How the electric transmission system works
Typical transmission line structures How dependable electricity reaches you
Transmission lines are sets of wires, called conductors, that carry electric power from generating plants to the substations that deliver power to customers. At a generating plant, electric power is stepped up to several thousand volts by a transformer and delivered to the transmission line. At numerous substations on the transmission system, transformers step down the power to a lower voltage and deliver it to distribution lines. Distribution lines carry power to farms, homes and businesses. The type of transmission structures used for any project is determined by the characteristics of the transmission line s route, including terrain and existing infrastructure.
Typical transmission line structures
High-voltage (230-kV, 345-kV, 400-kV (DC), 500-kV (DC):
Currently in Minnesota, the high-voltage system is generally comprised of 230-kiloVolt and 345-kV systems. There are also two direct current (DC) lines, one of 400-kV and one at 500-kV.
Structures are generally steel lattice towers, wooden H-Frames or single-pole steel. (photos below of each).
Lower voltage transmission systems:
161-kV and 115-kV systems are responsible for transmitting power from the larger transmission system and generation facility throughout the entire state. Some large industrial customers may be served directly from 161-kV and 115-kV systems.
161-kV and 115-kV structures are generally single pole structures between 70 and 95 feet tall.
69-kV through 23-kV systems transmit power to distribution substations. These also provide connection to some of the more remote and sparsely populated areas in greater Minnesota. Many smaller and rural industrial customers receive power directly from these systems.
Structures are generally single pole towers, constructed of either wood or steel and range from 50-70 feet tall.