Installation of cable structures. Power cable design. Feeding devices and oil pressure signaling of cable oil-filled lines

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On cable structures, wires and cables are laid openly along walls and ceilings.
Before laying, inspect the condition of the cables on the drums. Then, using a megohmmeter, the integrity of the core insulation is determined.
For laying cables, load-bearing structures assembled from perforated metal profiles and fasteners (brackets, bolts, nuts and washers) are used. Single cables are laid on hanging hooks fixed in racks (Fig. 1).
Cables with an outer diameter of more than 18 mm, laid horizontally or vertically, must have supports 4-10 m long. At the same time, cables laid on horizontal straight sections are not fixed on supports, and cables laid on vertical sections are fixed on each support.
Regardless of the arrangement of the supporting cable structures, the cables are fixed at a distance of no more than 0.5 m from junction boxes, couplings and end fittings.

Rice. 1. Prefabricated cable structures of the "Christmas tree" type: a - rack; b - shelf; in - bracket; g - suspension; d - fire-resistant partitions; e - stand with pendants; 1 - language; 2 - shank; 3 - oval hole of the shank; 4 - cable; 5 - asbestos-cement partition; 6- connector; 7 - suspension
When securing unarmoured cables, care must be taken not to damage their sheath. For this, elastic gaskets are used for supports and brackets, which should be 5-6 mm wider than them.
Indoor cables with a PVC sheath are laid in places where they cannot be damaged by rodents, or they are protected by boxes or nets.
Cable structures of the "herringbone" type, manufactured in factories, consist of perforated racks and shelves. Trough-shaped racks are made of sheet steel 2.5 mm thick and 400, 600, 800, 1200 and 1800 mm high. Depending on the height, the racks have 8, 12, 16, 24 and 36 shaped holes for placing cable shelves with different or equal distances within one rack.

Rice. 2. Installation of cable structures:
a - wall-mounted;: b - single-sided ceiling; a - double-sided ceiling; g - block (double) structures; 1 - shelf; 2- rack; 3 and 4 - corners

Cable shelves are made in lengths of 160, 250, 350 and 450 mm. The oval holes of the shelves allow cables to be fastened at a certain distance from each other, the special design of the joint between the shelf and the rack does not require welding (the exception is the structures used for vertical cable routing).
Cable structures are painted or galvanized. Galvanized structures are used in outdoor installations, in damp, especially damp and hot rooms, as well as in rooms with a chemically active environment of internal electrical installations, in cable mezzanines, basements and tunnels (regardless of the environment), in other cases, painted structures are used.
Cable structures with hangers consist of racks and embedded hangers. Racks with a height of 600, 800, 1200 and 1800 mm are manufactured at the MEZ by transverse cutting of factory-made perforated profiles (channels). Embedded hangers of three sizes during assembly of structures are inserted into the oval holes of the racks with the narrow side of the shank, and then turned by 90 ° are set to a horizontal position.
When laying cable lines, they tend to combine routes, combining cables into common streams placed on common structures. At the same time, cable structures are installed along the walls of rooms and cable structures, and also suspended from ceilings, beams and other building elements of buildings.
Depending on the installation method and the number of cables to be laid, single and block structures are used from racks and shelves or racks and embedded suspensions: wall, ceiling one-sided and two-sided, double (Fig. 2). In wall and ceiling blocks, cable structures in the MEZ are combined into transportable length sections (up to 6 m) with the help of General connections (girders).
Cable structures, depending on the place of their installation in rooms and cable structures, are welded to embedded elements or metal structures.
Cable racks can be attached to building bases by shooting with dowels using special overhead brackets.

Technical conditions for laying cable lines.

Cable lines must be designed in such a way that during installation and operation, the possibility of dangerous mechanical stresses and damages in them is excluded. To this end:
cables are laid with a margin in length sufficient to compensate for possible soil displacements and temperature deformations of both the cables themselves and the structures along which they are laid;
cables laid horizontally along structures, walls, floors, are rigidly fixed at the end points, directly at the end fittings, on both sides of the bends and at the connecting and locking couplings;
cables laid vertically along structures and walls are fixed in such a way that the deformation of the shells is prevented and the connections of the cores in the couplings are not broken under the action of the cable's own mass;
structures on which unarmored cables are laid are made in such a way that the possibility of mechanical damage to the cable sheaths is excluded; in places of rigid fastening, the sheaths of these cables are protected from mechanical and corrosion damage by elastic gaskets;
cables (including armored ones) located in places where mechanical damage is possible (movement of vehicles, mechanisms and goods, accessibility for unauthorized persons), protect in height by 2 m from the floor or ground level and by 0.3 m in the ground;
cables are laid from heated surfaces at a distance that prevents them from heating above the permissible level, while providing for the protection of cables from the breakthrough of hot substances at the installation sites of valves and flange connections;
cables protect against stray currents and soil corrosion;
designs of underground cable structures are selected taking into account the mass of cables, soil, road surface and the load from passing vehicles;
when laying cables, they withstand certain bending radii;
when laying cables on vertical and inclined sections of routes, the maximum allowable level differences are taken into account;
tensile forces when laying cables and pulling them in pipes are limited depending on the mechanical stresses allowed for conductive cores and sheaths.

Rice. 3. Attaching cables to structures:
a - one with a diameter of 22-34 mm with a single-blade bracket; b - one with a diameter of 12-60;. mm two-arm bracket; a - two with a diameter of up to 20 mm with a bracket; g ~ two overlays with a diameter of more than 20 mm; 5 - three 12-20 mm staples; 1 - cable; 2 - single-arm bracket; 3 - bolt; 4 - cable shelf; 5 - Thai;
6 and 7 - two-leg brackets; 5 - overlay
To compensate for temperature changes in cables and structures along which they are laid, in cable structures and industrial premises, cables are laid with a margin of 1-2% of the total length of the route.
For rigid fastening of cables laid horizontally along structures, brackets, clamps or linings are used, the size of which is chosen depending on the outer diameter of the cables (Fig. 3). On the vertical sections of the route, the distance between the points of rigid fastening of the cables is assumed to be 1 m.
In places of rigid fastening of unarmored cables with a lead or aluminum sheath, elastic gaskets made of non-combustible material (for example, asbestos sheet, polyvinyl chloride sheet) are tried on structures. Unarmored cables with a plastic sheath or a plastic hose are attached to the structure with brackets (clamps) without gaskets. To protect cables in places where mechanical damage is possible, cut steel pipes or sheet metal casings are used.
The radii of the internal bending curve of the cables during laying are allowed at least the following multiplicity / in relation to their outer diameter:
stranded in a lead sheath. . . , . ... , 15
single-core in an aluminum or lead sheath and stranded in an aluminum sheath. . . . , . . , . 25
with plastic insulation in aluminum sheath... 15
plastic and rubber insulation:
single-core. ..... . ,.,......, 10
stranded, . .. . . . -, . . , . 7.5
Excessively tight bends can damage the insulation and sheaths of the cables. In paper insulation, paper tapes are displaced and torn. Plastic and rubber insulation breaks when sharply bent, and wrinkles or cracks appear on the shells.
The maximum allowable level difference between: the highest and lowest points of the location of cables with voltage up to 1 kV with paper insulation and with their pro-; masonry on vertical and inclined sections should be no more than 25 m. The difference in levels for cables with plastic and rubber insulation is not limited.
The limitation of the level difference between the highest and lowest points of the cables is associated with the movement of the impregnating composition. It happens barely: in a blowing way. The cable cores are heated by electric current and there is a volumetric expansion of all materials from which the cable is made. The impregnating composition has the highest coefficient of volumetric expansion of the materials included in the cable construction. Therefore, it is filtered through the cable paper, penetrates the metal sheath and creates an overpressure in the cable, which leads to the expansion of the sheath and an increase in its volume. In a cable laid vertically or obliquely, under the action of gravity, the impregnating composition drains (between the wires of the cores, along the surface of single-wire cores, in the gaps between the paper insulation and the sheath), as a result of which an excess amount of the impregnating composition accumulates in the lower part of the cable, and in voids are formed in the upper part, filled with volatile substances and gases. The greater the level difference between the highest and lowest points of the cable location, the higher the hydrostatic pressure of the impregnating composition column on the metal sheath of the cable and the termination or termination. Under significant pressure, deformation of the shell can occur, the tightness of the end seal can be broken and, as a result, the impregnating composition can leak out. The presence of air and vacuum inclusions in cable insulation is accompanied by a sharp deterioration in electrical strength. When using cables with aluminum sheaths, which have greater mechanical strength than lead sheaths, the highest allowable level difference increases.
For cables with depleted-impregnated insulation, the largest allowable difference in levels increases to 100 m with lead sheaths and is not limited with aluminum sheaths.
The indicated level difference is not limited for cables with paper insulation impregnated with a non-flowing compound.
Cables are laid, as a rule, at a positive ambient temperature. Unwinding, carrying and laying cables at low temperatures is carried out after preheating.

The need for the use and volume of automatic stationary means for detecting and extinguishing fires in cable structures should be determined on the basis of departmental documents approved in the prescribed manner.

Fire hydrants must be installed in the immediate vicinity of the entrance, hatches and ventilation shafts (within a radius of no more than 25 m). For flyovers and galleries, fire hydrants should be located in such a way that the distance from any point on the axis of the flyover and gallery route to the nearest hydrant does not exceed 100 m.

2.3.123

In cable structures, the laying of control cables and power cables with a cross section of 25 mm or more, with the exception of unarmored cables with a lead sheath, should be carried out along cable structures (consoles).

Control unarmoured cables, unarmoured power cables with a lead sheath and unarmoured power cables of all designs with a cross section of 16 mm or less should be laid along trays or partitions (solid or non-solid).

It is allowed to lay cables along the bottom of the channel at a depth of not more than 0.9 m; in this case, the distance between a group of power cables above 1 kV and a group of control cables must be at least 100 mm, or these groups of cables must be separated by a fireproof partition with a fire resistance of at least 0.25 hours.

The distances between the individual cables are given in table. 2.3.1.

Backfilling of power cables laid in channels with sand is prohibited (for an exception, see 7.3.110).

In cable structures, the height, width of passages and the distance between structures and cables must be at least those given in Table. 2.3.1. Compared with the distances given in the table, local narrowing of the passages up to 800 mm or a decrease in height up to 1.5 m over a length of 1.0 m is allowed with a corresponding decrease in the vertical distance between the cables with one-sided and two-sided arrangement of structures.

Table 2.3.1. Minimum distance for cable installations

	The smallest dimensions, mm, when laying
Distance	in tunnels, galleries, cable floors and overpasses	in cable ducts and double floors
clear height		Not limited, but not more than 1200 mm
Horizontally in the light between structures with their two-sided arrangement (passage width)		300 at a depth of up to 0.6 m; 450 at a depth of more than 0.6 to 0.9 m; 600 at a depth of more than 0.9 m
Horizontally clear from the structure to the wall with one-sided arrangement (passage width)
Vertical between horizontal structures *:
for power cables with voltage:


110 kV and above
for control and communication cables, as well as power cables with a cross section of up to 3x25 mm and a voltage of up to 1 kV
Between supporting structures (cantilevers) along the length of the structure
Vertically and horizontally in the clear between single power cables up to 35 kV***	Not less than cable diameter
Horizontally between control cables and communication cables ***	Not standardized
Horizontally in the light between cables with a voltage of 110 kV and above		Not less than cable diameter
____________________ * The useful length of the console should not exceed 500 mm on straight sections of the track. When cables are arranged in a 250 mm triangle. * Including for cables laid in cable shafts.

2.3.124

Laying of control cables is allowed in bundles on trays and in multilayers in metal boxes, subject to the following conditions:

1. The outer diameter of the bundle of cables should be no more than 100 mm.

2. The height of the layers in one box should not exceed 150 mm.

3. Only cables with the same type of sheaths should be laid in bundles and multilayers.

4. Fastening cables in bundles, multilayered in boxes, bundles of cables to trays should be carried out in such a way that deformation of the cable sheaths under the action of its own weight and fastening devices is prevented.

5. For the purpose of fire safety, fire protection belts should be installed inside the ducts: in vertical sections - at a distance of no more than 20 m, as well as when passing through the ceiling; on horizontal sections - when passing through partitions.

6. In each direction of the cable route, a capacity margin of at least 15% of the total capacity of the boxes should be provided.

Laying of power cables in bundles and multilayer is not allowed.

2.3.125

*. In places saturated with underground utilities, it is allowed to perform semi-through tunnels with a height reduced in comparison with that provided for in Table. 2.3.1, but not less than 1.5 m, subject to the following requirements: the voltage of the cable lines must not exceed 10 kV; the length of the tunnel should be no more than 100 m; other distances must correspond to those given in table. 2.3.1; at the ends of the tunnel there should be exits or hatches.

___________________

* Agreed with the Central Committee of the trade union of workers of power plants and the electrical industry.

2.3.126

Oil-filled low-pressure cables must be fastened to metal structures in such a way that the possibility of the formation of closed magnetic circuits around the cables is excluded; the distance between the attachment points should be no more than 1 m.

Steel pipelines of high-pressure oil-filled cable lines can be laid on supports or suspended on hangers; the distance between supports or hangers is determined by the line project. In addition, pipelines must be fixed on fixed supports to prevent thermal deformations in pipelines under operating conditions.

The loads taken by the supports from the weight of the pipeline should not lead to any movement or destruction of the foundations of the supports. The number of these supports and their locations are determined by the project.

Mechanical supports and fastenings of branching devices on high-pressure lines should prevent the branching pipes from swinging, the formation of closed magnetic circuits around them, and insulating gaskets should be provided at the points of fastenings or touches of the supports.

2.3.127

The height of cable wells must be at least 1.8 m; chamber height is not standardized. Cable wells for connecting, locking and semi-locking couplings must have dimensions that ensure the installation of couplings without breaking.

Shore wells at underwater crossings should be sized to accommodate backup cables and feeders.

In the floor of the well, a pit should be arranged to collect groundwater and storm water; a drainage device shall also be provided in accordance with the requirements given in 2.3.114.

Cable wells must be equipped with metal ladders.

In cable wells, cables and couplings must be laid on structures, trays or partitions.

2.3.128

The hatches of cable wells and tunnels must have a diameter of at least 650 mm and be closed with double metal covers, of which the lower one must have a locking device that can be opened from the side of the tunnel without a key. Covers must be equipped with tools for their removal. Indoors, the use of a second cover is not required.

2.3.129

On the couplings of power cables with a voltage of 6-35 kV in tunnels, cable floors and channels, special protective covers must be installed to localize fires and explosions that may occur during electrical breakdowns in the couplings.

2.3.130

Terminations on high-pressure oil-filled cable lines should be located in rooms with a positive air temperature or be equipped with automatic heating when the ambient temperature drops below +5°C.

2.3.131

When laying oil-filled cables in the galleries, it is necessary to provide heating of the galleries in accordance with the specifications for oil-filled cables.

The premises of the oil-feeding units of the high-pressure lines must have natural ventilation. Underground feeding points are allowed to be combined with cable wells; in this case, the wells must be equipped with drainage devices in accordance with 2.3.127.

2.3.132

Cable structures, with the exception of overpasses, wells for couplings, channels and chambers, must be provided with natural or artificial ventilation, and the ventilation of each compartment must be independent.

The calculation of the ventilation of cable structures is determined based on the temperature difference between the incoming and outgoing air of no more than 10 ° C. In this case, the formation of hot air bags in the narrowing of tunnels, turns, detours, etc. must be prevented.

Ventilation devices must be equipped with dampers (gates) to stop air access in the event of a fire, as well as to prevent the tunnel from freezing in winter. The design of ventilation devices should ensure the possibility of using automation to stop air access to buildings.

When laying cables indoors, overheating of the cables must be prevented due to the increased ambient temperature and the effects of process equipment.

Cable structures, with the exception of wells for couplings, channels, chambers and open overpasses, must be equipped with electric lighting and a network for powering portable lamps and tools. At thermal power plants, the network for powering the tool may not be performed.

2.3.133

Cable laying in collectors, technological galleries and technological overpasses is carried out in accordance with the requirements of SNiP Gosstroy of Russia.

The smallest clear distances from cable racks and galleries to buildings and structures should correspond to those given in Table. 2.3.2.

The intersection of cable racks and galleries with overhead power lines, internal railways and roads, fire lanes, cable cars, overhead communication and radio lines and pipelines is recommended to be carried out at an angle of at least 30 °.

Table 2.3.2. The smallest distance from cable racks and galleries to buildings and structures

construction	Normalized distance	Smallest dimensions, m
When parallel following, horizontally
Buildings and structures with blank walls	From the construction of the overpass and gallery to the wall of the building and structure	Not standardized
Buildings and structures with walls with openings
In-plant non-electric railroad	From the design of the overpass and gallery to the dimension of the approach of buildings	1 m for galleries and overpasses; 3 m for impassable flyovers
Intra-plant road and fire lanes	From flyover and gallery construction to curbstone, outer edge or road ditch sole
cable car	From the design of the overpass and gallery to the gauge of the rolling stock
Above ground pipeline

When crossing, vertically
Intra-factory non-electrified bathroom railroad	From the bottom mark of the overpass and gallery to the rail head
Intra-factory electrified railway	From the bottom mark of the overpass and gallery:
	up to the rail head
	to the highest wire or carrier cable of the contact network
Internal factory road (fire road)	From the bottom mark of the overpass and gallery to the roadbed (fire passage)
Above ground pipeline	From the construction of the overpass and gallery to the nearest parts of the pipeline
Overhead power line	From the design of the overpass and gallery to the wires
Air communication and radio communication line	Also	1,5

The location of overpasses and galleries in hazardous areas - see Ch. 7.3, the location of overpasses and galleries in fire hazardous areas - see Ch. 7.4.

With parallel passage of flyovers and galleries with overhead communication and radio lines, the smallest distances between cables and wires of a communication and radio line are determined based on the calculation of the effect of cable lines on communication and radio lines. Communication and radio communication wires can be located under and above flyovers and galleries.

The smallest height of the cable overpass and gallery in the impassable part of the territory of an industrial enterprise should be taken into account the possibility of laying the lower row of cables at a level of at least 2.5 m from the planning ground level.

How power cables are arranged

Power cables consist of the following basic elements: conductive cores, insulation, sheaths and protective covers. In addition to the main elements, the cable design may include screens, protective earth conductors and fillers.

Power cables distinguish: according to the type of metal of the conductive conductors - cables with aluminum and copper conductors, according to the type of materials with which the current-carrying conductors are insulated, cables with paper, plastic and rubber insulation, according to the type of protection of the insulation of the cable cores from the influence of the external environment - cables in metal, plastic and rubber sheath, according to the method of protection against mechanical damage - armored and unarmored, according to the number of cores - one-, two-, three-, four- and five-core.

Each cable design has its own designation and brand. The brand of the cable is made up of the initial letters of the words describing the design of the cable.

Rice. 1. Cross-sections of power cables: a - two-core cables with round and segmented cores, b - three-core cables with belt insulation and separate sheaths, c - four-core cables with a zero core of round, sector and triangular shape, 1 - conductive core, 2 - zero core , 3 - core insulation, 4 - screen on conductive core, 5 - belt insulation, 6 - filler, 7 - screen on core insulation, 8 - sheath, 9 - armored cover, 10 - outer protective cover

Structural elements of power cables and their purpose.

Conductive conductors are conductors of electric current. Power cables have main and neutral conductors. The main conductors are used to transmit electrical energy, and the zero conductors are used to pass the phase current difference at and uneven load.

The current-carrying cores of power cables are made of aluminum and copper, single-wire and multi-wire. The shape of the core is made round, sector or segmented (see Fig. 1).

Aluminum conductors of cables up to 35 mm2 inclusive are made single-wire, 50-240 mm2 - single-wire or stranded, 300-800 mm2 - stranded.

Copper conductors up to 16 mm2 inclusive are made single-wire, 25 - 95 mm2 - single-wire or stranded, 120 - 800 mm2 - stranded.

The neutral conductor or the protective earth conductor, as a rule, has a section that is reduced compared to the main conductors. It can be round, sector or triangular in shape and is located in the center of the cable or between its main cores (see Fig. 1).

The protective earth conductor is used to connect non-live metal parts of the electrical installation to the protective earth loop.

Insulation provides the necessary electrical strength of the current-carrying conductors in relation to each other and to the grounded sheath (ground). Paper, rubber and plastic (polyvinyl chloride and polyethylene) insulation is used.

Insulation applied to a cable core is called core insulation, and applied over insulated twisted or parallel conductors of a multi-core cable is called belt insulation.

It is impregnated with viscous impregnating compounds (oil rosin or electrical insulating synthetic).

The disadvantage of cables with a viscous impregnation composition is the extremely limited possibility of laying them along inclined routes, namely, the height difference between their end terminations should not exceed: for cables with viscous impregnation up to 3 kV armored and unarmored in an aluminum sheath - 25 m sheath - 20 m, armored in lead sheath - 25 m, for cables with viscous impregnation 6 kV armored and unarmored in lead sheath - 15 m, in aluminum - 20 m, for cables with viscous impregnation 10 kV armored and unarmored in lead and aluminum shell - 15 m.

Cables with a viscous impregnating composition, the free part of which is removed, are called cables with lean impregnated insulation. They are used when laying on vertical and inclined routes without limiting the level difference, if these are unarmoured and armored cables in an aluminum sheath for voltages up to 3 kV, and with a level difference of up to 100 m - for any other cables with depleted impregnated insulation.

For laying along vertical and steep routes without limiting the level difference, cables are made with paper insulation impregnated with a special composition based on ceresin or polyisobutylene. This composition has an increased viscosity, as a result of which, when a cable laid vertically or along a steeply inclined route is heated, it does not flow down. Therefore, cables with such insulation can be laid to any height, just like cables with plastic and rubber insulation.

Rubber insulation is made from a continuous layer of rubber or from rubber bands, followed by vulcanization. Power cables with rubber insulation are used in AC networks up to 1 kV and DC up to 10 kV.

They have isolation from polyvinylchloride plastic compound in the form of a continuous layer or from compositions of polyethylene. Cables with self-extinguishing (non-combustible) and vulcanized polyethylene insulation are also used.

Screens are used to protect external circuits from the influence of electromagnetic fields of currents passing through the cable, and to ensure the symmetry of the electric field around the cable cores. Screens are made of semi-conductive paper and aluminum or copper foil.

Fillers are necessary to eliminate the free gaps between the structural elements of the cable in order to seal, give the required shape and mechanical stability of the cable structure. As fillers, bundles of paper tapes or cable yarn, plastic or rubber threads are used.

Power cable sheaths. Aluminum, lead, corrugated steel, plastic and rubber non-combustible (nayrite) cable sheaths protect the internal elements of the cable from destruction by moisture, acids, gases, etc.

The aluminum sheath of power cables for voltages up to 1 kV can be used as the fourth (zero) core in four-wire AC networks with a solidly grounded neutral, with the exception of installations with an explosive atmosphere and installations in which the current in the neutral wire under normal conditions is more than 75% of the current in phase core.

Protective covers for power cables. Since cable sheaths can be damaged and even destroyed by chemical and mechanical influences, they are covered with protective covers.

Protective covers protect cable sheaths from external influences (corrosion, mechanical damage). These include the cushion, armor cover, and outer cover. Depending on the design of the cable, one, two or three protective covers are used.

The cushion is applied to the screen or shell to protect it from corrosion and damage by armor tapes or wires. The pillow is made from layers of impregnated cable yarn, PVC, polyamide and other equivalent tapes, crepe paper, bituminous composition or bitumen.

To protect against mechanical damage, the cable sheaths are wrapped depending on the operating conditions. steel belt or wire armor. Wire armor is made of round or flat wires.

Armor made of flat steel tapes protects cables only from mechanical damage. Armor made of steel wires, in addition to this, also perceives tensile forces. These forces occur in cables when cables are laid vertically at great heights or along steeply inclined routes.

To protect the armor of cables from corrosion, it is covered with an outer cover made of a layer of cable or glass yarn impregnated with a bitumen composition, and in some designs, a pressed polyvinyl chloride or polyethylene hose is applied over the layers of yarn and bitumen.

In mines, explosive and fire hazardous rooms, it is not allowed to use armored cables of a conventional design due to the presence of a "cushion" containing combustible bitumen between the sheath and armor of the cable. In these cases, cables with a non-combustible "cushion" and an outer cover made from glass yarn from glass staple must be used.

Publication date: 09/13/2018

What is cable structures?

Cable structures are load-bearing structures, these include: cable boxes, cable trays, sections, cable racks, consoles, scarves, tees, adapter brackets and other elements designed for laying power and control cables in the open air, inside buildings and energy facilities facilities, including nuclear power plants in the Russian Federation.

What are cable structures made of?

Cable structures are made of bent profiles of increased rigidity. Perforation provides not only ease of installation of structures and fastening of cables, but also their ventilation when heated, as well as rapid detection and elimination of fires on cable routes (including the use of automatic fire extinguishing). Perforation makes it possible to decontaminate cable routes at nuclear power plants and wash off dust from cables in conditions of particularly dusty industries (pulverized coal production, woodworking plants, etc.).

Benefits of using

The use of bent profiles of increased rigidity allows, with a low metal consumption, to provide a large load capacity and increased structural strength. Thanks to the zinc coating, these structures can be used in both cold and maritime tropical climates.

A wide range of cable structure elements is provided, which allows:

install cable routes of any configuration without welding;
separate cable systems for fire extinguishing, communications, etc. from the main cable flows in compliance with all norms and rules for the joint laying of cables for various purposes on the same cable structures.

Type of climatic modification - U2. Т1 in accordance with GOST 15150. Nominal values of environmental climatic factors in accordance with GOST 15150. Other types of climatic modification are allowed upon agreement with the customer.

In industrial premises and cable structures, various designs are used for laying cables and wires. The installation of structures at the facility is a significant amount of electrical work, so the structures must meet a high degree of prefabrication and have a small mass. Cable structures are produced in normal and chemically resistant versions (galvanized or painted with chemically resistant varnishes).

Prefabricated cable structures (Fig. 30) are designed for laying electrical cables, as well as installing trays and boxes on them. They are installed along the walls of rooms, canals, tunnels, wells and other building structures. The distance between the cable structures on the horizontal sections of the route is 0.8-1 m, on the vertical sections - 2 m.

The structure of the cable structure includes racks, shelves, brackets and a key. Racks are made with a height of H 400-1800 mm (Fig. 30, a) from sheet steel with perforation, which has a pitch of 50 mm, which allows you to install shelves with distances between them of 100, 150 mm, etc. Cable construction does not require welding of shelves to the racks. The shelf is inserted into the rack and mechanically secured with a key. The reliability of the mechanical engagement of the shelf with the rack provides the necessary electrical contact for grounding the shelves. Racks are attached to building bases with brackets by shooting or welding to embedded parts.

Rice. 30. Prefabricated cable structures:
a - cable rack, b - shelf, c - bracket for attaching the cable rack, d - key for attaching the shelf to the rack

To obtain a cable structure of the required height, the racks can be vertically joined together in any combination. The shelves are made with a length (overhang) of 160-450 mm (Fig. 30, b), which allows you to complete the rack with shelves of different lengths.

For laying single cables, cable structures are used, consisting of perforated channels and embedded hangers (Fig. 31), which are inserted into the channel perforation hole with the narrow side of the shank and rotated by 90 °. Hangers are produced in three standard sizes for cables with an outer diameter of 20, 35 and 50 mm.

Rice. 31. Cable structures for single cables:
1 - perforated channel, 2 - embedded suspension

For fastening cables to various bases, single-blade and two-blade brackets are used (Fig. 32).

Rice. 32. Clips for cables:
a, b - single-arm and two-arm for fastening with screws and bolts, c - two-arm for shooting.

Trays are used for laying power and control cables and wires with voltage up to 1000 V and are made of perforated bent metal sheet. The width of the tray is 50, 100, 200 and 400 mm, the length is 2 m. The range of trays includes elements ready for assembly that provide the creation of a route with the necessary turns and branches in the horizontal and vertical planes (Fig. 33).

Rice. 33. Trays:
1, 2 - straight lines with a width of 50, 100 or 200, 400 mm, 3 - angled, 4. 5 - transitional and hinged connectors, 6 - clamps, 7 - hangers

The trays are connected with bolts, which ensures a reliable electrical circuit, which is necessary for the grounding network. Mount trays on brackets, hangers and prefabricated cable structures. Trays mounted on supporting structures are fixed in such a way that the possibility of slipping, overturning and falling them is excluded.

When trays intersect with other communications, the trays are laid indented from the walls, if this is not possible, bypasses are performed.

Boxes have a purpose similar to trays.

For straight sections of the route, a straight box is used, for branching into four directions - a cruciform box, for changing the direction of the route in the horizontal and vertical planes - an angular one, for entering electrical devices - a connecting one. In addition, the box set includes: an end cap for closing the end of the box and a clamp for fixing wires and cables. The boxes are made single-channel with a length of 2 and 3 m and are calculated for uniformly distributed loads (the distance between the attachment points is 3 m).

The boxes are designed for laying wires and cables in them with a bending radius of up to 50 mm.

Control questions

List the advantages and disadvantages of tunnels and channels.
What is the design and purpose of collectors?
List the advantages and disadvantages of a block sewer.
Why have they become less likely to use cable laying in trenches?
Why is the laying of cables on overpasses and galleries so widespread?
What is the purpose of prefabricated cable structures?