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Bonneville Power transmission line provides electrical power from the Columbia River to California

 - A 1964 map shows the Pacific Northwest-Southwest Interie.

A major electrical power line was constructed from the Columbia River south to California beginning in 1966 and completed in 1970. The power transmission system is known as the Pacific Northwest-Pacific Southwest Intertie. The Bonneville Power Administration (BPA) constructed 265 miles of transmission line from Celilo Converter Plant near The Dalles Dam to the Nevada border. The remaining 580 miles of line passed through Nevada to Los Angeles and was constructed by the City of Los Angeles. The line is 846 miles long and when it was completed it was the longest power line of its kind in the world.

There are three legs to the system. A direct current (d-c) line was constructed from the Celilo Converter Plant and extends south to Sylmar Station near Los Angeles. Electrical power generated by the Columbia River hydroelectric system is alternating current (a-c) and it is converted to d-c for easier transmission over long distances. Once the power reaches the Sylmar Station, the power is converted back to a-c before being transmitted to customers. The bipolar overhead transmission line has an operating voltage of 800kV and a power rating of 1,440 megawatts.

Two a-c lines from John Day Substation near John Day Dam on the Columbia River were constructed in the late 1960s and come in close proximity to the d-c line. The lines converge at the Grizzly Substation between Madras and Prineville. Each a-c line is 500 kV and rated 1,000 megawatt capacity and extend to Lugo Substation in Los Angeles. Portland General Electric (PGE) operates a transmission line from the John Day Substation to the Round Butte interconnection. PGE operates the transmission line from Round Butte to the Oregon/California state line. The California Power Pool operates both a-c lines from the Oregon border to Lugo.

The two a-c lines and the d-c line pass through Central Oregon and are prominent on the landscape of the region. The two a-c lines are side by side and the d-c line is slightly separated from the other two lines. It was a major construction project that exports Columbia River power to Los Angeles. Ponderosa Substation near Powell Butte converts some power for use in the large data centers located near Prineville.

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