The Pacific DC Intertie (also called Path 65) is an electric power transmission line that transmits electricity from the Pacific Northwest to the Los Angeles area using high voltage direct current (HVDC). The line capacity is 3,100 megawatts, which is enough to serve two to three million Los Angeles households and is 48.7% of the Los Angeles Department of Water and Power (LADWP) electrical system's peak capacity.[1]
The intertie originates near the Columbia River at the Celilo Converter Station on Bonneville Power Administration's grid outside The Dalles, Oregon and is connected exclusively to the Sylmar Converter Station north of Los Angeles, which is owned by five utility companies and managed by LADWP. The Intertie is capable of transmitting power in either direction, but power on the Intertie flows mostly from north to south.
The idea of shipping hydroelectric power to Southern California had been proposed as early as the 1930s, but was opposed and scrapped. By 1961, U.S. 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 U.S. and ASEA of Sweden. Private California power companies opposed the project but their technical objections were rebutted by Uno Lamm of ASEA at the 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 U.S. $600,000 per day by use of electric power from projects on the Columbia River.
The Pacific Intertie takes advantage of differing power demand patterns between the northwestern and southwestern U.S. 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 power grid (states west of the Great Plains, including Colorado and New Mexico).[2]
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The Pacific Intertie consists of:[3]
Originally only mercury arc rectifiers were used as static inverter valves. The valves were series connected in three six-pulse valve bridges for each pole. The blocking voltage of the valves was 133 kV with a maximum current of 1,800 amperes, for a transmission rate of 1,440 megawatts with a symmetrical voltage of 400 kV against earth. The line is the DC part of a system of four 500 kV lines that connect the Pacific Northwest with the Southwest; the AC part is Path 15. This is one of two HVDC lines serving Los Angeles, the other is the Path 27.
More on the ABB website on Pacific HVDC Intertie:
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