The production of electricity is done far away from cities at electricity generation centers. These power plants depend upon water, thermal energy, wind or geothermal power. Here, electricity is produced usually at 11 KV (voltage), 50 Hertz (frequency).
The system by which electricity is transmitted from such centers to the consumer can be divided into two parts:
By using step up transformer, voltage is converted for transmission of electricity at the production centre. At the electricity generation centre, by using step up transformer voltage is converted from 11 kV to 132 kV. Then, the electricity reaches at low power station through high tension wire. At lower power station it again converted up to 3.3 kV by using step down transformer. In this way by using step down transformer electricity reaches at home at the village of 220 V and 50 Hz.
Hertz (Hz) is unit of frequency. The number of cycles completed by AC in one second is called as its frequency. A frequency of 50 Hertz means, AC completes 50 cycles per second. That means AC flows in one direction 50 times while in the other again 50 times in electrical wires, bulbs and other electrical appliances. This means that a bulb lights up 100 times and goes out 100 times in a second. But due to the lack of perception of such small intervals of time, a bulb appears to glow constantly.
If the voltage of a transformer is increased then current flow reduces in the same proportion. Thus, by using step up transformers we change electricity to higher voltage and reduce the current flow. By transmitting this low current we reduce the losses occurred during the transmission.
The distribution system is the arrangement which provides power from substation to the consumer. It involves feeder distributors, sub distributors and service men. Normally, there are two types of distribution systems: (i) Tree system (ii) Ring system. These days mostly ring system is used.