Flexible Alternating Current Transmissions Systems (FACTS) include technologies that increase transmission system efficiency, maintain power quality, and respond quickly to disruptions to maintain reliability of the bulk power system. FACTS can be used to manipulate the conditions on transmission lines to keep AC power in balance by maintaining voltage stability, keeping current and voltage “in sync,” and dampening distortions. Transmission operators have always had to perform these functions, but in the past they used devices that relied on mechanical switches that performed more slowly, less efficiently, and less reliably. By dynamically managing AC power and line conditions, FACTS can raise the carrying capacity of existing lines, route power more efficiently, and direct power flow along contractual paths. Additionally, in regions with high renewable power penetration, FACTS can provide frequency response that traditionally required inefficient spinning generators.

The first FACTS technologies were deployed in the 1970s, starting with Static VAR Compensators (SVCs). Since then FACTS technologies have continued to grow in variety and sophistication; Navigant Research estimates that $42 billion will be invested in FACTS globally between 2014 and 2023. The U.S. grid already relies to some extent on FACTS to provide reliability, power quality, and control. In Texas, leading FACTS provider ABB installed four SVCs to allow existing transmission lines to carry more wind power and compensate for changes in voltage and power flow that can occur with variable output of wind generation. ABB also installed an SVC and two mechanically switched capacitors (MSCs) in Alaska to provide dynamic voltage control to a remote area of the grid subject to reliability challenges. FACTS technology can also be deployed incrementally as required to monitor line current and augment line impedance. The Tennessee Valley Authority and Southern Company are both using devices from Smart Wires to manage power flow, maintain reliability, and integrate higher levels of renewable generation.

By improving the performance of the existing grid, FACTS avoid the need to invest in costly new infrastructure subject to siting and permitting challenges. FACTS are also able to integrate variable renewable generation while delivering the reliability and power quality that are increasingly important in our IT-driven economy. Finally, by extending the operating range and capacity of transmission lines and enabling power to flow along contractual paths, FACTS can help increase competition and allow power markets to function more effectively.