked polyethylene insulation layer is not greater than 8%, the thickness at the thinnest point is not less than 90%-0.1mm of the nominal thickness, the thickness of the outer sheath at the thinnest point is not less than 80%-0.2mm of the nominal thickness, and it needs to pass the 6t (kV) power frequency spark test.

[0012] Preferably, the method for preparing the corrosion-resistant power cable comprises the following steps: S1 conductor treatment: The copper rod is drawn and annealed to form a compact stranded conductor with a right-hand lay and a pitch of 10-20 times the outer diameter of the conductor. The surface is plated with a nickel-phosphorus alloy layer with a thickness of 0.1-0.3 μm. S2 three-layer co-extrusion: Using three-layer co-extrusion equipment, the conductor shielding layer, cross-linked polyethylene insulation layer, and insulation shielding layer are extruded in sequence. The extrusion temperature is 160-180°C, the vulcanization pressure is 1.5-2MPa, the line speed is 20-30m / min, and the insulation eccentricity is controlled within 8%; S3 mica tape wrapping: Wrap the mica tape around the conductor in the right direction with an overlap rate of 10-15%, and then perform warm water cross-linking at a water temperature of 70-90°C for 12-24 hours; S4 armor and sheath extrusion: The armor layer is wrapped around the inner lining layer, the steel tape gap ratio is ≤50% or the steel wire pitch ratio is 9-12; the outer sheath is extruded by a tube extrusion die, the die core diameter d=d1+(1-2)mm, the die sleeve diameter D=d+2(δ+t)+(2-4)mm, where d1 is the outer diameter before extrusion, δ is the die core wall thickness, and t is the sheath thickness.

[0013] Preferably, the DC resistance of the stranded conductor in S1 complies with the GB / T 3956-2008 standard, and the plating solution temperature during nickel-phosphorus alloy plating is 50-60° C., the pH value is 4.5-5.5, and the plating time is 10-15 min.

[0014] Preferably, the S4 outer sheath raw material premixing process is: low-density polyethylene, ethylene-vinyl acetate copolymer, nano zinc oxide, rare earth cerium compound, and silane coupling agent are mixed at a speed of 300-500 r / min for 10-15 minutes, and then granulated by twin-screw extrusion.

[0015] Preferably, the finished cable needs to pass the 1000h immersion test in 3.5% sodium chloride solution, with the outer sheath weight loss rate ≤5%, and pass the JB / T 10696.9 ant nest method anti-termite test, with a corrosion level of Level 1.

[0016] (3) Beneficial technical effects Compared with the existing technology, the beneficial effects of the present invention are: 1. The outer sheath is infused with rare earth cerium compounds and nano-zinc oxide to form a corrosion-resistant network structure. After immersion in a 3.5% sodium chloride solution for 1000 hours, the weight loss rate is reduced, effectively resisting salt spray, acid and alkali corrosion. The copper conductor is plated with a nickel-phosphorus alloy layer, which strengthens the bonding strength, improves oxidation resistance, and significantly enhances conductive stability.

[0017] 2. Optimized manufacturing processes achieve high-precision control. Three-layer co-extrusion technology, combined with customized molds, reduces insulation eccentricity to below 8% in cables 10kV and above, achieving partial discharge ≤5pC, meeting high-voltage operating requirements. The metal shield's double-layer copper tape wrapping achieves a 15%-20% overlap, ensuring uniform and stable electromagnetic shielding. The armor interstitial ratio is ≤50%, enhancing mechanical strength.

[0018] 3. The warm water cross-linking process precisely controls time and temperature according to voltage level. After 72 hours of cross-linking, the insulation elongation under load for 26 / 35kV cables is ≤125%, and the permanent elongation after cooling is ≤10%, ensuring the long-term stability of the insulation layer. This highly standardized preparation method allows for quantitative control of mold parameters and extrusion temperature, making it suitable for large-scale production. This improves the yield of finished products and reduces production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of a method for preparing a corrosion-resistant power cable disclosed in the present invention; Figure 2 is a line chart comparing the weight loss rates of the embodiment and the comparative example after immersion in 3.5% NaCl for 1000 hours; Figure 3 1. It is a bar chart comparing the insulation resistance retention rates of the embodiment and the comparative example; Figure 4 It is a bar chart comparing the insulation process parameters of the embodiment and the comparative example. DETAILED DESCRIPTION

[0020] according to Figures 1 to 4 , the specific implementation methods of the present invention are as follows: Overview of cable structure Copper conductor: 6mm² and below is Class 1 solid conductor, 10-35mm² is Class 2 non-compact structure, 50mm² and above is Class 2 compact structure, with surface plating of 0.1-0.3μm nickel-phosphorus alloy (nickel 65-75%, phosphorus 25-35%).

[0021] Conductor shielding layer: extruded semi-conductive layer (ethylene-vinyl acetate copolymer: carbon black = 9:1), thickness 0.8-1.0mm, resistivity ≤ 800Ω・m, 500mm² and above requires composite semi-conductive tape wrapping (thickness 0.14mm, overlap rate ≥5%).

[0022] Cross-linked polyethylene insulation layer: prepared by silane cross-linking reaction, nominal thickness 1.2-1.4mm for 0.6 / 1kV, 4.5mm for 10kV, 10.1mm for 26 / 35kV, thinnest point ≥ 90% of nominal value - 0.1mm, eccentricity ≤15% (0.6 / 1kV) or ≤8% (10kV and above).

[0023] Insulation shielding layer: extruded strippable semi-conductive layer, thickness 0.8-1.0mm, thinnest point ≥0.7mm.

[0024] Mica tape wrapping: Wrap 1-2 layers in the right direction with an overlap rate of 10-15%.

[0025] Metal shielding layer: copper tape wrapping (double layer, inner layer 0.1-0.15mm, outer layer 0.15-0.2mm, overlap rate 15-20%) or copper wire sparse winding (70 pieces, diameter 0.8mm, pitch diameter ratio 11-13, gap ≤4mm).

[0026] Inner lining: low-density polyethylene or halogen-free low-smoke polyolefin, thinnest point ≥ 80% of nominal value - 0.2mm.

[0027] Armor layer: double-layer galvanized steel tape (gap ratio ≤ 50%, thickness 0.5-0.8mm) or round steel wire (diameter 0.8-1.2mm, pitch diameter ratio 9-12), non-magnetic metal tape / wire for single-core cable.

[0028] Outer sheath: 60-70 parts of low-density polyethylene, 15-20 parts of ethylene-vinyl acetate copolymer, 5-8 parts of nano-zinc oxide, 3-5 parts of rare earth cerium compound, 2-4 parts of silane coupling agent, the thinnest point ≥ 80% of the nominal value -0.2mm, must pass the 6t (kV) spark test (t is the nominal thickness).

[0029] Example 1: 0.6 / 1kV 3×50mm² corrosion-resistant power cable 1. Structural composition Copper conductor: 7 copper wires with a diameter of 3.01 mm (Class 2 non-compacted), an outer diameter of 8.2 mm, plated with 0.2 μm nickel-phosphorus alloy (70% nickel, 30% phosphorus).

[0030] Conductor shield: thickness 0.8mm, resistivity 750Ω·m.

[0031] Cross-linked polyethylene insulation layer: nominal thickness 1.4mm, thinnest point 1.16mm (1.4×90%-0.1=1.16), eccentricity 12%.

[0032] Mica tape: 1 layer, overlap rate 12%.

[0033] Metal shielding layer: single layer of copper tape (thickness 0.1mm), overlap rate 15%.

[0034] Inner lining: low-density polyethylene, thickness 1.2mm, thinnest point 0.94mm (1.2×80%-0.2=0.76, measured 0.94).

[0035] Armor layer: double-layer galvanized steel strip (thickness 0.5mm), gap ratio 45%.

[0036] Outer sheath: 65 parts of low-density polyethylene, 18 parts of ethylene-vinyl acetate copolymer, 6 parts of nano-zinc oxide, 4 parts of rare earth cerium compound, 3 parts of silane coupling agent, thickness 1.8mm, thinnest point 1.24mm.

[0037] 2. Preparation Steps S1 conductor treatment: Copper rods were drawn to 3.01 mm, annealed at 350°C for 2 h, and twisted into 7 strands with a pitch of 107-123 mm. Nickel-phosphorus alloy plating was performed at a bath temperature of 55°C, pH 5.0, and electroplating for 12 min.

[0038] S2 three-layer co-extrusion: the extrusion temperatures of conductor shielding material, insulation material and insulation shielding material are 165℃, 175℃ and 170℃ respectively, the vulcanization pressure is 1.5MPa, the line speed is 20m / min, and warm water cross-linking (water temperature 70℃, 24h).

[0039] S3 mica tape wrapping: 1 layer in right direction, overlap rate 12%, spark test voltage 8.4kV (6×1.4kV).

[0040] S4 armor and sheath extrusion: The steel strip is wrapped in the left direction, and the gap rate is ≤50%. The outer sheath adopts a tube extrusion die (die core diameter = armor rear outer diameter + 3mm, die sleeve diameter = die core diameter + 2*(0.5+1.8)+3mm), extrusion temperature is 175℃, and printing spacing is 400mm.

[0041] Example 2: 10kV 3×150mm² corrosion-resistant power cable 1. Structural composition Copper conductor: 30 2.60 mm diameter copper wires (Class 2 compressed), 14.4 mm outer diameter, plated with 0.25 μm nickel-phosphorus alloy (68% nickel, 32% phosphorus).

[0042] Conductor shielding layer: thickness 0.8mm, added 0.5 parts of nanographene, resistivity 700Ω・m.

[0043] Cross-linked polyethylene insulation layer: nominal thickness 4.5mm, thinnest point 4.05mm, eccentricity 7%.

[0044] Mica tape: 1 layer, overlap rate 15%.

[0045] Metal shielding layer: double-layer copper tape (inner layer 0.1mm, outer layer 0.15mm), overlapping rate 20%.

[0046] Inner lining: Halogen-free low-smoke polyolefin, thickness 1.8mm, thinnest point 1.42mm (1.8×80%-0.2=1.24, measured 1.42).

[0047] Armor layer: double-layer galvanized steel strip (thickness 0.5mm), gap ratio 45%.

[0048] Outer sheath: 70 parts of low-density polyethylene, 15 parts of ethylene-vinyl acetate copolymer, 8 parts of nano-zinc oxide, 3 parts of rare earth cerium compound, 4 parts of silane coupling agent, thickness 2.8mm, thinnest point 2.04mm.

[0049] 2. Preparation Steps S1 conductor treatment: twisted into 30 strands, pitch 140-157mm, bath temperature 60°C, pH = 4.8, electroplating for 15 minutes.

[0050] S2 three-layer co-extrusion: extrusion temperature 170℃, 180℃, 175℃, vulcanization pressure 2.0MPa, line speed 25m / min, warm water cross-linking (water temperature 85℃, 24h).

[0051] S4 armor and sheath extrusion: After the steel tape is wrapped, the outer sheath core diameter = the outer diameter of the armor + 7mm, the sheath diameter = the core diameter + 2*(0.5+2.8)+5mm, the extrusion temperature is 185℃, and the spark test voltage is 16.8kV (6×2.8kV).

[0052] Example 3: 26 / 35kV 1×630mm² corrosion-resistant power cable 1. Structural composition Copper conductor: 60 copper wires with a diameter of 3.80 mm (Type 2 compressed), an outer diameter of 30.0 mm, and plated with 0.3 μm nickel-phosphorus alloy (75% nickel, 25% phosphorus).

[0053] Conductor shielding layer: Semi-conductive tape (0.14mm, right-hand wrapping, overlap rate 5%) + extruded semi-conductive layer composite structure.

[0054] Cross-linked polyethylene insulation layer: nominal thickness 10.1mm, thinnest point 9.45mm, eccentricity 8%.

[0055] Mica tape: 2 layers, overlap rate 15%.

[0056] Metal shielding layer: sparsely wound copper wires (70 wires, 0.8 mm diameter, pitch ratio 12, gap ≤ 4 mm) + reverse-tied copper tape (0.1 mm thickness, right-hand wrapping).

[0057] Lining layer: Halogen-free low-smoke polyolefin, thickness 2.4mm, thinnest point 1.72mm (2.4×80%-0.2=1.72).

[0058] Armor layer: non-magnetic aluminum wire (diameter 1.2mm), pitch-to-diameter ratio 9, left-hand winding, total gap ≤1.2mm.

[0059] Outer sheath: 60 parts of low-density polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 5 parts of nano-zinc oxide, 5 parts of rare earth cerium compound, 2 parts of silane coupling agent, thickness 4.4mm, thinnest point 3.32mm.

[0060] 2. Preparation Steps S1 conductor treatment: Copper rods were drawn to 3.80 mm, annealed at 400°C for 3 h, and twisted into 60 strands with a pitch of 270-291 mm. Nickel-phosphorus alloy plating was performed at a bath temperature of 60°C, pH 5.5, and electroplating for 15 min.

[0061] S2 three-layer co-extrusion: 35kV-grade cross-linkable material is used. The extrusion temperatures of conductor shield, insulation, and insulation shield are 180°C, 190°C, and 185°C respectively. The vulcanization pressure is 2.0MPa, the line speed is 15m / min, and the insulation core is placed for 72 hours to eliminate stress.

[0062] S3 mica tape wrapping: 2 layers in right direction, overlap rate 15%, partial discharge test (voltage 2U0, sensitivity ≤5pC).

[0063] S4 armor and sheath extrusion: aluminum wire wrapped in the left direction, pitch diameter ratio 9; outer sheath core diameter = armor outer diameter + 9mm, sleeve diameter = core diameter + 2*(0.6+4.4)+6mm, extrusion temperature 190℃, spark test voltage 26.4kV (6×4.4kV), printing spacing 300mm.

[0064] Comparative example: Traditional PVC sheathed cable (0.6 / 1kV 3×50mm²) 1. Differences in structure and process Outer sheath: HI-90 type polyvinyl chloride material, without nano zinc oxide and rare earth cerium compounds, thickness 1.8mm, thinnest point 1.24mm (1.8×80%-0.2=1.24).

[0065] Preparation process: Omit premixing of outer sheath raw materials, directly extrude, no anti-corrosion treatment, the armor layer is a single layer of steel belt.

[0066] The corrosion resistance of the embodiment and the comparative example is compared in the following table: Table 1 The outer sheath weight loss rate of Examples 1-3 is reduced by 73%-76% compared with the control example, and the insulation resistance retention rate is increased by 30-31 percentage points, which proves that the composite addition of rare earth cerium compound and nano zinc oxide significantly enhances the corrosion resistance.

[0067] The insulation process parameters of the embodiment and the comparative example are compared in the following table: Table 2 The insulation eccentricity of Examples 2-3 is reduced by 41%-58% compared with the 0.6 / 1kV products. The 26 / 35kV products ensure insulation uniformity under high voltage by extending the crosslinking time to 72h. The spark test voltage increases linearly with increasing thickness.

[0068] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A corrosion-resistant power cable, characterized in that: From the inside to the outside, it includes a copper conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, a metal shielding layer, an inner lining layer, an armor layer, and an outer sheath; the outer sheath is composed of the following components in parts by weight: 60-70 parts of low-density polyethylene, 15-20 parts of ethylene-vinyl acetate copolymer, 5-8 parts of nano zinc oxide, 3-5 parts of rare earth cerium compound, and 2-4 parts of silane coupling agent.

2. The corrosion-resistant power cable according to claim 1, characterized in that: The copper conductor is wrapped with 1-2 layers of mica tape in the right direction with an overlap rate of 10-15%. 6mm² and below adopts Class 1 solid conductor, 10-35mm² adopts Class 2 non-compact structure, and 50mm² and above adopts Class 2 compact structure.

3. The corrosion-resistant power cable according to claim 2, characterized in that: The conductor shielding layer is an extruded semi-conductive layer with a resistivity of ≤800Ω·m and a thickness of 0.8-1.0mm. The nominal thickness of the insulating shielding layer is 0.8-1.0mm, and the thickness at the thinnest point is not less than 0.7mm.

4. The corrosion-resistant power cable according to claim 3, characterized in that: The metal shielding layer is wrapped with double-layer copper tape, the inner copper tape has a thickness of 0.1-0.15mm, the outer copper tape has a thickness of 0.15-0.2mm, the overlap rate is 15-20%, and the copper tape is made of TU1 soft copper tape.

5. The corrosion-resistant power cable according to claim 4, characterized in that: The armor layer is a double-layer galvanized steel strip or round steel wire armor; when steel strip is used, it is wrapped with a left-hand gap and the gap rate is ≤50%; when steel wire is used, the steel wire diameter is 0.8-1.2mm, the armor direction is left-hand, and the pitch-diameter ratio is 9-12.

6. The corrosion-resistant power cable according to claim 5, characterized in that: The eccentricity of the cross-linked polyethylene insulation layer is not greater than 8%, the thickness at the thinnest point is not less than 90%-0.1mm of the nominal thickness, the thickness of the outer sheath at the thinnest point is not less than 80%-0.2mm of the nominal thickness, and it must pass a 6t (kV) power frequency spark test.

7. The method for preparing a corrosion-resistant power cable according to claim 6, characterized in that: The following steps are involved: S1 conductor treatment: The copper rod is drawn and annealed to form a compact stranded conductor with a right-hand lay and a pitch of 10-20 times the outer diameter of the conductor. The surface is plated with a nickel-phosphorus alloy layer with a thickness of 0.1-0.3 μm. S2 three-layer co-extrusion: Using three-layer co-extrusion equipment, the conductor shielding layer, cross-linked polyethylene insulation layer, and insulation shielding layer are extruded in sequence. The extrusion temperature is 160-180°C, the vulcanization pressure is 1.5-2MPa, the line speed is 20-30m / min, and the insulation eccentricity is controlled within 8%; S3 mica tape wrapping: Wrap the mica tape around the conductor in the right direction with an overlap rate of 10-15%, and then perform warm water cross-linking at a water temperature of 70-90°C for 12-24 hours; S4 armor and sheath extrusion: The armor layer is wrapped around the inner lining layer, the steel tape gap ratio is ≤50% or the steel wire pitch ratio is 9-12; the outer sheath is extruded by a tube extrusion die, the die core diameter d=d1+(1-2)mm, the die sleeve diameter D=d+2(δ+t)+(2-4)mm, where d1 is the outer diameter before extrusion, δ is the die core wall thickness, and t is the sheath thickness.

8. The method for preparing a corrosion-resistant power cable according to claim 7, characterized in that: The DC resistance of the stranded conductor in S1 complies with the GB / T 3956-2008 standard. When plating nickel-phosphorus alloy, the plating bath temperature is 50-60° C., the pH value is 4.5-5.5, and the plating time is 10-15 minutes.

9. The method for preparing a corrosion-resistant power cable according to claim 7, characterized in that: The S4 inner and outer sheath raw material premixing process is: low-density polyethylene, ethylene-vinyl acetate copolymer, nano zinc oxide, rare earth cerium compound, and silane coupling agent are mixed at a speed of 300-500 r / min for 10-15 minutes, and then granulated by twin-screw extrusion.

10. The method for preparing a corrosion-resistant power cable according to claim 7, characterized in that: The finished cable must pass a 1000-hour immersion test in 3.5% sodium chloride solution, with the outer sheath weight loss rate ≤5%, and pass the JB / T 10696.9 ant nest method anti-ant test, with a corrosion level of Level 1.

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