page_title: Transmission tower
section_title: Assembly
hierarchical_section_title: Transmission tower / Assembly
caption_attribution_description: Deutsch: Temporärer abgespannter Hochspannungsmast, daneben ein angefangener neuer Gittermast und Bauteile
context_page_description: A transmission tower or power tower is a tall structure, usually a steel lattice tower, used to support an overhead power line.
  In electrical grids, they are generally used to carry high-voltage transmission lines that transport bulk electric power from generating stations to electrical substations; utility poles are used to support lower-voltage subtransmission and distribution lines that transport power from substations to electric customers. They come in a wide variety of shapes and sizes. Typical height ranges from 15 to 55 m, though the tallest are the 370 m towers of a 2,700 m span of Zhoushan Island Overhead Powerline Tie. The longest span of any hydroelectric crossing ever built belonged to the Pylons of Messina with a length of 3,646 m. In addition to steel, other materials may be used, including concrete and wood.
  There are four major categories of transmission towers: suspension, terminal, tension, and transposition. Some transmission towers combine these basic functions. Transmission towers and their overhead power lines are often considered to be a form of visual pollution. Methods to reduce the visual effect include undergrounding.
context_section_description: Before transmission towers are even erected, prototype towers are tested at tower testing stations. There are a variety of ways they can then be assembled and erected:
  They can be assembled horizontally on the ground and erected by push-pull cable. This method is rarely used because of the large assembly area needed.
  They can be assembled vertically (in their final upright position). Very tall towers, such as the Yangtze River Crossing, were assembled in this way.
  A jin-pole crane can be used to assemble lattice towers. This is also used for utility poles.
  Helicopters can serve as aerial cranes for their assembly in areas with limited accessibility. Towers can also be assembled elsewhere and flown to their place on the transmission right-of-way. Helicopters may also be used for transporting disassembled towers for scrapping.
caption: Temporary guyed pylon next to a commenced new tower
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