The main component of an electric power cable is its core. The conductor is the element that carries power from one point to another. This is why it is made of a highly conductible material. In most cases it is copper or aluminium. One of the longest ranging debates in the field is about copper Vs aluminium — which one works best!
Copper was the conductor used in the first power distribution system that was developed by Thomas Edison for the New York City. It was the favoured metal for almost all first experiments with electricity, such as telephone and telegraph. This is because it is one of the most conductible metals, second only to silver.
In fact, the conductivity of copper has increased as processing technology has given us a purer metal. In 1913, the International Annealed Copper Standard was adopted to compare copper’s conductivity against other metals.
Although aluminium joined the party a bit late, it soon became the conductor of choice because of its properties. The aluminium used as conductor in most electric power cables today is actually an alloy of aluminium. In fact, the alloy AA-8000 was actually developed to mirror some of the advantages of copper.
Now let us do a comparison of both conductors:
Conductivity: There is no doubt that copper has better conductivity than aluminium. In fact, aluminium has just 61%conductivity of copper. This makes copper a more efficient carrier of electricity.
Weight: Although aluminium has less conductivity than copper, it more than makes up for this in weight. In the end, we compensate for copper’s conductivity by simply increasing the weight and bringing it at par with copper. For half the weight we can get the same resistance.
Price: Another advantage of aluminium in electric power cables is its low cost. Aluminium is one of the most commonly found elements, where the occurrence of copper is not as abundant. With better technology copper prices have also fallen and we do see some designers switching back to copper. However, copper prices, because of their limited availability, often fluctuate wildly. This makes it unsuitable for long-term projects.
Properties: Copper alloys can usually give one 20-40% elongation. Aluminium, on the other hand, only gives us 18% elongation. However, some aluminium alloys, developed to increase elongation, do better. AA-8000, used in power circuits was developed to copy the properties of copper.
Diameter size: Because of its far higher ductility, we can get copper conductors with a smaller cross section. This property is further aided by copper’s lower susceptibility to problems arising out of electrical contact. This gives it multiple advantages. To begin with, we can have thinner cables that are easy to install.
The smaller cross-section of the copper means that copper wires are also less stiff, which further aids their installation. With copper we can also get very fine starred cables. While we can also achieve fine stranding in aluminium, it is never quite as fine-stranded as copper. The individual wires are also thinner in the case of copper. This is why the ‘extra fine stranded’ cables always contain copper conductor.
Cost of installation: In this case, both copper and aluminium have their advantages. Where weight is a consideration, as in the case of shipping, aluminium wins because of its lighter weight. Lighter aluminium core cables do not require heavy supports in elaborate projects like power grids. But where weight is not an issue, copper cables are often easier to install because these are more flexible.
Durability: Copper has better resistance to corrosion than aluminium. It is also better at handling stress. Aluminium also cracks when it is subjected to vibrations. This is a problem in power cables where electricity often makes the cables vibrate. Vibration is also a concern in motors and transformers.
Recently, a combination of copper aluminum has emerged as a viable solution. The electric power cables carrying both aluminium and copper wires combine the quality of both elements.
Electric power cables can have copper or aluminium conductors. While aluminium is cheaper and lighter, copper is more durable, flexible and has better ductility. It also has better conductivity than aluminium and is hence, used more frequently than aluminium.