Overview: Cables and wires are one of the most important parts of any electrical system. These are the things which carry and transmit electrical power from the source to the point of consumption. Even though any cable shoulders a very critical duty it has a fairly simple construction and all the components inside the cable have a specific duty too! An obvious question that can pop in one’s mind would be about the construction of the cable and what are these cables exactly made up of? Cable is made up of several different materials, metals as well as non metals. Insulation, sheath, armour, binders and finally the most important part of any cable i.e. a conductor. Cables and wires are involved in transfer of electric power from power plants to consumer or from source to the power grid and then to the end consumer. Cables play a very critical part in the overall transmission of the electricity from its point of generation to the end consumer as if these cables are the veins and arteries of the electrical circulation system. As the technology has progressed in engineering sectors, so has it evolved in power generation and transmission sector. Inventions of newer materials have made it easier, safer and affordable to anyone and everyone to access modern cables. PVC materials in insulation and metallic elements in armour materials have been developed, which offer many advantages to the cable and affect its durability and life time. Conductors have changed too, with respect to the changes in technology. The construction of the cable and the way these conductors are arranged and placed inside the cable has been optimized to get maximum rigidity or flexibility, safety and relevant parameters. Stringent standards are set towards the manufacturing of modern day cables and so the manufacturers abide by them. One can easily understand the working if a cable if the one knows how the cable is able to conduct electricity and transport it around.
Conductors and conductance: Conductors in the cable are the ones which are responsible to conduct and transport electrical energy through the cables. This conductor lies at, what is called as the core of the cable. Metals like silver, gold and brass are also good conductors of electricity but then the cost at which these materials are available in the market is plain and simple exorbitant and surely these cannot be used to make products on a larger scale as that of a power cable or a connecting wire. Basis of any conductor can be realized only after knowing how conduction occurs in the first place. Electrical conductivity in metals occurs due to electrically charged particle movement in and around the metal. Electrons present in the outermost shell of an atom which are free to move, also known as valence electrons are the ones responsible for conducting electricity. These free electrons can move through the atomic structure that forms the metallic element and when subjected under the effect of an electric field, these electrons move inside the metal structure passing electric charge to other electrons as the move. Conductivity can be considered the strongest if there is least resistance. The conductors which have a single valance electron moving through the metal and which can cause a strong repelling force can be considered to have good conductivity. In that sense, Copper has a conductivity of 5.98×10^7 σ(S/m) at 20°C and resistivity of 1.68×10^8 p(Ω•m) at 20°C and Aluminium has conductivity of 3.5×10^7 σ(S/m) at 20°C and resistivity of 2.82×10^-8 p(Ω•m) at 20°C. These conductors can be included in the wires in stranded form or in solid forms but typically depends on the application at hand. Stranded wires have two or more wires wound concentrically to form a helix. These stranded wires are wound around the conductor core. Cables having stranded construction have a better flexibility than the solid construction. In comparison to stranded cables solid conductor cables have a solid single conductor where bare copper is used in majority cases.
Metals used in cable construction: Even though metals like silver or gold have better conductivity, sheer cost of those materials make them a worst candidate to be used as a conductor material. Copper and Aluminium are two of the most widely used metals in cable constructions due to numerous advantages and very good conductive properties. As mentioned earlier a conductor needs to have low resistance to effectively allow the flow of electricity, good ductile properties and the right amount of strength to be able to carry electric current efficiently. Copper and Aluminium is used widely in cable manufacturing as these metals are highly ductile and resistive to corrosion. Copper clad Aluminium cables can be another type of working cables. Copper clad Aluminium cables are made by bonding thick Copper layer over Aluminium core. Copper can be around 10% of the total volume of material in the cable. Buying cables which include Aluminium or Copper online can be easily done now days.
Copper and Aluminium conductors in cables: Focusing on Aluminium as a conductor material, it is the metal which is readily available in the and definitely cheaper than Copper. From the price point of view, Aluminium price is much more stable as compared to the copper. Copper prices tend to fluctuate frequently so does the cost of cable itself changes, inevitably. Aluminium has a difference in conductivity as compared to same sized Copper but on the other hand it is much lighter in weight. Due to these characteristic, it finds its way in larger cables and cables used in over head power distribution systems. When current passes through Aluminium it has a tendency to heats up . A film of oxide is formed on the surface which ultimately acts as a good insulator. Aluminium cables find applications in motors including squirrel cage and induction motors as well as in low and medium voltage underground cables.
As mentioned earlier Copper on the other hand has resisivity of around 1.68×10−8ρ (Ω•m) at 20 °C. Copper can easily qualify as the oldest metal used for making cables mainly due to its high conductivity. Apart from Silver, Copper has the best conductive capabilities. Impurities and production processes like hardening affect the conductivity of Copper but second to that, copper alloys are produced to increase the hardness quotient of the copper in applications where ductility is of less importance.
Due to the difference in conductivity more Aluminium is required if one wants to match the conductivity of a equal amount of Copper conductor, thus a larger insulation material is required to cover the cross section of the Aluminium cable. Copper cables can be thinner and fit into tight spots like in household applications as well as it can be easily jointed. Armour when added to a cable gives an extra layer of protection to it, thus an armoured Aluminium cable or an armoured Copper cable will be a logical choice when used in harsh operating conditions. Now shop for such cables online easily.
Apart from the proven advantages there are some drawbacks too! Copper cables can be expensive to make if the market rate of copper is on the high where as Aluminium cables can be prone to breakage if bent at too many places. Copper does not creep or loosen at the connecting points. Even though Aluminium and Copper have their own advantages and disadvantages both metals are extensively used to make cables and are chosen on the basis of many factors like application area, technical requirements, cost, overall sustainability and so on.
Applications of Aluminium and Copper cables: Copper cables can find application in residential applications where it is used extensively rather than Aluminium. Wires and cables used in electronic instruments and gadgets are also made up with Copper as a conductor. Due to high conductivity copper cables are used in electricity generation and distribution networks. Overhead transmission lines tend to use Aluminium cables due to its less weight and corresponding less cost. Apart from these transmission lines Aluminium cables can be used in applications where weight can be crucial factors for e.g. automobiles or aircrafts.