They allow large centralized facilities such as hydroelectric dams, fossil fuel burning steam turbine plants, nuclear power plants, etc. run by large public and private utility organizations to produce large quantities of energy and then deliver it to distribution networks for delivery to retail customers for consumption.
The first large scale hydroelectric generators (engineered and installed under the technical oversight of Nikola Tesla) were installed at Niagara Falls and provided electricity to Buffalo City, New York[?] via power lines.
In a typical transmission grid, power plants use transformers to step the electric power up to high voltage alternating current (AC) for transmission over longer distances to a substation. This substation then steps the voltage down and supplies electricity to local power lines. It is necessary to transmit the electricity at high voltage to reduce the percentage loss of power over long distances: for a given cable the loss of power is proportional to the square of the current, while for a given transported power, this current is inversely proportional to the voltage.
It is argued by some that proximity to a high voltage power line presents a danger to the animals and humans living nearby. Some have claimed that electromagnetic radiation from high-tension lines cause elevated risk of certain types of cancer. Some studies have purported to identify the risk, while other studies have not.
Transmission lines can also be used to carry data: this is called power-line carrier, or PLC communication.
Transmission is a natural monopoly and there is a move in many countries to separately regulate transmission (see New Zealand Electricity Market). In the USA the Federal Energy Regulatory Commission (FERC[?]) has issued a Notice Of Proposed Rulemaking[?] (NOPR[?]) setting out a proposed Standard Market Design[?] (SMD[?]) that would see the establishment of Regional Transmission Operators[?] (RTOs[?]).