History
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.
- In 1972, after the Sylmar earthquake, the static inverter station in Sylmar had to be reconstructed after damage to the largest part.
- In 1982, the power rating of the mercury arc valve rectifiers was raised by various improvements to 1,600 megawatts.
- In 1984, the transmission voltage was pushed to 500 kV and the transmission power was increased to 2,000 megawatts by adding one six-pulse thyristor valve group to each pole.
- In 1989, a further increase of the transmission power took place by a parallel switched thyristor static converter in Celilo and Sylmar.
- In 2004, Sylmar East station situated at 34°18′42″N 118°28′53″W / 34.31167°N 118.48139°W / 34.31167; -118.48139 (Sylmar East Converter Station - Pacific DC Intertie (south end)) was upgraded from 1,100 MW to 3,100 MW (rededicated as the Sylmar Converter Station in 2005). The controls and older converters, including the mercury arc valves, were completely replaced by a single pair of 3,100 MW 12-pulse converters built by ABB. In parallel with this project, the six-pulse mercury arc valves at the Celilo Converter Station were replaced with Siemens light-triggered thyristors (MARP replacement).
Read more about this topic: Pacific DC Intertie
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