If a line is constructed using towers designed to carry several circuits, it is not necessary to install all the circuits at the time of construction. Towers for high- and extra-high voltage are usually designed to carry two or more electric circuits (with very rare exceptions, only one circuit for 500-kV and higher). Typically, one or two ground wires, also called "guard" wires, are placed on top to intercept lightning and harmlessly divert it to ground. The towers are usually steel lattices or trusses (wooden structures are used in Australia, Canada, Germany, and Scandinavia in some cases) and the insulators are either glass or porcelain discs or composite insulators using silicone rubber or EPDM rubber material assembled in strings or long rods whose lengths are dependent on the line voltage and environmental conditions. The towers must be designed to carry three (or multiples of three) conductors. Germany, Spain or Czech Republic, smaller lattice towers are used for medium voltage (above 10 kV) transmission lines too. Three-phase electric power systems are used for high voltage (66- or 69-kV and above) and extra-high voltage (110- or 115-kV and above most often 138- or 230-kV and above in contemporary systems) AC transmission lines. High voltage AC transmission towers Transmission tower in Toronto, ON Single-circuit three-phase transmission line In Canada, the term hydro tower is commonly used as hydroelectricity constitutes a majority of the country's energy production. In the United States, the use of the term pylon is more common in the Midwest, including areas such as Cincinnati and Chicago. This term is used infrequently in most regions of the United States as pylon commonly refers to other things, primarily traffic cones. The term electricity pylon or simply pylon comes from the basic shape of the structure, an obelisk-like structure which tapers toward the top, and the name is mostly used in the United Kingdom and parts of Europe in everyday colloquial speech. Transmission tower is the name for the structure used in the industry in the United States and some other English-speaking countries. Methods to reduce the visual effect include undergrounding. Transmission towers and their overhead power lines are often considered to be a form of visual pollution.
Some transmission towers combine these basic functions. There are four major categories of transmission towers: suspension, terminal, tension, and transposition. In addition to steel, other materials may be used, including concrete and wood. The longest span of any hydroelectric crossing ever built belongs to the powerline crossing of Ameralik fjord with a length of 5,376 m (17,638 ft).
Typical height ranges from 15 to 55 m (49 to 180 ft), though the tallest are the 380 m (1,247 ft) towers of a 2,656 m (8,714 ft) span between the islands Jintang and Cezi in China's Zhejiang province.
They come in a wide variety of shapes and sizes. In electrical grids, they are generally used to carry high-voltage transmission lines that transport bulk electric power from generating stations to electrical substations before reaching its end consumers utility poles are used to support lower-voltage subtransmission and distribution lines that transport power from substations to electric customers. Structure, lattice tower and overhead power lineĪ transmission tower, also known as an electricity pylon or simply a pylon in British English and as a hydro tower in Canadian English, is a tall structure, usually a steel lattice tower, used to support an overhead power line.
0 kommentar(er)
