Advanced Transmission Technologies
Advanced Transmission Technologies December 2020 United States Department of Energy Washington, DC 20585 Executive Summary The high-voltage transmission electric grid is a complex, interconnected, and interdependent system that is responsible for providing safe, reliable, and cost-effective electricity to customers. In the United States, the transmission system is comprised of three distinct power grids, or “interconnections”: the Eastern Interconnection, the Western Interconnection, and a smaller grid containing most of Texas. The three systems have weak ties between them to act as power transfers, but they largely rely on independent systems to remain stable and reliable. Along with aged assets, primarily from the 1960s and 1970s, the electric power system is evolving, from consisting of predominantly reliable, dependable, and variable-output generation sources (e.g., coal, natural gas, and hydroelectric) to increasing percentages of climate- and weather- dependent intermittent power generation sources (e.g., wind and solar). All of these generation sources rely heavily on high-voltage transmission lines, substations, and the distribution grid to bring electric power to the customers. The original vertically-integrated system design was simple, following the path of generation to transmission to distribution to customer. The centralized control paradigm in which generation is dispatched to serve variable customer demands is being challenged with greater deployment of distributed energy resources (at both the transmission and distribution level), which may not follow the traditional path mentioned above. This means an electricity customer today could be a generation source tomorrow if wind or solar assets were on their privately-owned property. The fact that customers can now be power sources means that they do not have to wholly rely on their utility to serve their needs and they could sell power back to the utility.
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