In the safe operation system of electrical systems, earthing protection is a crucial link to ensure the safety of personnel and equipment. As the core carrier of the earthing system, the performance and quality of the earthing cable directly determine the reliability of earthing protection. The 70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable, as a professional product designed for high-current earthing scenarios, is widely used in industrial, civil, power, rail transit, and other fields due to its precise specification design, high-quality material selection, clear identification system, and stable comprehensive performance. This article will conduct a comprehensive and in-depth analysis of this earthing cable from two core dimensions: the product itself and general product information, providing professional and detailed reference materials for industry practitioners, purchasers, and engineering and technical personnel to assist them in making scientific decisions in the design, construction, and maintenance of earthing systems.
I. From the Perspective of the Product Itself: In-depth Analysis of Core Performance and Structure
(I) Precise Specification Parameters for High-Current Earthing
Specification parameters are the fundamental guarantee for the performance of earthing cable products, directly determining their current-carrying capacity, insulation protection effect, and applicable scenario boundaries. In the specification design of the 70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable, the particularities of high-current earthing scenarios (such as equipment short circuits, lightning-induced leakage, etc.) are fully considered. Each parameter has undergone verification against industry standards and testing under actual working conditions to ensure high compatibility with earthing requirements in different scenarios.
1. Conductor Specifications: Dual Guarantee of High Conductivity and High Flexibility
The conductor cross-sectional area of this earthing cable is 70mm², and the setting of this specification is based on precise calculations of high-current diversion needs. In accordance with GB/T 3956-2008 "Conductors of Cables", the DC resistance of the 70mm² copper conductor at 20℃ is ≤0.268Ω/km. The extremely low resistance means minimal loss during current transmission, enabling rapid diversion of high current generated during short circuits or leakage to the ground. In terms of rated current-carrying capacity, when the cable is laid in air (ambient temperature 30℃), its rated current-carrying capacity can reach 225A, fully covering the earthing current requirements of most industrial equipment and power systems. For example, when a 100kW high-voltage motor suffers from insulation damage, the short-circuit current can reach 150-200A, and the 70mm² conductor can easily carry and quickly divert this current, preventing the equipment casing from being charged for an extended period.
The conductor is made of high-purity electrolytic copper (copper content ≥99.95%). Compared with ordinary copper materials, high-purity electrolytic copper removes impurities and oxygen, improving conductivity by approximately 5%-8%, while also having superior ductility and toughness. To further enhance the flexibility of the conductor, a multi-strand stranding process is adopted: hundreds of fine
Copper Wires with a diameter of 0.2mm are stranded in a "concentric layer stranding" manner (inner-layer copper wires stranded clockwise, outer-layer copper wires stranded counterclockwise) with a specific pitch (12-16 times the conductor outer diameter). This stranding process significantly improves the bending performance of the conductor. At room temperature, the bending radius can reach 6 times the cable's outer diameter (solid hard
Copper Conductors typically require more than 10 times), and even in a low-temperature environment of -15℃, the bending radius can be controlled within 8 times the outer diameter without brittleness or cracking. In actual construction, the conductor can easily bypass obstacles such as building wall corners and equipment metal brackets, adapting to complex wiring paths such as cable trenches, wall embedding, and equipment interiors, reducing construction difficulty and the risk of conductor damage.
In addition, the surface of the conductor undergoes tin-plating treatment (tin layer thickness ≥8μm). The tin layer not only effectively prevents oxidation and corrosion of the copper conductor (especially in humid and dusty environments) but also improves the contact conductivity between the conductor and terminal blocks, reducing contact resistance. In a salt spray test, the tinned conductor was placed in a 5% sodium chloride solution spray environment (temperature 35℃, relative humidity 95%) for 48 consecutive hours. The tin layer showed no rust or peeling, and the conductor resistance change rate was ≤2%, ensuring long-term stable operation in harsh environments.
2. Insulation Layer Specifications: Perfect Combination of Safety Identification and Reliable Protection
The insulation layer is a key barrier for the earthing cable to isolate the conductor from external components and prevent accidental leakage, and it also serves as an intuitive identifier for the earthing circuit. The insulation layer of this earthing cable is made of polyvinyl chloride (PVC) material and strictly adopts a green-yellow dual-color design in accordance with international standards (IEC 60446), forming a dual function of "function + identification".
From the perspective of insulation performance parameters, the thickness of the
PVC Insulation layer is precisely calculated and controlled between 1.2-1.4mm (tolerance ≤±0.1mm). The sufficient thickness ensures insulation strength: at 20℃, when a 500V DC voltage is applied, the insulation resistance is ≥100MΩ; after a 1000-hour thermal aging test (temperature 100℃), the insulation resistance still remains ≥50MΩ, with a tensile strength retention rate of ≥80% and an elongation at break retention rate of ≥70%. This proves that it is less prone to insulation aging and performance degradation during long-term use. At the same time, the insulation layer has good voltage impact resistance, capable of withstanding a 1500V AC voltage (frequency 50Hz) for a 1-minute withstand voltage test without breakdown or flashover, avoiding insulation failure caused by voltage fluctuations.
The green-yellow dual-color identification is a core feature of this insulation layer, adopting a "1:1 alternating distribution" color scheme (each segment of green and yellow is 50mm in length). This color combination is an internationally recognized dedicated identifier for earthing, with extremely high recognition. In construction scenarios, even in dimly lit cable trenches or equipment rooms, construction personnel can quickly distinguish the earthing circuit from live wires and neutral wires through the color, reducing safety hazards caused by wiring errors (such as mistakenly connecting the earthing cable to a live wire) from the source. To ensure color durability, high-stability color masterbatches (lightfastness grade ≥7) are used. After a 1000-hour ultraviolet aging test (simulating outdoor exposure), the color shows no significant fading and remains clearly recognizable.
In addition, the PVC insulation layer also has excellent flame retardancy and mechanical strength. Its flame retardancy reaches UL94 V-0 level. In the vertical burning test, the flame self-extinguishes within 10 seconds, and no drippings ignite the absorbent cotton below, effectively preventing the spread of fire. In terms of mechanical strength, the insulation layer has a tensile strength of ≥12MPa and an elongation at break of ≥150%. During daily construction and use, it can resist slight friction and extrusion (such as friction between the cable and pipes during laying, with external extrusion strength ≤50N/cm²) without damage.
3. Overall Performance Parameters: Stable Performance for Multi-Scenario Adaptation
In addition to the core parameters of the conductor and insulation layer, the overall performance parameters of this earthing cable further ensure its stable operation in different scenarios. In terms of operating temperature range, this earthing cable can work normally in an environment of -15℃ to 70℃: in a low-temperature environment (-15℃), the cable shows no brittleness, and its bending performance meets construction requirements; in a high-temperature environment (70℃), the conductor resistance change rate is ≤5%, and the insulation layer shows no softening or deformation, ensuring that the earthing function is not affected by temperature.
Earthing resistance is a key indicator to measure the effectiveness of the earthing system. When this earthing cable is used in conjunction with earthing electrodes and earthing grids, the earthing resistance can be stably controlled below 4Ω (meeting the earthing resistance requirements of most scenarios in GB 50169-2016 "Code for Construction and Acceptance of Earthing Devices"). For example, in the equipment earthing scenario of an industrial workshop, using this earthing cable to connect the equipment casing to the earthing electrode results in an earthing resistance of only 2.5Ω, far below the standard requirement, ensuring that leakage current can be quickly diverted to the ground.
In addition, this earthing cable also has a certain degree of chemical corrosion resistance. After being immersed in a 10% concentration hydrochloric acid or sodium hydroxide solution for 72 hours, the insulation layer shows no swelling or cracking, and the conductor resistance change rate is ≤3%, making it suitable for scenarios with slight chemical corrosion such as chemical workshops and sewage treatment plants. In terms of weather resistance, after a 2000-hour outdoor exposure test (simulating wind, rain, and ultraviolet environments), the insulation layer shows no aging or peeling, and the conductor conductivity does not decrease significantly, making it suitable for outdoor power facilities, rail transit lines, and other open-air scenarios.
(II) Characteristic Applications Focused on Multi-Fields
Based on the above specification parameters and performance advantages, the application of the 70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable is highly focused on high-current earthing and high-safety demand fields. According to the functional requirements and risk levels of different scenarios, it has formed diversified application directions, covering four core fields: industrial production, civil construction, power facilities, and rail transit, providing stable and reliable current diversion guarantees for various earthing systems.
1. Industrial Production Field: Ensuring Equipment and Personnel Safety
In industrial production scenarios, large mechanical equipment (such as CNC machine tools, injection molding machines, high-voltage motors) and power distribution systems operate with high currents. Once insulation damage occurs, high-current leakage is likely to occur, posing a serious threat to operators and equipment. The application of this earthing cable in the industrial field mainly focuses on the following scenarios:
Casing Earthing of Large Mechanical Equipment: For high-voltage motors (power 50-200kW), CNC machine tools, and other equipment in industrial workshops, if their casings become charged due to insulation damage, it may cause electric shock to personnel or equipment burnout. Using a 70mm² earthing cable to connect the equipment casing to the earthing electrode can quickly divert leakage current (for example, the short-circuit current of a 200kW motor is approximately 180A, and this earthing cable can easily carry and divert it to the ground within 0.1 seconds), while triggering the leakage protector to trip and cut off the main power supply. In the stamping workshop of an auto parts manufacturing plant, after using this earthing cable for 8 sets of 200kW stamping machines, there have been no safety accidents caused by equipment leakage in nearly 3 years, and the equipment failure rate has decreased by 60%.
Protective Earthing and Working Earthing of Power Distribution Systems: The protective earthing of industrial power distribution systems (such as workshop power distribution cabinets and distribution boxes) needs to carry short-circuit fault currents, while working earthing needs to stabilize the system potential. Both have high requirements for the current-carrying capacity of the earthing cable. This earthing cable can be used as the protective earthing main line and working earthing branch line of the power distribution system, connecting the power distribution cabinet casing, neutral terminal, and earthing grid. In a power distribution room renovation project in a chemical industrial park, this earthing cable was used to construct a protective earthing system. When a short-circuit fault occurred in the power distribution cabinet, the short-circuit current reached 220A, and the earthing cable successfully diverted the current to the earthing grid without causing equipment damage, with a fault response time of only 0.08 seconds, far exceeding the industry average.
Earthing in Explosion-Proof Environments: In explosion-proof environments such as petrochemical and coal mining industries, the earthing of electrical equipment not only needs to prevent leakage but also avoid explosions caused by static accumulation. The high conductivity of this earthing cable can quickly divert static electricity generated during equipment operation (such as static electricity generated during the stirring process of chemical reactors), and the flame retardancy of its PVC insulation layer (UL94 V-0 level) can prevent the expansion of fire accidents. After an oilfield's oil production platform used this earthing cable for the earthing of explosion-proof motors and instruments, the static elimination efficiency increased by 80%, and no safety hazards caused by static electricity have occurred.
2. Civil Construction Field: Building a Comprehensive Electrical Safety Barrier
Civil construction (such as high-rise buildings, residential communities, and commercial complexes) is closely related to people's daily lives, and the reliability of the earthing system directly affects residents' electrical safety and building fire safety. The application of this earthing cable in civil construction mainly includes:
Lightning Protection Earthing of High-Rise Buildings: High-rise buildings (with 10 or more floors) are prone to lightning strikes. If the high current generated by lightning strikes cannot be diverted in a timely manner, it may damage electrical equipment in the building and cause fires. Using this earthing cable as the lightning protection earthing main line to connect the rooftop lightning rod, lightning protection belt, and earthing electrode can carry the instantaneous high current generated by lightning strikes (the current of a single lightning strike can reach 10-20kA, and the short-term withstand current of this earthing cable can reach 30kA), safely diverting the current to the ground. In a 38-story residential building project in a first-tier city, after using this earthing cable to construct a lightning protection earthing system, no electrical equipment in the building was damaged during multiple thunderstorm weather events, and the lightning protection effect was significant.
Protective Earthing of Household Appliances and High-Power Equipment: High-power household appliances in civil buildings, such as air conditioners (power 2-5kW) and electric water heaters (power 2-3kW), are prone to leakage if their insulation is damaged due to aging. Using this earthing cable to connect the appliance casing to the household earthing terminal can quickly divert leakage current, preventing electric shock to personnel. In the indoor distribution box renovation of a residential community, this earthing cable was equipped for the air conditioner and water heater circuits of each household. After the renovation, the number of electric shock complaints caused by household appliance leakage decreased from 15 per year to 0.
Earthing Main Line of Elevator Machine Rooms and Power Distribution Rooms: The elevator machine rooms (elevator power 10-30kW) and power distribution rooms of high-rise buildings are core areas of the electrical system, and their earthing main lines need to carry large currents. Using this earthing cable as the earthing main line to connect the elevator casing, power distribution cabinet, and earthing grid can ensure the rapid diversion of current in case of equipment failure. After the elevator machine room of a commercial complex used this earthing cable for earthing, the downtime of the elevator caused by electrical faults was reduced from 8 hours per month to 1 hour, significantly improving operational stability.
3. Power Facilities Field: Ensuring Stable Operation of Power Systems
Power facilities (such as substations, power distribution rooms, and transmission line tower foundations) are core nodes of power transmission. Their earthing systems not only need to prevent equipment leakage but also stabilize the system potential and resist lightning strikes, placing high requirements on the current-carrying capacity and reliability of the earthing cable. The application of this earthing cable in power facilities mainly includes:
Earthing Grid Branch Lines of Substations: The earthing grid of a substation needs to connect high-voltage equipment such as transformers and circuit breakers to divert short-circuit fault currents and lightning currents. Using this earthing cable as the earthing grid branch line to connect the equipment earthing terminal and the earthing grid main line can ensure the rapid diffusion of fault currents (for example, the short-circuit current of a 110kV substation is approximately 200A, and this earthing cable can carry it stably). After a 220kV substation used this earthing cable to construct the earthing grid branch lines, during a transformer short-circuit fault, the earthing cable successfully diverted a 210A fault current without causing equipment damage, and the fault handling time was reduced to 30 minutes.
Earthing Electrode Connection in Power Distribution Rooms: The earthing electrodes (such as galvanized steel pipe earthing electrodes and copper rod earthing electrodes) in power distribution rooms need to be connected to equipment through earthing cables to form a complete earthing circuit. The high conductivity and corrosion resistance of this earthing cable can ensure stable current transmission between the earthing electrode and the equipment. In the renovation of a county-level power distribution room, this earthing cable was used to connect 10 galvanized steel pipe earthing electrodes and the power distribution cabinet. The test results showed that the earthing resistance was only 1.8Ω, meeting the strict requirements of the power system, and the operational stability of the power distribution room was improved by 70%.
Earthing of Transmission Line Tower Foundations: The outdoor transmission line tower foundations need to be earthed to resist lightning strikes. Using this earthing cable to connect the tower foundation and the earthing electrode can carry the instantaneous high current generated by lightning strikes. After the 110kV transmission line tower foundations in a certain area used this earthing cable for earthing, the number of line tripping events caused by lightning strikes decreased from 12 per year to 2, significantly improving the stability of power supply.
4. Rail Transit Field: Coping with Complex Electromagnetic and High-Current Environments
The operating environment of rail transit (subways, light rails) is complex, with problems such as strong electromagnetic interference and high-current leakage. and the earthing system must have anti-interference and high-current-carrying capabilities. The application of this earthing cable in the rail transit field mainly includes:
Equipment Earthing in Subway Stations: Traction converters, platform screen door systems, and signal equipment in subway stations operate with high currents and are susceptible to electromagnetic interference. The earthing system must simultaneously achieve leakage protection and electromagnetic shielding. Using this earthing cable to connect the equipment casing to the station earthing grid can quickly divert leakage current (for example, the short-circuit current of a traction converter is approximately 220A, which this earthing cable can stably carry). At the same time, the low-resistance characteristic of its Copper Core can reduce electromagnetic interference, ensuring the normal operation of signal equipment. After 20 stations of Metro Line 3 in a certain city adopted this earthing cable, the equipment failure rate decreased by 50%, and the signal transmission error rate dropped from 0.5% to 0.1%.
Track Earthing in Light Rail Lines: Light rail tracks need to maintain good earthing with the ground to divert track leakage current and prevent track corrosion. Using this earthing cable to connect the tracks to the earthing electrodes along the line can ensure that the track earthing resistance is ≤4Ω, allowing leakage current to be quickly diverted to the ground. After Light Rail Line 1 in a certain city used this earthing cable for track earthing, the track corrosion rate decreased by 40%, the track maintenance cycle was extended from 1 year to 2 years, and maintenance costs were reduced by 50%.
Earthing of Power Facilities Along Rail Transit Lines: Power facilities such as substations and distribution boxes along subway and light rail lines need to withstand harsh outdoor environments and lightning strike risks. The weather resistance and lightning protection performance of this earthing cable can ensure stable earthing of the facilities in thunderstorms, high temperatures, and humid environments. After 15 outdoor distribution boxes along a light rail line adopted this earthing cable for earthing, they withstood the test of 3 rainy seasons and summers without any equipment damage caused by earthing faults.
(III) High-Quality and Durable Material and Style Design
Material selection and style design are key supports for the quality and user experience of earthing cable products. The 70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable adheres to the principle of "safety first, performance-oriented" in material selection and balances practicality and construction convenience in style design, forming a product feature of "high quality + high adaptability".
1. Material Selection: Strict Control at Every Layer to Build a Solid Safety Barrier
The material system of this earthing cable covers three core parts: conductor, insulation layer, and protective layer (optional). The material of each part undergoes multiple rounds of screening and testing to ensure product performance and safety from the source.
Conductor Material: High-Purity Electrolytic Copper: As mentioned earlier, the conductor is made of electrolytic copper with a purity of ≥99.95%, produced through the process of "electrolytic refining - continuous casting and rolling - wire drawing and annealing". During the wire drawing process, the copper rod is drawn into fine copper wires with a diameter of 0.2mm, which are then subjected to annealing treatment (temperature 400-450℃, holding time 2 hours) to eliminate internal stress generated during wire drawing, reduce conductor hardness (Brinell hardness ≤50HB), and improve flexibility. The annealed copper wires are subjected to concentric layer stranding, with the inner and outer layers stranded in opposite directions to ensure a compact conductor structure, reduce the skin effect during current transmission (the skin effect causes current to concentrate on the conductor surface, increasing losses), and reduce losses by approximately 10%.
Insulation Layer Material: Modified PVC: The insulation layer is made of modified polyvinyl chloride (PVC) material. Compared with ordinary PVC, modified PVC significantly improves heat resistance, weather resistance, and flame retardancy by adding environmentally friendly plasticizers (dioctyl phthalate, DOP), calcium-zinc composite stabilizers, and chlorinated paraffin flame retardants. Among them, the plasticizer DOP not only improves the flexibility of the insulation layer (keeping the insulation layer elastic even at -15℃) but also complies with the EU RoHS environmental standard without releasing harmful substances; the calcium-zinc composite stabilizer replaces the traditional lead salt stabilizer to further improve environmental performance and avoid heavy metal pollution; the chlorinated paraffin flame retardant enables the insulation layer to meet the UL94 V-0 flame retardant standard, forming a flame-retardant carbon layer when exposed to fire to prevent the spread of flames.
Protective Layer Material (Optional): Low-Smoke Halogen-Free Polyolefin: For outdoor, humid, or highly corrosive scenarios, this earthing cable can be equipped with a low-smoke halogen-free polyolefin protective layer. The protective layer has a thickness of 0.8-1.0mm and is tightly wrapped around the insulation layer using an extrusion process, with excellent weather resistance (passing a 3000-hour outdoor exposure test without aging) and corrosion resistance (withstanding immersion in 10% sulfuric acid solution for 72 hours without damage). The low-smoke halogen-free characteristic of the protective layer ensures that no toxic or harmful gases are released in case of fire, making it suitable for crowded places such as subway stations and shopping malls.
2. Style Design: Practicality-Oriented to Improve Construction Efficiency
The style design of this earthing cable focuses on construction convenience, identification clarity, and structural compactness, aiming to reduce construction difficulty and improve project progress while ensuring performance.
Cable Outer Diameter Design: The outer diameter of the cable is optimized through structural simulation. The outer diameter of the 70mm² earthing cable (without a protective layer) is controlled at 12-13mm, which is 10%-15% smaller than that of similar products on the market. This compact design is more conducive to threading in narrow pipelines (such as Φ20mm electrical conduits) or dense cable trays. In the actual construction of a high-rise residential project, this cable can be threaded into a Φ20mm conduit along with 1 other cable, improving the utilization rate of the conduit by 40%.
Color and Marking Design: In addition to the green-yellow dual-color insulation layer, the cable surface is printed with clear, durable markings using laser engraving technology. The marking content includes the product model (e.g., 70mm² Copper Earthing Cable), rated voltage (450/750V), production batch number, and certification logos (UL, CE, GB). The marking interval is 500mm, which meets the requirement of "visible marking every 1 meter" specified in international standards. The laser-engraved markings are resistant to friction and high temperatures—even after rubbing the surface with sandpaper 50 times, the markings remain legible, facilitating later maintenance and quality tracing.
End Treatment Design: The two ends of the cable are pre-treated with tin plating (tin layer thickness ≥10μm) to prevent the conductor from being oxidized during storage and construction. For large orders, the cable ends can also be customized with copper lugs (such as DT-type copper lugs) according to customer requirements. The copper lugs are crimped using a hydraulic crimping machine, with a crimping pressure of 120kN, ensuring a tight connection between the copper lugs and the conductor (the pull-out force ≥5kN). This pre-treatment reduces on-site construction time by 30% and avoids connection failures caused by improper on-site crimping.
(IV) Rigorous and Standardized Production Processes
The production process of the 70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable follows the principle of "full-process quality control", with strict operating standards and testing procedures established for each process from raw material input to finished product inspection, ensuring that every meter of cable meets high-quality requirements.
1. Conductor Stranding Process: Laying the Foundation for Conductivity and Flexibility
The conductor stranding process is the first key step in cable production, directly affecting the conductor's conductivity and flexibility. The production line uses a fully automatic high-speed stranding machine (speed up to 800 rpm) with a precision tension control system.
First, the raw copper wires (0.2mm in diameter) are loaded into the pay-off racks of the stranding machine. A total of 350 copper wires are used for the 70mm² conductor, requiring 350 pay-off racks. Each pay-off rack is equipped with a tension controller to ensure that the tension of each copper wire is uniform (tension deviation ≤3%). Uniform tension prevents uneven stress distribution in the conductor during stranding, which could lead to wire breakage during bending or increased contact resistance.
During stranding, the copper wires are twisted into a concentric layer structure according to the set pitch (12-16 times the conductor outer diameter). The stranding machine is equipped with a pitch monitoring sensor that automatically adjusts the twisting speed if the pitch deviates by more than ±5%, ensuring the consistency of the stranding pitch. After stranding, the conductor is passed through a diameter measuring instrument (measurement accuracy ±0.01mm) to check the outer diameter (required to be 8.5-9.0mm for the 70mm² conductor). If the outer diameter exceeds the range, the machine stops automatically for adjustment.
Finally, the
Stranded Conductor undergoes a "tensile test"—a 1-meter sample is taken, and a tensile force of 500N is applied. The elongation at break is required to be ≥30%. Only conductors that pass the test are sent to the next process.
2. Conductor Tin-Plating Process: Enhancing Corrosion Resistance
The conductor tin-plating process is crucial to improving the conductor's corrosion resistance and contact conductivity. The production line uses an electrolytic tin-plating system with a plating speed of 15-20m/min.
First, the stranded conductor is degreased in an alkaline degreasing tank (concentration 10% sodium hydroxide solution, temperature 60℃) for 10 minutes to remove surface oil stains. Then, it is pickled in a hydrochloric acid tank (concentration 5%) for 5 minutes to remove the oxide layer on the conductor surface. After pickling, the conductor is rinsed with pure water to remove residual acid, preventing acid corrosion of the conductor.
Next, the conductor enters the electrolytic tin-plating tank. The plating solution is a tin sulfate solution (concentration 200g/L), with a current density of 2A/dm² and a plating temperature of 40℃. The thickness of the tin layer is controlled by adjusting the plating speed and current density—when the speed is 15m/min and the current density is 2A/dm², the tin layer thickness can reach 8μm. After plating, the conductor is rinsed with pure water again and then dried in a hot air oven (temperature 120℃) for 5 minutes to remove surface moisture.
After tin-plating, the conductor undergoes a "salt spray test" (sampling ratio 1%)—the sample is placed in a 5% sodium chloride solution spray environment for 48 hours. The tin layer is required to have no rust or peeling, and the conductor resistance change rate is ≤2%.
3. Insulation Extrusion Process: Ensuring Uniformity and Insulation Performance
The insulation extrusion process coats the tin-plated conductor with a uniform green-yellow dual-color PVC insulation layer, and its precision directly determines the cable's insulation performance and identification effect. The production line uses a twin-screw extruder with a computerized control system (temperature control accuracy ±1℃) and a dual-color extrusion die.
First, the modified PVC material (green and yellow) is dried in a dehumidifying dryer (temperature 80℃) for 4 hours to reduce moisture content (≤0.3%), avoiding insulation bubbles caused by moisture vaporization during extrusion.
The dried green and yellow PVC materials are fed into two separate feed hoppers of the extruder. The extruder barrel is divided into 5 temperature zones, with temperatures set to 140℃ (feeding zone), 160℃ (compression zone), 175℃ (melting zone), 180℃ (metering zone), and 170℃ (die head). The temperature gradient ensures that the PVC material is fully melted and mixed uniformly.
The melted green and yellow PVC materials are extruded through a dual-color extrusion die (concentricity tolerance ≤0.05mm) onto the tin-plated conductor. The die is designed to ensure that the green and yellow materials are distributed alternately at a 1:1 ratio, with a clear boundary between colors. A laser diameter gauge installed at the die exit monitors the insulation layer thickness in real time (measurement accuracy ±0.01mm), ensuring that the thickness is 1.2-1.4mm. If the thickness deviates, the system automatically adjusts the extrusion speed or die gap to correct it.
After extrusion, the cable enters a water cooling tank (cooling water temperature 20-25℃) for rapid cooling. The cooling length is 8 meters, ensuring that the insulation layer is fully solidified. The cooled cable then passes through a traction machine (traction speed synchronized with the extrusion speed) to avoid stretching the insulation layer.
4. Protective Layer Extrusion Process (Optional): Enhancing Environmental Adaptability
For cables requiring a protective layer, the protective layer extrusion process is added after the insulation extrusion. The process is similar to the insulation extrusion but with adjusted parameters based on the protective layer material.
The low-smoke halogen-free polyolefin material is dried in a dehumidifying dryer at 100℃ for 4 hours, then fed into a dedicated extruder. The extruder barrel temperature zones are set to 165℃, 185℃, 200℃, 205℃, and 195℃. The protective layer is extruded onto the
Insulated Cable through a crosshead die, with the thickness controlled at 0.8-1.0mm.
After extrusion, the cable is cooled in a two-stage cooling tank: the first stage uses water at 20℃ for rapid cooling, and the second stage uses air cooling to reduce the surface moisture of the protective layer. The cooled cable then undergoes a "protective layer adhesion test"—the protective layer is peeled off manually, and the adhesion force is required to be ≥20N/100mm, ensuring that the protective layer is tightly bonded to the insulation layer and does not peel off during installation.
5. Post-Production Testing and Inspection: Ensuring 100% Qualification
After the production of the cable is completed, a comprehensive post-production testing and inspection process is carried out to ensure that every roll of cable meets the quality standards.
Electrical Performance Testing: Random samples are taken from each production batch (sampling ratio 3%) for DC resistance testing (using a micro-ohmmeter with an accuracy of ±0.1%), insulation resistance testing (using a megohmmeter with a range of 0-1000MΩ), and AC withstand voltage testing (applying 1500V AC voltage for 1 minute). All test data must meet the specified requirements (DC resistance ≤0.268Ω/km; insulation resistance ≥100MΩ; no breakdown in withstand voltage test).
Mechanical Performance Testing: Samples are tested for tensile strength and elongation at break of the insulation layer and protective layer (using a universal testing machine with a speed of 50mm/min), and bending resistance (bending 1000 times at a radius of 6 times the outer diameter). The test results must meet the standard requirements (tensile strength retention rate ≥80%, elongation at break retention rate ≥70%; no conductor breakage after bending).
Flame Retardancy Testing: Every 5 production batches, a sample is sent to a third-party testing agency (such as SGS, BV) for UL94 V-0 flame retardancy testing. The sample is subjected to a vertical burning test, and the flame must self-extinguish within 10 seconds without drippings igniting the absorbent cotton below.
Visual and Dimensional Inspection: All finished cables are inspected for appearance (no scratches, bubbles, or color unevenness on the insulation layer and protective layer) and dimensions (outer diameter, insulation thickness, protective layer thickness) using a visual inspection platform and a digital caliper (accuracy ±0.01mm). Unqualified products are marked and reprocessed or scrapped.
II. From the Perspective of General Product Information: Comprehensive Supporting Services
In addition to the excellent performance of the product itself, a complete set of general product information—including packaging, transportation, shipping, samples, and after-sales service—is crucial to ensuring the safe delivery of the product, convenient use by customers, and long-term satisfaction. The 70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable provides a full range of supporting services, covering every link from the factory to the customer's application.
(I) Scientific and Protective Packaging
The packaging of the cable is designed to protect the product from damage during transportation and storage, while also facilitating handling, inventory management, and on-site use. The packaging scheme is formulated according to the cable length, order quantity, and transportation method.
1. Inner Packaging: Protecting the Cable Surface
Each roll of cable is available in two standard lengths: 50 meters and 100 meters, to meet the different needs of small and medium-sized projects. For the 50-meter roll (weight about 25kg), the inner packaging uses a moisture-proof kraft paper (thickness 0.2mm) coated with a polyethylene (PE) film. The PE film has a moisture permeability of ≤3g/m²·24h, effectively blocking moisture from the external environment and preventing the cable insulation layer from absorbing moisture and aging. The kraft paper is wrapped around the cable roll with a tension of 10-12N, ensuring it fits tightly without looseness—this prevents the cable from rubbing against the packaging during transportation, which could scratch the insulation layer. At both ends of the 50-meter roll, a circular EPE foam pad (thickness 15mm, diameter 300mm) is added to absorb impact forces when the rolls are stacked, preventing the edge of the cable roll from being crushed.
For the 100-meter roll (weight about 50kg), an additional layer of PVC shrink film is wrapped outside the kraft paper. The shrink film is heated to 130℃ to shrink tightly around the roll, forming a rigid protective shell that further enhances moisture resistance and prevents the roll from unwinding during handling. The shrink film also has a UV-resistant coating, which can resist ultraviolet radiation during outdoor storage, avoiding color fading of the green-yellow insulation layer.
2. Outer Packaging: Ensuring Structural Stability
The outer packaging is divided into carton packaging and wooden pallet packaging, depending on the order quantity. For small orders (1-3 rolls), double-layer corrugated cartons (bursting strength ≥2000kPa) are used. The carton size is customized according to the cable roll dimensions—for example, the carton for a 50-meter roll is 350mm×350mm×200mm, with reinforced cardboard corners (thickness 5mm) added to the four corners to improve impact resistance. A 50mm wide reinforced tape is applied at all seams (cross-shaped sealing) to prevent the carton from splitting under the weight of the cable.
For large orders (≥5 rolls), wooden pallets (made of pine wood treated with anti-corrosion and anti-mite agents) are used. The pallets have a size of 1200mm×1000mm, with a load-bearing capacity of ≥800kg. The cable rolls are arranged on the pallet in a "single-layer" pattern (each pallet holds 6 rolls of 50-meter or 3 rolls of 100-meter) to avoid excessive pressure on the bottom rolls. The rolls are fixed with PET strapping (tensile strength ≥800N) in 4 directions (top, bottom, left, right), and a layer of waterproof PE film (thickness 0.25mm) is wrapped around the entire pallet—with 150mm overlaps between film layers to protect against rain and snow during outdoor transportation.
3. Labeling: Clear and Traceable Information
Each package is labeled with standardized information to facilitate identification, inventory management, and quality tracing. The label (made of waterproof synthetic paper with a thickness of 0.2mm) includes the following content:
Product Information: Model (70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable), length (50m/100m), Insulation Material (modified PVC), protective layer (if applicable: low-smoke halogen-free polyolefin), and production batch number (e.g., 20250915-02).
Quality Certification: Logos of relevant certifications (UL, CE, GB), and a QR code linking to the product's quality test report (scannable to view detailed data such as DC resistance, insulation resistance, and flame retardancy test results).
Handling Instructions: Symbols for "keep dry," "handle with care," "no stacking" (for cartons), and "maximum stacking 2 layers" (for pallets).
Shipping Information: Consignee name, address, contact number, and shipping mark (for international orders, including HS code: 7413001000).
(II) Efficient and Safe Transportation
To ensure the cable reaches the customer intact and on time, a professional transportation network is established, covering both domestic and international routes. The transportation mode is selected based on the destination, order urgency, and cost-effectiveness.
1. Domestic Transportation: Balancing Speed and Cost
In domestic markets, two main transportation modes are available: road transportation and rail transportation. Road transportation is preferred for short distances (≤600km) or urgent orders (delivery time ≤3 days). It uses closed trucks with temperature and humidity control systems—temperature is maintained at 5-35℃, and humidity ≤65% to avoid damage caused by extreme weather (e.g., low-temperature brittleness of the insulation layer or high-temperature softening). The trucks are equipped with GPS tracking devices, allowing customers to monitor the real-time location of the goods via a mobile app.
For long distances (≥1000km) or large-volume orders (≥10 pallets), rail transportation is more cost-effective (30% lower than road transportation) and has lower vibration (rail vibration amplitude ≤2mm, compared to 6mm for road transportation), reducing the risk of packaging damage. The cable pallets are loaded into container cars (20-foot containers for 8 pallets, 40-foot containers for 16 pallets) with anti-slip mats on the floor. Before loading, a pre-shipment inspection is conducted—an inspector checks the packaging integrity (no tears, water stains) and the tightness of the strapping, repairing any defects immediately.
2. International Transportation: Complying with Customs and Standards
For international orders, sea transportation and air transportation are the primary options. Sea transportation is used for large-volume orders (≥1 container) with a delivery time of 25-50 days (depending on the destination port). The wooden pallets are first treated with heat (temperature ≥56℃ for 30 minutes) to meet the ISPM 15 standard, avoiding quarantine issues at the destination country. The pallets are loaded into seaworthy containers, with wooden blocks placed around the rolls to prevent tipping during rough sea conditions. A 1.5kg moisture absorber is placed inside each container to control humidity (≤60%), preventing the cable from absorbing moisture during long voyages.
Air transportation is used for urgent orders (delivery time ≤7 days) or sample shipments. The cable rolls are repackaged in lightweight aluminum alloy cases (weight reduced by 45% compared to wooden pallets) to meet airline weight restrictions. The cases are lined with EVA foam (thickness 25mm) to absorb impact, and the total weight of each case is limited to 30kg.
All international shipments are accompanied by complete customs documents, including a commercial invoice (detailing product description, quantity, unit price, and total amount), packing list (matching the invoice with package dimensions, weight, and quantity), certificate of origin (CO) issued by the local chamber of commerce, and safety data sheet (SDS) for the
PVC Insulation Material. A dedicated customs clearance team reviews the documents 72 hours before shipment to ensure compliance with the destination country's regulations—for example, providing additional certifications (such as FCC for the US market or VDE for the European market) if required.
(III) Streamlined Shipping Process
The shipping process is designed to be transparent and efficient, with clear timelines and proactive communication to keep customers informed at every stage.
1. Order Confirmation and Production Scheduling
Upon receiving an order, the sales team sends an order confirmation email within 24 hours, outlining product details (specification, length, customization requirements), delivery terms (EXW, FOB, CIF), and payment terms. The production planning team then schedules production based on the order urgency: standard products (without protective layer) have a lead time of 5-7 working days, while customized products (with low-smoke halogen-free protective layer) require 10-12 working days.
A dedicated customer service representative is assigned to each order, providing weekly progress updates. For large projects (e.g., subway station grounding system orders), the representative shares photos or videos of the production process (e.g., conductor stranding, insulation extrusion) to allow the customer to monitor quality.
2. Pre-Shipment Inspection (PSI)
Before shipping, a third-party inspection agency (e.g., Intertek, BV) conducts a pre-shipment inspection. The inspection includes:
The inspection agency issues a PSI report, which is shared with the customer. If any non-conformities are found (e.g., insulation thickness below 1.2mm), production is paused until the issue is resolved—for example, re-extruding the insulation layer for defective rolls.
3. Shipment Notification and Tracking
Once the shipment is dispatched, the customer service representative sends a shipment notification email within 2 hours, including the carrier name, tracking number, estimated arrival date, and contact information of the local delivery agent. For sea shipments, the representative provides the container tracking number (e.g., from Maersk or COSCO) to allow the customer to monitor the container's location via the carrier's website. For air shipments, the air waybill number is provided for real-time tracking via DHL or UPS.
The representative follows up with the customer 1 day before the estimated arrival date to confirm receipt arrangements, and checks in again 3 days after delivery to ensure the goods are intact and meet expectations.
(IV) Flexible Sample Service
Recognizing that customers may need to test the cable's performance before placing a large order, a flexible sample service is offered to meet different testing needs.
1. Sample Types and Specifications
Two types of samples are available:
Standard Samples: 1-meter lengths of standard products (70mm², green-yellow PVC insulation, without protective layer) are provided free of charge (excluding shipping costs) for qualified customers (e.g., electrical contractors, construction companies, power utilities).
Customized Samples: Samples with specific configurations (e.g., with low-smoke halogen-free protective layer, pre-crimped copper lugs) are available upon request. A nominal fee (USD 80-120, depending on complexity) is charged, which is refundable if the customer places an order exceeding 500 meters within 3 months.
All samples are packaged in small plastic cases (200mm×150mm×80mm) with a sample information card, including product specifications, production date, key test data (e.g., DC resistance: ≤0.268Ω/km, flame retardancy: UL94 V-0), and contact information of the technical support team.
2. Sample Order and Delivery
Customers can request samples via the company's website, email, or through their sales representative. The request requires the following information: company name, contact person, application scenario (e.g., subway station equipment grounding, industrial workshop power distribution), and testing focus (e.g., corrosion resistance, bending performance).
Standard samples are shipped within 2 working days via express delivery (DHL, UPS), with a delivery time of 3-5 days for domestic shipments and 5-7 days for international shipments. Customized samples are shipped within 5 working days after production. The customer service representative provides the sample tracking number and follows up to confirm receipt.
3. Sample Testing Support
A technical engineer is assigned to each sample request to provide testing support. The engineer can:
Address Issues: If the sample fails to meet expectations (e.g., insufficient flexibility at low temperatures), the engineer identifies the cause (e.g., inappropriate plasticizer ratio in the insulation layer) and provides a revised sample if needed.
(V) Comprehensive After-Sales Service
A robust after-sales service system is established to address customer concerns and ensure long-term satisfaction, covering quality warranty, technical support, and complaint handling.
1. Quality Warranty
The 70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable comes with a 3-year warranty from the date of delivery. The warranty covers defects in materials and workmanship, such as:
To claim the warranty, the customer needs to provide:
Usage details (installation method, operating environment, and duration of use) to rule out improper use (e.g., exposure to concentrated acid or alkali).
The after-sales team reviews the claim within 48 hours. If approved, the team offers three solutions:
2. Technical Support and Training
Technical support is available throughout the product lifecycle, not just during the warranty period:
Installation Guidance: Providing detailed installation manuals (with step-by-step diagrams and safety precautions) and on-site installation guidance for large projects. For example, in a subway station grounding system project, technicians are dispatched to supervise the cable connection to the earthing grid, ensuring compliance with IEC 60364 (Electrical installations in buildings) standards and optimal grounding performance.
Troubleshooting: Offering 24/7 troubleshooting support via phone, email, or video call. If the cable's grounding resistance exceeds the standard, the technical team analyzes possible causes (e.g., poor contact with the earthing electrode, conductor oxidation) and provides solutions (e.g., cleaning the contact surface, re-plating the conductor). The response time for urgent issues (e.g., equipment leakage caused by grounding failure) is less than 2 hours.
Training Programs: Organizing quarterly training sessions for customers (electricians, maintenance personnel) at the company's training center or the customer's site. The training covers product performance (e.g., current-carrying capacity, corrosion resistance), installation best practices (e.g., cable bending, terminal crimping), and maintenance tips (e.g., regular insulation resistance testing). The training includes hands-on demonstrations—for example, teaching participants how to use a megohmmeter to test insulation resistance.
3. Complaint Handling and Continuous Improvement
Customer complaints are treated as opportunities to improve product quality and service. The complaint handling process follows these structured steps:
Registration: All complaints are logged in a centralized system, including details such as complaint date, customer information, product batch number, defect description, and impact on the customer's project.
Investigation: A cross-functional team (including representatives from production, quality control, and technical support) is assigned to investigate the root cause. For example, if a complaint is about insulation layer peeling, the team checks the insulation extrusion process parameters (temperature, speed) and the quality of the PVC material.
Resolution: The team develops a resolution plan within 3 working days and communicates it to the customer. For example, if the root cause is a faulty extrusion die, the plan includes replacing the die and providing new cable rolls.
Continuous Improvement: Root causes of complaints are shared with the relevant departments to implement corrective and preventive actions. For example, if multiple complaints relate to insufficient tin-plating thickness, the production department increases the plating time and adds an additional thickness inspection step. A monthly complaint report is generated to track trends, and the effectiveness of improvement actions is reviewed quarterly.
Conclusion
The 70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable stands out in the market as a reliable and high-performance solution for high-current grounding scenarios. Its strengths lie not only in its technical excellence—characterized by high-purity copper conductors for low-resistance current diversion, green-yellow dual-color PVC insulation for clear identification and reliable protection, and rigorous production processes ensuring consistency—but also in its wide applicability across industrial, civil, power, and rail transit fields.
Equally important is its comprehensive supporting services: scientific packaging protects the product during transportation, efficient transportation networks ensure timely delivery, flexible sample services facilitate pre-purchase verification, and robust after-sales support provides long-term peace of mind. Every aspect of the product, from material selection to after-sales troubleshooting, is designed to meet the strict safety and performance requirements of grounding systems.
As electrical systems become more complex and safety standards more stringent (driven by regulations such as GB 50169 and IEC 60364), the demand for high-quality
Grounding Cables will continue to grow. The 70mm² Copper Conductor Green/Yellow PVC Insulated Earthing Cable, with its combination of technical superiority and customer-centric services, is well-positioned to meet this demand. It is not just a cable product, but a critical component in safeguarding electrical systems, protecting personnel and equipment, and ensuring the stable operation of infrastructure across industries.
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