Electric Power Transmission System

an aggregate of electrical installations and devices that can transmit electricity over a distance. It includes step-down and step-up transformers, aerial and/or cable power transmission lines, high-voltage switches, protective devices, and automatic emergency devices. The feasibility of transmitting substantial amounts of electricity over a distance is determined by the power capability of the system, which in turn depends on the voltage and the length of the transmission line, the provision for stable operation, the conditions of use, and the permissible amount of loss. An increase in the power capability of an electric power transmission system is obtained primarily by increasing the voltage of the transmission line (seeHIGH-VOLTAGE ENGINEERING and TRANSMISSION OF ELECTRIC POWER).