Editing Pacific DC Intertie (section)

==History==
[[File:Sylmar Converter Station.jpg|thumb|Sylmar East station, rededicated as the Sylmar Converter Station in 2005 following the upgrade to 3,100&nbsp;MW.]]

The first phase of the scheme, completed in May 1970, used only [[mercury-arc valve]]s in the [[HVDC converter|converter]]s.<ref>Compendium of HVDC schemes, [[International Council on Large Electric Systems|CIGRÉ]] [https://e-cigre.org/publication/003-compendium-of-hvdc-schemes-throughout-the-world Technical Brochure No. 003], 1987, pp57-62.</ref> The valves were series connected in three six-pulse valve bridges for each pole. The blocking [[voltage]] of the valves was 133&nbsp;kV with a maximum [[current (electricity)|current]] of 1,800 [[ampere]]s, for a transmission rating of 1,440&nbsp;MW with a symmetrical voltage of 400 kV with respect to earth.

Each converter station housed six mercury arc valves groups, consisting each of seven valves, for a total of 42 valves in each converter.
The valves had a width of {{convert|2.15|m|ft|order=flip}}, a height of {{convert|3.2|m|ft|order=flip}} and a length of {{convert|3.5|m|ft|order=flip}} and weighed {{convert|14000|lb|kg}}. Each valve contained {{convert|1.1|litre|USfloz}} mercury, with a weight of {{convert|14.9|kg|lb|order=flip}}.

* 1972: After the [[Sylmar earthquake]], the [[Sylmar Converter Station]] had to be reconstructed due to extensive damage.
* 1982: The power rating of the mercury arc valve rectifiers was raised by various improvements to 1,600&nbsp;MW.
* 1984: The transmission voltage was pushed to 500&nbsp;kV and the transmission power was increased to 2,000&nbsp;MW by adding one six-pulse [[thyristor valve]] group rated at 100&nbsp;kV to each pole.
* 1989: A further increase of the transmission power to 3,100&nbsp;MW took place by installing a 1,100&nbsp;MW parallel connected thyristor converter in Celilo and Sylmar.  This upgrade started in 1985 was called the ''Pacific Intertie Expansion''.<ref>{{cite web |title=Pacific Intertie |url=https://www.hitachienergy.com/us/en/about-us/customer-success-stories/pacific-intertie |publisher=Hitachi Energy |access-date=20 April 2024}}</ref> This expanded the converter station to two sites, Sylmar West (situated at {{coord|34|18|32|N|118|29|13|W|type:landmark_region:US-CA|name=Sylmar West Converter Station - Pacific DC Intertie (south end)}})<ref>{{cite web |title=Sylmar West HVDC station |url=https://library.e.abb.com/public/4f3509951d3997cac1257b0c00552de5/Sylmar%20West%20HVDC%20station.kmz |publisher=ABB |access-date=20 April 2024}}</ref> and Sylmar East (situated at {{coord|34|18|42|N|118|28|53|W|type:landmark_region:US-CA|name=Sylmar East Converter Station - Pacific DC Intertie (south end)}}).<ref name=ABB/>
* 1993: One pole of the Pacific Intertie Expansion converter station at Sylmar was completely destroyed by fire.<ref>"Fire aspects of HVDC thyristor valves and valve halls", [[International Council on Large Electric Systems|CIGRÉ]] ''[https://web.archive.org/web/20150923221152/http://www.e-cigre.org/bib/136.pdf Technical Brochure No. 136]'', February 1999.</ref> The converter was replaced in 1994–1995 by [[Siemens]].<ref>Christl, N., Faehnrich, W., Lips, P., Rasmussen, F., Sadek, K., "Thyristor Valve Replacement Of The Pacific Intertie Expansion Sylmar East 500 Kv HVDC Converter Station", [[Institution of Electrical Engineers|IEEE]] Sixth International Conference on AC and DC Power Transmission (Conf. Publ. No. 423), 1996.</ref>
* 1994: After the Northridge earthquake, the Sylmar Converter Station had to be reconstructed due to extensive damage.
* 2004: The Sylmar East station was upgraded from 1,100&nbsp;MW to 3,100&nbsp;MW. The controls and older converters, including the mercury arc valves, were completely replaced by a single pair of 3,100&nbsp;MW 12-pulse converters built by [[ABB]]. This allowed the Sylmar East station to handle the full capacity.<ref name="ABB">{{cite news |title=ABB Rededicates Sylmar Converter Station (Press Release) |url=http://www.abb.com/cawp/seitp202/A719AD829B2496D085256FD4006BF446.aspx |publisher=ABB |date=24 March 2005 |archive-url=https://web.archive.org/web/20090201125328/http://www.abb.com/cawp/seitp202/A719AD829B2496D085256FD4006BF446.aspx |archive-date=1 February 2009}}</ref>  In parallel with this project, the six-pulse mercury arc valves at the Celilo Converter Station were replaced with [[Siemens]] [[light-triggered thyristor]]s in compliance with their [[Modified Age Replacement Policy]] (MARP).
* 2005: The Sylmar East station was rededicated as the Sylmar Converter Station.<ref name=ABB/>
* 2014-2015: The Celilo converter substation was upgraded in a similar manner to the Sylmar East upgrade.  The North converter was upgraded from 1,100&nbsp;MW to 3,100&nbsp;MW. The new converter was built by the [[ABB]].  The new converter connects at 500kV AC instead of the previous 230kV AC connection.  After completion, all of the equipment for the south converter was removed.<ref>"Celilo Converter Station", [[Bonneville Power Administration]] ''[https://www.bpa.gov/news/pubs/FactSheets/fs-201604-Celilo-Converter-Station.pdf]'', April 2016. (Fact Sheet)</ref><ref>"ABB completes upgrade of first major HVDC link in U.S. transmission history", [[ABB]] ''[https://new.abb.com/news/detail/45972/abb-completes-upgrade-of-first-major-hvdc-link-in-us-transmission-history]'' 20 June 2016. (press release)</ref>