6. Transmission of Electricity
Electrical energy which is generated by alternators in a power station needs to be
transmitted to the users in towns and industrial areas by cables.
7. Problems in Electricity Transmission
Problems Ways to overcome Pictures
1. Cost of cables. a) Copper cables have low resistance but are high in cost.
b) Aluminium cables are usually used because they are light, have
low resistance and cost less.
2. Loss of power by the
a) By using thicker aluminium cables, resistance of the cables can
b) By using high voltage transmission, the current in the cables is
reduced and hence the power dissipated by the cables is
3. Charge leakage
between the cables
and the Earth.
a) To prevent charge leak, the aluminium cables are supported by
high metal pylons.
b) The metal support of the pylon is earthed so that it is safe to
workers and the public who come into contact with them.
8. National Grid Network
The National Grid Network is a system of cables which connects all the power stations and
sub-stations to all the consumers in a close-loop.
9. Step-up transformers are used to
increase the output voltage of a
generator. The high voltage is need
to reach the sub-stations in areas
such as towns, cities and industrial
In the sub-stations, step-down
transformers are used to reduce the
output voltage for light industrial
areas, offices and our homes.
10. Advantages of National Grid Network
Power supply will be uninterrupted even when
there is a breakdown in one power station. The
other power station will increase their
production to ensure continuous power supply.
The generation of electricity by each station
can be controlled and regulated according to
the demand pattern.
Cost of generation of electricity is reduced.