INTRODUCTION
Electric power is generated most economically at 14 to 25 kV. System loads such as motors, lights, etc., require a voltage source of 440, 220, and 110 V. Transformers are needed to change the voltage level. They are also used for these reasons:
1. To reduce transmission losses between power plants and the load by stepping up the voltage. (When the voltage is stepped up, the current will be stepped down. This results in reduction of transmission losses which are proportional to the square of the current.)
2. Reduction in the diameter of the transmission line (amount of copper or aluminum) due to a reduction in the current flowing in the line.
Typical transmission voltages are 13.2, 22, 66, 230, 345, and 500 kV. In general, the longer the distance, the higher the voltage used.