High voltage AC transmission towers
Electricity pylons over water, near Darwin, Northern Territory, Australia
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 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 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 pylon 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.
High voltage DC transmission pylons
HVDC Distance Pylon near the terminus of the Nelson River Bipole adjacent to Dorsey Converter Station near Rosser, Manitoba, Canada August 2005
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
Tension tower with phase transposition of a powerline for single phase AC traction current (110 kV, 16.67 Hz) near Bartholom, Germany
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.
This section requires expansion.
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.
Tower Identification Tag on HVDC anchor pylon at Dorsey Converter Station near Rosser, Manitoba, Canada August 2005
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 3 metres (9.8 ft) 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 Kingdom, all such towers are fitted with barbed wire.
Hyperboloid pylon in the suburb of Nizhniy Novgorod, Russia.
Antennas for low power FM radio, television, and mobile phone services are sometimes erected on pylons, especially on the steel towers carrying high voltage cables.
To build branches, quite impressive constructions must occasionally be used. This also applies occasionally to twisting towers 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 1 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.
One of the Pylons of Cdiz, Spain
Two well-known wide river crossings are the Elbe Crossing 1 and Elbe Crossing 2. The latter has the highest overhead line masts in Europe, at 227 meters tall. The overhead line crossing pylons in the Spanish bay of Cdiz 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 dam 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
Anchor pylons (also called strainer pylons or terminal towers) are used at the endpoints of straight runs of conductors. They utilize tension insulators to carry the horizontal tension of the long stretch of line.
pine pylon an electricity pylon for two circuits of three-phase AC current, a which the conductors are arranged in three levels. In pine pylons the lowest crossbar has a wider span than that in the middle and this one a larger span than that on the top.
Transposing pylons are anchor or terminal pylons at which the conductors are "transposed" so that they exchange sides of the pylon.
Long-distance anchor pylon
Steel tube pylon
Lattice steel pylon
Concrete filled steel tube pylon
Three level pylon
bridge mounted structures, as on Storstrm Bridge
Rail current pylon
Pylons in art and culture
The North Korean coat of arms, bearing a pylon in the center.
In the 1998 film Among Giants, a pylon at grid reference SD833152 in Ashworth Valley, near Rochdale, Greater Manchester, England, was painted pink for the movie. The pylon was demolished in 2003.
In Ruhrpark, a big mall in Bochum, Germany, there is a pylon decorated with balls.
The North Korean official emblem has a pylon and a dam on it.
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 30 to 50 feet (9.1 to 15 m), 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. Furthermore terminals of high-voltage direct current-systems are expensive and have no remarkable overload capacity. Beside this, there are additional losses in the inverter plants and it is difficult to operate HVDC systems with more than 2 terminals. Until now, HVDC is nearly always used for applications where an AC solution would be impossible or a technical bad solution. In fact, HVDC Kingsnorth an HVDC cable system for feeding the inner part of London, UK was replaced after 12 years by an AC system. Although HVDC is well suited for cable transmission and often used for submarine power cables, there are also many HVDC overhead lines ( see List of HVDC projects).
Pylons of special interest
Yangtze River Crossing
Tallest pylons in the world
Yangtze River Crossing Nanjing
Tallest pylons in the world, built of reinforced concrete
Pylons of Pearl River Crossing
253 m + 240 m, 830 ft + 787 ft
Orinoco River Crossing
Tallest electricity pylons in South America
Pylons of Messina
232 m ( 224 m without basement)
no longer used as pylons
HVDC Yangtze River Crossing Wuhu
Wuhu, Anhui Province
Tallest electricity pylons used for HVDC
Elbe Crossing 2
tallest electricity pylons in Europe
Chusi Powerline Crossing
Tallest electricity pylons in Japan
Overhead line crossing Suez Canal
Kerinchi near Kuala Lumpur
Tallest pylon in Southeast Asia
pylons of reinforced concrete
380kV Thames Crossing
Elbe Crossing 1
Tracy Saint Lawrence River Powerline Crossing
tallest electricity pylon in Canada
Bosporus overhead line crossing III
Pylons of Cadiz
Aust Severn Powerline Crossing
132kV Thames Crossing
demolished in 1987
Karmsundet Powerline Crossing
Limfjorden Overhead powerline crossing 2
Saint Lawrence River HVDC Quebec-New England Overhead Powerline Crossing
dismantled in 1992
Pylons of Voerde
Khlbrand Powerline Crossing
Bremen-Farge Weser Powerline Crossing
Pylons of Ghesm Crossing
Strait of Ghesm
One pylon standing on a caisson in the sea
Shukhov tower on the Oka River
Tarchomin-Lomianki Vistula Powerline Crossing
127 m ( Tarchomin), 121 m ( Lomianki)
Skolwin-Inoujcie Odra Powerline Crossing
126 m ( Skolwin), 125 m ( Inoujcie)
Enerhodar Dnipro Powerline Crossing 2
Pylons on caissons
Bosporus overhead line crossing I
Bosporus overhead line crossing II
Little Belt Overhead powerline crossing 2
125.3 m + 119.2 m
Duisburg-Wanheim Powerline Rhine Crossing
Little Belt Overhead powerline crossing 1
119.5 m + 113.1 m
Pylons of Duisburg-Rheinhausen
Bullenhausen Elbe Powerline Crossing
Lubaniew-Bobrowniki Vistula Powerline Crossing
Ostrwek-Tursko Vistula Powerline Crossing
Riga Hydroelectric Power Plant Crossing Pylon
Bremen-Industriehafen Weser Powerline Crossing
1972-1974 ( line for three phase AC)
two parallel running powerlines, one used for three phase AC, the other for traction current. Highest pylons designed for single phase AC use.
Nowy Bgpom-Probostwo Dolne Vistula Powerline Crossing
Nowy Bgpom/Probostwo Dolne
111 m ( Probostwo Dolne), 109 m ( Nowy Bgpom)
Daugava Powerline Crossing
Regw Gob Vistula Powerline Crossing
Orsoy Rhine Crossing
Limfjorden Overhead powerline crossing 1
Enerhodar Dnipro Powerline Crossing 1
Pylons on caissons
Reisholz Rhine Powerline Crossing
Under the legs of the pylon on the east shore of Rhine there runs the rail to nearby Holthausen substation
380kV-Ems-Overhead Powerline Crossing
Mark (south of Weener)
Pylon in the artificial lake of Santa Maria
Lake of Santa Maria
Pylon in an artificial lake
Leaning pylon of Mingjian
Aggersund Crossing of Cross-Skagerak
tallest pylons of an HVDC-line in Europe
Longest span of Germany ( 1444 metres)
Carquinez Strait Powerline Crossing
68 m + 20 m
World's first powerline crossing of a larger waterway
Pylon 1 of powerline departing Reuter West Power Station
Chimney-like pylon with lattice steel crossbars
Pylon 310 of powerline Innertkirchen-Littau-Mettlen
Tallest pylon of prefabricated concrete
Anlage 2610, Mast 69
Pylon of 220kV-powerline decorated with balls in Ruhr-Park mall.
Colossus of Eislingen
Pylon standing over a little river
Amnville les Thermes
34 m / 28 m
4 pylons forming an artwork
Huddersfield Narrow Canal Pylon
Pylon standing over Huddersfield Narrow Canal, perhaps the only pylon whose legs can be passed under by boat
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 Thornbury, South Gloucestershire, England, United Kingdom
A tubular pylon, or muguet (lily) pylon, of an Hydro-Qubec Transnergie 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, Quebec, Canada, for high-voltage lines, from 110 to 315 kV.
Pylon decorated with balls in Ruhr Park, Bochum, Germany
Pylon straddling the Huddersfield Narrow Canal in Stalybridge, West Yorkshire, United Kingdom
Double-circuit transmission line
List of spans
^ Broadcast Tower Technologies. "Gin Pole Services". http://www.tower-technologies.com/GinPole.htm. Retrieved 2009-10-24.
^ Pylon ZP226 at Structurae
^ American Transmission Company (2009). "Underground Transmission Lines". http://www.atcllc.com/IT5.shtml. Retrieved 2009-10-24.
^ a b Allegheny Energy, Inc. (2009). "Out of Sight, Out of Mind? Obstacles to Burying the TrAIL". http://www.aptrailinfo.com/downloads/propertyowners/One Page - Underground.pdf. Retrieved 2009-10-24.
Wikimedia Commons has media related to: Pylons
Flash Bristow's pylon photo gallery and pylon FAQ
Pictures of Pylons and technical information
Pylon Photographs and Art
Pylons in Russia and other areas of former Soviet Union
Images of new Dutch high voltage pylon, Zwarts & Jansma Architects
Collection of some electricity pylons on Skyscraperpage.com
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