Electric power transmission

Transmission lines in Lund, Sweden

BC Hydro transmission towers and lines in Coquitlam, British Columbia.

Transmission line in Taiwan

Electric power transmission is the transmitting of electricity to places where it will be used. Specifically, it is the bulk transfer of electrical power from the power plant to substations near populated areas. Electric power distribution is the delivery from the substation to the consumers. Due to the large amount of power and long distances, transmission normally takes place at high voltage (110 kV or above).

Electricity is usually transmitted over long distance through overhead power transmission lines. Underground power transmission is used only in densely populated areas (such as large cities) because of the high cost of installation and maintenance and because the power losses increase dramatically compared with overhead transmission unless superconductors and cryogenic technology are used.

A power transmission system is sometimes referred to colloquially as a "grid"; however, for reasons of economy, the network is rarely a true grid. Redundant paths and lines are provided so that power can be routed from any power plant to any load center, through a variety of routes, based on the economics of the transmission path and the cost of power.

Electric Power Transmission Media

Five-hundred kilovolt (500 kV) Three-phase electric power Transmission Lines at Grand Coulee Dam. Four circuits are shown. Two additional circuits are obscured by trees on the far right. The entire 7079 MW nameplate generation capacity of the dam is accommodated by these six circuits.
A diagram of an electric power system. The transmission system is in blue.
New York City streets in 1890. Besides telegraph lines, multiple electric lines were required for each class of device requiring different voltages.
Westinghouse alternating current polyphase generators on display at the 1893 World's Fair in Chicago, part of their "Tesla Poly-phase System". Such polyphase innovations revolutionized transmission.
A transmission substation decreases the voltage of incoming electricity, allowing it to connect from long-distance high-voltage transmission, to local lower voltage distribution. It also reroutes power to other transmission lines that serve local markets. This is the PacifiCorp Hale Substation, Orem, Utah, US.
The synchronous grids of Europe
A high-power electrical transmission tower, 230 kV, double-circuit, also double-bundled
A 115 kV subtransmission line in the Philippines, along with 20 kV distribution lines and a street light, all mounted on a wood subtransmission pole
115 kV H-frame transmission tower
Electrical grid without a transformer