electric power through power grid

Electric power transmission

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Transmission lines

Electric power transmission is the bulk transfer of electrical power (or more correctly energy), a process in the delivery of electricity to consumers. A power transmission networktypically connects power plants to multiple substations near a populated area. The wiring from substations to customers is referred to as Electricity distribution, following the historic business model separating the wholesale electricity transmission business from distributorswho deliver the electricity to the homes.^[1] Electric power transmission allows distant energy sources (such as hydroelectric power plants) to be connected to consumers in population centers, and may allow exploitation of low-grade fuel resources such as coal that would otherwise be too costly to transport to generating facilities.

Usually transmission lines use three phase alternating current (AC). Single phase AC current is sometimes used in a railway electrification system. High-voltage direct currentsystems are used for long distance transmission, or some undersea cables, or for connecting two different ac networks.

Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in transmission. Power is usually transmitted asalternating current through overhead power lines. Underground power transmission is used only in densely populated areas because of its higher cost of installation and maintenance when compared with overhead wires,and the difficulty of voltage control on long cables.

A power transmission network is referred to as a "grid". Multiple redundant lines between points on the network 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. Much analysis is done by transmission companies to determine the maximum reliable capacity of each line, which, due to system stability considerations, may be less than the physical or thermal limit of the line. Deregulation of electricity companies in many countries has led to renewed interest in reliable economic design of transmission networks. However, in some places the gaming of a deregulated energy system has led to disaster, such as that which occurred during the California electricity crisis of 2000 and 2001.^[2]

Diagram of an electrical system.

Contents [hide] 1 Overhead transmission 2 Underground transmission 3 History 4 Bulk power transmission 4.1 Grid input 4.2 Losses 4.3 Transmission grid exit 5 High-voltage direct current 6 Limitations 7 Control 7.1 Load balancing 7.2 Failure protection 8 Communications 9 Electricity market reform 10 Merchant transmission 11 Health concerns 12 Government policy 13 Special transmission 13.1 Grids for railways 13.2 Radio frequency power transmission 13.3 Superconducting cables 13.4 Single wire earth return 13.5 Wireless power transmission 14 Cyber-warfare 15 Records 16 See also 17 Notes 18 Further reading 19 External links