Overhead line crossing
An overhead line crossing is the crossing of an obstacle (traffic route, river, valley or strait) by an overhead line .
The execution of an overhead line crossing depends heavily on the local conditions and the regulations for the line construction in force at the time of construction , as well as on the regulations for crossing traffic routes. For example, when shipping lanes cross, the clearance height is paramount. However, overhead line crossings are carried out similarly in many comparable cases.
Overhead line crossings can in some cases make complex constructions necessary and also have operational disadvantages. In such cases, it should be considered whether it is more economical to design the crossing of the obstacle as underground or submarine cables . Also Tunnel (and culverts ) provide an opportunity to the underpass of rivers with cables. Bridges can carry overhead line masts (such as Storstrømsbroen or the Cologne South Bridge ) and also have cable ducts.
Types of overhead line crossings
Roads and railway lines
Overhead line crossings of roads, railway lines, small and medium-sized watercourses nowadays generally do not require any special structures. In the early years of overhead line construction (1910s / 1920s), however, it was a requirement that a protective bridge had to be built under the line at crossings of traffic routes . Later, to cross an overhead line with a state railway line, a guy mast had to be erected on both sides of the line , which can be seen particularly well on some of the older overhead lines still in existence, such as the north-south line .
For overhead line crossings on motorways and expressways, the overhead line masts sometimes have to be renewed prematurely, as there are increased static requirements for them. Often, however, the routes of roads or railway lines get in the way of existing older masts, for which new constructions are built a little further away. It also happens that the masts on both sides of the road have to be raised later in order to maintain the safety distance. Alternatively, underground cables are used - mostly for medium-voltage lines.
If the local conditions make it appear appropriate, an overhead line can also be crossed by a valley bridge. For example, the Körschtal viaduct crosses a two-circuit 110 kV three-phase power line from EnBW AG. For obvious reasons, such as the risk of short circuits from falling objects, one tries to avoid such crossings. Further examples are the Brenztalbrücke , the Siegtalbrücke , the Dambachtal bridge or the Maintalbrücke Gemünden . The Fuldatalbrücke Morschen even crosses two 110 kV and one 20 kV overhead lines.
At highway Behelfsflugplätzen overhead lines are often used as underground cable laid or guided around the umfunktionierbare for runway pavement. In the area of road crossing, low single-level masts are used, which are often marked as an aviation obstacle.
Railway lines used to have to be crossed with two guy masts. This is also the case with the Rankbachbahn , which the north-south line built in 1929 at Magstadt crosses.
The north-south line crosses the A 6 east of a former temporary motorway airport on very low single-level masts.
A 110 kV overhead line runs under the Brenz Valley Bridge near Giengen .
State borders
State borders, especially when the line sections on both sides of the border are operated by different energy supply companies, are often crossed with a span that consists of a guy mast on each side of the border. This reduces maintenance work that would require direct coordination of workers on both sides of the border to an absolute minimum and avoids any competence problems for the cross-border line section as much as possible.
In the case of lines that cross a state border, but not as a coupling line, but purely as a transit line, only in sections on foreign national territory, the masts usually do not change. Examples are the Dutch 150 kV line between Roermond and Heerlen , which runs through the Heinsberg district, or the French 220 kV line Saint-Avold –Bruch in the Saarland .
When crossing the former inner-German border , different pylons were used on both sides.
Other overhead lines
When overhead lines cross each other, the necessary mutual safety distances and the safety distances to the ground must be observed. As a rule, the line with the lower voltage is usually passed under the line with the higher voltage. Basically, one tries to plan such intersections in such a way that their realization takes place with the least possible financial effort. This is usually achieved by leaving the line to be crossed as unchanged as possible. However, if this line is to be crossed by the new line to be built, a possibly existing earth wire is often lowered to the level of the top traverse in the crossing area in order to reduce the height of the masts of the line to be crossed.
If the new pipeline to be built crosses under an existing pipeline, attempts are often made to achieve this in the vicinity of masts of this pipeline, since in this case the necessary safety clearances with respect to the ground and the other pipelines are often guaranteed without increasing the existing masts. When crossing under , the mast pattern is often changed and because of the low height of the line crossing under , the one- level arrangement of the conductor cables is preferred.
When crossing lines, problems may arise due to the maximum mast height given for reasons of flight safety, as the masts sometimes have to be increased later. The mast of the 380 kV Pulverdingen - Hoheneck line , which is located immediately north of the intersection with the 380 kV Rommerskirchen – Bürstadt – Hoheneck line , is 108.5 m high and thus the highest overhead line mast in Baden-Württemberg . It can be easily recognized from the nearby A 81 .
Another possibility is the erection of a mast, which takes the circuits of both crossing lines. If necessary, it can also be used to link both lines or as a junction mast .
If it is not possible to achieve the required overall height at one of the masts locations of the crossing line, this is wired or driven to lower mast heights in the area of the crossing section with the line. In Great Britain in particular, underground cabling of crossing overhead lines is widespread.
An unusual type of crossover of overhead lines exists north of Kincardine in Scotland . Here the high-voltage line Kincardine-Tealing passes under two other high-voltage lines. One of the circuits of the Kincardine-Tealing line passes under these lines as an overhead line on low masts, the other as an underground cable.
Crossing of two 380 kV lines between Ludwigsburg and Freiberg / Neckar. The four-circuit 380 kV line Hoheneck-Pulverdingen crosses the two-circuit 380 kV line Hoheneck-Bürstadt. A two-circuit 220 kV line runs parallel to the 380 kV Hoheneck-Pulverdingen line and runs under the 380 kV Hoheneck-Bürstadt line.
Aerial ropeways
Overhead lines should, if at all, only cross the route of a cable car above it.
The necessary protective distances from overhead lines to the ropes of a cable car can be found in the relevant regulations regarding the construction of cable cars and overhead lines. If the cable car is crossed under a cable car, the necessary safety clearances between the overhead line and the floor of the cable car cabin must be guaranteed, even in the worst case. Basically, both crossings and undercrossings are fully regulated by the relevant regulations.
However, special precautionary measures are often taken in the area of the intersection. At overhead line crossings where the overhead line runs above the cables of the cable car, two safety cables are occasionally attached to prevent the conductor cable from falling onto the cable car in the event of a break in the overhead line mast or the fastening insulator. Alternatively, auxiliary trusses can also be mounted on the overhead line masts under the conductor cables, which prevent the conductor cables from falling onto the cableway route. Occasionally the span of the line over the cable car is scaffolded with a rigid construction over its entire length or at least in the area of the cable car. This version can be found, for example, on the Caracas cable car .
At crossings where the overhead line runs underneath the cable car's support cables, the line is often laid on special masts in the crossing area, which scaffold the line in the area of the cable car crossing. Such a measure is not necessarily required by the relevant regulations for overhead line construction, but in the event of an accident it enables people to be rescued from the cable car without the overhead line having to be disconnected. Such constructions can be found at 110 kV overhead line crossings of the Penkenbahn in Mayrhofen , the Patscherkofelbahn near Innsbruck and south of Zermatt .
A 110 kV overhead line crosses the local mountain railway in Garmisch-Partenkirchen as an underground cable .
Temporary protective structures
If the overhead line under construction crosses a railway line, cable car, road or other overhead line, it must be ensured that hanging ropes do not obstruct traffic; that they do not come into contact with cables that are already live, which would result in a short circuit. Therefore a wooden frame is built over the lower obstacle.
Broad rivers and straits
Overhead line crossings of wide rivers and straits often consist of four masts, if the terrain on both banks is relatively flat: two guy masts of particularly massive construction to brace the crossing section and two high masts to ensure the necessary cable height above the respective water body. These masts are equipped with wider cross members and larger cross member spacings than the other masts of the line in order to prevent the conductor cables from knocking against each other even in strong winds.
In contrast to normal overhead line masts, the two support masts on both sides of the intersection are often marked as a flight safety obstacle and can be climbed via stairs. Not least because of this, they are often particularly impressive and eye-catching structures. The pylons of Elbe crossing 2 are the highest overhead line pylons in Germany and Europe with a height of 227 m.
Overhead line crossings of rivers and straits with widths of more than two kilometers are often uneconomical and very unfavorable under operational conditions, because because of the risk of wind-induced vibratory movements of the conductor cables, very large conductor spacings must be selected or insulating spacers must be installed in the span between the phases. Since the bundle conductors that are consistently used in high-voltage lines tend to vibrate much more than single conductors, they cannot be used in many cases, which means that the crossing section may become the section that determines the maximum load capacity of the line. Another problem arises from the fact that, for economic and licensing reasons, the masts at the two ends of the crossing section cannot be built as high as you want, but on the other hand a considerable minimum height of the line often has to be observed due to shipping traffic, which is why there is a high tension in the conductor cable occurs with large spans. Only ropes with a high steel content can cope with this tensile stress, but with the same weight they have poorer electrical conductivity than the usual conductor ropes made of copper , Aldrey or aluminum-coated steel, which also leads to an impairment of the electrical load capacity. For this reason, in bodies of water over two kilometers wide, it should always be checked whether the crossing line can be designed as a cable laid in the water ( submarine cable ), which is the only practicable solution for bodies of water over five kilometers wide.
If the waterway to be crossed is not too deep, one or more overhead line masts can be erected on caissons in the waterway. One example that has been carried out is the overhead line crossing of Lake Maracaibo .
The approval of such constructions is very problematic in navigable waters because overhead line masts erected in the water represent dangerous obstacles for shipping, especially in fog.
If necessary, small masts or cross girders can be installed on the bridge body to accommodate conductor cables on a bridge that crosses said body of water. A solution of this kind, which is likely to cause safety problems, especially in bridge maintenance, was implemented at Storstrømsbroen in Denmark. The south bridge in Cologne also carries an overhead line; it is the Cologne – Sindorf traction power line completed in 2002 .
Incidentally, it is quite possible that overhead line crossings of wide bodies of water are replaced by cables laid in the water. The overhead line crossing of the Strait of Messina , which with a span of 3646 meters was one of the longest overhead line crossings and its crossing masts with a height of 200 meters were among the highest high-voltage pylons in the world, was replaced by a submarine cable because of their low electrical load capacity.
If overhead lines that have such an intersection have to be renewed, sometimes only the tip of the intersection pylons is replaced in order to avoid the complex and costly demolition of the old and construction of completely new overhead line pylons.
The Elbe Crossing 2 at Stade uses the highest pylons in Europe.
The overhead line crossing near Duisburg-Rheinhausen is realized by unconventional masts .
A delta mast of a single-circuit 110-kV overhead line is located in Lake Schwerin . The water is crossed north of the Paulsdamm .
For the Voerde overhead line crossing , the mast tips were renewed due to age-related wear; the lower masts were preserved.
Guy mast with eight- fold insulators at the crossing of the Usk estuary
Examples
- High voltage line to Zhoushan Island
- Yangtze overhead line crossing
- Yangtze overhead line crossing Nanking
- Yangtze overhead line crossing Wuhu
- Pearl River overhead line crossing
- Orinoco overhead line crossing
- Elbe & Köhlbrand , currently the three highest overhead line crossings in Germany
- Chusi overhead line crossing
- Overhead line crossing of the Suez Canal
- Overhead line crossing of the Ling-Bei Canal
- Luohe overhead line crossing
- Volga overhead line crossing Balakowo
- The highest pipeline in Europe over the Vorab glacier , see preliminary derivation
- Overhead lines across the Bosporus
- Overhead line crossing of the Strait of Messina (closed)
- Overhead line crossing of the St. Lawrence River Tracy
- Scheldt overhead line crossing Doel
- Overhead line crossing of the Bay of Cadiz
- Limfjord overhead line crossing 1
- Limfjord overhead line crossing 2
- Karmsund overhead line crossing
- Overhead line crossing of the Saint Lawrence River of the HVDC Québec – New England (dismantled)
- Rhine overhead line crossing Koblenz-Niederwerth-Urbar
- Rhine overhead line crossing Reisholz
- Rhine overhead line crossing Voerde
- Weser overhead line crossing Bremen-Farge
- Overhead line crossing of the Oka near Dzerzhinsk
- Dnepr overhead line crossing Energodar
- Overhead line crossing of the Rhine near Duisburg - Rheinhausen
- Vistula overhead line crossing Tarchomin-Lomianki
- Skolwin-Inoujście overhead line crossing
- Vistula overhead line crossing Lubaniew-Bobrowniki
- Vistula overhead line crossing Świeże Górne-Rybakow
- Vistula overhead line crossing Ostrówek-Tursko
- Vistula overhead line crossing Nowy Bógpomóż-Probostwo Dolne
- Vistula overhead line crossing Regów-Gołąb
- Overhead line crossing Klaipeda-Curonian Spit (Lithuanian part)
- Elbe overhead line crossing Bullenhausen
- Overhead line crossings of the Little Belt (dismantled)
- Weser crossings Bremen industrial port
- Swine overhead line crossing Swinoujscie
- Strelasund overhead line crossing
- Overhead line crossing Peenestrom Karnin
- Overhead line crossing of the Peene near Karlshagen
- Overhead line crossing Khortytsia on the east bank of the Dnieper
- Aggersund overhead line crossing of the HVDC Cross-Skagerrak
- Overhead line crossing over the Weisstannental (see 380 kV line Sils-Fällanden )
- Overhead line crossing over the Furkareuss valley between Andermatt and Realp (see Gotthard line )
- 380 kV Ems overhead line crossing
- Masts of the Pearl River overhead line crossing
- Masts of the Ghesm overhead line crossing
- 380 kV Thames overhead line crossing
- Severn overhead line crossing Aust
- Daugava overhead line crossing
- Overhead line crossing of Carquinez Street
Valleys
Overhead line crossings of valleys consist of two guy masts on both sides of the valley. If the topography of the valley is suitable, these need not be very high. In the case of very wide valleys, it is advantageous to provide a separate mast for each phase in order to achieve a sufficient distance between the conductors. In these cases there is often another guy mast behind them to change the angle of the conductors. The problems with large spans mentioned in the last section naturally also exist in these cases, but if a suitable topography does not require high crossing masts, an almost unlimited distance between the conductors can be achieved very economically by using a separate mast for each phase.
The Kocher valley is crossed by a 380/110 kV overhead line near Morsbach.
A 20 kV medium voltage line crosses the Glattbachtal near Großglattbach
Examples
- Overhead line crossing of Ameralik Fjord on Greenland, over 5 km - longest span
- Overhead line crossing of the Sognefjord , Norway, over 4 km
- Spanning the Eyach Valley ( Annex 615 )
- Spanning the Enz Valley near Bad Wildbad
- Spanning the Nagold Valley near Bad Liebenzell
- Spanning the Weisstannental
- Rhine overhead line crossing Hirzenach-Oberkestert
Individual evidence
- ↑ The "Freiberg Riese" - the highest overhead line mast in Baden-Württemberg (height: 108.5 meters). In: www.strassenkatalog.de. Retrieved October 20, 2016 .