Introduction to trafo

1. ppt
Power stations, either fuel fired (thermal) or hydroelectric, are installed at a
point of location
generally hundreds and thousands kilometres away from the consumers, hence
a vast transmission lines
between generating point and consumer load centre is needed. It has been seen
in practice that generation
voltages at the power stations are in the range of 10 to 15 kV. It is a known fact
that when a power is
transmitted through a overhead line, some of the power it carries is dissipated
in the line conductor as
I2R in the form of heat, where ‘I’ is the current drawn by the line conductor and
‘R’ is the line resistance.
It is not economical to try to reduce the losses by solely decreasing the
conductor resistance, because
this would require a substantial increase in the cross-sectional area of
conductor, resulting a huge expenses
of copper conductor beyond means.

2. trafo
• At the beginning of the power transmission line near the generating station, the line voltage is
raised by
• a step-up transformer and at the end of the line the voltage is lowered by series of step-down
transformers
• to a value convenient for the consumers (400 V or nearer).
• The prime role in the present day power station is played by power transformers. The transformer
• is used to raise or lower the voltage in the supply network of the power system which serve to
transmit
• electric power over great distance and distribute it among consumers.
• Power transformers are notable for their high power capacities and operating voltages.
• Since electricity has to transmit over thousands of kilometres to the integrated power grid, the
• load centre and directly to numerous minor consumers, the system voltage has to be transformed
four to
• five times, hence the need to installed a large number of step-up and step-down transformers.
Also, it
• should be noted that each transformation stage operating at progressly lower voltage the total
capacity
• of power transformers is usually greater than that at the preceding stage. Therefore in any power
station
• the installed capacity of transformer is six or seven times the installed generating capacity. As an
example,
• Fig. 1.1 shows the layout of a transmission and distribution network.