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100-539: The span consists of four 40-millimeter diameter steel conductors, one of which is a spare. The span has a width of 190 metres and a minimum clearance of 128 metres. The pylons on each side of the span carry only one conductor each and are situated on mountains 444 metres high on the north shore and 1,013 metres high on the south shore. It is designed to withstand the cold winters of Greenland, so electricity produced can reach consumers without any disturbance. Download coordinates as: This Greenland -related article

200-402: A (nearly) continuous conductor running along the track that usually takes one of two forms: an overhead line , suspended from poles or towers along the track or from structure or tunnel ceilings, or a third rail mounted at track level and contacted by a sliding " pickup shoe ". Both overhead wire and third-rail systems usually use the running rails as the return conductor, but some systems use

300-573: A higher total efficiency. Electricity for electric rail systems can also come from renewable energy , nuclear power , or other low-carbon sources, which do not emit pollution or emissions. Electric locomotives may easily be constructed with greater power output than most diesel locomotives. For passenger operation it is possible to provide enough power with diesel engines (see e.g. ' ICE TD ') but, at higher speeds, this proves costly and impractical. Therefore, almost all high speed trains are electric. The high power of electric locomotives also gives them

400-467: A historical concern for double-stack rail transport regarding clearances with overhead lines but it is no longer universally true as of 2022 , with both Indian Railways and China Railway regularly operating electric double-stack cargo trains under overhead lines. Railway electrification has constantly increased in the past decades, and as of 2022, electrified tracks account for nearly one-third of total tracks globally. Railway electrification

500-554: A large height clearance for navigation. Such towers and the conductors they carry must be equipped with flight safety lamps and reflectors. Two well-known wide river crossings are the Elbe Crossing 1 and Elbe Crossing 2 . The latter has the tallest overhead line masts in Europe, at 227 m (745 ft) tall. In Spain, the overhead line crossing pylons in the Spanish bay of Cádiz have

600-443: 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. Indeed, for economic reasons, some transmission lines are designed for three (or four) circuits, but only two (or three) circuits are initially installed. 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

700-516: A lower cost than building a new transmission line. 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). These are usually arranged on one level, whereby each circuit occupies one half of

800-524: A number of European countries, India, Saudi Arabia, eastern Japan, countries that used to be part of the Soviet Union, on high-speed lines in much of Western Europe (including countries that still run conventional railways under DC but not in countries using 16.7   Hz, see above). Most systems like this operate at 25   kV, although 12.5   kV sections exist in the United States, and 20   kV

900-646: A particularly interesting construction. The main crossing towers are 158 m (518 ft) tall with one crossarm atop a frustum framework construction. The longest overhead line spans are the crossing of the Norwegian Sognefjord Span (4,597 m (15,082 ft) between two masts) and the Ameralik Span in Greenland (5,376 m (17,638 ft)). In Germany, the overhead line of the EnBW AG crossing of

1000-454: A power grid that is delivered to a locomotive, and within the locomotive, transformed and rectified to a lower DC voltage in preparation for use by traction motors. These motors may either be DC motors which directly use the DC or they may be three-phase AC motors which require further conversion of the DC to variable frequency three-phase AC (using power electronics). Thus both systems are faced with

1100-498: A relative lack of flexibility (since electric trains need third rails or overhead wires), and a vulnerability to power interruptions. Electro-diesel locomotives and electro-diesel multiple units mitigate these problems somewhat as they are capable of running on diesel power during an outage or on non-electrified routes. Different regions may use different supply voltages and frequencies, complicating through service and requiring greater complexity of locomotive power. There used to be

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1200-425: A result, transmission towers became politically important in the 2020s. Transmission tower is the name for the structure used in the industry in the United States and some other English-speaking countries. In Europe and the U.K., the terms electricity pylon and pylon derive from the basic shape of the structure, an obelisk with a tapered top. In Canada, the term hydrotower is used, because hydroelectricity

1300-481: A separate fourth rail for this purpose. In comparison to the principal alternative, the diesel engine , electric railways offer substantially better energy efficiency , lower emissions , and lower operating costs. Electric locomotives are also usually quieter, more powerful, and more responsive and reliable than diesel. They have no local emissions, an important advantage in tunnels and urban areas. Some electric traction systems provide regenerative braking that turns

1400-514: A steel plant in Piombino, Italy [4] and on a roof on an industrial building at Cherepovets, Russia at 59°8'52"N 37°51'55"E. Until 2015, on a residential highrise building in Dazhou, China at 31°11'28"N 107°30'43"E a powerline tower stood. Beside this, it is also possible that the lower parts of an electricity pylon stand in a building. Such a structure a person, who cannot have a view of the interior of

1500-418: A third rail. The key advantage of the four-rail system is that neither running rail carries any current. This scheme was introduced because of the problems of return currents, intended to be carried by the earthed (grounded) running rail, flowing through the iron tunnel linings instead. This can cause electrolytic damage and even arcing if the tunnel segments are not electrically bonded together. The problem

1600-429: A variety of ways they can then be assembled and erected: The International Civil Aviation Organization issues recommendations on markers for towers and the conductors suspended between them. Certain jurisdictions will make these recommendations mandatory, for example that certain power lines must have overhead wire markers placed at intervals, and that warning lights be placed on any sufficiently high towers, this

1700-426: A very small footprint and relies on guy wires in tension to support the structure and any unbalanced tension load from the conductors. A guyed tower can be made in a V shape, which saves weight and cost. Poles made of tubular steel generally are assembled at the factory and placed on the right-of-way afterward. Because of its durability and ease of manufacturing and installation, many utilities in recent years prefer

1800-578: Is a stub . You can help Misplaced Pages by expanding it . This article about electric power transmission is a stub . You can help Misplaced Pages by expanding it . Transmission tower A transmission tower (also electricity pylon , hydro tower , or pylon ) is a tall structure , usually a lattice tower made of steel that is used to support an overhead power line . In electrical grids , transmission towers carry high-voltage transmission lines that transport bulk electric power from generating stations to electrical substations , from which electricity

1900-549: Is a 61.3 m (201 ft) tall pylon of a 380 kV powerline near Reuter West Power Plant in Berlin. In China some pylons for lines crossing rivers were built of concrete. The tallest of these pylons belong to the Yangtze Powerline crossing at Nanjing with a height of 257 m (843 ft). Sometimes (in particular on steel lattice towers for the highest voltage levels) transmitting plants are installed, and antennas mounted on

2000-470: Is also used in environments that would be corrosive to steel. The extra material cost of aluminium towers will be offset by lower installation cost. Design of aluminium lattice towers is similar to that for steel, but must take into account aluminium's lower Young's modulus . A lattice tower is usually assembled at the location where it is to be erected. This makes very tall towers possible, up to 100 m (328 ft) (and in special cases even higher, as in

2100-652: Is delivered to end consumers; moreover, utility poles are used to support lower-voltage sub-transmission and distribution lines that transport electricity from substations to electricity customers. There are four categories of transmission towers: (i) the suspension tower , (ii) the dead-end terminal tower, (iii) the tension tower , and (iv) the transposition tower . The heights of transmission towers typically range from 15 to 55 m (49 to 180 ft), although when longer spans are needed, such as for crossing water, taller towers are sometimes used. More transmission towers are needed to mitigate climate change , and as

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2200-411: Is derived by using resistors which ensures that stray earth currents are kept to manageable levels. Power-only rails can be mounted on strongly insulating ceramic chairs to minimise current leak, but this is not possible for running rails, which have to be seated on stronger metal chairs to carry the weight of trains. However, elastomeric rubber pads placed between the rails and chairs can now solve part of

2300-451: Is effected by one contact shoe each that slide on top of each one of the running rails . This and all other rubber-tyred metros that have a 1,435 mm ( 4 ft  8 + 1 ⁄ 2  in ) standard gauge track between the roll ways operate in the same manner. Railways and electrical utilities use AC as opposed to DC for the same reason: to use transformers , which require AC, to produce higher voltages. The higher

2400-526: Is electrified, companies often find that they need to continue use of diesel trains even if sections are electrified. The increasing demand for container traffic, which is more efficient when utilizing the double-stack car , also has network effect issues with existing electrifications due to insufficient clearance of overhead electrical lines for these trains, but electrification can be built or modified to have sufficient clearance, at additional cost. A problem specifically related to electrified lines are gaps in

2500-486: Is limited and losses are significantly higher. However, the higher voltages used in many AC electrification systems reduce transmission losses over longer distances, allowing for fewer substations or more powerful locomotives to be used. Also, the energy used to blow air to cool transformers, power electronics (including rectifiers), and other conversion hardware must be accounted for. Standard AC electrification systems use much higher voltages than standard DC systems. One of

2600-490: Is limited to approximately 30 m (98 ft). Wood is rarely used for lattice framework. Instead, they are used to build multi-pole structures, such as H-frame and K-frame structures. The voltages they carry are also limited, such as in other regions, where wood structures only carry voltages up to approximately 30 kV. In countries such as Canada or the United States, wooden towers carry voltages up to 345 kV; these can be less costly than steel structures and take advantage of

2700-755: Is no longer exactly one-third of the grid frequency. This solved overheating problems with the rotary converters used to generate some of this power from the grid supply. In the US , the New York, New Haven, and Hartford Railroad , the Pennsylvania Railroad and the Philadelphia and Reading Railway adopted 11   kV 25   Hz single-phase AC. Parts of the original electrified network still operate at 25   Hz, with voltage boosted to 12   kV, while others were converted to 12.5 or 25   kV 60   Hz. In

2800-413: Is particularly true of transmission towers which are in close vicinity to airports . Railway electrification Railway electrification is the use of electric power for the propulsion of rail transport . Electric railways use either electric locomotives (hauling passengers or freight in separate cars), electric multiple units ( passenger cars with their own motors) or both. Electricity

2900-447: Is sufficient traffic, the reduced track and especially the lower engine maintenance and running costs exceed the costs of this maintenance significantly. Newly electrified lines often show a "sparks effect", whereby electrification in passenger rail systems leads to significant jumps in patronage / revenue. The reasons may include electric trains being seen as more modern and attractive to ride, faster, quieter and smoother service, and

3000-410: Is that the power-wasting resistors used in DC locomotives for speed control were not needed in an AC locomotive: multiple taps on the transformer can supply a range of voltages. Separate low-voltage transformer windings supply lighting and the motors driving auxiliary machinery. More recently, the development of very high power semiconductors has caused the classic DC motor to be largely replaced with

3100-850: Is the countrywide system. 3   kV DC is used in Belgium, Italy, Spain, Poland, Slovakia, Slovenia, South Africa, Chile, the northern portion of the Czech Republic, the former republics of the Soviet Union , and in the Netherlands on a few kilometers between Maastricht and Belgium. It was formerly used by the Milwaukee Road from Harlowton, Montana , to Seattle, across the Continental Divide and including extensive branch and loop lines in Montana, and by

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3200-565: Is the development of powering trains and locomotives using electricity instead of diesel or steam power . The history of railway electrification dates back to the late 19th century when the first electric tramways were introduced in cities like Berlin , London , and New York City . In 1881, the first permanent railway electrification in the world was the Gross-Lichterfelde Tramway in Berlin , Germany. Overhead line electrification

3300-717: Is the principal source of electricity for the country. 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. In some European countries, e.g. Germany, Spain or Czech Republic, smaller lattice towers are used for medium voltage (above 10 kV) transmission lines too. 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 Australia, Canada, Germany, and Scandinavia in some cases) and

3400-420: Is typically generated in large and relatively efficient generating stations , transmitted to the railway network and distributed to the trains. Some electric railways have their own dedicated generating stations and transmission lines , but most purchase power from an electric utility . The railway usually provides its own distribution lines, switches, and transformers . Power is supplied to moving trains with

3500-834: Is used on some narrow-gauge lines in Japan. On "French system" HSLs, the overhead line and a "sleeper" feeder line each carry 25   kV in relation to the rails, but in opposite phase so they are at 50   kV from each other; autotransformers equalize the tension at regular intervals. Various railway electrification systems in the late nineteenth and twentieth centuries utilised three-phase , rather than single-phase electric power delivery due to ease of design of both power supply and locomotives. These systems could either use standard network frequency and three power cables, or reduced frequency, which allowed for return-phase line to be third rail, rather than an additional overhead wire. The majority of modern electrification systems take AC energy from

3600-638: The Delaware, Lackawanna and Western Railroad (now New Jersey Transit , converted to 25   kV   AC) in the United States, and the Kolkata suburban railway (Bardhaman Main Line) in India, before it was converted to 25   kV 50   Hz. DC voltages between 600   V and 750   V are used by most tramways and trolleybus networks, as well as some metro systems as the traction motors accept this voltage without

3700-457: The Elbe crossing 1 and Elbe crossing 2 ). Assembly of lattice steel towers can be done using a crane . Lattice steel towers are generally made of angle-profiled steel beams (L-beam or T-beams ). For very tall towers, trusses are often used. Wood is a material which is limited in use in high-voltage transmission. Because of the limited height of available trees, the maximum height of wooden pylons

3800-683: The HSL-Zuid and Betuwelijn , and 3,000   V south of Maastricht . In Portugal, it is used in the Cascais Line and in Denmark on the suburban S-train system (1650   V DC). In the United Kingdom, 1,500   V   DC was used in 1954 for the Woodhead trans-Pennine route (now closed); the system used regenerative braking , allowing for transfer of energy between climbing and descending trains on

3900-450: The Hamburg water and navigation office. For crossing broad valleys, a large distance between the conductors must be maintained to avoid short-circuits caused by conductor cables colliding during storms. To achieve this, sometimes a separate mast or tower is used for each conductor. For crossing wide rivers and straits with flat coastlines, very tall towers must be built due to the necessity of

4000-674: The Innovia ART system. While part of the SkyTrain network, the Canada Line does not use this system and instead uses more traditional motors attached to the wheels and third-rail electrification. A few lines of the Paris Métro in France operate on a four-rail power system. The trains move on rubber tyres which roll on a pair of narrow roll ways made of steel and, in some places, of concrete . Since

4100-616: The Southern Railway serving Coulsdon North and Sutton railway station . The lines were electrified at 6.7   kV 25   Hz. It was announced in 1926 that all lines were to be converted to DC third rail and the last overhead-powered electric service ran in September 1929. AC power is used at 60   Hz in North America (excluding the aforementioned 25   Hz network), western Japan, South Korea and Taiwan; and at 50   Hz in

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4200-454: The United States , the New York, New Haven and Hartford Railroad was one of the first major railways to be electrified. Railway electrification continued to expand throughout the 20th century, with technological improvements and the development of high-speed trains and commuters . Today, many countries have extensive electrified railway networks with 375 000  km of standard lines in

4300-754: The Eyachtal has the longest span in the country at 1,444 m (4,738 ft). In order to drop overhead lines into steep, deep valleys, inclined towers are occasionally used. These are utilized at the Hoover Dam , located in the United States, to descend the cliff walls of the Black Canyon of the Colorado . In Switzerland, a pylon inclined around 20 degrees to the vertical is located near Sargans , St. Gallens . Highly sloping masts are used on two 380 kV pylons in Switzerland,

4400-684: The Netherlands, New Zealand ( Wellington ), Singapore (on the North East MRT line ), the United States ( Chicago area on the Metra Electric district and the South Shore Line interurban line and Link light rail in Seattle , Washington). In Slovakia, there are two narrow-gauge lines in the High Tatras (one a cog railway ). In the Netherlands it is used on the main system, alongside 25   kV on

4500-720: The UK, the London, Brighton and South Coast Railway pioneered overhead electrification of its suburban lines in London, London Bridge to Victoria being opened to traffic on 1   December 1909. Victoria to Crystal Palace via Balham and West Norwood opened in May 1911. Peckham Rye to West Norwood opened in June 1912. Further extensions were not made owing to the First World War. Two lines opened in 1925 under

4600-400: The United States . A lattice tower is a framework construction made of steel or aluminium sections. Lattice towers are used for power lines of all voltages, and are the most common type for high-voltage transmission lines. Lattice towers are usually made of galvanized steel. Aluminium is used for reduced weight, such as in mountainous areas where structures are placed by helicopter. Aluminium

4700-494: The ability to pull freight at higher speed over gradients; in mixed traffic conditions this increases capacity when the time between trains can be decreased. The higher power of electric locomotives and an electrification can also be a cheaper alternative to a new and less steep railway if train weights are to be increased on a system. On the other hand, electrification may not be suitable for lines with low frequency of traffic, because lower running cost of trains may be outweighed by

4800-516: The advantages of raising the voltage is that, to transmit certain level of power, lower current is necessary ( P = V × I ). Lowering the current reduces the ohmic losses and allows for less bulky, lighter overhead line equipment and more spacing between traction substations, while maintaining power capacity of the system. On the other hand, the higher voltage requires larger isolation gaps, requiring some elements of infrastructure to be larger. The standard-frequency AC system may introduce imbalance to

4900-454: The building, cannot distinguish from a real rooftop pylon. A structure of this type is Tower 9108 of a 110 kV high-voltage traction power line in Fulda [5] , File:Mast9108-Fundament.jpg . A new type of pylon, called Wintrack pylons, will be used in the Netherlands starting in 2010. The pylons were designed as a minimalist structure by Dutch architects Zwarts and Jansma. The use of physical laws for

5000-488: The cross arm. 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. Transmission towers must withstand various external forces, including wind, ice, and seismic activity, while supporting the weight of heavy conductors. Different shapes of transmission towers are typical for different countries. The shape also depends on voltage and number of circuits. Delta pylons are

5100-567: The design made a reduction of the magnetic field possible. Also, the visual impact on the surrounding landscape is reduced. Two clown-shaped pylons appear in Hungary, on both sides of the M5 motorway , near Újhartyán . The Pro Football Hall of Fame in Canton, Ohio, U.S., and American Electric Power paired to conceive, design, and install goal post -shaped towers located on both sides of Interstate 77 near

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5200-410: The distance they could transmit power. However, in the early 20th century, alternating current (AC) power systems were developed, which allowed for more efficient power transmission over longer distances. In the 1920s and 1930s, many countries worldwide began to electrify their railways. In Europe, Switzerland , Sweden , France , and Italy were among the early adopters of railway electrification. In

5300-448: The electrification. Electric vehicles, especially locomotives, lose power when traversing gaps in the supply, such as phase change gaps in overhead systems, and gaps over points in third rail systems. These become a nuisance if the locomotive stops with its collector on a dead gap, in which case there is no power to restart. This is less of a problem in trains consisting of two or more multiple units coupled together, since in that case if

5400-404: The end of funding. Most electrification systems use overhead wires, but third rail is an option up to 1,500   V. Third rail systems almost exclusively use DC distribution. The use of AC is usually not feasible due to the dimensions of a third rail being physically very large compared with the skin depth that AC penetrates to 0.3 millimetres or 0.012 inches in a steel rail. This effect makes

5500-571: The experiment was curtailed. In 1970 the Ural Electromechanical Institute of Railway Engineers carried out calculations for railway electrification at 12 kV DC , showing that the equivalent loss levels for a 25 kV AC system could be achieved with DC voltage between 11 and 16   kV. In the 1980s and 1990s 12 kV DC was being tested on the October Railway near Leningrad (now Petersburg ). The experiments ended in 1995 due to

5600-500: The fact that electrification often goes hand in hand with a general infrastructure and rolling stock overhaul / replacement, which leads to better service quality (in a way that theoretically could also be achieved by doing similar upgrades yet without electrification). Whatever the causes of the sparks effect, it is well established for numerous routes that have electrified over decades. This also applies when bus routes with diesel buses are replaced by trolleybuses. The overhead wires make

5700-592: The first major UK redesign since 1927, designed by Danish company Bystrup , winner of a 2011 competition from more than 250 entries held by the Royal Institute of British Architects and Her Majesty's Government . Y-pylons are a newer concept for electrical transmission towers. They usually have a guy-wire or support beam to help support the "Y" shape in the tower. Christmas-tree-shaped towers for 4 or even 6 circuits are common in Germany and have 3 cross arms where

5800-1012: The general power grid. This is especially useful in mountainous areas where heavily loaded trains must descend long grades. Central station electricity can often be generated with higher efficiency than a mobile engine/generator. While the efficiency of power plant generation and diesel locomotive generation are roughly the same in the nominal regime, diesel motors decrease in efficiency in non-nominal regimes at low power while if an electric power plant needs to generate less power it will shut down its least efficient generators, thereby increasing efficiency. The electric train can save energy (as compared to diesel) by regenerative braking and by not needing to consume energy by idling as diesel locomotives do when stopped or coasting. However, electric rolling stock may run cooling blowers when stopped or coasting, thus consuming energy. Large fossil fuel power stations operate at high efficiency, and can be used for district heating or to produce district cooling , leading to

5900-440: The ground. A semi-flexible tower is designed so that it can use overhead grounding wires to transfer mechanical load to adjacent structures, if a phase conductor breaks and the structure is subject to unbalanced loads. This type is useful at extra-high voltages, where phase conductors are bundled (two or more wires per phase). It is unlikely for all of them to break at once, barring a catastrophic crash or storm. A guyed mast has

6000-564: The hall as part of a power infrastructure upgrade. The Mickey pylon is a Mickey Mouse shaped transmission tower on the side of Interstate 4 , near Walt Disney World in Orlando, FL . Bog Fox is a design pylon in Estonia south of Risti at 58° 59′ 33.44″ N, 24° 3′ 33.19″ E. In Russia several pylons designed as artwork were built [6] Before transmission towers are even erected, prototype towers are tested at tower testing stations . There are

6100-411: The high cost of the electrification infrastructure. Therefore, most long-distance lines in developing or sparsely populated countries are not electrified due to relatively low frequency of trains. Network effects are a large factor with electrification. When converting lines to electric, the connections with other lines must be considered. Some electrifications have subsequently been removed because of

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6200-523: The highest arm has each one cable, the second has two cables and the third has three cables on each side. The cables on the third arm usually carry circuits for lower high voltage. Special designed pylons are necessary to introduce branching lines, e.g. to connect nearby substations. Towers may be self-supporting and capable of resisting all forces due to conductor loads, unbalanced conductors, wind and ice in any direction. Such towers often have approximately square bases and usually four points of contact with

6300-485: 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. Typically, one or two ground wires , also called "guard" wires, are placed on top to intercept lightning and harmlessly divert it to ground. Towers for high- and extra-high voltage are usually designed to carry two or more electric circuits. If

6400-492: The losses (saving 2   GWh per year per 100   route-km; equalling about €150,000 p.a.). The line chosen is one of the lines, totalling 6000   km, that are in need of renewal. In the 1960s the Soviets experimented with boosting the overhead voltage from 3 to 6   kV. DC rolling stock was equipped with ignitron -based converters to lower the supply voltage to 3   kV. The converters turned out to be unreliable and

6500-422: The maximum power that can be transmitted, also can be responsible for electrochemical corrosion due to stray DC currents. Electric trains need not carry the weight of prime movers , transmission and fuel. This is partly offset by the weight of electrical equipment. Regenerative braking returns power to the electrification system so that it may be used elsewhere, by other trains on the same system or returned to

6600-586: The most common design for single circuit lines, because of their stability. They have a V-shaped body with a horizontal arm on the top, which forms an inverted delta . Larger Delta towers usually use two guard cables. Portal pylons are widely used in the USA, Ireland, Scandinavia and Canada. They stand on two legs with one cross arm, which gives them a H-shape. Up to 110 kV they often were made from wood, but higher voltage lines use steel pylons. Smaller single circuit pylons may have two small cross arms on one side and one on

6700-402: The need for overhead wires between those stations. Maintenance costs of the lines may be increased by electrification, but many systems claim lower costs due to reduced wear-and-tear on the track from lighter rolling stock. There are some additional maintenance costs associated with the electrical equipment around the track, such as power sub-stations and the catenary wire itself, but, if there

6800-490: The other. One level pylons only have one cross arm carrying 3 cables on each side. Sometimes they have an additional cross arm for the protection cables. They are frequently used close to airports due to their reduced height. Danube pylons or Donaumasten got their name from a line built in 1927 next to the Danube river . They are the most common design in central European countries like Germany or Poland. They have two cross arms,

6900-497: The phase separation between the electrified sections powered from different phases, whereas high voltage would make the transmission more efficient. UIC conducted a case study for the conversion of the Bordeaux-Hendaye railway line (France), currently electrified at 1.5   kV DC, to 9   kV DC and found that the conversion would allow to use less bulky overhead wires (saving €20 million per 100   route-km) and lower

7000-583: The pole in use. In the latter case, the line from the converter station to the earthing (grounding) electrode is built as underground cable, as overhead line on a separate right of way or by using the ground conductors. Electrode line towers are used in some HVDC schemes to carry the power line from the converter station to the grounding electrode. They are similar to structures used for lines with voltages of 10–30 kV, but normally carry only one or two conductors. AC transmission towers may be converted to full or mixed HVDC use, to increase power transmission levels at

7100-500: The problem by insulating the running rails from the current return should there be a leakage through the running rails. The Expo and Millennium Line of the Vancouver SkyTrain use side-contact fourth-rail systems for their 650 V DC supply. Both are located to the side of the train, as the space between the running rails is occupied by an aluminum plate, as part of stator of the linear induction propulsion system used on

7200-733: The public grid or for the railway traction current grid. Concrete poles for medium-voltage are also used in Canada and the United States. In Switzerland, concrete pylons with heights of up to 59.5 metres (world's tallest pylon of prefabricated concrete at Littau ) are used for 380 kV overhead lines. In Argentina and some other south american countries, many overhead power lines, except the ultra-high voltage grid, were placed on tubular concrete pylons. Also in former soviet countries, concrete pylons are common, though with crossarms made of steel. Concrete pylons, which are not prefabricated, are also used for constructions taller than 60 metres. One example

7300-454: The pylons in order to prevent electrochemical corrosion of the pylons. 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, often conductors on both sides of the tower are installed for mechanical reasons. Until the second pole is needed, it is either used as electrode line or joined in parallel with

7400-451: The realization of overhead 400/230 volt grids for the power supply of homes [1] . However, there are also roof-mounted support structures for high-voltage. Some thermal power plants in Poland like Połaniec Power Station and in the former Soviet Union like Lukoml Power Station use portal pylons on the roof of the power station building for the high voltage line from the machine transformer to

7500-460: The resistance per unit length unacceptably high compared with the use of DC. Third rail is more compact than overhead wires and can be used in smaller-diameter tunnels, an important factor for subway systems. The London Underground in England is one of few networks that uses a four-rail system. The additional rail carries the electrical return that, on third-rail and overhead networks, is provided by

7600-570: The revenue obtained for freight and passenger traffic. Different systems are used for urban and intercity areas; some electric locomotives can switch to different supply voltages to allow flexibility in operation. Six of the most commonly used voltages have been selected for European and international standardisation. Some of these are independent of the contact system used, so that, for example, 750   V   DC may be used with either third rail or overhead lines. There are many other voltage systems used for railway electrification systems around

7700-490: The running rails. On the London Underground, a top-contact third rail is beside the track, energized at +420 V DC , and a top-contact fourth rail is located centrally between the running rails at −210 V DC , which combine to provide a traction voltage of 630 V DC . The same system was used for Milan 's earliest underground line, Milan Metro 's line 1 , whose more recent lines use an overhead catenary or

7800-464: The same task: converting and transporting high-voltage AC from the power grid to low-voltage DC in the locomotive. The difference between AC and DC electrification systems lies in where the AC is converted to DC: at the substation or on the train. Energy efficiency and infrastructure costs determine which of these is used on a network, although this is often fixed due to pre-existing electrification systems. Both

7900-516: The same towers is common. Sometimes, especially with 110 kV circuits, a parallel circuit carries traction lines for railway electrification . 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. On some schemes, the ground conductor is used as electrode line or ground return. In this case, it had to be installed with insulators equipped with surge arrestors on

8000-405: The same width. In 2021 the first T-pylon, a new tubular T-shaped design, was installed in United Kingdom for a new power line to Hinkley Point C nuclear power station , carrying two high voltage 400 kV power lines. The design features electricity cables strung below a cross-arm atop a single pole which reduces the visual impact on the environment compared to lattice pylons. These 36 T-pylons were

8100-555: The steep approaches to the tunnel. The system was also used for suburban electrification in East London and Manchester , now converted to 25   kV   AC. It is now only used for the Tyne and Wear Metro . In India, 1,500   V DC was the first electrification system launched in 1925 in Mumbai area. Between 2012 and 2016, the electrification was converted to 25   kV 50   Hz, which

8200-443: The supply grid, requiring careful planning and design (as at each substation power is drawn from two out of three phases). The low-frequency AC system may be powered by separate generation and distribution network or a network of converter substations, adding the expense, also low-frequency transformers, used both at the substations and on the rolling stock, are particularly bulky and heavy. The DC system, apart from being limited as to

8300-506: The surge voltage insulating properties of wood. As of 2012 , 345 kV lines on wood towers are still in use in the US and some are still being constructed on this technology. Wood can also be used for temporary structures while constructing a permanent replacement. Concrete pylons are used in Germany normally only for lines with operating voltages below 30 kV. In exceptional cases, concrete pylons are used also for 110 kV lines, as well as for

8400-510: The switchyard. Also other industrial buildings may have a rooftop powerline support structure. One can find such a device at a steel work in Dnipro, Ukraine at 48°28'57"N 34°58'43"E and at a steel work in Freital, Germany at 50°59'53"N 13°38'26"E. In the United States such device may be more common as in other countries [2] , [3] There are also real rooftop high voltage towers on industry buildings as at

8500-694: The three-phase induction motor fed by a variable frequency drive , a special inverter that varies both frequency and voltage to control motor speed. These drives can run equally well on DC or AC of any frequency, and many modern electric locomotives are designed to handle different supply voltages and frequencies to simplify cross-border operation. Five European countries – Germany, Austria, Switzerland, Norway and Sweden – have standardized on 15   kV 16 + 2 ⁄ 3   Hz (the 50   Hz mains frequency divided by three) single-phase AC. On 16 October 1995, Germany, Austria and Switzerland changed from 16 + 2 ⁄ 3   Hz to 16.7   Hz which

8600-575: The through traffic to non-electrified lines. If through traffic is to have any benefit, time-consuming engine switches must occur to make such connections or expensive dual mode engines must be used. This is mostly an issue for long-distance trips, but many lines come to be dominated by through traffic from long-haul freight trains (usually running coal, ore, or containers to or from ports). In theory, these trains could enjoy dramatic savings through electrification, but it can be too costly to extend electrification to isolated areas, and unless an entire network

8700-442: 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 flue gases, such constructions are very rare. There exist also a variety of pylons and powerline poles mounted on buildings. The most common forms are small rooftop poles used in some countries like Germany for

8800-412: The top above or below the overhead ground wire . 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 Elbe Crossing 1 tower, there is a radar facility belonging to

8900-466: The train stops with one collector in a dead gap, another multiple unit can push or pull the disconnected unit until it can again draw power. The same applies to the kind of push-pull trains which have a locomotive at each end. Power gaps can be overcome in single-collector trains by on-board batteries or motor-flywheel-generator systems. In 2014, progress is being made in the use of large capacitors to power electric vehicles between stations, and so avoid

9000-713: The train's kinetic energy back into electricity and returns it to the supply system to be used by other trains or the general utility grid. While diesel locomotives burn petroleum products, electricity can be generated from diverse sources, including renewable energy . Historically, concerns of resource independence have played a role in the decision to electrify railway lines. The landlocked Swiss confederation which almost completely lacks oil or coal deposits but has plentiful hydropower electrified its network in part in reaction to supply issues during both World Wars. Disadvantages of electric traction include: high capital costs that may be uneconomic on lightly trafficked routes,

9100-413: The transmission and conversion of electric energy involve losses: ohmic losses in wires and power electronics, magnetic field losses in transformers and smoothing reactors (inductors). Power conversion for a DC system takes place mainly in a railway substation where large, heavy, and more efficient hardware can be used as compared to an AC system where conversion takes place aboard the locomotive where space

9200-470: The tyres do not conduct the return current, the two guide bars provided outside the running ' roll ways ' become, in a sense, a third and fourth rail which each provide 750 V DC , so at least electrically it is a four-rail system. Each wheel set of a powered bogie carries one traction motor . A side sliding (side running) contact shoe picks up the current from the vertical face of each guide bar. The return of each traction motor, as well as each wagon ,

9300-416: The upper arm carries one and the lower arm carries two cables on each side. Sometimes they have an additional cross arm for the protection cables. Ton shaped towers are the most common design, they have 3 horizontal levels with one cable very close to the pylon on each side. In the United Kingdom the second level is often (but not always) wider than the other ones while in the United States all cross arms have

9400-416: The use of monopolar steel or concrete towers over lattice steel for new power lines and tower replacements. In Germany steel tube pylons are also established predominantly for medium voltage lines, in addition, for high voltage transmission lines or two electric circuits for operating voltages by up to 110 kV. Steel tube pylons are also frequently used for 380 kV lines in France , and for 500 kV lines in

9500-432: The voltage, the lower the current for the same power (because power is current multiplied by voltage), and power loss is proportional to the current squared. The lower current reduces line loss, thus allowing higher power to be delivered. As alternating current is used with high voltages. Inside the locomotive, a transformer steps the voltage down for use by the traction motors and auxiliary loads. An early advantage of AC

9600-405: The weight of an on-board transformer. Increasing availability of high-voltage semiconductors may allow the use of higher and more efficient DC voltages that heretofore have only been practical with AC. The use of medium-voltage DC electrification (MVDC) would solve some of the issues associated with standard-frequency AC electrification systems, especially possible supply grid load imbalance and

9700-532: The world, and the list of railway electrification systems covers both standard voltage and non-standard voltage systems. The permissible range of voltages allowed for the standardised voltages is as stated in standards BS   EN   50163 and IEC   60850. These take into account the number of trains drawing current and their distance from the substation. 1,500   V DC is used in Japan, Indonesia, Hong Kong (parts), Ireland, Australia (parts), France (also using 25 kV 50 Hz AC ) ,

9800-527: The world, including China , India , Japan , France , Germany , and the United Kingdom . Electrification is seen as a more sustainable and environmentally friendly alternative to diesel or steam power and is an important part of many countries' transportation infrastructure. Electrification systems are classified by three main parameters: Selection of an electrification system is based on economics of energy supply, maintenance, and capital cost compared to

9900-437: Was exacerbated because the return current also had a tendency to flow through nearby iron pipes forming the water and gas mains. Some of these, particularly Victorian mains that predated London's underground railways, were not constructed to carry currents and had no adequate electrical bonding between pipe segments. The four-rail system solves the problem. Although the supply has an artificially created earth point, this connection

10000-543: Was first applied successfully by Frank Sprague in Richmond, Virginia in 1887-1888, and led to the electrification of hundreds of additional street railway systems by the early 1890s. The first electrification of a mainline railway was the Baltimore and Ohio Railroad's Baltimore Belt Line in the United States in 1895–96. The early electrification of railways used direct current (DC) power systems, which were limited in terms of

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