1. Product-Specific Information
1.1 Specification Parameters
The 2-core
XLPE Insulated PVC sheathed aluminum core waterproof
Underground Power Cable (1000V) is a specialized low-voltage power
Transmission Cable designed for underground laying scenarios, with precise and comprehensive specification parameters that ensure its stable performance, waterproof reliability, and adaptability to complex underground environments.
1.1.1 Voltage Rating and Electrical Performance
The cable’s rated voltage is 1000V (Um = 1.2kV), which aligns with the low-voltage power distribution system standards (GB/T 12706.1-2020 and IEC 60502-1). This voltage level is suitable for most low-voltage applications, where the maximum operating voltage does not exceed 1kV. To verify its electrical safety, the cable undergoes rigorous voltage withstand tests during production: a 3kV AC voltage is applied between the conductor and the grounded sheath for 5 minutes, with no breakdown or leakage current exceeding 10μA allowed. This test ensures the cable can withstand transient overvoltages caused by grid switching or lightning strikes in underground environments.
The insulation resistance of the cable is another key electrical parameter. Measured with a 2500V megohmmeter at 20℃, the insulation resistance between the conductor and sheath is not less than 1000MΩ·km. Even after 24 hours of immersion in water (20±5℃), the insulation resistance remains above 500MΩ·km, confirming its excellent waterproof insulation performance. The dielectric loss of the XLPE insulation layer is extremely low—at 50Hz, the dielectric loss tangent (tanδ) is ≤0.0005—minimizing energy loss during power transmission and improving the cable’s overall energy efficiency.
1.1.2 Conductor Specifications
The cable uses high-purity aluminum (Al) conductors with a purity of ≥99.7%, which meets the requirements of GB/T 3954-2014 (Aluminum and aluminum alloys for electrical purposes). The conductor adopts a bunch stranding structure, where multiple
Aluminum Wires are twisted together to enhance
Flexibility and mechanical strength. The number of strands and wire diameter vary by cross-sectional area:
The DC resistivity of the
Aluminum Conductor at 20℃ is ≤0.0282Ω·mm²/m, which is higher than that of copper (≤0.017241Ω·mm²/m) but optimized through the bunch stranding process to reduce transmission losses. The rated current-carrying capacity of the conductor is tested under standard underground laying conditions (soil thermal resistivity of 1.5K·m/W, ambient temperature of 25℃):
To address the issue of aluminum conductor oxidation in underground humid environments, the conductor surface is treated with hot-dip tinning. The tin layer has a thickness of ≥5μm, which forms a dense protective film to isolate the aluminum from moisture and oxygen in the soil, effectively slowing down oxidation. The tin-plated layer also improves the conductor’s solderability, facilitating reliable connections with terminals during installation.
1.1.3 Insulation Layer Parameters
The insulation layer is made of crosslinked polyethylene (XLPE) material, processed through a chemical crosslinking process using dicumyl peroxide (DCP) as the crosslinking agent. The crosslinking degree of the XLPE insulation is ≥75%, tested via the hot-set method (heating at 200℃ under 0.2MPa load for 15 minutes, with a deformation rate ≤10% and recovery rate ≥80%). This high crosslinking degree ensures the insulation layer has excellent heat resistance and mechanical strength.
The thickness of the XLPE insulation layer is strictly controlled based on the conductor cross-sectional area to ensure sufficient insulation strength:
The XLPE insulation layer has a long-term allowable operating temperature of 90℃ and can withstand short-circuit temperatures up to 250℃ for a duration of ≤5 seconds. This heat resistance allows the cable to operate stably in underground environments where soil temperatures may fluctuate between -10℃ and 40℃. Additionally, the XLPE material has excellent chemical stability, resisting erosion from common acids (such as dilute sulfuric acid and hydrochloric acid) and alkalis (such as sodium hydroxide solution) in the soil, ensuring the insulation layer’s performance remains unchanged over long-term use.
1.1.4 Sheath Layer and Waterproof Parameters
The sheath layer is made of modified polyvinyl chloride (PVC) material, which is a blend of PVC resin, waterproofing agents (such as calcium stearate), anti-aging agents (such as 2,6-di-tert-butyl-p-cresol), and flame retardants (such as aluminum hydroxide). This modified PVC sheath has enhanced waterproof, anti-aging, and flame-retardant properties compared to conventional PVC.
The thickness of the PVC sheath varies with the cable’s overall structure:
The mechanical properties of the PVC sheath are critical for withstanding underground stresses: tensile strength ≥12MPa, elongation at break ≥150% at room temperature. After aging (100℃ for 168 hours), the tensile strength retention rate is ≥80%, and the elongation at break retention rate is ≥70%, ensuring the sheath maintains its protective function over time. The waterproof performance of the sheath is rated IP68, verified by a 24-hour immersion test at room temperature—after immersion, the cable’s insulation resistance shows no significant decrease (≥500MΩ·km), and there is no water intrusion into the inner insulation layer.
The flame-retardant performance of the PVC sheath meets the requirements of GB/T 18380.1-2008 (Single vertical combustion test for
Electric Cables and wires). When a 1kW flame is applied to the sheath for 15 seconds, the flame self-extinguishes within 60 seconds after the fire source is removed, and no dripping material ignites the cotton placed 1m below the cable. The limiting oxygen index (LOI) of the sheath material is ≥30%, indicating it is difficult to burn and can inhibit flame spread in case of
Underground Cable trench fires.
1.1.5 Overall Cable Dimensions and Weight
The overall dimensions and weight of the cable are important for transportation, storage, and on-site laying:
16mm² 2-core cable: Outer diameter ≈16mm, weight ≈0.32kg/m. Despite its slightly higher weight, the aluminum conductor’s lightweight advantage still reduces overall handling intensity compared to copper-core cables of the same cross-sectional area.
The minimum bending radius of the cable is 12 times its outer diameter, allowing it to be bent in narrow underground spaces (such as small cable shafts or crowded cable trenches) without damaging the insulation or sheath. This flexibility is crucial for adapting to complex underground laying paths.
1.2 Feature Applications
The 2-core XLPE insulated PVC sheathed aluminum core waterproof underground power cable (1000V) has a wide range of feature applications due to its excellent waterproof performance, cost-effectiveness, and adaptability to underground environments. It is widely used in municipal engineering, residential areas, industrial parks, agricultural fields, and other low-voltage power distribution scenarios.
1.2.1 Municipal Engineering
In municipal engineering projects, such as urban road lighting, underground pipe gallery power supply, and public square power distribution systems, the cable plays a key role. Urban road lighting requires cables to be laid underground along the road to avoid above-ground obstacles and ensure pedestrian safety. The cable’s IP68 waterproof rating ensures it can withstand water accumulation in underground trenches caused by rain or road cleaning. For example, in a 5km urban road lighting project, the 6mm² 2-core cable is used to connect 200 street lamps (each with a power of 150W). The 32A rated current-carrying capacity of the 6mm² conductor is sufficient to supply power to 10-12 street lamps per circuit, reducing the number of cables and simplifying the laying process.
Underground pipe galleries are another important application scenario. The cable is used to supply power to monitoring equipment (such as temperature and humidity sensors), ventilation systems, and emergency lighting in the pipe gallery. The modified PVC sheath’s anti-aging and corrosion-resistant properties allow the cable to operate stably in the enclosed, potentially humid environment of the pipe gallery for 20-30 years. The 10mm² 2-core cable is often selected for this scenario, as its 45A rated current-carrying capacity can meet the power demand of multiple pieces of equipment in a single pipe gallery section.
1.2.2 Residential Community Power Distribution
In residential communities, the cable is widely used in underground parking lot power supply, courtyard lighting, and household incoming lines. Underground parking lots have high humidity and are prone to water accumulation during rainy seasons, making the cable’s waterproof performance critical. The 6mm² 2-core cable is used for emergency lighting and small power outlets in parking lots, while the 10mm² 2-core cable is used for the main power supply of parking lot ventilation fans and charging piles (for small electric vehicles). For example, in a residential community with 1000 parking spaces, 50 10mm² 2-core cables are used to supply power to 200 charging piles (each with a power of 3.5kW), ensuring stable charging for residents’ vehicles.
Courtyard lighting in residential communities requires cables to be laid underground to maintain the community’s appearance. The 6mm² 2-core cable is ideal for this purpose, as its lightweight and small outer diameter make it easy to lay under lawns or flower beds without damaging the landscape. The cable’s flame-retardant sheath also reduces the risk of fire caused by short circuits, protecting the safety of residents and property.
Household incoming lines in high-rise residential buildings often use the 10mm² or 16mm² 2-core cable. The 10mm² cable is suitable for small and medium-sized households (with a maximum power demand of 10kW), while the 16mm² cable is used for large households (with a power demand of 12-15kW). The aluminum conductor’s cost advantage reduces the overall project cost for the community, while the XLPE insulation’s stable performance ensures reliable power supply to each household.
1.2.3 Small Industrial Plants
Small industrial plants, such as food processing factories, garment factories, and hardware workshops, use the cable for underground power distribution to production equipment and auxiliary facilities. The 16mm² 2-core cable is commonly used to supply power to medium-power equipment, such as small compressors (5.5kW) and sewing machines (1.5kW per unit). The 60A rated current-carrying capacity of the 16mm² conductor can supply power to 3-4 compressors or 20-25 sewing machines per circuit, improving the efficiency of power distribution.
The cable’s resistance to oil and chemical corrosion makes it suitable for food processing factories, where there may be oil splashes or cleaning agent residues in the underground environment. The modified PVC sheath resists erosion from vegetable oil, mineral oil, and common cleaning agents (such as sodium hypochlorite solution), ensuring the cable’s service life is not affected. Additionally, the cable’s flame-retardant performance meets the fire safety requirements of industrial plants, reducing the risk of fire spreading through
Underground Cables.
1.2.4 Agricultural Irrigation Systems
In agricultural fields, the cable is used to supply power to underground irrigation pumps and field lighting. Agricultural irrigation requires cables to be laid underground to avoid damage from farm machinery (such as tractors and harvesters) and to withstand the humid environment of farmland soil. The 10mm² or 16mm² 2-core cable is selected based on the power of the irrigation pump: the 10mm² cable for small pumps (3kW) and the 16mm² cable for medium pumps (5.5kW).
The cable’s aluminum conductor is lightweight, making it easy to lay over long distances (e.g., 500-1000m) in farmland without excessive labor costs. The IP68 waterproof rating ensures the cable can withstand waterlogging in the soil caused by heavy rain or irrigation, preventing conductor oxidation and insulation failure. The flame-retardant sheath also reduces the risk of fire caused by accidental contact with farmland straw or other flammable materials.
1.3 Material and Style
The conductor is made of high-purity aluminum (purity ≥99.7%) sourced from qualified suppliers, ensuring excellent electrical conductivity. High-purity aluminum is selected because it has lower resistivity compared to low-purity aluminum alloys, reducing power loss during transmission. The aluminum is processed into wires through a drawing process, where aluminum rods are pulled through diamond dies to form wires of the required diameter. The drawing process is carried out at room temperature to avoid changing the aluminum’s crystal structure and affecting its conductivity.
After drawing, the aluminum wires undergo a hot-dip tinning process. The tinning process involves immersing the aluminum wires in a molten tin bath (temperature 230-250℃) for 2-3 seconds, followed by air cooling to form a uniform tin layer on the surface. The tin layer (thickness ≥5μm) has several key functions:
The aluminum wires are then stranded into conductors using a bunch stranding machine. The bunch stranding process twists the wires in the same direction, which enhances the conductor’s flexibility and makes it easier to bend during underground laying. The stranding pitch (distance between two adjacent turns of the wire) is controlled at 15-20 times the conductor diameter—too small a pitch would increase production costs, while too large a pitch would reduce flexibility.
The insulation layer uses high-quality XLPE material, produced by crosslinking low-density polyethylene (LDPE) with dicumyl peroxide (DCP) as the crosslinking agent. The LDPE resin used has a melt flow rate (MFR) of 2.0-3.0g/10min (190℃, 2.16kg), which ensures good processability during extrusion. The crosslinking process transforms the linear LDPE molecules into a three-dimensional network structure, significantly improving the material’s properties:
Heat Resistance: XLPE’s long-term operating temperature is 90℃, compared to 70℃ for conventional polyethylene. This allows the cable to operate in underground environments with high soil temperatures (up to 40℃) without insulation degradation. The short-circuit withstand temperature of 250℃ (≤5s) also protects the cable from damage during transient current spikes.
Dielectric Properties: XLPE has a low dielectric constant (2.2-2.4 at 50Hz) and dielectric loss tangent (tanδ ≤0.0005), which minimizes energy loss during power transmission. For a 1km length of 16mm² cable, the dielectric loss is only about 0.5W at full load—negligible compared to the total power transmitted.
Chemical Stability: XLPE is resistant to most organic and inorganic substances in soil, including dilute acids, alkalis, and salts. It does not swell or degrade when exposed to these chemicals, ensuring a service life of 20-30 years underground.
The XLPE insulation is extruded onto the conductor using a single-screw extruder with a precision die. The extrusion process is controlled to ensure uniform thickness—any deviation (beyond ±0.1mm) is detected by an online laser thickness gauge, which triggers an adjustment to the extruder speed or die position. After extrusion, the insulation undergoes a chemical crosslinking process in a continuous vulcanization (CV) tube, where high-temperature nitrogen (220-250℃) activates the DCP crosslinking agent. This ensures a crosslinking degree of ≥75%, verified by the hot-set test.
1.3.3 Sheath Material: Modified Flame-Retardant Waterproof PVC
The sheath layer is made of modified PVC, a blend of PVC resin, waterproofing agents, anti-aging agents, flame retardants, and plasticizers. Each component is carefully selected to enhance the sheath’s performance for underground use:
PVC Resin: Suspension polymerization PVC resin with a K value of 65-70 is used, providing good mechanical strength and flexibility. The K value reflects the molecular weight of PVC—higher K values improve strength but reduce processability, so 65-70 is a balance for sheath applications.
Waterproofing Agent: Calcium stearate (added at 1-2 phr, parts per hundred resin) is incorporated to improve water resistance. Calcium stearate fills microvoids in the PVC matrix, preventing water molecules from penetrating the sheath. This, combined with the dense PVC structure, gives the sheath an IP68 waterproof rating.
Anti-Aging Agent: 2,6-di-tert-butyl-p-cresol (BHT, 0.5-1 phr) is added to resist oxidation and UV aging. Although the cable is laid underground, small amounts of UV light may reach it through soil gaps, and BHT prevents the PVC from becoming brittle over time. After 168 hours of aging at 100℃, the sheath’s tensile strength retention rate is ≥80%, ensuring long-term flexibility.
Flame Retardant: Aluminum hydroxide (ATH, 50-60 phr) is used as a non-halogen flame retardant. When exposed to fire, ATH decomposes and releases water vapor, which cools the sheath and dilutes combustible gases. This, combined with the char layer formed by PVC decomposition, gives the sheath an LOI of ≥30% and passes the GB/T 18380.1-2008 vertical combustion test.
Plasticizer: Diisononyl phthalate (DINP, 30-40 phr) is added to improve flexibility. DINP is a non-toxic plasticizer that provides long-term flexibility to the sheath—even at -15℃, the sheath remains flexible enough to withstand bending without cracking.
The modified PVC sheath is extruded onto the
Insulated Conductor using a single-screw extruder, with the barrel temperature controlled at 140-180℃ (lower than XLPE extrusion to prevent PVC decomposition). A vacuum sizing sleeve is used during extrusion to ensure the sheath has a smooth surface and uniform outer diameter. After extrusion, the sheath is cooled in a water tank (20-25℃) to solidify, ensuring dimensional stability.
1.3.4 Cable Style: 2-Core Compact Stranded Structure
The cable adopts a 2-core compact stranded structure, consisting of four layers from the inside out: tinned aluminum conductor, XLPE insulation, semi-conductive water-blocking tape, and modified PVC sheath. This structure is optimized for underground laying:
2-Core Stranding: The two insulated conductors are twisted together in a concentric stranding pattern, with a stranding pitch of 15-20 times the cable’s outer diameter. For the 10mm² cable (outer diameter 14mm), the stranding pitch is 210-280mm. This twisting reduces the cable’s overall size and makes it more flexible—easier to bend around obstacles in underground trenches. The 2-core design also simplifies wiring: one core for the live wire and one for the neutral wire (or two live wires for 220V single-phase systems), eliminating the need for additional cables.
Semi-Conductive Water-Blocking Tape: Between the insulated conductors and the PVC sheath, a layer of semi-conductive water-blocking tape is wrapped. This tape is composed of a non-woven fabric base coated with a water-swellable polymer (e.g., sodium polyacrylate). If the PVC sheath is accidentally damaged and water enters, the polymer swells to form a gel-like barrier, preventing water from spreading along the cable core. This adds a second line of defense against water intrusion, critical for underground applications where sheath damage may go unnoticed.
Smooth Sheath Surface: The outer surface of the PVC sheath is extruded to be smooth and flat, with no protrusions or defects. This reduces friction during laying—when the cable is pulled through a conduit, the smooth surface minimizes resistance, protecting the sheath from scratches. The sheath is also marked with product information (model, specification, voltage rating, manufacturer) using UV-resistant inkjet printing, ensuring the information remains legible for the cable’s service life.
1.4 Production Process
The production of the 2-core XLPE insulated PVC sheathed aluminum core waterproof underground power cable (1000V) involves six key steps, each with strict quality control to ensure the final product meets performance standards.
1.4.1 Conductor Preparation: Drawing and Tinning
Step 1: Aluminum Wire Drawing
The raw material is 8mm-diameter high-purity aluminum rods (purity ≥99.7%). The rods are fed into a continuous wire drawing machine, which draws them through a series of diamond dies with decreasing diameters to form aluminum wires of the required size. The drawing process is divided into 4-6 passes to avoid excessive deformation (which could reduce conductivity). For example, to produce 1.05mm-diameter wires for the 6mm² conductor, the aluminum rod is drawn through dies with diameters 6.5mm, 5.0mm, 3.8mm, 2.5mm, 1.8mm, and finally 1.05mm. During drawing, a water-based lubricant (containing sodium stearate) is used to reduce friction and cool the wire, preventing surface scratches. The drawing speed is controlled at 80-120m/min, depending on the wire diameter—slower for smaller diameters to ensure precision.
After drawing, the aluminum wires are annealed in a nitrogen-protected annealing furnace to eliminate internal stress. The annealing temperature is 350-400℃, and the holding time is 10-15 minutes. Annealing improves the wire’s ductility, reducing its brittleness and making it easier to strand. The annealed wires are tested for conductivity—only those with a conductivity of ≥61% IACS (International Annealed Copper Standard) are accepted.
Step 2: Conductor Stranding
The annealed aluminum wires are stranded into conductors using a bunch stranding machine. The number of wires per conductor is determined by the cross-sectional area: 7 wires for 6mm² and 10mm², 19 wires for 16mm². The stranding machine twists the wires in the same direction (right-hand lay) at a speed of 300-500rpm. The stranding pitch is set to 12-16 times the conductor diameter—for the 10mm² conductor (diameter 4.14mm), the pitch is 50-66mm. This pitch balance ensures flexibility and prevents the strands from loosening. During stranding res varies by conductor cross-sectional area: 7 strands for 6mm² and 10mm², and 19 strands for 16mm². The stranding process follows a concentric pattern, with one wire at the center and subsequent layers arranged symmetrically around it. For the 6mm² conductor (7 strands), the central wire is surrounded by 6 outer wires, ensuring a round and compact structure. The stranding pitch is controlled at 12-16 times the conductor diameter—for a 3.15mm-diameter 6mm² conductor, the pitch ranges from 37.8mm to 50.4mm. This pitch balance ensures the conductor is flexible enough for bending while maintaining mechanical stability.
During stranding, a polyester binding tape is wrapped around the
Stranded Conductor to hold the strands together and prevent loosening. The tape overlap rate is 20-30% to ensure full coverage. After stranding, the conductor’s diameter and roundness are inspected using a laser diameter gauge: the diameter tolerance must be within ±1%, and the roundness error (difference between maximum and minimum diameters) must be ≤0.2mm. Any conductor with irregular shape or loose strands is rejected.
Step 3: Tinning of Conductors
To prevent aluminum oxidation in underground humid environments, the
Stranded Conductors undergo hot-dip tinning. The process takes place in a continuous tinning line, which includes three key stages:
Pre-Cleaning: The conductor is immersed in a 5-10% hydrochloric acid solution at 50-60℃ for 5-10 minutes to remove surface oxides and oil stains. It is then rinsed with deionized water and dried with hot air (120-150℃) to ensure no moisture remains.
Fluxing: The cleaned conductor is dipped in a zinc chloride-based flux solution (20-30% concentration) at 60-80℃. The flux removes any remaining oxides and forms a protective layer that prevents re-oxidation before tinning.
Hot-Dip Tinning: The fluxed conductor is passed through a molten tin bath (temperature 230-250℃). The tin bath contains high-purity tin (≥99.9% purity) with a small amount of lead (0.5-1% to improve tin fluidity). The conductor’s residence time in the bath is 3-5 seconds, ensuring the tin fully adheres to the aluminum surface. After exiting the bath, the conductor passes through a pair of squeeze rollers to control the tin layer thickness (≥5μm) and remove excess tin. A cold air blower then cools the tinned conductor to room temperature, solidifying the tin layer.
The tinned conductor is inspected for tin layer uniformity using a microscope—any bare spots, blisters, or uneven thickness (variation >1μm) result in rejection. The tinned surface should be bright and smooth, with no visible defects.
1.4.2 XLPE Insulation Extrusion and Crosslinking
Step 1: Material Preparation
The
XLPE Insulation Material is prepared by mixing LDPE resin (MFR 2.0-3.0g/10min), DCP crosslinking agent (1.5-2.0 phr), antioxidant (0.1-0.2 phr of 1010), and lubricant (0.5 phr of polyethylene wax) in a high-speed mixer. The mixing process is conducted at 80-100℃ for 10-15 minutes, with a mixing speed of 800-1000rpm, to ensure uniform dispersion of additives. The mixed material is then granulated using a twin-screw extruder (barrel temperature 120-160℃) to form XLPE pellets. The pellets are stored in a dry warehouse (moisture content ≤0.1%) for at least 24 hours before use to prevent moisture absorption, which could cause bubbles in the insulation layer.
Step 2: Insulation Extrusion
The tinned conductor is fed into a single-screw extruder (screw diameter 65mm, length-diameter ratio 25:1) for insulation extrusion. The extruder barrel is divided into three temperature zones:
The extruder is equipped with a precision crosshead die, custom-designed for each conductor specification. For the 6mm² conductor, the die inner diameter is 4.75mm (to achieve 0.8mm insulation thickness on a 3.15mm conductor); for the 16mm² conductor, the die inner diameter is 7.5mm (1.2mm insulation on a 5.1mm conductor). The extrusion speed is synchronized with the conductor’s line speed (60-80m/min for 6mm², 50-70m/min for 16mm²) to maintain uniform insulation thickness.
An online laser thickness gauge is installed immediately after the die to monitor the insulation thickness in real time. The gauge measures the thickness at 4 points around the conductor circumference every 100ms. If the thickness deviates beyond ±0.1mm, the system automatically adjusts the extruder speed or die position to correct it. Any section of cable with insulation thickness outside the tolerance is marked and cut off after extrusion.
Step 3: Chemical Crosslinking
After extrusion, the insulated conductor enters a continuous vulcanization (CV) tube for crosslinking. The CV tube is a stainless steel pipe (length 30-40m, diameter 150mm) divided into three sections:
Vulcanization Section: Temperature 220-250℃, pressure 1.5-2.5MPa (using high-purity nitrogen), to promote the crosslinking reaction. The DCP decomposes at high temperature, generating free radicals that link LDPE molecules into a three-dimensional network. The residence time in this section is 2-3 minutes (depending on cable speed), ensuring a crosslinking degree of ≥75%.
After exiting the CV tube, the insulated conductor is tested for crosslinking degree using the hot-set method. A 100mm-long sample is loaded with a 0.2MPa weight and heated at 200℃ for 15 minutes. The sample’s deformation rate (ΔL/L0) must be ≤10%, and the recovery rate (after cooling to room temperature) must be ≥80%. Samples that fail this test indicate insufficient crosslinking, and the entire production batch is re-inspected.
1.4.3 Semi-Conductive Water-Blocking Tape Wrapping
To enhance waterproof performance, a layer of semi-conductive water-blocking tape is wrapped around the two insulated conductors after they are twisted into a 2-core cable core.
Step 1: 2-Core Twisting
The two insulated conductors (each with XLPE insulation) are fed into a cabling machine for twisting. The twisting adopts a concentric stranding pattern, with a stranding pitch of 15-20 times the cable core’s outer diameter. For the 10mm² cable (each insulated conductor has an outer diameter of 6.14mm, so the 2-core bundle has an outer diameter of ~10mm), the stranding pitch is 150-200mm. The twisting speed is 40-60m/min, and a tension controller ensures both conductors are twisted with uniform tension to avoid uneven stress.
Step 2: Water-Blocking Tape Wrapping
A tape wrapping machine is integrated with the cabling machine to apply the semi-conductive water-blocking tape. The tape is 25mm wide and 0.15mm thick, composed of a non-woven polyester base coated with a water-swellable polymer (sodium polyacrylate, content ≥30%). The wrapping process uses a spiral overlap method, with an overlap rate of 50% (each wrap covers half of the previous one) to ensure no gaps. The tape tension is controlled at 5-10N to ensure tight adhesion to the cable core without stretching or breaking the tape.
The semi-conductive nature of the tape (volume resistivity ≤10³Ω·cm) ensures electrical continuity between the insulation layer and the sheath, preventing partial discharge that could damage the insulation. The water-swellable polymer is inert in dry conditions but swells to 50-100 times its original volume when exposed to water, forming a tight gel barrier that blocks water from spreading along the cable core. After wrapping, the cable core is inspected for tape coverage—any missing sections or loose wraps trigger re-wrapping.
1.4.4 PVC Sheath Extrusion
The final protective layer—modified PVC sheath—is extruded onto the cable core (with water-blocking tape) to provide mechanical protection and waterproofing.
Step 1: Material Preparation
The modified PVC material is prepared by mixing PVC resin (K value 65-70), DINP plasticizer (30-40 phr), ATH flame retardant (50-60 phr), calcium stearate waterproofing agent (1-2 phr), BHT anti-aging agent (0.5-1 phr), and lubricant (0.5 phr of polyethylene wax) in a low-speed mixer. The mixing is conducted at 60-80℃ for 15-20 minutes (speed 300-500rpm) to avoid overheating (which could cause PVC decomposition). The mixture is then extruded into pellets using a single-screw extruder (barrel temperature 140-170℃) and cooled in a water tank before being stored in a ventilated warehouse.
Step 2: Sheath Extrusion
The cable core (with water-blocking tape) is fed into a sheath extruder (screw diameter 80mm, length-diameter ratio 20:1). The extruder barrel has three temperature zones:
The extruder uses a crosshead die with an inner diameter matching the desired sheath outer diameter. For the 6mm² cable (cable core outer diameter ~8mm), the die inner diameter is 12mm (to achieve 1.2mm sheath thickness); for the 16mm² cable (cable core outer diameter ~12mm), the die inner diameter is 16mm (1.6mm sheath thickness). A vacuum sizing sleeve is attached to the die exit to control the sheath’s outer diameter and roundness. The vacuum pressure is 0.04-0.06MPa, which pulls the molten PVC tightly against the sizing sleeve’s inner wall, ensuring a smooth surface and uniform diameter.
After extrusion, the
Sheathed Cable passes through a water cooling tank (temperature 20-25℃) for 5-10 minutes to solidify the PVC. The cooling is gradual—first using warm water (30-40℃) to prevent rapid cooling (which could cause sheath cracking), then cold water to reach room temperature. A traction machine pulls the cable through the cooling tank at a speed synchronized with the extrusion rate to avoid tension or slack.
Step 3: Sheath Marking and Inspection
An inkjet printer is installed after the cooling tank to mark the sheath surface with product information. The marking includes the cable model (e.g., “VV22-0.6/1kV 2×10mm²”), voltage rating (1000V), manufacturer name, production date, and batch number. The ink is UV-resistant and adheres to the PVC surface with adhesion ≥5N/25mm (tested via tape peel method).
The sheathed cable is then inspected for sheath quality:
1.4.5 Final Product Testing
Before packaging, the finished cable undergoes a series of comprehensive tests to ensure compliance with standards (GB/T 12706.1-2020 and IEC 60502-1).
Electrical Tests:
DC Resistance Test: Using a DC resistance tester, measure the conductor resistance at 20℃. Maximum resistance: 6mm² ≤4.91Ω/km, 10mm² ≤2.95Ω/km, 16mm² ≤1.83Ω/km.
Mechanical Tests:
Flame and Waterproof Tests:
Only cables passing all tests are labeled and packaged for shipment.
2. Product General Information
2.1 Packaging
The 2-core XLPE insulated PVC sheathed aluminum core waterproof underground power cable (1000V) is packaged to protect it from mechanical damage, moisture, and dust during storage and transportation, with packaging tailored to the cable’s length and cross-sectional area.
2.1.1 Primary Packaging: Cable Drums
Plastic Drums (for 6mm² and 10mm² Cables)
Cables with smaller cross-sectional areas (6mm², 10mm²) are typically wound onto plastic drums, as they are lighter and easier to handle. The drums are made of high-density polyethylene (HDPE) with a wall thickness of 5-8mm, ensuring durability without rusting (unlike steel) or rotting (unlike wood). The drum dimensions vary by cable length:
6mm² cable: 500m/drum, drum diameter 600mm (flange) × 300mm (barrel), weight ~10kg (empty), total weight ~100kg (with 500m cable).
The drum’s inner barrel is lined with a 0.2mm-thick polyethylene film to prevent direct contact between the cable and the drum, avoiding sheath scratches. The flange is reinforced with radial ribs to withstand stacking pressure—up to 3 drums can be stacked vertically (for 6mm² drums) without deformation.
Steel Drums (for 16mm² Cables)
The 16mm² cable (heavier, 0.32kg/m) is wound onto galvanized steel drums to handle higher weight. The drums are made of 2.5mm-thick galvanized steel (zinc coating ≥80μm) to resist corrosion. Dimensions: 800mm (flange diameter) × 400mm (barrel diameter), empty weight ~30kg, cable length 300m/drum (total weight ~126kg). The drum’s steel shaft (diameter 50mm) is reinforced with bearings to facilitate smooth unwinding during on-site laying. A rubber gasket is placed between the flange and barrel to seal out moisture, and the inner barrel is lined with foam padding (5mm thick) to protect the cable sheath.
2.1.2 Labeling and Documentation
Each drum is labeled with two weather-resistant PVC labels (one on each flange), containing the following information:
Product details: Model, cross-sectional area, voltage rating, length, weight.
A waterproof document pouch is attached to the drum flange, containing a copy of the Certificate of Quality (COQ), Test Report, Packing List, and (for export) Commercial Invoice and Bill of Lading. All documents are provided in both Chinese and English.
2.2 Transportation
The cable is transported by professional logistics providers with experience in handling
Electrical Cables, ensuring on-time and damage-free delivery. Transportation plans are customized based on the shipment volume, destination, and local regulations.
2.2.1 Transportation Modes
Road Transportation (Domestic)
For domestic shipments, 10-20 ton flatbed trucks are used. The drums are secured to the truck bed using steel straps (tension ≥500kg) and wooden blocks (to prevent rolling). The maximum number of drums per truck depends on drum size: 10-12 wooden drums (6mm²) or 8-10 steel drums (16mm²).
Drivers are provided with a “Transportation Guide” that includes the shipment route, drum weight, center of gravity, and emergency contact information. Routes are selected to avoid rough roads or areas with height/weight restrictions. For shipments in extreme temperatures (≤-15℃ or ≥40℃), the truck is equipped with insulation mats to protect the cable from temperature damage.
Rail Transportation (Long-Distance Domestic)
For distances ≥500km, rail freight is more cost-effective. The drums are loaded into covered railcars to avoid exposure to rain or snow. A non-slip rubber mat is laid on the railcar floor, and the drums are fixed with steel chains (breaking strength ≥2000kg) to withstand train vibrations. Rail transportation typically takes 3-7 days, depending on the destination, and the logistics provider provides daily shipment updates.
Sea Transportation (Export)
For international shipments, the cable is transported in 20ft or 40ft containers. The drums are arranged in a single layer (to avoid stacking pressure) and secured to the container floor using container twist locks. Desiccant bags (500g each, 10-15 bags per container) are placed inside to absorb moisture during sea transit.
The container is labeled with “Fragile—Handle with Care”, “Waterproof”, and “Export Cargo” signs. Sea transportation takes 15-45 days (depending on the port), and the logistics provider handles customs clearance, providing the customer with a Bill of Lading and customs documents.
2.2.2 Transportation Precautions
Temperature Control: During transportation in temperatures ≤-15℃, the cable must not be bent (to prevent sheath cracking) until it reaches room temperature. In temperatures ≥40℃, the truck/container is ventilated to avoid overheating the cable.
Damage Inspection: Upon delivery, the customer is required to inspect the drum’s packaging for damage (broken flanges, torn HDPE film). If damage is found, the customer must take photos and notify the manufacturer within 24 hours to initiate a damage claim.
2.3 Shipment
The shipment process is designed to be transparent and efficient, with clear communication between the manufacturer, logistics provider, and customer.
2.3.1 Order Processing and Shipment Scheduling
After receiving the customer’s order, the sales team confirms the delivery time (7-15 days for standard specifications, 20-30 days for custom lengths). Once production is complete and the cable passes testing, the sales team sends a “Shipment Confirmation” email to the customer, including:
Customers can request a pre-shipment inspection (PSI) to verify the cable’s quality before shipment. The manufacturer provides access to the factory or shares digital copies of test reports for inspection.
2.3.2 Shipment Tracking and Delivery Notification
The logistics provider assigns a unique tracking number to each shipment, which the customer can use to track the shipment status via the provider’s website or mobile app. The manufacturer also sends real-time updates:
Delivery Reminder: Sent 24-48 hours before arrival, to allow the customer to prepare for unloading (e.g., arrange forklifts, clear storage space).
Upon delivery, the customer signs a delivery receipt to confirm receipt of the shipment. The receipt includes a note on the drum’s condition (e.g., “No damage to packaging”). If the customer is unavailable to receive the shipment, the logistics provider will reschedule delivery at a convenient time.
2.4 Samples
The manufacturer provides free or low-cost samples to help customers evaluate the cable’s quality, performance, and suitability for their specific underground projects.
2.4.1 Sample Specifications and Request Process
Sample Details: Samples are 1-3 meters long, available for all three specifications (6mm²/10mm²/16mm²). Each sample is cut from the same production batch as bulk cables, ensuring it accurately represents the bulk product’s quality. The sample includes a small label with the same information as the bulk cable (model, specification, production date).
Request Method: Customers can request samples via the manufacturer’s website (online sample request form), email, or phone. The request form requires the following information: customer name, company, contact information, desired sample specification and quantity, application scenario (e.g., “residential underground parking lot”), and delivery address.
2.4.2 Sample Delivery and Technical Support
Delivery Logistics
Samples are packaged in a compact cardboard box (size 35×15×10cm) lined with foam padding to prevent bending or scratching during transit. The box is labeled with the customer’s contact information, sample specification, and a “Fragile—Do Not Bend” warning. For domestic customers, samples are shipped via express delivery (e.g., SF Express, ZTO Express) with a delivery time of 2–3 business days. For international customers, DHL or FedEx is used, with an average delivery time of 5–7 business days.
The manufacturer covers the shipping cost for customers who place a bulk order (≥5 drums) within 30 days of receiving the sample. For customers only requesting samples without immediate bulk purchase intent, a nominal shipping fee (ranging from \(10 to \)30, depending on destination) is charged, which is refundable upon subsequent bulk order placement.
Technical Guidance for Sample Testing
Each sample package includes a “Sample Test Guide” (available in Chinese and English) that outlines step-by-step methods for evaluating key performance indicators, including:
The manufacturer’s technical team is available via phone or email to answer test-related questions. For example, if a customer struggles to measure insulation resistance, technical engineers can provide real-time guidance on instrument calibration or test environment control.
2.4.3 Sample Feedback and Follow-Up
Within 7–10 days of sample delivery, the sales team conducts a follow-up with the customer to collect feedback. Common feedback topics include:
If the customer is satisfied with the sample, the sales team assists with bulk order details, such as confirming delivery schedules, negotiating pricing, and arranging pre-shipment inspections. If the customer has concerns (e.g., “The sheath is too stiff in cold weather”), the technical team analyzes the issue and offers solutions—for instance, adjusting the PVC plasticizer ratio to improve low-temperature flexibility and providing a revised sample for re-evaluation within 5 working days.
2.5 After-Sales Service
The manufacturer provides comprehensive after-sales service to ensure the cable’s long-term stable operation in underground environments, covering warranty, fault resolution, maintenance guidance, and continuous improvement based on customer feedback.
2.5.1 Warranty Policy
Warranty Coverage and Period
The cable comes with a standard 5-year warranty from the date of delivery, covering defects in materials and workmanship, including:
The warranty does not cover damage caused by improper use, such as:
Warranty Claim Process
To file a warranty claim, the customer must submit the following documents to the after-sales team within 7 days of discovering the defect:
A copy of the delivery receipt (proving purchase date and batch number).
High-resolution photos/videos of the defect (showing the damage location, extent, and surrounding soil conditions).
A brief report on the cable’s installation and operation history (e.g., laying depth, soil type, load current).
The after-sales team reviews the claim within 3 working days and may dispatch engineers to the site for inspection (domestic customers: 48-hour on-site response; international customers: 72-hour coordination with local authorized service partners). If the defect is confirmed to be covered by the warranty, the manufacturer offers three resolution options:
Free Replacement: For severely damaged cables (e.g., insulation breakdown affecting power supply), a new cable of the same specification is shipped within 5–7 days, with the manufacturer covering all transportation and installation costs.
On-Site Repair: For minor defects (e.g., local sheath damage), engineers are sent to repair the cable using heat-shrinkable waterproof sleeves or PVC repair tape, ensuring the repaired section meets IP68 waterproof standards.
Partial Refund: If the customer prefers not to replace or repair the cable, a partial refund (proportional to the damaged length) is provided based on the original purchase price.
2.5.2 Fault Handling for Underground Operation
24/7 Emergency Support
The manufacturer operates a 24-hour emergency hotline to address urgent faults, such as cable short-circuits causing power outages in residential communities or industrial plants. When a fault is reported, the support team first collects key information (cable specification, installation depth, fault symptoms) and provides preliminary troubleshooting steps:
If remote troubleshooting fails, the manufacturer dispatches a technical team—for domestic projects, engineers arrive on-site within 24 hours (48 hours for remote areas); for international projects, local service partners (trained and certified by the manufacturer) are activated within 72 hours.
Root Cause Analysis and Prevention
After resolving the fault, the manufacturer issues a “Fault Analysis Report” within 10 working days, which includes:
For example, if a batch of 10mm² cables experiences conductor oxidation in a coastal area, the report may recommend adding an additional layer of anti-corrosion grease to the conductor surface for future orders destined for high-salt soil environments.
2.5.3 Regular Maintenance Guidance
To extend the cable’s service life (20–30 years under proper maintenance), the manufacturer provides a “Under
Ground Cable Maintenance Manual” to customers, outlining annual and quarterly maintenance tasks:
Quarterly Maintenance (Customer-Performed)
Annual Maintenance (Manufacturer-Assisted)
The manufacturer offers an optional annual maintenance service (charged at \(50–\)100 per drum) where engineers visit the site to perform:
2.5.4 Customer Feedback and Continuous Improvement
The manufacturer collects after-sales feedback through multiple channels, including:
Post-Maintenance Surveys: Sent to customers after annual maintenance, rating service quality (e.g., engineer professionalism, problem-solving efficiency) on a 5-point scale.
Annual Customer Seminars: Held in major cities (e.g., Shanghai, Guangzhou, Dubai), where customers share on-site operation experiences and provide input on product upgrades.
Feedback is analyzed quarterly by a cross-departmental team (sales, technical, production) to identify improvement opportunities. For example:
If feedback indicates “water-blocking tape failure in high-moisture soil,” the R&D team replaces the sodium polyacrylate polymer with a more water-absorbent bentonite-based material, improving water-swelling efficiency by 30%.
Annually, the manufacturer publishes a “Customer Satisfaction Report” that summarizes feedback trends, improvement measures, and future service plans. This report is shared with all customers to demonstrate transparency and commitment to quality.
Conclusion
The 2-core XLPE insulated PVC sheathed aluminum core waterproof underground power cable (1000V) is a specialized solution tailored to the unique challenges of underground low-voltage power distribution. From a product-specific perspective, its precise specification parameters (1000V voltage rating, 6mm²/10mm²/16mm² cross-sections), high-performance materials (tinned aluminum conductor, XLPE insulation, modified waterproof PVC sheath), and rigorous production processes (conductor tinning, XLPE crosslinking, water-blocking tape wrapping) ensure reliable waterproofing, mechanical durability, and electrical stability in underground environments.
From the general product information perspective, thoughtful packaging (wooden/steel drums with moisture-proof layers), flexible transportation modes (road/rail/sea), transparent shipment tracking, customer-centric sample services, and comprehensive after-sales support (5-year warranty, 24/7 technical assistance, maintenance guidance) further enhance its value proposition.
Whether for municipal projects, residential communities, small industrial plants, or agricultural irrigation systems, this cable balances cost-effectiveness (aluminum conductor) with performance (IP68 waterproofing, flame retardancy), making it an ideal choice for underground low-voltage power transmission. The manufacturer’s commitment to continuous improvement, driven by customer feedback, ensures the product remains adaptable to evolving project requirements—such as harsher soil conditions or stricter environmental standards—solidifying its position in the global underground cable market.
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