Electrical transmission is the process of delivering generated electricity - usually over long distances - to the distribution grid located in populated areas. An important part of this process includes transformers which are used to increase voltage levels to make long distance transmission feasible.
The electrical transmission system is used in combination with power plants, distribution systems, and sub-stations to form what is known as the electrical grid. The grid is designed to meet all of society's electricity needs, and is what gets the electrical power from its beginning to its end use. Since power plants are most often located outside of densely populated areas, the transmission system must be fairly large.
Power lines or transmission lines, such as those in Figure 1, are used to transport electricity from place to place. This electricity is in the form of alternating current and begins at step-up transformers, and typically span a distance of 500 kilometers or less. There are 3 types of lines:
Above, it was mentioned that high voltage lines reduce this lost power. This fact can be explained by looking at the transmitted power, . As the voltage gets higher, the current must decrease in proportion because the power is remaining constant. For example, if the voltage is increased by a factor of 100, the current must decrease by a factor of 100 and the resulting power lost will be decreased by 1002 = 10000. However there is a limit, being that at extremely high voltages (2000 kV) the electricity begins to discharge resulting in high losses. In the transmission and distribution of electricity in the United States, the EIA estimates that about 6% of the electricity is lost.