Introduction
Aluminium cables are widely used in homes, businesses, and industries. They are cheap and efficient at carrying heavy electrical loads. It’s vital to know these cables’ current-carrying capacity. It ensures safety, proper load management, and peak performance. This guide will detail various aluminium cable gauges. It will also advise on choosing the right cable for specific uses.
When choosing cables for electrical systems, the current-carrying capacity is key. This guide will help you understand the factors affecting cable performance. It focuses on PVC and XLPE-insulated low-voltage power cables (up to 0.6/1 kV). This reference will enhance your decision-making, whether you’re an engineer or project planner. It details cable characteristics for various environmental and operational conditions.
Understanding Current Carrying Capacity of Aluminium Cables
The current carrying capacity of aluminium cable is its safe limit for current. The current carrying capacity of aluminium cable varies with insulation type, conductor construction, and other factors. These include environmental conditions and installation specifics. Aluminium has lower conductivity than copper. So, at a given size, aluminium cables carry less current than copper ones. Aluminium’s electrical conductivity is about 58% of copper’s. So, aluminium cables can carry 42% less current than copper ones.
Copper cables may have higher conductivity. But, aluminium cables are cheaper. They can suit various uses if designed and installed with care.
Factors Influencing the Current Carrying Capacity of Aluminium Cables
Several variables impact the ability of current carrying capacity of aluminium cable to carry current effectively.
Type of insulation
Different insulation materials affect the heat tolerance of the cable. This, in turn, affects its current-carrying capacity. For instance:
XLPE (Cross-Linked Polyethylene) insulation allows higher temperatures, up to 90°C. PVC (Polyvinyl Chloride) insulation maxes out at around 70°C. So, XLPE-insulated cables generally support higher currents than PVC-insulated ones.
Environmental temperature
The ambient air and soil temperatures surrounding the cable influence its capacity. Elevated ambient temperatures decrease the capacity of a cable to release heat. This lowers its current-carrying capacity. For buried cables, soil temperature and resistivity are also critical.
Installation Configuration and Cable Grouping
Group installations: Cables installed in groups generate more heat than a single cable. This reduces the allowable current capacity due to limited airflow and heat dissipation.
Cable Spacing: Touching cables result in mutual heating, lowering the current-carrying limit.
Conductor construction: Solid or stranded conductors affect heat and flexibility, impacting current capacity.
Voltage type and level
AC vs. DC Voltage: AC may cause more losses at higher frequencies due to skin and proximity effects. Direct Current (DC) may allow higher current-carrying capacities for the same cable size, under certain conditions.
Voltage levels: Higher voltage uses often need different cable insulation and construction standards. These can affect current-carrying capacity.
Conductor Configuration (Armoured vs Unarmoured)
Armoured cables are more protected but may carry less current. The extra layers around the conductor can trap heat.
Soil Conditions (for Underground Cables)
For cables buried underground, soil resistivity and moisture content play significant roles. High-resistivity soils hinder heat dissipation, thus reducing the allowable current capacity. When sizing cables for underground work, consider the soil’s moisture, compactness, and thermal properties.
Key Electrical Characteristics of PVC and XLPE Insulated Cables
Cable insulation type, cross-section, and conductor material are important. They affect a cable’s current-carrying capacity. This section details PVC and XLPE-insulated cables, focusing on copper and aluminium conductors.
Cross-Section and Insulation Types
| Cross-Section (mm²) | PVC-Insulated (70°C Conductor Temp) – Cu | PVC-Insulated – Al | XLPE-Insulated (90°C Conductor Temp) – Cu | XLPE-Insulated – Al |
|---|---|---|---|---|
| 1.5 | 0.17 | – | 0.21 | – |
| 2.5 | 0.29 | – | 0.36 | – |
| 4 | 0.46 | – | 0.57 | – |
| 6 | 0.69 | – | 0.86 | – |
| 10 | 1.15 | – | 1.43 | – |
| 16 | 1.84 | – | 2.29 | – |
| 25 | 2.88 | 1.90 | 3.57 | 2.35 |
| 35 | 4.03 | 2.66 | 5.01 | 3.29 |
| 50 | 5.75 | 3.80 | 7.15 | 4.70 |
| 70 | 8.05 | 5.32 | 10.01 | 6.58 |
| 95 | 10.93 | 7.22 | 13.59 | 8.93 |
| 120 | 13.80 | 9.12 | 17.16 | 11.28 |
| 150 | 17.25 | 11.40 | 21.45 | 14.10 |
| 185 | 21.27 | 14.06 | 26.46 | 17.39 |
| 240 | 27.60 | 18.24 | 34.32 | 22.56 |
| 300 | 30.90 | 20.40 | 42.90 | 28.20 |
| 400 | 41.20 | 27.20 | 57.20 | 37.60 |
| 500 | 51.50 | 34.00 | 71.50 | 47.00 |
Note: Values represent the short-circuit current-carrying capacity in kA for a 1-second duration.
Current-Carrying Capacity for Cables Laying in the Air
When cables are laid in open air, their capacity is affected by insulation type, ambient temperature, and cable cross-section. Below is an overview of the capacity for PVC and XLPE-insulated cables (copper and aluminium) in open air at an ambient temperature of 30°C.
Nominal Current Capacities (Air-Laid)
| Cross-Section (mm²) | Copper (N2XY/N2X2Y/N2XH) | Copper (N2XCY/N2XC2Y) | Aluminum (NA2XY/NA2X2Y/NA2XH) | Aluminum (NA2XCY) |
|---|---|---|---|---|
| 1.5 | 33 | 24 | 26 | 25 |
| 2.5 | 43 | 32 | 34 | 33 |
| 4 | 57 | 42 | 44 | 43 |
| 6 | 72 | 53 | 56 | 54 |
| 10 | 99 | 74 | 77 | 75 |
| 16 | 131 | 98 | 102 | 100 |
| 25 | 177 | 133 | 138 | 136 |
| 35 | 217 | 162 | 170 | 165 |
| 50 | 265 | 197 | 207 | 201 |
| 70 | 336 | 250 | 263 | 255 |
| 95 | 415 | 308 | 325 | 314 |
| 120 | 485 | 359 | 380 | 364 |
| 150 | 557 | 412 | 437 | 416 |
| 185 | 646 | 475 | 507 | 480 |
| 240 | 774 | 564 | 604 | 565 |
| 300 | 901 | 649 | 697 | 643 |
| 400 | 1060 | 761 | 811 | 737 |
| 500 | 1252 | 866 | 940 | 807 |
Important: Ensure adequate spacing and ventilation for cables laid in air to maximize current capacity and reduce overheating risks.
Current-Carrying Capacity Chart for Aluminium Cables
The following tables provide a quick reference to the current-carrying capacities for various sizes of XLPE and PVC-insulated aluminium armoured cables, based on standardized conditions.
XLPE Insulated Aluminium Armoured Cable (1.1 kV)
| Cable Size (Sq. mm) | Single-Core (A) | Two-Core (A) | Three-Core (A) |
|---|---|---|---|
| 4 | 35 | 30 | 30 |
| 10 | 75 | 35 | 35 |
| 25 | 115 | 99 | 99 |
| 70 | 210 | 176 | 176 |
| 150 | 352 | 294 | 294 |
| 400 | 519 | 461 | 461 |
PVC Insulated Aluminium Armoured Cable (1.1 kV)
| Cable Size (Sq. mm) | Single-Core (A) | Two-Core (A) | Three-Core (A) |
|---|---|---|---|
| 4 | 27 | 27 | 26 |
| 10 | 47 | 47 | 40 |
| 25 | 78 | 65 | 59 |
| 70 | 153 | 150 | 130 |
| 150 | 202 | 185 | 155 |
| 300 | 280 | 275 | 240 |
The values in these tables represent the maximum current-carrying capacities for cables in air. For underground or enclosed installations, de-rating factors must be applied to account for reduced heat dissipation.
Calculating Current-Carrying Capacity with a De-Rating Factor
For optimal cable selection, apply a de-rating factor to the rated current capacity under specific conditions. This factor is crucial in apps with high temperatures, low airflow, or poor heat dissipation.
Below is a basic formula to calculate the adjusted current-carrying capacity:
Adjusted Capacity = Rated Capacity × De-Rating Factor
This calculation ensures the cable works well in real-world conditions. It boosts safety and durability.
Specifications of Common Aluminium Cable Gauges
The following are detailed specifications for various commonly used aluminium cable gauges. Each section gives insights into the load capacity, uses, and suitability of different aluminium cable sizes.
2.5 sq mm aluminium cable
| Specification | Details |
|---|---|
| Gauge | 2.5 Sq MM |
| Voltage Support | 250V |
| Current Capacity | 110A |
| Load Capacity | 500W |
| Suitable For | Low-power applications, such as LED lights, fans, and emergency lighting |
The 2.5 sq mm aluminium cable is suitable for low-power uses. It can power general residential lighting and low-wattage devices. It gives a reliable connection for devices with moderate power needs. It’s often used in household wiring for low-load circuits.
4.0 sq mm aluminium cable
| Specification | Details |
|---|---|
| Gauge | 4.0 Sq MM |
| Voltage Support | 250V |
| Current Capacity | 110A |
| Load Capacity | 800W |
| Suitable For | Moderate-power appliances, such as fans, small kitchen appliances, and lighting systems |
This cable gauge is ideal for moderate power applications. It is suitable for small to medium household appliances. It provides a safe connection for devices that demand up to 800W, and is commonly used for general-purpose wiring.
6.0 sq mm aluminium cable
| Specification | Details |
|---|---|
| Gauge | 6.0 Sq MM |
| Voltage Support | 250V |
| Current Capacity | 110A |
| Load Capacity | 1200W |
| Suitable For | Moderate to high-power appliances, such as refrigerators and washing machines |
The 6.0 sq mm cable is widely used in residential and commercial wiring where moderate to high power loads are present. It can power standard household devices. So, it is a common choice for electrical work in homes and offices.
8.0 sq mm aluminium cable
| Specification | Details |
|---|---|
| Gauge | 8.0 Sq MM |
| Voltage Support | 250V |
| Current Capacity | 110A |
| Load Capacity | 1800W |
| Suitable For | Heavy-load appliances, such as water heaters and large kitchen appliances |
An 8.0 sq mm cable is suitable for higher power applications and heavy-duty devices that require stable current delivery. This gauge meets the capacity for larger appliances and some industrial equipment.
10 sq mm aluminium cable
| Specification | Details |
|---|---|
| Gauge | 10 Sq MM |
| Voltage Support | 250V |
| Current Capacity | 110A |
| Load Capacity | 2500W |
| Suitable For | Heavy-duty applications, such as geysers, immersion heaters, and industrial equipment |
The 10 sq mm aluminium cable is ideal for heavy-duty electrical loads and is commonly used in commercial installations. This cable has a 2500W load capacity. It can handle demanding tasks and provide stable performance under high power.
Short-circuit current-carrying capacity
Cables’ short-circuit capacity depends on the insulation, conductor size, and installation environment. Here, we provide a look into the capacities for PVC and XLPE insulated cables.
Key Short-Circuit Parameters
PVC-insulated cables: The conductor temperature limit is set at 70°C, with a short-circuit temperature threshold of 160°C.
XLPE-Insulated Cables: The conductor temperature limit is set at 90°C, with a short-circuit temperature threshold of 250°C.
Conclusion
Current carrying capacity of aluminium cable varies. It depends on the material, insulation, environment, and installation. While aluminium is less conductive than copper, it is cheaper. With some adjustments, it can be a good alternative. By knowing the factors that affect current carrying capacity of aluminium cable and applying de-rating factors, we can safely use aluminium cables in many applications. Proper cable selection, installation, and maintenance are vital for current carrying capacity of aluminium cables. They ensure the safety, performance, and longevity of the electrical system.
Read more: Electrical cable sizing
