The Celilo Converter Station, built in 1970 and owned and operated by the Bonneville Power Administration, is the northern terminus of the Pacific DC Intertie, near The Dalles, Oregon, in the United States.
Celilo Converter Station Wikipedia
The Celilo Converter Station was originally configured with six groups of six-pulse mercury arc valves with a blocking voltage of 133 kV each (for a total of ±400 kV) and a maximum current of 2,000 amperes.
In 1985 two six-pulse valve groups of thyristors were added to increase the voltage to 500 kV per pole for a total differential voltage of 1,000 kV.
In 1989 two new 1,100 ampere, 500 kV thyristor converters were added in parallel with the two existing converters, giving a total transmission power of 3,100 Megawatts (3,100 A at ±500 kV).
Until September 2001, the Celilo Converter Station was partially open to the public and included displays describing the history of DC transmission and the Pacific Intertie, but security concerns have closed this facility to the public.
In 2004, the mercury arc valves groups were replaced with light-triggered thyristor groups to eliminate the environmental risks of mercury and to reduce the maintenance costs of the obsolete mercury arc valves.
In January 2016, the new Celilo Converter Station is planned to go into service after replacing the entire terminal with a new two-converter terminal rated +/- 560kV 3410A (3800MW), while the Oregon-part of the transmission line is being upgraded to +/-520kV and 3,220MW.
There was also a DC test facility for testing high voltage equipment nearby (now abandoned, soon to be demolished). At the end of the 1960s, a test transmission line for 1,333 kV was erected at 45.482792°N 120.814097°W / 45.482792; -120.814097 (1333 kV DC Line) to test equipment for this voltage, which was intended for a planned HVDC from Celilo Converter Station to Hoover Dam. This line was never built.