Cable selection is a critical step in electrical design and installation. Incorrect selection may lead to safety hazards (such as overheating or fire), excessive voltage drop, equipment damage, or low system efficiency. Below are the core factors to consider when selecting a cable:
1. Core Electrical Parameters
(1)Conductor Cross-Sectional Area:
Current Carrying Capacity: This is the most important parameter. The cable must be able to carry the maximum continuous operating current of the circuit without exceeding its allowable operating temperature. Refer to ampacity tables in relevant standards (such as IEC 60287, NEC, GB/T 16895.15).
Voltage Drop: Current flowing through the cable causes voltage drop. Excessive length or insufficient cross-section may lead to low voltage at the load end, affecting equipment operation (especially motor starting). Calculate the total voltage drop from the power source to the load, ensuring it is within the permissible range (typically ≤3% for lighting, ≤5% for power).
Short Circuit Withstand Capacity: The cable must withstand the maximum short-circuit current possible in the system without thermal damage before the protective device operates (thermal stability check). Larger cross-sectional areas have higher withstand capacity.
(2)Rated Voltage:
The cable’s rated voltage (e.g., 0.6/1kV, 8.7/15kV) must not be lower than the system’s nominal voltage (e.g., 380V, 10kV) and any possible maximum operating voltage. Consider system voltage fluctuations and overvoltage conditions.
(3)Conductor Material:
Copper: High conductivity (~58 MS/m), strong current carrying capability, good mechanical strength, excellent corrosion resistance, easy to handle joints, higher cost. Most commonly used.
Aluminum: Lower conductivity (~35 MS/m), requires larger cross-section to achieve the same ampacity, lighter weight, lower cost, but lower mechanical strength, prone to oxidation, requires special tools and antioxidant compound for joints. Often used for large cross-section overhead lines or specific applications.
2. Installation Environment & Conditions
(1)Installation Method:
In Air: Cable trays, ladders, ducts, conduits, surface mounted along walls, etc. Different heat dissipation conditions affect ampacity (derating required for dense installations).
Underground: Direct buried or ducted. Consider soil thermal resistivity, burial depth, proximity to other heat sources (e.g., steam pipelines). Soil moisture and corrosiveness affect sheath selection.
Underwater: Requires special waterproof structures (e.g., lead sheath, integrated water-blocking layer) and mechanical protection.
Special Installation: Vertical runs (consider self-weight), cable trenches/tunnels, etc.
(2)Ambient Temperature:
Ambient temperature directly affects cable heat dissipation. Standard ampacity tables are based on reference temperatures (e.g., 30°C in air, 20°C in soil). If actual temperature exceeds the reference, ampacity must be corrected (derated). Pay special attention in high-temperature environments (e.g., boiler rooms, tropical climates).
(3)Proximity to Other Cables:
Dense cable installations cause mutual heating and temperature rise. Multiple cables installed in parallel (especially with no spacing or in the same conduit) must be derated based on number, arrangement (touching / non-touching).
(4) Mechanical Stress:
Tensile Load: For vertical installations or long pulling distances, consider cable self-weight and pulling tension; choose cables with sufficient tensile strength (e.g., steel wire armoured).
Pressure/Impact: Direct buried cables must withstand surface traffic loads and excavation risks; tray-mounted cables may be compressed. Armouring (steel tape, steel wire) provides strong mechanical protection.
Bending Radius: During installation and turning, cable bending radius must not be smaller than the allowable minimum, to avoid damaging insulation and sheath.
(5)Environmental Hazards:
Chemical Corrosion: Chemical plants, wastewater plants, coastal salt fog areas require corrosion-resistant sheaths (e.g., PVC, LSZH, PE) and/or outer layers. Non-metallic armouring (e.g., glass fiber) may be needed.
Oil Contamination: Oil depots, machining workshops require oil-resistant sheaths (e.g., special PVC, CPE, CSP).
UV Exposure: Outdoor exposed cables require UV-resistant sheaths (e.g., black PE, special PVC).
Rodents/Termites: Some regions require rodent/termite-proof cables (sheaths with repellents, hard jackets, metal armouring).
Moisture/Submersion: Damp or submerged environments require good moisture/water-blocking structures (e.g., radial water-blocking, metal sheath).
Explosive Atmospheres: Must meet hazardous area explosion-proof requirements (e.g., flame-retardant, LSZH, mineral insulated cables).
3. Cable Structure & Material Selection
(1)Insulation Materials:
Cross-linked Polyethylene (XLPE): Excellent high-temperature performance (90°C), high ampacity, good dielectric properties, chemical resistance, good mechanical strength. Widely used for medium/low voltage power cables. First choice.
Polyvinyl Chloride (PVC): Low cost, mature process, good flame retardancy, lower operating temperature (70°C), brittle at low temperature, releases toxic halogen gases and dense smoke when burning. Still widely used but increasingly restricted.
Ethylene Propylene Rubber (EPR): Good flexibility, weather, ozone, chemical resistance, high operating temperature (90°C), used for mobile equipment, marine, mining cables. Higher cost.
Others: Silicone rubber (>180°C), mineral insulated (MI – copper conductor with magnesium oxide insulation, excellent fire performance) for special applications.
(2)Sheath Materials:
PVC: Good mechanical protection, flame-retardant, low cost, widely used. Contains halogen, toxic smoke when burning.
PE: Excellent moisture and chemical resistance, common for direct-buried cable outer sheaths. Poor flame retardancy.
Low Smoke Zero Halogen (LSZH / LS0H / LSF): Low smoke, non-toxic (no halogen acid gases), high light transmittance during burning. Mandatory in public spaces (subways, malls, hospitals, high-rise buildings).
Flame-retardant Polyolefin: Meets specific flame-retardant requirements.
Selection should consider environmental resistance (oil, weather, UV) and mechanical protection needs.
(3)Shielding Layers:
Conductor Shield: Required for medium/high voltage (>3.6/6kV) cables, equalizes conductor surface electric field.
Insulation Shield: Required for medium/high voltage cables, works with conductor shield for complete field control.
Metallic Shield/Armour: Provides EMC (anti-interference/reduces emissions) and/or short-circuit path (must be earthed) and mechanical protection. Common forms: copper tape, copper wire braid (shielding + short-circuit path), steel tape armour (mechanical protection), steel wire armour (tensile + mechanical protection), aluminium sheath (shielding + radial water-blocking + mechanical protection).
(4)Armouring Types:
Steel Wire Armoured (SWA): Excellent compressive and general tensile protection, for direct burial or mechanical protection needs.
Galvanised Wire Armoured (GWA): High tensile strength, for vertical runs, large spans, underwater installations.
Non-metallic Armour: Glass fiber tape, provides mechanical strength while being non-magnetic, lightweight, corrosion-resistant, for special requirements.
4. Safety & Regulatory Requirements
(1)Flame Retardancy:
Select cables meeting applicable flame-retardant standards (e.g., IEC 60332-1/3 for single/bunched flame retardancy, BS 6387 CWZ for fire resistance, GB/T 19666) based on fire risk and evacuation needs. Public and escape-difficult areas must use LSZH flame-retardant cables.
(2)Fire Resistance:
For critical circuits that must remain energized during fire (fire pumps, smoke fans, emergency lighting, alarms), use fire-resistant cables (e.g., MI cables, mica-taped organic insulated structures) tested to standards (e.g., BS 6387, IEC 60331, GB/T 19216).
(3)Halogen-Free & Low Smoke:
Mandatory in areas with high safety and equipment protection requirements (transport hubs, data centers, hospitals, large public buildings).
(4)Compliance with Standards & Certification:
Cables must comply with mandatory standards and certifications in the project location (e.g., CCC in China, CE in EU, BS in UK, UL in US).
5. Economics & Life Cycle Cost
Initial Investment Cost: Cable and accessories (joints, terminations) price.
Installation Cost: Varies with cable size, weight, flexibility, and ease of installation.
Operating Loss Cost: Conductor resistance causes I²R losses. Larger conductors cost more initially but reduce long-term losses.
Maintenance Cost: Reliable, durable cables have lower maintenance costs.
Service Life: High-quality cables in proper environments can last 30+ years. Evaluate comprehensively to avoid choosing low-spec or poor-quality cables based only on initial cost.
6. Other Considerations
Phase Sequence & Marking: For multi-core cables or phase-separated installations, ensure correct phase sequence and color coding (per local standards).
Earthing & Equipotential Bonding: Metallic shields and armour must be reliably earthed (usually at both ends) for safety and shielding performance.
Reserve Margin: Consider possible future load growth or routing changes, increase cross-section or reserve spare circuits if needed.
Compatibility: Cable accessories (lugs, joints, terminations) must match cable type, voltage, and conductor size.
Supplier Qualification & Quality: Choose reputable manufacturers with stable quality.
For optimal performance and reliability, selecting the right cable goes hand in hand with choosing high-quality materials. At ONE WORLD, we provide a comprehensive range of wire and cable raw materials — including insulation compounds, sheathing materials, tapes, fillers, and yarns — tailored to meet diverse specifications and standards, supporting safe and efficient cable design and installation.
Post time: Aug-15-2025