Pacific HVdc Intertie The Pacific HVdc intertie (PDCI) connects the BPA system at The Dalles, Oregon, on the Columbia River with a partnership of utilities in southern California at Sylmar in the San Fernando Valley in the northern part of Los Angeles (see Figure 3). This intertie has had a long and complex history that was detailed in an April 2007 article in IEEE Power & Energy Magazine. In the article, dramatic changes to the Sylmar converter station were described: the old mercury arc converters were eliminated, and thyristor converters from 1989 were replaced with more modern equipment in 2004. Currently, the northern station, called Celilo, is undergoing a similar renovation with totally new converters replacing the converters that were installed in 1989. Additional work is expected at Sylmar in the next few years to replace filters and control equipment. The current renovation at Celilo is of some interest and is described in detail. figure 2. A typical modern HVdc converter station. (Photo courtesy of Siemens.) Originally constructed in the late 1960s, the PCDI has undergone numerous changes over its history. First Celilo dc-ac Converter Station Oregon Pacific HVdc Intertie Transmission Line California Nevada Owens Gorge Transmission Line Los Angeles Owens River Aqueduct System Owens Gorge Power Plant Califonia Aqueduct (State Water Project) Sylmar dc-ac Converter Station Mead Switching Station McCullough/ Marketplace Switching Station Intermountain Generation Station Utah Southern Transmission System Crystal Switching Station Hoover Navajo Dam Power Plant Generating Eldorado Generating Station Station Mohave Generating Station Castaic Power Plant Palo Vender Devers Line 2 Los Angeles Area System Devers Switching Station Arizona Palo Verde Generating Station Los Angeles Area Generating Facilities: Valley Generating Station figure 3. A map showing ac and dc lines into the Los Angeles basin. march/april 2016 ieee power & energy magazine 35