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High Voltage Direct Current (HVDC)

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Pacific DC Intertie (PDCI)

The Pacific Direct Current Intertie (PDCI) is a 1354 km HVDC line that extends from the Columbia River to Los Angeles (Figure 1). It began operation in 1970, with mercury-arc valves that have been replaced with different generations of thyristor valves.

The PDCI transmits 3.1 Gigawatts (GW) of electricity at ±500 kV. Electricity is transmitted in either direction: from north to south, or from south to north. There are no substations along the way, just a converter station (terminal) at each end. Think of HVDC as a highly efficient express train that does not make stops along the way.

The PDCI is 2-pole (two conductor bundles) with earth (ground) return for single pole use (at half power) if needed (can provide extended emergency use). A ring of ground electrodes provide the northern earth return. Ocean electrodes in the Pacific Ocean provide the southern earth return.

Originally the PDCI transmitted 1.4 GW at 800 kV (±400 kV). The PDCI will soon be upgraded to 3.22 GW, and may later be upgraded to 3.8 GW in the north-to-south direction. Voltage will be upgraded to ±560 kV.

The original PDCI plan proposed additional 800 kV HVDC lines that were not built. Another 800 kV HVDC line would have been adjacent to the present PDCI line in Oregon and Nevada, staying on the Nevada side and continuing to Mead, near Hoover Dam, where another 800 kV HVDC line would have extended to Los Angeles (reported in G. D. Breuer, E. M. Hunter, P. G. Engstrom, R. F. Stevens, “The Celilo Converter Station of the Pacific HV-DC Intertie”, IEEE Transactions on Power Apparatus and Systems, November 1966, p. 1116–1128).

Figure 1.  Pacific DC Intertie (PDCI).

Aerial photographs

Map of 1964 proposal

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