Depending on the method of hanging wires, overhead line (OHL) supports are divided into two main groups:
A) intermediate supports, on which the wires are fixed in supporting clamps,
b) anchor type supports, used for tensioning wires. On these supports, the wires are secured in tension clamps.
The distance between supports (power lines) is called span, and the distance between anchor-type supports is called anchored area(Fig. 1).
In accordance with the intersection of some engineering structures, such as railways public use, must be performed on anchor-type supports. At the angles of rotation of the line, corner supports are installed on which the wires can be suspended in support or tension clamps. Thus, the two main groups of supports - intermediate and anchor - are divided into types that have a special purpose.
Rice. 1. Scheme of the anchored section of the overhead line
Intermediate straight supports installed on straight sections of the line. On intermediate supports with hanging insulators, the wires are secured in supporting garlands hanging vertically; on intermediate supports with pin insulators, the wires are secured with wire knitting. In both cases, intermediate supports perceive horizontal loads from wind pressure on the wires and on the support, and vertical loads from the weight of the wires, insulators and the own weight of the support.
With unbroken wires and cables, intermediate supports, as a rule, do not take the horizontal load from the tension of the wires and cables in the direction of the line and therefore can be made of a lighter structure than supports of other types, for example, end supports that take the tension of the wires and cables. However, to ensure reliable operation line intermediate supports must withstand some loads in the direction of the line.
Intermediate corner supports are installed at the angles of rotation of the line with wires suspended in supporting garlands. In addition to the loads acting on intermediate straight supports, intermediate and anchor corner supports also absorb loads from the transverse components of the tension of wires and cables.
At power line rotation angles of more than 20°, the weight of the intermediate corner supports increases significantly. Therefore, intermediate corner supports are used for angles up to 10 - 20°. For large rotation angles, install anchor corner supports.
Rice. 2. Intermediate supports for overhead lines
Anchor supports. On lines with suspended insulators, the wires are secured in the clamps of tension garlands. These garlands are like a continuation of the wire and transfer its tension to the support. On lines with pin insulators, the wires are secured to anchor supports with reinforced ties or special clamps that ensure the transfer of the full tension of the wire to the support through the pin insulators.
When installing anchor supports on straight sections of the route and suspending wires on both sides of the support with equal tensions, the horizontal longitudinal loads from the wires are balanced and the anchor support works in the same way as an intermediate one, i.e., it perceives only horizontal transverse and vertical loads.
Rice. 3. Anchor-type overhead line supports
If necessary, the wires on one and the other side of the anchor support can be pulled with different tension, then the anchor support will perceive the difference in tension of the wires. In this case, in addition to horizontal transverse and vertical loads, the support will also be affected by horizontal longitudinal load. When installing anchor supports at corners (at the turning points of the line), the anchor corner supports also take the load from the transverse components of the tension of wires and cables.
End supports are installed at the ends of the line. Wires extend from these supports and are suspended on substation portals. When hanging wires on the line before the construction of the substation is completed, the end supports perceive full one-way tension.
In addition to the listed types of supports, special supports are also used on lines: transpositional, used to change the order of arrangement of wires on supports, branch lines - to make branches from the main line, supports large crossings across rivers and water bodies, etc.
The main type of supports on overhead lines are intermediate, the number of which is usually 85-90% total number supports
Based on their design, supports can be divided into: free-standing And guyed supports. Guys are usually made of steel cables. Wooden, steel and reinforced concrete supports are used on overhead lines. Support designs made of aluminum alloys have also been developed.
Overhead line support structures
- Wooden support of the 6 kV LOP (Fig. 4) - single-column, intermediate. Made from pine, sometimes larch. The stepson is made of impregnated pine. For 35-110 kV lines, wooden U-shaped two-post supports are used. Additional items support structures: hanging garland with hanging clamp, traverse, braces.
- Reinforced concrete supports are made as single-column free-standing ones, without guys or with guys on the ground. The support consists of a post (trunk) made of centrifuged reinforced concrete, a traverse, a lightning protection cable with a grounding conductor on each support (for lightning protection of the line). Using a grounding pin, the cable is connected to a ground electrode (a conductor in the form of a pipe driven into the ground next to the support). The cable serves to protect lines from direct lightning strikes. Other elements: stand (barrel), rod, traverse, cable support.
- Metal (steel) supports (Fig. 5) are used at voltages of 220 kV and more.
Power transmission lines (PTL) are one of the most important components of modern electrical network. A power transmission line is a system of energy equipment that extends beyond power plants and is designed for the remote transmission of electricity through electric current.
Power lines are divided into cable and overhead. Cable a power transmission line is a power transmission line made by one or more cables laid directly into the ground, cable ducts, pipes, or onto cable structures. Air power line (VL) is a device designed for transmission and distribution electrical energy via wires that are in the open air.
For the installation of overhead power lines, special structures are used - overhead power line supports. Power transmission line supports are special structures designed to hold the wires of overhead power lines at a given distance from the surface of the earth and from each other.
The system of overhead power transmission towers was developed at the beginning of the twentieth century, when the first powerful power plants began to appear, and it became possible to transmit electricity over long distances. Until the mid-twentieth century, rolling out wires for power transmission line supports took place on the ground. But this method of rolling had many disadvantages: the wire dragged along the ground received numerous damages and required repairs during the installation process. Small scratches and chips became the cause of corona discharge, leading to losses of transmitted energy.
In the fifties of the twentieth century in Europe it was developed special method installation of electrical wires - the so-called traction method. The pulling method involves rolling out the wire directly onto installed power line supports using special rollers, without lowering the wire to the ground. A tension machine is installed at one end of the overhead line, and a brake machine at the other. Thanks to this method, during the construction of power lines, the possibility of damage to electrical wires was significantly reduced and repair costs were reduced, which, in turn, led to a reduction in losses of transmitted electricity. Advantage this method is also expressed in the fact that the presence of natural (rivers, lakes, forests, mountains, etc.) and artificial (roads, railways, buildings, etc.) barriers facilitates and speeds up the installation of power lines. In Russia, the technology for installing power line supports “under tension” has been used since 1996 and at the moment is the most expedient and popular way of constructing overhead power line supports.
IN modern construction Power line supports are also used as supports for holding grounded lightning rods and fiber optic communication lines. They are also used to illuminate spaces on highways, streets, squares, etc. in the dark. Overhead line supports are designed for the construction of power lines at a design outdoor temperature of up to -65˚C inclusive.
The supports are divided into two main groups, depending on the method of hanging the wires:
- intermediate power transmission line supports. The wires on these supports are secured in supporting clamps;
- anchor type supports. The wires on anchor-type supports are secured in tension clamps. These supports are used for tensioning wires.
Two main groups are divided into types that have special purposes:
- intermediate straight supports. They are installed on straight sections of the line and are intended to support wires and cables and are not designed for loads from the tension of wires along the line. On intermediate supports with suspended insulators, the wires are fixed in special supporting garlands, which are located vertically. On supports with pin insulators, the wires are secured by wire knitting. Intermediate straight supports perceive horizontal loads from wind pressure on the wires and on the support, and vertical loads from the weight of the wires and the own weight of the power line support;
- intermediate corner supports. They are installed at the angles of rotation of the line with wires suspended in supporting garlands. In addition to the loads that act on intermediate straight supports, intermediate supports also perceive loads from the transverse components of the tension of wires and cables;
- anchor corner supports. They are installed at power line rotation angles of more than 20˚, have a more rigid structure than intermediate corner supports and are designed for significant loads;
- anchor supports. Special anchor supports are installed on straight sections of the route for crossing engineering structures or natural barriers. Perceive longitudinal load from the tension of wires and cables;
- end supports. They are a type of anchor supports, installed at the end or beginning of power lines and are designed to absorb loads from one-sided tension of wires and cables;
- special supports, which include: transpositional - used to change the order of wires on the supports; branch lines - for installing branches from the main line; cross - used when overhead lines intersect in two directions; anti-wind - to enhance the mechanical strength of overhead lines; transitional - when crossing overhead lines through engineering structures or natural barriers.
According to the method of fixation into the soil, pores are divided:
By design, power line supports are divided into:
- free-standing supports. In turn, they are divided into single-post And multi-post;
- supports with guys;
- emergency reserve cable-stayed supports.
Transmission line supports are divided into supports for lines with voltages of 0.4, 6, 10, 35, 110, 220, 330, 500, 750, 1150 kV. These groups of supports differ in size and weight. The greater the voltage passing through the wires, the higher and heavier the support. The increase in the size of the support is caused by the need to obtain required distances from the wire to the support body and to the ground, corresponding to the PUE (Electrical Installation Rules) for various line voltages.
Based on the material used, power transmission line supports are divided into wooden, metal and reinforced concrete. The choice of the type of power transmission line supports is usually based on the availability of appropriate materials in the area where the power line is constructed, economic feasibility And technical characteristics object under construction. Wooden poles are used for lines with low voltage, up to 220/380 V. However, despite such advantages as low cost and ease of manufacture, wooden poles have significant disadvantages: wooden poles are short-lived (service life is 10 - 25 years) and do not have high strength , the material reacts sharply to changes in climatic conditions.
Metal supports are much stronger than wooden ones, but require constant maintenance - the surface of the structures and connecting elements must be periodically painted or galvanized to prevent oxidation or corrosion.
High strength and resistance of the material to deformation, corrosion and sudden climate changes, long service life of structures (about 50-70 years), fire resistance, high manufacturability and low cost are some of the few reasons that allow us to say: reinforced concrete is the most appropriate solution for production power transmission line supports in Russia. Indeed, in a country with a huge area and varied climate, there is a need not only for large quantities long communication lines, but also in high reliability in conditions of sudden changes weather conditions and humidity levels. The availability of high-quality reinforced concrete supports for power lines is the most important condition for ensuring stability in the operation of the electric power industry. The Blok group of companies produces and supplies construction market only high-quality products from , in strict accordance with GOST and SNiP.
Reinforced concrete pillars of power transmission line supports are divided into two types according to the manufacturing method.
- vibrating support struts. A manufacturing method in which the concrete mixture is subjected to vibration during pouring into a mold, which ensures an increase in the density and uniformity of concrete with less cement consumption. They are made from both prestressed and non-stressed reinforced concrete and are used as racks and struts in power transmission line supports with voltages up to 35 kV, as well as lighting supports;
- centrifuged support struts. Cooking method concrete mixture, which ensures uniform distribution of the mixture, therefore, each section is completely compacted. Centrifuged pole stands are intended for power lines with voltages of 35-750 kV.
Structurally, reinforced concrete power transmission line supports are elongated racks with different sections depending on the expected operating conditions and loads. The design of the support posts also assumes the presence of embedded parts for installing clamps, traverses and fastenings for rigid or hinged fastening of wires, as well as plates to increase the load-bearing function of products.
According to the type of construction, reinforced concrete supports are divided into the main types:
- cylindrical support struts;
- conical support posts.
Reinforced concrete power transmission line supports come in a wide range.
For high-voltage power lines, centrifuged cylindrical and conical supports are manufactured in accordance with GOST 22687.2-85 “Cylindrical reinforced concrete centrifuged racks for supports high voltage lines power transmission" and GOST 22687.1-85 "Conical reinforced concrete centrifuged racks for supports of high-voltage power lines" respectively.
Vibrating racks are manufactured in accordance with GOST 23613-79 “Reinforced concrete vibrating racks for supports of high-voltage power lines. Specifications", GOST 26071-84 "Reinforced concrete vibrating racks for supports of overhead power lines with a voltage of 0.38 kV. Technical specifications" and series 3.407.1-136 "Reinforced concrete supports of 0.38 kV overhead lines" and 3.407.1-143 "Reinforced concrete supports of 10 kV overhead lines".
Special two-post supports are manufactured in accordance with series 3.407.1-152 “Unified designs of intermediate two-post reinforced concrete supports of 35-500 kV overhead lines.”
Series 3.407.1-157 “Unified reinforced concrete products for 35-500 kV substations” includes vibrating conical racks with rectangular cross-section centrifuged cylindrical racks. Series 3.407.1-175 “Unified designs of intermediate single-column reinforced concrete supports of 35-220 kV overhead lines” contains instructions for the manufacture of conical racks of supports.
Reinforced concrete centrifuged supports for overhead contact networks and lighting are manufactured according to series 3.507 KL-10 “Supports for overhead contact networks and lighting.”
The material used for the manufacture of reinforced concrete racks of power transmission line supports is resistant to electrical corrosion and corrosion from impact. environment Portland cement of various classes of compressive strength, from B25. Fine sand and crushed gravel. Selected for each project different option preparation of concrete mixture: vibration is used for poles of power transmission lines with voltages up to 35 kV and lighting poles, centrifugation is used for poles of power lines with voltages of 35-750 kV. Concrete grades for frost resistance and water resistance are assigned depending on operating conditions and climate in the construction area, from F150 and W4, respectively. Additionally, special plasticizing and gas-entraining additives are added to the concrete of the support posts.
The concrete of power transmission line poles is reinforced with prestressed reinforcement to give greater strength to the products. All reinforcement parts and embedded products are necessarily coated with a special substance against internal corrosion.
The following classes of steel are used as working reinforcement:
- rod thermally strengthened periodic profile class At-VI according to GOST 10884-71 when operating racks in the construction area with a design outdoor temperature of not lower than -55°C;
- hot-rolled rod of periodic profile of classes A-IV and A-V. When the design temperature of the outside air is below -55°C, steel of these classes should be used in the form of whole rods of measured length. Reinforcing wire is used as transverse reinforcement class B-I. For the manufacture of clamps, grounding conductors and mounting loops, hot-rolled smooth reinforcing steel of class A-I is used.
Marking of racks according to GOST 23613-79.
In the brand designation of the rack, the letters and numbers mean: SV - vibrating rack; additional letters “a” and “b” - options for racks, where:
- “a” - the presence in the racks of embedded products (pins) and holes for fastening wires;
- “b” - the presence of holes in the racks for fastening anchor plates;
- the number after the letters is the length of the stand in decimeters;
- the number after the first dash is the calculated bending moment in ton-force meters;
- the number after the second dash is the design grade of concrete for frost resistance.
For racks made of sulfate-resistant cement, the letter “c” is placed after the design grade of concrete for frost resistance.
For racks intended for use in areas with a design outdoor temperature below -40°C or in the presence of aggressive soils and groundwater, the third group of brands also includes the corresponding designations of characteristics that ensure the durability of racks under operating conditions: M - for racks used in areas with a design outdoor temperature of -40°C;
For racks used in conditions of exposure to aggressive soils and groundwater - characteristics of the degree of concrete density: P - increased density, O - especially dense.
According to GOST 22687.1-85 and GOST 22687.2-85, the rack brand consists of alphanumeric groups separated by a hyphen.
The first group contains the designation of the standard size of the rack, including:
letter designation type of rack, where:
- SK - conical;
- SC - cylindrical;
- Next, the length of the stand is indicated in meters in whole numbers.
The second group includes designations: the bearing capacity of the rack and the scope of its application in the support and the characteristics of prestressed longitudinal reinforcement:
- 1 - for reinforcing steel class A-V or At-VCK;
- 2 - the same, class A-VI;
- 3 - for reinforcing ropes of class K-7 with mixed reinforcement;
- 4 - the same, class K-19;
- 5 - for reinforcing ropes of class K-7;
- 0 - for reinforcing steel class A-IV or At-IVK.
In the third group, if necessary, additional characteristics are reflected (resistance to aggressive environments, the presence of additional embedded products, etc.).
Marking according to series 3.407.1-136 for the designs of 0.38 kV overhead line support elements consists of an alphanumeric designation.
The first part indicates the designation of the type of power line support:
- P - intermediate;
- K - terminal;
- UA - corner anchor;
- PP - transitional intermediate;
- POA - transitional branch anchor;
- PC - cross.
In the second part - the standard size of the support: odd numbers for single-circuit supports, even numbers for eight- and nine-wire overhead lines.
Marking according to series 3.407.1-143 for 10 kV overhead line supports has in the first part a letter designation of the type of support:
- P - intermediate;
- OA - branch anchor;
- Etc.
In the second part there is a digital index 10, indicating the overhead line voltage.
In the third part, separated by a dash, the number of the standard size of the support is written.
The elements of the supports, which include slabs and anchors, are marked with an alphanumeric designation. P - slab, AC - cylindrical anchor.
The product size number is indicated through a hyphen.
The marking of reinforced concrete intermediate single-post supports according to series 3.407.1-175 and double-post supports according to series 3.407.1-152 consists of an alphanumeric designation.
The first digit indicates the serial number of the region in which the support is used;
The following combination of letters is the type of support:
- PB - intermediate concrete;
- PSB - intermediate special concrete;
- The next group of numbers is the voltage of the overhead line in kV, in the dimensions of which the support is made;
- The number next after the dash is the serial number of the power line support, in the unification, with odd numbers belonging to single-circuit supports, and even numbers to double-circuit ones.
Marking of support products according to series 3.407.1-157:
The first group of alphanumeric designations includes letters of the conventional names of products and the main overall dimensions in decimeters, where:
- BC - vibrating stand.
The second group, separated by a hyphen, indicates the load-bearing capacity in kN.m;
The third group, separated by a hyphen, denotes design features(reinforcement option, presence of additional embedded parts).
The marking of supports of the 3.407-102 series includes the following names:
- SCP - cylindrical hollow stand;
- BC - vibrating stand;
- VSL - vibrating stand for lighting lines and railway networks;
- Next comes a number indicating the standard size of the product.
Marking of overhead contact line and lighting supports according to series 3.507 KL-10 consists of alphanumeric designations.
Centrifuged power line supports (issue 1-1):
- OKTs - outdoor lighting poles with power supply cables;
- OAC - anchor supports for external lighting with air supply;
- OPTs - intermediate supports of external lighting with air supply;
- OSC - combined contact network and outdoor lighting supports with power supply cables.
The first number after the letters, separated by a hyphen, indicates the horizontal standard load on the support in centners, the second - the length of the support in meters.
Vibrating supports (issues 1-2, 1-4, 1-5):
- SV - vibrating outdoor lighting stand with cable or air power supply;
- The number following the letters indicates the standard bending moment in the embedment, in tm;
- The second number, separated by a hyphen, indicates the length of the rack in meters.
Unstressed vibrating struts (issue 1-6):
- The first group contains a letter designation of the type of structure, SV - vibrating stand, and a numerical designation - the length of the stand in decimeters;
- The second group is a symbol for bearing capacity.
Designed to hold wires suspended. These include lattice and multifaceted racks, traverses, and foundations. They may have different sizes and shape. The production of power line supports involves the use various materials. These structures are made of reinforced concrete and metal. The following types of supports are distinguished by purpose:
- Anchor;
- Intermediate;
- End;
- Angular.
Anchor wires are installed to limit anchor spans and in places where the number or type of wires changes. Installation of intermediate supports is carried out on straight sections of the electrical wiring route. Corner designs used where it changes its direction. End - used at the beginning and end of the line. The plant for the production and installation of power transmission poles JSC PK "StalKonstruktsiya" produces intermediate supports of rigid and flexible construction in Moscow.
Antenna supports
They are used to secure antenna equipment at the required height. They are a rod metal structure in the shape of a regular tetrahedral pyramid. Depending on the signal strength, the level of communication lines raised may be different. Therefore, the height of these structures ranges from 30 to 80 m. They include:
- Bracket;
- Service area;
- Staircase with railing;
- Crossing area;
- Lattice support.
The main area of application is radio relay communication lines. The structures are secured using bolted connections. A vertical ladder for the movement of people is fixed in the internal shaft of the structure. The production of power line supports of this type is carried out in six standard sizes. In this case, sections 10 m long are used.
Communication towers
They are special towers that have increased bearing capacity and increased height. Their purpose is to place sets of antenna equipment that provide communications. Production metal structures This type is carried out in 2 varieties - masts and towers.
The most popular of them are masts. They are made from rolled pipe and painted white or red. Among them are supports for cellular and radio communications, street lighting, masts for television and radio broadcasting. The most commonly used are three-section designs. Installation of radio masts is carried out in several stages using special equipment.
Power poles
Their purpose is to maintain electrical wires at the required distance from the surface of roofs, ground and wires of other lines. Such structures have to function in various meteorological conditions, so they require strength. The production of power line supports is carried out on the basis of various materials. In rural areas, softwood is still widely used for 35 kV power lines.
Most modern version are multifaceted steel structures galvanized by hot-dip galvanizing. The design period of their operation is 70 years.
Production and installation
In order for such structures to serve for a long time and reliably, they need to be carefully designed and high quality manufacturing. Our metal structures plant produces and supplies power transmission line supports to many energy and manufacturing companies. Process consists of assembling the frame, conducting incoming inspection of raw materials, warm-wet processing of molded products, and output inspection of finished products.
The production of metal power transmission poles in Moscow uses pipe and sheet metal. It is made from high quality carbon steel. Raw materials entering production must be subjected to laboratory control in the form of chemical and spectral analysis.
After production, the products are transported on platforms in separate sections. Before installation of structures, marking of the route is carried out. Next, wells are drilled for their subsequent installation. The depth and diameter of the pit depend on the type of product and the type of soil. Installation of supports is carried out using cranes or manipulators.
When laying overhead power lines, in addition to selecting the cable, it is also necessary to select the supports on which it will be fixed, as well as insulators. We will devote this article to overhead power line supports.
To install overhead lines, metal, reinforced concrete and wooden, as they are often called in everyday life, electrical supports are used.
Wooden supports
They are usually made from pine logs with the bark removed. For power lines with supply voltages up to 1000 V, it is also possible to use other tree species, for example, fir, oak, cedar, spruce, and larch. Logs that will subsequently become power line supports must comply with certain technical requirements. The natural taper of the trunk, in other words, the change in its diameter from the thick lower end (butt) to the upper cut should not exceed 8 mm per 1 meter of log length. The diameter of the log on the top cut for lines with voltages up to 1000 V is taken to be at least 12 cm, for lines with voltages above 1000 V, but not higher than 35 kV - 16 cm, and for lines with higher voltages at least 18 cm.
Wooden supports can be used for the construction of overhead lines with a voltage not exceeding 110 kV inclusive. Most widespread wooden supports were used in overhead lines with voltages up to 1000 V, as well as in communication lines. The advantage of wooden supports is their relatively low cost and ease of manufacture. However, there is a minus, a significant minus - they are susceptible to rotting and the service life of pine supports is about 4-5 years. To protect wood from rotting, it is impregnated with special antiseptics against rotting, for example anthracene or creosote oil. Those parts that will be dug into the ground, as well as cutting ends, braces and traverses, lend themselves to especially careful processing. Thanks to antiseptics, the service life increases by about 2-3 times. For the same purpose, quite often the legs of a wooden electrical support are made of two parts - the main stand and the chair (stepchild):
Where – 1) the main stand, and 2) a chair (stepson)
If the lower part is severely rotted, it is enough to replace only the stepson.
Metal supports
Plus - durable and reliable in operation. Disadvantage - a large consumption of metal is required, which entails a significant increase in cost (compared to wooden ones). Metal supports of overhead power lines are used, as a rule, at voltages from 110 kV, since the operation of metal supports involves high costs for performing very labor-intensive and expensive work on periodic painting, which protects against corrosion.
Reinforced concrete supports
In the industrial manufacturing process are the most the best option for overhead lines both up to 1000 V and above 1000 V. The use of reinforced concrete supports dramatically reduces operating costs, since they practically do not require repairs. Currently, almost everywhere, reinforced concrete supports are used in the construction of overhead lines of 6-10 kV and up to 110 kV. They are especially widespread in urban networks up to and above 1000 V. Reinforced concrete supports can be made either monolithic (cast) or in the form of assemblies, which are assembled directly at the installation site. Their strength depends on the method of concrete compaction, of which there are two - centrifugation and vibration. When using the centrifugation method, a good density of concrete is obtained, which subsequently has a good effect on the finished product.
On overhead power lines, special anchor, corner, end, and intermediate supports are used.
Their purpose is to rigidly secure wires and lines to them. The location for their installation is determined by the project. By design, the anchor support must be strong, since if a wire breaks on one side, it must withstand the mechanical load of the wires on the other side of the line.
Anchor spans are the distance between anchor supports. On straight sections (depending on the cross-section of the wires), anchor spans are up to 10 km long.
Intermediate supports
Serve only to support wires on straight sections of line between anchor supports. From total number of electrical supports installed on the line, intermediate ones occupy about 80-90%.
Corner supports
Designed for installation in places where power line routes turn. If the angle of rotation of the line is up to 20 0, then the electrical support can be manufactured as an intermediate one, and if the angle is about 20-90 0, then as an anchor type.
They are of an anchor type and are installed at the beginning and end of lines. If in anchor electrical supports the force of one-sided tension of the wires can only arise in emergency situation, if the wire breaks, it always operates in the end electrical supports.
Special supports
They are electrical poles of increased height and are used at the intersection of power lines with highways and highways. railways, rivers, intersections between power lines themselves and in other cases when standard height the electrical support is not enough to provide the required distance to the wires. Intermediate electrical supports for lines with voltages up to 10 kV are made single-post (candle-shaped). In low-voltage networks, single-post supports perform the functions of corner or end supports, and are also equipped additionally with guy wires attached to the side opposite to the tension of the wires, or with struts (supports) that are installed on the side of the tension of the wires:
For lines with a voltage of 6-10 kV, electrical supports are made A-shaped:
Air lines are also characterized by their main dimensions and dimensions.
Overhead line dimension is the vertical distance from the lowest point of the wire to the ground or water.
The sag is the distance between the imaginary straight line between the wire attachment points on the support and the lowest point of the wire in the span:
All dimensions of power lines are strictly regulated by the PUE and directly depend on the value of the supply voltage, as well as the terrain through which the route passes.
The PUE also regulates other dimensions when crossing and approaching power lines, both among themselves and between communication lines, highways and railways, overhead pipelines, and cable cars.
To check the designed power line to the requirements of the PUE, mechanical strength calculations are performed, the methods of which are given in special courses on electrical networks.
Services for the manufacture of metal structures for power transmission line supports, the production of metal products, and custom metalworking services are provided by the company "Skhid-budkonstruktsiya", Ukraine.
What types of power line supports exist?
In the production of metal structures for power lines, blowing types of overhead line supports are distinguished: intermediate power line supports, anchor power line supports, corner power line supports and special metal products for power lines.
The types of overhead power line structures that are the most numerous on all power lines are intermediate supports, which are designed to support wires on straight sections of the route. All high-voltage wires are attached to power line cross-arms through supporting garlands of insulators and other structural elements overhead power lines. In normal mode, overhead line supports of this type take loads from the weight of adjacent half-spans of wires and cables, the weight of insulators, linear fittings and individual support elements, as well as wind loads caused by wind pressure on the wires, cables and the metal structure of the power line itself. In emergency mode, the structures of intermediate power transmission line supports must withstand the stresses that arise when one wire or cable breaks.
The distance between two adjacent intermediate supports of an overhead line is called the intermediate span.
Overhead line corner supports can be intermediate or anchor. Intermediate corner elements of power transmission lines are usually used at small angles of rotation of the route (up to 20°).
Anchor or intermediate corner elements of power transmission lines are installed in sections of the line route where its direction changes.
Intermediate corner supports of overhead lines in normal mode, in addition to the loads acting on the usual intermediate elements of power lines, perceive the total forces from the tension of wires and cables in adjacent spans, applied at the points of their suspension along the bisector of the angle of rotation of the power line.
The number of anchor corner supports of overhead lines is usually a small percentage of the total number on the line (10... 15%). Their use is determined by the installation conditions of the lines, the requirements for intersections of lines with various objects, natural obstacles, i.e. they are used, for example, in mountainous areas, and also when intermediate corner elements do not provide the required reliability. Anchor corner supports are also used as end supports from which the line wires go into switchgear substations or stations. On lines running in populated areas, the number of power line anchor corner elements also increases. The overhead line wires are secured through tension garlands of insulators. In normal mode, these lep supports, in addition to the loads indicated for the intermediate elements of the lep, are subject to the difference in tension along the wires and cables in adjacent spans and the resultant of the tensile forces along the wires and cables. Typically, all anchor-type supports are installed so that the resultant of the gravitational forces is directed along the axis of the support traverse. In emergency mode, power line anchor posts must withstand the break of two wires or cables.
The distance between two adjacent power line anchor supports is called the anchor span.
Branch elements of power transmission lines are designed to make branches from main overhead lines when it is necessary to supply power to consumers located at some distance from the route.
Cross elements are used to cross overhead line wires in two directions.
Overhead line end posts are installed at the beginning and end of the overhead line. They perceive forces directed along the line created by the normal one-way tension of the wires.
For overhead lines, power line anchor supports are also used, which have increased strength compared to the types of stands listed above and more complex design.
For overhead lines with voltage up to 1 kV, reinforced concrete racks are mainly used.
What types of power line supports are there? Classification of varieties
They are classified according to the method of fixation in the ground:
Overhead line supports installed directly into the ground
- Power line supports installed on foundations
Types of power transmission line supports by design:
Free-standing power transmission towers
- Posts with guys
Power line supports are classified according to the number of circuits:
Single-chain
- Double-chain
- Multi-chain
Unified power line supports
Based on many years of practice in the construction, design and operation of overhead lines, the most appropriate and economical types and designs of supports for the corresponding climatic and geographical regions are determined and their unification is carried out.
Designation of power line supports
What types of supports are used for the construction of overhead lines?
For metal and reinforced concrete supports of 10 - 330 kV overhead lines, the following designation system has been adopted.
P, PS - intermediate supports
PVS - intermediate supports with internal connections
PU, PUS - intermediate corner
PP - intermediate transitional
U, US - anchor-angular
K, KS - end
B - reinforced concrete
M - Polyhedral
How are overhead line supports marked?
The numbers after the letters in the marking indicate the voltage class. The presence of the letter “t” indicates a cable stand with two cables. The number separated by a hyphen in the marking of overhead line supports indicates the number of circuits: odd, for example, one in the numbering of a power line support is a single-circuit line, an even number in the numbering is two and multi-circuit. The number separated by “+” in the numbering means the height of the attachment to the base support (applicable to metal ones).
For example, symbols overhead line supports:
U110-2+14 - Metal anchor-corner double-chain support with stand 14 meters
PM220-1 - Intermediate metal multifaceted single-chain support
U220-2t - Metal anchor-corner
PB110-4 - Intermediate reinforced concrete