Editing Electric power transmission (section)

== History ==
{{Main|History of electric power transmission}}
[[File:New York utility lines in 1890.jpg|thumb|New York City streets in 1890. Besides telegraph lines, multiple electric lines were required for each class of device requiring different voltages.]]

Commercial electric power was initially transmitted at the same voltage used by lighting and mechanical loads. This restricted the distance between generating plant and loads. In 1882, DC voltage could not easily be increased for long-distance transmission. Different classes of loads (for example, lighting, fixed motors, and traction/railway systems) required different voltages, and so used different generators and circuits.<ref name=hughes>{{cite book |url=https://books.google.com/books?id=g07Q9M4agp4C&q=westinghouse+%22universal+system%22&pg=PA122|pages=119–122|author=Thomas P. Hughes|title=Networks of Power: Electrification in Western Society, 1880–1930|publisher=Johns Hopkins University Press|location=Baltimore|isbn=0-8018-4614-5 |year=1993|author-link=Thomas P. Hughes}}</ref><ref name="guarnieri 7-1">{{Cite journal|last=Guarnieri|first=M.|year=2013|title=The Beginning of Electric Energy Transmission: Part One|journal=IEEE Industrial Electronics Magazine|volume=7|issue=1|pages=57–60|doi=10.1109/MIE.2012.2236484|s2cid=45909123}}</ref>

Thus, generators were sited near their loads, a practice that later became known as [[distributed generation]] using large numbers of small generators.<ref name=ncep1>{{cite web|url=https://www.energy.gov/sites/prod/files/oeprod/DocumentsandMedia/primer.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.energy.gov/sites/prod/files/oeprod/DocumentsandMedia/primer.pdf |archive-date=2022-10-09 |url-status=live|title=Electricity Transmission: A primer|publisher=National Council on Electricity Policy|access-date=September 17, 2019}}</ref>

Transmission of [[alternating current]] (AC) became possible after [[Lucien Gaulard]] and [[John Dixon Gibbs]] built what they called the secondary generator, an early [[transformer]] provided with 1:1 turn ratio and open magnetic circuit, in 1881.

The first long distance AC line was {{convert|34|km|abbr=off}} long, built for the 1884 International Exhibition of Electricity in [[Turin, Italy]]. It was powered by a 2&nbsp;kV, 130&nbsp;Hz [[Siemens & Halske]] alternator and featured several Gaulard transformers with primary windings connected in series, which fed incandescent lamps. The system proved the feasibility of AC electric power transmission over long distances.<ref name="guarnieri 7-1"/>

The first commercial AC distribution system entered service in 1885 in via dei Cerchi, [[Rome, Italy]], for public lighting. It was powered by two Siemens & Halske alternators rated 30&nbsp;hp (22&nbsp;kW), 2 kV at 120&nbsp;Hz and used 19&nbsp;km of cables and 200&nbsp;parallel-connected 2&nbsp;kV to 20&nbsp;V step-down transformers provided with a closed magnetic circuit, one for each lamp. A few months later it was followed by the first British AC system, serving [[Grosvenor Gallery]]. It also featured Siemens alternators and 2.4&nbsp;kV to 100&nbsp;V step-down transformers &ndash; one per user &ndash; with shunt-connected primaries.<ref name="guarnieri 7-2">{{Cite journal|last=Guarnieri|first=M.|year=2013|title=The Beginning of Electric Energy Transmission: Part Two|journal=IEEE Industrial Electronics Magazine|volume=7|issue=2|pages=52–59|doi=10.1109/MIE.2013.2256297|s2cid=42790906}}</ref>

Working to improve what he considered an impractical Gaulard-Gibbs design, electrical engineer [[William Stanley, Jr.]] developed the first practical series AC transformer in 1885.<ref name="edisontechcenter.org">{{cite web|url=http://edisontechcenter.org/GreatBarrington.html|title=Great Barrington Experiment|website=edisontechcenter.org}}</ref> Working with the support of [[George Westinghouse]], in 1886 he demonstrated a transformer-based AC lighting system in [[Great Barrington, Massachusetts]]. It was powered by a steam engine-driven 500&nbsp;V Siemens generator. Voltage was stepped down to 100&nbsp;volts using the Stanley transformer to power incandescent lamps at 23&nbsp;businesses over {{convert|4000|ft|m}}.<ref>{{cite web|url=https://ethw.org/William_Stanley|title=William Stanley – Engineering and Technology History Wiki|website=ethw.org|date=August 8, 2017 }}</ref> This practical demonstration of a transformer and alternating current lighting system led Westinghouse to begin installing AC systems later that year.<ref name="edisontechcenter.org"/>

In 1888 the first designs for an [[AC motor]] appeared. These were [[induction motor]]s running on [[polyphase system|polyphase]] current, independently invented by [[Galileo Ferraris]] and [[Nikola Tesla]]. Westinghouse licensed Tesla's design. Practical [[Three-phase electric power|three-phase]] motors were designed by [[Mikhail Dolivo-Dobrovolsky]] and [[Charles Eugene Lancelot Brown]].<ref name="books.google.com">[[Arnold Heertje]], Mark Perlman [https://books.google.com/books?id=qQMOPjUgWHsC&dq=tesla+motors+sparked+induction+motor&pg=PA138 Evolving Technology and Market Structure: Studies in Schumpeterian Economics], p. 138</ref> Widespread use of such motors were delayed many years by development problems and the scarcity of [[Polyphase system|polyphase power systems]] needed to power them.<ref>Carlson, W. Bernard (2013). ''Tesla: Inventor of the Electrical Age''. Princeton University Press. {{ISBN|1-4008-4655-2}}, p. 130</ref><ref>Jonnes, Jill (2004). ''Empires of Light: Edison, Tesla, Westinghouse, and the Race to Electrify the World''. Random House Trade Paperbacks. {{ISBN|978-0-375-75884-3}}, p. 161.</ref>

[[File:Tesla polyphase AC 500hp generator at 1893 exposition.jpg|thumb|right|Westinghouse alternating current [[polyphase system|polyphase]] generators on display at the 1893 [[World's Columbian Exposition|World's Fair in Chicago]], part of their Tesla Poly-phase System. Such polyphase innovations revolutionized transmission.]]

In the late 1880s and early 1890s smaller electric companies merged into larger corporations such as [[Ganz Works|Ganz]] and [[AEG (German company)|AEG]] in Europe and [[General Electric]] and [[Westinghouse Electric (1886)|Westinghouse Electric]] in the US. These companies developed AC systems, but the technical difference between direct and alternating current systems required a much longer technical merger.<ref name="Thomas Parke Hughes 1930, pages 120-121"/> Alternating current's economies of scale with large generating plants and long-distance transmission slowly added the ability to link all the loads. These included single phase AC systems, poly-phase AC systems, low voltage incandescent lighting, high-voltage arc lighting, and existing DC motors in factories and street cars. In what became a universal system, these technological differences were temporarily bridged via the [[rotary converter]]s and [[motor-generator]]s that allowed the legacy systems to connect to the AC grid.<ref name="Thomas Parke Hughes 1930, pages 120-121">{{cite book|first=Thomas |last=Parke Hughes|title=Networks of Power: Electrification in Western Society, 1880–1930|publisher=JHU Press|year=1993|pages=120–121}}</ref><ref name="Raghu Garud 2009, page 249">{{cite book|first1=Raghu|last1=Garud|first2=Arun|last2=Kumaraswamy|first3= Richard|last3= Langlois|title= Managing in the Modular Age: Architectures, Networks, and Organizations|url=https://archive.org/details/managingmodulara00garu|url-access=limited|publisher= John Wiley & Sons |year=2009| page=[https://archive.org/details/managingmodulara00garu/page/n256 249]|isbn=9781405141949}}</ref> These stopgaps were slowly replaced as older systems were retired or upgraded.

The first transmission of single-phase alternating current using high voltage came in Oregon in 1890 when power was delivered from a hydroelectric plant at [[Willamette Falls]] to the city of [[Portland, Oregon|Portland]] {{convert|14|mi|km}} down river.<ref>{{Cite journal|last=Argersinger|first=R.E.|date=1915|title=Electric Transmission of Power|journal=General Electric Review|volume=XVIII|page=454}}</ref> The first three-phase alternating current using high voltage took place in 1891 during the [[International Electro-Technical Exhibition – 1891|international electricity exhibition]] in [[Frankfurt]]. A 15 kV transmission line, approximately 175&nbsp;km long, connected [[Lauffen, Baden-Württemberg|Lauffen on the Neckar]] and Frankfurt.<ref name="guarnieri 7-2"/><ref>Kiessling F, Nefzger P, Nolasco JF, Kaintzyk U. (2003). ''Overhead power lines''. Springer, Berlin, Heidelberg, New York, p.&nbsp;5</ref>

Transmission voltages increased throughout the 20th&nbsp;century. By 1914, fifty-five transmission systems operating at more than 70 kV were in service. The highest voltage then used was 150&nbsp;kV.<ref>Bureau of Census data reprinted in Hughes, pp.&nbsp;282–283</ref> Interconnecting multiple generating plants over a wide area reduced costs. The most efficient plants could be used to supply varying loads during the day. Reliability was improved and capital costs were reduced, because stand-by generating capacity could be shared over many more customers and a wider area. Remote and low-cost sources of energy, such as [[Hydroelectricity|hydroelectric]] power or mine-mouth coal, could be exploited to further lower costs.<ref name="hughes" /><ref name="guarnieri 7-2"/>

The 20th&nbsp;century's rapid industrialization made electrical transmission lines and grids [[critical infrastructure]]. Interconnection of local generation plants and small distribution networks was spurred by [[World War I]], when large electrical generating plants were built by governments to power munitions factories.<ref>Hughes, pp.&nbsp;293–295</ref>{{clear left}}