Pacific DC Intertie
The Pacific DC Intertie (also called Path 65) is an electric power transmission line that transmits electricity from the Pacific Northwest to the Los Angeles area using high voltage direct current (HVDC). The line capacity is 3,100 megawatts, which is enough to serve two to three million Los Angeles households and is 48.7% of the Los Angeles Department of Water and Power (LADWP) electrical system's peak capacity.
The intertie originates near the Columbia River at the Celilo Converter Station on Bonneville Power Administration's grid outside The Dalles, Oregon and is connected exclusively to the Sylmar Converter Station north of Los Angeles, which is owned by five utility companies and managed by LADWP. The Intertie can transmit power in either direction, but power flows mostly from north to south.
The idea of shipping 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 opposed the project but their technical objections were rebutted by Uno Lamm of ASEA at the 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 electric power from projects on the Columbia River.
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).
The Pacific Intertie consists of:
- The Celilo Converter Station which converts three phase 60 Hz AC at 235 to 525 kV to ±500 kV DC at Coordinates: .
- The grounding system at Celilo consists of 1,067 cast iron anodes buried in a two foot trench of petroleum coke, which behaves as an electrode, arranged in a ring of 3,255 m (2.02 mi) circumference at Rice Flats (near Rice, Oregon), which is 10.6 km (6.6 mi) SSE of Celilo. It is connected to the converter station by two aerial 644 mm2 steel-reinforced aluminum (ACSR) cables, which end at a strainer situated at .
- A 1,362-kilometre (846 mi) overhead transmission line consisting of two uninsulated conductors each 1,171 mm2 in cross sectional area, containing a steel wire core for strength.
- The Sylmar Converter Station ( ) which converts DC to AC (a process also called inverting) and 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 suspended in concrete enclosures about one meter above the ocean floor. The grounding array, which is 48 km (30 mi) from the converter station and is connected by a pair of 644 mm2 aluminum conductors, which are in the sections north of Kenter Canyon Terminal Tower at installed instead of the ground conductors on the pylons. It runs from Kenter Canyon Terminal Tower, via DWP Receiving Station U, Southern California Edison Northridge Substation and Rinaldi Electrical Substation to Sylmar Converter Station. On the section between Northridge substation and Rinaldi Street substation one of the two ground conductors of 2 parallel running 220 kV powerlines is used as electrode line conductor.
- The combined wires have a capacity of 3.1 gigawatts in bipolar mode.
The first phase of the scheme, completed in May 1970, used only mercury-arc valves in the converters. 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. 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 Sylmar Converter Station had to be reconstructed due to extensive damage.
- In 1982, the power rating of the mercury arc valve rectifiers was raised by various improvements to 1,600 MW.
- In 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.
- In 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, the so-called Pacific Intertie Expansion
- In 1993, one pole of the Pacific Intertie Expansion converter station at Sylmar was completely destroyed by fire. The converter was replaced in 1994/5 by Siemens.
- 2004, Sylmar East station situated at 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). 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
The Pacific DC Intertie along a service road paralleling Highway 395. Many of the towers of the Intertie are of this simple, slender design
The slender tower is supported laterally by four guy-wires
See also 
- Sharon Bernstein and Amanda Covarrubias, Times Staff Writers (September 10, 2006). "Heat Wave Caught DWP Unprepared". L.A. Times online. Retrieved 2006-09-11.[dead link]
- Prabha Kundur, Powertech Labs Inc. (October 3, 2003). "Power System Security in the New Industry Environment: Challenges and Solutions" (powerpoint). IEEE. p. 17. Retrieved 2006-09-11.
- "The Pacific Intertie Scheme". Bonneville Power Administration. 2000-11-03. Archived from the original on 2005-04-26. Retrieved 2009-08-20.
- Compendium of HVDC schemes, CIGRÉ Technical Brochure No. 003, 1987, pp57-62.
- Fire aspects of HVDC thyristor valves and valve halls, CIGRÉ Technical Brochure No. 136, February 1999.
- 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, IEE Sixth International Conference on AC and DC Power Transmission(Conf. Publ. No. 423), 1996.
- ABB Rededicates Sylmar Converter Station, 24 March 2005.
More on the ABB website on Pacific HVDC Intertie:
- aerial photo of Sylmar inverter plant