Editing Electric power distribution (section)

==Generation and transmission==
{{Main|Electric power transmission|Electricity generation}}
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File:Electricity grid simple- North America.svg|thumb|380px|right|Simplified diagram of AC [[electricity delivery]] from generation stations to consumers' [[service drop]].
rect 2 243 235 438   [[Power station]]
rect 276 317 412 556   [[Transformer]]
rect 412 121 781 400   [[Electric power transmission]]
rect 800 0 980 165   [[Transformer]]
desc bottom-left
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Electric power begins at a generating station, where the potential difference can be as high as 33,000 volts. AC is usually used. Users of large amounts of DC power such as some [[railway electrification system]]s, [[telephone exchange]]s and industrial processes such as [[aluminium]] smelting  use [[rectifier]]s to derive DC from the public AC supply, or may have their own generation systems.  [[HVDC|High-voltage DC]] can be advantageous for isolating alternating-current systems or controlling the quantity of electricity transmitted. For example, [[Hydro-Québec]] has a direct-current line which goes from the [[James Bay]] region to [[Boston]].<ref>{{Cite web|url=http://www.hydroquebec.com/learning/transport/grandes-distances.html|title=Extra-High-Voltage Transmission {{!}} 735 kV {{!}} Hydro-Québec|website=hydroquebec.com|access-date=2016-03-08}}</ref>

From the generating station it goes to the generating station's switchyard where a step-up transformer increases the voltage to a level suitable for transmission, from 44 kV to 765 kV. Once in the transmission system, electricity from each generating station is combined with electricity produced elsewhere. For alternating-current generators, all generating units connected to a common network must be [[Synchronization (alternating current)| synchronized]], operating at the same frequency within a small tolerance. Alternatively, disparate sources can be combined to serve a common load if some external power converter, such as a [[Frequency changer|rotating machine]] or a [[HVDC| direct current converter system]] is interposed. Electricity is consumed as soon as it is produced. It is transmitted at a very high speed, close to the [[speed of light]].