About Cables
Cables are as important to the electrical systems as veins for our body. As veins distribution in
our body supply blood,
cables supply electricity to the
electrical hardware and electronics
systems. Cables can be seen everywhere in different forms and sizes, as small as data cables
in mobiles to as large as
power cables in thermals. The role of cable as power carriers has
been diversified with the evolution of technology. No longer they are power carriers only,
they are now the backbone of data transmission system.
When we talk about cables, two things come to our mind. One is the large fiber or metallic
rope that is used for lifting and hauling. Other one is the conductor that carries electricity.
Both of them are equally important. Here in the following sections we are referring to the
later one i.e.
electric cables. Well they are simply called cables and here on we will use
only cable for electric cables.
Cable is not a single thing rather it is an assembly of insulated conductors and
protective materials. A wide range of cable types are found for different uses but
their primary duty is to conduct electricity only. The design and construction of
cables vary enormously to meet the diverse requirements.
History of Electrical Cables
Electrical cables have significantly evolved during the past one and half century.
Though they are very much the same despite some changes and improvements in their
design. A number of basic processes are still used in the manufacturing. The
demand of electrical cables seemed to have risen with Faraday's discovery of
the principle of the dynamo in 1831. Prior to that there was hardly any
means of producing electricity.
However the very first power distribution system used copper rods. It was
developed by Thomas Edison in 1882 in New York City. The copper rod, used
as conductor, was wrapped in jute and placed in rigid pipes filled with a
bituminous compound. Charles Goodyear patented vulcanized rubber in 1844,
but it was not applied for cable insulation until the 1880s. Rubber-insulated
cable was used in 1897 for Niagara galls power project for carrying
11,000 volts.
Uses of Cables
Electrical cables are used for the transmission, distribution and utilisation of
electrical power. Cables are the most practical means of conveying electrical
power to tools, appliances and machines of all types.
- Electrical cables are used in the home wiring system. They are used in the electrical and
electronics home appliances, such as television, electric iron, music systems. The
types and forms of cables used may differ from each other.
- Coaxial cables are used for transferring data from one device to another in computer systems.
- Cables are the primary means of connectivity in telephone industry.
Types of Cables
Electrical cables can be classified on a number of basis.
On the basis of Application
- Telephone Cables: Telephone cables carry messages back and forth along wires. They are
made up of multiple wires. Each wire is insulated and carries it's own specific separate
message. A telephone cable consists of thousands of wires, bound together by wrappings
of further insulation. Since these cables are laid underground or underwater, entire
cable is protected with an outer covering.
- Television Cables: Popularly called only cables, television cables are coaxial cables.
- Video Cables: A good video cable is rated by the clarity pf picture and sound it delivers.
The main function of video cables is to transfer a fully preserved signal from
one place to another. Several types of video cables working on different
technologies are available in the market today like DVI cables, HDMI cables, RF cables, etc.
- Computer Cables: Computer cables are coaxial cables made of copper conductors and good
dielectric materials. These cables connect various components of computers and
peripherals to each other.
- Medical Cables
- Industry Cables
- Power Cables: Power cables are used for supplying electricity from one place to
another. They can be classified according to the power they are capable of transferring.
Very high power cables, which can carry lacs of watts are used to transfer electricity
from thermal power to sub stations.
- Home Cables: These are basic electrical cables used for wiring in homes. Such cables have
a single copper or aluminum conductor covered with an insulating layer. Home cables are also
known as house wiring cables.
On the Basis of Construction
Cables Materials
Cables are made of conductors and insulating materials. Copper and aluminum are the most
commonly used metals as conductors in electrical cables.
- Copper: Due to the magnificent electrical conductivity, excellent ductility and
malleability, copper has been unchallenged as a conductor for all types of
insulated cables for more than 50-60 years. Apart from that copper has good
mechanical strength and shows excellent resistant to corrosion. Its conductivity
is largely affected by impurities and mechanical working.
- Aluminum: After copper aluminum is the most used metals for manufacturing electrical
cables. Like copper aluminum too has excellent conductivity, ductility and malleability.
Its advantage as conductor over copper is its light weight and low cost. The use of
aluminum as conductors came to fore only after 1950s when the price of copper soared.
- Other: However of all the metals, silver has the highest conductivity but due to its
very high cost it can't be used as general electrical cables. Gold too has very good
conductivity. Silver and gold conductors are used in highly sophisticated appliances
like computers.
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