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An electricity pylon or transmission tower (also known as an ironman in Australia and a hydro tower in Canadamarker) is a tall structure, usually a steel lattice tower, used to support overhead electricity conductors for electric power transmission.

High voltage AC transmission towers

Three-phase electric power systems are used for high and extra-high voltage AC transmission lines (50 kV and above). The towers must be designed to carry three (or multiples of three) conductors. The towers are usually steel lattices or trusses (wooden structures are used in Germanymarker 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 rod whose length is dependent on the line voltage and environmental conditions. One or two earth conductors (or "ground conductors") for lightning protection are often mounted at the top of each tower.

In some countries, towers for high and extra-high voltage are usually designed to carry two or more electric circuits. For double circuit lines in Germany, the "Danube" towers or more rarely, the "fir tree" towers, are usually used. 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.

Some high voltage circuits are often erected on the same tower as 110 kV lines. Paralleling circuits of 380 kV, 220 kV and 110 kV-lines on the same towers is common. Sometimes, especially with 110 kV circuits, a parallel circuit carries traction lines for railway electrification.

A new type of pylons will be used in the Netherlands starting in 2010. The pylons were designed as a minimalist structure by Dutch architects Zwarts & Jansma. The use of physical laws for the design made a reduction of the magnetic field possible. Also, the visual impact on the surrounding landscape is reduced.[76567]

High voltage DC transmission pylons

High voltage direct current (HVDC) transmission lines are either monopolar or bipolar systems. With bipolar systems a conductor arrangement with one conductor on each side of the tower is used. For single-pole HVDC transmission with ground return, towers with only one conductor can be used. In many cases, however, the towers are designed for later conversion to a two-pole system. In these cases, conductors are installed on both sides of the tower for mechanical reasons. Until the second pole is needed, it is either grounded, or joined in parallel with the pole in use. In the latter case the line from the converter station to the earthing (grounding) electrode is built as underground cable.

Railway traction line pylons

Towers used for single phase AC railway traction lines are similar in construction to those towers used for 110 kV-three phase lines. Steel tube or concrete poles are also often used for these lines. However, railway traction current systems are two-pole AC systems, so traction lines are designed for two conductors (or multiples of two, usually four, eight, or twelve). As a rule, the towers of railway traction lines carry two electric circuits, so they have four conductors. These are usually arranged on one level, whereby each circuit occupies one half of the crossarm. For four traction circuits the arrangement of the conductors is in two-levels and for six electric circuits the arrangement of the conductors is in three levels.

With limited space conditions, it is possible to arrange the conductors of one traction circuit in two levels. Running a traction power line parallel to a high voltage transmission line for three-phase AC on a separate crossarm of the same tower is possible. If traction lines are led parallel to 380 kV-lines, the insulation must be designed for 220 kV, because in the event of a fault, dangerous overvoltages to the three-phase alternating current line can occur. Traction lines are usually equipped with one earth conductor. In Austria, on some traction circuits, two earth conductors are used.

Assembly

There are a variety of ways pylons can be assembled and erected:
  • They can be assembled horizontally on the ground and erected by push-pull cable. This method is rarely used, however, because of the large assembly area needed.
  • Gin pole crane: A gin pole crane can be used to assemble lattice towers.
  • Using a crane or using derrick.
  • Helicopter: In areas with very limited accessibility, such as mountains, assembly can be done using a helicopter.


Testing of mechanical properties

There are tower testing stations for testing the mechanical properties of towers.

Sign markings

Aside from the obligatory high voltage warning sign, electricity towers also frequently possess a sign or circuit identification plate, with the names of the line (either the terminal points of the line, or the internal designation of the power company) and the tower number. This makes identifying the location of a fault to the power company that owns the tower easier.

In some countries, require that lattice steel towers be equipped with a barbed wire barrier approximately above ground in order to deter unauthorized climbing. Such barriers can often be found on towers close to roads or other areas with easy public access, even where there is not a legal requirement. In the United Kingdommarker, all such towers are fitted with barbed wire.

Special designs

Antennas for low power FM radio, television, and mobile phone services are sometimes erected on pylons, especially on the steel masts carrying high voltage cables.

To build branches, quite impressive constructions must occasionally be used. This also applies occasionally to twisting masts that divert three-level conductor cables.

Sometimes (in particular on steel framework pylons for the highest voltage levels) transmitting plants are installed. Usually these installations are for mobile phone services or the operating radio of the power supply firm, but occasionally also for other radio services, like directional radio. Thus transmitting antennas for low-power FM radio and television transmitters were already installed on pylons. On the carrying pylon of the Elbe Crossing 1marker there is a radar facility belonging to the Hamburg water and navigation office.

For crossing broad valleys, a large distance between the conductor cables must be maintained to avoid short-circuits caused by conductor cables colliding during storms. Sometimes a separate pylon is used for each conductor. For crossing wide rivers and straits with flat coastlines very high pylons must be built, because a large height clearance is needed for navigation. Such masts must be equipped with flight safety lamps.
Two well-known wide river crossings are the Elbe Crossing 1marker and Elbe Crossing 2marker. The latter has the highest overhead line masts in Europe, at 227 meters tall. The overhead line crossing pylons in the Spanish bay of Cádizmarker have a particularly interesting construction. They consist of 158-meter-high carrying pylons with one cross beam atop a frustum framework construction. The longest overhead line spans are the crossing of the Norwegian Sognefjord (4,597 meters between two masts) and the Ameralik span in Greenland (5,376 meters.) In Germany the overhead line of the EnBW AG crossing of the Eyachtal has the longest span in the country at 1,444 meters.

In order to drop overhead lines into steep, deep valleys, inclined pylons are occasionally used. An example of this type of pylon is located at the Hoover dammarker in the USA. In Switzerland a NOK pylon inclined around 20 degrees to the vertical is located near Sargans. Highly sloping masts are used on two 380 kV pylons in Switzerland, the top 32 meters of one of them being bent by 18 degrees to the vertical.

Power station chimneys are sometimes equipped with crossbars for fixing conductors of the outgoing lines. Because of possible problems with corrosion by the flue gases, such constructions are very rare.

Types of pylons

Specific functions



Materials used



Conductor arrangements



Specific locations



Specific purposes



Pylons in art and culture



Alternatives to pylons

Pylons and the cables that they support are generally regarded to be unattractive and decrease the aesthetic value of the landscape and property values; a form of visual pollution. An alternative to pylons is underground cables. There are schemes in various countries to remove the pylons and undergrounding the cables, such as those in Europe. The US, however, continues to place most of its power lines above ground. Aside from the aesthetic value, some believe that overhead power lines are a security threat; a transmission line can be targeted by terrorists and taken out swiftly by attacking the towers. The lines being moved underground also reduces the chance of the power lines being affected by storms such as hurricanes and tornadoes, or other storms that are capable of knocking trees down on the main lines leaving substations. They also reduce the possibility of starting forest fires when the lines are broken.

One of the largest disadvantages involving burying underground cables is its cost. Some estimates state that the price can be raised by 4 to 10 times . Laying underground cables can be very expensive, especially in rocky terrain. Underground cables also have poor heat-dissipation qualities; unlike conductors suspended on towers, which are cooled by the air, the heat from underground transmission has nowhere to go and can cause damage to the cables. This can be addressed by pumping water or oil along the cable to cool it. The additional capacitance of the ground also results in less efficient power transmission. They are far more vulnerable to careless or inadvertent damage by third parties, often in the course of construction work. Burying cables also requires a large purchase of right-of-way for the transmission corridor just as pylons do; some estimates place this clearance as , about the size of a three- to four-lane road.

There is the option of burying a high-voltage direct current (HVDC) as opposed to an alternating current (AC) line. However, this is a possibility which will take some time to implement in the United States, as there are no manufacturers of the cables required for this.

Pylons of special interest

Pylon Year Country Town Pinnacle height Remarks
Yangtze River Crossing 2003 Chinamarker Jiangyin 346.5m Tallest pylons in the world
Yangtze River Crossing Nanjing 1992 Chinamarker Nanjing 257 m Tallest pylons in the world, built of reinforced concrete
Pylons of Pearl River Crossing 1987 Chinamarker 253 m + 240 m, 830 ft + 787 ft
Orinoco River Crossingmarker ? Venezuelamarker Caroní 240 m Tallest electricity pylons in South America
Pylons of Messina 1957 Italymarker Messinamarker 232 m ( 224 m without basement) no longer used as pylons
HVDC Yangtze River Crossing Wuhu 2003 Chinamarker Wuhu, Anhui Provincemarker 229 m Tallest electricity pylons used for HVDC
Elbe Crossing 2marker 1976-1978 Germanymarker Stademarker 227 m tallest electricity pylons in Europe
Chusi Powerline Crossing 1962 Japanmarker Chusi 226 m Tallest electricity pylons in Japan
Daqi-Channel-Crossing 1997 Japanmarker ? 223 m
Overhead line crossing Suez Canalmarker 1998 Egyptmarker 221 m
LingBei-Channel-Crossing 1993 Japanmarker ? 214.5 m
Kerinchi Pylonmarker 1999 Malaysiamarker Kerinchi near Kuala Lumpurmarker 210 m Tallest pylon in Southeast Asia
Luohe-Crossing 1989 Chinamarker ? 202.5 m pylons of reinforced concrete
380kV Thames Crossingmarker 1965 UKmarker West Thurrockmarker 190 m
Elbe Crossing 1marker 1958-1962 Germanymarker Stademarker 189 m
Tracy Saint Lawrence River Powerline Crossing ? Canada Tracy 174.6 m tallest electricity pylon in Canada
Bosporus overhead line crossing III 1999 Turkeymarker Istanbulmarker 160 m
Pylons of Cadizmarker 1955 Spainmarker Cadizmarker 158 m
Aust Severn Powerline Crossing ? UK Aust 148.75 m
132kV Thames Crossingmarker 1932 UKmarker West Thurrockmarker 148.4 m demolished in 1987
Karmsundet Powerline Crossing ? Norway Karmsundet 143.5 m
Limfjorden Overhead powerline crossing 2 ? Denmark Raerup 141.7 m
Saint Lawrence River HVDC Quebec-New England Overhead Powerline Crossing 1989 Canada Deschambault-Grondinesmarker 140 m dismantled in 1992
Pylons of Voerde 1926 Germanymarker Voerdemarker 138 m
Köhlbrand Powerline Crossing ? Germany Hamburg 138 m
Bremen-Farge Weser Powerline Crossing ? Germany Bremenmarker 135 m
Pylons of Ghesm Crossing 1984 Iranmarker Strait of Ghesm 130 m One pylon standing on a caisson in the sea
Shukhov tower on the Oka River 1929 Russiamarker Dzerzhinskmarker 128 m Hyperboloid structure
Tarchomin-Lomianki Vistula Powerline Crossing ? Polandmarker Tarchomin-Lomiankimarker 127 m ( Tarchomin), 121 m ( Lomianki)
Skolwin-Inoujście Odra Powerline Crossing ? Polandmarker Skolwin-Inoujściemarker 126 m ( Skolwin), 125 m ( Inoujście)
Enerhodar Dnipro Powerline Crossingmarker 2 1984 Ukrainemarker Enerhodarmarker 126 m Pylons on caissons
Bosporus overhead line crossing I 1957 Turkeymarker Istanbulmarker ?
Bosporus overhead line crossing II 1983 Turkeymarker Istanbulmarker ?
Little Belt Overhead powerline crossing 2marker ? Denmark Middelfart 125.3 m + 119.2 m
Duisburg-Wanheim Powerline Rhine Crossing ? Germanymarker Duisburgmarker 122 m
Little Belt Overhead powerline crossing 1marker ? Denmark Middelfart 119.5 m + 113.1 m
Pylons of Duisburg-Rheinhausen 1926 Germanymarker Duisburg-Rheinhausen 118.8 m
Bullenhausen Elbe Powerline Crossing ? Germany Bullenhausen 117 m
Lubaniew-Bobrowniki Vistula Powerline Crossing ? Poland Lubaniew/Bobrownikimarker 117 m
Ostrówek-Tursko Vistula Powerline Crossing ? Poland Ostrówek/Tursko 115 m
Riga Hydroelectric Power Plant Crossing Pylon 1974 Latviamarker Salaspilsmarker 112 m
Bremen-Industriehafen Weser Powerline Crossing 1972-1974 ( line for three phase AC) Germany Bremen 111 m two parallel running powerlines, one used for three phase AC, the other for traction current. Highest pylons designed for single phase AC use.
Nowy Bógpomóż-Probostwo Dolne Vistula Powerline Crossing ? Poland Nowy Bógpomóż/Probostwo Dolne 111 m ( Probostwo Dolne), 109 m ( Nowy Bógpomóż)
Daugava Powerline Crossing 1975 Latvia Rigamarker 110 m
Regów Gołąb Vistula Powerline Crossing ? Poland Regówmarker/Gołąb 108 m
Orsoy Rhine Crossing ? Germanymarker Orsoy 105 m
Limfjorden Overhead powerline crossing 1 ? Denmark Raerup 101.2 m
Enerhodar Dnipro Powerline Crossingmarker 1 1977 Ukrainemarker Enerhodarmarker 100 m Pylons on caissons
Reisholz Rhine Powerline Crossing 1917 Germany Düsseldorfmarker ? Under the legs of the pylon on the east shore of Rhine there runs the rail to nearby Holthausen substation
380kV-Ems-Overhead Powerline Crossingmarker ? Germany Mark (south of Weenermarker) 84 m
Pylon in the artificial lake of Santa Mariamarker 1959 Switzerlandmarker Lake of Santa Maria 75 m Pylon in an artificial lake
Leaning pylon of Mingjian ? Taiwanmarker Mingjian ? Earthquake memorial /www.flickr.com/photos/thenhbushman/2465773565/
Aggersund Crossing of Cross-Skagerak 1977 Denmark Aggersundmarker 70 m tallest pylons of an HVDC-line in Europe
Eyachtal Spanmarker 1992 Germanymarker Höfen 70 m Longest span of Germany ( 1444 metres)
Carquinez Strait Powerline Crossing 1901 United Statesmarker Beniciamarker 68 m + 20 m World's first powerline crossing of a larger waterway
Pylon 1 of powerline departing Reuter West Power Station ? Germanymarker Berlinmarker 66 m Chimney-like pylon with lattice steel crossbars
Pylon 310 of powerline Innertkirchen-Littau-Mettlen 1990 Switzerlandmarker Littaumarker 59,5 m Tallest pylon of prefabricated concrete
Anlage 2610, Mast 69 ? Germanymarker Bochummarker 47 m Pylon of 220kV-powerline decorated with balls in Ruhr-Park mall.
Colossus of Eislingen 1980 Germanymarker Eislingen/Fils 47 m Pylon standing over a little river
Source ? Francemarker Amnéville les Thermes 34 m / 28 m 4 pylons forming an artwork
Huddersfield Narrow Canal Pylonmarker ? UKmarker Stalybridge ? Pylon standing over Huddersfield Narrow Canalmarker, perhaps the only pylon whose legs can be passed under by boat


Gallery

File:pylon.detail.arp.750pix.jpg|Detail of the insulators (the vertical string of discs) and conductor vibration dampers (the weights attached directly to the conductors) on a 275,000 volt suspension tower near Thornburymarker, South Gloucestershire, Englandmarker, United KingdommarkerFile:Electric Sails.jpg|A tubular pylon, or muguet (lily) pylon, of an Hydro-Québec TransÉnergie line. These pylons are more visually appealing than their regular counterparts. The tubular pylons are used in urban settings, such as this one in Gatineau, Quebecmarker, Canadamarker, for high-voltage lines, from 110 to 315 kV.File:2610 69.JPG|Pylon decorated with balls in Ruhr Park, Bochummarker, GermanymarkerFile:Hudders Staly Pylon.jpg|Pylon straddling the Huddersfield Narrow Canalmarker in Stalybridgemarker, West Yorkshire, United Kingdommarker

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