Page 529 - Basic Electrical Engineering

to reduce the cost of transmission. High-voltage transmission reduces the size
of transmission line conductors thereby reducing the weight of the
conducting material used. Since power is the product of voltage and current,

for the same power if voltage is increased, the magnitude of current will
decrease. For transmitting at this reduced current, the size of the line

conductors will reduce, and hence the cost gets reduced. The power house
wherefrom electricity is transmitted through transmission lines is called the

‘sending end’ whereas the other end of the transmission lines where the
electricity is received for use is called the ‘receiving end’. At the sending end

the voltage level is increased using step-up transformers before, connecting to
the transmission lines, while at the receiving end the voltage level is lowered
before the distribution of electricity for use. The voltage level is raised for

reducing the cost of transmission while it is again lowered before supplying
to consumers, for safety reasons. Consumers use electricity at 230 V or at 400

V.

Figure 6.1 Block diagramatic representation of a transformer

A device known as transformer which either raises or lowers the voltage
level of electrical power is always used at both the ends of the transmission

lines. When voltage is raised from lower level to higher level, the device used
is called a step-up transformer. When voltage is lowered from a high level to
a low level, the transformer used is called a step-down transformer.

The frequency of the alternating voltage on both sides of the transformer
will not change. Whatever the frequency of the input voltage is, the same will

be the frequency of the output voltage.
With this introduction, we may define a transformer as a device which

raises or lowers the voltage level of any electrical power input without