用户:JC1/twenty-second
电塔，又名输电塔，是用来承托架空电缆的结构物，通常为钢制铁塔-。输电网络中的输电系统主要用于大规模从发电厂输送电力至负载中心，使用架空电缆相对地底电缆成本较低，故需要输电塔将电缆抬高以避免高压电力影响地面活动。较低电压的配电系统的则常用电线杆作支撑物。电塔有各种不同形状和大小，高度通常为15至55米之间[1]，但最高可见于舟山岛架空电缆，当中有两座370米高的输电塔。除钢铁以外，亦有见以混凝土或木材作为建筑材料。
电塔可主要分为四大类：悬吊塔、终端塔、张力塔以及转置塔[1]。有些电塔则同时有以上数项塔种的功能。电塔和架空电缆为一种视觉污染，故亦为管线地下化的其中一种理由。
High voltage AC transmission towers
三相电 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 桁架 (工程)es (wooden structures are used in Canada, Germany, and 斯堪的纳维亚 in some cases) and the insulators are either glass or porcelain discs or composite insulators using silicone rubber or EPDM rubber material assembled in strings or long rods whose lengths are dependent on the line voltage and environmental conditions.
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 (with very rare exceptions, only one circuit for 500-kV and higher).[来源请求] 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. 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 the same towers is common. Sometimes, especially with 110 kV circuits, a parallel circuit carries traction lines for 电气化铁路.
High voltage DC transmission towers
高压直流输电 (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 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 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 a lower cost than building a new transmission line.[2][3]
Railway traction line towers
Towers used for single-phase AC 铁路运输 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 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.
Towers for different types of currents
AC circuits of different frequency and phase-count, or AC and DC circuits, may be installed on the same tower. Usually all circuits of such lines have voltages of 50 kV and more. However, there are some lines of this type for lower voltages. For example, towers used by both railway traction power circuits and the general three-phase AC grid.
Two very short sections of line carry both AC and DC power circuits. One set of such towers is near the terminal of HVDC Volgograd-Donbass on Volga Hydroelectric Power Station. The other are two towers south of Stenkullen, which carry one circuit of HVDC Konti-Skan and üne circuit of the three-phase AC line Stenkullen-Holmbakullen.
Towers carrying AC circuits and DC electrode lines exist in a section of the powerline between Adalph Static Inverter Plant and Brookston the pylons carry the electrode line of HVDC Square Butte.
The electrode line of HVDC CU at the converter station at Coal Creek Station uses on a short section the towers of two AC lines as support.
The overhead section of the electrode line of Pacific DC Intertie from Sylmar Converter Station to the grounding electrode in the Pacific Ocean near Will Rogers State Beach is also installed on AC pylons. It runs from Sylmar East Converter Station to Southern California Edison Malibu Substation, where the overhead line section ends.
In Germany, Austria and Switzerland some transmission towers carry both public AC grid circuits and railway traction power in order to better use rights of way.
Tower designs
Shape
Different shapes of transmission towers are typical for different countries. The shape also depends on voltage and number of circuits.
One circuit
Delta pylons are 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 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 the other.
Two circuits
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 多瑙河. They are the most common design in central European countries like Germany or Poland. They have two cross arms, 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 the same width.
Four circuits
Christmas-tree-shaped towers for 4 or even 6 circuits are common in Germany and have 3 cross arms where 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.
Support structures
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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 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 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.[4]
Materials
Tubular steel
Poles made of tubular 钢 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 the use of monopolar steel or concrete towers over lattice steel for new power lines and tower replacements. [来源请求]
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 the United States.
Lattice
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 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 杨氏模量.
A lattice tower is usually assembled at the location where it is to be erected. This makes very tall towers possible, up to 100米（328英尺） (and in special cases even higher, as in 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- or T-beams). For very tall towers, 桁架 (工程)es are often used.
Wood
木材 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 is limited to approximately 30米（98英尺）. 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 the surge voltage insulating properties of wood.[4] 截至2012年[update], 345 kV lines on wood towers are still in use in the US and some are still being constructed on this technology.[5][6] Wood can also be used for temporary structures while constructing a permanent replacement.
Concrete
混凝土 pylons are used in 德国国名 normally only for lines with operating 电压s below 30 kV. In exceptional cases, concrete pylons are used also for 110 kV lines, as well as for the public grid or for the 铁路运输 traction current grid. In Switzerland, concrete pylons with heights of up to 59.5 metres (world's tallest pylon of prefabricated concrete at 利陶) are used for 380 kV overhead lines. Concrete poles are also used in Canada and the United States.
Concrete pylons, which are not prefabricated, are also used for constructions taller than 60 metres. One example is a 66米（217英尺） tall pylon of a 380 kV powerline near Reuter West Power Plant in Berlin. Such pylons look like industrial chimneys.[来源请求] 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米（843英尺）.
Special designs
Sometimes (in particular on steel lattice towers for the highest voltage levels) transmitting plants are installed, and antennas mounted on 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 the 汉堡 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 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米（745英尺） tall. In Spain, the overhead line crossing pylons in the Spanish bay of Cádiz have a particularly interesting construction. The main crossing towers are 158米（518英尺） tall with one crossarm atop a 锥台 framework construction. The longest overhead line spans are the crossing of the Norwegian Sognefjord (4,597米（15,082英尺） between two masts) and the Ameralik Span in Greenland (5,376米（17,638英尺）). In Germany, the overhead line of the EnBW AG crossing of the Eyachtal has the longest span in the country at 1,444米（4,738英尺）.
In order to drop overhead lines into steep, deep valleys, inclined towers are occasionally used. These are utilized at the 胡佛水坝, 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 萨甘斯, St. Gallens. 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 flue gases, such constructions are very rare.
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 the design made a reduction of the magnetic field possible. Also, the visual impact on the surrounding landscape is reduced.[7]
Two clown-shaped pylons appear in Hungary, on both sides of the M5 motorway, near 乌伊豪尔詹.[8]
The Pro Football Hall of Fame in Canton, Ohio, U.S., and 美国电力公司 paired to conceive, design, and install goal post-shaped towers located on both sides of Interstate 77 near the hall as part of a power infrastructure upgrade.[9]
The Mickey Pylon is a 米老鼠 shaped transmission tower on the side of 4号州际公路, near 华特迪士尼世界度假区 in 奥兰多 (佛罗里达州).
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128 meters high Hyperboloid pylon in Russia -
River 易北河 Crossing 2 in Germany -
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Wintrack pylons in the Netherlands -
The Mickey Pylon in Florida, U.S.
Assembly
Before transmission towers are even erected, prototype towers are tested at tower testing stations. There are a variety of ways they can then be assembled and erected:
- They can be assembled horizontally on the ground and erected by push-pull cable. This method is rarely used because of the large assembly area needed.
- They can be assembled vertically (in their final upright position). Very tall towers, such as the Yangtze River Crossing, were assembled in this way.
- A jin-pole crane can be used to assemble lattice towers.[10] This is also used for 电线杆s.
- 直升机s can serve as aerial cranes for their assembly in areas with limited accessibility. Towers can also be assembled elsewhere and flown to their place on the transmission right-of-way.[11] Helicopters may also be used for transporting disassembled towers for scrapping.[12]
Markers
The 国际民用航空组织 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,[13] this is particularly true of transmission towers which are in close vicinity to 机场s.
Electricity pylons often have an identification tag marked with the name 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.
Transmission towers, much like other steel lattice towers including broadcasting or cellphone towers, are marked with signs which discourage public access due to the danger of the high voltage. Often this is accomplished with a sign warning of the high voltage. At other times, the entire access point to the transmission corridor is marked with a sign.
Tower functions
Tower structures can be classified by the way in which they support the line conductors.[14] Suspension structures support the conductor vertically using suspension insulators. Strain structures resist net tension in the conductors and the conductors attach to the structure through strain insulators. Dead-end structures support the full weight of the conductor and also all the tension in it, and also use strain insulators.
Structures are classified as tangent suspension, angle suspension, tangent strain, angle strain, tangent dead-end and angle dead-end.[4] Where the conductors are in a straight line, a tangent tower is used. Angle towers are used where a line must change direction.
Cross arms and conductor arrangement
Generally three conductors are required per AC 3-phase circuit, although single-phase and DC circuits are also carried on towers. Conductors may be arranged in one plane, or by use of several cross-arms may be arranged in a roughly symmetrical, triangulated pattern to balance the impedances of all three phases. If more than one circuit is required to be carried and the width of the line right-of-way does not permit multiple towers to be used, two or three circuits can be carried on the same tower using several levels of cross-arms. Often multiple circuits are the same voltage, but mixed voltages can be found on some structures.
Other features
Insulators
Insulators electrically isolate the live side of the transmission cables from the tower structure and earth. They are either glass or porcelain discs or composite insulators using silicone rubber or EPDM rubber material. They are assembled in strings or long rods whose lengths are dependent on the line voltage and environmental conditions. By using disks the shortest surface electrical path between the ends is maximised which reduces the chance of a leakage in moist conditions.
Stockbridge dampers
Stockbridge dampers are added to the transmission lines a meter or two from the tower. They consist of a short length of cable clamped in place parallel to the line itself and weighted at each end. The size and dimensions are carefully designed to damp any buildup of mechanical oscillation of the lines that could be induced by mechanical vibration most likely that caused by wind. Without them its possible for a standing wave to become established that grows in magnitude and destroys the line or the tower.
Arcing horns
Arcing horns are sometimes added to the ends of the insulators in areas where voltage surges may occur. These may be caused by either lightning strikes or in switching operations. They protect power line insulators from damage due to arcing. They can be seen as rounded metal pipework at either end of the insulator and provide a path to earth in extreme circumstances without damaging the insulator.
Physical security
Towers will have a level of physical security to prevent members of the public or climbing animals from ascending them. This may take the form of a security fence or climbing baffles added to the supporting legs. Some countries require that lattice steel towers be equipped with a 有刺铁丝网 barrier approximately 3米（9.8英尺） 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.
参见
References
- ^ 1.0 1.1 Environmental, Health, and Safety Guidelines for Electric Power Transmission and Distribution (PDF). International Finance Corporation: 21. 2007-04-30 [2013-09-15].
- ^ Convert from AC to HVDC for higher power transmission. ABB Review. 2018: 64–69 [20 June 2020].
- ^ Liza Reed; Granger Morgan; Parth Vaishnav; Daniel Erian Armanios. Converting existing transmission corridors to HVDC is an overlooked option for increasing transmission capacity. Proceedings of the National Academy of Sciences. 9 July 2019, 116 (28): 13879–13884. PMC 6628792
. PMID 31221754. doi:10.1073/pnas.1905656116.
- ^ 4.0 4.1 4.2 Donald Fink and Wayne Beaty (ed.) Standard Handbook for Electrical Engineers 11th Ed., Mc Graw Hill, 1978, ISBN 0-07-020974-X, pp. 14-102 and 14-103
- ^ http://www.spta.org/pdf/Reisdorff%20Lam%20%209-11.pdf
- ^ Olive Development. Winterport, Maine.
- ^ New High Voltage Pylons for the Netherlands. 2009 [2010-04-24].
- ^ Clown-shaped High Voltage Pylons in Hungary.47°14′09″N 19°23′27″E / 47.2358442°N 19.3907302°E
- ^ Rudell, Tim. Drive Through Goal Posts at the Pro Football Hall of Fame. WKSU. 2016-06-28 [2019-07-14].40°49′03″N 81°23′48″W / 40.8174274°N 81.3966678°W
- ^ Broadcast Tower Technologies. Gin Pole Services. [2009-10-24].
- ^ Powering Up – Vertical Magazine. verticalmag.com. [4 October 2015]. （原始内容存档于4 October 2015）.
- ^ Helicopter Transport of Transmission Towers. Transmission & Distribution World. 21 May 2018.
- ^ Chapter 6. Visual aids for denoting obstacles (PDF). Annex 14 Volume I Aerodrome design and operations. 国际民用航空组织: 6–3, 6–4, 6–5. 2004-11-25 [1 June 2011].
6.2.8 ... spherical ... diameter of not less than 60 cm. ... 6.2.10 ... should be of one colour. ... Figure 6-2 ... 6.3.13
- ^ American Society of Civil Engineers Design of latticed steel transmission structures ASCE Standard 10-97, 2000, ISBN 0-7844-0324-4, section C2.3
External links
- Pylon Appreciation Society
- Flash Bristow's pylon photo gallery and pylon FAQ
- Magnificent Views: Pictures of High Voltage Towers (also offers technical information)
- Structurae database of select notable transmission towers
- Pylons in Russia and other areas of former Soviet Union
- Meet the 'pylon spotters' – BBC News
