Transmission towers are used to pass signal wires and electrical current from place to place. They are usually made of steel and can run at times for long distances. Transmission towers are most often used when there is a large amount of electrical current to be distributed, usually between 115,000 and 765,000 volts. Several different designs of transmission towers are in wide use in the world today.
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Lattice Steel Towers
Lattice steel towers are made up of many different steel structural components connected together with bolts or welded. Many different types of lattice steel towers exist. These towers are also called self-supporting transmission towers or free-standing towers, due to their ability to support themselves. These towers are not always made of steel; they can also be made of aluminum or galvanized steel.
Tubular Steel Poles
Tubular steel poles are another of the major types of transmission towers. They are made up of hollow steel poles. Tubular steel poles can be manufactured as one large piece, or as several small pieces which fit together.
SIngle and Double Circuit Towers
Both tubular and lattice steel towers can be designed so as to support either one or two circuits of electrical current. Double-circuit towers hold the different conductors stacked atop one another, while in single-circuit towers the conductors are lined up horizontally.
Guyed towers take up a lot of space, and are therefore only used in parts of the world where land use policy allows them. They consist of two masts supported by four guys, or support cables.
Suspension Straight Towers
Suspension straight towers are a type of self-supporting tower that stands along straight sections of a transmission route. These towers are also sometimes called tangent towers. The only function of these types of towers is to suspend the wires. They do not have to create or regulate tension in any way.
Suspension Angle Towers
Suspension angle towers are built when it is necessary for the route of the electrical current to turn. These angle towers are usually designed so that the axis of the cross-arm bisects the angle of the conductors. This is the most efficient way to use the tower.
Anchor and Angle Tension Towers
Anchor and angle tension towers are used to sectionalize the routes. They terminate the conductors and they provide containment of possible cascade failures.
Terminal Transmission Towers
Terminal transmission towers are at the end of any route. They provide termination of the maximum conductor tensions.