Laying cables on the structures of buildings and structures. Power cable design What is cable construction used for?

Prefabricated cable structures (hereinafter referred to as products) are designed for laying cables, as well as for installing trays and boxes on them.
View climatic design products UT1,5 and U3 (operation in temperate, as well as in dry and humid tropical climates on outdoors and in rooms with high air temperature, as well as with high humidity) according to GOST 15150-69.
The product includes ready-to-install elements:

• Racks - for installing shelves on them.
• Shelves - for laying cables on them and installing trays and boxes on them.
• Bracket - for attaching racks to building structures.

Cable rack

Racks are attached to building structures by welding or shooting using the K-1157 bracket. Cable racks (Table 33, Fig. 43) are used to install shelves K-1160 - K-1164.

Designation	Length, mm.	Weight, kg
K-1150 U3	400	0,75
K-1150 Ts UT1.5
K-1151 U3	600	1,12
K-1151 Ts UT1.5
K-1152 U3	800	1,49
K-1152 Ts UT1.5
K-1153 U3	1200	2,22
K-1153 Ts UT1.5
K-1154 U3	1800	3,36
K-1154 Ts UT1.5
K-1155 U3	2200	4,10
K-1155 Ts UT1.5

Cable shelf

Shelves are designed for laying wires, cables, trays and boxes on them.
To fasten the shelf to the rack, the shelf shank is inserted into the hole in the rack, after which its tongue is turned by 90 ° with a key. This provides an electrical connection between the shelf and the rack.

Designation	Height, mm.	Length, mm.	Weight, kg	Part number
K-1160 U3	61	175	0,22
K-1160 Ts UT1.5		175
K-1161 U3		265	0,34
K-1161 Ts UT1.5		265
K-1162 U3		355	0,52
K-1162 Ts UT1.5		355
K-1163 U3	71	450	0,73
K-1163 Ts UT1.5		450
K-1164 U3		630	1,02
K-1164 Ts UT1.5		630

Working load on shelves, no more than:
K-1160 - 175N
K-1161 - 275N
K-1162 - 400N
K-1163 - 500N
K-1164 - 600N

brace

Bracket K-1157 is designed for fastening cable racks by welding to embedded parts or by shooting.

A type	Weight, kg
K-1157 U3	0,140
K-1157ts UT1.5

Mounting profiles and strips

Perforated steel mounting bent profiles K-225, K-235, K-236, K-237, K-239, K-240, K-241 (Fig. 51-53) and strips K-106, K-107, K -202 (Fig. 54) are designed for the manufacture of various designs with electric installation work Oh. The length of profiles and mounting strips is 2m. Performed according to TU 36-1434-82. The name, types, main dimensions and weight are given in the table.

A type	Name	Dimensions, mm							Number of holes	Weight, kg
		H	B	h	L	L1	t	S
K-235 U2; UT1.5	Channel	60	30	-	45	13	60	2,5	99	3,3
K-225 U2; UT1.5	Channel	80	40	-	55	17	70	2,5	28	5,5
K-240 U2; UT1.5	Channel	60	32	-	45	13	60	2,5	33	4,2
K-236 U2; UT1.5	corner	56	40	-	45	11	60	4	66	4,6
K-237 U2; UT1.5	corner	50	36	-	36	11	50	3	80	3,1
K-239 U2; UT1.5	Profile Z	97	40	60	45	13	60	3	66	5,2
K-241 U2;UT1.5	Profile Z	62	40	32	32	9	40	2	100	2,6
K-106 U2; UT1.5	Strip	40	-	-	36	9	50	4	40	2,06
K-107 U2; UT1.5	Strip	40	-	-	36	9	50	3	40	1,6
K-202 U2; UT1.5	Strip	20	-	-	25	6,6	40	3	50	0,94

Systems of cable structures designed for laying cables and installing other electrical equipment on them electrical installations and/or communication networks, can also be used to separate cables and form them into streams (groups). The system of cable structures includes mounting trays LM (cable trays), load-bearing trays NL (cable ladders), cable racks and supports (cantilever brackets), brackets and connectors.

Each type of special structure for laying cables is characterized by the maximum number of power cables that can be laid in it. Trench - 6 cables, channel -24, block - 20, tunnel - 72, flyover - 24, gallery - 56.

There is rarely a preference for any one type of cabling. Usually, a mixed laying is used, when, depending on the specific conditions, a combined execution of various laying methods is expedient. cable lines.

Cable lines of industrial enterprises can be divided into intra-shop and non-shop. Intra-workshop cable networks include laying cables openly on structures, in trays, boxes, channels, tunnels and pipes.

In rooms, hidden laying of wires and cables in steel pipes is gradually being replaced by open laying. Open laying of cables almost completely eliminates the dependence of the installation work on laying cables on the readiness of the construction part of the structure. Exposed cable runs allow zero cycle completion construction works without waiting for electrical installation work, which is impossible with hidden gaskets. Open cable runs are visible, accessible, convenient for inspection and replacement of cables, and are flexible when changing routes during the reconstruction of electrical installations.

When laying cables openly, fire safety measures should be observed, justify the choice of brands of cables and sheaths, choose the right cable for heating, control the quality of connections and the order of cable laying, separate the zones of mass cable laying from equipment. When laying open cables in electrical and industrial premises one should strive to combine routes, combine cables for various purposes (power, lighting, control cables) into common flows, laying them on common structures, trays or boxes.

Laying cable lines on walls and cable structures

In industrial premises and cable structures, they are used various designs 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.

a - cable rack, b - shelf, c - bracket for attaching the cable rack, d - key for attaching the shelf to the rack

Figure 3. - Prefabricated cable structures

Prefabricated cable structures (Figure 3) are designed for laying electrical cables, as well as the installation of trays and boxes on them. They are installed along the walls of rooms, canals, tunnels, wells and other building structures. The distance between cable structures on horizontal sections of the route is 0.8 - 1 m, on 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. NUMBERING, 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. The cable structure does not require welding shelves to 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.

To obtain a cable structure of the required height, the racks can be vertically joined together in any combination. The shelves are made in length (overhang l) 160 - 450 mm (Figure 3, b), which allows you to complete the rack with shelves of different lengths.

1 - perforated channel, 2 - embedded suspension

Figure 4 - Cable structures for single cables

For laying single cables, cable structures are used, consisting of perforated channels and embedded hangers (Figure 4), 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.

For fastening cables to various bases, single-blade and two-blade brackets are used (Figure 5).

a, b - single-arm and two-arm for fastening with screws or bolts, c - two-arm for shooting

Rice. 5 - Clamps for cables

Trays are used for laying power and control cables and wires up to 1000 V and are made of perforated bent sheet metal. 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 ensure the creation of a route with the necessary turns and branches in the horizontal and vertical planes (Figure 6).

1, 2 - straight lines with a width of 50, 100 or 200, 400 mm, 3 - angular. 4, 5 - transition and swivel connectors, 6 - clamps, 7 - hangers

Figure 6 - Trays

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.

In cable tunnels, channels, shafts and industrial premises, cables are laid along cable structures and in boxes. Cable structures, ducts and fasteners necessary for laying and fastening cables are produced by industrial enterprises of Glavelektromontazh.

Prefabricated cable structures consist of racks with special holes in which consoles are installed, made with and without perforation. Prefabricated cable structures are intended for direct laying of armored cables over them. When laying unarmored cables on prefabricated cable structures, solid fireproof partitions made of asbestos-cement boards under metal cable trays should be laid.

Cable ducts are produced in the KP and KKB series. Boxes of the KP series (Fig. 5) are used for multilayer laying of control cables under and above service platforms in the main building and auxiliary facilities of power plants, as well as in galleries along overpasses and in cable floors. The set of boxes includes straight, angled and tee sections, which makes it possible to assemble any cable route from them. The gearbox box section consists of a body, a cover and fasteners.

Boxes block series KKB (Fig. 5) are used for joint laying of power and control cables both inside the main building and auxiliary structures, and across the territory of power plants and outdoor switchgear. The boxes have an angle steel frame and a steel sheet lining. Cable consoles are installed inside the boxes. For the possibility of completing the cable route, elements of straight and corner boxes are produced.

Installation of cable structures should be started after completion plastering works, whitewashing and painting walls and building structures along which the cable route passes.

To fasten cable structures along the entire length of the cable route, 50x5 mm guide strips are laid from strip steel, two in number for tunnels and channels 900 and 1200 mm high and one for channels less than 900 mm high. These strips are also used as grounding lines and therefore must be securely welded along the entire length and connected along the route in two places to a common ground loop. The guide strips are welded to the embedded parts or attached to the building base with dowels fired with a mounting gun.

Fig 5. Left KP series box: 1-pin; 2 - cover; 3 - clamping bar; 4 - gasket; 5 - box body; 6 - cables or wires; 7 - cable structure bracket: 8 - insulating tube; 9-nut: 10-pillar On right- Cable boxes of the KKB series: a - box assembly; b - self-supporting span of the box; 1.2-corner box for horizontal rotation by 225 ° type KKB-UGN; 3 - direct type KKB-P; 4. 5 - angular type KKB-UN; 6 - direct type KKB-PO

Prefabricated cable structures are welded to the guide strips vertically and at the same height so that the corresponding shelves of all structures are on the same line. The distance between cable structures is maintained within 800-1000 mm. In places where the cable route turns, the distance between the structures is chosen in such a way that the permissible bending radius of the cables is maintained.

Metal trays are installed over cable structures when unarmored cables are laid through them. Trays are attached to structures with bolts or wedges or welded by electric welding. The connection of the trays is also carried out by bolts or welding. On the vertical sections of the cable route, the distance between the supporting structures should be no more than 2 m for cables of all brands, except for unarmored cables with rubber insulation of small sections, for which this distance should be no more than 0.7 m.

KP series cable ducts are installed on cable shelves, brackets or suspended on cables. The connection of the duct sections and the continuous earthing circuit are carried out by means of bolts or by welding. Boxes of the KKB series are self-supporting and can be attached to the supports assembled in blocks with a distance between the supports from 3 to 12 m. To increase fire safety, fire barriers are provided in the boxes KP and KKB. The boxes must be grounded in each room at least in two places.

Staples, buckles and other parts are used to fasten cables to structures.

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, cores protective earth and placeholders.

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 unarmoured, by 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.

Conductors are conductors 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-laid cores 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 networks alternating current up to 1 kV and direct current 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 symmetry 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 necessary 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 environment and installations in which the current in the neutral wire is at normal conditions is more than 75% of the current in the phase conductor.

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 on great height or on steep slopes.

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 should be used.

Inside cable structures (premises), cables are laid on steel structures of various designs. A cable structure is a room specially designed for placing cables, cable and other equipment in it, designed to ensure normal operation.

General principles for laying cable lines

Cable structures include cable tunnels, channels, boxes, blocks, shafts, floors, double floors, cable racks, galleries, chambers, feed points.

Cable structures must be separated from other rooms and neighboring cable structures by fireproof partitions and ceilings.

With the same partitions, extended tunnels should be divided into compartments no longer than 150 m when laying power and control cables and no more than 100 m with oil-filled cables. In cable structures, measures must be taken to prevent the ingress of process water and oils into them, and soil and storm water must also be drained.

Inside cable structures, cables are laid on steel structures of various designs. Cables of large cross sections (aluminum with a cross section of 25 mm2 or more, copper section 16 mm2 and more) are laid directly on the structures.

Power cables of smaller cross sections and control cables are laid in trays (welded or perforated) or in boxes that are mounted on cable structures or on walls. The lining in the trays is more reliable and has a better appearance than open gasket on structures.

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

Ventilation devices equipped with dampers to stop air access in case of fire, as well as to prevent the tunnel from freezing in winter.

When laying cables indoors, overheating of the cables must be prevented by increasing the ambient temperature and the influence technological equipment(it is not allowed to lay cables near the oil pipeline, above and below oil pipelines and pipelines with flammable liquid). In the floor and interfloor ceilings, cables are laid in channels or pipes. Do not lay cables in ventilation ducts and also open through the stairwells.

Cable crossings of passages must be carried out at a height of at least 1.8 m from the floor.

Rules for laying cables in cable tunnels

Cable tunnels (and collectors, in which pipelines are also laid), are recommended to be built in cities and enterprises with dense development of the territory or when the territory is highly saturated with underground utilities, as well as in the territories of large metallurgical, machine-building and other enterprises. Cable tunnels are constructed, as a rule, with the number of cables being laid from 20. Tunnels usually serve as trunk tunnels.

Rectangular cable tunnels are designed for two-sided and one-sided laying of cables and come in pass-through and semi-passage versions.

With a large number of cables, tunnels and rectangular collectors can be three-walled (double). In table. 5.6 shows the main dimensions of rectangular tunnels.

The use of semi-passage tunnels is allowed in places where underground communications prevent the passage tunnel from being completed; at the same time, a semi-through tunnel is accepted with a length of not more than 15 m and for cables with a voltage of not more than 10 kV.

The width of passages in cable tunnels and collectors must be at least 1 m, however, it is allowed to reduce the width of passages to 800 mm in sections no longer than 500 mm.

Long cable tunnels and collectors are divided along the length by fire-resistant partitions into compartments no longer than 150 m long with doors installed in them. The laying of cables in collectors and tunnels is calculated taking into account the possibility of additional laying of cables in the amount of at least 15%.

With double-sided arrangement of cable structures, control cables should be placed, if possible, on the opposite side from the power cables. With one-sided arrangement of structures, control cables should be placed under power cables and separated by a horizontal partition.

Power cables up to 1 kV should be laid under the cables voltage above 1 kV and separate them with a horizontal partition. It is recommended to lay different groups of cables (working and reserve voltages above 1 kV) on different shelves with their separation by horizontal fireproof partitions. As partitions, it is recommended to use asbestos-cement pressed unpainted slabs with a thickness of not less than 8 mm.

The use of unarmored cables with a polyethylene sheath in cable tunnels is prohibited according to fire safety conditions.

Cables laid horizontally along the structures are rigidly fixed at the end points, at the turns of the route, on both sides of the cable bend, at the connecting and end terminations. Cables laid vertically along structures and walls are fixed on each cable structure. In places of fastening between unarmored cables with a lead or aluminum sheath, metal supporting structures and a metal bracket, gaskets made of elastic material (rubber sheet, polyvinyl chloride sheet) with a thickness of at least 2 mm must be laid, protecting the sheath from mechanical damage. Unarmored cables with a plastic sheath can be fastened with brackets (clamps) without gaskets.

The metal armor of cables laid in tunnels must have an anti-corrosion coating.

Rules for laying cable in channels

Cable laying in cable channels are widely used. Cable channels are made standard from prefabricated reinforced concrete elements or from monolithic reinforced concrete (Fig. 5.7). In industrial premises, the channels are blocked with slabs at the floor level.

When passing outside buildings in unprotected areas, the channels are laid underground at a depth of at least 300 mm, depending on the loads that may occur on the route.

If the territory is protected, then semi-underground channels with natural or artificial ventilation are used. But such channels should not interfere with transport communications and should not be combined with the general layout of the territory of the enterprise, since the level of overlap of such channels rises above the planning mark by 50 ... 250 mm.

Cables in the channels are laid on structures of various designs; laying along the bottom of the channel is also possible. The number of cables in the channel can be different and depends on the diameters of the cables and the brand of the typical channel; up to 50 ... 60 power cables can be placed in channels of maximum dimensions. Gaskets if required a large number cables, it is possible to use double or three-walled channels, but this complicates the implementation of branches to individual consumers.

The method of laying cables in the channels allows for inspection and repair of cable lines during operation, as well as laying a new or replacing an existing cable without excavation.

When laying cables in channels, their reliable protection from mechanical damage.

In table. 5.7 shows the main dimensions of unified cable channels (designations B, B, H in Fig. 5.7).

The main straight tray channels, ceilings to them, as well as the main elements of prefabricated channels have a length of 3 m. 3×240 mm2, with cable bending radius R = 25d.

In areas where molten metal, high temperature liquids or substances that destroy the cable sheaths can be spilled, the construction of cable channels is not allowed.

Cable ducts outside buildings should be covered with earth over removable slabs with a layer thickness of 300 mm or more. In fenced areas accessible only to service personnel, for example, at substations, backfilling of cable channels over removable plates is prohibited.

Backfilling of power cables laid in channels is prohibited. The location of cables on structures, depending on the size of the channels, can be:

• on one wall of the channel on suspensions;
• on one wall of the channel on the shelves;
• on both walls on suspensions;
• on one wall of the channel on hangers, on the other wall on shelves;
• on both walls of the channel on the shelves;
• at the bottom of the channel with a depth of not more than 0.9 m.

Cable channels should be calculated taking into account the possibility of additional laying of cables at least 10% of those laid. The horizontal clear distance between the structures with their two-sided arrangement (passage width) must be at least 300 mm for channels up to 600 mm deep and at least 400 mm for channels with a depth of 900 and 1,200 mm.

Wiring are integral part electrical power and lighting networks of alternating and direct current with voltage up to 1 kV. Depending on the designs of conductors, the characteristics of the premises and environment conductors lay different ways: open on insulating supports or directly on building foundations and structures, in pipelines, on steel trays, in steel boxes, along tensioned steel cables and strings, and also hidden in structural elements buildings.

According to the accepted method of laying conductors, electrical wiring is divided into open and hidden. In industrial buildings, in order to generally reduce the cost of work and save metal, it is recommended to use open pipeless wiring or steel pipes replace with non-metallic ones.

For open pipeless wiring, unprotected insulated wires and unarmored cables are used, so the routes of such wiring at their location must ensure the safety of the wiring from possible damage. Under normal operating conditions, indoor wiring is considered sufficient protection. at a height of at least 2.0 ... 2.5 m from the mark of the clean floor or service platform and at a height of at least 3.5 ... 6.0 m from the ground level outside the premises. In necessary cases, open wiring is protected from touch and mechanical damage with special boxes or pipes.

open postings they take up a lot of space and increase the fire hazard, worsen the appearance of buildings and premises, but in general they are much more economical than hidden wiring. Concealed wiring is carried out in structural elements of buildings, in walls, floors, ceilings, special channels. Office, office, living quarters are now being carried out only concealed wiring.

Rules for laying cable in trays

When the number of wires and cables laid along common routes in industrial premises is very large, it is advisable to use cable laying on trays. Trays are designed for:

• open laying of cables in dry, damp and hot rooms;
• premises with a chemically active environment;
• fire hazardous premises for laying wires and cables allowed for such premises;
• cable half-floors and basements of electric machine rooms;
• passages behind shields and panels of control stations and transitions between them;
• technical floors of buildings and structures.

This electrical power sewerage system is highly flexible, greatly facilitating installation and operation. Tray wiring provides good conditions cooling cables, gives great savings and reduces the cost of work compared to other types of wiring.

The trays create free access to the cables throughout their length. If necessary, the cables can be easily removed and replaced by others; at the same time, you can change their number, section, brand, and also the route.

When using trays, it is easier to carry out wiring on complex routes, it is possible to arrange a branch on any section of the route of the tray line.

Trays are made from steel profiles and stripes. Two types of trays are used: welded (length 2; 2.5 and 3 m, width 400, 200, 100 and 50 mm) and from perforated strips (length 2 m, width 50 and 105 mm). Trays of both types are equipped with connecting corners and bolts for connecting the trays into a trunk. Individual trays and tray lines can be positioned horizontally, vertically and obliquely.

Cables on trays should be laid in one row.

Unarmored cables with voltage up to 1 kV with a cross section of conductors up to 25 mm2 are allowed to be laid in trays in multilayer, bundles and single-layer without gaps. The height of the layers of cables laid in multilayer should be no more than 150 mm. The height (diameter) of the beam should be no more than 100 mm. The distance between bundles of power cables must be at least 20 mm; the distance between bundles of control cables, as well as power and control cables, is not standardized.

Fastening of cables laid in trays on straight sections of the route, with horizontal installation trays are not required; at any other location of the trays, the cables are attached to the trays with an interval of no more than 2 m.

Rules for laying a cable on a cable

In cases where other types of cable laying cannot be applied for technological, structural or economic reasons, cable laying on cables (on a steel rope) is used. The laying of power cables on cables is used in networks with a voltage of up to 1 kV, both indoors (workshops) and outside them. Cable wiring on cables indoors is carried out along columns along and across the building, as well as between walls, and outdoors - as a rule, between the walls of buildings.

For power lines laid on a cable, the same cables are used as for laying inside buildings and structures. Cables laid outside buildings, including under open sheds, must have a protective non-combustible outer coating.

The choice of cable is made depending on the bearing load.

Ropes woven from galvanized steel wires and hot-rolled galvanized steel wire are used as a carrier cable.

The distance between the anchor fastenings of the carrying cable should be no more than 100 m.

The distance between intermediate fasteners should be no more than 30 m when laying one or two cables with a cross section of up to 70 mm2, 12 m when laying more than two cables with a cross section of 70 mm2 and in all cases of laying cables with a cross section of 95 mm2 or more. The distance between cable hangers should be 0.8…1.0 m.

Anchor end structures are attached to building walls or building columns; fastening them to beams and trusses is not allowed.

Rules for laying cables on overpasses and galleries

Flyovers and galleries are an alternative to tunnels and blocks; functionally, they have the same purpose - to organize large cable flows and protect them from mechanical and other damage.

Laying cables with voltage up to 10 kV with a cross section up to 240 mm2 on overpasses and in galleries is used for main and intershop electrical networks in the territories of industrial enterprises.

The use of special cable racks is recommended as the main type of cable laying on the territories of chemical and petrochemical enterprises, where the possibility of spillage of substances destructively acting on cable sheaths is not excluded, at enterprises where the level ground water close to the surface.

It is allowed to use technological racks for combined laying of pipelines and cables. The main types of cable racks are impassable reinforced concrete, metal and combined.

Impassable overpasses are used for:

• laying up to 16, 24 and 40 cables with spans between supports of 6 m,
• for laying 24 and 48 cables - 12 m;

One and two-section flyovers - for laying up to 64 and 128 cables with spans of 6 and 12 m.

The vertical distance between the shelves on impassable overpasses is 200 mm, on walk-throughs - 250 mm.

The horizontal distance between the shelves is 1 m, but it can be increased when developing a specific project, taking into account bearing capacity cable structures. When laying cables in an aluminum sheath with a cross section of 50 mm2 or more, the distance between cable structures is allowed up to 6 m.

The cable sag between structures should be 0.4 m.

For laying on overpasses, cables without an outer combustible cover, having anti-corrosion protection, or with an outer protective cover made of non-combustible material, should be used.