Sophisticated power lines (LPP), serve to deliver electricity over long distances. On the scale of the state, they are strategically important objects that are designed and erected in accordance with SNiP and Pue.
These linear sections are classified on cable and air power transmission lines, installation and gasket of which require compulsory compliance with the calculated conditions and the installation of special designs.
Air lines power lines
Fig.1 Air high-voltage power lines
The most common is the air lines, the laying of which occurs in the open air using high-voltage pillars, to which the wires are fixed using special fittings (insulators and brackets). Most often is the racks of the SC.
The power of power supply includes:
The minimum wisp should be: 5 ÷ 7 meters in non-heated terrain and 6 ÷ 8 meters in settlements.
As high-voltage columns are used:
The use of one or another design is caused by the voltage of the electrical network. We use the skill to determine the power supply voltage in appearance.
Classified ll:
Fig.2 Cable lines underground type
Unlike air lines, cable are insulated and therefore they are more expensive and reliable. This type of wires are used in places where the installation of air lines is impossible - in cities and settlements with dense development, in the territories of industrial enterprises.
Cable LP Classified:
The distinctive features are the laying method:
Fig.3 Laying underwater power lines
Unlike the first two ways of laying cable power passes, the option "Construction" provides for the creation:
Despite the fact that cable and electric power lines are used everywhere, both options have their own characteristics that must be taken into account in project documentationdefining
Air lines are distinguished by a number of criteria. We give a general classification.
I. By the type of current
Picture. Permanent current voltage 800 kV
Currently, the transmission of electrical energy is carried out mainly on alternating current. This is due to the fact that the overwhelming majority of electrical energy sources produce an alternating voltage (the exceptions are some unconventional sources of electrical energy, for example, solar power plants), and the main consumers are alternating current machines.
In some cases, the transmission of electrical energy on constant current is preferable. Diagram of the transmission on constant current is shown in the figure below. To reduce load lines in the line when transmitting electricity on a constant current, as well as on a variable, with the help of transformers increase the transmission voltage. In addition, when organizing transmission from the source to the consumer on a constant current, it is necessary to convert electrical energy from AC to a permanent (using a rectifier) \u200b\u200band back (using an inverter).
Picture. Schemes for the organization of the transmission of electrical energy in a variable (a) and constant (b) current: G - generator (energy source), T1 - an increase in transformer, T2 is a lower transformer, in - rectifier, and - inverter, H - load (consumer).
The advantages of transmission of electricity on constant current VL are as follows:
The main disadvantage of electricity transmission on constant current is the need to use AC transducers to constant (rectifiers) and back, permanent in variable (inverters), and related additional capital costs and additional losses for electricity transformation.
DC voltage did not receive currently widespreadTherefore, in the future, we will consider the installation and operation of the AC voltage.
II. By destination
III. By tension
Decoding of LAP - Abbreviation from the phrase "power line". The LEP is the most important component of energy systems that serves to transmit electricity from generating devices to distribution, converting and, ultimately, to consumers.
The transmission of electrical energy is carried out in metal wires, where the conductor is copper or aluminum. Located method of laying wires:
Listed Types of LEP are the main. Experiments on wireless transmission of energy are carried out, but at present this method did not find distribution in practice, with the exception of low-power devices.
Air lines of power lines, VLEP are characterized by high complexity. Their design, the order of operation is regulated by special documentation. Wl is characterized by the fact that electricity is transmitted by wires laid outdoors. To ensure safety, reduce losses, the composition of the VL is quite complicated.
What is? This is not a high-voltage line, as sometimes consider. VL is a whole range of designs and equipment. The main elements from which there is any power line:
Other components are also important, but their type, nomenclature and quantity depend on various factors:
The fittings include fasteners for connecting insulators, wires, fastening them to supports.
For your information. Dischargers, grounding and reduction devices are used to ensure safety and improve reliability in the occurrence of voltage jumps, including during a thunderstorm.
Sectioning devices allow you to shut down a part of the lept for the period of regulatory or emergency work.
The high-frequency and fiber optic equipment is designed to implement dispatching remote control and management of the operation of the line, partitioning devices, substation and switchgear.
The main documents that regulate any power lines are Construction norms and the rules (SNiP), as well as the rules of the installation of PUE electrical installations. These documents regulate design, design, construction and operation of air lines.
A wide variety of the designs and types of air lines allows you to allocate groups in them, combined with general features.
Most of the existing LEPs are designed to work with alternating current, which is associated with the simplicity of voltage conversion.
Separate types of lines are working with a constant current. They are intended for some applications (power supply of the contact network, powerful direct current consumers), but the total length is small, despite smaller losses on the capacitive and inductive components.
The main mode of operation Vl is normal when all wires and cables are in good condition. There may be cases when part of the wires are missing, but the LAP is operated:
What is cable power transmission? This type of power lines is different from the fact that the wires of different phases are isolated and combined into a single cable.
Under the conditions of the passage of CL divide on:
In addition to the fact that the cable can be in water or land, part of it necessarily passes through cable structures, which include:
This list is incomplete, the main difference of cable structures from others - they are intended exclusively for mounting the cable along with fastening devices, power couplings and branches.
Solid insulation cable lines obtained the greatest distribution:
Less frequently encounter liquid and gas isolation.
Losses in transmitted lines have different nature and are divided into:
The main element for fastening the wires of the power line - support. LEP supports are divided into two types:
Supports can be installed directly into the ground or foundation. By manufacturing material:
Insulators are designed for fastening and isolating the wires of the LPP. Suspension insulators, which allow from individual elements to make any length, depending on the requirements. As a rule, the higher the voltage in the kV, the greater length is the garland of insulators.
Move from:
Armature is used to connect the chains of insulators, fastening them to supports and wires. Cable lines to fittings also include couplings.
The protection uses lightning guides, arresters and grounding devices. Grounding metal supports is made by mechanical fastening of the carrying structure to a grounding circuit. Especially important grounding iron concrete supportsBecause when current leaks, it begins to flow through concrete reinforcement, having a destroying effect. Harm caused by a support is visually visible.
Important! For the best protection, the security wire is placed above all the others.
The technical characteristics of the LEP depends not only on the transmitted voltage and power. The following factors must be taken into account:
What is LEP? Any power line is a powerful source of electromagnetic field. Located near housing, high-voltage lines adversely affect health. The definition of minimum harm to health and the environment plays an important role in the design of the LPP.
Technical calculations are produced in order to determine which type of line should be used to achieve the greatest efficiency.
In general, it can be assumed that the power line (LEP) is an electric line that goes beyond the power plant or substation and intended for transmitting electrical energy to the distance; It consists of wires and cables, insulating elements and bearing structures.
The modern classification of the LEP for a number of signs is presented in Table. 13.1.
Classification of power lines
Table 13.1.
|
Sign |
Type of line |
Variety |
|
Rod Toka |
Direct current |
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|
Three-phase alternating current |
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|
Multiphase alternating current |
Six-phase |
|
|
Twelve phase |
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|
Nominal voltage |
Low-voltage (up to 1 kV) |
|
|
High voltage (over 1 kV) |
CH (3-35 kV) |
|
|
VN (110-220 kV) |
||
|
SVN (330-750 kV) |
||
|
UVN (over 1000 kV) |
||
|
Constructive performance |
Air |
|
|
Cable |
||
|
Number of chains |
Disposal |
|
|
Two-chart |
||
|
Multilette |
||
|
Topological characteristics |
Radial |
|
|
Magistral |
||
|
Branch |
||
|
Functional purpose |
Distribution |
|
|
Powerful |
||
|
Intersi forces |
In the classification in the first place there is a genus. In accordance with this feature, DC lines are distinguished, as well as three-phase and multiphase alternating current.
Lines direct current Competed with the rest only with a sufficiently large length and transmitted power, since in the total cost of the transmission a significant proportion is the cost of the construction of end conversion substations.
The greatest distribution in the world got lines three-phase alternating currentAnd over a length among them, the air lines lead them. Lines multiphase alternating current (six- and twelve phase) currently refer to the category of non-traditional.
The most important feature that determines the difference in the design and electrical characteristics of the power supply, is the rated voltage. U. . To category low-voltage These are lines with a rated voltage of less than 1 kV. Lines S. U hou\u003e 1 kV belong to the category high-voltage, and among them highlighted lines average voltage (CH) with U iom \u003d 3-35 kV, high voltage (Hl) with U Nou. \u003d 110-220 kV, ultra high voltage (SVN) U h (m \u003d 330-750 kV and ultrawow Voltage (UVN) with U HOU\u003e 1000 sq. M.
By design, air and cable lines are distinguished. A-priory aerial line - This is a power line, the wires of which are maintained above the ground using supports, insulators and fittings. In turn, cable line Determined as a power line made by one or more cables laid directly to the ground or laid in cable structures (collectors, tunnels, channels, blocks, etc.).
By the number of parallel chains (l c), paved on the total highway, distinguish disposal (P. =1), dual-chart (and c \u003d 2) and multilette(and C\u003e 2) lines. According to GOST 24291-9 B The same alternating current line is defined as a line having one set of phase wires, and two-charted VLs are two sets. Accordingly, the multirecasted ll is called a line having more than two sets of phase wires. These kits may have the same or different nominal voltages. In the latter case, the line is called combined.
Disposal air lines are constructed on monotoned supports, while two-charts can be constructed either with a suspension of each chain on individual supports, or with their suspension on a total (two-chart) support.
In the latter case, it is obviously reduced by the strip of the territory of the territory under the line of the line, but the vertical dimensions and the mass of support are increasing. The first circumstance is usually decisive if the line passes in the densely populated areas, where the value of the land is usually high enough. For the same reason, in a number of countries of the world, multi-specific supports with suspension chains of one nominal voltage are used (usually C and C \u003d 4) or different stresses (with I C
According to topological (circuit), the characteristics distinguish radial and main lines. Radial The line is considered to which the power comes only on the one hand, i.e. From a single power source. Magistral The line is determined by GOST as a line from which several branches depart. Under a branched It is understood by the line attached by one end to another LPP at its intermediate point.
Last Sign of Classification - functional purpose.Here are allocated distribution and food Lines, as well as a line of intersystem communications. The division of lines for distribution and supply is quite conditionally, for those and others serve to ensure the electrical energy of consumption points. Typically, the distribution includes lines of local electrical networks, and to the supply - line of networks of district values \u200b\u200bthat carry out the power supply of the power centers of the distribution networks. The line of intersystem communications directly connect different power systems and are intended for mutual exchange of power in both normal modes and accidents.
The process of electrification, the creation and merging of power systems into a single power system was accompanied by a gradual increase in the rated voltage of the LAM in order to increase their bandwidth. In this process, two systems of nominal stresses have historically developed on the territory of the former USSR. The first, most common, includes the following number of values. U HWT:35-110-200-500- 1150 kV, and the second -35-150-330-750 kV. By the time of the collapse of the USSR, there were more than 600 thousand km of 35-1150 square meters in Russia. In the subsequent period, the growth of the length continued, albeit less intensively. The corresponding data is presented in Table. 13.2.
The dynamics of changes in the length of VL for 1990-1999.
Table 13.2.
|
and , sq. |
Length of VL, thousand km |
|||||
|
1990 |
1995 |
1996 |
1997 |
1998 |
1999 |
|
|
Total |
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Electrical networks are designed to transmit and distribute electricity. They consist of a set of substations and lines of various stresses. In power plants, the increases of transformer substations are built and the high-voltage power lines transmit electricity over long distances. In places of consumption, lowering transformer substations are building.
The basis of the electrical network is usually underground or high voltage air lines. The lines coming from the transformer substation to the introductory and distribution devices and from them to the power camshafts and to group panels are called the supply network. The supply network, as a rule, is an underground low voltage cable lines.
On the principle of networking, we are divided into open and closed. The opening network includes lines going to electrical receivers or their groups and receiving power on one side. An open network has some disadvantages in the fact that when an accident, at any point of the network, the food of all consumers ceases to emergency.
The closed network may have one, two or more power sources. Despite a number of advantages, closed networks have not yet been widely distributed. At the place of laying of the network there are external and internal.
Each voltage corresponds to certain electrical wiring methods. This is explained by the fact that the voltage is higher, the more difficult to isolate the wires. For example, in apartments, where the voltage is 220 V, the wiring is performed by wires in rubber or plastic insulation. These wires are simple on the device and cheap.
It is incomparably more difficult to arrange an underground cable, designed for several kilovolts and laid underground between transformers. In addition to enhanced insulation requirements, it should still have increased mechanical strength and corrosion resistance.
For direct power supply of consumers are used:
For the transmission to the voltage distance in tens and hundreds of kilovolt, air lines are created. Wires high rise above the ground, air is used as insulation. The distances between the wires are calculated depending on the voltage, which is planned to be transmitted. Dimensions increase and constructs constructions with an increase in operating voltage.
The electric transmission line is called a device for transmitting or distributing electricity over the wires in the open air and attached to peers (brackets), insulators and fittings to supports or engineering facilities, in accordance with the "rules of electrical installations" on the voltage, airlines are divided into two Groups: voltage up to 1000 V and voltage over 1000 V. For each line of lines are set technical requirements their devices.
Air power transmission lines 10 (6) kV are most widely used in rural areas and in small cities. This is explained by their smaller cost compared to cable lines less building density, etc.
For wiring of air lines and networks, various wires and cables are used. The main requirement for the material of the wires of the power lines of the power lines is small electrical resistance. In addition, the material used for the manufacture of wires must have sufficient mechanical strength, to be resistant to the action of moisture and in the air of chemicals.
Currently, the wires of aluminum and steel are most often used, which allows saving deficient non-ferrous metals (copper) and reduce the cost of wires. Copper wires are used on special lines. Aluminum has low mechanical strength, which leads to an increase in the arrow of the provice and, accordingly, to an increase in the height of the supports or a decrease in the length of the span. When transferring small electricity powers for short distances, the use of steel wires are found.
For the insulation of wires and fastening them to the supports of power lines, linear insulators are served, which, along with the electric, should also have sufficient mechanical strength. Depending on the method of fastening on the support, the insulators are plotted (they are fixed on hooks or pins) and suspended (they are collected in the garland and fasten to the support with special reinforcement).
The pin insulators are used on power lines with voltage up to 35 kV. We label them with letters denoting the design and purpose of the insulator, and numbers indicating the operating voltage. On the air lines of 400 V, the TF, SC, ICF pine insulators are used. The letters in the symbol symbols denote the following:
T - Telegraph;
F - porcelain;
C - glass;
Shs - pine glass;
SHF - pin porcelain.
Pin insulators are used to hang up relatively light wires, and depending on the terms of the tracks are used different types Fastening wires. The wire on intermediate supports is usually strengthened on the head of the pin insulators, and on the angular and anchor supports on the neck of the insulators. On the angular supports, the wire is placed on the outside of the insulator relative to the corner of the line rotation.
Pendant insulators are used on air lines of 35 kV and higher. They consist of a porcelain or glass plate (insulating detail), caps of a forging cast iron and a rod. The design of the socket socket and the rod head provides a spherical hinge connection of insulators when the garlands is completed. Garlands are collected and suspended to supports and thereby provide the necessary insulation of wires. The amount of insulators in the garland depends on the voltage of the line and the type of insulators.
The material for mating aluminum wire to the insulator is an aluminum wire, and for steel wires - soft steel. When viscating wires, single mounting is usually performed, the double mount is used in locality and at elevated loads. Before viscous, the wire is blank (at least 300 mm).
Head mating is performed by two knitted wires of different lengths. These wires are fixed on the neck of the insulator, twisting among themselves. The edges of a shorter wire wrapped the wire and tightly attract four to five times around the wire. The ends of the other wire, longer, are applied to the insulator head through the wire four to five times.
To perform lateral mating, they take one wire, put it on the neck of the insulator and turn around the neck and wires so that one of its end is over the wire and bent from top to bottom, and the second is from the bottom up. Both ends of the wire are removed forward and turn them around them around the neck of the insulator with the wire, changing places relative to the wire.
After that, the wire is tightly attracted to the neck of the insulator and wrap the ends of the knitting wire around the wire from the opposite sides of the insulator six to eight times. In order to avoid damage to the aluminum wires, the place of mating is sometimes wrapped with an aluminum ribbon. Cutting the wire on an insulator with a strong tension of the knitting wire is not allowed.
The knitting of the wires are performed manually using the Monter the Passatages. Special attention is paid to the density of the adjacent knitting wire to the wire and the position of the ends of the knitting wire (they should not strike). Pins insulators are attached to supports on steel hooks or pins. The hooks are written directly into wooden supports, and the pins are installed on metal, reinforced concrete or wooden traverses. For the attachment of insulators on the hooks and pins use transitional polyethylene caps. The preheated cap is tightly overwhelmed to the pin until it stops, then the insulator is screwed onto it.
Wires are suspended on reinforced concrete or wooden supports using suspended or pin insulators.
The smallest permissible height of the lower hook location on the support (from the ground level) is:
The smallest permissible cross sections of the wires of air power transmission lines of more than 1000 V are selected by the conditions of mechanical strength, taking into account the possible thickness of their icing.
For air LAP voltage up to 1000 V, under the conditions of mechanical strength, wires that have sections of at least:
On the air power transmission lines to 1000 V sets grounding devices. The distance between them is determined by the number of thunderstorms of the year:
The resistance of the grounding device should be no more than 30 ohms.
Device of air power transmission.
The power lines of the power lines consist of supporting structures (supports and bases), traverse (or brackets), wires, insulators and reinforcements. In addition, the VL includes the devices necessary to ensure uninterrupted power supply of consumers and normal operation of the line: lightning cables, dischargers, grounding, as well as auxiliary equipment.
Power line supports support wires at a predetermined distance from each other and from the ground surface. And the supports of air lines with voltage up to 1000 V can also be used to hang on them wires of radio networks, local telephone communication, outdoor lighting.
Airlines are characterized by simplicity of operation and repair, lower cost compared to cable lines of the same length.
Depending on the purpose there are intermediate and anchor supports. Intermediate supports are installed on direct plots of the VL route, and they are intended only to maintain wires. Anchor supports are installed for the transition of VL through engineering facilities or natural barriers, at the beginning, at the end and on the turns of the LAP. Anchor supports perceive the longitudinal load from the difference in the removal of wires and cables in adjacent anchor spans. Treatment is called the effort with which the wire or cable is pulled on the supports. Treatment varies depending on the wind strength, ambient temperature, ice thickness on the wires.
Horizontal distances between the centers of two supports, on which the wires are suspended, called the span. The vertical distance between the lower point of the wire in the span to intersectable engineering structures or to the surface of the Earth or water is called the name of the wire.
The wire of the wire is called the vertical distances between the lower point of the wire in the span and the horizontal direct connecting point of the fastening of the wire on the supports.
Power and lighting networks with voltage up to 1000 V, made by insulated wires of all corresponding sections or unsonent cables with rubber or plastic insulation by cross section to 16 mm2, are electrical wiring. The outer is considered the wiring, laid through the outer walls of buildings and structures, between buildings, under sheds, as well as on supports (no more than 4 spans, each length of 25 m) outside the streets and roads.
Put the wires at a height of at least 2.75 m from the surface of the Earth. When crossing pedestrian tracks, this distance makes at least 3.5 m, and when crossing passages and ways to transport goods - at least 6 m.
Power air lines Over 1 kV - a device for transmitting electricity over the wires located outdoors and attached with insulating structures and reinforcements to supports, carrier structures, brackets and racks on engineering facilities (bridges, overpass, etc.).
Wires and protective cables through insulators or garlands of insulators are suspended on supports: intermediate, anchor, angular, end, transposition, reinforced (anti-mantle and large transition supports). They are performed by free-standing or with delay-wooden, reinforced concrete or metal, single-chain, two-charts, etc.
Uninsulated single and multi-voltage wires from one and two metals (combined) are used for mounting.
Recently, the self-supporting insulated wires (SIP) began to use, which reduces the distance between the wires of the VL. For insulation of wires and cables from Earth and fastening them to supports, insulators are made from porcelain and glass.
On VL 110 kV and the suspended insulators should be used, the use of rod and support-rod insulators is allowed.
On VL 35 kV and the suspended or stem insulators are used below. It is allowed to use pin insulators.
HA BL 20 kV and below should be applied:
The choice of type and material (glass, porcelain, polymeric materials) of insulators is carried out taking into account climatic conditions (temperature and humidification) and pollution conditions.
On VL, passing into particularly difficult conditions (mountains, swamps, regions of the Far North, etc.), on VL, built on two-charted and multi supports, on VL, feeding traction substations of electrified railways, and in large transitions, independently From the voltage, glass insulators should be used or (if there is an appropriate rationale) polymer.
Route VL, i.e. The terrain strip where it passes, after surveys and coordination with organizations, the interests of which are affected by the construction of the WL, is finalized by the project.
Before installation, documents are drawn up for the alienation and removal of land plots, demolition of structures, as well as the right to flood crops and rod of forest. Production package is performed, i.e. Wake up of the installation centers on the installation site Vl.
The complex of works on the construction of WL includes the preparatory, construction, installation and starting work, as well as the delivery of the line into operation.
Works directly on the track start from acceptance from the design organization and customer of the production pickets of the VL. Then they cut the bottom (if VL or individual sections pass through forest areas). The widths between the crowns of trees in forests and green plantings are taken depending on the height of trees, voltage VL, terrain. The minimum width of the appearances is determined by the distance from the wires with their greatest deviation to the crown of trees. This distance should be at least 2 m for a voltage of up to 20 kV and 3 m - for a voltage voltage of 35-110 kV.
All trees inside the seekers are cut down so that the height of the stump is not more than 1/3 of its diameter. For the passage of transport and mechanisms in the middle of the widths on a width of at least 2.5 m trees cut down to the ground. In winter, when cutting the forest, the snow around each tree is cleared to the ground level. The wood, obtained while cutting the trees, is sorted, separated and placed in the stacks along the request; The bunches are folded into the heaps for the export.
The main SMR includes the manufacture of wooden supports, delivering supports or their parts on the highway, breakdowns of rocks of cutlets under support, digging, assembling and installing supports, circle of wires and other materials on the highway, installation of wiring and protective grounding, phasing and numeration of supports .
For anchor a-shaped support, there are two pitchers, the axes of which are located from the center of the picketing column of support in both directions along the axis of the track. Pulling under the angular A-shaped support is placed on the bisector of the angle of rotation of the line and perpendicular to it (Fig. 4, b). Marking under support with sinks and pins, as well as under narrow beads and wide-visual metal supports are made similarly. If the digging of the kittlers is carried out with drill machines, they only produce a breakdown of calellov centers.
Drain of catlers manually is performed in exceptional cases, if the earthmoving machines can not approach the picket under the conditions of the terrain. Drain of kitty should be the most mechanized. For this purpose, drilling vehicles (yamobura), excavators, bulldozers are used. Land work should be carried out with the maximum seal of the walls of the pit, which provides a reliable fastening of supports. The depth of the kittlers to install the supports depending on the soil and mechanical loads on the support is determined by the project.
The elements of the supports are manufactured, as a rule, at special plants and transport partly assembled.
The last assembly of elements in supports is made on specialized areas (polygons) or directly on the pickets of the ll. The place of assembly of the supports is chosen depending on their type, transport capabilities, characteristics of the track, etc., it is determined in the PPR. The final (complete) assembly of complex supports, as a rule, is performed on the pickets of the ll. The assembly is made on special sites cleaned from interfering items. This ensures the convenience of laying out the details of the support. In addition, for the subsequent lift of the supports, the path is cleared for the free passage of cranes and tracting transport, the anchors are securely fastened, the rigging cables are removed on the required distance from the valid voltage lines or communication lines.
As a rule, the supports are laid out and assemble in the direction of the axis of the line, near the foundations or pitchers with such a calculation so that the collected supports do not need to be pulled out when lifting. The composition of the assembly of supports, the installation of pin insulators mounted on hooks and pins with polyethylene caps is included.
The quality and serviceability of the details of the supports are checked twice: first before assembly, then on the picet of the track, since it is possible to damage the supports during transportation.
For each team of support for 35 kV 35 kV and higher, the passport is filled or recorded in the support magazine.
For lifting and installing supports best tool It is a caterpillar crane that requires a minimum of rigging funds. The crane hook should capture the support slightly above its center of gravity, otherwise she can turn over.
In the absence of a caterpillar crane, the required carrying capacity or with insufficient removal of the crane boom can be applied by a truck crane with a carrying capacity of 5-7 T in conjunction with the tractor. The support is raised at the beginning of the truck before reaching it an angle of 35-40 ° in relation to the horizontal surface of the Earth. Further rise of the support is performed by a tractor pulling the cable, fixed behind the support. To prevent overturning of the support toward the tractor to the top of the support, the brake cable is attached to the start of the lift.
In the absence of cranes, the supports are installed by the drop-down arrow using the tractor. The falling boom is pre-raised manually or with a small crane. To prevent the transition of support through the vertical position, the brake cable is provided. There is also a method for installing supports by building: support is raised by individual sections, connecting them in a vertical position. This method is used when transporting high supports across the river or when installing heavy supports.
After installing the supports in the pit or the foundations, their position is selected in accordance with regulatory instructions. For example, the deviation of reinforced concrete supports from the vertical axis along and across the line (the ratio of the deviation of the upper end of the support rack to its height) must be 1: 150. The vertical position of the supports of 35-110 sq. 35-110 kV is checked by theodolite.
Recruited supports are firmly fixed: in the ground-thorough layer-by-layer traam; On foundations and reinforced concrete piles-screwing nuts on anchor bolts.
After reconciliation and fixing the supports, constant signs are applied on them, the year of installation, the conditional designation of the name VL, etc. The correctness of the installation of the support is confirmed by the passport, in which permission is made on the production of work on the installation of wires and cables.
Under installation work on VL, the following basic operations are performed:
The long-term practice of construction of the WL revealed the most appropriate organization of work, the name of the flow method. Each type of work is entrusted by a specialized brigade. So, if in the first anchor span, where the installation begins, fastening the wires on the intermediate supports, then the second is carried out the tension of wires and cables, in the third rolling, etc.
After completing all the preparatory work and inspection, the tracks prepared for the installation proceed directly to the splitting of the wires. As a rule, the splitter is performed in two ways: with fixed roster devices installed at the beginning of the mounted section, or using mobile fooling devices (carts, sleds, cable conveyors, etc.), moving along the track by traction mechanism.
The first method does not require the manufacture of special mobile fools (carts), but during the movement on Earth, damage to the cable and the upper observables of aluminum wires is possible. The drums with the wire are set at 15-20 m from the first anchor support in the direction of rolling. Moved from each drum for a length of 15-20 m wire or cable with the mounting clamp installed at the end are fixed to the traction mechanism. It moves along the route and after entering the first intermediate support, 30-40 m stops. Wires unfold and folded in the position, initial for lifting on the support.
After making sure the assembly of the garlands of insulators, they are raised to support.
This method is used when installing short lines, as well as on sites, where the possibility of their damage to the wires is unlikely (with a good snow or herbal cover).
In the second method, the rushing is first performed by an anchoring of wires and cables on the first anchor support. Then the traction mechanism along with a rolling trolley moves to the first intermediate support. Prior to moving to the second intermediate support from the drum, 5-10 turns of the wire or cable are wounded and unfold it into its original position. Subsequent operations are carried out in the same way as at the first method. Rolling of wires and cables is carried out only by rollers suspended on supports. When rolling, measures are taken to protect wires from damage when ground friction, especially solid soils.
The connection of steel aluminum wires with a cross section of up to 185 mm2 in the spans of the VL above 1000 V is carried out by oval connections, mounted twisting, and by cross section of up to 240 mm2 - connecting clamps mounted with a solid crimping. In the hinges of the anchor and nodal supports, the compound is performed by thermal welding for steel aluminum wires with a cross section of up to 240 mm2. The wires with a cross section of 300 mm2 are connected by the pressed connectors, and when connecting wires of different stamps, bolted clamps are used.
When mounting the tensioning clamp, mounted with the cutting of the wire, to the end of the wire forming the loop (cable), and the wires leaving the span, impose wire bandages. The ends of the wires are cut and cleaned from the dirt with a napkin moistened in gasoline. The inner surface of the aluminum housing 1 is purified by steel hero, they feed the aluminum wire wire and release the steel core wire. Protheses with gasoline core and smearing the thin layer of technical vaseline, turn it into an anchor hole 2 until it stops. Pressing the tension clamp leads in a direction from the eye to the wire, and the pressing of the aluminum body is the middle of the clamping to its end.
If the plumes requires a detachable compound, bolted and dyeing clamps are used, but such a connection does not fully give a completely stable and reliable electrical contact.
The standards establishes the requirements for the mechanical strength of the compound in flights, which should be at least 90% of the strength of the whole wire. In the loops (loops), a smaller margin of safety is allowed (30-50% of the strength of the whole wire). The instructions for installing air lines of power lines provide data on loads that must withstand welded connections for each brand of wire.
For welding wires, the propano-oxygen flame requires oxygen, propane and special burner, this welding gives good dual quality.
The reliability of the electrical contact of the welded compound is determined by the coefficient expressing the ratio of ohmic resistance of the wires of the wires with a welded connection to the resistance of the same segment of the whole wire. This coefficient should not exceed 1.2. The ohmic resistance of short sections of the wire is measured by a micromimet.
The need to connect wires from inhomogeneous materials or wires of different sections occurs during responsible transitions through rivers, lakes and railway highways. Such compounds are performed by special transitional looped clamps of PP, representing two sleeves with legs connected on bolts.
The tension of the wires lead, as a rule, in flights between the anchor or anchor-angular supports, to which the rolled and connected wires are attached using tension clamps and tensioning insulant garlands. The tensioning garlands and the tension clip are raised to the support by a block having a cable and a mounting clamp. For lifting garlands, a car, tractor or winch are used.
When lifting the weight of the garlands with a wire on the first in the course of the installation anchor support, this support does not experience the efforts of these tension. But when tightening and fixing the garland on the second anchor support, the efforts of the efforts are experiencing both anchor supports, and in connection with which during this period they are strengthened with stretch marks.
Prior to the beginning of the severity of the wires, all works on the rolling and connecting of wires and cables should be completed.
As a traction mechanism, tractors, cars, winches are used. The choice of mechanism depends on the actual conditions of installation (traction effort, routes, etc.). When the tension is observed the lifting of wires and cables in flights and the removal of items and dirt from them; behind the passage of repair couplings and connecting clamps through rollers; For passage roads and other obstacles in the work area.
The tension of the wires on metal supports are performed similarly.
When tightening the wires and cable, use data of the VL project, in the tables of which the values \u200b\u200bof the prior arrows are indicated depending on the distance between the supports and air temperature during the installation. It should be borne in mind that in the spring and autumn temperature of the air in the morning can significantly exceed the temperature of the wire lying on the ground. In this case, the wire is lifted from the ground with a car or tractor and kept in such a position until it takes the ambient temperature.
Typically, the magnitudes of arrows are given in the installation tables of the project or in curves for the intermediate span of the anchor. When an anchor plot has uneven spans, the progress boom is given for the so-called switter, the length of which is indicated in the tables or curves of the VL project.
Before tightening the wires, a reliable connection should be prepared (alarm) between all people participating in this work: a monter that produces the arrow of the Provision, observing in the intermediate span and the driver of a car or tractor, with which the wires are tightened.
The reception of the arrows of the wire with direct sight is starting from the middle wire with the horizontal location of the wires and from the top - with the vertical.
When visiting the wire (or cable), lead to the line of sight from above, for which the wire is first plugged (by 0.3-0.5 m), and then release to the specified proc. With long anchor spans (more than 3 km), sights are produced in two spans located in each third of the anchor site. With the length of the anchor span less than 3 km, the sights are produced in two spans: the most remote from the traction mechanism (first of all) and more close (in the second place) to it.
When tensioning and visiting wiring and cables, it is strictly withstanding the specified ventilation force value at the corresponding air temperature. The actual prior arrow should not differ from the project by more than ± 5% with the mandatory observance of the normalized distances to the Earth and the engineering structures. The magnitude of the wire or cable relative to the other should not be more than 10% of the Provision project boom.
At the end of sighting on a wire with anchor support, located from the side opposite to the traction mechanism, a label is applied (bandage or indelible paint). Then, if the tension clip is mounted on the ground, the wire is lowered to the ground.
Fastening of wires and cables to anchor-type supports on Vl35-100 kV with suspended insulators is carried out using tension clamps: Wedge-Coush wedges, bolted and pressed.
Up to 10 kV, where pin insulators are mainly used, the anchor mount is carried out using bias clamps. The type of wire fastening on the pin insulators (single or double) depends on the characteristics of the WL (the conditions of the track, the brand of wires, etc.) and is determined by the project.
Before mounting the ends of the wires and the contact surfaces of the tension clamps are thoroughly wiped with a cloth moistened in a solvent (gasoline, acetone, etc.), and then cleaned with a carposecility or steel hero under the layer of neutral technical vaseline.
To expose the steel core of the steel aluminum wire, aluminum cores of the lower oops are written only to half of their diameter in order to avoid damage to the core. The naked ends of the core are washed in a solvent, dryly wipe on a rag and lubricated with a vaseline. The process of pressing tension and connecting clamps is similar.
Installation of wires and cables should be carried out, as a rule, without breaking them in loops (loops). Cutting loops (loops) is allowed only in exceptional cases, for example, in order to avoid the installation of the connecting clamp in the span or on supports that limit the span intersection with engineering structures. Installation of wedge and bolted clamps with undiscable loops are produced simultaneously on the side of the mounted anchor span and towards the span along the rolling of wires.
The fastening of wires and cables on intermediate supports on an AD to 35 kV on the pin insulators and in the supporting clamps of the insulators of 35-110 kV insulators produce only after finalizing the wires on the anchor supports that limit the mounted section of the VL.
The wiring of the wires of the rollers and their fastening is made without lowering them to the ground. On VL 35-110 kV, the transition of the wires is made from telescopic steps, and in the absence of mechanisms, suspended staircases (cradles) are used.
Up to 35 kV, with the use of pin insulators, the shifting and fastening of the wires are carried out directly from the support.
At 6-35 kV, aluminum and steel aluminum wires are fixed with a side viscous with a dense shell of the wire aluminum wire in the zone of its contact with a cervical of the insulator. The knitting of the wires start from point 0, where they are applied the middle of the knitting wire. The right end of the wire should be on the line, it is fixed with three turns on the wire, then directed along line a. The left end of the wire follows the line b, it is also fixed with three twisters on the wire and direct along the line B, after which both the wires are secured on the wire. Aluminum wire for winding and mating take the same diameter as wire mounted wire, but not less than 2.5 and no more than 4 mm. The length of the knitting wire per mount is 1.4 m, the length of the winding wire is about 0.8m.
Installation of wires and cables on transitions is performed in the same sequence and order as when mounting them between the anchor supports. At the end of the installation of wires and cables, the transition is handed over to the owner's organization on the act. If the installation is made with retreats from the project, the act leads the list of these deviations and indicate who they are allowed.
Insulation of air electrical networks is exposed to various kinds of overvoltages. These overvoltages (especially atmospheric) can cause overlappings of outer insulation, interruption of internal insulation, a short circuit arc, emergency shutdown and disrupt the uninterrupted power supply.
Air lines with a voltage of 110 kV on metal reinforced concrete supports, as a rule, protect against direct hits of lightning cuts along the entire length. 120 kV voltage on wooden supports and voltage to 35 kV such protection do not require. Single metal and reinforced concrete supports and other places with weakened insulation on a voltage of 35 kV with wooden supports are protected by tubular dischargers or in the presence of APV protective gaps, and on a voltage of 110-220 kV-tubular arresters.
The experience of operating tubular arresters showed that the use of them in order to increase the inexpoxicity of air lines does not give proper effect. The fact is that the likelihood of damage to tubular arresters during the thunderstorm season has an order of 0.001, which, with their large number, reduces the inconvenience rate. In addition, the tubular arresters have the upper and lower limits for the current short circuit, and this requires systematic audits and delays the electrical arc harvesting at a repeated discharge of lightning and parallel triggered multiple tubular arresters. Therefore, currently tubular arresters are installed only to protect outlets with weak insulation. These include: the places of crossing the LPP, as well as the intersection of the airline with the line of communication. On lines with wooden supports, tubular arresters are installed on the first cable support approach to the substation and on separate angular metal supports. In high transitional supports, due to the increased induced components of overvoltages, at direct lightning strike in the support, it is recommended to install tubular or valve arresters or a lightning cable.
Before installing on the support, the tubular arresters inspect without removing the paper wrap to the end of the installation.
The arresters are installed on transitions with such a calculation so that the latter does not fall in transition during damage to the arrester and burnout, but in the adjacent span. The setting of the arrester should ensure the stability of the external spark gap and eliminate the possibility of overlapping it with a jet of water, which can flush from the upper electrode. The arrester is securely fixed on the support and ground. The sizes of the external spark gap should not differ from the project more than ± 10%.
The installation of arresters on the supports of 35-110 kV VL 35-110 is made to ensure the possibility of mounting and disassembling the arresters without disconnecting the line. The gases exhaust zones of adjacent phases do not have to intersect, and they should not be elements of structures of supports, wires, etc.
Supports having a grond-protective cable or other devices, incremental, reinforced concrete and metal supports with a voltage of 3-35 kV, supports on which power or measuring transformers are installed, disconnectors, fuses or other devices, as well as metal and reinforced concrete supports voltage 110-500 kV Without cables and other lightning devices, if necessary, according to the conditions for ensuring reliable operation of relay protection and automation, must be grounded. In this case, the amount of resistance of grounding devices is taken in accordance with PUE.
Installation of tubular arresters on the BL35 kV
For grounding reinforced concrete supports, elements of the longitudinal rebar fittings are used as grounding conductors, which are metallically interconnected and can be attached to grounding.
Artificial earthingers in lightning protection devices are used in cases where the resistance of natural earthing exceeds the normalized value. They are placed in the ground in the process of the CMR.
The cables and parts of the fastening of insulators to the traverse of reinforced concrete supports are metallically connected with grounding laundering or grounded equipment. The cross section of each of the grounding descents on the BL support is taken at least 35 mm2, and for one-run-level-diameter of at least 10 mm. It is allowed to use steel galvanized single-wire descents with a diameter of at least 6 mm.
On Wood with wooden supports, the bolted compound of grounding descents is recommended; On metal and reinforced concrete supports, the connection of grounding descents can be both welded and bolted.
Grounders VL, as a rule, are plugged into the depth specified in the project.
For mounting, a voltage of up to 1000 V is used wooden, mainly with reinforced concrete consoles (steps) and reinforced concrete supports. For the manufacture of wooden supports uses impregnated with an antiseptic logs of a grade III forest (pine, spruce, fir), and for traverse - only pine or larch. The impregnation of wood by antiseptic significantly lengthens the life of wooden supports.
Vertical and horizontal distances from wires VL to trees and bushes should be at least 1 m. Conditions for forest arrays and green plantings, where the RL route passes, is not mandatory.
In the populated area with single and two-storey buildings, the WL must have grounding devices intended for protection against atmospheric overvoltages. The resistance of these grounding devices should be at least 30 ohms, and the distance between them is at least 200 m for areas with the number of thunderstorm clocks in a year to 40,100 m - for areas with the number of thunder hours in a year more than 40.
In addition, grounding devices must be completed:
Drinking for one-room intermediate supports, as a rule,
We are developing with the help of jambulus with markup exactly along the track axis in order to avoid the output of the support of the line. In places of passage of underground communications (for example, cables), the recess of the soil is made manually.
The connection of wires in the flight spans should be performed using connecting clamps that provide mechanical strength of at least 90% of the discontinuous effort of the occasion.
In one span, no more than one connection on each wire is allowed.
In flights, the intersection of WL with engineering structures, the connection of wires of WL is not allowed.
The connection of wires in the hinges of the anchor supports must be made using clips or welding.
Wires of different marks or sections must be connected only in the hinges of the anchor supports.
Fastening of uninsulated wires to insulators and insulating traverses on the supports of the WL, with the exception of supports for intersections, it is recommended to perform single one.
On VL above 1,000 per double fastening of the wires are performed on anchor supports, intersection supports and in locality.
The location of the phase wires on the support can be any, and the zero wire, as a rule, is located below phase wires.
Safety during CMR and electrical work works is ensured by a continuous supervision of the work of the brigade, which is conducted by a brigadier, must monitor compliance with the safety rules for the work of work, the health of the tool and protective devices, the correct placement of people.
In addition to the general safety regulations, the following rules must be followed by installing:
Power lines - central element of the EE transmission and distribution system. Lines are performed mainly by air and cable. At energy-intensive enterprises also apply conductor. Pa by generator voltage of power plants - busbars; In industrial and residential buildings - internal wiring.
The choice of the type of power transmission, its design is determined by the purpose of the line, the location (gasket) and, accordingly, its rated voltage transmitted by the power, the transmission range, the area and the cost of occupied (alienated) territory, the climatic conditions, the requirements of electrical safety and technical aesthetics and a number of others Factors and, ultimately, the economic feasibility of transmitting electrical energy. The specified choice is made at the stages of the design decision.
This section formulates the requirements that the LEP should meet, the conditions for their implementation and on their basis are some principles and options for the design of the power lines.
The most common at all levels of the power supply system of air lines due to their relatively low cost. For this reason, the use of WL should be considered in the first place.
Air lines power lines
Air is called lines intended for transmission and distribution of EE on wires located outdoors and supported by support and insulators. Air LPPs are constructed and operated in a wide variety of climatic conditions and geographic areas are susceptible to atmospheric influences (wind, ice, rain, temperature change). In this regard, the WL should be constructed taking into account atmospheric phenomena, air pollution, laying conditions (weakly-sealed terrain, territory of the city, enterprise), etc. From the analysis of the conditions of WL, it follows that materials and designs of lines must satisfy a number of requirements: economically acceptable cost, good electrical conductivity and sufficient mechanical strength of wires and cables, resistance to corrosion, chemical impacts; The lines should be electrically and environmentally friendly, to occupy the minimum territory.
Constructive execution of air lines. The main structural elements of the WL are supports, wires, lightning cables, insulators and linear fittings.
According to the constructive execution of supports, single and two-chained VLs are most common. On the track lines can be constructed up to four chains. The lines of the line - the lane of the Earth on which the line is constructed. One chain of high-voltage VL combines three wires (wiring set) of a three-phase line, low-voltage - from three to five wires. In general, the structural part of the VL (Fig. 1) is characterized by the type of support, the lengths of the spans, overall dimensions, phase design, the number of insulators.
The lengths of the spans are chosen on economic considerations, since the provisis of wires increases with increasing length of the spans, it is necessary to increase the height of the supports
N, not to disturb the permissible dimensions of the H line (Fig. 1. b)this will reduce the number of supports and insulators on the line. The lines of the lines are the lowest distance from the lower point of the wire to the Earth (water, the canvas) - was supposed. So to ensure the safety of people and transportation under the line. it the distance depends on the nominee voltage of the line and the conditions of the area (inhabited, unprofitable). The distance between the adjacent phases of the line depends mainly on the nominal voltage. The main structural sizes of the ll are given in Table. 1. The design of the VL phase is mainly determined by the number of wires in the phase. If the phase is made in several wires, it is called split. Splitters are performed by phases of high and ultra-high voltage. At the same time, two wires are used in the same phase at 330 (220) kV, three-tries of 500 kV, four to five at 750 kV, eight or twelve - at 1150 square meters.
Supports of air lines.Opports are structures designed to maintain wires at the necessary height over, land, water and any engineering structure. In addition, on the supports in the necessary cases, the necessary steel grounded cables are suspended to protect wires from direct lightning strikes and associated overvoltage.
Table №1
Design sizes VL
| Rated voltage, kV | Distance between phases D., M. | Long span l, M. | Height of support N., M. | Gaspel lines h,m. |
| 0,5 | 40-50 | 8-9 | 6-7 | |
| 6-10 | 1 | 50-80 | 10 | 6-7 |
| 35 | 3 | 150-200 | 12 | 6-7 |
| 110 | 4-5 | 170-250 | 13-14 | 6-7 |
| 150 | 5,5 | 200-280 | 15-16 | 7-8 |
| 220 | 7 | 250-350 | 25-30 | 7-8 |
| 330 | 9 | 300-400 | 25-30 | 7,5-8 |
| 500 | 10-12 | 350-450 | 25-30 | 8 |
| 750 | 14-16 | 450-750 | 30-41 | 10-12 |
| 1150 | 12-19 | - | 33-54 | 14,5-17,5 |
Types and designs of supports are diverse. Depending on the appointment and placement on the route, they are divided into intermediate and anchor. The supports of the material, execution, and the fastening method, the wiring garters are distinguished. Depending on the material, they are wooden, reinforced concrete and metal.
Intermediate supports The simplest, serve to maintain wires on direct areas of the line. They are most common; Their share on average is 80-90% of the total number of supports VL. The wires are attached to them with the help of supporting (suspended) isolant garlands or pin insulators. Intermediate supports in normal mode are experiencing a load mainly from their own weight of wires, cables and insulators, suspended garlands of insulators hang vertically.
Anchor supports installed in places of rigid fastening of wires; They are divided into terminal, angular, intermediate and special. Anchor supports, designed for longitudinal and transverse components of the tension of the wires (the tension garlands of insulators are located horizontally), the greatest loads are therefore much more expensive and more difficult to intermediate; Their number on each line should be minimal. In particular, end and corner supports, installed at the end or on the rotation of the line, are experiencing a constant tension, wires and cables: unilateral or by an equally rotating angle; Intermediate anchor, installed on extended direct sites, are also calculated on one-sided tension, which may occur when the parts of the wires can be broken in the span adjacent to the support.
Special supports are the following types: Transitional - for large spans crossing rivers, gorges; branch - to perform branches from the main line; Transposition - to change the order of the location of the wires on the support.
Along with the assignment (type), the design of the support is determined by the number of chains of the VL and the mutual location of the wires (phases). Supports (and lines) are performed in a single or two-chart version, while the wires on the supports can be placed with a triangle, horizontally, inverse "christmas tree" and hexagon, or "barrel" (Fig. 2).
The asymmetrical location of the phase wires relative to each other (Fig. 2) causes the detail of inductors and containers of different phases. To ensure the symmetry of the three-phase system and aligning the phases of reactive parameters on long lines (more than 100 km), a voltage of 110 kV and above is carried out permutation (transposition) of wires in the chain using the appropriate supports. With a full transposition cycle, each wire (phase) is evenly over the length of the line occupies consistently all three phases on the support (Fig. 3).
Wooden supports(Fig. 4) is made of pine or larch and apply on lines with voltage up to 110 kV in forest areas, but more and less. The main elements of the supports are steppes (consoles) 1, racks 2, traverse 3, disclosures 4, subsequent bars 6 and riglels 5. Supports are easy to manufacture, cheap, convenient to transport. Their main drawback is a short time due to wheels rotting, despite its antiseptic processing. Application of reinforced concrete steats (consoles) increases the service life of the supports up to 20-25 years.
Reinforced concrete supports (Fig. No. 5) are most widely used on lines voltage up to 750 kV. They may be freestandy (intermediate) and with deficule (anchor). Reinforced concrete supports are more durable wooden, easy to operate, cheaper than metal.
Metal (Steel) Support(Fig. 6) is used on lines with a voltage of 35 kV and higher. The main elements include racks 1, traverse 2, cable-bearing 3, outflow 4 and foundation 5. They are durable and reliable, but quite metallotable, occupy a large area, require to install special reinforced concrete foundations and during operation should be painted for corrosion protection.
Metal supports are used in cases where it is technically difficult and not economically constructed on wooden and reinforced concrete supports (transitions through rivers, gorges, accomplishment of samples from VL, etc.)
Air lines. Wires are designed to transmit electricity. Along with good electrical conductivity (possibly less electrical resistance), sufficient mechanical strength and resistance to corrosion, they must satisfy the conditions of efficiency. For this purpose, wires are used from the cheapest aluminum metals, steel, special alloys of aluminum. Although copper has the highest copper wires due to the high cost and necessity for other purposes in new lines is not used. Their use is allowed in contact networks, in networks of mining enterprises.
Additionally uninsulated (naked) wires are used for VL. According to the design of the wires, there may be single and multi-wiring, hollows (Fig. 7). Single-wire, mainly steel wires are limited in low-voltage networks. To give them flexibility and greater mechanical strength, the wires are made by multi-voltage from one metal (aluminum or steel) and of two metals (combined) - aluminum and steel. Steel in the wire increases mechanical strength.
Based on the conditions of mechanical strength, aluminum wires of stamps A and ACP (Fig. 7) are used on a voltage of up to 35 kV. Air lines of 6-35 kV can also be performed by steel aluminum wires, and above 35 kV lines are mounted exclusively by steel aluminum wires. Style aluminum wires have around the steel core of oops from aluminum wire. The cross-sectional area of \u200b\u200bthe steel part is usually 4-8 times less aluminum, but the steel perceives about 30-40% of the entire mechanical load; Such wires are used on lines with long spans and in areas with heavier climatic conditions (with a greater heated wall thickness). In the steel aluminum wires, the cross section of the aluminum and steel part is indicated, for example, AC 70/11, as well as data on anti-corrosion protection, for example, ACS, ASKP - the same wires, as well as the AC, but with the core filler (C) or the entire wire ( N) anti-corrosion lubrication; ASK is the same wire as the speakers, but with a core coated with a polyethylene film. The wires with anti-corrosion sewn are used in areas where air is contaminated with impurities acting destroyably on aluminum and steel.
Increased wire diameters when the conduction material is unchanged can be used by the use of wires with filler from dielectric and hollow wires (Fig. 7, g, e).Such use reduces the loss of coronation. Hollow wires are used mainly for the axilization of 220 kV camshafts and higher.
The wires from aluminum alloys (AN - Necurity-processed, already heat-treated) have a greater but compared to aluminum mechanical strength and practically the same electrical conductivity. They are used on a voltage voltage above 1 kV in areas from a pushing wall hunger 20 mm.
More and more applications are found with self-supporting insulated wires of 0.38-10 sq. In the lines of 380/220, the wires consist of a carrier, isolated or uninsulated wire, which is zero, three isolated phase wires, one insulated wire (any phase) of external lighting. Phase insulated wires are wedged around the carrier zero wire (Fig. 8). The carrier wire is steel aluminum, and phase-aluminum. The latter are covered with light-resistant thermal stabilized (sewn) polyethylene (APB type wire). The advantages of BL with insulated wires in front of the lines with bare wires can be attributed to the absence of insulators on the supports, the maximum use of the height of support for the suspension of wires; There is no need to trim the trees in the line pass area.
Ground-proof cables Along with spark gaps, arresters, stress limiters and grounding devices, serve to protect the line from atmospheric overvoltages (thunderstorm discharges). The cables are suspended above phase wires (Fig. 2) on a voltage voltage of 35 kV and above depending on the area of \u200b\u200bthunderstorm activity and the support material, which is governed by the rules of electrical installation devices (PUE). As lightning wires, steel galvanized steel ropes are usually used with 35, C 50 and C 70, and when using cables for high-frequency communication - Standard-aluminum wires. The fastening of cables on all supports of the voltage of 220-750 kV should be performed using an insulator, the spark interval bypass. On the lines of 35-110 kV, the attachment of cables to metallic and reinforced concrete intermediate supports is carried out without the insulation of the cable.
Insulators of air lines. Insulators are designed for insulation and fixing wires. They are made from porcelain and tempered glass - materials with high mechanical and electrical strength and resistance to weathering. The significant advantage of glass insulators is that when damaged, tempered glass is crumbling. This makes it easier to find damaged insulators on the line.
By design, the method of fixing on the support isolators are separated into pin and suspended. Pins insulators (Fig. 9, a, b)used for lines with voltage up to 10 kV and rarely (for small sections) - 35 square meters. They are attached to supports with hooks or pins. Pendant insulators (Fig. 9, c) are used on a voltage voltage of 35 kV and higher. They consist of a porcelain or glass insulating part 1, caps of ductile cast iron 2, metal rod 3 and cement ligament 4. Insulators are assembled in garlands (Fig. 10, d):supports on intermediate supports and stretching on anchor. The number of insulators in the garland depends on the voltage, type and material of the supports, the contamination of the atmosphere. For example, in line 35 kV - 3-4 insulator, 220 kV - 12-14; on lines with wooden supports with high load capacity, the number of insulators in the garland one is smaller than on lines with metal supports; In the tensioning garlands operating in the most difficult conditions, set 1-2 isolator more than those in support.
The insulators using polymer materials were developed and undergo an experienced industrial test (Fig. 9, g, e).They are a rod element from fiberglass protected by a coating with ribs from fluoroplast or silicon-carnage rubber. The rod insulators compared with the suspension have less weight and cost, higher mechanical strength than tempered glass. The main problem is to ensure the possibility of their long-term (more than 30 lay) work.
Linear fittings Designed to secure wires to insulators and cables to supports and contains the following main elements: clamps, connectors, remote struts, etc. (Fig. 10). Supporting clamps are used for suspension and fixing the wires of the VL on intermediate supports with bounded stiffness of the sealing (Fig. 10, but).On the anchor supports for rigid fastening of wires, tension garlands and clamps - tension and wedges are used (Fig. 10, B, in).Coupling fittings (earrings, ears, brackets, rocker) is designed for suspension garlands on supports. Supporting garland (Fig. 10, d)it is fixed on the traverse of the intermediate support using an earrings 1 inserted by another side into the header of the upper suspended insulator 2. Usho 3 is used to attach to the lower insulator of the garlands of the supporting clamp 4. Remote struts (Fig. 10, e)mounted in the flights of lines of 330 kV and above with split phases, prevent charming, collision and twisting individual phase wires. Connectors are used to connect separate sections of the wire using oval or pressing connectors (Fig. 10, e, g).In the oval connectors of the wire or twist, or crimped; In the pressed connectors used to connect steel aluminum wires of large sections, steel and aluminum parts are pressed separately.
The result of the development of EE technology for long distances is various options for compact LEPs, characterized by a smaller distance between the phases and, as a result, smaller by the inductive resistance and the width of the line of the line (Fig. 11). When using the support "covering type" (Fig. 11, but)reducing the distance is achieved due to the location of all phase split structures inside the "covering portal" or one side of the support stand (Fig. 11, b). The rapprochement of the phases is provided by interphase insulating spacers. Various variants of compact lines with unconventional schemes for the location of the split phases are proposed (Fig. 11, in-and). In addition to reducing the width of the track per unit of power transmitted, compact lines can be created to transmit increased capacities (up to 8-10 GW); Such lines cause fewer tensions. electric field At the ground level and have a number of other technical advantages.
Compact lines also include controlled self-adensive lines and controlled lines with unconventional configuration of split phases. They are two-chart lines in which the phases of different valuable are shifted in pairs. In this case, voltages shifted to a certain angle are summed up to the chains. Due to the mode changes using special phase shift angle devices, the line parameters are controlled.
Cable power cable lines
Cable line (CL) Line for transmitting electricity, consisting of one or more parallel cables, made in any way of laying (Fig. 11). Cable lines are packed where the construction of the WL is impossible due to the constrained territory, is unacceptable under the safety conditions, it is impractical on economic, architectural and planning indicators and other requirements. The largest application of the CL was found in transmission and distribution of EE at industrial enterprises and in cities (internal power supply systems) during the transfer of EE through large aquatic spaces, etc. The advantages and advantages of cable lines compared to air: impetituding atmospheric impacts, road secrets and unavailability For unauthorized persons, less damage, the compactness of the line and the possibility of widespread the power supply of consumers of urban and industrial areas. However, CL is much more expensive than the air of the same voltage (on average 2-3 times for lines of 6-35 kV and 5-6 times for lines of 110 kV and higher), more complicated during construction and operation.
The CL includes: cable, connecting and end couplings, building construction, fastening elements, etc.
The cable is a ready-made factory product consisting of isolated conductive veins enclosed in a protective hermetic shell and armor protecting them from moisture, acids and mechanical damage. Power cables have from one to four aluminum or copper lived with a cross section of 1.5-2000 mm 2. Cases with a cross section of up to 16 mm 2 -On-focused, over - multi-proper. On the shape of the cross section of the core round, segment or sectorals.
Cables with a voltage up to 1 kV are performed, as a rule, four-core, 6-35 sq. - three-core voltages, and a voltage of 110-220 kV - one-core.
Protective shells are made from lead, aluminum, rubber and polychlorvinyl. In cables with voltage of 35 kV, each lived additionally lies in the lead shell, which will create a more uniform electric field and improves heat removal. Alignment of the electric zero in plastic insulation cables and the shell is achieved by shielding each vein semiconducting paper.
In cables on a voltage of 1-35 kV to increase the electrical strength between insulated cores and the shell, a layer of waist isolation is laid.
The cable armor is performed from steel tapes or steel galvanized wires, protects against corrosion by outer cover from cable broach, impregnated with bitumen and coiled with chalk.
In cables with a voltage of 110 kV and higher, the increase in the electrical strength of paper insulation is filled with gas or oil under excess pressure (gas-filled and oil-filled cables).
In the cable designation mark, information about its design, rated voltage, quantity and cross-section lived. In four-core cables with a voltage of up to 1 kV section of the fourth ("zero"), the veins are less than the phase. For example, HPV-1-3x35 + 1x25 cable - cable with three copper cores in the cross section of 35 mm 2 and the fourth cross section of 25 mm 2 , polyethylene (P) isolation by 1 kV, the shell of polychlorvinyl (B), non-monored, without outdoor cover (g) - for laying indoors, in canals, tunnels, in the absence of mechanical effects on the cable; Cable AOSB-35-3x70 - cable with three aluminum (a) veins of 70 mm 2, with an insulation by 35 kV, with separately disconnected (o) veins, in lead (c) shell, armored (b) steel ribbons, with outdoor protective cover -for gaskets in the earthen trench; OSB-35-3x70 is the same cable, but with copper veins.
The designs of some cables are presented in Figure 13. Figure 13 , and bpower cables voltage up to 10 square meters.
Four cable380 V voltage (see Fig. 13, but)contains elements: 1 - conductive phase veins; 2 - paper phase and waist insulation; 3 - protective shell; 4 - steel armor; 5 - protective cover; 6 - paper filler; 7 - zero lived.
Three-core cablewith paper insulation with a voltage of 10 kV (Fig. 13, b)contains elements: 1 - current-carrying veins; 2 - phase isolation; 3 - total belt isolation; 4 - protective shell; 5 - cushion under armor; 6 - steel armor; 7 - protective cover; 8 - aggregate.
Three-core cablethe voltage of 35 kV is depicted in fig. 1.3, in.It includes - 1 - round conductive veins; 2 - Paul in watering the screens; 3 - phase isolation; 4 - lead shell; 5 - pillow; 6 - cable yarn aggregate; 7 - steel armor; 8 - protective cover.
In fig. 1.3, g.presented oil filled cablemedium and high pressure with a voltage of 110-220 kV. Oil pressure prevents air to its ionization, eliminating one of the main causes of the isolation breakdown. Three single-phase cables are placed in a steel pipe 4 filled with oil 2 under excess pressure. The current-carrying veins 6 consists of copper round wire and covered with paper insulation 1 with viscous impregnation; On top of the insulation, the screen 3 is applied in the form of a copper perforated lepta and bronze wire, protecting insulation from mechanical damage while stretching the cable in the pipe. Outside the steel pipe is protected by cover 5.
The cables in the polychlorvinyl insulation produced by three-, four- and five-housing (1.3, e)or single-linked (Fig. 1.3, e).
Cables are made by segments of limited length depending on. Hiding and cross section. When laying, the segments are connected by connecting couplings, sealing the connection locations. At the same time, the ends of the cores are exempt from isolation and close up in connecting clamps.
When laying in the land of cables 0.38-10 kV for sewn from corrosion and mechanical damage, the connection location is the protective cast iron detachable casing. For 35 kV cables, steel or fiberglass covers are also used. In fig. fourteen, but The compound of a three-core low-voltage cable 2 in the cast-iron coupling 1. The cable ends are fixed by porcelain strut 3 and the loan is connected 4. Cable clutches up to 10 kV with paper insulation are filled with bituminous compositions, cables 20-35 kV - oil-filled. For cables with plastic insulation, connective couplings from heat-suite insulating tubes are used, the number of which corresponds to the number of phases, and one heat-suite tube for zero veins, seated in a heat-suite coupling (Fig. 14, b) . Apply other constructions of connecting couplings.
At the ends of the cables are used end couplings or end sealing. In fig. fifteen, buta mastic-filled three-phase outdoor clutch with porcelain insulators for 10 kV voltage cables is given. For three-core cables with plastic insulation, an end coupling is used, presented in Fig. fifteen, 6. It consists of a thermal shrinkable glove 1, resistant to the effects of the environment, and semiconducting heat-shrinkable tubes 2, with which three single-core cables are created at the end of the three-core cable. Insulating heat-superstitable tubes are put on separate cores 3. They are mounted on them the desired amount of heat-sustainable insulators 4.
For cables 10 kV and below with plastic insulation in the interior, a dry cutter is used (Fig. 15, B). The shaved ends of the cable with insulation 3 are wrapped with a sticky polychlorvinyl ribbon 5 and lacquer; The ends of the cable are sealed with cable weight of 7 and an insulating glove 1, overlapping cable sheath 2, the ends of gloves and cores are additionally compacted and wrapped with a polychlorvinyl tape 4, 5, the latter to prevent the lag and unwinding is fixed with twine bands 6.
The method of cable laying is determined by the terms of the line route. Cables are laid in earthy trenches, blocks, tunnels, cable tunnels, reservoirs, cable overpass, as well as overlapping buildings (Fig. 12).
Most often in the territory of cities, industrial enterprises cables are paved in earthy trenches (Fig. 12, but).To prevent damage due to the deflection at the bottom of the trench, create a soft pillow from a layer of sifted land or sand. When laying in one trench of several cables up to 10 kV, the horizontal distance between them should be at least 0.1 m, between 20-35 kV cables - 0.25 m. The cable is covered with a small layer of the same soil and closed with brick or concrete slabs To protect against mechanical damage. After that, the cable trench falls asleep the earth. In places of transition through roads and in inputs in the building, the cable is paved in asbestos-cement or other pipes. It protects the cable from vibrations and provides the ability to repair without opening the canvas. Trench gasket is the least costly method of cable sewage EE.
In places of laying a large number of cables, aggressive soil and wandering too "limit the possibility of their laying in the ground. Therefore, along with other underground communications, special structures are used: collectors, tunnels ropes, blocks and overpass. The collector (Fig. 12, b) serves to jointly accommodate different underground communications in it: cable power lines and communications, water pipeline through city highways and in large enterprises. With a large number of parallel cable paved, for example, from the building of a powerful power plant, we use a gasket in tunnels (Fig. 12, B). At the same time, the operating conditions are improved, the surface area of \u200b\u200bthe Earth, necessary for laying cables, is reduced. However, the cost of tunnels is very large. The tunnel is intended only for laying cable lines. It is built under the ground from the precast concrete or sewer pipes of a large diameter, the tunnel capacity is from 20 to 50 cables.
At less cables, cable channels are used (Fig. 12, d), closed earth or leaving the surface level of the Earth. Cable overaps and galleries (Fig. 12, e)use for overhead cable laying. This type of cable structures are widely used where the gasket is directly power cables In Earth, it is dangerous due to landslides, collaps, permafrost, etc. In cable channels, tunnels, collectors and overpass cables are packed through the cable brackets.
In large cities and in large enterprises, cables are sometimes laid in blocks (Fig. 12, e) representing asbestos-cement pipes, joints that are covered with concrete. However, the cables are poorly cooled in them, which reduces their bandwidth. Therefore, laying cables in blocks only when they are impossible to lay them in trenches.
In buildings, on walls and overlaps, large streams of cables are placed in metal trays and boxes. Single cables can be opened open along walls and overlaps or hidden: in pipes, in hollow plates and other building parts of buildings.
Tockets, busbars and internal wiring
The conductor is called the power line, the current-growing parts of which are made of one or more rigidly fixed aluminum or copper wires or tires and relate to them supporting and supporting structures and insulators, protective shells (boxes). Shinbore is called protected and closed currents made by rigid tires. Busbins up to 1 kV apply in workshop networks industrial enterprises, more than 1 kV - in the generator voltage chains for EE transmission to increasing transformers of power plants. Terminals 6-35 kV are used for the main nutrition of energy-intensive enterprises at currents of 1.5-6.0 ka. Busbars up to 1 kV industrial enterprises (complete connections) are mounted from standard sections of factory manufacture. Separate sections 1 of such a conductor (Fig. 15, but)consist of boxes with elements placed in them, branching 3 and introductory 2 boxes attached through the branch section 4 to the highway 5. Complete busbar, produced by three- and four-pass (Fig. 15, b)it consists of sections in the form of segments of tires 1, fixed on pads 3 in box 2 with clamps 4 to attach electrostators. The length of such sections under transportation conditions does not exceed 6 m. Busbar box is necessary to protect against external influences, sometimes they are used as a zero conductor.
The rigid symmetric current wire 6-10 kV is performed from the box of the box, rigidly fixed on the supporting insulators attached to the circuit steel construction on the tops of the equilateral triangle. The conductor can be laid open - on supports or overpars, or hidden - in tunnels (Fig. 17) and galleries.
The flexible unified symmetric current line 6-10 kV of external filling is essentially a two-charted VL with split phases (Fig. 18, but).Each phase consists of 4, 6, 8 or 10 of the wires of the brand A 600, located on supporting clamps around the circle with a diameter of 600 mm. With the help of a special suspension system on the insulators, all three phases are placed on the vertices of the triangle and are attached to the supports. An interfacial insulating spacers are installed to prevent the phases of the phases among themselves in flights.
A flexible 35 kV (Fig. 18) of the phases consist of three wires, the stamps A 600 are fixed in the rings and the medium of the carrier steel cable are suspended on the insulators to the support. The supports of flexible conductor, constructed from reinforced concrete or steel, are installed after 50-100 m. Outpack from conductives to electrospiders are performed by tires or bare wires.
Internal electrical wiringcalled wires and cables with electrical installation and electrical products intended for the fulfillment of internal networks in buildings. They are performed open and hidden, in most cases insulated wires laid on insulators or pipes. Cables are laid in the canals, floors or walls. Sometimes the internal electrical wiring also includes containers (busbars) of manufactured networks of industrial enterprises.
| In my world |
3) Wires of the WL should be located, as a rule, above the LS and LPB cable (see also 1.76, p. 4);
4) The connection of the wires of the VL in the intersection span with the suspension cable LS and HPF is not allowed. The cross section of the carrier vein SIP should be at least 35kv.mm. Wires of VL must be a multi-breed section of at least: aluminum - 35kv.mm, steel aluminum - 25 square meters; SIP conductor cross-section with all carriers of harness - at least 25kv.mm;
5) The metal shell of the suspended cable and the cable on which the cable is suspended must be grounded on supports that limit the intersection span;
6) The distance horizontally from the base of the LS cable support and the HPD to the projection of the nearest WP wire to the horizontal plane should be no less than the highest height of the intersection span.
1.78.
When crossing angle with uninsulated LS and LPV wires, the following requirements must be respected:
1) The intersection of the VLI with drugs and HPF can be performed in the span on the support;
2) Ruff supports that limit the span of the intersection with the LS of the main and intra -one communication networks and with the CTC connecting lines must be anchor type. When crossing all the remaining drugs and HDPV, the use of intermediate supports, reinforced with an additional console or troop, is allowed;
3) carrier veins SIP or harness with all carriers of conductors in the intersection area should have a tensile strength ratio with the highest settlement loads of at least 2.5;
4) Wires should be located above the ls and hp. On supports that limit the intersection of the intersection, the carriers of the CIP wires should be fixed by tensioning clamps. Wires were allowed to be placed under the wires of the LDV. At the same time, the wires of the LPV on the supports that limit the intersection of the intersection should have a double fastening;
5) The connection of the carrier and carrier conductors of the SIP harness, as well as the LS and LPV wires in the intersection spans is not allowed.
1.79.
When crossing isolated and uninsulated wires, the following requirements must be followed with uninsulated LS wires and LPVs:
1) The intersection of WL wires with LS wires, as well as the wires of HPV voltage above 360 \u200b\u200bV should be performed only in the span.
The intersection of wires of the WL with subscriber and feeder lines of HPV voltage up to 360 V is allowed to be performed on BL supports;
2) BL supports that limit the injection span must be anchor type;
3) LS wires, both steel and non-ferrous metal, should have a tensile strength reserve coefficient with the highest calculated loads of at least 2.2;
4) Wires of the WL should be located above the WHD and LPV wires. On supports that limit the span intersection, the WL wires must have a double fastening. The wires of the 380/220 Vl voltage and below are allowed to be located under the wires of the LPV and the LINDS of the GTS. At the same time, the wires of LPV and the LINDS of the GTS on the supports that limit the intersection of the intersection should have a double fastening;
5) The connection of the wires of the VL, as well as the LS and LPV wires in the intersection spans is not allowed. VL wires must be multi-proper cross-sections: aluminum - 35kv.mm, steel aluminum - 25kv.mm.
1.80.
When crossing the underground cable insert in WL with uninsulated and insulated wires, the LS and LPV must comply with the following requirements:
1) the distance from the underground cable insert in VL to the support of the drugs and the LPV and its earthing should be at least 1M, and when the cable is laying in an insulating pipe - not less than 0.5 m;
2) The distance horizontally from the base of the cable support VL to the projection of the nearest LS wire and the HPV on the horizontal plane should be at least the highest height of the intersection span.
1.81.
The distance horizontally between the wires of the VLI and the LS wires and the HPV with parallel passage or convergence should be at least 1 m.
Under the rapprochement of WL with air drugs and LPV, the horizontal distance between isolated and uninsulated wires of VL and Wires of LS and HPV should be at least 2m. In cramped conditions, this distance is allowed to be reduced to 1.5 m. In all other cases, the distance between the lines should be at least the height of the highest support for VL, LS and LPV.
Under rapprochement of WL with underground or suspended LS cables and holy distances, the distance between them should be taken in accordance with 1.77 PP. 1 and 5.
1.82. The rapprochement of VL with the antenna structures of transmitting radio centers, receiving radio centers, dedicated receiving points of wired broadcasting and local radio cores is not normalized.
1.83. The wires from the support of VL before entering the building should not be intersecting with wires of branches from the drugs and HDPs, and they should be placed at one level or above the LAN and LPV. The horizontal distance between the wires of the VL and the LS and LPV wires, television cables and the descents from the radiance on the inputs should be at least 0.5 m for SIP and 1.5 m for uninsulated VL wires.
1.84.
The joint suspension of the suspended cable of the rural telephone and was allowed when performing the following requirements:
1) Zero lived SIP should be isolated;
2) the distance from the SIP to the stem cable of the STS in the span and on the Blue support should be at least 0.5 m;
3) Each blast blast must have a grounding device, while the ground resistance must be no more than 10 ohms;
4) On each support, the PEN conductor must be re-ground;
5) The carrier rope of the telephone cable together with the metal mesh outer cover of the cable must be attached to the earthinger of each support by a separate independent conductor (descent).
1.85.
A joint suspension on common supports of uninsulated wires of VL, LS and LPV is not allowed.
On common supports, a joint suspension of uninsulated wires of VL and insulated wires of HPF is allowed. The following conditions must be respected:
1) the rated voltage of the WL should be no more than 380 V;
3) the distance from the lower wires of the LPV to the Earth, between the chains of LPV and their wires must comply with the requirements of the current Rules of the Ministry of Communications of Russia;
4) non-insulated wire wires should be located above the wires of the LDF; At the same time, the distance vertically from the lower wire of the VL to the upper wire of the LDV should be on the support of at least 1.5 m, and in the span - at least 1.25m; When the LPV wires are arranged on the brackets, this distance is taken from the lower wire of the VL located on the same side as the wires of the LPV.
1.86.
On common supports, a joint suspension of SIP was allowed with non-insulated or insulated wires of LS and LPV. The following conditions must be respected:
1) The rated voltage of the blast should be no more than 380 V;
2) the rated voltage of the LDF should be no more than 360 V;
3) Nominal voltage of drugs, the calculated mechanical stress in the WATS wires, the distance from the lower wires of the LAN and HPF to the Earth, between the chains and their wires must comply with the requirements of the current Rules of the Ministry of Communications of Russia;
4) Wires of VLI up to 1 kV should be located above the ls and hp. At the same time, the distance vertically from the SIP to the top wire of the LS and the LPV, regardless of their mutual location, should be at least 0.5 m on the support and in the span. Wires of VLI and LS and LPV are recommended to be located on different sides of the support.
1.87.
A joint suspension on common supports of uninsulated wires of VL and LS cables is not allowed. The joint suspension on the total supports of the wires of the voltage voltage of no more than 380 V and the LPV cables are allowed when compliance with the conditions.
Optical fibers Window must meet the requirements.
1.88. The joint suspension on the common supports of the wires of the voltage of no more than 380 V and the wires of telemechanics is allowed when compliance with the requirements given in 1.85 and 1.86, as well as if the telemechanic chains are not used as wired telephone channels.
1.89.
Suspension of fiber-optic communication cables (OK) is allowed on the supports of VL (VLI):
non-metallic self-supporting (OXN);
non-metallic, piled on the phase wire or zhgut SIP (window).
Mechanical calculations of WL (VLI) supports with OCSN and the window should be made for the initial conditions specified in 1.11 and 1.12.
Supports Vl, on which ok hang, and their fixing in the soil should be calculated taking into account additional loads arising from this.
The distance from the Oxn to the surface of the Earth in the populated and unanimous locations should be at least 5 m.
The distances between the wires of VL to 1 kV and the OCCN on the support and in the span should be at least 0.4 m.
Page 5 of 14
The electrical air linage is called a device that serves to transmit electrical energy by wires located outdoors and attached with the help of insulators and reinforcements to supports. Air lines of power lines are divided into voltage to 1000 V and above 1000 V.
During the construction of air lines of power, the volume of earthworks is insignificant. In addition, they differ simplicity of operation and repair. The cost of the construction of the air line is approximately 25-30% less than the cost of the cable line of the same length. Air lines are divided into three classes:
class I - lines with a nominal production voltage of 35 kV with consumers 1 and 2nd categories and above 35 kV regardless of consumer categories;
class II - lines with a nominal operational voltage of 1 to 20 kV with consumers 1 and 2nd categories, as well as 35 kV with consumers of the 3rd category;
Class III - lines with a nominal operational voltage of 1 kV and below. A characteristic feature of the air line voltage up to 1000 V is the use of supports for simultaneous mounting of radio network wires, outdoor lighting, television, alarm system. The main elements of the airline are supports, insulators and wires.
For lines with a voltage of 1 kV, the supports of two types are used: wooden with reinforced concrete consoles and reinforced concrete.
For wooden supports, logs are used, impregnated with antiseptic, from the forest II grade - pines, ate, larch, fir. Do not impregnate logs in the manufacture of supports from the forest hardening of the winter logging. The diameter of the logs in the upper cut should be at least 15 cm for single-suitable supports and at least 14 cm for double and A-like supports. It is allowed to take the diameter of the logs in the upper cut at least 12 cm on branches that go to the inputs in the building and facilities. Depending on the purpose and design, intermediate, angular, branch, cross-end and end are distinguished.
Intermediate supports on the lines are the most numerous, as they serve to maintain wires at height and are not designed for efforts that are created along the line in case of wire break. To perceive this load, anchor intermediate supports are installed, having their "legs" along the line axis. For perception of efforts, perpendicular lines, anchor intermediate supports are installed, placing "legs" supports across the line.
Anchor supports have a more complex design and increased strength. They are also divided into intermediate, angular, branches and end, which increase the overall strength and stability of the line.
The distance between the two anchor supports is called an anchor span, and the distance between the intermediate supports is the pitch of the supports.
In places to change the direction of the airline route, corner supports are installed.
For the power supply of consumers, which are at some distance from the main airline, the branch supports are used on which the wires connected to the air line and to the input of the power consumer.
End supports are installed at the beginning and end of the airline specifically for perceiving one-sided axial effort.
Designs of various supports are shown in Fig. 10.
When designing the airline, the number and type of supports are determined depending on the configuration of the track, the cross-section of the wires, the climatic conditions of the area, the degree of population of the area, the relief of the track and other conditions.
For structures, the voltage of above 1 kV is used mainly reinforced concrete and wooden antiseptic supports on reinforced concrete consoles. The designs of these supports are unified.
Metal supports are mainly used as anchor supports on air lines with voltage above 1 kV.
On the plugs, the location of the wires can be any, only zero wire in the lines up to 1 kV are placed below the phase. On the suspension on the supports of the wires of the outer lighting, they are placed below the zero wire.
Wires voltage up to 1 kV should be swallowed at an altitude of at least 6 m from the ground, taking into account the arrow of the Provision.
The distance vertically from the Earth to the point of the highest wire wire is called the dimension of the WP wire above the ground.
The wires of the airline can close on the highway with other lines, intersect with them and pass at a distance from objects.
The dimensions of the rapprochement of WL wires are called a permissible smallest distance from the wires of the line to objects (buildings, structures) located in parallel to the VL highway, and the intersection is the shortest distance vertical from the object located under the line (intersectable) to the WL wire.
Fig. 10. Designs of wooden supports of air lines:
but - on voltage below 1000 V, b. - on voltage 6 and 10 kV; 1
- intermediate, 2
- angular with a troop, 3
- Corner with delay, 4
- Anchor
The mounting of the wires of the airline on the supports is carried out using insulators (Fig. 11), placed on hooks and pins (Fig. 12).
For air lines with a voltage of 1000 V and below, the TF-4, TF-16, TF-20, NS-16, NS-18, AIK-4, and for branches - 12, at a cross section of wires up to 4 mm 2, is used; TF-3, AIK-3 and SHO-16 when crossing wires up to 16 mm 2; TF-2, AIK-2, SHO-70 and SCN-1 with a cross-section of wires to 50 mm 2; TF-1 and AIC-1 when the wires section are up to 95 mm 2.
To mount the wires of air lines with a voltage above 1000V, insulators of SC, SD, GLL, SEC6-A and SCF10-A and suspended insulators are used.
All insulators, in addition to suspended, are tightly screwed down on hooks and pins, which are pre-wound a pass, impregnated with sudic or olifa, or put on special plastic caps.
For a voltage of up to 1000 V, KN-16 hooks are used, and above 1000 V - the hooks of the kV-22, made of round steel with a diameter, respectively, 16 and 22 mm 2. On the traverses of the supports of the same air lines to 1000 V, with the fastening of the wires, pcs-d pcs are used for wooden traverse and pcs - for steel.
At the voltage of air lines, more than 1000 in the traverses of the supports are mounting pins Shchu-22 and Shu-24.
Under the terms of the mechanical strength for air lines with voltage up to 1000 V, single-robust and many wire wires are used, not less: aluminum - 16 steel aluminum and bimetallic -10, steel multi-level - 25, steel single-wire - 13 mm (diameter 4 mm).
On the air line with a voltage of 10 kV and below passing in non-heated area, with a calculated thickness of the ice-generated layer of ice (the ice wall) to 10 mm, in flights without intersections with structures, it is allowed to use single-rocker steel wires in the presence of a special indication.
In flights that intersect pipelines that are not intended for combustible liquids and gases are allowed to use steel wires with a cross section of 25 mm 2 or more. For air lines, the voltage above 1000 V is used only by a multi-voltage copper wire with a cross section of at least 10 mm 2 and an aluminum cross section of at least 16 mm 2.
The connection of the wires with each other (Fig. 62) is performed by a twist, in the connecting clamp or in spot clips.
The mounting of the wires of the VL and insulators is carried out by knitting wire with one of the methods shown in Fig. 13.
Steel wires are tied with a soft steel galvanized wire with a diameter of 1.5 - 2 mm, and aluminum and steel aluminum - aluminum wire with a diameter of 2.5 - 3.5 mm (the wire of multi-voltage wires can be used).
Aluminum and steel-aluminum wires in the mounting places are pre-wrapped with an aluminum ribbon to protect them from damage.
On intermediate supports, the wire is fasten mainly on the head of the insulator, and on the corner supports - on the neck, having it from the outside of the angle, and the lines of the lines. The wires on the head of the insulator are fixed (Fig. 13, a) with two cuts of knitting wire. The wire is twisted around the insulator head so that the ends of it from different lengths are on both sides of the neck of the insulator, and then two short end winds 4 - 5 times around the wire, and two longs are transferred through the insulator head and also wipe around the wire several times. When mounting the wire on the neck of the insulator (Fig. 13, b), the knitting wire covers the loop of the wire and the neck of the insulator, then one end of the knitted wire is wrapped around the wire in one direction (from top to bottom), and the other end is in the opposite direction (bottom-up).
On anchor and end supports, the wire is fixed with a cap on the cervix. In places of transition, VL through railways and tramways, as well as in the intersections with other power lines and communication lines, use double fastening of wires.
All wooden details when assembling supports tightly customize to each other. The clearance in places of wrist and joints should not exceed 4 mm.
Racks and consoles to the supports of air lines are performed in such a way that wood in the place of the interface did not have bitch and cracks, and the junction was completely dense, without cleansing. The working surfaces of the wrist should be solid propil (without wood slot).
The holes in the logs are drilled. It is forbidden to burn holes with heating rods.
Bandages for conjugation of prefixes with support are made of soft steel wire with a diameter of 4 - 5 mm. All bandage turns must be evenly stretched and fit tightly to each other. In case of cliff one turn, the entire bandage should be replaced with a new one.
When connecting wires and cables, the voltage above 1000 V in each span is allowed no more than one connection to each wire or cable.
When using welding to connect the wires, there should be no faster of the outer oops or welding disturbance during the junction of the connected wires.
Metal supports, protruding metal parts of reinforced concrete supports and all metal parts of wooden and reinforced concrete BL supports are protected by anti-corrosion coatings, i.e. paint. The places of mounting welding of metal supports are coated and stained on a width of 50 - 100 mm along the weld immediately after welded. Parts of structures that are subject to concrete are covered by cement milk.
Fig. 14. Methods for fastening wires viscous to insulators:
but - Head knitting, b. - Side binding
During operation, the power lines of the transmission periodically examine, and also produce prophylactic measurements and verification. The amount of wood reloading is measured at a depth of 0.3 - 0.5 m. The support or prefix is \u200b\u200bconsidered unsuitable for further operation, if the depth of rotting along the log radius is more than 3 cm when the log diameter is more than 25 cm.
Extraordinary VL inspections are held after accidents, hurricanes, in a fire near the line, during ice-frequency, ice, frost below -40 ° C, etc.
When a multiple wire discovery is detected on a cliff with a common cross section of up to 17% of the cross section of the wire, the breakdown area is overlapped with a repair coupling or bandage. The repair coupling on the steel aluminum wire is installed when cutting up to 34% of aluminum wires. If a larger amount of lived is cut, the wire must be cut and connected by the connecting clamp.
Insulators can have trifles, burns of glaze, melting metal parts and even the destruction of porcelain. This occurs in the case of a breakdown of electrical arc insulators, as well as the deterioration of their electrical characteristics as a result of aging during operation. Often, the tributes of insulators occur due to severe contamination of their surface and at stresses exceeding the working. Data on defects detected during inspections of insulators are logged in a magazine of defects, and on the basis of these data makes plans for repair work of air lines.
The cable line is a line for transmitting electrical energy or individual pulses consisting of one or more parallel cables with connecting and end couplings (sealing) and fasteners.
The underground cable lines establish security zones, the size of which depends on the voltage of this line. Thus, for cable lines with a voltage up to 1000, the security area has the size of 1 m on each side from extreme cables. In cities under the sidewalks, the line should take place at a distance of 0.6 m from buildings and structures and 1 m from the carriageway.
For cable lines with voltage above 1000, the security area has a size of 1 m on each side from extreme cables.
The underwater cable lines voltage up to 1000 V and above have a security zone, determined by parallel straight at a distance of 100 m from the extreme cables.
The cable route is chosen taking into account its smallest consumption and ensure the safety of mechanical damage, corrosion, vibration, overheating and the possibility of damage to neighboring cables when a short circuit occurs on one of them.
When laying cables, it is necessary to observe the maximum allowable radii of their bend, the excess of which leads to a violation of the integrity of the insulation lived.
Laying the cable in the ground under buildings, as well as through basements and warehouses Forbidden.
The distance between the cable and the foundations of the buildings should be at least 0.6 m.
When laying a cable in the area of \u200b\u200bplantings, the distance between the cable and trunks of the trees should be at least 2 m, and 0.75 m is allowed in the green zone with shrub landings. In the case of a cable laying in parallel with heat pipes, the distance in the light from the cable to the wall of the heat pipe channel should not be less than 2 m, to the axis of the railway path - at least 3.25 m, and for an electrified road - at least 10.75 m.
When laying a cable parallel to the tram paths, the distance between the cable and the tram axis should be at least 2.75 m.
In places intersection of iron and highways, as well as tram tracks, cables are paved in tunnels, blocks or pipes across the width of the alienation zone at a depth of at least 1 m from the canvas and at least 0.5 m from the bottom of the drainage channels, and in the absence of a zone Alienation Cables are paved directly on the intersection area or at a distance of 2 m on both sides of the canvas.
The cables are placed with a "snake" with a margin of 1 - 3% of its length in order to eliminate the possibility of hazardous mechanical stresses when soil displacements and temperature deformations. Stop the end of the cable in the form of rings is prohibited.
The number of connecting couplings on the cable should be the smallest, so the cable is paved with complete construction lengths. For 1 km of cable lines, there may be no more than four couplings for three-core cables with a voltage up to 10 kV cross section to 3x95 mm 2 and five couplings for sections from 3x120 to 3x240 mm 2. For single-core cables, no more than two couplings per 1 km of cable lines are allowed.
For connections or termination of the cable, the ends are cut, that is, the stepwise removal of protective and insulating materials. The cutting dimensions are determined by the coupling design, which will be used to connect the cable, the cable voltage and the cross section of its conductive livers.
The finished cutting of the end of a three-core cable with paper insulation is shown in Fig. fifteen.
Connection of the ends of the cable with a voltage to 1000 V is carried out in cast iron (Fig. 16) or epoxy clutches, and a voltage of 6 and 10 kV - in epoxy (Fig. 17) or lead couplings.
Fig. 16. Connecting cast iron coupling:
1
- upper coupling, 2
- Winding of resin tape, 3
- porcelain strut, 4
- lid, 5
- tightening bolt, 6
- grounding, 7
- lower demumuft, 8
- Connecting sleeve
The connection of conductive cable veins with a voltage to 1000 V is performed by crimping in the sleeve (Fig. 18). To do this, they are selected by the section of the connected conductive conductive livelines, the punch and the matrix, as well as the mechanism for crimping (press clamp, hydropress, etc.), clean the inside surface of the sleeve with a steel hero (Fig, 18, a), and connected veins - Brush - for cards (Fig. 18, b). Multi-voltage sectoral cables cable versatile pliers curve. Enter veins in the sleeve (Fig. 18, c) so that their ends come into contact and were located in the middle of the sleeve.
Fig. 17. Connecting epoxy coupling:
1
- Wire bandage, 2
- Coupling case, 3
- Bandage of harsh threads, 4
- strut, 5
- Winding veins, 6
- ground wire, 7
- connection lived, 8
- Sealing winding
Fig. 18. Connection of copper cable Cable Pressing:
but - sweeping of the inner surface of the sleeve with steel wireno b. - Stripping the veins with a brush of cards, in - Installation of the sleeve on the connected veins, g. - crimping sleeves in the press, d. - Ready connection; 1
- Copper sleeve, 2
- Ersh, 3
- Brush, 4
- lived, 5
- Press
Install the sleeve flush in the file of the matrix (Fig. 18, d), then the sleeve is pressed with two pressing, one by one for each vein (Fig. 18, e). Paving is produced in such a way that the Puinson's washer at the end of the process rested into the end (shoulders) of the matrix. The residual cable thickness (mm) is checked with a special caliper or kronzirkul (value N.in fig. nineteen):
4.5 ± 0.2 - when cross section of the connected lived 16 - 50 mm 2
8.2 ± 0.2 - with a section of the connected lived 70 and 95 mm 2
12.5 ± 0.2 - with a section of the connected lived 120 and 150 mm 2
14.4 ± 0.2 - during the section of the connected lived 185 and 240 mm 2
The quality of the compressed cable contacts check the external inspection. In this case, pay attention to the junction wells, which should be placed coaxially and symmetrically relative to the middle of the sleeve or tubular part of the tip. In places of pressure, Punson should not be supervisors or cracks.
To ensure the appropriate quality of crimping cables, you need to perform the following conditions for the production of work:
apply tips and sleeves, the cross section of which corresponds to the construction of the cable vein to be terminated or connected;
use matrices and punches corresponding to sizes of tips or sleeves used in crimping;
Do not change the cable vein section to facilitate the input of the veins in the tip or the sleeve by removing one of the wire;
do not press without preliminary stripping and lubrication of quartz-vaseline paste of contact surfaces of tips and sleeves on aluminum veins; Finishing crimping no earlier than Puinson's washer fit close to the torch of the matrix.
After connecting the cable, the cable was removed from the metal belt between the first and second ring shell cutters and the bandage from 5-6 turns of harsh threads was applied to the edge of the waist insulation, after which the spacer plates are installed between the cores so that the cable veins deterled at a certain distance from each other. friend and from the coupling case.
The ends of the cable in the coupling are placed, pre-winding i on the cable in the fields of input and output from the coupling of 5 to 7 layers of the resin ribbon, and then fasten both halves of the coupling bolts. The grounding conductor soldered to the armor and the cable shell at the fastening bolts and thus firmly fix it on the coupling.
Operations of the cutting ends of the cables with a voltage of 6 and 10 kV in the lead clutch are not much different from similar compound operations in the cast-iron coupling.
Cable lines can provide reliable and durable work, but only subject to the compliance with the technology of installation work and all the requirements of the maintenance rules.
The quality and reliability of the mounted cable clutches and seals can be enhanced, if applied when installing the kit of the required tool and fixtures for cutting the cable and the compounds of the core, heating cable mass, etc. The personnel qualifications of the personnel are of great importance for improving the quality of the work performed.
For cable connections, sets of paper rollers, rolls and bobbins cotton yarn are used, but it is not allowed so that they have folds, needed and crumpled spaces have been contaminated.
Such kits deliver in banks depending on the size of the couplings by numbers. The bank at the installation site before use should be opened and warmed up to a temperature of 70 - 80 ° C. Preheated rollers and rolls check for no moisture by immersion paper belts In a heated temperature of 150 ° C paraffin. It should not be observed crackling and separation of foam. If the moisture is discovered, the set of rollers and rolls are braked.
The reliability of cable lines during operation supports the execution of a set of activities, including control over the heating of the cable, inspections, repairs, preventive tests.
To ensure long-term operation of the cable line, it is necessary to monitor the temperature of the cable, as the insulation overheating causes an acceleration of aging and a sharp reduction in the service life of the cable. The maximum allowable temperature of the conductive cable veins is determined by the cable design. So, for cables with a voltage of 10 kV with paper insulation and viscous unscrewing impregnation, a temperature is allowed no more than 60 ° C; For cables with a voltage of 0.66 - 6 kV with rubber insulation and viscous unscrewing impregnation - 65 ° C; for cables with a voltage of up to 6 kV with plastic (from polyethylene, self-tapping polyethylene and polyvinyl chloride plastic) insulation - 70 ° C; For cables with a voltage of 6 kV with paper insulation and depleted impregnation - 75 ° C; For cables with a voltage of 6 kV with plastic (from vulcanized or self-tapping polyethylene or paper insulation and viscous or depleted impregnation - 80 ° C.
Durable current loads on cables with impregnated paper, rubber and plastics are chosen according to valid gta stations. Cable lines with a voltage of 6-10 kV, carrying loads less nominal, can be briefly overloaded by a value that depends on the type of gasket. For example, a cable laid in the ground and having a preload coefficient of 0.6 may be overloaded by 35% for half an hour, by 30% - 1 h and 15% - 3 hours, and with a preload ratio of 0.8 - by 20% for half an hour, by 15% - 1 hour and 10% - 3 hours.
For cable lines in operation for more than 15 years, overload decreases by 10%.
The reliability of the cable line is largely depends on the proper organization of operational supervision over the state of the lines and their tracks through periodic examinations. Planned inspections allow you to identify various violations on cable tracks (earthwork production, warehousing of cargo, planting of trees, etc.), as well as cracks and chips on end-couplings insulators, weakening their fasteners, the presence of bird nests, etc.
A greater hazard for the intake of cables is excavations of the Earth produced on the tracks or near them. Organization operating underground cablesmust allocate by the production of excavations in order to eliminate the damage to the cable.
Places of production of earthworks According to the degree of danger of damage to cables are divided into two zones:
I zone - land plot located on the cable track or up to 1 m from the extreme cable with a voltage above 1000 V;
II zone - plot of land, located from the extreme cable at a distance of more than 1 m.
When working in the I zone, it is prohibited:
use of excavators and other earthmoving machines;
Use of shock mechanisms (wedge-women, ball-women, etc.) at a distance closer than 5 m;
The use of mechanisms for the excavation of the soil (jackhammers, electromotts, etc.) to a depth of 0.4 m at a normal depth of the cable (0.7 - 1 m); Earth production in winter time without prior heating of soil;
Performance of work without supervision by the representative of the operating cable line of the organization.
In order to identify the detects of the insulation of the cable, connecting and end couplings and to prevent the sudden yield of the cable or destruction of its short circuit currents, carry out prophylactic tests of cable lines with increased DC voltage.
The air transmission line (VL) is called a device for transmitting and distributing electricity over the wires in the open air c attached with insulators and fittings in supports or brackets of engineering structures (bridges, overpasses, etc.). The VL device, its design and construction must comply with the "rules of the electrical installation device" (PUE), which are mandatory for all power lines, except for special (for example, contact networks tram, trolleybus, railway, etc.)
Classification and operating modes VL. The power lines of the power lines are usually designed to transfer the variable three-phase current and are divided into:
- supervalted voltage of 500 sq and above, which are mainly used for communication between individual power systems;
- the main voltage of 220 and 330 kV, which serve to transmit energy from powerful power plants, as well as for communication between power systems and pooling power plants inside power systems (usually combine power plants with distribution points);
- distribution voltage 35, software and 150 kV, which serve to power enterprises and settlements of large areas (combine distribution points with consumers and are branched networks with transformer substations);
- 20 kV power lines and below, employees for supplying electricity to consumers.
Electricity consumers of power supply reliability are divided into three categories:
- The first includes consumers, a violation of the power supply of which can lead to danger to the life of people, damage to equipment, mass marriage of products, violation of important elements of urban economy;
- to the second - consumers, the break of the power supply of which leads to a massive bearing of products, the downtime of equipment and workers, violation of the normal activity of a significant part of the urban population;
- To the third - the rest of consumers.
By voltage, the power lines of the power lines "the rules of the electrical installation device" are divided into two groups: voltage to 1000 V (low-voltage) and voltage above 1000 V (high-voltage). For each line of lines, the technical requirements of their device are installed. The nominal linear voltage of three-phase current lines is regulated by GOST 721-62 and can have the following values: 750, 500, 330, 20, 10, 150, 110, 35, 20, 10, 6 and 3 kV, and also 660, 380 and 220 V.
On the electrical mode of operation of the line are divided by. Lines with an isolated neutral, when the total point of the windings (neutral) is not attached to the grounding device or is attached to it through the devices having a large resistance, and with a deaf-free neutral, when the generator neutral or transformer is tightly connected to the ground.
In networks with an isolated neutral, the insulation of the line should be at least the linear voltage value, since when the same phase is closed to the ground, the voltage of the two other phases relative to the Earth becomes equal to linear. In networks with a deaf-free neutral, when damaged of one phase, a short circuit occurs through the ground and the line protection turns off the damaged area. In this case, the phase overvoltage does not occur and the insulation of the line is selected by phase voltage. The disadvantage of these networks is the large value of the earth closure and turn off the line with a single-phase closure on the ground. In our country, a deaf-free neutral network is used in voltage systems up to 1000 V and from 110 kV and higher.
Depending on the mechanical state, the following modes of operation VL are distinguished:
- Normal - wires and cables are not cut off;
- emergency - wires and cables are turned off completely or partially;
- Mounted - in terms of installation of supports, wires and cables.
Mechanical loads on elements were largely dependent on the climatic conditions of the area and the nature of the terrain on which the line passes. When designing, the base is based on the largest value of the wind speed and the wall thickness of the ice, which is formed on the wires, observed in the area 1 time in 15 years for the voltage of 500 kV and 1 time in 10 years for a voltage of 6-330 kV.
The terrain on which the VL passes, depending on the availability for people, transport and agricultural machinery, is divided according to PUE into three categories:
- The locality includes the territory of cities, towns, Teres-Ven, industrial and agricultural enterprises, ports, marins, railway stations, parks, boulevards, beaches, taking into account the boundaries of their development for the next 10 years;
- Unanvertered territory partially visited by people and accessible to transport and agricultural machinery (non-residential areas, gardens, gardens and terrain with separate, rare buildings and temporary facilities are also considered to be;
- To the hard-to-reach territory, inaccessible to transport and agricultural machinery.
Device and basic elements of VL. Electricity air lines consist of supporting structures (supports and bases), wires, insulators and linear reinforcement. In addition, the VL includes devices needed to ensure uninterrupted power supply of consumers and normal line operation: lightning cables, arresters, grounding, as well as auxiliary equipment for the needs of operation (high-frequency communication devices, capacitive power take-off, etc.)
Power line supports support the wires at a given distance between themselves and from the surface of the Earth, horizontal distances between the centers of two supports, on which the wires are suspended, called the span, or a length of the span. Distinguish between transition, intermediate and anchor spans. Anchor span usually consists of several intermediate.
The angle of rotation of the line is called the angle between the direction of the line in adjacent spans.
The vertical distance of the HG (Figure 1, a) between the lower point of the wire in the span to intersectable engineering structures or to the surface of the Earth or water is called the dimensions of the wire.
Figure 1 - Gabritis (A) and Provo Strela (b) Wiring:
F, F - Wire Provision Arrow; HG-envelope wires from the ground, and, in - Wire suspension points
The wire of the wire F wires call the vertical distance between the lower point of the wire in the span and the horizontal straight line, connecting the suspension points of the wire suspension on the supports. If the height of the attachment points is different, the prior arrow is considered relative to the highest and lower points of fastening of the wire (F and F in Figure 1, b).
Treatment is called the effort with which the wire or cable is pulled on the supports. The tension varies depending on the strength of the wind, the ambient air temperature, the thickness of the ice on the wires and may be normal or weakened.
The reserves of the strength, or the reserve coefficient of the elements of the power line, is called the ratio of the minimum estimated load that destroys this element to the value of the actual load in the most difficult conditions.
The mechanical voltage of the material is called the load on the elements of the VL, attributed to the unit of the area of \u200b\u200btheir working section. For example, the tension of the wire belonging to its cross section determines the mechanical stress of the material of the wire.
The time resistance is called the maximum allowable mechanical stress of the material, after which the destruction of the product begins.
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