Editing Pacific DC Intertie (section)

== Overview ==
The idea of sending [[hydroelectric]] power to [[Southern California]] had been proposed as early as the 1930s, but was opposed and scrapped.  By 1961, US president [[John F. Kennedy]] authorized a large public works project, using new [[high voltage direct current]] technology from [[Sweden]].  The project was undertaken as a close collaboration between [[General Electric]] of the US and [[ASEA]] of Sweden.  Private California power companies had opposed the project but their technical objections were rebutted by [[Uno Lamm]] of ASEA at an [[IEEE]] meeting in New York in 1963.  When completed in 1970 the combined AC and DC transmission system was estimated to save consumers in Los Angeles approximately US$600,000 per day by use of cheaper electric power from [[List of dams in the Columbia River watershed|dams on the Columbia River]].

One advantage of direct current over AC is that DC current penetrates the entire conductor as opposed to AC current which only penetrates to the [[skin depth]]. For the same conductor size, the effective resistance is greater with AC than DC, hence more power is lost as heat with AC. In general, the total cost for HVDC is less than an AC line if the line length is over 500–600 kilometers, and with advances in conversion technology, this distance has been reduced considerably. A DC line is also ideal for connecting two AC systems that are not synchronized with each other. HVDC lines can help stabilize a power grid against cascading blackouts since power flow through the line is controllable.

The Pacific Intertie takes advantage of differing power demand patterns between the northwestern and southwestern US. During winter, the northern region operates electrical heating devices while the southern portion uses relatively little electricity. In summer, the north uses little electricity while the south reaches peak demand due to air conditioning usage. Any time the Intertie demand lessens, the excess is distributed elsewhere on the [[Western Interconnection|western power grid]] (states west of the Great Plains, including [[Colorado]] and [[New Mexico]]).<ref>{{cite web
 |url         = http://www.ewh.ieee.org/r7/toronto/events/oct0303/prabha.ppt
 |format      = [[PowerPoint]]
 |title       = Power System Security in the New Industry Environment: Challenges and Solutions
 |author      = Prabha Kundur, Powertech Labs Inc.
 |page        = 17
 |publisher   = [[IEEE]]
 |date        = October 3, 2003
 |access-date  = 2006-09-11
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20060822101832/http://ewh.ieee.org/r7/toronto/events/oct0303/prabha.ppt
 |archive-date = August 22, 2006
}}</ref><gallery>
File:Img0259HVDC 500kV wire.JPG|The [[HVDC]] [[electric power transmission|power line]] in [[Los Angeles]] (shorter tower carrying two wires on the right). The power line crosses [[Interstate 5 in California|Interstate 5]] near the interchange with [[Interstate 210 and State Route 210 (California)|Interstate 210]] in [[Sylmar, Los Angeles|Sylmar]].
File:Path 65 P0002014.jpg|The Pacific DC Intertie along a service road paralleling [[U.S. Route 395 in California|U.S. Highway 395]].  Many of the towers of the Intertie are of this simple, slender design
File:Path 65 P0002019.jpg|The slender tower's base tapers down to a single point that is bolted to a concrete anchor
File:Path 65 P0002020.jpg|The slender tower is supported laterally by four [[guy-wire]]s
File:PacificIntertie.jpg|The Pacific Intertie outside of Benton, California
File:Pacific DC Intertie Towers near Fernley, Nevada.jpg|Pacific DC Intertie towers (left side) near [[Fernley, Nevada]]. The first few towers are self-supported. The towers on the far side use [[guy-wire]]s.
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