Pacific DC Intertie

The idea of sending hydroelectric power to Southern California had been proposed as early as the 1930s, but was opposed and scrapped. By 1961, US president John F. Kennedy authorized a large public works project, using new high voltage direct current technology from Sweden. The project was undertaken as a close collaboration between General Electric of the US and ASEA of Sweden. Private California power companies had opposed the project but their technical objections were rebutted by Uno Lamm of ASEA at an IEEE meeting in New York in 1963. When completed in 1970 the combined AC and DC transmission system was estimated to save consumers in Los Angeles approximately US$600,000 per day by use of cheaper electric power from dams on the Columbia River.

One advantage of direct current over AC is that DC current penetrates the entire conductor as opposed to AC current which only penetrates to the skin depth. For the same conductor size, the effective resistance is greater with AC than DC, hence more power is lost as heat with AC. In general, the total cost for HVDC is less than an AC line if the line length is over 500–600 kilometers, and with advances in conversion technology, this distance has been reduced considerably. A DC line is also ideal for connecting two AC systems that are not synchronized with each other. HVDC lines can help stabilize a power grid against cascading blackouts since power flow through the line is controllable.

The Pacific Intertie takes advantage of differing power demand patterns between the northwestern and southwestern US. During winter, the northern region operates electrical heating devices while the southern portion uses relatively little electricity. In summer, the north uses little electricity while the south reaches peak demand due to air conditioning usage. Any time the Intertie demand lessens, the excess is distributed elsewhere on the western power grid (states west of the Great Plains, including Colorado and New Mexico).{{cite web

|url = http://www.ewh.ieee.org/r7/toronto/events/oct0303/prabha.ppt

|format = PowerPoint

|title = Power System Security in the New Industry Environment: Challenges and Solutions

|author = Prabha Kundur, Powertech Labs Inc.

|page = 17

|publisher = IEEE

|date = October 3, 2003

|access-date = 2006-09-11

|url-status = dead

|archive-url = https://web.archive.org/web/20060822101832/http://ewh.ieee.org/r7/toronto/events/oct0303/prabha.ppt

|archive-date = August 22, 2006

}}

File:Img0259HVDC 500kV wire.JPG|The HVDC power line in Los Angeles (shorter tower carrying two wires on the right). The power line crosses Interstate 5 near the interchange with Interstate 210 in Sylmar.

File:Path 65 P0002014.jpg|The Pacific DC Intertie along a service road paralleling U.S. Highway 395. Many of the towers of the Intertie are of this simple, slender design

File:Path 65 P0002019.jpg|The slender tower's base tapers down to a single point that is bolted to a concrete anchor

File:Path 65 P0002020.jpg|The slender tower is supported laterally by four guy-wires

File:PacificIntertie.jpg|The Pacific Intertie outside of Benton, California

File:Pacific DC Intertie Towers near Fernley, Nevada.jpg|Pacific DC Intertie towers (left side) near Fernley, Nevada. The first few towers are self-supported. The towers on the far side use guy-wires.

The Pacific Intertie consists of:{{cite web

| url = http://www.transmission.bpa.gov/cigresc14/Compendium/PACIFIC.htm

| title = The Pacific Intertie Scheme

| publisher = Bonneville Power Administration

| date = 2000-11-03

| access-date = 2009-08-20

|archive-url = https://web.archive.org/web/20050426045806/http://www.transmission.bpa.gov/cigresc14/Compendium/PACIFIC.htm |archive-date = 2005-04-26}}

• The Celilo Converter Station which converts three phase 60 Hz AC at 230 to 500 kV to ±500 kV DC (1000 kV pole-to-pole) at {{coord|45|35|39|N|121|6|51|W|type:landmark_region:US-OR|display=inline,title|name=Celilo Converter Station - Pacific DC Intertie (north end)}}.
• The grounding system at Celilo consists of 1,067 cast iron anodes buried in a {{convert|2|ft|cm|-1|adj=on|spell=in}} trench of petroleum coke, which behaves as an electrode, arranged in a ring of {{convert|3255|m|mi|1|order=flip}} circumference at Rice Flats (near Rice, Oregon), which is {{convert|10.6|km|mi|order=flip}} SSE of Celilo. It is connected to the converter station by two aerial {{convert|644|mm2|in2|abbr=on}} ACSR (aluminum conductor, steel reinforced) conductors, which end at a "dead-end" tower situated at {{coord|45.497586|-121.064620|type:landmark_region:US-OR|name=End of electrode line|format=dms}}.
• A {{convert|1361|km|mi|adj=on|order=flip}} overhead transmission line consisting of two steel-cored ACSR conductors, each {{convert|1.6|in|cm}} in diameter with a conducting cross-sectional area of {{convert|1171|mm2|in2|abbr=on}}, carrying 500 kV.
• The two lines when combined have a capacity of 3.1 gigawatts (in bipolar mode).
• The Sylmar Converter Station ({{coord|34|18|42|N|118|28|53|W|type:landmark_region:US-CA|name=Sylmar Converter Station - Pacific DC Intertie (south end)}}) which converts DC to 230 kV AC (a process also called inverting) and is phase-synchronized with the L.A. power grid.
• The Sylmar grounding system is a line of 24 silicon-iron alloy electrodes submerged in the Pacific Ocean at Will Rogers State Beach{{cite web|url=https://placesjournal.org/article/the-infrastructural-city/|title=Review of The Infrastructural City, edited by Kazys Varnelis |publisher=Places Journal}} suspended in concrete enclosures about {{convert|0.5|to|1|m|ft|0|sp=us|order=flip}} above the ocean floor. The grounding array, which is {{convert|48|km|mi|0|order=flip}} from the converter station and is connected by a pair of {{convert|644|mm2|in2|abbr=on}} ACSR conductors, which are in the sections north of Kenter Canyon Terminal Tower at {{coord|34|04|04.99|N|118|29|18.5|W|type:landmark|name=Southern California Edison Malibu Substation, Pacific DC Intertie - End of overhead electrode line}} installed instead of the ground conductors on the pylons. It runs from Kenter Canyon Terminal Tower, via DWP Receiving Station U (Tarzana; a former switching station), Receiving Station J (Northridge) and Rinaldi Receiving Station (also a former switching station) to Sylmar Converter Station. On the section between Receiving Stations J and Rinaldi, one of the two shielding conductors on each of two parallel-running 230 kV transmission lines is used as electrode line conductor.

File:Sylmar Converter Station.jpg

The first phase of the scheme, completed in May 1970, used only mercury-arc valves in the converters.Compendium of HVDC schemes, CIGRÉ [https://e-cigre.org/publication/003-compendium-of-hvdc-schemes-throughout-the-world Technical Brochure No. 003], 1987, pp57-62. 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 rating of 1,440 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 MW.
• 1984: The transmission voltage was pushed to 500 kV and the transmission power was increased to 2,000 MW by adding one six-pulse thyristor valve group rated at 100 kV to each pole.
• 1989: A further increase of the transmission power to 3,100 MW took place by installing a 1,100 MW parallel connected thyristor converter in Celilo and Sylmar. This upgrade started in 1985 was called the Pacific Intertie Expansion.{{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}} 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)}}){{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}} 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)}}).
• 1993: One pole of the Pacific Intertie Expansion converter station at Sylmar was completely destroyed by fire."Fire aspects of HVDC thyristor valves and valve halls", CIGRÉ [https://web.archive.org/web/20150923221152/http://www.e-cigre.org/bib/136.pdf Technical Brochure No. 136], February 1999. The converter was replaced in 1994–1995 by Siemens.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", IEEE Sixth International Conference on AC and DC Power Transmission (Conf. Publ. No. 423), 1996.
• 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 MW to 3,100 MW. 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. This allowed the Sylmar East station to handle the full capacity.{{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}} In parallel with this project, the six-pulse mercury arc valves at the Celilo Converter Station were replaced with Siemens light-triggered thyristors in compliance with their Modified Age Replacement Policy (MARP).
• 2005: The Sylmar East station was rededicated as the Sylmar Converter Station.
• 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 MW to 3,100 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."Celilo Converter Station", Bonneville Power Administration [https://www.bpa.gov/news/pubs/FactSheets/fs-201604-Celilo-Converter-Station.pdf], April 2016. (Fact Sheet)"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)

• Uno Lamm
• Path 27
• North American Electric Reliability Corporation
• WECC Intertie Paths
• Path 66

{{Reflist}}

• [http://new.abb.com/systems/hvdc/references/pacific-intertie Pacific Intertie (abb.com) ]
• [https://web.archive.org/web/20050426045806/http://www.transmission.bpa.gov/cigresc14/Compendium/PACIFIC.htm The Pacific Intertie Scheme (BPA, via web.archive.com)]
• [http://wecc.biz/ Wecc.biz]

{{Power Transmission Corridors of the Western United States}}

{{DEFAULTSORT:Pacific Dc Intertie}}

Category:Energy infrastructure completed in 1970

Category:1970 establishments in California

Category:Energy infrastructure in Oregon

Category:Energy infrastructure in California

Category:HVDC transmission lines

Category:Western Interconnection