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Electricity Pylon

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.

Assembly

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.

Sign markings

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.

Special designs

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

Specific functions

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

Branch pylon

Anchor portal

Materials used

Wood pylon

Concrete pylon

Steel tube pylon

Lattice steel pylon

Concrete filled steel tube pylon

Stobie pole

Conductor arrangements

Portal pylon

Delta pylon

Single-level pylon

Two-level pylon

Three level pylon

Barrel pylon

Specific locations

Roof stand

Crossing pylon

bridge mounted structures, as on Storstrm Bridge

Specific purposes

Rail current pylon

Hybrid pylon

Utility pole

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

Pylon

Year

Country

Town

Pinnacle height

Remarks

Yangtze River Crossing

2003

China

Jiangyin

346.5m

Tallest pylons in the world

Yangtze River Crossing Nanjing

1992

China

Nanjing

257 m

Tallest pylons in the world, built of reinforced concrete

Pylons of Pearl River Crossing

1987

China

253 m + 240 m, 830 ft + 787 ft

Orinoco River Crossing

Venezuela

Caron

240 m

Tallest electricity pylons in South America

Pylons of Messina

1957

Italy

Messina

232 m ( 224 m without basement)

no longer used as pylons

HVDC Yangtze River Crossing Wuhu

2003

China

Wuhu, Anhui Province

229 m

Tallest electricity pylons used for HVDC

Elbe Crossing 2

1976-1978

Germany

Stade

227 m

tallest electricity pylons in Europe

Chusi Powerline Crossing

1962

Japan

Chusi

226 m

Tallest electricity pylons in Japan

Daqi-Channel-Crossing

1997

Japan

223 m

Overhead line crossing Suez Canal

1998

Egypt

221 m

LingBei-Channel-Crossing

1993

Japan

214.5 m

Kerinchi Pylon

1999

Malaysia

Kerinchi near Kuala Lumpur

210 m

Tallest pylon in Southeast Asia

Luohe-Crossing

1989

China

202.5 m

pylons of reinforced concrete

380kV Thames Crossing

1965

West Thurrock

190 m

Elbe Crossing 1

1958-1962

Germany

Stade

189 m

Tracy Saint Lawrence River Powerline Crossing

Canada

Tracy

174.6 m

tallest electricity pylon in Canada

Bosporus overhead line crossing III

1999

Turkey

Istanbul

160 m

Pylons of Cadiz

1955

Spain

Cadiz

158 m

Aust Severn Powerline Crossing

Aust

148.75 m

132kV Thames Crossing

1932

West Thurrock

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-Grondines

140 m

dismantled in 1992

Pylons of Voerde

1926

Germany

Voerde

138 m

Khlbrand Powerline Crossing

Germany

Hamburg

138 m

Bremen-Farge Weser Powerline Crossing

Germany

Bremen

135 m

Pylons of Ghesm Crossing

1984

Iran

Strait of Ghesm

130 m

One pylon standing on a caisson in the sea

Shukhov tower on the Oka River

1929

Russia

Dzerzhinsk

128 m

Hyperboloid structure

Tarchomin-Lomianki Vistula Powerline Crossing

Poland

Tarchomin-Lomianki

127 m ( Tarchomin), 121 m ( Lomianki)

Skolwin-Inoujcie Odra Powerline Crossing

Poland

Skolwin-Inoujcie

126 m ( Skolwin), 125 m ( Inoujcie)

Enerhodar Dnipro Powerline Crossing 2

1984

Ukraine

Enerhodar

126 m

Pylons on caissons

Bosporus overhead line crossing I

1957

Turkey

Istanbul

Bosporus overhead line crossing II

1983

Turkey

Istanbul

Little Belt Overhead powerline crossing 2

Denmark

Middelfart

125.3 m + 119.2 m

Duisburg-Wanheim Powerline Rhine Crossing

Germany

Duisburg

122 m

Little Belt Overhead powerline crossing 1

Denmark

Middelfart

119.5 m + 113.1 m

Pylons of Duisburg-Rheinhausen

1926

Germany

Duisburg-Rheinhausen

118.8 m

Bullenhausen Elbe Powerline Crossing

Germany

Bullenhausen

117 m

Lubaniew-Bobrowniki Vistula Powerline Crossing

Poland

Lubaniew/Bobrowniki

117 m

Ostrwek-Tursko Vistula Powerline Crossing

Poland

Ostrwek/Tursko

115 m

Riga Hydroelectric Power Plant Crossing Pylon

1974

Latvia

Salaspils

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 Bgpom-Probostwo Dolne Vistula Powerline Crossing

Poland

Nowy Bgpom/Probostwo Dolne

111 m ( Probostwo Dolne), 109 m ( Nowy Bgpom)

Daugava Powerline Crossing

1975

Latvia

Riga

110 m

Regw Gob Vistula Powerline Crossing

Poland

Regw/Gob

108 m

Orsoy Rhine Crossing

Germany

Orsoy

105 m

Limfjorden Overhead powerline crossing 1

Denmark

Raerup

101.2 m

Enerhodar Dnipro Powerline Crossing 1

1977

Ukraine

Enerhodar

100 m

Pylons on caissons

Reisholz Rhine Powerline Crossing

1917

Germany

Dsseldorf

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

Germany

Mark (south of Weener)

84 m

Pylon in the artificial lake of Santa Maria

1959

Switzerland

Lake of Santa Maria

75 m

Pylon in an artificial lake

Leaning pylon of Mingjian

Taiwan

Mingjian

Earthquake memorial

Aggersund Crossing of Cross-Skagerak

1977

Denmark

Aggersund

70 m

tallest pylons of an HVDC-line in Europe

Eyachtal Span

1992

Germany

Hfen

70 m

Longest span of Germany ( 1444 metres)

Carquinez Strait Powerline Crossing

1901

United States

Benicia

68 m + 20 m

World’s first powerline crossing of a larger waterway

Pylon 1 of powerline departing Reuter West Power Station

Germany

Berlin

66 m

Chimney-like pylon with lattice steel crossbars

Pylon 310 of powerline Innertkirchen-Littau-Mettlen

1990

Switzerland

Littau

59,5 m

Tallest pylon of prefabricated concrete

Anlage 2610, Mast 69

Germany

Bochum

47 m

Pylon of 220kV-powerline decorated with balls in Ruhr-Park mall.

Colossus of Eislingen

1980

Germany

Eislingen/Fils

47 m

Pylon standing over a little river

Source

France

Amnville les Thermes

34 m / 28 m

4 pylons forming an artwork

Huddersfield Narrow Canal Pylon

Stalybridge

Pylon standing over Huddersfield Narrow Canal, perhaps the only pylon whose legs can be passed under by boat

Gallery

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

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