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1 1 (November 18, 2022)

handle is hein.crs/govejln0001 and id is 1 raw text is: Congressional Research Service Infermin g Ih kegisltive d bate sirc 'o914 Introduction to Electricity Transmission November 18, 2022 The U.S. electricity transmission system connects the electricity generation system-where electricity is made- and the electricity distribution system-where electricity is used. Figure I. Electric Power Sector System Schematic Source: CRS, adapted from U.S.-Canada Power System Outage Task Force, Final Report on the August 1 4, 2003, Blackout in the United States and Canada: Causes and Recommendations, April 2004, p. 5. Notes: Not all types of components in each system are shown. The transmission system includes hundreds of thousands of miles of power lines that carry electricity at relatively high voltages. Transmission line voltages range from 230 thousand volts (kV) to 765 kV, though lower voltages can be used as well. The higher the voltage, the more power can move through the line. Approximately 98% of the U.S. transmission system uses alternating current (AC) power, in which the direction of electrical charge changes 60 times per second. The remainder uses direct current (DC), in which the direction of charge does not change. AC power can be converted relatively easily and cheaply between high and low voltages, making it more suitable for delivering it to customers that use low voltage AC (e.g., 120 V for most household uses). DC lines require expensive conversion stations, but can be more efficient over very long distances and better suited for specialized applications, such as undersea cables. The transmission system also includes thousands of transformers that change voltage levels, stepping up or stepping down voltages to higher or lower levels, respectively. Transformers also provide electric stability to the grid. High-voltage transformers vary in size (measured in input/output voltage or power levels), and typically are custom-built for specific locations in the transmission system. Ownership and Regulation Most transmission lines are owned by private, for-profit companies, though some are owned by public entities: the federal government, publicly-owned utilities (e.g., divisions of a municipal government), or member-owned electric cooperatives. The Federal Energy Regulatory Commission (FERC) regulates the rates these transmission owners charge for delivering electricity across state lines. FERC also can approve financial incentives for certain construction and operational activities. For example, FERC can incentivize the use of new technologies and participation in regional transmission organizations in which power resources are shared in a region. Power sharing is believed to increase reliability and lower overall costs for consumers. The federal government does not have general siting authority for transmission lines-in most cases, state and local governments have authority for siting. Federal permits may be necessary for portions of some transmission lines, such as those that cross federal lands (e.g., National Forests) or waters under jurisdiction of the U.S. Army Corps of Engineers. Congress gave FERC backstop authority for siting transmission lines in areas designated by the U.S. Department of Energy (DOE) to be in the national interest. In these cases, FERC can site transmission lines when state or local governments fail to take action or deny an application. To date, no transmission lines have been approved under this authority. Perceived Transmission Needs Some advocates have expressed interest in expanding and enhancing the U.S. transmission system. Part of this interest relates to a desire to use more renewable energy for electricity generation. Many of the country's best renewable energy resources are concentrated in a few areas: onshore wind in the central United States, solar in the Southwest, and offshore wind in the Northeast. New transmission lines are likely needed to cost-effectively develop these resources and deliver the electricity to consumers. Some of the advocates propose a greater use of DC transmission to move electricity from these areas across the country. A number of transmission projects have been proposed associated with these areas of strong renewable energy resources, as shown in Figure 2. (The figure also shows proposed lines that would allow greater import of hydropower from the Canadian province of Quebec.) These proposed projects are unique from other transmission projects in that they cross multiple states and connect different regions of the electricity grid with each other.

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