Laying cable ducts in the ground. Intersections and convergence of cables in the ground

SCOPE, DEFINITIONS

2.3.1. This chapter of the Rules applies to cable power lines up to 220 kV, as well as lines performed by control cables. Cable lines of higher voltages are made according to special projects. Additional requirements for cable lines are given in Ch. 7.3, 7.4 and 7.7.

2.3.2. A cable line is a line for the transmission of electricity or its individual impulses, consisting of one or more parallel cables with connecting, locking and end sleeves (terminals) and fasteners, and for oil-filled lines, in addition, with feeders and an oil pressure alarm system.

2.3.3. A cable structure is a structure specially designed to accommodate cables, cable boxes, as well as oil feeders and other equipment designed to ensure the normal operation of oil-filled cable lines. Cable structures include: cable tunnels, channels, boxes, blocks, shafts, floors, double floors, cable racks, galleries, chambers, feeding points.

A cable tunnel is a closed structure (corridor) with supporting structures located in it for placing cables and cable boxes on them, with free passage along the entire length, which allows cable laying, repairs and inspections of cable lines.

A cable channel is a closed and buried (partially or completely) in the ground, floor, ceiling, etc., an impassable structure designed to accommodate cables in it, laying, inspecting and repairing which can only be done with the ceiling removed.

A cable shaft is a vertical cable structure (usually of rectangular section), whose height is several times greater than the side of the section, equipped with brackets or a ladder for people to move along it (walk-through shafts) or a completely or partially removable wall (impassable mines).

A cable floor is a part of a building bounded by a floor and a floor or cover, with a distance between the floor and the protruding parts of the floor or cover of at least 1.8 m.

A double floor is a cavity bounded by the walls of the room, the interfloor overlap and the floor of the room with removable slabs (on the whole or part of the area).

A cable block is a cable structure with pipes (channels) for laying cables in them with wells related to it.

A cable chamber is an underground cable structure, closed with a deaf removable concrete slab, designed for laying cable boxes or for pulling cables into blocks. A chamber that has a hatch to enter it is called a cable well.

A cable overpass is an elevated or ground open horizontal or inclined extended cable structure. Cable overpass can be passable or non-passage.

A cable gallery is an overground or ground closed completely or partially (for example, without side walls) horizontal or inclined extended cable structure.

2.3.4. It is called a box - see 2.1.10.

2.3.5. It is called a tray - see 2.1.11.

2.3.6. A cable oil-filled line of low or high pressure is a line in which the long-term allowable overpressure is:

0.0245-0.294 MPa (0.25-3.0 kgf/cm2) for low-pressure lead-sheathed cables;

0.0245-0.49 MPa (0.25-5.0 kgf/cm2) for low pressure cables in aluminum sheath;

1.08-1.57 MPa (11-16 kgf/cm2) for high pressure cables.

2.3.7. A section of a low-pressure oil-filled cable line is the section of the line between the stop sleeves or the stop and end sleeves.

2.3.8. A feeding point is an above-ground, ground or underground structure with feeding devices and equipment (feed tanks, pressure tanks, feeding units, etc.).

2.3.9. A branching device is a part of a high-pressure cable line between the end of a steel pipeline and end single-phase couplings.

2.3.10. A feeding unit is an automatically operating device consisting of tanks, pumps, pipes, bypass valves, valves, an automation panel and other equipment designed to provide high-pressure cable line oil feeding.

GENERAL REQUIREMENTS

2.3.11. The design and construction of cable lines should be carried out on the basis of technical and economic calculations, taking into account the development of the network, the responsibility and purpose of the line, the nature of the route, the laying method, cable structures, etc.

2.3.12. When choosing a cable line route, areas with soils that are aggressive with respect to the metal sheaths of cables should be avoided, if possible (see also 2.3.44).

2.3.13. Above underground cable lines, in accordance with the current rules for the protection of electrical networks, security zones should be established in the size of the area above the cables:

for cable lines above 1 kV, 1 m on each side of the outermost cables;

for cable lines up to 1 kV, 1 m on each side of the outermost cables, and when cable lines pass in cities under sidewalks - 0.6 m towards buildings and 1 m towards the carriageway of the street.

For submarine cable lines up to and above 1 kV, in accordance with the indicated rules, a security zone should be established, defined by parallel straight lines at a distance of 100 m from the outermost cables.

Security zones of cable lines are used in compliance with the requirements of the rules for the protection of electrical networks.

2.3.14. The route of the cable line should be selected taking into account the lowest cable consumption, ensuring its safety under mechanical stress, ensuring protection against corrosion, vibration, overheating and damage to adjacent cables by an electric arc in the event of a short circuit on one of the cables. When placing cables, avoid crossing them with each other, with pipelines, etc.

When choosing the route of a low-pressure oil-filled cable line, the terrain is taken into account for the most rational placement and use of make-up tanks on the line.

2.3.15. Cable lines must be designed in such a way that during installation and operation, the occurrence of dangerous mechanical stresses and damages in them is excluded, for which:

cables must be laid with a margin in length sufficient to compensate for possible displacements of the soil and temperature deformations of the cables themselves and the structures along which they are laid; laying the cable stock in the form of rings (coils) is prohibited;

cables laid horizontally along structures, walls, ceilings, etc., must be 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 must be fixed so that the deformation of the sheaths is prevented and the connections of the cores in the couplings are not broken under the action of the own weight of the cables;

structures on which unarmored cables are laid must be designed 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 must be protected from mechanical damage and corrosion with the help of elastic gaskets;

cables (including armored ones) located in places where mechanical damage is possible (movement of vehicles, mechanisms and goods, accessibility for unauthorized persons) must be protected in height by 2 m from the floor or ground level and by 0.3 m in earth;

when laying cables next to other cables in operation, measures must be taken to prevent damage to them;

cables should be laid at a distance from heated surfaces, which prevents the cables from heating above the permissible level, while protecting the cables from the breakthrough of hot substances at the installation sites of valves and flange connections should be provided.

2.3.16. Protection of cable lines against stray currents and soil corrosion must meet the requirements of these Rules and SNiP 3-04.03-85 "Protection of building structures and structures against corrosion" of the State Construction Committee of Russia.

2.3.17. The structures of underground cable structures must be calculated taking into account the mass of cables, soil, road surface and the load from passing traffic.

2.3.18. Cable structures and structures on which cables are laid must be made of non-combustible materials. It is forbidden to perform any temporary devices in cable structures, store materials and equipment in them. Temporary cables must be laid in compliance with all requirements for cable laying, with the permission of the operating organization.

2.3.19. Open laying of cable lines should be carried out taking into account the direct action of solar radiation, as well as heat radiation from various types of heat sources. When laying cables at a geographic latitude of more than 65 °, protection from solar radiation is not required.

2.3.20. The radii of the inner bending curve of the cables must have, in relation to their outer diameter, a multiplicity of not less than those specified in the standards or specifications for the corresponding brands of cables.

2.3.21. The radii of the internal bending curve of the cable cores when making cable terminations must have, in relation to the reduced core diameter, a multiplicity of at least those specified in the standards or specifications for the corresponding cable brands.

2.3.22. The tensile forces during laying cables and pulling them in pipes are determined by the mechanical stresses allowed for the cores and shells.

2.3.23. Each cable line must have its own number or name. If the cable line consists of several parallel cables, then each of them must have the same number with the addition of the letters A, B, C, etc. Openly laid cables, as well as all cable boxes, must be tagged with the designation on the cable tags and end couplings of the brand, voltage, section, number or name of the line; on the tags of the couplings - the number of the coupling and the date of installation. Labels must be impact resistant environment. On cables laid in cable structures, tags must be located along the length at least every 50 m.

2.3.24. Protective zones of cable lines laid in the ground in undeveloped areas must be marked with information signs. Information signs should be installed at least every 500 m, as well as in places where the direction of cable lines changes. The information signs should indicate the width of the security zones of cable lines and the telephone numbers of cable line owners. (see Appendix "Requirements for information signs and their installation")

CHOICE OF LAYING METHODS

2.3.25. When choosing methods for laying power cable lines up to 35 kV, you must be guided by the following:

1. When laying cables in the ground, it is recommended to lay no more than six power cables. With a larger number of cables, it is recommended to lay them in separate trenches with a distance between cable groups of at least 0.5 m or in channels, tunnels, overpasses and in galleries.

2. Laying cables in tunnels, overpasses and in galleries is recommended when the number of power cables running in one direction is more than 20.

3. Laying cables in blocks is used in conditions of great constraint along the route, at intersections with railway tracks and driveways, with the likelihood of a metal spill, etc.

4. When choosing methods for laying cables across urban areas, the initial capital costs and costs associated with the production of maintenance and repair work, as well as the convenience and cost-effectiveness of maintaining structures, should be taken into account.

2.3.26. On the territories of power plants, cable lines should be laid in tunnels, ducts, channels, blocks, overpasses and in galleries. Laying power cables in trenches is allowed only to remote auxiliary facilities (fuel depots, workshops) with no more than six. In the territories of power plants with a total capacity of up to 25 MW, it is also allowed to lay cables in trenches.

2.3.27. On the territories of industrial enterprises, cable lines should be laid in the ground (in trenches), tunnels, blocks, channels, overpasses, in galleries and along the walls of buildings.

2.3.28. On the territories of substations and switchgears, cable lines should be laid in tunnels, ducts, channels, pipes, in the ground (in trenches), ground reinforced concrete trays, along overpasses and in galleries.

2.3.29. In cities and towns, single cable lines should, as a rule, be laid in the ground (in trenches) along the impassable part of the streets (under sidewalks), in yards and technical lanes in the form of lawns.

2.3.30. On streets and squares saturated with underground utilities, it is recommended to lay cable lines in the amount of 10 or more in a stream in collectors and cable tunnels. When crossing streets and squares with improved coatings and with heavy traffic, cable lines should be laid in blocks or pipes.

2.3.31. When constructing cable lines in permafrost areas, physical phenomena associated with the nature of permafrost should be taken into account: heaving soil, frost cracks, landslides, etc. Depending on local conditions, cables can be laid in the ground (in trenches) below the active layer, in in the active layer in dry, well-draining soils, in artificial embankments from large-skeletal dry imported soils, in trays on the surface of the earth, on overpasses. Joint laying of cables with heating pipelines, water supply, sewerage, etc. in special structures (collectors) is recommended.

2.3.32. The implementation of various types of cable laying in permafrost areas should be carried out taking into account the following:

1. For laying cables in earthen trenches, the most suitable soils are draining soils (rocky, pebble, gravel, crushed stone and coarse sand); heaving and subsidence soils are unsuitable for laying cable lines in them. It is allowed to lay cables directly in the ground with no more than four cables. Due to ground-frozen and climatic conditions, it is prohibited to lay cables in pipes laid in the ground. At intersections with other cable lines, roads and underground utilities, cables should be protected with reinforced concrete slabs.

Laying cables near buildings is not allowed. The entry of cables from the trench into the building in the absence of a ventilated underground must be carried out above the zero mark.

2. Laying cables in channels is allowed to be used in places where the active layer consists of non-rocky soils and has a flat surface with a slope of not more than 0.2%, which ensures the runoff of surface water. Cable channels should be made of waterproof reinforced concrete and covered with reliable waterproofing from the outside. From above, the channels must be closed with reinforced concrete slabs. Channels can be made deep into the ground and without deepening (above the ground). In the latter case, under the channel and near it, a pillow with a thickness of at least 0.5 m from dry soil should be made.

2.3.33. Inside buildings, cable lines can be laid directly along building structures (openly and in boxes or pipes), in channels, blocks, tunnels, pipes laid in floors and ceilings, as well as on machine foundations, in mines, cable floors and double floors.

2.3.34. Oil-filled cables can be laid (with any number of cables) in tunnels and galleries and in the ground (in trenches); the way they are laid is determined by the project.

CABLE SELECTION

2.3.35. For cable lines laid along routes running in various soils and environmental conditions, the choice of cable designs and cross-sections should be made for the section with the most severe conditions, if the length of the sections with lighter conditions does not exceed the construction length of the cable. With a significant length of individual sections of the route with different laying conditions, appropriate designs and cable sections should be selected for each of them.

2.3.36. For cable lines laid along routes with different cooling conditions, the cable sections should be selected along the section of the route with the worst cooling conditions, if its length is more than 10 m. It is allowed for cable lines up to 10 kV, with the exception of submarine ones, the use of cables of different sections, but not more than three, provided that the length of the smallest segment is not less than 20 m (see also 2.3.70).

2.3.37. For cable lines laid in the ground or water, armored cables should be used predominantly. The metal sheaths of these cables must have an outer jacket to protect them from chemical attack. Cables with other designs of external protective coatings (unarmoured) must have the necessary resistance to mechanical stress when laying in all types of soil, when pulled in blocks and pipes, as well as resistance to thermal and mechanical stress during maintenance and repair work.

2.3.38. Pipelines of high-pressure oil-filled cable lines laid in earth or water must be protected against corrosion in accordance with the design.

2.3.39. In cable structures and industrial premises, if there is no danger of mechanical damage in operation, it is recommended to lay unarmored cables, and if there is a danger of mechanical damage in operation, armored cables or their protection from mechanical damage should be used.

Outside cable structures, it is allowed to lay unarmored cables at an inaccessible height (at least 2 m); at a lower height, the laying of unarmored cables is allowed provided that they are protected from mechanical damage (boxes, angle steel, pipes, etc.).

For mixed laying (ground - cable structure or industrial premises), it is recommended to use the same brands of cables as for laying in the ground (see 2.3.37), but without combustible outer protective covers.

2.3.40. When laying cable lines in cable structures, as well as in industrial premises, armored cables should not have protective covers made of combustible materials over the armor, and unarmored cables over metal sheaths.

For open laying, it is not allowed to use power and control cables with combustible polyethylene insulation.

Metal sheaths of cables and metal surfaces on which they are laid must be protected with a non-combustible anti-corrosion coating.

When laying in rooms with an aggressive environment, cables resistant to this environment must be used.

2.3.41. For cable lines of power plants, switchgears and substations specified in 2.3.76, it is recommended to use cables armored with steel tape protected by a non-combustible coating. At power plants, the use of cables with combustible polyethylene insulation is not allowed.

2.3.42. For cable lines laid in cable blocks and pipes, as a rule, unarmoured cables in a lead reinforced sheath should be used. In sections of blocks and pipes, as well as branches from them up to 50 m long, it is allowed to lay armored cables in a lead or aluminum sheath without an outer cover of cable yarn. For cable lines laid in pipes, it is allowed to use cables in a plastic or rubber sheath.

2.3.43. For laying in soils containing substances that are destructive to cable sheaths (salt marshes, swamps, bulk soil with slag and building material, etc.), as well as in areas hazardous due to electrical corrosion, cables with lead sheaths should be used and reinforced protective covers of types B, B or cables with aluminum sheaths and especially reinforced protective covers of types B, B (in a continuous moisture-resistant plastic hose).

2.3.44. In places where cable lines cross swamps, cables should be selected taking into account geological conditions, as well as chemical and mechanical influences.

2.3.45. For laying in soils subject to displacement, cables with wire armor should be used or measures should be taken to eliminate the forces acting on the cable during soil displacement (reinforcement of the soil with sheet piles or pile rows, etc.).

2.3.46. In places where cable lines cross streams, their floodplains and ditches, the same cables should be used as for laying in the ground (see also 2.3.99).

2.3.47. For cable lines laid on railway bridges, as well as on other bridges with heavy traffic, it is recommended to use armored cables in an aluminum sheath.

2.3.48. For cable lines of mobile mechanisms, flexible cables with rubber or other similar insulation that can withstand multiple bends should be used (see also 1.7.111).

2.3.49. For submarine cable lines, cables with round wire armor should be used, if possible of the same construction length. For this purpose, the use of single-core cables is permitted.

In places where cable lines cross from the shore to the sea in the presence of strong sea surf, when laying the cable in sections of rivers with strong currents and eroded banks, as well as at great depths (up to 40-60 m), a cable with double metal armor should be used.

Cables with rubber insulation in a PVC sheath, as well as cables in an aluminum sheath without special waterproof coatings for laying in water are not allowed.

When laying cable lines through small non-navigable and non-alloyable rivers with a width (together with a floodplain) of no more than 100 m, with a stable channel and bottom, it is allowed to use cables with tape armor.

2.3.50. For oil-filled cable lines with a voltage of 110-220 kV, the type and design of the cables are determined by the project.

2.3.51. When laying cable lines up to 35 kV on vertical and inclined sections of the route with a level difference exceeding the allowable according to GOST for cables with viscous impregnation, cables with non-draining impregnating mass, cables with depleted impregnated paper insulation and cables with rubber or plastic insulation should be used. For the specified conditions, cables with viscous impregnation can only be used with locking sleeves located along the route, in accordance with the permissible level differences for these cables in accordance with GOST.

The difference in vertical marks between the stop sleeves of low-pressure oil-filled cable lines is determined by the relevant technical conditions for the cable and the calculation of make-up at extreme thermal conditions.

2.3.52. Four-wire networks must use four-wire cables. Laying of zero conductors separately from phase conductors is not allowed. It is allowed to use three-core power cables in an aluminum sheath with a voltage of up to 1 kV using their sheath as a neutral wire (fourth core) in four-wire networks alternating current(lighting, power and mixed) with a solidly grounded neutral, with the exception of installations with an explosive environment and installations in which, under normal operating conditions, the current in the neutral wire is more than 75% of the allowable long-term current of the phase wire.

The use of lead sheaths of three-core power cables for this purpose is allowed only in reconstructed urban electrical networks 220/127 and 380/220 V.

2.3.53. For cable lines up to 35 kV, it is allowed to use single-core cables if this leads to significant savings in copper or aluminum in comparison with three-core ones, or if it is not possible to use a cable of the required building length. The cross section of these cables must be selected taking into account their additional heating by currents induced in the sheaths.

Measures must also be taken to ensure equal distribution of current between cables connected in parallel and safe contact with their sheaths, to exclude heating of metal parts located in the immediate vicinity and to securely fasten the cables in insulating clamps.

FEEDING DEVICES AND ALARM OF OIL PRESSURE OF CABLE OIL FILLED LINES

2.3.54. The oil feed system must ensure reliable operation of the line in any normal and transient thermal conditions.

2.3.55. The amount of oil in the oil feeding system should be determined taking into account the consumption for feeding the cable. In addition, there must be a supply of oil for emergency repairs and oil filling of the longest section of the cable line.

2.3.56. Feed tanks of low pressure lines are recommended to be placed indoors. A small number of feed tanks (5-6) at open food points are recommended to be placed in light metal boxes on portals, supports, etc. (at an ambient temperature of at least minus 30 ° C). Make-up tanks must be equipped with oil pressure gauges and protected from direct sunlight.

2.3.57. Feeding units of high-pressure lines must be placed in enclosed spaces with a temperature not lower than +10°C, and located as close as possible to the point of connection to cable lines (see also 2.3.131). Several feeding units are connected to the line through an oil manifold.

2.3.58. When laying several high-pressure oil-filled cable lines in parallel, it is recommended that each line be fed with oil from separate feeding units, or a device should be installed to automatically switch the units to one or another line.

2.3.59. Feeding units are recommended to be supplied with electricity from two independent power sources with a mandatory automatic transfer switch (ATS). Feeding units must be separated from one another by fireproof partitions with a fire resistance limit of at least 0.75 hours.

2.3.60. Each cable oil-filled line must have an oil pressure alarm system that provides registration and transmission to duty personnel of signals about a decrease and increase in oil pressure in excess of permissible limits.

2.3.61. At least two sensors must be installed on each section of the low pressure oil-filled cable line, and a sensor on each feeding unit should be installed on the high pressure line. Emergency signals should be transmitted to a point with constant duty of personnel. The oil pressure alarm system must be protected from the influence of electric fields of power cable lines.

2.3.62. Feeding points on low pressure lines must be equipped with telephone communication with control points (power grids, network area).

2.3.63. The oil pipeline connecting the collector of the feeding unit with the high-pressure oil-filled cable line must be laid in rooms with a positive temperature. It is allowed to lay it in insulated trenches, trays, channels and in the ground below the freezing zone, provided that a positive ambient temperature is ensured.

2.3.64. Vibration in the room of the switchboard with devices for automatic control of the feeding unit should not exceed the permissible limits.

CONNECTIONS AND CABLE TERMINATIONS

2.3.65. When connecting and terminating power cables, coupling designs should be used that correspond to their operating conditions and the environment. Connections and terminations on cable lines must be made so that the cables are protected from the penetration of moisture and other harmful substances from the environment into them and that the connections and terminations withstand the test voltages for the cable line and comply with the requirements of GOST.

2.3.66. For cable lines up to 35 kV, terminations and couplings must be used in accordance with the current technical documentation for couplings approved in the prescribed manner.

2.3.67. For connecting and locking sleeves of oil-filled low-pressure cable lines, only brass or copper sleeves must be used.

The length of the sections and the location of the stop sleeves on the low-pressure oil-filled cable lines are determined taking into account the replenishment of the lines with oil in normal and transient thermal conditions.

Locking and semi-locking couplings on cable oil-filled lines must be placed in cable wells; when laying cables in the ground, it is recommended to place couplings in chambers that are subject to subsequent backfilling with sifted earth or sand.

In areas with electrified transport (metro, trams, railways) or with soils that are aggressive towards metal sheaths and cable line couplings, couplings must be accessible for control.

2.3.68. On cable lines made by cables with normally impregnated paper insulation and cables impregnated with non-draining mass, cable connections should be made using stop-and-go couplings if the level of laying cables with normally impregnated insulation is higher than the level of laying cables impregnated with non-draining mass (see also 2.3 .51).

2.3.69. On cable lines above 1 kV, carried out by flexible cables with rubber insulation in a rubber hose, cable connections must be made by hot vulcanization coated with anti-damp varnish.

2.3.70. The number of couplings per 1 km of newly constructed cable lines should be no more than: for three-core cables 1-10 kV with a cross section of up to 3x95 mm2 4 pcs.; for three-core cables 1-10 kV with sections 3x120 - 3x240 mm2 5 pcs.; for three-phase cables 20-35 kV 6 pcs.; for single-core cables 2 pcs.

For cable lines 110-220 kV, the number of couplings is determined by the project.

The use of small-sized cable segments for the construction of extended cable lines is not allowed.

GROUNDING

2.3.71. Cables with metal sheaths or armor, as well as cable structures on which cables are laid, must be grounded or neutralized in accordance with the requirements given in Ch. 1.7.

2.3.72. When grounding or grounding the metal sheaths of power cables, the sheath and armor must be connected by a flexible copper wire to each other and to the housings of the couplings (terminal, connecting, etc.). On cables of 6 kV and above with aluminum sheaths, the sheath and armor grounding must be carried out by separate conductors.

It is not required to use grounding or neutral protective conductors with a conductivity greater than the conductivity of the cable sheaths, however, the cross section in all cases must be at least 6 mm2.

Cross-sections of grounding conductors of control cables should be selected in accordance with the requirements of 1.7.76-1.7.78.

If an external end sleeve and a set of arresters are installed on the structure support, then the armor, metal sheath and sleeve must be connected to the grounding device of the arresters. The use of only metal sheaths of cables as a grounding device in this case is not allowed.

Overpasses and galleries must be equipped with lightning protection in accordance with RD 34.21.122-87 "Instructions for the installation of lightning protection for buildings and structures" of the USSR Ministry of Energy.

2.3.73. On cable oil-filled low-pressure lines, end, connecting and locking couplings are grounded.

On cables with aluminum sheaths, feeders must be connected to the lines through insulating inserts, and the end sleeve housings must be insulated from the aluminum sheaths of the cables. This requirement does not apply to cable lines with direct entry into transformers.

When using armored cables for oil-filled low-pressure cable lines in each well, the cable armor on both sides of the coupling must be welded and grounded.

2.3.74. The steel pipeline of high-pressure oil-filled cable lines laid in the ground must be grounded in all wells and at the ends, and those laid in cable structures - at the ends and at intermediate points determined by the calculations in the project.

If it is necessary to actively protect the steel pipeline from corrosion, its grounding is carried out in accordance with the requirements of this protection, while it must be possible to control the electrical resistance of the anti-corrosion coating.

2.3.75. When a cable line passes into an overhead line (VL) and if there is no grounding device at the overhead line support, cable boxes (masts) can be grounded by attaching the metal sheath of the cable if the cable box at the other end of the cable is connected to a grounding device or the grounding resistance of the cable sheath meets the requirements of Ch. 1.7.

SPECIAL REQUIREMENTS FOR CABLE FACILITIES OF POWER PLANTS, SUBSTATIONS AND SWITCHGEAR

2.3.76. The requirements given in 2.3.77-2.3.82 apply to cable facilities of thermal and hydroelectric power plants with a capacity of 25 MW or more, switchgears and substations with a voltage of 220-500 kV, as well as switchgears and substations of particular importance in the power system (see. also 2.3.113).

2.3.77. The main electrical connection diagram, auxiliary circuit and operating current circuit, equipment control and layout of equipment and cable facilities of a power plant or substation must be carried out in such a way that in the event of fires in the cable facilities or outside it, disruption of the operation of more than one unit of the power plant is excluded, simultaneous loss of mutually redundant connections of distribution devices and substations, as well as failure of fire detection and extinguishing systems.

2.3.78. For the main cable flows of power plants, cable structures (floors, tunnels, shafts, etc.) should be provided, isolated from process equipment and excluding access to cables by unauthorized persons.

When placing cable flows at power plants, cable line routes should be selected taking into account:

preventing overheating of cables from heated surfaces of process equipment;

prevention of damage to cables during exhausts (fires and explosions) of dust through the safety devices of dust systems;

preventing the laying of transit cables in technological tunnels for hydraulic ash removal, chemical water treatment facilities, as well as in places where pipelines with chemically aggressive liquids are located.

2.3.79. Mutually redundant critical cable lines (power, operational current, communications, control, signaling, fire extinguishing systems, etc.) should be laid so that during fires the possibility of simultaneous loss of mutually redundant cable lines is excluded. In sections of the cable industry, where the occurrence of an accident threatens it great development, cable streams should be divided into groups isolated from one another. The distribution of cables into groups is accepted depending on local conditions.

2.3.80. Within one power unit, it is allowed to build cable structures with a fire resistance limit of 0.25 hours. At the same time, technological equipment that can serve as a source of fire (tanks with oil, oil stations, etc.) must have fences with a fire resistance limit of at least 0.75 h, excluding the possibility of ignition of cables in the event of a fire on this equipment.

Within one power unit of a power plant, it is allowed to lay cables outside special cable structures, provided that they are reliably protected from mechanical damage and dust, from sparks and fire during the repair of process equipment, ensuring normal temperature conditions for cable lines and ease of maintenance.

To provide access to cables when they are located at a height of 5 m or more, special platforms and passages should be constructed.

For single cables and small groups of cables (up to 20), operational sites may not be built, but it must be possible to quickly replace and repair cables in the field.

When laying cables within one power unit outside special cable structures, it should be ensured, if possible, that they are divided into separate groups passing along different routes.

2.3.81. Cable floors and tunnels, in which cables of various power units of the power plant are located, including cable floors and tunnels under block control panels, must be divided block by block and separated from other rooms, cable floors, tunnels, shafts, ducts and channels by fireproof partitions and ceilings with a fire resistance limit not less than 0.75 h, including in places where cables pass.

In places where cables are supposed to pass through partitions and ceilings, in order to ensure the possibility of replacement and additional laying of cables, a partition made of fireproof, easily pierced material with a fire resistance of at least 0.75 hours should be provided.

In extended cable structures of thermal power plants, emergency exits should be provided, located, as a rule, at least 50 m apart.

Cable facilities of power plants must be separated from outgoing network cable tunnels and collectors by fireproof partitions with a fire resistance limit of at least 0.75 hours.

2.3.82. The places where cables enter the rooms of closed switchgears and the rooms of control and protection panels of open switchgears must have partitions with a fire resistance limit of at least 0.75 hours.

The places where cables enter the block control panels of the power plant must be closed with partitions with a fire resistance limit of at least 0.75 hours.

Cable shafts must be separated from cable tunnels, floors and other cable structures by fireproof partitions with a fire resistance of at least 0.75 hours and have ceilings at the top and bottom. Extended shafts when passing through ceilings, but at least every 20 m, should be divided into compartments by fireproof partitions with a fire resistance of at least 0.75 hours.

Passage cable shafts must have entrance doors and be equipped with ladders or special brackets.

LAYING CABLE LINES IN THE GROUND

2.3.83. When laying cable lines directly in the ground, the cables must be laid in trenches and have backfilling from below, and backfilling from above with a layer of fine earth that does not contain stones, construction debris and slag.

Cables throughout their entire length must be protected from mechanical damage by coating at a voltage of 35 kV and above with reinforced concrete slabs with a thickness of at least 50 mm; at voltages below 35 kV - with slabs or ordinary clay bricks in one layer across the cable route; when digging a trench with an earthmoving mechanism with a cutter width of less than 250 mm, as well as for one cable - along the cable line route. The use of silicate, as well as clay hollow or perforated bricks is not allowed.

When laying at a depth of 1-1.2 m, cables of 20 kV and below (except for city power cables) may not be protected from mechanical damage.

Cables up to 1 kV should have such protection only in areas where mechanical damage is likely (for example, in places of frequent excavations). Asphalt pavements of streets, etc. are regarded as places where excavation is carried out in rare cases. For cable lines up to 20 kV, except for lines above 1 kV, supplying electrical receivers of category I *, it is allowed to use signal plastic tapes instead of bricks in trenches with no more than two cable lines that meet the technical requirements approved by the USSR Ministry of Energy. It is not allowed to use signal tapes at the intersections of cable lines with utilities and above cable boxes at a distance of 2 m in each direction from the crossed communication or box, as well as at the approaches of lines to switchgears and substations within a radius of 5 m.

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* According to local conditions, with the consent of the owner of the lines, it is allowed to expand the scope of signal tapes.

The signal tape should be laid in a trench above the cables at a distance of 250 mm from their outer covers. When one cable is located in a trench, the tape should be laid along the axis of the cable, with a larger number of cables, the edges of the tape should protrude beyond the outermost cables by at least 50 mm. When laying more than one tape across the width of the trench, adjacent tapes must be laid with an overlap of at least 50 mm wide.

When using a signal tape, laying cables in a trench with a cable cushion device, sprinkling the cables with the first layer of earth and laying the tape, including sprinkling the tape with a layer of earth along the entire length, must be carried out in the presence of a representative of the electrical installation organization and the owner of the power grid.

2.3.84. The depth of cable lines from the planning mark should be at least: lines up to 20 kV 0.7 m; 35 kV 1 m; at the intersection of streets and squares, regardless of voltage 1 m.

Cable oil-filled lines 110-220 kV must have a laying depth from the planning mark of at least 1.5 m.

It is allowed to reduce the depth to 0.5 m in sections up to 5 m long when lines are introduced into buildings, as well as at their intersections with underground structures, provided that the cables are protected from mechanical damage (for example, laying in pipes).

The laying of 6-10 kV cable lines on arable land should be carried out at a depth of at least 1 m, while the strip of land above the route can be occupied by crops.

2.3.85. The clear distance from the cable laid directly in the ground to the foundations of buildings and structures must be at least 0.6 m. Laying cables directly in the ground under the foundations of buildings and structures is not allowed. When laying transit cables in the basements and technical undergrounds of residential and public buildings, one should be guided by the SNiP of the Gosstroy of Russia.

2.3.86. With parallel laying of cable lines, the horizontal distance in the light between the cables must be at least:

1) 100 mm between power cables up to 10 kV, as well as between them and control cables;

2) 250 mm between 20-35 kV cables and between them and other cables;

3) 500 mm* between cables operated by different organizations, as well as between power cables and communication cables;

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4) 500 mm between 110-220 kV oil-filled cables and other cables; at the same time, low-pressure oil-filled cable lines are separated from one another and from other cables by reinforced concrete slabs placed on edge; in addition, the electromagnetic influence on communication cables should be calculated.

It is allowed, if necessary, by agreement between operating organizations, taking into account local conditions, reducing the distances specified in clauses 2 and 3 to 100 mm, and between power cables up to 10 kV and communication cables, except for cables with circuits sealed by high-frequency telephone communication systems, up to 250 mm, provided that the cables are protected from damage that may occur during a short circuit in one of the cables (laying in pipes, installing fireproof partitions, etc.).

The distance between the control cables is not standardized.

2.3.87. When laying cable lines in the plantation zone, the distance from the cables to the tree trunks should, as a rule, be at least 2 m. It is allowed, in agreement with the organization in charge of the green spaces, to reduce this distance, provided that the cables are laid in pipes laid by digging .

When laying cables within the green zone with shrub plantings, the indicated distances can be reduced to 0.75 m.

2.3.88. With parallel laying, the horizontal distance in the light from cable lines with voltage up to 35 kV and oil-filled cable lines to pipelines, water supply, sewerage and drainage must be at least 1 m; to gas pipelines of low (0.0049 MPa), medium (0.294 MPa) and high pressure (more than 0.294 to 0.588 MPa) - at least 1 m; to high pressure gas pipelines (more than 0.588 to 1.176 MPa) - at least 2 m; to heat pipelines - see 2.3.89.

In cramped conditions, it is allowed to reduce the specified distances for cable lines to 35 kV, with the exception of distances to pipelines with flammable liquids and gases, up to 0.5 m without special cable protection and up to 0.25 m when laying cables in pipes. For oil-filled cable lines 110-220 kV in the approach section no longer than 50 m, it is allowed to reduce the horizontal distance in the light to pipelines, with the exception of pipelines with flammable liquids and gases, to 0.5 m, provided that a protective wall is installed between the oil-filled cables and the pipeline excluding the possibility of mechanical damage. Parallel laying of cables above and below pipelines is not allowed.

2.3.89. When laying a cable line in parallel with a heat pipeline, the clear distance between the cable and the wall of the heat pipeline channel must be at least 2 m, or the heat pipeline in the entire area of ​​approach to the cable line must have such thermal insulation that additional heating of the earth by the heat pipeline at the place where the cables pass at any time of the year is not exceeded 10°C for cable lines up to 10 kV and 5°C - for lines 20-220 kV.

2.3.90. When laying a cable line in parallel with railways, cables should be laid, as a rule, outside the exclusion zone of the road. Laying cables within the exclusion zone is allowed only upon agreement with the organizations of the Ministry of Railways, while the distance from the cable to the axis of the railway track must be at least 3.25 m, and for an electrified road - at least 10.75 m. In cramped conditions it is allowed to reduce the specified distances, while the cables in the entire approach section must be laid in blocks or pipes.

On electrified roads DC blocks or pipes must be insulating (asbestos-cement, impregnated with tar or bitumen, etc.) *.

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2.3.91. When laying a cable line in parallel with tram tracks, the distance from the cable to the axis of the tram track must be at least 2.75 m. 2.3.90.

2.3.92. When laying a cable line in parallel with motor roads of categories I and II (see 2.5.145), cables must be laid on the outside of the ditch or the bottom of the embankment at a distance of at least 1 m from the edge or at least 1.5 m from the curb stone. Reducing the specified distance is allowed in each individual case in agreement with the relevant road administrations.

2.3.93. When laying a cable line in parallel with an overhead line of 110 kV and above, the distance from the cable to the vertical plane passing through the outermost wire of the line must be at least 10 m.

The clear distance from the cable line to grounded parts and ground electrodes of overhead lines above 1 kV must be at least 5 m at voltages up to 35 kV, 10 m at voltages of 110 kV and above. In cramped conditions, the distance from cable lines to underground parts and ground electrodes of individual overhead lines above 1 kV is allowed at least 2 m; at the same time, the distance from the cable to the vertical plane passing through the overhead line wire is not standardized.

The clear distance from the cable line to the overhead line support up to 1 kV must be at least 1 m, and when laying the cable in the approach area in an insulating pipe, 0.5 m.

In the territories of power plants and substations in cramped conditions, it is allowed to lay cable lines at distances of at least 0.5 m from the underground part of overhead communication towers (current conductors) and overhead lines above 1 kV, if the grounding devices of these towers are connected to the substation ground loop.

2.3.94*. When cable lines cross other cables, they must be separated by a layer of earth with a thickness of at least 0.5 m; this distance in cramped conditions for cables up to 35 kV can be reduced to 0.15 m, provided that the cables are separated along the entire intersection plus 1 m in each direction by slabs or pipes made of concrete or other equal strength material; the communication cables must be located above the power cables.

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* Agreed with the Ministry of Communications of the USSR.

2.3.95. When cable lines cross pipelines, including oil and gas pipelines, the distance between the cables and the pipeline must be at least 0.5 m. It is allowed to reduce this distance to 0.25 m, provided that the cable is laid at the intersection plus at least 2 m in each direction in pipes.

When crossing a cable oil-filled line of pipelines, the clear distance between them must be at least 1 m. For cramped conditions, it is allowed to take a distance of at least 0.25 m, but provided that the cables are placed in pipes or reinforced concrete trays with a lid.

2.3.96. When crossing cable lines up to 35 kV heat pipelines, the distance between the cables and the overlap of the heat pipeline in the light must be at least 0.5 m, and in cramped conditions - at least 0.25 m. In this case, the heat pipeline at the intersection plus 2 m in each direction from the outermost cables must have such thermal insulation that the temperature of the earth does not rise by more than 10 ° C in relation to the highest summer temperature and by 15 ° C in relation to the lowest winter temperature.

In cases where the specified conditions cannot be met, one of the following measures is allowed: deepening of cables to 0.5 m instead of 0.7 m (see 2.3.84); use of a cable insert of a larger cross section; laying cables under the heat pipeline in pipes at a distance of at least 0.5 m from it, while the pipes must be laid in such a way that the cables can be replaced without excavation (for example, inserting pipe ends into chambers).

When crossing a cable oil-filled line of a heat pipe, the distance between the cables and the overlap of the heat pipe must be at least 1 m, and in cramped conditions - at least 0.5 m. thermal insulation so that the temperature of the earth does not rise by more than 5 ° C at any time of the year.

2.3.97. When cable lines cross railways and roads, cables must be laid in tunnels, blocks or pipes across the entire width of the exclusion zone at a depth of at least 1 m from the roadbed and at least 0.5 m from the bottom of drainage ditches. In the absence of an exclusion zone, the specified laying conditions must be met only at the intersection plus 2 m on both sides of the roadbed.

When cable lines cross electrified and subject to electrification at direct current * railways blocks and pipes shall be insulating (see 2.3.90). The crossing point must be at least 10 m away from switches, crosses and places where suction cables are attached to the rails. The crossing of cables with the tracks of electrified rail transport should be carried out at an angle of 75-90 ° to the axis of the track.

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* Agreed with the Ministry of Railways.

The ends of the blocks and pipes must be sunk with jute braided cords coated with waterproof (crumpled) clay to a depth of at least 300 mm.

When crossing dead-end industrial roads with low traffic intensity, as well as special routes (for example, on slipways, etc.), cables, as a rule, should be laid directly in the ground.

When crossing the route of cable lines by a newly constructed non-electrified railway or a motor road, it is not required to re-lay existing cable lines. At the intersection, reserve blocks or pipes with tightly sealed ends should be laid in the event of repair of cables in the required number.

In the event of a cable line transitioning into an overhead cable, it must come out to the surface at a distance of at least 3.5 m from the bottom of the embankment or from the edge of the canvas.

2.3.98. When cable lines cross tram tracks, cables must be laid in insulating blocks or pipes (see 2.3.90). The crossing must be carried out at a distance of at least 3 m from the switches, crosses and places where suction cables are attached to the rails.

2.3.99. When cable lines cross entrances for vehicles to yards, garages, etc., cables should be laid in pipes. In the same way, cables must be protected at the intersection of streams and ditches.

2.3.100. When installing cable boxes on cable lines, the clear distance between the cable box body and the nearest cable must be at least 250 mm.

When laying cable lines on steep routes, the installation of cable boxes on them is not recommended. If it is necessary to install cable boxes in such sections, horizontal platforms must be made under them.

To ensure the possibility of remounting the couplings in case of their damage on the cable line, it is required to lay the cable on both sides of the couplings with a margin.

2.3.101. If there are stray currents of dangerous values ​​along the cable line route, it is necessary:

1. Change the route of the cable line in order to avoid dangerous areas.

2. If it is impossible to change the route: provide for measures to minimize the levels of stray currents; use cables with increased resistance to corrosion; to carry out active protection of cables from the effects of electrocorrosion.

When laying cables in aggressive soils and areas with the presence of stray currents of unacceptable values, cathodic polarization should be used (installation of electrical drains, protectors, cathodic protection). For any method of connecting electrical drainage devices, the norms of potential differences in the suction sections, provided for by SNiP 3.04.03-85 "Protection of building structures and structures against corrosion" of the Gosstroy of Russia, must be observed. It is not recommended to use cathodic protection with external current on cables laid in saline soils or saline water bodies.

The need to protect cable lines from corrosion should be determined from the aggregate data of electrical measurements and chemical analyzes soil samples. Corrosion protection of cable lines should not create conditions dangerous for the operation of adjacent underground structures. The designed corrosion protection measures must be implemented before the new cable line is put into operation. In the presence of stray currents in the ground, it is necessary to install control points on cable lines in places and at distances that allow determining the boundaries of dangerous zones, which is necessary for the subsequent rational selection and placement of protective equipment.

To control potentials on cable lines, it is allowed to use the cable outlets on transformer substations, distribution points, etc.

LAYING OF CABLE LINES IN CABLE BLOCKS, PIPES AND REINFORCED CONCRETE TRAYS

2.3.102. For the manufacture of cable blocks, as well as for laying cables in pipes, it is allowed to use steel, cast iron asbestos-cement, concrete, ceramic and similar pipes. When choosing a material for blocks and pipes, one should take into account the level of groundwater and their aggressiveness, as well as the presence of stray currents.

Oil-filled single-phase low pressure cables must be laid only in asbestos-cement and other pipes made of non-magnetic material, and each phase must be laid in a separate pipe.

2.3.103. The allowable number of channels in blocks, the distances between them and their size should be taken in accordance with 1.3.20.

2.3.104. Each cable block must have up to 15% redundant channels, but not less than one channel.

2.3.105. The depth of laying cable blocks and pipes in the ground should be taken according to local conditions, but not less than the distances given in 2.3.84, counting to the top cable. The depth of laying of cable blocks and pipes in closed areas and in the floors of industrial premises is not standardized.

2.3.106. Cable blocks must have a slope of at least 0.2% towards the wells. The same slope must be observed when laying pipes for cables.

2.3.107. When laying pipes for cable lines directly in the ground, the smallest clear distances between pipes and between them and other cables and structures should be taken as for cables laid without pipes (see 2.3.86).

When laying cable lines in pipes in the floor of the room, the distances between them are taken as for laying in the ground.

2.3.108. In places where the direction of the route of cable lines laid in blocks changes, and in places where cables and cable blocks go into the ground, cable wells should be constructed to ensure convenient pulling of cables and their removal from blocks. Such wells should also be built on straight sections of the route at a distance from one another, determined by the maximum allowable tension of the cables. With the number of cables up to 10 and voltage not higher than 35 kV, the transition of cables from the blocks to the ground is allowed to be carried out without cable wells. In this case, the exit points of the cables from the blocks must be sealed with waterproof material.

2.3.109. The transition of cable lines from blocks and pipes to buildings, tunnels, basements, etc., should be carried out in one of the following ways: by direct insertion of blocks and pipes into them, by constructing wells or pits inside buildings or chambers near their outer walls.

Measures should be provided to prevent water and small animals from penetrating through pipes or openings from trenches into buildings, tunnels, etc.

2.3.110. Channels of cable blocks, pipes, exit from them, as well as their connections must have a treated and cleaned surface to prevent mechanical damage to cable sheaths during pulling. At the exits of cables from blocks to cable structures and chambers, measures should be taken to prevent damage to the sheaths from abrasion and cracking (the use of elastic linings, compliance with the required bending radii, etc.).

2.3.111. With a high level of groundwater in the outdoor switchgear, preference should be given to above-ground methods of laying cables (in trays or boxes). Above-ground trays and slabs for their covering must be made of reinforced concrete. Trays must be laid on special concrete pads with a slope of at least 0.2% along the planned route in such a way as not to impede the runoff of storm water. If there are openings in the bottoms of above-ground trays that ensure the release of storm water, it is not required to create a slope.

When using cable trays for laying cables, passage through the territory of the outdoor switchgear and access to the equipment of machines and mechanisms necessary for performing repair and maintenance work should be provided. For this purpose, crossings through the trays should be arranged using reinforced concrete slabs, taking into account the load from passing vehicles, while maintaining the location of the trays at the same level. When using cable trays, it is not allowed to lay cables under roads and crossings in pipes, channels and trenches located below the trays.

The exit of cables from the trays to the control and protection cabinets must be carried out in pipes that are not buried in the ground. Laying of cable jumpers within one cell of the outdoor switchgear is allowed in a trench, and in this case, the use of pipes to protect cables when they are connected to control cabinets and relay protection is not recommended. Protection of cables from mechanical damage must be carried out in other ways (using an angle, channel, etc.).

LAYING OF CABLE LINES IN CABLE FACILITIES

2.3.112. Cable structures of all types should be carried out taking into account the possibility of additional laying of cables in the amount of 15% of the number of cables provided for by the project (replacement of cables during installation, additional laying in subsequent operation, etc.).

2.3.113. Cable floors, tunnels, galleries, flyovers and shafts must be separated from other rooms and adjacent cable structures by fireproof partitions and ceilings with a fire resistance limit of at least 0.75 hours. power and control cables and no more than 100 m in the presence of oil-filled cables. The area of ​​each compartment of a double floor should be no more than 600 m2.

Doors in cable structures and partitions with a fire resistance of 0.75 hours must have a fire resistance of at least 0.75 hours in electrical installations listed in 2.3.76, and 0.6 hours in other electrical installations.

Exits from cable structures should be provided outside or into rooms with industries of categories G and D. The number and location of exits from cable structures should be determined based on local conditions, but there should be at least two of them. With a cable structure length of not more than 25 m, it is allowed to have one exit.

The doors of cable structures must be self-closing, with sealed porches. Exit doors from cable structures must open outward and must have locks that can be unlocked from cable structures without a key, and doors between compartments must open in the direction of the nearest exit and be equipped with devices that maintain them in the closed position.

Passage cable racks with service bridges must have entrances with ladders. The distance between the entrances should be no more than 150 m. The distance from the end of the overpass to the entrance to it should not exceed 25 m.

Entrances must have doors that prevent free access to the flyovers for persons not related to the maintenance of the cable industry. Doors must have self-locking locks that can be opened without a key with inside flyovers.

The distance between the entrances to the cable gallery when laying cables not higher than 35 kV in it should be no more than 150 m, and when laying oil-filled cables - no more than 120 m.

External cable racks and galleries must have main supporting building structures (columns, beams) made of reinforced concrete with a fire resistance of at least 0.75 hours or of rolled steel with a fire resistance of at least 0.25 hours.

The supporting structures of buildings and structures that can dangerously deform or reduce the mechanical strength during combustion of groups (streams) of cables laid near these structures on external cable racks and galleries must have protection that ensures the fire resistance of the protected structures is at least 0.75 hours.

Cable galleries should be divided into compartments by fireproof fireproof partitions with a fire resistance limit of at least 0.75 hours. The length of the gallery compartments should be no more than 150 m when laying cables up to 35 kV in them and no more than 120 m when laying oil-filled cables. For external cable galleries, partially closed, these requirements do not apply.

2.3.114. In tunnels and channels, measures must be taken to prevent the ingress of process water and oil into them, and soil and storm water must be drained. The floors in them must have a slope of at least 0.5% towards water collectors or storm sewers. The passage from one section of the tunnel to another, when they are located at different levels, must be carried out using a ramp with an elevation angle of not more than 15 °. The arrangement of steps between compartments of tunnels is prohibited.

In cable channels constructed outdoors and located above the groundwater level, an earthen bottom is allowed with a draining bedding 10-15 cm thick made of compacted gravel or sand.

Drainage mechanisms should be provided in tunnels; at the same time, it is recommended to use their automatic start-up depending on the water level. Starting devices and electric motors must be of a design that allows them to work in particularly damp places.

When crossing a flyover and a walk-through gallery from one mark to another, a ramp with a slope of no more than 15 ° must be made. As an exception, stairs with a slope of 1:1 are allowed.

2.3.115. Cable channels and double floors in switchgears and rooms should be covered with removable fireproof plates. In electric machine and similar rooms, it is recommended to block the channels with corrugated steel, and in control rooms with parquet floors - with wooden panels with parquet, protected from below with asbestos and with asbestos tin. Overlapping of channels and double floors should be designed for the movement of the corresponding equipment on it.

2.3.116. Cable ducts outside buildings must be backfilled over removable slabs with a layer of earth at least 0.3 m thick. In fenced areas, backfilling cable ducts with earth over removable slabs is not necessary. The weight of an individual floor slab removed by hand must not exceed 70 kg. Plates must have a lifting device.

2.3.117. In areas where molten metal may be spilled, liquids with high temperature or substances that destroy the metal sheaths of cables, the construction of cable channels is not allowed. Manholes in collectors and tunnels are also not allowed in these areas.

2.3.118. Underground tunnels outside buildings must have a layer of earth at least 0.5 m thick on top of the ceiling.

2.3.119. When laying cables and heat pipelines together in buildings, additional air heating by a heat pipeline at the location of the cables at any time of the year should not exceed 5 ° C, for which ventilation and thermal insulation on the pipes should be provided.

1. Control cables and communication cables should be placed only under or only above power cables; however, they should be separated by a partition. At intersections and branches, it is allowed to lay control cables and communication cables above and below power cables.

2. Control cables may be laid next to power cables up to 1 kV.

4. Various groups of cables: working and reserve cables above 1 kV of generators, transformers, etc., supplying power receivers of category I, are recommended to be laid at different horizontal levels and separated by partitions.

5. Dividing partitions specified in paragraphs 1, 3 and 4 must be fireproof with a fire resistance limit of at least 0.25 hours.

When using automatic fire extinguishing using air-mechanical foam or sprayed water, the partitions specified in paragraphs 1, 3 and 4 may not be installed.

On external cable racks and in external partially closed cable galleries, the installation of dividing partitions specified in clauses 1, 3 and 4 is not required. At the same time, mutually redundant power cable lines (with the exception of lines to electrical receivers of a special group of category I) should be laid with a distance between them of at least 600 mm and it is recommended to locate: on overpasses on both sides of the span supporting structure (beams, trusses); in the galleries on opposite sides of the aisle.

2.3.121. Oil-filled cables should be laid, as a rule, in separate cable structures. It is allowed to lay them together with other cables; at the same time, oil-filled cables should be placed in the lower part of the cable structure and separated from other cables by horizontal partitions with a fire resistance limit of at least 0.75 hours. Oil-filled cable lines should be separated from one another with the same partitions.

2.3.122. 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 mm2 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 mm2 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 cross section up to 3x25 mm2, voltage 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.

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* 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

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 links, the smallest distances between cables and wires of a communication line and radio link are determined based on the calculation of the effect of cable lines on communication lines and radio link. 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 industrial enterprise should be taken from the calculation of the possibility of laying the lower row of cables at a level of at least 2.5 m from the planned ground level.

LAYING OF CABLE LINES IN PRODUCTION ROOMS

2.3.134. When laying cable lines in industrial premises, the following requirements must be met:

1. Cables must be accessible for repair, and openly laid cables for inspection.

Cables (including armored ones) located in places where mechanisms, equipment, cargo and transport are moved must be protected from damage in accordance with the requirements given in 2.3.15.

2. The clear distance between the cables must correspond to that given in Table. 2.3.1.

3. The distance between parallel power cables and all kinds of pipelines, as a rule, must be at least 0.5 m, and between gas pipelines and pipelines with flammable liquids - at least 1 m. At shorter distances of approach and at intersections, the cables must be protected from mechanical damage (metal pipes, casings, etc.) throughout the approach area plus 0.5 m on each side, and, if necessary, are protected from overheating.

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

Parallel laying of cables above and below oil pipelines and pipelines with flammable liquid in a vertical plane is not allowed.

2.3.135. Laying cables in the floor and interfloor ceilings should be carried out in channels or pipes; sealing cables in them tightly is not allowed. The passage of cables through ceilings and internal walls can be made in pipes or openings; after laying the cables, the gaps in the pipes and openings must be sealed with an easily pierced non-combustible material.

Laying cables in ventilation ducts is prohibited. It is allowed to cross these channels with single cables enclosed in steel pipes.

Open cable laying in stairwells is not allowed.

UNDERWATER CABLE LAYING

2.3.136. When cable lines cross rivers, canals, etc., cables should be laid mainly in areas with a bottom and banks that are little prone to erosion (crossing streams - see 2.3.46). When laying cables through rivers with an unstable channel and banks subject to erosion, the burial of cables into the bottom should be done taking into account local conditions. The cable laying depth is determined by the project. Laying cables in the areas of piers, berths, harbors, ferry crossings, as well as regular winter moorings of ships and barges is not recommended.

2.3.137. When laying cable lines in the sea, data on the depth, speed and style of water movement at the crossing point, prevailing winds, the profile and chemical composition of the bottom, and the chemical composition of water should be taken into account.

2.3.138. Cable lines should be laid along the bottom in such a way that they are not suspended in uneven places; sharp protrusions must be removed. Shoals, stone ridges and other underwater obstacles on the route should be bypassed or trenches or passages should be provided in them.

2.3.139. When cable lines cross rivers, canals, etc., cables, as a rule, must be buried in the bottom to a depth of at least 1 m in coastal and shallow water areas, as well as on shipping and rafting routes; 2 m when crossing oil-filled cable lines.

In reservoirs where dredging works are periodically carried out, cables are buried in the bottom to a mark determined in agreement with water transport organizations.

When laying oil-filled cable lines 110-220 kV on navigable rivers and canals, in order to protect them from mechanical damage, it is recommended to fill trenches with sandbags, followed by throwing stones.

2.3.140. The distance between cables buried in the bottom of rivers, canals, etc. with a reservoir width of up to 100 m, is recommended to be at least 0.25 m. Newly constructed underwater cable lines should be laid at a distance of at least 1.25 depth from existing cable lines reservoir, calculated for the long-term average water level.

When laying low-pressure cables in water at a depth of 5-15 m and at a flow velocity not exceeding 1 m/s, it is recommended to take the distances between the individual phases (without special fastenings of the phases to each other) at least 0.5 m, and the distances between the extreme cables of parallel lines - at least 5 m.

With underwater laying at a depth of more than 15 m, as well as at flow rates of more than 1 m/s, the distances between individual phases and lines are taken in accordance with the project.

When oil-filled cable lines and lines up to 35 kV are laid in parallel under water, the horizontal distance between them in the light must be at least 1.25 times the depth calculated for the long-term average water level, but not less than 20 m.

The horizontal distance from cables buried in the bottom of rivers, canals and other water bodies to pipelines (oil pipelines, gas pipelines, etc.) should be determined by the project depending on the type of dredging performed when laying pipelines and cables, and be at least 50 m. It is allowed to reduce this distance to 15 m in agreement with the organizations in charge of cable lines and pipelines.

2.3.141. On shores without improved embankments, at the place of the underwater cable crossing, a reserve of at least 10 m in length for river and 30 m for sea laying, which is laid in a figure of eight, should be provided. On improved embankments, cables should be laid in pipes. In the place where the cables exit, as a rule, cable wells should be arranged. The upper end of the pipe must enter the coastal well, and the lower end must be at a depth of at least 1 m from the lowest water level. Onshore sections of the pipe must be firmly sealed.

2.3.142. In places where the channel and banks are subject to erosion, it is necessary to take measures against the exposure of cables during ice drifts and floods by strengthening the banks (paving, breaking dams, piles, sheet piles, slabs, etc.).

2.3.143. Crossing of cables under water is prohibited.

2.3.144. Underwater cable crossings must be marked on the shores with signal signs in accordance with the current rules for navigation along inland navigation routes and sea straits.

2.3.145. When laying three or more cables up to 35 kV in water, one backup cable should be provided for every three working ones. When laying oil-filled cable lines in water from single-phase cables, a reserve must be provided: for one line - one phase, for two lines - two phases, for three or more - according to the project, but not less than two phases. Reserve phases must be laid in such a way that they can be used to replace any of the active working phases.

LAYING OF CABLE LINES IN SPECIAL FACILITIES

2.3.146. Laying of cable lines on stone, reinforced concrete and metal bridges should be carried out under the pedestrian part of the bridge in channels or in fireproof pipes separate for each cable; it is necessary to provide measures to prevent the runoff of storm water through these pipes. On metal and reinforced concrete bridges and when approaching them, cables are recommended to be laid in asbestos-cement pipes. In places of transition from bridge structures to the ground, cables are also recommended to be laid in asbestos-cement pipes.

All underground cables when passing through metal and reinforced concrete bridges must be electrically isolated from the metal parts of the bridge.

2.3.147. Laying cable lines on wooden structures (bridges, piers, piers, etc.) should be carried out in steel pipes.

2.3.148. In places where cables pass through the expansion joints of bridges and from bridge structures to abutments, measures must be taken to prevent the occurrence of mechanical stresses in the cables.

2.3.149. Laying cable lines along dams, dams, piers and berths directly in an earthen trench is allowed with a thickness of the earth layer of at least 1 m.

When transmitting large powers, it is not always possible to get by with one cable, and we are forced to lay several parallel cables. This design solution is not very good compared to the operation of a single cable.

Previously, I had several times to provide for two parallel cables. At the same time, I connected them to one circuit breaker. If I had to make such a decision now, I would do it very differently.

Why is it dangerous to connect several parallel cables to one machine?

In normal mode, the entire load is distributed equally between all cables. In this case, the cable lines must be of the same cross section and the same length. Let's imagine such a situation. For some reason, one cable fails. Of course, not as a result of a short circuit current, since the machine will disconnect the line. The load from the damaged cable is redistributed to other cables, and thus they themselves are overloaded and fail.

How can parallel cables be protected?

Let's consider two options:

• two parallel cables;
• three parallel cables.

The first thing to do is to install a protective circuit breaker on each cable. In this case, the rated current of the machine must be less than the permissible cable current.

But, I think this solution is not enough. Why wait for other cables to overload? Other circuit breakers must be turned off immediately.

For example, circuit breakers of the BA88 series allow you to install additional devices such as a shunt trip and an emergency contact.

The emergency contact signals us about the state of the circuit breaker and sends a command to operate the shunt release.

The algorithm of this scheme:

Circuit breaker #1 tripped -> emergency contact #1 switched -> shunt release tripped (#2, #3)

The only difficulty may arise when turning on the circuit breakers. In this regard, the protection scheme of three parallel cables is more practical. When turned on, the circuit breaker is turned on last. In the first scheme, the machines must be turned on simultaneously.

How electrical cables are laid, we recommend that you read the second section of the PUE 6. The "outdated" version. The provisions listed in the document are advisory in nature. Those who comply with the requirements for laying electrical cables will certainly avoid violations. The information is presented within one document, it remains only to read. Let's see how the laying of power electrical cables.

How and where to lay the cable

First look at the end of PUE 6, it will dispel doubts: an endless list of approvals will convince readers: it was not a silly letter, a real document that has seen the hands of many builders and officials. New requirements may appear, but given that humanity is just overcoming the Stone Age, it’s enough not to slide into the Paleozoic. PUE 6 electrical lines classifies:

1. The first part considers the types of electrical wiring, choice, typical conditions: premises, street, attic.
2. Lines with voltages below 35 kW (separately before/after 1 kV).
3. Lines with voltages below 220 kV (including cables up to 35 kV).
4. Overhead cable lines (up to/above 1 kV).

The first discusses PUE 6 (section 2) the scope. The following requirements must be met for cables with a cross section of phase conductors up to 16 square millimeters. Unfortunately, omitted, take copper or aluminum. We conclude: always good until proven otherwise. Consider first the classification of electrical wiring:

• By the nature of the occurrence:
  1. Open. It happens stationary, portable, mobile. It is laid outdoors along the surfaces of structures, between supports. Along the way, insulators, rollers, pipes, boxes, sleeves, baseboards, poles are used.
  2. Closed. It is laid inside the walls: hidden with plaster, strobes, inside concrete (walls, floor, ceiling) as a monolith, using cavities.
• External wiring is laid along the outer walls. Suspended length no more than 100 meters (four spans of 25 meters each). Other concerns overhead lines, underground routes.

It is allowed to lay an electric cable in the bathroom floor. Another question concerns the protective measures envisaged (grounded grid). The matter is limited to trifles.

Laying wires inside buildings

Among the general requirements, the inadmissibility of laying a number of voltage circuits up to / above 42 volts is indicated, with rare exceptions (see clause 2.1.16). It is relevant to today's reality, when I wanted to light the bathroom without restrictions with constant 12 volts. Fortunately, the DIN-rail adapter is sold for 800 rubles. It turns out that it is forbidden to merge in one branch. Make a house wiring from 12 volts. Safe, allows the use of a minimum cross-section of wiring.

PUE 6 gives the answer here: use fireproof partition walls between the wires. Much more interesting will be the requirement of joint following of phase, zero (return) wires (it is forbidden to use adjacent pipes). Villagers should know: the cable is not laid in combustible cavities, niches of wooden walls. Many use ceramic insulator rollers (the distance to the plane is over 10 mm, or by laying fireproof material).

With open laying, the distance from the floor is at least 2.5 meters. We bet that in private houses the villagers do not comply with the requirement. For hazardous areas only. They are not required to reduce the voltage, fitting into the upper limit of 42 volts, placing the electric cable for internal installation at a height of two meters. But it can be done. Remember the 12 volt adapter, put in switchboard. The purpose of lighting is definitely enough to supply a village house. With regard to sockets, a protected gasket (cable channels) should be used. With a degree of protection of the box IP20 and above, the height is not standardized. Connections are allowed in the form:

• crimping;
• terminal blocks;
• welding;
• soldering.

By the way, bare twists are prohibited even for ground circuits. Joint insulation is not worse than linear sections. Next come the obvious requirements: the absence of tension, the availability of nodes, connections (for service specialists). Under the cladding, a cable protected from combustion should be laid: many installers forgot. YouTube will give out as many plots as you like: the lining of PVC panels hides the traditional PVA for several cores. The mentioned part of the PUE is inactive, the installation process itself does not become less dangerous. Draw your own conclusions: we build for state inspectors, officials by and large do not care about the consequences (they must comply with the letter of the law), we do it for ourselves (so that nothing is guaranteed to happen).

Thus, laying an electric cable in a wooden house is a fine art. Useful aluminum corrugation. It is clear that plastic is not always suitable for reasons of lack of fire resistance. Take comfort: the aluminum corrugation is easy to ground, certainly improving the electromagnetic environment of the house, simplifying the replacement of wiring, saving against fire. Like other metal parts of the building, sleeves, pipes, cable channels are zeroed. Able to serve as a screen. Read more about the standards for laying an electric cable in Table. 2.1.3 PUE 6, according to the peculiarities of laying in various climatic conditions (heat, dampness), many rules are prescribed in section 2.1.

Increased attention is paid to pipeline intersections. The laying of the electrical cable is carried out, leaving a gap of at least 5 cm. If the water in the pipeline is hot, or something flammable (read, gas), the distance doubles. Moreover, protection of 25 cm against mechanical damage should be provided on each side of the intersection. On a parallel line from a pipeline, cable, the distance is taken at least 10 or 40 cm, depending on the content (gas, kerosene, hot water, steam).

Outdoor wiring of the building

Rules for laying outdoor wiring

Finally, the color coding of the electric cable for outdoor installation from the substation will be a curiosity:

1. Yellow - phase A.
2. Green - phase B.
3. Red - phase C.
4. Blue - zero working wire.
5. With yellow and green stripes - zero protective wire.
6. The reserve tire is marked with transverse stripes to the main ones.

The coloring differs from PVA cables (slightly), not intended to pull three-phase lines. The laying of an electric cable in the ground in the country is carried out by other types. Pipe marking is in accordance with GOST R IEC 61386.24, GOST 16442 will tell you examples of cables. The last document will indicate which brand of electric cable is unsuitable for laying in the ground. The subtleties of installation are indicated by PUE 6, starting from clause 2.3.83. It is said that the cable line lies no closer than 0.7 meters to the surface. From below, backfilling is performed (sand, crushed stone), from above it is slightly covered with soil, free from various kinds of debris.

Selection of the wiring section (cable cores)

According to PUE 6, the cable is divided into two categories by the cross-sectional size of the cores:

• Within 6 square millimeters for copper, 10 for aluminum is selected from tables 1.3.4 and 1.3.5 directly. As for long-term operation.
• Otherwise, when the core thickness is higher, the table current must be multiplied by a correction factor of 0.875 / √ TPV. Where TPV is the relative duration of equipment activity in the operating cycle. Simply put, the equipment works less for a period of time, it is thinner to take a core.

Please note that the figures indicated in the table are widely cited in the literature without indicating the source. PUE 6 says: the maximum continuous current of the core is determined by the type of cable (the number of conductors in insulation), the laying method discussed above. By grouping the data, readers can easily choose an electrical cable for laying over the air, underground. It's nice that the parameters are graded according to the type of insulation, voltage. There is not enough space to call the information exhaustive, some of which are withdrawn from official circulation by the current legislation.

It became difficult to find the requirements for the cross-section of the neutral conductor of the cable three-phase network. PUE 6 directly says: it should be at least 50% of the phase, sometimes it increases to 100%. Correction factors for selecting the limiting current depending on the ambient temperature will seem useful. You will see, depending on the conditions, the cable cross-section can be reduced, or, conversely, it will have to be increased. Correction factors are entered for soil type. It is important for those who want to lay the track correctly.

Many readers will like table 2.1.1, indicating the smallest cross-sections of conductors for copper and aluminum. For stationary cable laying on rollers indoors, the value is at least 1 square millimeter of copper. The current can reach 17 A (PVC cords with PVC insulation), approximately 3.7 kW of power. wanted LED lamp connect with a thinner section - it is impossible. We assume that PUE 6 came out long before the appearance of home versions of sources in our area. Surely the engineers will have to revise the measurements, make adjustments for the type of light bulbs.

cable blocks

The allowable current of cable blocks is widely discussed depending on the structure. The laying process is described in section 2.3 (now removed). It is said that cast-iron, concrete, asbestos-cement pipes are suitable for a cable block. Calculation of the number of channels, structuring is carried out in accordance with clause 1.3.20, and 15% (at least 1 piece) is reserved for the reserve (in case an additional line is needed).

The depth of the cable blocks is selected in accordance with clause 2.3.84. In most cases, it is 0.7 - 1 meter. There are assumptions to reduce the distance to half a meter on a section of no more than 5 meters. It will allow you to correctly lay the channels, which should have a slope of 0.2% towards the wells (the depth is growing). When laying, we take into account: the minimum distance between the lines is determined by the voltage, it grows with increasing.

The definition of cable blocks is hushed up, so readers probably have a question the size of a mountain. Meanwhile, the structures are formed by channels of various kinds connecting the wells. Due to the structure, the underground laying of an electrical cable is carried out without the involvement of construction equipment. Most importantly, there is no need to open expensive coatings. We bet there's some sort of cable conduit under the Piazza.

A similar technology helps cable laying under the riverbed. A special unit drills an arc-shaped tunnel in the ground, overlooking the opposite bank. The cable is laid inside. If necessary, the walls, of course, are reinforced. It makes it possible in the future to freely repair a section of the route, change certain veins (add, replace, remove). It is clear that underwater types of cable laying are not available to most private traders, you need to know in case you need to go through a difficult section.

Conclusion

We remind you that the specified PUE 6 is "outdated". You can still be guided while doing the work. Simply put, atheists say: there is no God, the Lord cares little about what is said. Similarly, the laying of an electrical cable in an apartment is carried out in accordance with documents marked by the trust of professionals.

Typically, cables in a trench are laid in one row at established distances from buildings and structures. The smallest distance between the cables and the oil or gas pipeline is at least 0.5 m. At intersections, cables up to 1 kV are laid over cables of higher voltage, since the probability of damage in cables up to 1 kV is greater and with such placement in case of accidents in cables up to 1 kV will not damage higher voltage cables. When crossing cables with other cable lines, there must be a layer of soil between them with a thickness of at least 500 mm. If this distance cannot be observed, then concrete slabs (bricks) are laid between cables up to 35 kV or the cable is placed in a pipe or corrugated hose. Bricks or a concrete slab are laid on a layer of earth with a thickness of at least 150 mm, which is poured over the cables. When crossing railways and highways, cables are laid in tunnels, blocks or pipes across the entire width of the exclusion zone at a distance of at least 1 m from the roadbed and at least 0.5 m from the bottom of the drainage ditch.
Asbestos-cement, plastic, concrete, ceramic, cast iron and corrugated plastic pipes should be used to protect cables at intersections and approaches with obstacles. The use of steel pipes is allowed only for passages made by piercing the soil. To prevent the accumulation of water in the pipes, they should be laid with a slope of at least 0.2%. The inner diameter of pipes longer than 5 m must be at least one and a half times the outer diameter of the cable, but not less than 100 mm. It is not allowed to leave the cable laid in the trench unattended if it is not sprinkled with earth and is not protected by slabs or bricks. Cables intended for voltages above 1000 V must, with rare exceptions, be closed on top with red gapless bricks or special plates. The route of each line must be plotted on the terrain plan.
When crossing streets, squares, highways and railways, the laying depth is increased to 1 m. Reducing the laying depth to 0.5 m is allowed when cables are entered into the building, as well as when crossing underground structures with a line, provided that the cables are protected from mechanical damage (for example, when laying in pipes). The laying of 6-10 kV cable lines along arable land is carried out at a depth of at least 1 m, while the land above the route is used for crops.
The width of the bottom of the trench for laying power cables up to 10 kV must be at least: 300 mm - for one or two cables; 400 mm - for two or three cables; 500 mm - for three or four cables; 630 mm for four to five cables and 800 mm for five to six cables. In the case of excavation of a trench by an earthmoving mechanism, it is allowed to reduce the width of the trench for laying one cable up to 10 kV to the width of the cutter, but not less than 150 mm. Failure to observe the distances between the cables causes unacceptable heating during their operation, which can cause the cables to fail.
At the corners, they dig a trench so that when the cables are bent, their insulation is not damaged. Cables in an aluminum sheath, especially large cross-sections, are quite difficult to bend to the required radius; To do this, use a special device similar to a manual pipe bender.

Dimensions of cable trenches and placement of cables in them with brick protection from mechanical damage: a - one, b - two, c - three, d - four, e - five
Cable laying at the intersections of roads and railways is carried out in an open way (digging a trench) or in a closed way (puncture, horizontal drilling). Soil puncture for the passage of cables under structures without digging an open trench is carried out using horizontal drilling, punching or a D-4601 type pneumatic punch.
The trench before laying the cable should be inspected to identify places on the route containing substances that have a destructive effect on the metal cover and cable sheath (salt marshes, lime, water, bulk soil containing slag or construction waste, areas located closer than 2 m from cesspools and garbage pits, etc.). If it is impossible to bypass these places, the cable must be laid in clean neutral ground.
When laying cables in the ground and water, it is necessary to take into account the estimated ambient temperatures, which are given in Table.
Estimated ambient temperatures

When laying in the ground in parallel with other operated cables or utilities near buildings and structures, clear distances must be observed (at least):

1. between cables up to 10 kV - 0.1 m (the same distance with parallel laying of newly laid cables);
2. from 35 kV cables - 0.25 m (Fig. 6);
3. from cables operated by other organizations, and communication cables - 0.5 m (Fig. 7);
4. from tree trunks - 2 m and from shrub plantings - 0.75 m (Fig. 8);
5. from the foundations of buildings and structures - 0.6 m (Fig. 9);
6. from pipelines, water supply, sewerage, drainage, low and medium pressure gas pipelines - 1 m (Fig. 0);
7. from high pressure gas pipelines and heat pipelines - 2 m (Fig. 1);
8. from the electrified railway - 10.75 m (Fig. 2); -
9. from tram tracks - 2.75 m (Fig. 3);
10. from the highway, from the edge - 1 m
11. from the curb stone - 1.5 m (Fig. 4);
12. from the extreme wire of the 110 kV overhead line - 10 m (Fig. 5);
13. from the support VL 1 kV - 1m (Fig. 6);

It is allowed to reduce the listed distances in cramped conditions, but this must be specified in the project and measures must be taken to protect cables in pipes or blocks. When crossing other cable lines or utilities and structures, clear distances must be at least:

1. from cables with voltage up to 10 kV - 0.25 m (Fig. 7);
2. from pipelines, heat pipelines, gas pipelines - 0.5 m (Fig. 8);

From the canvas of railways, tram tracks, highways - 0.6 m.

Rice. 9. Laying cables near the foundation of the building and structures:
1 - cable 1-10 kV; 2 - foundation

Rice. 6. Laying cables 1-10 kV in parallel with cables 35 kV (20 kV): 1 - cable 20 kV; 2 - cable 35 kV; 3 - cable 10 kV; 4 - sand; 5 - reinforced concrete slabs
Note. The distance between cables operated by different organizations must be at least 500 mm. If the required distance cannot be maintained, partitions made of non-combustible materials (brick, concrete) are installed between the cables or one of the cables is laid in a pipe in the area of ​​inaccessible proximity

Rice. 10. Laying cables parallel to pipelines, water pipes, sewerage, drainage, low and medium pressure gas pipelines
1 - pipeline; 2 - cable 1-10 kV

Rice. 7. Laying cables 1-10 kV with communication cables and power cables up to 10 kV operated by other organizations: 1 - 10 kV cable; 2 - cable 1 kV; 3 - communication cable or power cable of another organization; 4- sand;
1 - tray; 2 - cable 1-10 kV

Fig.2. Laying cables in parallel with the electrified railway: 1 - cable 1-10 kV; 2 - rail head
5 - bricks or slabs

Rice. 8. Laying cables near shrubs and trees: 1 - cable 1-10kV



Note. When laying cables near the supports of VL220 kV and above, the distance to them is taken according to the design of the cable line or according to the design of the overhead line (depending on which line was built later).
Rice. 7. Crossing of cable routes with voltage up to 10 kV: 1 - cable up to 10 kV; 2 - bricks
Rice. 6. Laying cables next to an overhead power line up to 1 kV: 1 - overhead line support; 2 - cable 1-10 kV
Rice. 5. Laying cables next to an overhead power line with a voltage of 110 kV: 1 - overhead line support; 2 - cable 1-10 kV.

Rice. 8. Crossing of cables with water and gas pipelines: 1 - cable up to 10 kV; 2 - pipeline

Rice. 4. Laying cables parallel to the road: 1 - roadbed; 2 - curbstone: 3 - cable 1-10 kV

Fig.3. Cable laying in parallel with tram tracks: 1 - rail head; 2 - cable 1-10 kV.

When laying cables on bridges, it is necessary to use cables in an aluminum or plastic sheath, under the pedestrian part of the bridges - in pipes made of fireproof material. The cables must be electrically isolated from the metal parts of the bridges.
On the cables at the points of transition through the expansion joints of bridges and with the structure of bridges, compensators in the form of a semicircle must be made on the abutments.
In case of difficult descents from bridges to abutments, the design organization should develop sketches for difficult places.
For underwater laying, cables with round and flat armor are used. Installation of couplings in water is prohibited, i.e. when crossing rivers, it is necessary to lay a cable of the same construction length.
Underwater cable laying should be carried out by a specialized installation organization according to a previously agreed project for the production of works.
When laying cables in places where the soil is subject to displacement (including in bulk soils), the cables must have wire armor.
At the turning points, the branching of the cables of the trench is performed so that the bending radius of the cables is not less than the permissible one (Fig. 9).
On slopes from 20 to 50 °, cables are laid in trenches with the cable fastened to reinforced concrete piles.
On fig. 10 shows an example of cable laying on slopes. Distance A between fastenings should be no more than 15 m for flat tape armored cables and 50 m for wire armored cables. Dimension H does not exceed the largest permissible level differences for cables. The places where the cables are attached to the slab are filled with bituminous mass. Instead of reinforced concrete piles, poles made of coniferous wood treated with an antiseptic composition can be used.



Rice. 9. Rotation and branching of cable routes: a - rotation of cables; b - branching of cables; c - cable branch

Rice. 10. Cable fastening on slopes eroded by showers and melt waters with a slope of 20 to 50 °: 1 - sagging soil or sand; 2 - brick or slabs; 3 - reinforced concrete pile; 4 - asbestos-cement slab; 5 - bracket for attaching the cable

Cables are laid with a margin of 1 ... 2% ("snake") of its length to exclude the possibility of dangerous mechanical stresses during soil displacement and temperature deformations, especially in spring when the earth thaws. Laying the cable with a "snake" when laying with the help of mechanisms is carried out in the process of transferring it from the rollers to the bottom of the trench.
After inspecting the cable route by a representative of the operating organization, it is allowed to backfill the cable with sand or fine earth that does not contain stones, construction debris and slag.
In the event that the project provides for the protection of cables with red clay bricks or asbestos-cement slabs, then the powder over the cable must be at least 100 mm. When laying a signal-warning tape over the cables, which should also be indicated in the project, the powder must be at least 300 mm, i.e. the tape must be at a depth of 400 mm from the planning mark. A smaller depth of tape laying is allowed in sections up to 5 m long when the cable is entered into the building, as well as at intersections with underground structures and communications, provided that the cables are protected from mechanical damage (in pipes, reinforced concrete slabs). In these cases, the tape must be inserted 300 mm into the pipe or under the slab on each side of the intersection.
The warning and warning tape made of polyvinylchloride compound must be red in color, 0.5 ... 1 mm thick and at least 150 mm wide. One tape can be laid over two cables.
With a larger number of cables, it is necessary to lay an additional number of tapes in such a way that the edges of the tape close the cable, taking into account the "snake".
After powdering the cables and laying bricks (slabs) or warning tape, representatives of the construction and electrical installation organizations, together with representatives of the operating organization, draw up an act for hidden work, which is an official document authorizing the filling of trenches with soil. Backfilling of tracks without the specified document is prohibited. Backfilling of the tracks is carried out immediately after the signing of the act.
The final backfilling of the pits must be carried out after the installation of the couplings and testing the cable line with increased voltage.
It is forbidden to backfill trenches with soil containing stones, metal waste, etc.

Page 12 of 18

in the ground

In the ground - a trench 1-20 kV power cables are laid at a depth of 0.7 m, and 35 kV - 1 m from the planning mark of the earth's surface and are placed closer to the buildings in the sidewalk zone. The shallow occurrence of power cable lines laid in the ground, their accessibility are often the cause of mechanical damage during earthworks. The protection of electric power cables from mechanical damage is carried out with reinforced concrete slabs for 20-35 kV cables throughout, and for cables up to 10 kV - with bricks or slabs, while cables with voltages above 1000 V are protected throughout, and cables up to 1000 V - only in places of frequent excavations.

Rice. 21. Parallel laying of power cables up to 10 kV together with control cables.
1 - power cable up to 10 kV; 2 - control cables; 3 - soft soil or sand; 4 - brick or reinforced concrete slabs.
With parallel laying of cable lines up to 10 kV, the distance between them horizontally in the light, as well as between them and the control cables, is assumed to be at least 100 mm (Fig. 21).
When laying cable lines with voltages above 10 kV and up to 35 kV inclusive, the distance between them and other cables must be at least 250 mm. The given distances are the minimum in terms of mutual heating and the possibility of arc damage in case of damage.
The clear distance between power cables and communication cables, as well as between cables operated by different organizations, is set at least 500 mm. If, under local conditions, the required distances cannot be maintained, then by agreement between the operating organizations, these distances can be reduced to 100 mm, and between power cables with voltage up to 10 kV and communication cables (except for cables with a circuit sealed by high-frequency telephony systems) up to 250 mm provided that the cables are protected from arc damage. Protection
Parallelly laid cables from damage by an electric arc in the event of a short circuit in the power cable is carried out by installing fireproof partitions between the cables.
The distance between the cable and the body of the cable line couplings is set at 250 mm. If this distance cannot be observed, it is necessary to take measures to protect the cables closest to the coupling from damage (for example, installing a fireproof partition between the cable and the coupling, deepening the couplings, etc.).
When laying cables along buildings parallel to the building line, the distance from the foundations of buildings to the nearest cable is set at least 600 mm.
According to the conditions of the minimum number of intersections, power cables laid along buildings are located in the following sequence from the building line: distribution line cable with voltage up to 1000 V, distribution line cable with voltage above 1000 V, supply line cable over 1000 V. Cable laying when installing cable entries into buildings at such an arrangement of the line does not lead to the need to relocate nearby cables lying in the trench.
When laying cables in the zone of green spaces, the distance from tree trunks to the nearest cable, according to the conditions for ensuring the safety of green spaces, is assumed to be at least 2 m, and from shrubs - at least 1 m.
For a cable line located in parallel with a heat pipeline, the clear distance between the cable and the heat pipeline must be at least 2 m, or the heat pipeline in the entire area of ​​approach to the cable line is insulated so that the additional heating of the earth by the heat pipeline at the place where the cables pass at any time of the year does not exceed 10°C for cable lines up to 10 kV and 5°C for 35 kV lines.
When laying cables in parallel with other pipelines, the horizontal distance between the cable and the pipeline is assumed to be at least 500 mm, and with oil and gas pipelines at least 1 m. If this distance cannot be maintained due to local conditions, it can be reduced to 250 mm, at the same time, cables for protection against mechanical damage are laid in pipes throughout the approach section. Parallel laying of cables above and below pipelines (in the vertical plane) is not allowed.
When laying cables in parallel with railways, they are usually placed outside the exclusion zone of the road (Fig. 22, a). Laying cables within the exclusion zone (Fig. 22.6) is allowed only upon agreement with the organizations of the Ministry of Railways, while the distance A (Fig. 22) between the cable and the nearest rail of the railway with diesel traction is assumed to be at least 3 m, and on electrified roads - at least 10 m.

Rice. 22. Laying cable lines parallel to railways.
a - cable laying outside the right-of-way; b - cable laying in the right-of-way; c - laying the cable parallel to the tram tracks; 1 - power cable; 2- railway rail; 3- cell.
In cramped conditions, it is allowed to reduce the indicated distances, while the cables in the entire approach area must be laid in blocks or pipes. When laying a cable through electrified railways, insulating blocks or pipes are used (asbestos-cement pipes impregnated with tar or bitumen).
When laying cables in parallel with the tram tracks (Fig. 22, c), the distance from the cable to the nearest rail is set at least 2 m. In cramped conditions, this distance can be reduced, while the cables are laid in insulating blocks or pipes throughout the approach area.
Parallel to motor roads of class I (carriageway width 15 m with four lanes), as well as class II (carriageway width 7.5 m with two lanes), cables are laid from the outside of the ditch at a distance of at least
1 m from it (Fig. 23). Reducing this distance is allowed in each individual case in agreement with the relevant road administrations.
If the cable line is laid in parallel with an overhead power line (VL) with a voltage of 110 kV and higher, the distance from the cable to the vertical plane passing through the outermost wire of the line is set at least 10 m.
The clear distance from the cable line to the grounding devices of overhead transmission line supports with voltages over 1000 V is assumed to be at least 10 m. The distance to the line supports with voltages up to 1000 V should be 1 m, and when laying the cable in the approach area in the pipe 0.5 m .
Crossing by cable lines of streets, areas, which, as a rule, have improved coverage, is carried out in blocks or pipes at a depth of at least 1 m. In order to reduce the length of the route, the intersection is performed perpendicular to the structure being crossed.
When cable lines cross entrances for vehicles to yards and garages, cables are laid in pipes, and when crossing dead-end industrial roads with low traffic intensity, as a rule, directly in the ground.

Rice. 23. Laying cables in parallel with highways.
1 - power cables, 2 - roadside, 3 - ditch, 4 - carriageway of the roadbed.
When cable lines cross railways and highways, cables are laid in tunnels, blocks or pipes across the entire width of the exclusion zone at a depth of at least 1 m from the roadbed and at least 0.5 m from the bottom of drainage ditches. In the absence of an exclusion zone, the specified method of laying is carried out only at the intersection plus 2 m on both sides of the roadbed.
When crossing electrified and subject to direct current electrification railways, cables are laid in insulating blocks or pipes. In this case, the crossing point is set at a distance of less than 10 m from the switches, crosses and points of attachment of the suction cables to the rails.
In case of transition of the cable line to the air line, the cable exit to the surface is carried out no closer than 3.5 m from the bottom of the embankment or from the edge of the web.
New cable lines laid in the ground, as a rule, intersect with existing previously laid lines, as well as with other underground structures. In places of such intersections, the cables are protected from mechanical damage and the action of an electric arc in case of its occurrence.
When crossing power cable lines between themselves, the cables higher voltage laid under low voltage cables,
At the intersections, the cables are separated by a layer of soil with a thickness of at least 500 mm (Fig. 24). If, according to local conditions, it is not possible to maintain this distance, then it is allowed to reduce it to 250 mm, provided that the cables are separated along the entire intersection plus 1 m in each direction by fireproof partitions-plates or pipe sections.
When cable lines cross pipelines, including oil and gas pipelines, the distance between the cable and the pipeline is assumed to be at least 0.5 m. It is allowed to reduce this distance to 0.25 m, provided that the cable is laid at the intersection plus 2 m in each direction in pipes.
When cable lines cross heat pipelines, the distance between the cables and the overlap of the heat pipeline in the light must be at least 0.5 m; at the same time, the heat pipeline at the intersection plus 2 m in each direction from the outermost cables is provided with such thermal insulation that the ground temperature does not rise by more than 10 ° C in relation to the highest summer temperature and by 15 ° C in relation to the lowest winter temperature (Fig. 25). In case of crossing the steam pipeline, the channel is completely backfilled with mineral wool at the intersections and plus 2 m on both sides of the outermost cables. This measure is carried out in addition to the main thermal insulation applied to the steam pipeline. In the case when the above temperatures cannot be observed, the following are allowed: cable deepening up to 0.6 m instead of 0.7 m; use of a cable insert of a larger cross section; cables are laid under the heat pipeline in pipes at a distance of at least 0.5 m from it.



Rice. 24. Mutual intersection of power cables.
a - with separation by a layer of earth; b - with their separation with brick or reinforced concrete slabs; c - with the conclusion of one group of crossed cables in a pipe; 1 - high voltage cable; 2 - low voltage cable or low current cable; 3 - soil; 4 - brick or slab; 5 - pipe.
In the cramped conditions of the city, it is not always possible to deliver the drum with the cable to the place of its installation for rolling. Usually, cable drums (preliminarily brought to the track, and temporarily left in the nearest yards and other places where they do not interfere with the movement of vehicles, pedestrians, and only by the time the cable is laid are rolled up to the trench and installed for unwinding. Rolling of cable drums should be carried out in sheathing in the direction of cable winding, indicated on the drums by an arrow so that the turns of the cable tightly wound on the drum do not loosen or unravel when rolling the drum. from boards laid along the rolling line, and provided that the cable is tightly wound on the drum, the upper end of the cable is securely fixed and the edges of the drum cheeks rise above the turns of the cable by at least 100 mm. the drum is not hit by stones, bricks and other objects that can damage the cab spruce.

Rice. 25. Crossing heat pipes with cables.
a - cables above the heat pipe; b - cables under the heat pipe; 1 - power cable; 2 - heat pipe; 3 - pipe; 4- thermal insulation.
The drum is installed in such a way that its rotation when winding the cable occurs against the direction of the arrow on the cheek of the drum. Then a steel shaft with a diameter of 60 mm is passed through the axial hole of the drum with a drum mass of up to 2500 kg, a shaft with a diameter of 70 mm with a mass of up to 3500 kg and 75 mm with a drum mass of up to 5000 kg. Screw jacks are installed under the ends of the steel shaft, with the help of which the drum is raised by 150-200 mm from the ground. The raised drum must stand firmly on its supports and rotate freely, without moving along the shaft. Carefully, so as not to damage the upper turns of the cable, remove the sheathing. The nails remaining at the end of the cheeks of the drum are removed or hammered so as to exclude the possibility of catching, damaging the cable during the rotation of the drum, as well as the hands of the workers rotating the drum.
To roll out a cable from a drum weighing up to 3 tons, it is recommended to use a drum lifter (Fig. 26), the use of which speeds up the installation of the drum.



Rice. 26. Drum lifter.
1 - drum with cable; 2 - drum lifter lever.
This design of the drum lifter compares favorably with the jacks discussed above in that it does not require retracting the drum, adjusting each of the two supports of the installation. The drum lifter is brought under the steel axle threaded through the drum, leveled and, using it as a lever, lift the drum and give it the position and direction necessary for rolling the cable.
Before laying the cable, they are preliminarily fixed, sprinkled with earth, pipes laid at the points of intersection or convergence with other underground utilities; prepare passages for entering (Laying cable into buildings through foundations and walls; remove from the trench © ode (if any), stones and level the bottom of the trench; fill 100 mm thick at the bottom of the trench with fine soft earth or mountain sand and harvest along the route fine sifted earth or mountain sand for powdering the cable after laying, prepare and stack bricks or reinforced concrete slabs along the route to protect the cable after it has been laid and powdered.
The preparation of the trench for laying the cable is drawn up by an act of acceptance for installation.
Cable laying works consist of the following technological operations, rolling the cable from the drum, laying the cable into the trench, removing the executive drawing, backfilling the cable with a layer of soft earth or sand at least 100 mm thick, laying coatings that protect the cable from mechanical damage, backfilling the trench.
When winding the cable from the drum by any of the methods described below, measures are taken to exclude the possibility of damage to the cable as a result of sticking of tightly superimposed turns of the cable to each other. When gluing adjacent coils and rapidly rotating the drum during unwinding, unacceptable bends and damage to the coil of cable unwound from the drum are possible. Therefore, the unwinding of the cable must be carried out at a minimum speed, and to regulate the speed of the drum, it is braked if necessary. Experienced workers or electricians standing at the drum observe the correct winding of the cable, the timely separation of glued adjacent turns from each other. A worker standing at the drum picks up a coil of cable descending from the drum and, in case of gluing it with adjacent coils, tears it off by force. A kink and damage to the cable when winding from the drum can also be due to falling coils as a result of improper winding (usually when rewinding) or rolling the drum with incomplete use of its capacity for a considerable distance and violating the direction of rolling (against the direction indicated by the arrow).
In this case, the coil coming off the drum may be clamped by adjacent coils that have moved from their place. The worker standing at the drum must notice this in a timely manner, eliminate the jamming, release the clamped coil, or temporarily stop the unwinding.
Cable rolling can also be carried out from a moving vehicle, pulling with a drive or manual winch on rollers, manually pulling on rollers or manually without rollers.
When rolling out a cable from a drum installed on a vehicle moving at a speed of 0.6-1 km / h, the cable is also laid in a trench at the same time. In this case, the vehicle can be a car equipped with an RKB-Z loader, a TKB-5 cable conveyor trolley towed by a car or tractor, a special cable car, as well as a car with cable jacks installed on it.



Rice. 27. Rolling cable on rollers using a winch.
1 - cable layer; 2 - roller; 3 - winch with electric drive.

During the rolling of the cable from the conveyor or vehicle, the rotation of the drum in accordance with the above must be done manually by experienced workers or fitters. Workers following the machine take the coiled cable and lay it on the bottom of the trench. The distance between the edge of the trench and the machine must be at least the depth of the trench for all soils except loam, where this distance is equal to the depth of the trench multiplied by 1.25. The method of unwinding and laying a cable from a moving vehicle is used in the field and in places where there are no other underground structures crossing the trench, and under which the coiled cable must be laid. The application of this method is also possible in the absence of obstacles to traffic along the route. In the cramped conditions of the city with its saturation with underground communications, it is impossible to use the method of unwinding and laying a cable from a moving vehicle. The disadvantages of this method are also the difficulties associated with loading the drum, installing the structure, jacks in the car body, and the irrational use of the car.
The method of rolling out the cable by pulling it with a cable using a drive or manual winch on rollers has found the greatest application. In this method, the cable drum is installed on the TKB-5 conveyor trolley or on conventional cable screw jacks at one end of the trench, and winches with a cable for pulling the cable at the other end of it.
Rollers for rolling out the cable on straight sections of the route are installed at the bottom of the trench at a distance of 3 to 5 m from each other, and corner rollers or a guide chute are installed at the turns of the route (Fig. 27). The corner rollers or the guide chute are fixed with braces so that they do not move when the cable is pulled.

Rice. 28. Clip for attaching the cable to the rope.
1 - conical asterisk with three sector recesses; 2 - body; 3 - head; 4 - traction cable; 5 - casing; 6 - cable core; 7 - cable.
When laying several cables in one trench, the rollers are installed so that they do not interfere with laying the laid cable in its place at the bottom of the trench. The bending radius of the corner rollers and guide troughs must be at least as large as the bending radius allowed for the given cable. After installing the drum with the cable, ensuring its free rotation along the pre-installed rollers, the winch steel cable is unwound, the end of which is passed through all intersections, and attached to the upper end of the cable unwound from the drum. At the ends of the pipes through which the cable is pulled (in the course of rolling), detachable mounting funnels are installed to reduce friction when the cable enters the pipe channel.
The method of connecting the cable to the outer end of the cable is determined by the tensile force and, depending on the value of this force, the connection can be made using a special wire stocking, canvas belt, and also directly behind the cores using a special clamp (Fig. 28). The permissible length of the dragged cable, at which it is possible to use a wire stocking or canvas belt, depends on the mass and cross section of the cable and is limited to a length of no more than 100 m for cable ends with a cross section of 120-185 mm 2. The wire stocking is put on the cable sheath and is firmly fixed at the end with a wire bandage along the applied resin tape over a length of at least 500 mm.

Table 4
Estimated pulling forces per 100 m of cable

Conductor cross section, mm 2				Conductor cross section, mm 2	Pulling force, kgf, at cable voltage, kV

Note. The numerator shows the tensile forces for three-core cables with aluminum conductors, and the denominator - for cables with copper conductors.
The required tensile force on the straight sections of the route depends on the mass of the cable (accepted according to the reference book for electric cables) and the coefficient of friction, i.e.
P=kq,
where P is the tensile force of the cable; q is the mass of the cable; k - coefficient of friction,
The value of the coefficient of friction when unwinding and pulling the cable is: 0.8 when pulling “on the ground (bottom of the trench); 0.25 when pulling on the rollers, when sliding on the ground is excluded, since the number of rollers is set in sufficient quantity; 0.35 when pulling on the rollers, when sliding on the ground between the rollers is not excluded; 0.03-0.04 - on ice.
Tensile forces per 100 m of cable for approximate calculations when laying heavy three-core armored cables with voltage up to 10 kV in a trench with a coefficient of 0.35 according to [L. 6] are given in Table. four.
The tensile strength of copper conductors is 26 kgf / mm, and aluminum stranded, respectively, 16 kgf / mm. The maximum allowable tensile force is taken equal to 7b of the strength of the cable cores.
The diameter of the steel cable, taking into account the tensile force for laying the cable, is selected according to the following data:

Let, for example, it is required to determine the tensile force of the construction length of 250 m of a cable with a cross section of 3X185 mm 2, voltage of 10 kV, ASB brand, laid along the rollers.
Using the formula above, substituting the values ​​of the quantities, we obtain:

where 7763 kg is the mass of 1 km of the cable length of the ASB brand with a section of 185 mm 2 and a voltage of 10 kW; 0.35 - the value of the coefficient of friction in the presence of cable sliding on the ground between the rollers.
To take into account the additional effort required when starting off (starting to move),

The obtained value of the tensile force allows you to select the diameter of the cable, equal to 7.7 mm, as well as the load capacity of the winch.
The tensile strength of three-core cables with aluminum conductors will be:
185-3-16=8880 kgf.
The maximum allowable tensile force for the cores for this cable is respectively equal to: P = 8880/6 = 1480 kgf, which, as can be seen, significantly exceeds the required tensile force P, necessary for rolling the cable we adopted on the rollers.
The choice of load capacity and winch drive for cable rolling, depending on the tensile forces and laying conditions, is made according to Table. 3.
After attaching the cable to the upper end of the cable, the drum is rolled out. Turning on the winch drive motor or rotating the winch with a manual drive, provide the necessary tensile force to unwind the cable from the drum, roll it out along the rollers and the bottom of the trench. When rolling out the cable using mechanisms, the tensile force acting on the cable is controlled using a dynamometer or other control device. With a manual drive, the winch is rotated smoothly, without jerks. The cable, which is unwound from the drum by the pull of the cable, must, without bends, freely sliding along the rollers, cross without engagement and friction other underground structures encountered on its way above the marks.
If it is necessary to pull the cable through the pipes, along with the installation of mounting funnels, measures are taken for preliminary cleaning, and, if possible, measures for purging them. With a pipe length of more than 10 m, the cable being pulled is lubricated with grease.
When unrolling a cable using a cable and winches for tension, two experienced fitters should be at the drum and monitor its unwinding. If necessary, they slow down the drum or release the coil of cable that has stuck together or is pinched by adjacent coils. A winch with a drive (electric or motor) has one worker who monitors the operation of the winch and controls the tensile force on a dynamometer. If the cable is rolled out using a manual winch, then two workers are required to rotate it and control the tensile force. An experienced worker is allocated to monitor the end of the cable being laid moving along the rollers, to direct it under the underground structures crossing the trench, as well as to communicate with the control of the winch and give a signal to stop or start the winch. The cable is rolled out at a speed of 0.6-1 km/h.
After the cable is rolled out, the winch stops, the cable is disconnected, and then the cable is removed from the rollers and transferred to its place at the bottom of the trench. The cable is laid along the entire length with a normal slack, a snake, which compensates for changes in the length of the cable caused by temperature fluctuations in the cable during operation; in this case, the length of the cable will be approximately 2-3% longer than the length of the trench. When laying several cables in a trench, their ends are positioned in such a way that the distance between the centers of the couplings (to be installed) is at least 2 m.
The method of mechanized unwinding and cable laying described above is the simplest, most reliable and therefore has great advantages over other methods, especially on straight routes and in the presence of intersections under which the cable unwound from the drum should be laid.
If it is impossible, according to local conditions, to apply the mechanisms, the rolling and laying of the cable is carried out manually. When rolling out and laying the cable manually, the drum is also installed at the end of the trench, and the cable is pulled by workers placed along the route, at the command of the foreman. The number of workers for manual laying is determined based on the load per worker no more than 35 kg. When rolling out and laying the cable, make sure that the cable is not damaged as a result of unacceptable bends, twists, and for this at all critical places: at the drum, at the places where the route turns, the cable passes through pipes, at intersections with other underground structures - experienced workers or electricians should be placed. At the cable drum, it is necessary to have a brake in the form of a board, which, if necessary, is pressed against the cheek of the drum, and experienced electricians must be supplied to regulate the speed of the drum and monitor the correct winding of the cable. When laying the cable, they ensure the consistency and simultaneity of the actions of all workers along the entire front of the work, for which it is recommended, for large installations, to have local radio installations on the route and carry out the command using a loudspeaker or telephone. The signal is also made by flags and other conditional means of signaling. The manual cable laying technology is determined depending on the width of the trench and the presence of intersections with other underground structures in it along a wide trench (at least 0.5 m) workers carry the cable, moving along the trench, and in a narrow trench workers carry the cable, moving along the edge of the trench. One of the workers takes the end of the cable, and the people placed at the drum begin to rotate the drum. At certain equal intervals of 3-5 m (depending on the mass of the cable and based on the load of not more than 35 kg), the cable is picked up by workers who carry it on their hands, preventing the cable from dragging along the ground after rolling out the entire construction length of the drum, the end of the cable is laid to the bottom of the trench by the first worker, then sequentially by the second, third, and so on, until all the cable is correctly laid on the bottom of the trench and in its place.
If there are other underground utilities crossing the trench, under which it is necessary to drag the cable, the workers are placed in the gap between two adjacent rollers, on which the cable is laid. The workers, standing still in a bent position, simultaneously and on command gradually move the cable being laid along the rollers, as shown in Figure 29, a. The method of manual unwinding and cable laying described above, when the cable drum is installed at the end of the trench, has a significant drawback, since it requires a significant number of workers, especially when laying heavy cables.
If, however, the drum with the cable to be unwound and laid is placed not at the end, but in the middle of the trench, then the required number of workers can be reduced by about 2 times. With this method of rolling and laying the cable with the installation of the drum in the middle of the trench, the cable is wound from the upper end of the drum and laid first in one side of the trench in the same way and in the same technological sequence as mentioned above, and then in the other side of the trench. In this case, the cable is wound up not from above, but from the bottom of the drum with a loop brought through the drum (Fig. 29.6). If there are underground structures under which the cable to be laid should be laid, unwind the entire cable from the drum with a loop, bring the end of the cable under the first intersection and, standing still, gradually move the cable along the rollers along the trench through all other intersections until the entire loop is selected. Cable laying using loops can only be carried out in extreme cases by a qualified team of workers with extensive experience in laying cables, since this method is most likely to damage the cable as a result of unacceptable bends, kinks and twists. With the forced application of this method, laying on hinges and turns put the most experienced disciplined workers or electricians.



Rice. 29. Cable laying without the use of mechanisms (manually).
a - unwinding the cable from the drum and moving the cable along the rollers; b - unwinding the cable from the bottom of the drum with a loop brought through the drum.
Arrangement of cable drums along the laying route and cable rolling is performed using the factory marking of the upper end of the cable, as follows. The construction lengths of the cable are laid sequentially one after the other, and the upper end of one drum is placed to the lower end of the other drum if the marking of the upper end of both drums is the same ("P" or "O"). If the upper end of one drum is marked "P", and the other "O", then the cable from these drums should be rolled out with their upper ends towards each other.
When laying the cable, they provide for a margin of cable ends along the length necessary for connection and termination, the installation of compensators that protect the coupling from damage during soil displacements, as well as temperature deformations of the cable. The cable margin in compensators, in addition, is calculated in such a way that in case it was possible to install a new coupling without the need to lay an insert and install two couplings. For cables up to 10 kV inclusive, the length of the cable margin in the compensators of the couplings can be taken equal to 350 mm (which corresponds to half the length of the coupling for the largest section of the cable 240 mm 2 type SS-110, equal to 690 mm) and for cables 20-35 kV, respectively 400 mm.
The length of the reserve required for cutting and connecting the cable is determined depending on the method of making the connection with the same conductors (of the same color) or opposite conductors (of different colors).
During the construction of power cable lines, the connection of individual building lengths of the cable to each other is usually carried out by any cores without regard to colors, and phasing in order to ensure the same phases with the switchgear busbars is carried out during the installation of the termination. The margin of the cable left at the ib ends (overlapping) when laying, depending on the connection method, is:
when connecting with any conductors of different colors

when connecting with the same conductors of the same color

where I is the pitch length of the total cable twist (mm), the value of which for power cables of large cross section is 3000 mm; 3 - the number of phases (veins) involved in the calculation of the length of the stock of each end; 2 is the number of cable ends to be connected.
When laying a cable with single-wire conductors of large cross-section (150 mm 2 and above), which has a rigid structure, it is necessary to replace this cable with a multi-core cable of normal flexibility of the same brand at the input section of the line being constructed into the building, switchgear cell.
The use of rigid cables with single-wire cores in the cramped conditions of switchgear of electrical devices is not always possible due to the small dimensions of the cells, backboards and assemblies and the difficulties that arise in connection with this when installing the termination and performing the connection.
Above, different ways of unwinding and laying a cable, as well as the reasons that cause damage to the cable, were considered.
When laying a cable with impregnated paper insulation, the most severe, irreparable type of defect in work, leading to damage to the cable throughout its construction length, is the unwinding and laying at a negative ambient temperature of a cable that has not been previously heated up in an appropriate way.
At negative temperatures below 0°C, the oil-rosin composition with which the paper insulation of the cable is impregnated loses its viscosity and lubricity. The frozen mass does not lubricate, but glues the layers of paper insulation tapes. Bending of the cable during unwinding and laying under these conditions leads to a rupture of the paper insulation, a decrease in its electrical strength and subsequent electrical breakdown after the cable line is put into operation. Therefore, laying a cable with impregnated paper insulation at temperatures below 0 ° C without preheating is not allowed. The cable can be heated in a heated room, in a special greenhouse and with electric current. The most convenient, high-quality and fastest is the method of heating the cable with electric current.
This method consists in the fact that an electric current is passed through the conductive conductors of the heated cable, the source of which is a power transformer with a power of 20 kV * A, the voltage of the primary winding is 220/380 V, the secondary - from 7 to 98 V at 10 steps. The transformer is fixed in an annular frame, which ensures the convenience of its transportation. The value of the electric current passing through the conductors of the cable is set depending on the cross section and voltage of the heated cable. The only drawback of this method is the need to break the sealing of the ends of the cable, since in order to create an electric current circuit, it is necessary to shortly connect the conductors of the inner end of the cable after cutting them, and connect the outer end to a current source - a power transformer.
After connecting the cable cores to each other, it is necessary to restore the sealing of the inner end of the cable by soldering the lead cap. The lead cap must be soldered in such a way that the shorted cores do not reach the bottom of the cap by 30-40 mm, since at a shorter distance the cap can be torn by the cable cores during its installation.
The outer end of the cable on the drum is cut under a temporary funnel and filled with bituminous mass so that the place of the insulation cut of the cores is filled with mass and is 50 mm away from the surface of the mass poured into the funnel. It must be borne in mind that after heating the cable and subsequent cooling, a vacuum is formed inside it, as a result of which intensive suction of outside air and moistening of the insulation are possible, if tightness is not created when sealing the ends of the cable. Therefore, after the end of the heating of the cable, the funnel is cut off and a lead cap is also soldered to this end of the cable.
When connecting the heating cable, make sure that the load does not exceed the maximum allowable value for a given cable section, taken from the tables of permissible loads for air, taking into account the correction factor for the air temperature during warm-up.
If several cables are laid in the trench, then several drums can be heated simultaneously from one transformer by connecting their conductive cores to each other in series and increasing the circuit voltage accordingly. If the cables to be heated have a different cross section of the cores, then the maximum allowable current for heating is selected according to the cable with a smaller cross section of the cores. When you turn on the cable for heating by ammeter, make sure that the current does not exceed the values ​​​​allowed for a given cable section. Along with monitoring the current value, monitoring of the temperature of the outer covers of the upper turns of the cable on the drum is established.
The temperature of the armor or metal sheath of the outer turns of the cable at the end of the warm-up should not exceed + 25 ° C for cables 20-35 kV, + 35 ° C for cables 6-10 kV and + 40 ° C for cables 3 kV and below. To monitor the heating temperature, a thermometer is installed on the drum between the two upper turns of the cable, the lower end of which is pressed tightly against the outer cover and insulated with felt or cotton wool. The cable is laid after the end of heating at the maximum possible speed (from 30 to 60 minutes, depending on the outdoor temperature) so that the cable does not have time to cool. In cases where the laying of the cable, carried out at a low temperature, for some reason is delayed and takes a long time, the cable is reheated before unwinding or the cable is laid “under current”.
The heated cable must be laid in a trench with a “snake”, have more slack (3%) than a similar cable laid under normal conditions (i.e. without heating), since it will stretch somewhat when it cools down.
After the cable laying is completed, they check the correct placement of the cable in the trench, in the pipe provided for crossing driveways, streets, as well as at the approaches and inputs to the switchgear of substations, compliance with the dimensions at the points of convergence and intersection of cable lines with each other, as well as with underground structures located operated by other organizations.
To draw up as-built drawings, the route for laying and entering cables into the electrical room is filmed before the trench is backfilled. In accordance with the requirements of [L. 4] for topographic and geodetic works, as-built drawings for laying the cable are signed by the surveyor who surveyed the route, representatives of the customer and the construction and installation organization. The correctness of the shooting and the compliance of the executive drawing with the nature after the control measurements and inspection are certified by technical supervision. The executive drawing of the route is included in the executive documentation submitted when the line is put into operation.
As a cable line construction project, cable laying executive drawings are made on a scale of 1: 500, and in some cases, where there are a large number of cable lines, on a scale of 1: 200 or even 1: 100. The location of each laid cable line is “tied” to permanent structures, which are usually buildings, and in areas where there are no permanent landmarks, reinforced concrete or metal poles (benchmarks) are installed at a rate of 100-150 m from each other on straight sections of the route, at all turns and at couplings.
The executive drawings also indicate the sections of the route where the cables are laid at a depth of more than 1 m and less than 0.7 m, the location of busy and standby pipes laid in connection with approaches, intersections of other underground utilities.
After checking the quality of the laying, filling the cable with a layer of soft earth or sand 100 mm thick, laying slabs or red (non-silicate) bricks to protect the laid cable from mechanical damage, an act for hidden work is drawn up, drawn up by the construction and installation organization and a representative of the operating organization. The representative of the technical supervision gives permission to backfill the trench, while controlling the quality of the backfill, the thoroughness of the soil compaction over the laid cables.
Before the cable is powdered with a layer of earth or sand, the protective plates or bricks are laid, it is not allowed to leave the cable unattended due to a break in work. The brick is laid on top of the cable bedding so that with one cable the middle of the coating is on the axis of the cable (one layer across), and with a large number of cables, a continuous flooring is made from the coating with an exit in both directions beyond the outermost cables of at least 50 mm.
Backfilling of the trench, as a rule, is carried out with earth previously taken out of the trench, provided that it does not contain clods of frozen soil, stones, construction debris, slag, etc. If the soil taken out of the trench does not meet the specified requirements, then the trench is backfilled with imported shallow earth. On well-maintained streets, city squares and in other areas with an improved road base, trenches and pits are covered with exclusively sandy soil in order to avoid subsequent subsidence after the restoration of the road surface. The final backfilling of the trench with soil and its compaction are carried out by mechanisms.