Transmission Lines:

Issues Associated with High-Voltage Direct-Current Transmission Lines along Transportation Rights of Way

GAO-08-347R: Published: Feb 1, 2008. Publicly Released: Feb 1, 2008.

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David J. Wise
(202) 512-3000


Office of Public Affairs
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Electricity is central to the national economy and the daily lives of many Americans, powering homes, businesses, and industries. Today, an extensive system consisting of more than 150,000 miles of high-voltage transmission lines works to provide reliable electricity service and transport electricity from power plants to consumers. Federal and state entities share responsibility for regulating the electricity system. On the federal level, the Federal Energy Regulatory Commission (FERC) regulates interstate transmission of electricity and wholesale rates, among other regulatory activities. State public utility commissions are generally responsible for regulating retail electricity sales and, in some cases, planning for new power plants and transmission lines. However, as studies have shown, growth in electricity demand has strained the nation's transmission system, resulting in less flexibility to respond to system problems and an increased risk of potential blackouts. These issues have led some to suggest that new lines or other investments in the transmission system may be required to increase capacity and accommodate growing electricity demand. Several companies have recently introduced proposals to build new high-voltage direct-current (HVDC) transmission lines. Some of these proposed lines would follow active transportation rights of way, such as railroads, highways, and pipelines. Some stakeholders have raised concerns about the potential economic, safety, and security issues related to collocating new HVDC transmission lines along transportation rights of way, particularly for nearby residents and consumers of electric power. Given these issues, Congress included a provision in the Implementing Recommendations of the 9/11 Commission Act of 2007 requiring us to assess the siting of HVDC transmission lines along active railroad and other transportation rights of way and report to appropriate congressional committees. In response to this requirement and after discussions with the committees, we examined (1) the role of the federal government in siting HVDC electric transmission lines along active transportation rights of way, (2) advantages and disadvantages of adding transmission lines and using HVDC technology, and (3) benefits and risks associated with the siting of HVDC electric transmission lines along active transportation rights of way.

Historically, the federal government has had a limited role in siting transmission lines. It has generally only made siting decisions on federal lands. State governments, through public utility commissions and other agencies, traditionally approve transmission line siting. However, the Energy Policy Act of 2005 expanded the federal government's role. Specifically, under certain circumstances, FERC now has the authority to approve and issue siting permits for new transmission lines in areas designated by the Department of Energy as National Interest Electric Transmission Corridors (NIETC). However, some stakeholders have expressed concerns about FERC's expanded authority in the national corridors, including how the state siting process will be affected and whether states and the public will be involved in FERC's proceedings. FERC officials told us they expect the review of a transmission line proposal in the national corridors would have little impact on the states' existing process. FERC officials also told us that to the extent FERC receives applications, they expect to consider information from the state siting process as part of their federal proceeding and that states and the public will have opportunities to participate in and comment on the federal siting process. Currently, federal statutes as well as federal and state guidance encourage the collocation of new transmission lines along existing transportation and other rights of way. We identified potential advantages and disadvantages to adding transmission lines and using HVDC technology. According to studies we reviewed and stakeholders we interviewed, adding transmission lines offers potential advantages, including (1) decreased congestion and improved reliability of the electricity system by providing access to additional sources of generation and additional paths for electricity, (2) lower costs for consumers at the end of the line where electricity is received, (3) better utilization of existing power plants and more competitive local wholesale electricity markets, (4) facilitated development of new electricity sources location outside population centers, and (5) facilitated development of renewable energy sources. Stakeholders and studies also identified potential disadvantages of adding transmission lines, including (1) diminished economic or aesthetic values of the land if lines are built above ground, (2) raised electricity prices in areas from where the electricity is being taken, and (3) reduced incentives to identify alternatives that decrease demand (e.g., energy conservation). With respect to the potential advantages of using HVDC over HVAC technology, studies we reviewed and stakeholders we interviewed indicated that HVDC lines generally (1) cost less than HVAC over long distances and (2) allow operators of transmission systems to have more control over the direction and the amount of power flowing over HVDC lines. Potential disadvantages of using HVDC over HVAC technology include (1) higher costs for short-distance lines due to the cost of equipment needed to convert DC into AC electricity used by residents and (2) the lack of electricity benefits to consumers living along these lines--unless converter stations are installed at intermediate locations--because such lines are generally not connected to local electricity lines.

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