The Pacific Northwest-Southwest Intertie project is a far-reaching program to provide strong electrical interconnections between the Pacific Northwest, primarily a region of hydroelectric generation, and the Pacific Southwest, primarily a region of steam generation. When completed, the Pacific Intertie will be the largest interregional tie in North America and the first to make use of parallel ac and dc circuits (Figure 1). The Pacific Intertie will ultimately consist of two 500-kv ac transmission lines from the Columbia River to the Southern California area, a 500-kv ac line from the Southern California area to the Lake Mead-Hoover Dam area of Southern Nevada, two 345-kv ac lines from the Lake Mead-Hoover Dam area to the Phoenix area, a ±375-kv dc transmission line from the Columbia River to Los Angeles, and a ±375-kv dc line also from the Columbia River to the Lake Mead-Hoover Dam area. The two high voltage direct current (HVDC) transmission lines are the first to be built in the United States, will have the highest voltage and greatest transmission capability of any HVDC system in the world today, will be the longest in length, 855 miles, and are the first lines which do not include significant lengths of underwater cable that dictate the use of HVDC transmission. The first of the two HVDC lines to go into operation will be the line to Los Angeles, the Celilo- Sylmar Line. The northern terminal, Celilo, is connected to the system of the Bonneville Power Administration; the Los Angeles terminal, Sylmar, is connected to the system of the Los Angeles Department of Water and Power (DWP). Financial partners of the DWP in the construction of this facility are the Southern California Edison Company and the municipalities of Burbank, Glendale and Pasadena.
