The high voltages power from the generating station transmitted over long distances at a still high voltage to minimize the loss of energy in form heat in the line wires used for transmission. For a given electric power, the current become low at a high voltage* and therefore the loss of energy due to heating (I2Rt) in the line wires becomes less. Thus, the alternating voltage generated is first stepped up from 11 kV to 132 kV at the generating station (or called the grid substation) using the step-up transformer. It is then transmitted to the main.
At the main sub-station, the voltage is stepped down from 132 kV to 33 kV using the step down transformer and is then transmitted to the heavy industries and intermediate sub-station. At the intermediate sub-station, the voltage is stepped down from 33 kV to 11 kV using the step down transformer and it is transmitted to light industries and city substation. At the city sub-station, it is further stepped down from 11 kV to 220 V (Indian Standard Unit but varies with country) using the step down transformer to supply to the domestic consumers. And finally reaches to local homes.
