Pacific DC Intertie

Pacific DC Intertie
Name	Pacific DC Intertie
Caption	Pacific DC Intertie schematic
Country	United States
Start	Celilo Converter Station
End	Sylmar Converter Station
Owner	Bonneville Power Administration, Los Angeles Department of Water and Power
Established	1970
Length km	1400
Type	High-voltage direct current
Capacity MW	3000

Pacific DC Intertie The Pacific DC Intertie is a high-voltage direct current transmission corridor linking the Pacific Northwest and Southern California. It transmits bulk hydroelectric and thermal power between Bonneville Power Administration territories and the Los Angeles Department of Water and Power service area, integrating resources from projects such as Grand Coulee Dam and Boulder Canyon Project. The Intertie plays a central role in Western U.S. power balancing, system reliability, and energy markets involving entities like Western Area Power Administration and California Independent System Operator.

Overview

The Intertie is a long-distance, high-voltage direct current (HVDC) link that provides asynchronous transfer capability between the Bonneville Power Administration grid and the Los Angeles Department of Water and Power grid. It enables bulk transfers from Columbia River basin resources such as Grand Coulee Dam and Dalles Dam to load centers in the Los Angeles region, serving utilities including Southern California Edison, Portland General Electric, and municipal systems like Seattle City Light. The project interfaces with regional operators such as the North American Electric Reliability Corporation and market participants like CalPX (historic) and CAISO.

History and Development

Planning began in the 1950s amid growing demand in Southern California and expanding hydroelectric development on the Columbia River. Key decision-makers included officials from Bonneville Power Administration, Los Angeles Department of Water and Power, and federal agencies behind projects like Grand Coulee Dam and Bonneville Dam. Construction phases paralleled advances in HVDC technology pioneered by firms such as General Electric and Westinghouse Electric Corporation. The first bipolar system entered service in 1970, with uprates and modernizations carried out in later decades involving contractors like Siemens and ABB Group.

Route and Technical Specifications

The route runs roughly 1,400 kilometers from the Celilo Converter Station near The Dalles, Oregon down the Columbia River corridor, across the Cascade Range and through the Central Valley (California), terminating at the Sylmar Converter Station in the San Fernando Valley. Original configuration used ±500 kV bipolar conductors; voltage and conductor arrangements have been subject to uprates and reconductoring by firms such as Phelps Dodge and Alcoa. The line crosses major transmission corridors including rights-of-way adjacent to Pacific Gas and Electric Company lines and interfaces near substations like Patterson Substation and Palo Verde Power Plant interconnections. Terrain challenges include river canyons, mountain passes near the Sierra Nevada, and urban approaches into Los Angeles.

Converter Stations and Equipment

The terminal converter stations at Celilo Converter Station and Sylmar Converter Station use thyristor-based line-commutated converters originally supplied by manufacturers including General Electric and later retrofitted with equipment from Siemens and ABB Group. Converter transformers, smoothing reactors, and harmonic filters are essential components; maintenance and upgrades have involved companies such as Bechtel and Eaton Corporation. Control systems integrate with regional control centers like Bonneville Power Administration Control Center and Los Angeles Department of Water and Power Control Center, and protection schemes coordinate with entities such as North American Electric Reliability Corporation and Western Electricity Coordinating Council.

Operations and Transmission Capacity

Originally rated around 3,100 MW at ±500 kV, operational capacity has varied with equipment upgrades, dynamic ratings, and thermal limits managed by operators including Bonneville Power Administration and Los Angeles Department of Water and Power. The Intertie supports daily and seasonal energy exchanges—moving surplus hydroelectric energy during spring runoff from facilities like Grand Coulee Dam to southern loads, and enabling return flows during other periods. Dispatch coordination involves market participants such as Southern California Edison, Pacific Gas and Electric Company, and balancing authorities like CAISO. Reliability events and disturbances have been analyzed in studies by North American Electric Reliability Corporation and led to procedural changes implemented by Western Electricity Coordinating Council.

Impact and Economic Significance

The Intertie has enabled economic transfers of low-cost hydroelectric power, affecting wholesale prices in markets served by CAISO and Northwest Power and Conservation Council regions. It has been instrumental in supporting Los Angeles Department of Water and Power reliability during drought or thermal outages and in integrating generation from projects like Grand Coulee Dam, Chief Joseph Dam, and John Day Dam. The corridor has influenced transmission planning by organizations such as Western Electricity Coordinating Council and has economic links to industries reliant on stable power in Southern California, including manufacturing hubs and data centers serviced by Southern California Edison and municipal utilities.

Future Upgrades and Projects

Planned and proposed enhancements include converter station modernizations, potential voltage uprates, and improved control and protection systems involving vendors like ABB Group and Siemens. Studies by Bonneville Power Administration, California Energy Commission, and Western Electricity Coordinating Council consider capacity additions, integration with renewable resources such as offshore and utility-scale wind farms and solar power plants, and coordination with regional initiatives like Path 15 reinforcement. Stakeholders including Los Angeles Department of Water and Power, Bonneville Power Administration, and regional transmission planners continue to evaluate long-term reinforcements to support Western interconnection resilience and market integration.

Category:High-voltage direct current transmission lines in the United States