FACTS (Flexible Alternating Current Transmission Systems) refers to a set of technologies that enhance the efficiency, stability, and controllability of AC power transmission networks. FACTS devices help regulate voltage, control power flow, and improve grid reliability, reducing transmission losses and preventing overloads. Common FACTS components include Static VAR Compensators (SVC), Static Synchronous Compensators (STATCOM), and Unified Power Flow Controllers (UPFC). These systems are essential for modernizing power grids, integrating renewable energy sources, and ensuring efficient power distribution in high-demand networks.

A Fault-Closing Device is a protective device designed to safely close a circuit during a fault condition, such as a short circuit or voltage surge. It helps restore power quickly while ensuring system stability and minimizing damage to electrical equipment. These devices are commonly used in circuit breakers and reclosers to improve power grid reliability by allowing controlled fault clearance and system restoration without manual intervention.

A Feeder is a power line that transmits electricity from a substation to distribution transformers or directly to consumers. It serves as a key link in the electrical distribution network, delivering power to residential, commercial, and industrial areas. Feeders can be overhead or underground and are designed to handle varying loads while maintaining voltage stability. They are equipped with protective devices such as circuit breakers and reclosers to ensure reliability and prevent faults from spreading through the power system.

Frequency refers to the number of cycles of an alternating current (AC) or electromagnetic wave that occur per second, measured in hertz (Hz). In power systems, standard frequencies are 50 Hz (used in most of the world) and 60 Hz (used in North America). Frequency stability is crucial for the efficient operation of electrical grids, as variations can affect power quality and equipment performance. In communications, frequency determines signal transmission characteristics, such as in radio, television, and wireless networks.