The main difference between copper & aluminum cables is the difference in their conductivity. The copper cable has more conductivity in comparison to the aluminum cable. We will discuss the differences between these types of cables in detail.
The Cooper & aluminum cables are two types of cables that have wide applications in an industrial installation. The main function of the cable is to carry the current from source to load. The cable has mainly the following parts.
- The conductor that carries the current
- The insulation that insulates the live conductors
- Inner sheath- Provides insulation to cable conducting cores
- Armour- Provides the mechanical strength to cable
- Outer sheath – Provide overall insulation to cable
The aluminum and copper cables have almost all the cable parts in common. The main difference is the core material. The aluminum cables have conductors made of aluminum. On the other hand, the copper cables have conductors made of copper.
Difference between Copper Cables & Aluminium Cables
The followings are the differences between copper and aluminum cables on the basis of cable sizing, cost, impedance cable weight, flexibility, and termination. We will discuss all those points in detail.
There is a big difference between the current-carrying capacity of the copper and aluminum cable. The copper cable of the same size as the aluminum cable can carry more current. The reason behind this is the different conductivity of copper and aluminum. The aluminum conductor has a lower current-carrying capacity and higher impedance than the equivalent copper conductor.
The conductivity of the copper and aluminum at 20°C is 5.98×10⁷ S/m & 3.5×10⁷ S/m respectively. Thus, the conductivity of the copper conductor is about 1.7 times the conductivity of the aluminum conductor.
Impedance of Cable
The conductivity of the aluminum cable is less than that of the copper cable. This clearly indicates that the resistance of the aluminum cable is more than that of copper cable. The impedance of copper cable with the current-carrying capacity of 135 amperes is 0.627 Ω/km. If we now select the same size of aluminum cable then its current-carrying capacity is 95 amperes and its impedance is 1.043 Ω/km.
Here, the point is why the user must be concerned about the cable impedance. When current flows in a conductor, the voltage drop and power loss occur throughout the length of the conductor. There will be more power loss(I2R) in aluminum cable in comparison to copper cable because of its higher resistance. Moreover, the voltage drop will be also more causing less voltage at the receiving end.
Difference between Copper & Aluminum Cable: Cable Flexibility
The aluminum cable is more flexible than the copper cable. However, the tensile strength and the fatigue resistance of the aluminum cable are less than the copper.
|Tensile strength||N/mm2||150 – 300||50 – 100|
|Fatigue resistance||N/mm2||60 – 115||20 – 45|
From the above table, it is clear that the tensile strength and the fatigue resistance of the copper conductor are better than the aluminum. These properties of copper allow using of small diameter stranded conductors in the cable. As a result, the copper cable is more flexible for the stranded conductor. Also, the high tensile strength of the copper cable can withstand high stress without wear and tear.
Oxidation of conductor
The aluminum conductors are prone to oxidize. The oxidization on the conductor and at the contact point increases the resistance. As a result, there is a chance of getting the cable heated up. On the other hand, the copper cable is not apt to oxidize.
Difference between Copper & Aluminum Cable: Weight of the Cable
The weight of the copper cable is more than the aluminum cable of the same size. This adds to the complexity of the installation. Moreover, the copper cable requires a bit more mechanical support over long distances to keep it in place. As a result, the installation cost of the copper cable is more. In a transmission line, Aluminium Conductor Steel Reinforced(ACSR) conductor. It reduces the weight of the transmission towers and their supports.
Coefficient of Thermal Expansion
The coefficient of thermal expansion of the materials shows the degree of change in its dimension with a rise in temperature. The copper cable has less coefficient of thermal expansion compared to aluminum cable. The coefficient of thermal expansion for aluminum is 35% greater than that of copper.
When connecting copper cable tin-plated copper lugs are crimped. This makes a solid copper-to-copper connection. However, when terminating aluminum cable, a special lug made of bi-metals ( Al-Cu) is used to have a minimum contact resistance inside the lug area.