Editing Power engineering (section)

===Power engineering in the USA===
In 1936 the first commercial [[high-voltage direct current]] (HVDC) line using [[mercury-arc valve]]s was built between [[Schenectady, New York|Schenectady]] and [[Mechanicville, New York]]. HVDC had previously been achieved by installing direct current generators in series (a system known as the [[Thury system]]) although this suffered from serious reliability issues.<ref>{{cite web | url=http://www.ieee.org/organizations/pes/public/2005/may/peshistory.html | title=A Novel but Short-Lived Power Distribution System | date=2005-05-01 | publisher=IEEE | access-date=2008-05-25 | url-status=dead | archive-url=https://web.archive.org/web/20110524013821/http://www.ieee.org/organizations/pes/public/2005/may/peshistory.html | archive-date=2011-05-24 }}</ref> In 1957 [[Siemens]] demonstrated the first solid-state rectifier (solid-state rectifiers are now the standard for HVDC systems) however it was not until the early 1970s that this technology was used in commercial power systems.<ref>{{cite news | author=Gene Wolf | title=Electricity Through the Ages | url=http://tdworld.com/mag/power_electricity_ages/ | work=Transmission & Distribution World | date=2000-12-01 }}</ref> In 1959 Westinghouse demonstrated the first [[circuit breaker]] that used [[sulfur hexafluoride|SF<sub>6</sub>]] as the interrupting medium.<ref>{{cite news | author=John Tyner, Rick Bush and Mike Eby | title=A Fifty-Year Retrospective | url=http://tdworld.com/mag/power_fiftyyear_retrospective/ | work=Transmission & Distribution World | date=1999-11-01 }}</ref> SF<sub>6</sub> is a far superior [[dielectric]] to air and, in recent times, its use has been extended to produce far more compact switching equipment (known as [[switchgear]]) and [[transformer]]s.<ref>{{ cite web | url=http://www.abb.com/product/us/9AAC710047.aspx | publisher=ABB | title=Gas Insulated Switchgear | access-date=2008-05-25 }}</ref><ref>{{cite web | url=http://www.sayedsaad.com/Transformer/SF6_Transformer/sf6_transformer_main.htm | title=SF6 Transformer | first=Sayed | last=Amin | access-date=2008-05-25 | archive-url=https://web.archive.org/web/20080616053117/http://www.sayedsaad.com/Transformer/SF6_Transformer/sf6_transformer_main.htm | archive-date=2008-06-16 | url-status=dead }}</ref> Many important developments also came from extending innovations in the [[Information and communications technology|ICT]] field to the power engineering field. For example, the development of computers meant [[load flow study|load flow studies]] could be run more efficiently allowing for much better planning of power systems. Advances in information technology and telecommunication also allowed for much better remote control of the power system's switchgear and generators.