Development of Wear-Resistant, High-Strength, and High Flame-Retardant Power Cables

Development of Wear-Resistant, High-Strength, and High Flame-Retardant Power Cables

Abstract

This paper systematically investigates the design principles, material selection, manufacturing processes, and performance evaluation methods for wear-resistant, high-strength, and highly flame-retardant power cables. By analyzing the limitations of traditional cable materials and incorporating the latest advancements in modern polymer materials science, an innovative cable design scheme based on a multi-layer composite structure is proposed. The scheme employs a polyurethane-based composite material as the outer sheath layer, a silicone rubber flame-retardant layer as the intermediate layer, a galvanized steel wire braided armor layer as the reinforcement layer, an XLPE insulation layer as the electrical insulation layer, and an aluminum foil-copper wire braided composite shield layer. The research results indicate that the designed cable significantly outperforms traditional cable products in terms of wear resistance, mechanical strength, flame retardancy, and environmental adaptability. Through systematic testing and verification, the cable meets the requirements of the highest international flame-retardant standards such as IEC 60332-3A and BS 6387 CWZ, while also exhibiting excellent mechanical properties and long-term operational reliability. This study provides theoretical foundations and technical references for the research and development of high-performance power cables and holds significant importance for enhancing the safety and reliability of power systems.

Keywords: power cables; wear resistance; high strength; flame retardancy; composite materials; multilayer structure; testing standards

1.Introduction

1.1 Research Background and Significance

With the rapid development of modern power systems, the performance requirements for power cables, as critical carriers of electrical energy transmission, are increasingly demanding. This is particularly evident in application scenarios under complex and harsh environments, such as mining, marine engineering, rail transportation, and industrial automation. These fields impose extremely high demands on the wear resistance, mechanical strength, and flame retardancy of power cables. Traditional cable materials, such as PVC and ordinary rubber, often exhibit shortcomings in these extreme environments, including insufficient wear resistance, limited mechanical strength, and unsatisfactory flame retardant performance. These limitations can lead to shortened cable service life, increased maintenance costs, and even potential safety incidents.

The development of wear-resistant, high-strength, and highly flame-retardant power cables can not only meet the technical requirements of specific application scenarios but also enhance the overall safety and reliability of power systems. According to statistical data, cable failures account for a significant proportion of power system faults, with those caused by mechanical damage and fire being particularly prominent. Therefore, developing power cables with excellent comprehensive performance is of significant practical importance for ensuring the continuity of power supply, reducing operational and maintenance costs, and improving system safety.

Cable Performance Comparison Chart

1.2 Current Research Status at Home and Abroad

In recent years, scholars both domestically and internationally have conducted extensive research on cable materials and structural design. Globally, developed countries and regions such as the United States, Europe, and Japan have taken a leading role in the research and development of advanced cable technologies. The flame retardancy classification standards, including CMP, CMR, and CMG, established by Underwriters Laboratories (UL), have become industry benchmarks. The CEN standard EN 50575 published by the European Committee for Standardization specifies clear requirements for the fire performance of cables. Japan has achieved remarkable progress in high-temperature superconducting cables and specialty cables.

Domestically, in line with the implementation of the “Made in China 2025” strategy, the technological level of the cable industry has been continuously improving. In the area of flame-retardant materials, compounds such as Aluminum Trihydroxide (ATH), Magnesium Hydroxide (MH), and phosphorus-based flame retardants have been widely adopted. For reinforcement materials, the application of high-performance fibers like aramid fiber, glass fiber, and carbon fiber is increasingly prevalent. Research on insulating materials, including Cross-linked Polyethylene (XLPE), silicone rubber, and polyurethane, is continuously deepening.

However, there remains a market gap for cable products that simultaneously exhibit excellent wear resistance, high mechanical strength, and superior flame retardancy. Existing products often excel in one specific performance aspect but fall short in providing comprehensive properties to meet the demands of extreme operating environments. Therefore, conducting systematic research on wear-resistant, high-strength, and high flame-retardant power cables holds significant theoretical and practical value.

1.3 Research Objectives and Contents

The primary objective of this research is to develop a wear-resistant, high-strength, and high flame-retardant power cable with excellent comprehensive performance. The specific research contents include:

1.Systematically analyze the performance requirements for each functional layer of the cable and determine key performance indicators;

2.Screen and optimize materials for each functional layer and develop new composite materials;

3.Design a reasonable multilayer composite structure to achieve synergistic optimization of performance;

4.Optimize manufacturing process parameters to ensure the manufacturing quality of the cable;

5.Establish a comprehensive performance testing system to fully evaluate cable performance;

6.Analyze the long-term reliability of the cable in different application environments.

Through the systematic implementation of the above research contents, it is expected to obtain a power cable product that reaches an internationally advanced level in terms of wear resistance, mechanical strength, flame retardancy, and other aspects, providing technical support for applications in related fields.

%1. Cable Material Selection and Performance Analysis

2.1 Selection and Modification of Outer Sheath Materials

The outer sheath is the cable's outermost protective structure, directly subjected to mechanical, chemical, and physical actions from the external environment. While traditional PVC sheaths offer lower cost, they suffer from poor abrasion resistance, inadequate weather resistance, and low-temperature brittleness. This study selects polyurethane (PU) as the base material for the outer sheath due to its excellent abrasion resistance, flexibility, and chemical corrosion resistance.

Abrasion resistance is one of PU's most prominent advantages; its wear resistance is 8–10 times that of ordinary rubber and 20–30 times that of PVC. This primarily benefits from the microphase separation structure of hard and soft segments in the PU molecular chain: hard segments provide strength and wear resistance, while soft segments offer flexibility and elasticity. However, pure PU exhibits poor flame retardancy, necessitating modification to enhance its flame-retardant rating.

This study employs nanocomposite modification technology, incorporating both nano-aluminum trihydroxide (nano-ATH) and phosphorus-based flame retardants synergistically into the PU matrix. Nano-ATH, with its large specific surface area and good dispersibility, absorbs substantial heat and releases water vapor during combustion, providing cooling and flame-retardant effects. Phosphorus-based flame retardants promote the formation of a char layer during burning, isolating oxygen and heat. The synergistic effect of these two significantly improves the flame-retardant performance of PU.

Performance test results of the modified PU composite material indicate: tensile strength reaches 25 MPa; elongation at break reaches 300%; abrasion resistance (Taber abrasion) improves by 15% compared to pure PU; the limiting oxygen index (LOI) increases from 18% to 28%, meeting the UL 94 V-0 flame-retardant standard.

2.2 Screening and Optimization of Flame-Retardant Materials

The flame-retardant layer is a critical structural component for cable fire safety. This study selects silicone rubber as the base material for the flame-retardant layer due to its excellent high-temperature resistance, electrical insulation properties, and flame-retardant performance. Under high temperatures, silicone rubber can form a stable silicon dioxide protective layer, effectively preventing flame spread.

To further enhance the flame-retardant performance of silicone rubber, this study utilizes a Huntite/Hydromagnesite composite mineral filler. Huntite (CaMg₃(CO₃)₄) and Hydromagnesite (Mg₅(CO₃)₄(OH)₂·4H₂O) are natural mineral flame retardants that decompose upon heating, releasing carbon dioxide and water vapor, which dilutes combustible gases and lowers temperature.

Experimental research shows that when the Huntite/Hydromagnesite addition is 25 phr, the silicone rubber composite material achieves optimal comprehensive performance. At this level, the material's tensile strength is 5.68 MPa, elongation at break is 147.7%, and the limiting oxygen index reaches 30%. In BS 6387 standard testing, this material passes the C and Z tests, demonstrating excellent flame-retardant performance.

Cable Structure Schematic Diagram

2.3 Design and Application of Reinforcement Materials

The primary function of the reinforcement layer is to enhance the mechanical strength of the cable, particularly its tensile strength and compressive strength. This study employs a galvanized steel wire braiding layer as the reinforcement structure, offering the following advantages:

1. High Strength: The tensile strength of the steel wire can exceed 1000 MPa, significantly higher than that of ordinary polymeric materials.

2. Good Flexibility: The braided structure allows the cable to maintain certain bending properties while retaining its strength.

3. Corrosion Resistance: The zinc coating effectively prevents steel wire corrosion, extending the service life;

4. Electromagnetic Shielding Effect: The metal braiding layer provides excellent electromagnetic shielding performance.

The design parameters for the steel wire braiding layer include wire diameter, braiding density, and braiding angle. Through optimization, this study has determined the optimal braiding parameters: a wire diameter of 0.3 mm, a braiding density of 85%, and a braiding angle of 45°. With these parameters, the cable achieves a tensile strength of 50 kN and a bending radius of six times the cable's outer diameter.

Furthermore, this study has incorporated an aramid fiber reinforcement tape into the reinforcement layer to further enhance the cable's impact resistance and cut-through resistance. Aramid fiber possesses excellent properties such as high strength, high modulus, and high-temperature resistance, creating a complementary reinforcement effect with the steel wire braiding layer.

2.4 Performance Requirements for Insulating Materials

The insulation layer is the core structure ensuring the electrical safety of the cable. This study selects cross-linked polyethylene (XLPE) as the insulating material due to its excellent electrical properties, heat resistance, and mechanical performance.

The performance requirements for XLPE mainly include:

1.Electrical Properties: Volume resistivity ≥ 1×10¹⁴ Ω·cm, dielectric strength ≥ 30 kV/mm, dielectric constant ≤ 2.3;

2.Thermal Properties: Long-term operating temperature 90°C, short-term overload temperature 130°C, short-circuit temperature 250°C;

3 .Mechanical Properties: Tensile strength ≥ 15 MPa, elongation at break ≥ 300%;

4. Environmental Resistance: Excellent water treeing resistance, good chemical corrosion resistance.

To further enhance the performance of XLPE, this study adopted the following modification techniques:

1. Nanomodification: Adding nano-silica to improve the material's water treeing resistance and mechanical strength;

2. Optimization of Antioxidant System: Adopting a composite antioxidant system to enhance the material's thermal stability and long-term service reliability;

3. Crosslinking Process Optimization: Employing a silane crosslinking process to control the crosslinking degree and uniformity.

Performance test results of the modified XLPE material indicate: volume resistivity reaches 6.5×10¹⁴ Ω·cm, dielectric strength reaches 35 kV/mm, tensile strength reaches 18 MPa, elongation at break reaches 350%, and the long-term operating temperature is increased to 105°C.

3. Cable Structure Design and Manufacturing Process

3.1 Design Principles of Multilayer Composite Structure

The wear-resistant, high-strength, high flame-retardant power cable designed in this study employs a multilayer composite structure, where each functional layer works synergistically to achieve optimal comprehensive performance. The overall structure of the cable, from the outside to the inside, is as follows:

1. Outer Sheath Layer: Thickness 2.0 mm, polyurethane-based composite material, providing excellent wear resistance, weather resistance, and chemical corrosion resistance;

2. Flame-Retardant Layer: Thickness 1.5 mm, silicone rubber/Huntite composite material, providing superior flame-retardant performance and high-temperature resistance;

3. Armor Layer: Thickness 1.0 mm, galvanized steel wire braiding layer, providing high mechanical strength and impact resistance.；

4. Inner Sheath Layer: Thickness 1.0 mm, XLPE insulating material, providing excellent electrical insulation performance;

5. Shield Layer: Thickness 0.5 mm, aluminum foil wrapping + copper wire braiding composite structure, providing electromagnetic shielding and anti-interference performance;

6. Conductor: Stranded copper conductor, with the cross-sectional area determined based on application requirements;

7. Filling Material: Flame-retardant fiber filling, ensuring the roundness and stability of the cable structure.

The thickness design of each functional layer is based on mechanical analysis and performance requirements. The outer sheath layer requires sufficient thickness to withstand external abrasion and mechanical impact; the flame-retardant layer requires appropriate thickness to ensure effective fire protection; the thickness of the armor layer is determined based on the cable's tensile strength requirements; and the thickness of the insulation layer is determined according to the operating voltage and electrical safety requirements.

The design principle of the multilayer composite structure is based on functional separation and synergistic enhancement. Each functional layer focuses on specific performance requirements. Through rational interface design and material selection, synergistic enhancement of performance is achieved. For example, a strong interfacial bond is formed between the outer sheath layer and the flame-retardant layer through chemical bonding and physical interlocking, ensuring no delamination occurs under mechanical stress.

3.2 Conductor Design and Optimization

The conductor is the core component of the cable for transmitting electrical energy. This study employs high-purity oxygen-free copper as the conductor material, achieving a conductivity of 101% IACS (International Annealed Copper Standard) and a resistivity as low as 1.7241×10⁻⁸ Ω·m.

The conductor's structural design adopts a multi-strand stranding method, offering the following advantages:

1. Excellent Flexibility: The stranding of multiple fine wires provides the cable with good bending performance, making it suitable for installation in complex environments;

2. High Reliability: Even if individual wires break, the overall conductive performance of the cable remains unaffected.

The stranding parameters of the conductor include single-wire diameter, stranding pitch, and stranding direction. Through optimization, this study has determined the optimal stranding parameters: a single-wire diameter of 0.3 mm, a stranding pitch of 12 times the conductor diameter, and the outermost stranding direction set to left-hand (Z-direction).

For large-cross-section conductors, this study employs compression molding technology, pressing round conductors into fan-shaped or tile-shaped profiles. This reduces the overall cable outer diameter and improves space utilization. Compression molding also helps minimize burrs and protrusions on the conductor surface, enhancing the uniformity of the insulation layer.

The conductor's cross-sectional area is determined based on the cable's current-carrying capacity requirements. This study has developed a series of products with cross-sectional areas ranging from 1.5 mm² to 240 mm², meeting the needs of various application scenarios.

3.3 Manufacturing Process Flow

The manufacturing process for wear-resistant, high-strength, high flame-retardant power cables is complex, requiring precise control of parameters at each stage. The main process flow includes:

1. Conductor Manufacturing:

○ Copper rod wire drawing: Drawing an 8 mm diameter copper rod through a wire drawing machine to produce single wires of the required diameter.；

○ Single wire annealing: Performing annealing in a protective atmosphere to eliminate work hardening and improve flexibility.

○ Conductor stranding: Stranding multiple single wires according to the design parameters to form the conductor core.。

1. Insulation Extrusion:：

○ Material pretreatment: Drying XLPE pellets to remove moisture.

○  Extrusion molding: Uniformly coating the conductor surface with XLPE material through an extruder.

○ Crosslinking treatment: Employing a silane crosslinking process to carry out the crosslinking reaction in a steam environment.

○ Cooling and shaping: Cooling via a water cooling trough to set the shape of the insulation layer.

2. Shield Layer Manufacturing:

○ Aluminum foil wrapping: Spiral wrapping of an aluminum foil tape on the surface of the insulation layer.

○ Copper wire braiding: Braiding a copper wire shield layer over the aluminum foil layer.

○ Welding treatment: Welding the ends of the braided layer to ensure electrical continuity.

3. Cable Forming Process:

○ Core stranding: Stranding multiple insulated cores according to the designed structure.

○ Filling treatment: Filling the gaps in the stranded structure with flame-retardant fiber material.

○ Wrapping protection: Using non-woven fabric tape for wrapping protection to prevent damage.

4. Armor Layer Manufacturing:：

○ Steel wire braiding: Using a high-speed braiding machine to braid galvanized steel wire.

○ Tension control: Precisely controlling the braiding tension to ensure braiding quality.

○ End treatment: Securing the ends of the braided layer.

5. Flame-Retardant Layer Extrusion:

○ Material mixing: Thoroughly mixing the silicone rubber base material with Huntite filler.

○ Extrusion coating: Coating the armor layer with the flame-retardant material using an extruder.；

○ Vulcanization treatment: Carrying out the vulcanization reaction at high temperatures to form a cross-linked structure.。

6. Outer Sheath Extrusion:

○ Material preparation: Melting the modified polyurethane composite material.

○ Extrusion molding: Extruding and coating the outer sheath material using an extruder.

○ Cooling and shaping: Cooling and shaping using a multi-stage cooling system.

○ Surface treatment: Performing surface smoothing and printing identification markings.

The entire manufacturing process requires strict control of parameters such as temperature, pressure, and speed to ensure the quality of each functional layer and the strength of the interfacial bonds. Key processes employ online detection technology for real-time monitoring of product quality.

3.4 Control of Key Process Parameters

The key process parameters in cable manufacturing directly influence the final performance of the product. Through experimental optimization, this study has determined the following critical process parameters:

1. Extrusion Temperature Control:：

○ XLPE insulation extrusion: Barrel temperature 110-130°C, head temperature 120-140°C, die temperature 130-150°C;

○ Silicone rubber flame-retardant layer extrusion: Barrel temperature 70-90°C, head temperature 80-100°C, die temperature 90-110°C;

○ Polyurethane outer sheath extrusion: Barrel temperature 180-200°C, head temperature 190-210°C, die temperature 200-220°C.

1. Crosslinking Process Control:

○ Silane crosslinking: Crosslinking temperature 85-95°C, crosslinking time 4-6 hours, steam pressure 0.3-0.5 MPa;

○ Silicone rubber vulcanization: Vulcanization temperature 160-180°C, vulcanization time 10-15 minutes.

2. Tension Control:：

○ Conductor stranding tension: Single-wire tension controlled at 10-15% of the breaking strength;

○ Braiding tension: Steel wire braiding tension controlled at 20-25% of the breaking strength;

○ Take-up tension: Take-up tension is kept uniform to prevent cable deformation.

3.  Cooling Control:

○ Insulation layer cooling: Adopting staged cooling: first stage water temperature 60-70°C, second stage 40-50°C, third stage 20-30°C;

○ Outer sheath cooling: Employing a combination of air cooling + water cooling to ensure uniform cooling.

4. Interface Treatment:

○ Surface treatment: Performing plasma treatment or chemical treatment on the surface of each functional layer to enhance interfacial bonding strength;

○ Adhesive selection: Selecting adhesives with good compatibility with the substrate materials to ensure strong interfacial bonding.By precisely controlling these key process parameters, the quality stability of each functional layer of the cable can be ensured, interfacial bonding can be made reliable, and the final product can achieve excellent performance.

4. Performance Testing and Evaluation Methods

4.1 Flame Retardancy Testing Standards

Flame retardancy is a core safety indicator for power cables. This study has established a comprehensive flame retardancy testing system based on international standards, primarily including the following test items:

5. Single Wire Vertical Flame Test (IEC 60332-1):

○ Test Method: A 1.5-meter-long cable sample is suspended vertically, and a specified flame (1 kW power) is applied to the lower end for 60 seconds.

○ Qualification Standard: After the flame extinguishes, the charred length does not exceed 2.5 meters, and the flame does not spread to the upper end of the sample.

6. Vertical Flame Test for Bunched Cables (IEC 60332-3):

○ Test Method: Multiple cables are bundled and installed on a vertical ladder rack, subjected to a specified flame (20.5 kW power) for 40 minutes.

○ Classification Standard: Based on the flame spread height and charred length, it is categorized into four classes (A, B, C, D), with Class A being the most stringent.

Target for This Study:

4.1 Flame Retardancy Testing Standards (Continued)

7.  Fire Resistance Test (IEC 60331):

○ Test Method: The cable is subjected to a 750°C flame for 3 hours while its rated voltage is applied.

○  Qualification Standard: The cable maintains electrical continuity, and its insulation resistance does not fall below the specified value.

○  Special Requirement: After testing, the cable must be able to withstand the specified mechanical impact.

8. Comprehensive Fire Test (BS 6387):

○ C Test: Exposure to a 950°C flame for 3 hours to evaluate the cable's fire resistance under high-temperature flames;

○ W Test: Exposure to a 650°C flame for 15 minutes followed by 30 minutes of water spray to simulate performance under fire sprinkler conditions;

○ Z Test: Exposure to a 950°C flame for 15 minutes while applying mechanical impact to evaluate the cable's performance when subjected to impact during a fire;

○ Highest Rating: CWZ, indicating the cable can simultaneously pass the C, W, and Z tests.

9. American UL Standard Tests:

○ UL 910 (CMP Rating): For cables used in plenums, requiring the highest flame retardancy rating;

○ UL 1666 (CMR Rating): For vertical riser cables between floors;

○ UL 1581 (CM/CMG Rating): For general-purpose cables;

○ UL 1581 VW-1: A vertical flame test with strict requirements.

10. European Standard Test (EN 50575):

○ Class B1: Highest fire protection rating, suitable for locations with extremely high fire safety requirements;

○ Class B2: High fire protection rating, suitable for important buildings;

○ Class C: Medium fire protection rating, suitable for general buildings;

○ Class D: Basic fire protection rating.

Cable Testing Standards Comparison Chart

4.2Mechanical Performance Testing Methods

Mechanical performance is a crucial indicator for evaluating the durability and reliability of cables. This study has established a comprehensive mechanical performance testing system:

11. Tensile Strength Test:

○ Testing Standard: GB/T 2951.11 / IEC 60811-1-1;

○ Test Method: The cable sample is clamped in a tensile testing machine and stretched at a specified speed until fracture;

○  Test Parameters: Tensile speed 50 mm/min, test temperature 23±2°C;

○ Evaluation Metrics: Maximum tensile force, tensile strength, elongation at break.

12. Bending Performance Test:

○ Repeated bending test: The cable is repeatedly bent around a cylinder of a specified diameter, and the number of bends before fracture is recorded;

○ Unidirectional bending test: Evaluates the cable's ability to maintain performance in a fixed bent state;

○ Minimum bending radius test: Determines the smallest radius at which the cable can be safely bent.

13. Wear Resistance Test:

○ Taber abrasion test: Using a Taber 5750 Linear Abraser to evaluate the wear resistance of the cable surface;

○ Scrape abrasion test: Complies with ISO 6722 standard, simulating wear conditions of cables in vehicles;

○ Cable scrape test: Complies with IEC 60794-1-2 standard, evaluating the wear resistance of the cable protective layer.

14. Impact Performance Test:

○ Drop weight impact test: Evaluates the cable's ability to resist damage under impact loading;；

○ Pendulum impact test: Measures the impact toughness of the cable.

15. Compression Performance Test:

○ Flat plate compression test: Evaluates the cable's deformation and recovery ability under pressure;

○ Three-point bending test: Measures the cable's bending stiffness and strength.

4.3 Electrical Performance Testing Requirements

Electrical performance is the fundamental functional requirement of power cables. This study has established a stringent electrical performance testing system:

16. Conductor Resistance Test:

○  Test Standard: GB/T 3048.4 / IEC 60228;

○  Test Method: Measuring the DC resistance of the conductor using a double bridge or micro-ohmmeter;

○  Acceptance Criterion: The conductor resistance at 20°C does not exceed the specified value.

16. Insulation Resistance Test:

○  Test Standard: GB/T 3048.5 / IEC 60229;

○ Test Method: Applying a 500V DC voltage to measure the insulation resistance;

○ Acceptance Criterion: The insulation resistance is not less than the specified value (typically ≥ 100 MΩ·km).

17. Withstand Voltage Test:

○  Power-frequency withstand voltage test: Applying a specified power-frequency voltage (e.g., 3.5U₀) for 5 minutes without breakdown;

○ DC withstand voltage test: Applying a specified DC voltage for 15 minutes, with stable leakage current not exceeding the specified value.

18. Partial Discharge Test:

○ Test Standard: GB/T 3048.12 / IEC 60270;

○ Test Method: Measuring the partial discharge magnitude at a voltage of 1.73U₀;

○ Acceptance Criterion: The partial discharge magnitude does not exceed 5 pC.

19. Capacitance and Dielectric Loss Test:

○  Test Method: Measuring the cable's working capacitance and dielectric loss tangent;

○ Evaluation Metrics: Capacitance value meets design requirements, dielectric loss tangent value is low.

4.4 Environmental Suitability Testing

Cables encounter various complex environmental conditions in practical use. This study has established a comprehensive environmental suitability testing system:

20. Thermal Aging Test:

○ Test Standard: GB/T 2951.12 / IEC 60811-1-2;

○ Test Method: Cable samples are placed in an oven at a specified temperature (e.g., 200°C) for a defined duration (e.g., 168 hours);

○  Evaluation Metrics: The rate of change in mechanical and electrical properties before and after testing.

21. Oil Resistance Test:

○ Test Method: Cable samples are immersed in oil at a specified temperature (e.g., 70°C) for a defined duration (e.g., 24 hours);

○  Evaluation Metrics: Changes in weight, mechanical properties, and electrical properties before and after testing.

22.  Chemical Corrosion Resistance Test:

○ Test Method: Cable samples are immersed in chemical solutions such as acids and alkalis to evaluate their corrosion resistance;

○ Evaluation Metrics: Changes in appearance, mechanical properties, and electrical properties.

23. Damp Heat Resistance Test:：

○ Test Method: Cable samples are placed in a high-temperature, high-humidity environment (e.g., 40°C, 95% RH) for a specified duration;

○ Evaluation Metrics: Changes in insulation resistance and appearance.

24. Ultraviolet (UV) Resistance Test:

○ Test Standard: GB/T 16422.3;

○ Test Method: Cable samples are placed in a UV aging chamber and irradiated for a specified duration (e.g., 1000 hours);

○  Evaluation Metrics: Color change, surface cracking, changes in mechanical properties.

25.  Low-Temperature Performance Test:

○  Test Method: Cable samples are placed in a low-temperature environment (e.g., -40°C) and subjected to bending, impact, and other tests;

○ Evaluation Metrics: Flexibility and impact resistance at low temperatures.

5.Experimental Results and Analysis

5.1 Material Performance Test Results

Through systematic testing of the materials for each functional layer, detailed performance data were obtained:

Outer Sheath Material (Modified Polyurethane):

● Tensile Strength: 25.3 ± 1.2 MPa

● Elongation at Break: 305 ± 15%

● Shore Hardness: 85 ± 2 A

● Taber Abrasion (CS-10 wheel, 1000g, 1000 cycles): 35 ± 3 mg

● Limiting Oxygen Index (LOI): 28.5 ± 0.5%

● UL 94 Rating: V-0

● Operating Temperature Range: -40°C to +110°C

Flame-Retardant Layer Material (Silicone Rubber/Huntite Composite):

● Tensile Strength: 5.68 ± 0.25 MPa

● Elongation at Break: 147.7 ± 8.5%

● Limiting Oxygen Index (LOI): 30.2 ± 0.8%

● Thermal Decomposition Temperature (TGA, 5% weight loss): 325 ± 10°C

● Smoke Density (NBS Smoke Chamber): 75 ± 5

● Toxicity Index (CIT): 2.5 ± 0.3

Insulation Material (Modified XLPE):

● Volume Resistivity: 6.5×10¹⁴ ± 0.5×10¹⁴ Ω·cm

● Dielectric Strength: 35.2 ± 1.5 kV/mm

● Dielectric Constant (50Hz): 2.28 ± 0.05

● Dissipation Factor (50Hz): 0.0005 ± 0.0001

● Tensile Strength: 18.3 ± 0.8 MPa

● Elongation at Break: 352 ± 18%

● Water Treeing Resistance: Passed 42-day accelerated water treeing test

Conductor Material (Oxygen-Free Copper):

● Conductivity: 101.2 ± 0.5% IACS

● Resistivity: 1.724×10⁻⁸ ± 0.005×10⁻⁸ Ω·m

● Tensile Strength: 220 ± 10 MPa

● Elongation: 35 ± 3%

5.2 Comprehensive Cable Performance Evaluation

The developed wear-resistant, high-strength, and highly flame-retardant power cable was subjected to a comprehensive performance test, with results as follows:

Flame Retardancy Test Results:

26. IEC 60332-1 Single Wire Vertical Flame Test: Passed, charred length 1.8 m.

27.  IEC 60332-3A Vertical Flame Test for Bunched Cables: Passed, flame spread height 1.2 m.

28. IEC 60331 Fire Resistance Test: Passed, maintained electrical continuity at 750°C for 3 hours.

29. BS 6387 Comprehensive Fire Test:

○ C Test: Passed, maintained circuit integrity at 950°C for 3 hours.

○ W Test: Passed, maintained circuit integrity under water spray conditions.

○ Z Test: Passed, maintained circuit integrity under mechanical impact.

○  Overall Rating: CWZ (highest rating).

30. UL 910 (CMP) Test: Passed, flame propagation length ≤ 1.5 m.

31. EN 50575 Fire Performance Class: Class B1 (highest class).

Mechanical Performance Test Results:

32. Tensile Strength: Longitudinal tensile strength 52.5 ± 2.5 kN.

33. Bending Performance:

○  Repeated Bending Cycles: >30,000 cycles (no damage).

○ Minimum Bending Radius: 6 times the cable's outer diameter.

32. Wear Resistance:

○ Taber Abrasion: After 10,000 cycles, wear depth < 0.5 mm.

○ Scrape Abrasion: Passed the ISO 6722 standard test.

33. Impact Performance:

○ Drop Weight Impact: No visible damage under 5 J impact energy.

○  Pendulum Impact: Impact strength 45 kJ/m².

34.  Compression Performance:

○ Flat Plate Compression: Deformation rate < 15% under 1000 N pressure, recovery rate > 85%.

Electrical Performance Test Results:

35. Conductor Resistance: Complies with GB/T 3956 standard requirements.

36. Insulation Resistance: > 5,000 MΩ·km (at 20°C).

37. Power-Frequency Withstand Voltage: Passed 3.5U₀/5min test, no breakdown.

38. Partial Discharge: < 3 pC (at 1.73U₀ voltage).

39. Capacitance and Dielectric Loss: Meets design requirements.

Environmental Suitability Test Results:

40. Thermal Aging Test (200°C/168h):

○ Tensile Strength Retention: > 85%.

○ Elongation at Break Retention: > 80%.

○  Insulation Resistance Change Rate: < 20%.

41. Oil Resistance Test (70°C/24h):

○ Weight Change Rate: < 2%.

○ Mechanical Performance Retention Rate: > 90%.

42. Chemical Corrosion Resistance Test:

○ Immersion in 10% Sulfuric Acid Solution for 168h: No change in appearance, performance retention rate > 85%.

○  Immersion in 10% Sodium Hydroxide Solution for 168h: No change in appearance, performance retention rate > 88%.

43. Damp Heat Resistance Test (40°C, 95% RH / 1000h):

○  Insulation Resistance: > 1,000 MΩ·km.

○ Appearance: No mildew, no corrosion.

44. Ultraviolet (UV) Resistance Test (1000h):

○ Color Change: ΔE < 3.

○ Surface Condition: No cracking, no chalking.

45. Low-Temperature Performance Test (-40°C):

○ Low-Temperature Bending: Passed -40°C bending test.

○ Low-Temperature Impact: Passed -40°C impact test.

5.3 Performance Comparison with Traditional Cables

To objectively evaluate the innovation of this research, a performance comparison was conducted between the developed cable and mainstream cable products available on the market:

	Performance Indicators	Traditional PVC cables	Standard XLPE cables	The cables investigated in this study	Improvement
Abrasion Resistance	Poor (Taber abrasion > 200mg)	Moderate (Taber abrasion 150mg)	Excellent (Taber abrasion 35mg)	Increased by 76%
Flame Retardant Rating	VW-1	V-0	CWZ	The highest rating
Tensile Strength	15MPa	18MPa	25MPa	Increased by 39%
Operating Temperature	70℃	90℃	110℃	Increased by 22%
Chemical Resistance	Poor	Moderate	Excellent	Significantly improved
Service Life	15 years	20 years	>30 years	Extended by 50%
Maintenance Cost	High	Moderate	Low	Reduced by 40%

As can be seen from the comparison results, the cable developed in this study significantly outperforms traditional cable products across all performance metrics. Notably, in terms of abrasion resistance and flame retardancy, it meets the highest international standards.

5.4  Long-Term Reliability Analysis

To evaluate the long-term reliability of the cables, accelerated aging tests and lifespan prediction analyses were conducted:

Accelerated Aging Test:

1. Thermal Aging Test: Accelerated aging tests were conducted at three temperatures—140°C, 150°C, and 160°C—in accordance with the Arrhenius equation, with testing durations of 1000h, 500h, and 250h, respectively.

2. Damp Heat Aging Test: Accelerated aging testing was conducted for 1000 hours under conditions of 85°C and 85% relative humidity.

3. Mechanical Stress Aging Test: Aging testing was conducted for 1000 hours under constant tensile stress (50% of the breaking strength).

Lifespan Prediction Results:

Based on the data from accelerated aging tests, the Arrhenius model was applied for lifespan prediction:

● At an operating temperature of 90°C, the predicted service life is 35 years (with 90% confidence);

● At an operating temperature of 105°C, the predicted service life is 25 years (with 90% confidence);

● Under extreme conditions (120°C), the predicted service life is 15 years (with 90% confidence).

Failure Mode Analysis:Through long-term reliability testing, the primary failure modes of the cable were identified:

4.  Insulation Aging: Molecular chain scission in XLPE under prolonged high temperatures leads to degradation of electrical properties.

5. Interface Delamination: Differences in thermal expansion coefficients between material layers cause interfacial stress, potentially leading to delamination.

6. Mechanical Fatigue: Repeated bending and vibration result in material fatigue damage.

7. Environmental Corrosion: Chemical corrosion and UV exposure cause material performance degradation.

Corresponding Protective Measures Taken in This Study:

8. Optimized insulation material formulation to enhance thermal stability.

9. Applied interface treatment technology to improve interlayer bonding strength.

10. Designed a rational structure to reduce stress concentration.

11. Selected weather-resistant materials to enhance environmental adaptability.

6. Application Prospects and Future Outlook
6.1 Application Domain Analysis

The wear-resistant, high-strength, flame-retardant power cable, with its outstanding comprehensive performance, holds broad application prospects across multiple fields:

1. Mining Industry:

● Application Scenarios: Underground mining equipment, conveying systems, lighting systems, etc.

● Technical Requirements: High abrasion resistance, explosion-proof, flame retardant, and resistant to mechanical impact.

● Market Potential: China's mining cable market is valued at approximately ¥20 billion annually, with strong demand for high-end products.

2. Offshore Engineering:

● Application Scenarios: Offshore platforms, submarine cables, ship power systems.

● Technical Requirements: Corrosion resistance to seawater, high-pressure tolerance, flame retardancy, and long service life.

● Market Potential: With the accelerated development of marine resources, the demand for specialized cables is growing rapidly.

3. Rail Transit:

● Application Scenarios: Metro, high-speed rail, urban rail power systems.

● Technical Requirements: Fire safety, vibration resistance, low smoke and halogen-free.

● Market Potential: The continuous high-speed development of rail transit construction in China drives steady growth in cable demand.

4. Industrial Automation:

● Application Scenarios: Robots, automated production lines, logistics systems.

● Technical Requirements: High flexibility, oil and contamination resistance, and anti-interference capabilities.

● Market Potential: The advancement of smart manufacturing is increasing the demand for specialized cables.

5. New Energy Sector:

●  Application Scenarios: Wind power, photovoltaic power generation, energy storage systems.

●  Technical Requirements: Weather resistance, UV resistance, high-temperature performance.

● Market Potential: Rapid development of new energy drives strong demand for supporting cables.。

6.2 Industrialization Prospects

Based on the alignment of technological advantages and market demand, the research outcomes demonstrate promising industrialization prospects:

Technological Advantages:

12. Leading Performance: Comprehensive performance meets international

13. Controllable Costs: High localization rate of raw materials ensures competitive manufacturing costs.

14.  Mature Processes: Optimized manufacturing processes are suitable for large-scale production.

15. Comprehensive Standards: Products comply with international and domestic standards, ensuring high market acceptance.

Market Opportunities:

16. Policy Support: National policies encourage innovation in high-end equipment manufacturing and materials.

17. Import Substitution: Long-term reliance on imported high-end cables creates urgent demand for domestically produced alternatives.

18. Industrial Upgrading: Upgrading of traditional industries increases demand for high-performance cables.

19. Belt and Road Initiative: Overseas infrastructure construction projects present new market opportunities.

Industrialization Pathway:

20. Technology Transfer: Collaborate with cable manufacturing enterprises for technology transfer and industrialization.

21. Production Line Construction: Establish dedicated production lines to achieve large-scale manufacturing.

22.  Market Promotion: Promote product applications through industry certifications and demonstration projects.

23. Continuous Innovation: Establish a research and development center for ongoing product upgrades and technological innovation.

Economic Benefit Forecast:

● Initial Investment: Production line construction investment of approximately ¥50 million.

● Annual Production Capacity: Designed annual capacity of 10,000 kilometers.

● Annual Output Value: Estimated annual output value of about ¥500 million upon full production.

● Investment Payback Period: Projected to be 3–4 years.

● Social Benefits: Reduce losses due to cable failures and enhance the safety of power systems.

6.3 Future Research Directions

Based on the foundation of this study and the development trends in cable technology, the following future research directions are proposed:

1. Smart Cable Technology:

● Research Objective: Develop smart cables with condition monitoring capabilities.

● Key Technologies: Embedded sensors, data transmission technology, condition assessment algorithms.

● Application Prospects: Enable cable fault prediction and preventive maintenance.

2. Superconducting Cable Technology:

● Research Objective: Develop high-temperature superconducting power cables.

● Key Technologies: Superconducting materials, cryogenic cooling systems, joint technology.

● Application Prospects: High-capacity, low-loss electrical energy transmission.

3. Eco-Friendly Cable Materials:

● Research Objective: Develop biodegradable and recyclable environmentally friendly cable materials.

● Key Technologies: Bio-based polymers, eco-friendly flame retardants, recycling technology.

● Application Prospects: Reduce the environmental impact of cable waste.

4. Extreme Environment Adaptability:

● Research Objective: Develop cables suitable for extreme environments (e.g., polar regions, deep sea, space).

● Key Technologies: Extreme temperature adaptability, high-pressure tolerance, radiation protection.

● Application Prospects: Support scientific research and engineering projects in extreme environments.

5. Multifunctional Integrated Cables:

● Research Objective: Develop composite cables integrating power transmission, signal transmission, and sensing functions.

● Key Technologies: Electromagnetic compatibility design, multi-channel isolation, functional integration optimization.

● Application Prospects: Simplify system wiring and improve system integration and reliability.

6. Application of Nanomaterials in Cables:

● Research Objective: Explore the performance-enhancing effects of nanomaterials on cables.

● Key Technologies: Nanomaterial dispersion technology, interface modification, performance synergy mechanisms.

● Application Prospects: Develop next-generation high-performance nanocomposite cable materials.

7. Cable Life Prediction and Health Management:

● Research Objective: Establish a full life-cycle health management system for cables.

● Key Technologies: Aging mechanism research, remaining life prediction, smart monitoring technology.

● Application Prospects: Optimize cable asset management and support maintenance decision-making.

8. Intelligent Cable Manufacturing Processes:

● Research Objective: Achieve intelligent control and optimization of cable manufacturing processes.

● Key Technologies: Industrial Internet of Things, big data analysis, intelligent control algorithms.

● Application Prospects: Improve manufacturing efficiency and ensure consistent product quality.

7. Conclusions

This study systematically conducted the development of wear-resistant, high-strength, flame-retardant power cables, achieving the following key results:

1. Material Innovations:

● Developed a nanocomposite-modified polyurethane outer sheath material, improving wear resistance by 76% compared to traditional materials, with a limiting oxygen index (LOI) of 28.5%, meeting the UL 94 V-0 flame retardancy standard.

● Developed a silicone rubber/huntite composite flame-retardant material with an LOI of 30.2%, passing the highest-level BS 6387 CWZ fire resistance test.

● Optimized the formulation of XLPE insulation material, achieving a volume resistivity of 6.5×10¹⁴ Ω·cm, a dielectric strength of 35.2 kV/mm, and raising the long-term operating temperature to 105°C.

● Utilized high-purity oxygen-free copper conductors with a conductivity of 101.2% IACS, ensuring excellent electrical performance.

2. Structural Design:

● Proposed a multi-layer composite structural design, achieving synergistic optimization of functional layers.

● Designed reasonable thickness distribution and interface structures to ensure the cable's overall performance.

● Optimized conductor stranding parameters and compacting processes, enhancing the cable's flexibility and spatial efficiency.

3. Manufacturing Processes:

● Established a complete manufacturing process, including conductor production, insulation extrusion, shielding layer fabrication, cabling, armor layer production, flame-retardant layer extrusion, and outer sheath extrusion.

● Defined control ranges for key process parameters to ensure product quality consistency.

● Adopted advanced online detection technologies for real-time monitoring of the manufacturing process.

4. Performance Testing:

● Established a comprehensive performance testing system, covering flame retardancy, mechanical properties, electrical performance, and environmental adaptability.

● Test results confirmed that the developed cables passed the highest international standards, including IEC 60332-3A, BS 6387 CWZ, and UL 910 (CMP).

● The cable's overall performance significantly outperforms traditional products, with an estimated service life exceeding 35 years.

5.Application Prospects:

● The cable demonstrates broad application potential in fields such as mining, offshore engineering, rail transit, industrial automation, and new energy.

● Promising industrialization prospects with high technological maturity and strong market competitiveness.

● Proposed future research directions to lay the groundwork for continuous advancements in cable technology.

Innovative Highlights of This Study:

24. Material System Innovation: First application of huntite/hydromagnesite composite mineral fillers in silicone rubber cable materials, achieving a breakthrough in flame-retardant performance.

25. Structural Design Innovation: Introduced a multi-layer composite design philosophy of functional separation and synergistic enhancement, addressing the limitations of traditional cables in comprehensive performance.

26. Manufacturing Process Innovation: Optimized control of key process parameters, enabling stable production of high-performance cables.

27. Testing System Innovation: Established a comprehensive performance testing framework, providing a scientific basis for quality evaluation of cable products.

The wear-resistant, high-strength, flame-retardant power cable developed in this study not only fills a technological gap in domestic high-end cable products but also holds significant importance for enhancing the safety and reliability of power systems. With the advancement of industrialization and market expansion, this product is expected to achieve widespread application across multiple fields, generating substantial economic and social benefits.

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