Pue 7 cable lines up to 1 sq. Requirements and prices for laying cables in the ground. Requirements for checking a line in case of current leakage

SCOPE, DEFINITIONS

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

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

2.3.3. A cable structure is a structure specifically designed to house cables, cable couplings, as well as oil-feeding devices and other equipment designed to ensure the normal operation of oil-filled cable lines. Cable structures include: cable tunnels, channels, ducts, blocks, shafts, floors, double floors, cable overpasses, galleries, chambers, feeding points.

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

A cable channel is a channel that is closed and buried (partially or completely) in the ground, floor, ceiling, etc. a non-passable structure designed to accommodate cables, the installation, inspection and repair of which can only be carried out with the ceiling removed.

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

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

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

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

A cable chamber is an underground cable structure, covered with a blind removable concrete slab, intended for laying cable couplings 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 overhead or ground-based open horizontal or inclined extended cable structure. The cable rack can be pass-through or non-pass-through.

A cable gallery is an above-ground or above-ground, fully or partially closed (for example, without side walls) horizontal or inclined extended cable passage structure.

2.3.4. It is called a box - see 2.1.10.

2.3.5. It's called a tray - see 2.1.11.

2.3.6. An oil-filled cable line of low or high pressure is a line in which the long-term permissible excess pressure is:

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

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

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

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

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

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

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

GENERAL REQUIREMENTS

2.3.11. The design and construction of cable lines must 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 installation method, cable designs, etc.

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

2.3.13. Above underground cable lines in accordance with current security regulations electrical networks Security zones should be installed in the size of the area above the cables:

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

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

For submarine cable lines up to and above 1 kV, in accordance with the specified rules, a security zone must 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 cable line route should be selected taking into account the lowest cable consumption, ensuring its safety under mechanical stress, providing protection from corrosion, vibration, overheating and damage to adjacent cables electric arc when a short circuit occurs 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 feed tanks on the line.

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

cables must be laid with a reserve length sufficient to compensate for possible soil displacements and temperature deformations of the cables themselves and the structures along which they are laid; It is prohibited to lay cable reserves in the form of rings (turns);

cables laid horizontally along structures, walls, ceilings, etc. must be rigidly secured at the end points, directly at the end seals, on both sides of bends and at connecting and locking couplings;

cables laid vertically along structures and walls must be secured in such a way that deformation of the shells is prevented and the connections of the cores in the couplings are not broken under the influence of the cables’ own weight;

structures on which unarmored cables are laid must be made in such a way that the possibility of mechanical damage to the cable sheaths is excluded; in places of rigid fastening, the sheaths of these cables must be protected from mechanical damage and corrosion using elastic gaskets;

cables (including armored ones) located in places where mechanical damage is possible (movement of vehicles, machinery and cargo, accessibility to 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 near other cables in operation, measures must be taken to prevent damage to the latter;

cables must be laid at a distance from heated surfaces that prevents heating of the cables above the permissible level, while protection of the cables from the breakthrough of hot substances in the places where valves and flange connections are installed must be provided.

2.3.16. Protection of cable lines from stray currents and soil corrosion must meet the requirements of these Rules and SNiP 3.04.03-85 “Protection of building structures and structures from corrosion” of the Gosstroy of Russia.

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

2.3.18. Cable structures and structures on which cables are laid must be made of fireproof materials. It is prohibited to install any temporary devices in cable structures or 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 effect of solar radiation, as well as heat radiation from various types of heat sources. When laying cables at a latitude of more than 65°, protection from solar radiation is not required.

2.3.20. The radii of the internal bending curve of cables must have a multiple of at least those specified in the standards or technical specifications for the corresponding brands of cables in relation to their outer diameter.

2.3.21. The radii of the internal bending curve of the cable cores when performing cable terminations must have, in relation to the given diameter of the cores, a multiple of not less than those specified in the standards or technical specifications for the corresponding brands of cables.

2.3.22. Tensile forces when laying cables and pulling them in pipes are determined by the mechanical stresses permissible for cores and sheaths.

2.3.23. Each cable line must have its own number or name. If a 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 terminations, must be equipped with tags indicating the brand, voltage, cross-section, number or name of the line on the tags of the cables and terminations; on the coupling tags - coupling numbers and installation dates. Tags must be resistant to environmental influences. On cables laid in cable structures, tags must be located along the length at least every 50 m.

2.3.24. Identification signs must be installed on the cable line route laid in undeveloped areas. The route of a cable line laid across arable land must be marked with signs installed at least every 500 m, as well as in places where the direction of the route changes.

SELECTION 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 in one trench. If there are a larger number of cables, it is recommended to lay them in separate trenches with a distance between groups of cables of at least 0.5 m or in channels, tunnels, overpasses and galleries.

2. Laying cables in tunnels, along 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 very tight spaces along the route, at intersections with railway tracks and driveways, when there is a possibility of a metal spill, etc.

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

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

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

2.3.28. In the areas of substations and distribution facilities, cable lines must 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 impassable parts of streets (under sidewalks), along courtyards and technical strips in the form of lawns.

2.3.30. In streets and squares saturated with underground communications, it is recommended to lay 10 or more cable lines in a stream in collectors and cable tunnels. When crossing streets and squares with improved surfaces and 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 the active layer in dry, well-draining soils, in artificial embankments made of coarse dry imported soils, in trays on the surface of the ground, on overpasses. It is recommended to jointly lay cables with pipelines for heating, water supply, sewerage, etc. in special structures (collectors).

2.3.32. The implementation of different 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 (rock, pebble, gravel, crushed stone and coarse sand); heaving and subsidence soils are unsuitable for laying cable lines in them. Cables can be laid directly in the ground if the number of cables is no more than four. Due to soil, permafrost and climatic conditions, laying cables in pipes laid in the ground is prohibited. At intersections with other cable lines, roads and underground communications, cables should be protected with reinforced concrete slabs.

Laying cables near buildings is not permitted. 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 may be used in places where the active layer consists of non-heaving soils and has a flat surface with a slope of no more than 0.2%, ensuring surface water drainage. Cable ducts should be made of waterproof reinforced concrete and covered on the outside with reliable waterproofing. The channels must be covered from above with reinforced concrete slabs. Channels can be made buried in the ground or without burial (on top of the ground). In the latter case, a cushion with a thickness of at least 0.5 m of dry soil must be made under the channel and near it.

2.3.33. Inside buildings, cable lines can be laid directly along building structures (open and in boxes or pipes), in channels, blocks, tunnels, pipes laid in floors and ceilings, as well as along machine foundations, in shafts, 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 method of laying them is determined by the project.

CABLE SELECTION

2.3.35. For cable lines laid along routes passing in different soils and environmental conditions, the choice of cable designs and sections should be made along the section with the most severe conditions, if the length of sections with easier conditions does not exceed the construction length of the cable. If there are significant lengths 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, cable sections must be selected according to 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 underwater, to use cables of different sections, but no more than three, provided that the length of the shortest segment is at least 20 m (see also 2.3.70 ).

2.3.37. For cable lines laid in land or water, armored cables should be used predominantly. The metal sheaths of these cables must have an outer covering to protect them from chemical attack. Cables with other designs of external protective coatings (unarmoured) must have the necessary resistance to mechanical stress when laid 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 oil-filled high-pressure cable lines laid in the ground or water must be protected against corrosion in accordance with the design.

2.3.39. In cable structures and production 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 should be used or protected from mechanical damage.

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

For mixed installation (ground - cable structure or industrial premises), it is recommended to use the same brands of cables as for installation in the ground (see. 2.3.37 ), but without flammable 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 coverings made of flammable materials on top of the armor, and unarmored cables on top of metal sheaths.

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

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

When laying in rooms with an aggressive environment, cables that are 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-flammable coating. At power plants, the use of cables with flammable polyethylene insulation is not allowed.

2.3.42. For cable lines laid in cable blocks and pipes, as a rule, unarmored cables in a reinforced lead 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 covering of cable yarn. For cable lines laid in pipes, the use of cables in a plastic or rubber sheath is allowed.

2.3.43. For laying in soils containing substances that have a destructive effect on cable sheaths (salt marshes, swamps, bulk soil with slag and building materials, etc.), as well as in areas dangerous due to the effects of electrocorrosion, cables with lead sheaths must be used and reinforced protective covers of types B l, B 2l or cables with aluminum sheaths and especially reinforced protective covers of types B v, B p (in a continuous moisture-resistant plastic hose).

2.3.44. Where cable lines cross swamps, cables must be selected taking into account geological conditions, as well as chemical and mechanical influences.

2.3.45. For installation in soils subject to displacement, cables with wire armor must be used or measures must be taken to eliminate the forces acting on the cable when the soil moves (soil reinforcement with sheet piling or pile rows, etc.).

2.3.46. 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 over railway bridges, as well as 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 repeated bending should be used (see also 1.7.11 ).

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 pass from shore to sea in the presence of strong sea surf, when laying cables 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 polyvinyl chloride sheath, as well as cables in an aluminum sheath without special waterproof coatings, are not allowed for installation in water.

When laying cable lines through small non-navigable and non-floating rivers with a width (including the floodplain) of no more than 100 m, with a stable bed and bottom, the use of cables with tape armor is allowed.

2.3.50. For oil-filled cable lines with a voltage of 110 - 220 kV, the type and design of 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 that allowed by GOST for cables with viscous impregnation, cables with a non-draining impregnation mass, cables with depleted impregnated paper insulation and cables with rubber or plastic insulation must be used. For the specified conditions, cables with viscous impregnation may only be used with stop couplings placed along the route, in accordance with the permissible level differences for these cables according to GOST.

The difference in vertical elevations between the locking couplings of low-pressure oil-filled cable lines is determined by the corresponding technical specifications for the cable and the calculation of recharge under extreme thermal conditions.

2.3.52. In four-wire networks, four-core cables must be used. Laying neutral conductors separately from phase conductors is not permitted. 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 wire) in four-wire networks alternating current(lighting, power and mixed) with a solidly grounded neutral, with the exception of installations with an explosive atmosphere and installations in which, under normal operating conditions, the current in the neutral wire is more than 75% of the permissible 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 city electrical networks of 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 compared to three-core cables or if it is not possible to use a cable of the required construction 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 parallel-connected cables and safe touching of their shells, to prevent heating of metal parts in the immediate vicinity and to securely fasten the cables in insulating clasps.

FEEDING DEVICES AND OIL PRESSURE ALARM FOR CABLE OIL-FILLED LINES

2.3.54. The oil-feeding 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 must be determined taking into account the consumption for feeding the cable. In addition, there must be a supply of oil for emergency repairs and for filling the longest section of the cable line with oil.

2.3.56. Feeding tanks for low pressure lines are recommended to be placed in enclosed spaces. It is recommended to place a small number of feed tanks (5 - 6) at open feeding points in light metal boxes on portals, supports, etc. (at ambient temperature not lower than minus 30 ° C). Feed tanks must be equipped with oil pressure indicators and protected from direct exposure to solar radiation.

2.3.57. Feeding units for 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 the 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 topped up 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. It is recommended that the feeding units be provided with electricity from two independent power sources with a mandatory device automatic switching on reserve (AVR). Feeding units must be separated from one another by fireproof partitions with a fire resistance rating of at least 0.75 hours.

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

2.3.61. At least two sensors must be installed on each section of the low-pressure oil-filled cable line, and on the high-pressure line - a sensor on each feeding unit. Emergency signals must be transmitted to a point with permanent personnel on duty. 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 centers (electricity network, network area).

2.3.63. The oil pipeline connecting the manifold 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 switchboard room with devices for automatic control of the feeding unit should not exceed permissible limits.

CABLE CONNECTIONS AND TERMINATIONS

2.3.65. When connecting and terminating power cables, coupling designs that comply with their operating and environmental conditions should be used. Connections and terminations on cable lines must be made in such a way 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 can withstand the test voltages for the cable line and comply with GOST requirements.

2.3.66. For cable lines up to 35 kV, end and connecting couplings must be used in accordance with the current technical documentation for couplings approved in accordance with the established procedure.

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

The length of sections and installation locations of locking couplings on low-pressure oil-filled cable lines are determined taking into account the replenishment of the lines with oil in normal and transient thermal conditions.

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

In areas with electrified transport (metropolitan, trams, railways) or with soils that are aggressive to the metal shells and couplings of cable lines, the couplings must be accessible for inspection.

2.3.68. On cable lines made with cables with normally impregnated paper insulation and cables impregnated with a non-drip compound, cable connections must be made using stop-transition couplings if the laying level of cables with normally impregnated insulation is higher than the laying level of cables impregnated with a non-drip compound (see also 2.3.51 ).

2.3.69. On cable lines above 1 kV, made with flexible cables with rubber insulation in a rubber hose, cable connections must be made by hot vulcanization and 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 3 ´ 95 mm 2 4 pcs.; for three-core cables 1 - 10 kV with sections x 120 - 3 ´ 240 mm 2 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 connecting couplings is determined by the design.

The use of undersized cable sections for the construction of long cable lines is not permitted.

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 Chapter. 1.7.

2.3.72. When grounding or neutralizing 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 (end, connecting, etc.). On cables of 6 kV and above with aluminum sheaths, grounding of the sheath and armor must be carried out with 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 mm 2.

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

If an external end coupling and a set of arresters are installed on the structure support, then the armor, metal shell and coupling must be connected to the grounding device of the arresters. In this case, using only metallic cable sheaths as a grounding device 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 of buildings and structures” by the USSR Ministry of Energy.

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

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

When using armored cables for low-pressure oil-filled 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 oil-filled high-pressure 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 calculations in the project.

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

2.3.75. When a cable line transitions into an overhead line (OHL) and if there is no grounding device at the overhead line support, cable couplings (mast) can be grounded by attaching the metal sheath of the cable, if the cable coupling at the other end of the cable is connected to a grounding device or the grounding resistance of the cable sheath complies with the requirements of Chapter. 1.7.

SPECIAL REQUIREMENTS FOR CABLE FACILITIES OF POWER PLANTS, SUBSTATIONS AND DISTRIBUTION DEVICES

2.3.76. 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 energy system (see also 2.3.113 ).

2.3.77. The main electrical connection diagram, the auxiliary diagram and the operating current diagram, equipment control and layout of the equipment and cable facilities of a power plant or substation must be carried out in such a way that in case of fires in the cable facilities or outside it, disruption of the operation of more than one unit of the power plant, simultaneous loss of mutually redundant connections of switchgears 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.) must be provided, isolated from the process equipment and preventing access to the cables by unauthorized persons.

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

preventing overheating of cables from heated surfaces of technological equipment;

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

preventing the laying of transit cables in hydraulic ash removal technological tunnels, chemical water treatment rooms, 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, alarm systems, fire extinguishing systems, etc.) must be laid so that in case of fires the possibility of simultaneous loss of mutually redundant cable lines is excluded. In areas of cable facilities where the occurrence of an accident threatens its further development, cable flows should be divided into groups isolated from one another. The distribution of cables into groups depends on local conditions.

2.3.80. Within one power unit, it is permitted to construct cable structures with a fire resistance limit of 0.25 hours. In this case, technological equipment that can serve as a source of fire (oil tanks, oil stations, etc.) must have fences with a fire resistance limit of at least 0.75 h, eliminating the possibility of cables catching fire in the event of a fire on this equipment.

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

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

For single cables and small groups of cables (up to 20), operational platforms may not be constructed, but it must be possible to quickly replace and repair cables under operating conditions.

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

2.3.81. Cable floors and tunnels in which cables of various power units of a 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 hours, 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 rating of at least 0.75 hours must be provided.

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

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

2.3.82. The entry points of cables into the premises of closed switchgear and in the room of control and protection panels of open switchgear must have partitions with a fire resistance rating of at least 0.75 hours.

Cable entry points to power plant control panels must be covered with partitions with a fire resistance rating 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 limit of at least 0.75 hours and have ceilings at the top and bottom. Extended shafts, when passing through ceilings, but at least after 20 m, must be divided into compartments by fireproof partitions with a fire resistance limit of at least 0.75 hours.

Walk-through 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 a backfill on the bottom and a layer of fine earth on top that does not contain stones, construction waste and slag.

Cables along their entire length must be protected from mechanical damage by covering them at voltages 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 earth-moving 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 laid at a depth of 1 - 1.2 m, cables of 20 kV and below (except for city power supply 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 excavation). Asphalt street surfaces, etc. are considered as places where excavations are 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 in trenches with no more than two cable lines to use signal plastic tapes instead of bricks that meet the technical requirements approved by the USSR Ministry of Energy. It is not allowed to use warning tapes at the intersections of cable lines with utility lines and over-cable couplings at a distance of 2 m in each direction from the crossed utility line or coupling, as well as at the approaches of lines to switchgears and substations within a radius of 5 m.

* According to local conditions, with the consent of the line owner, it is allowed to expand the scope of application 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 placing one cable in a trench, the tape must be laid along the axis of the cable; with a larger number of cables, the edges of the tape must protrude beyond the outer cables by at least 50 mm. When laying more than one tape across the width of a trench, adjacent tapes must be laid with an overlap of at least 50 mm wide.

When using signal tape, laying cables in a trench with a cable cushion, 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 electrical networks.

2.3.84. The depth of cable lines from the planning mark must be no less than: lines up to 20 kV 0.7 m; 35 kV 1 m; when crossing streets and squares, regardless of voltage 1 m.

Oil-filled cable 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 entering lines into buildings, as well as where they intersect 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 across arable land must be done at a depth of at least 1 m, while the strip of land above the route can be occupied for crops.

2.3.85. The clear distance from a 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 basements and technical undergrounds of residential and public buildings, one should be guided by the SNiP of the Gosstroy of Russia.

2.3.86. When laying cable lines in parallel, the horizontal clear distance 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 cables 20 - 35 kV and between them and other cables;

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

4) 500 mm between oil-filled cables 110 - 220 kV and other cables: in this case, 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, in cases of need, by agreement between operating organizations, taking into account local conditions, to reduce the distances specified in paragraphs. 2 and 3, up to 100 mm, and between power cables up to 10 kV and communication cables, except for cables with circuits sealed with high-frequency systems telephone communication, 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 control cables is not standardized.

2.3.87. When laying cable lines in a planted area, the distance from the cables to the tree trunks must, 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 a green area with shrub plantings, the specified distances can be reduced to 0.75 m.

2.3.88. When laying in parallel, the horizontal clear distance from cable lines with voltages 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 heating pipes - 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 for pipelines with flammable liquids and gases, to 0.5 m without special cable protection and to 0.25 m when laying cables in pipes. For oil-filled cable lines 110 - 220 kV in a convergence section with a length of no more than 50 m, it is allowed to reduce the horizontal clear distance 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 , eliminating the possibility of mechanical damage. Parallel laying of cables above and below pipelines is not permitted.

2.3.89. When laying a cable line parallel to a heat pipe, the clear distance between the cable and the wall of the heat pipe channel must be at least 2 m, or the heat pipe throughout the entire area of ​​proximity to the cable line must have such thermal insulation so that additional heating by the heat pipe at the point 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 lines 20 - 220 kV.

2.3.90. When laying a cable line parallel to railways, the cables must, as a rule, be laid outside the road exclusion zone. Laying cables within the exclusion zone is allowed only in agreement with organizations of the Ministry of Railways, and 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 permissible to reduce the specified distances, while the cables throughout the approach area must be laid in blocks or pipes.

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

2.3.91. When laying a cable line parallel to tram tracks, the distance from the cable to the axis of the tram track must be at least 2.75 m. In cramped conditions, this distance can be reduced, provided that the cables throughout the approach area will be laid in insulating blocks or pipes specified in 2.3.90.

2.3.92. When laying a cable line parallel to highways of categories I and II (see. 2.5.146 ) 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 departments.

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 the grounded parts and grounding conductors of overhead line supports above 1 kV must be at least 5 m at voltages up to 35 kV, 10 m at voltages 110 kV and above. In cramped conditions, the distance from cable lines to underground parts and grounding conductors of individual overhead line supports above 1 kV is allowed at least 2 m; in this case, 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 supports (current conductors) and overhead lines above 1 kV, if the grounding devices of these supports are connected to the substation grounding loop.

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

* Agreed with the USSR Ministry of Communications.

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. This distance can be reduced to 0.25 m, provided that the cable is laid at the intersection plus at least 2 m in each direction in pipes.

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

2.3.96. When cable lines up to 35 kV cross heat pipes, the distance between the cables and the ceiling of the heat pipe in the clear must be at least 0.5 m, and in cramped conditions - at least 0.25 m. In this case, the heat pipe at the intersection plus 2 m in each direction from the outer cables must have such thermal insulation that the temperature of the ground does not increase 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 the cables to 0.5 m instead of 0.7 m (see. 2.3.84 ); use of a cable insert with 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 cable replacement can be done without excavation work (for example, inserting pipe ends into chambers).

When an oil-filled cable line crosses a heat pipe, the distance between the cables and the ceiling of the heat pipe must be at least 1 m, and in cramped conditions - at least 0.5 m. In this case, the heat pipe at the intersection plus 3 m in each direction from the outermost cables must have such thermal insulation so that the ground temperature does not rise by more than 5 °C at any time of the year.

2.3.97. When cable lines cross railways and highways, the 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 road surface.

When cable lines cross railways electrified and subject to direct current electrification*, the blocks and pipes must be insulating (see. 2.3.90 ). The intersection must be at a distance of at least 10 m from the arrows, crosses and points of connection of suction cables to the rails. The intersection of cables with the tracks of electrified rail transport should be made at an angle of 75 - 90° to the axis of the track.

* Agreed with the Ministry of Railways.

The ends of blocks and pipes must be insulated 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 paths (for example, on slips, etc.), cables, as a rule, should be laid directly in the ground.

When the route of cable lines crosses a newly constructed non-electrified railway or highway, relocation of existing cable lines is not required. At the intersection, reserve blocks or pipes with tightly sealed ends should be laid in the required quantity in case of cable repairs.

In the case of a transition of a cable line into an overhead line, the cable must exit to the surface at a distance of at least 3.5 m from the base of the embankment or from the edge of the canvas.

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

2.3.99. When tiled lines cross vehicle entrances to courtyards, garages, etc. Cables must be laid in pipes. Cables at intersections of streams and ditches should be protected in this way.

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 steeply inclined routes, installing cable couplings on them is not recommended. If it is necessary to install cable joints in such areas, horizontal platforms must be made underneath them.

To ensure the possibility of reinstalling the couplings in the event of their damage on the cable line, it is necessary to lay the cable on both sides of the couplings with a reserve.

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

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

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

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

The need to protect cable lines from corrosion should be determined based on the combined data of electrical measurements and chemical analyzes of soil samples. Protection of cable lines from corrosion should not create conditions that are 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. If there are stray currents in the ground, it is necessary to install control points on cable lines in places and at distances that make it possible to determine 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 places where cables exit to transformer substations, distribution points, etc.

LAYING 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 material for blocks and pipes, you should take into account the level of groundwater and its 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 permissible number of channels in blocks, the distances between them and their size must be taken in accordance with 1.3.20 .

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

2.3.105. The depth of cable blocks and pipes in the ground should be taken according to local conditions, but not be less than the distances given in 2.3.84 , counting to the top cable. The depth of installation of cable blocks and pipes in closed areas and in the fields 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 a 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 pass into the ground, cable wells should be constructed to ensure convenient pulling of cables and their removal from the blocks. Such wells should also be constructed on straight sections of the route at a distance from one another determined by the maximum permissible tension of the cables. When the number of cables is up to 10 and the voltage is not higher than 35 kV, the transition of cables from blocks to the ground can be carried out without cable wells. In this case, the places where cables exit from the blocks must be sealed with waterproof material.

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

Measures must be taken to prevent the penetration of water and small animals from trenches into buildings, tunnels, etc. through pipes or openings.

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

2.3.111. If the groundwater level is high on the territory of the outdoor switchgear, preference should be given to above-ground methods of laying cables (in trays or boxes). Aboveground trays and slabs for their covering must be made of reinforced concrete. The 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 interfere with the flow of storm water. If there are openings in the bottoms of the above-ground gutters that allow for the release of storm water, there is no need 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 must be ensured. For this purpose, crossings over the trays must be arranged using reinforced concrete slabs, taking into account the load from passing traffic, while maintaining the location of the trays at the same level. When using cable trays, laying cables under roads and crossings in pipes, channels and trenches located below the trays is not allowed.

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

LAYING CABLE LINES IN CABLE STRUCTURES

2.3.112. Cable structures of all types must 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, overpasses 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. Extended tunnels must be divided by the same partitions into compartments no more than 150 m long, if available power and control cables and no more than 100 m in the presence of oil-filled cables. The area of ​​each double floor compartment should be no more than 600 m2.

Doors in cable structures and partitions with a fire resistance limit of 0.75 hours must have a fire resistance limit 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 must be provided outside or into premises with production categories G and D. The number and location of exits from cable structures must be determined based on local conditions, but there must be at least two. If the length of the cable structure is no more than 25 m, it is allowed to have one output.

Doors of cable structures must be self-closing, with sealed doorways. 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 keep them in the closed position.

Walk-through cable racks with service bridges must have entrances with stairs. 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 overpasses for persons not involved in cable maintenance. Doors must have self-locking locks that can be opened without a key from the inside of the overpass.

The distance between the entrances to the cable gallery when laying cables no 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 load-bearing building structures (columns, beams) made of reinforced concrete with a fire resistance limit of at least 0.75 hours or rolled steel with a fire resistance limit of at least 0.25 hours.

Load-bearing structures of buildings and structures that can be dangerously deformed or reduce mechanical strength when groups (streams) of cables laid near these structures on external cable overpasses and galleries burn, must have protection that provides a fire resistance limit of the protected structures of at least 0.75 hours.

Cable galleries must be divided into compartments by fireproof fire 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 and no more than 120 m when laying oil-filled cables. The above requirements do not apply to external cable galleries that are partially closed.

2.3.114. In tunnels and canals, measures must be taken to prevent process water and oil from entering them, and drainage of soil and storm water must also be ensured. The floors in them must have a slope of at least 0.5% towards water collectors or storm drains. The passage from one tunnel compartment to another, when they are located at different levels, must be carried out using a ramp with an inclination angle of no higher than 15°. The construction of steps between tunnel compartments is prohibited.

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

Drainage mechanisms must be provided in tunnels; In this case, it is recommended to use automatic start-up depending on the water level. Starting devices and electric motors must be designed to allow them to operate in particularly damp places.

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

2.3.115. Cable ducts and double floors in switchgears and rooms must be covered with removable fireproof slabs. In electrical machinery and similar rooms, it is recommended to cover the channels with corrugated steel, and in control panel rooms with parquet floors - with wooden boards with parquet, protected from below with asbestos and asbestos with tin. The covering of ducts and double floors must be designed to allow the movement of related equipment over it.

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

2.3.117. In areas where molten metal, high-temperature liquids, or substances that destroy the metal sheaths of cables may be spilled, the construction of cable channels is not allowed. In these areas, it is also not allowed to install hatches in sewers and tunnels.

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 pipes together in buildings, additional heating of the air by the heat pipe 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.

2.3.120. In cable structures, it is recommended to lay cables in entire construction lengths, and the placement of cables in structures should be done in accordance with the following:

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 backup 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 overpasses and in external partially enclosed cable galleries, installation of dividing partitions specified in paragraphs. 1, 3 and 4 are not required. In this case, mutually redundant power cable lines (with the exception of lines to electrical receivers of special group I category) should be laid with a distance between them of at least 600 mm and are recommended to be located: 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, as a rule, be laid in separate cable structures. It is allowed to lay them together with other cables; in this case, 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. The same partitions should be used to separate oil-filled cable lines from one another.

2.3.122. The need for the use and scope of automatic stationary means of detecting and extinguishing fires in cable structures must 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 overpasses and galleries, fire hydrants must be located in such a way that the distance from any point on the axis of the overpass and gallery route to the nearest hydrant does not exceed 100 m.

2.3.123. In cable structures, the laying of control cables and power cables with a cross-section of 25 mm 2 or more, with the exception of unarmored cables with a lead sheath, should be carried out along cable structures (consoles).

Control unarmored cables, unarmored power cables with a lead sheath and unarmored power cables of all designs with a cross-section of 16 mm 2 or less should be laid on trays or partitions (solid or non-solid).

It is allowed to lay cables along the bottom of the channel with a depth of no 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 rating of at least 0.25 hours.

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

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

Table 2.3.1. Shortest distance for cable structures

* The useful length of the console should be no more than 500 mm on straight sections of the route.

** When cables are arranged in a 250 mm triangle.

*** Including for cables laid in cable shafts.

In cable structures, the height, width of passages and the distance between structures and cables must be no less than those given in table. 2.3.1. Compared to the distances given in the table, a local narrowing of passages up to 800 mm or a reduction in height to 1.5 m over a length of 1.0 m is allowed with a corresponding reduction in the vertical distance between cables for one-sided and two-sided structures.

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 cable bundle must 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 of cables in bundles, multilayered in boxes, cable bundles to trays should be done in such a way that deformation of the cable sheaths under the influence of its own weight and fastening devices is prevented.

5. For fire safety purposes, fire barrier belts must be installed inside the boxes: in vertical sections - at a distance of no more than 20 m, as well as when passing through the ceiling; in horizontal sections - when passing through partitions.

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

Laying power cables in bundles and multi-layers is not allowed.

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

* Agreed with the Central Committee of the Trade Union of Power Plant and Electrical Industry Workers.

2.3.126. Oil-filled low-pressure cables must be mounted on metal structures in such a way that the possibility of forming closed magnetic circuits around the cables is excluded; the distance between fastening 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 design. In addition, pipelines must be fixed on fixed supports to prevent thermal deformations in the 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 support foundations. The number of these supports and their locations are determined by the project.

Mechanical supports and fastenings of branching devices on high-pressure lines must prevent swinging of branching pipes and the formation of closed magnetic circuits around them, and insulating gaskets must be provided in places where supports are fastened or touched.

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

Coastal wells at underwater crossings must be sized to accommodate backup cables and feeders.

A pit must be installed in the floor of the well to collect groundwater and storm water; a drainage device must 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. Hatches for cable wells and tunnels must have a diameter of at least 650 mm and be closed with double metal covers, the bottom of which must have a device for closing with a lock that can be opened from the side of the tunnel without a key. Covers must have provisions for their removal. Indoors, the use of a second cover is not required.

2.3.129. Special protective covers must be installed on connecting couplings of power cables with voltages of 6 - 35 kV in tunnels, cable floors and channels to localize fires and explosions that may occur during electrical breakdowns in the couplings.

2.3.130. End couplings on high-pressure oil-filled cable lines must be located in rooms with positive air temperatures or be equipped with automatic heating when the ambient temperature drops below +5 °C.

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

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

Table 2.3.2. The shortest distance from cable overpasses and galleries to buildings and structures

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

The calculation of ventilation of cable structures is determined based on the temperature difference between incoming and exhaust air of no more than 10 °C. At the same time, the formation of bags of hot air in narrowing tunnels, turns, bypasses, etc. must be prevented.

Ventilation devices must be equipped with dampers (dampers) to stop the access of air in the event of a fire, as well as to prevent freezing of the tunnel in winter. The design of ventilation devices must ensure the possibility of using automatic shutdown of air flow into structures.

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

Cable structures, with the exception of wells for connecting 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 installed.

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

The shortest clear distances from cable overpasses 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, intra-plant railways and roads, fire passages, cable cars, overhead communication and radio lines and pipelines is recommended to be performed at an angle of at least 30°.

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

When running parallel overpasses and galleries with overhead communication and radio lines, the shortest distances between the cables and wires of the communication and radio lines are determined based on the calculation of the influence of cable lines on the communication and radio lines. Communication and radio wires can be located under and above overpasses and galleries.

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

LAYING CABLE LINES IN PRODUCTION PREMISES

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

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

Cables (including armored ones) located in places where machinery, equipment, cargo and vehicles 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, should be at least 0.5 m, and between gas pipelines and pipelines with flammable liquids - at least 1 m. At shorter approach distances and at intersections, the cables must be protected from mechanical damage (metal pipes, casings, etc.) throughout the entire approach area plus 0.5 m on each side, and, if necessary, 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 liquids in a vertical plane is not allowed.

2.3.135. Laying of cables in the floor and interfloor ceilings should be done in channels or pipes; Tightly sealing cables in them is not allowed. The passage of cables through ceilings and internal walls can be carried out in pipes or openings; After laying cables, gaps in pipes and openings must be sealed with easily pierced fireproof material.

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

Open cable routing in staircases is not permitted.

UNDERWATER CABLE LINES

23.136. When cable lines cross rivers, canals, etc. Cables should be laid primarily in areas with a bottom and banks that are less susceptible to erosion (crossing streams - see Fig. 2.3.46 ). When laying cables across rivers with unstable beds and banks prone to erosion, the cables should be buried in the bottom taking into account local conditions. The depth of cables is determined by the project. Laying cables in areas of piers, moorings, harbours, ferry crossings, as well as regular winter moorings of ships and barges is not recommended.

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

2.3.138. Cable lines must be laid along the bottom in such a way that they do not become suspended in uneven places; sharp protrusions must be removed. Shallows, rock ridges and other underwater obstacles on the route should be avoided or trenches or passages 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 areas, as well as on shipping and rafting routes; 2 m when crossing oil-filled cable lines.

In reservoirs where dredging is periodically carried out, cables are buried in the bottom to a level 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 the trenches with sandbags followed by throwing stones.

2.3.140. Distance between cables buried in the bottom of rivers, canals, etc. with a reservoir width of up to 100 m, it is recommended to take at least 0.25 m. Newly constructed underwater cable lines must be laid at a distance from existing cable lines of at least 1.25 of the depth of the 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 speed not exceeding 1 m/s, the distance between the individual phases (without special fastenings of the phases to each other) is recommended to be at least 0.5 m, and the distances between the extreme cables of parallel lines - at least 5 m.

For underwater installations at a depth of more than 15 m, as well as at flow speeds of more than 1 m/s, the distances between individual phases and lines are taken in accordance with the design.

When laying oil-filled cable lines and lines up to 35 kV in parallel underwater, the horizontal distance between them in the clear 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 bodies of water to pipelines (oil pipelines, gas pipelines, etc.) must be determined by the project depending on the type of dredging work 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.

23.141. On banks without improved embankments, a reserve of at least 10 m in length for river installations and 30 m for sea installations must be provided at the location of the underwater cable crossing, which is laid in a figure eight pattern. On improved embankments, cables must be laid in pipes. As a rule, cable wells should be installed at the point where cables exit. The upper end of the pipe must go into the coastal well, and the lower end must be at a depth of at least 1 m from the lowest water level. In coastal areas, pipes 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 exposure of cables during ice drifts and floods by strengthening the banks (paving, fender dams, piles, sheet piles, slabs, etc.).

2.3.143. Crossing cables with each other 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 of navigation on inland shipping routes and sea straits.

2.3.145. When laying three or more cables up to 35 kV in water, one backup cable must be provided for every three workers. When laying oil-filled cable lines from single-phase cables in water, a reserve must be provided: for one line - one phase, for two lines - two phases, for three or more - according to the design; 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 existing operating phases.

LAYING CABLE LINES IN SPECIAL STRUCTURES

2.3.146. The laying of cable lines on stone, reinforced concrete and metal bridges must be carried out under the pedestrian part of the bridge in channels or in fireproof pipes separate for each cable; measures must be taken to prevent storm water from flowing through these pipes. On metal and reinforced concrete bridges and when approaching them, it is recommended to lay cables in asbestos-cement pipes. In places of transition from bridge structures to the ground, it is recommended to lay cables in asbestos-cement pipes.

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

2.3.147. The laying of cable lines along wooden structures (bridges, piers, piers, etc.) must be carried out in steel pipes.

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

2.3.149. Laying cable lines along dams, dikes, piers and moorings directly in an earthen trench is allowed if the earth layer is at least 1 m thick.

Open - on walls and building structures on brackets and cable structures; in boxes, trays, on cables, cable and technological racks; in the channels; hidden - in the ground (trenches), in blocks

5. Exits from the tunnel, as well as exits from tunnel ventilation shafts, must be located outside hazardous areas.

7.3.128. Open conductors up to 1 kV and above of flexible and rigid structures are allowed to be laid across the territory of an enterprise with explosive zones on specially designed overpasses or supports.

Laying open conductors on overpasses with pipelines with flammable gases and flammable liquids and instrumentation overpasses is prohibited.

7.3.129. Current conductors up to 10 kV in a sheath with a degree of protection IP54 can be laid across the territory of an enterprise with explosive zones on special overpasses, overpasses with pipelines with flammable gases and flammable liquids and instrumentation overpasses, if there is no possibility of harmful interference on the instrumentation and automation circuits from the current conductors. Current conductors should be laid at a distance of at least 0.5 m from pipelines, if possible on the side of pipelines with non-flammable substances.

7.3.130. The minimum permissible distances from conductors to premises with explosive zones and to external explosive installations are given in table. 7.3.15.

GROUNDING DEVICES

1.8.36. Grounding devices are tested to the extent provided for in this paragraph.

1. Checking the elements of the grounding device. This should be done by inspecting the elements of the grounding device within the scope of inspection. The cross-sections and conductivity of the elements of the grounding device must comply with the requirements of these Rules and design data.

2. Checking the circuit between grounding conductors and grounding elements. You should check the cross-sections, integrity and strength of the grounding and grounding conductors, their connections and connections. There should be no breaks or visible defects in the grounding conductors connecting the devices to the grounding loop. The reliability of welding is checked by hitting a hammer.

3. Checking the condition of breakdown fuses in electrical installations up to 1 kV. Breakdown fuses must be in good working order and correspond to the rated voltage of the electrical installation.

4. Checking the phase-zero circuit in electrical installations up to 1 kV with solid grounding of the neutral. The check should be carried out in one of the following ways: by directly measuring the current of a single-phase fault to the housing or wire using special instruments; by measuring the impedance of the phase-zero loop with subsequent calculation of the single-phase fault current.

The current of a single-phase fault to the housing or neutral wire must ensure reliable operation of the protection, taking into account the coefficients given in the relevant chapters of these Rules.

5. Measuring the resistance of grounding devices. The resistance values ​​must comply with the values ​​given in the relevant chapters of these Rules.

POWER CABLE LINES

1.8.37. Power cable lines with voltage up to 1 kV are tested according to clauses 1, 2, 7, 13, voltage above 1 kV and up to 35 kV - according to clauses 1-3, 6, 7, 11, 13, voltage 110 kV and above - in to the full extent provided for in this paragraph.

1. Checking the integrity and phasing of the cable cores. The integrity and coincidence of the phase designations of the connected cable cores are checked.

2. Insulation resistance measurement. Produced with a megohmmeter for a voltage of 2.5 kV. For power cables up to 1 kV, the insulation resistance must be at least 0.5 MOhm. For power cables above 1 kV, the insulation resistance is not standardized. The measurement should be made before and after testing the cable with increased voltage.

3. Test with increased voltage of rectified current. Power cables above 1 kV are tested with increased rectified current voltage.

The values ​​of the test voltage and the duration of application of the normalized test voltage are given in table. 1.8.42.

Table 1.8.42. Rectified current test voltage for power cables

During testing with increased voltage of rectified current, attention is paid to the nature of the change in the leakage current.

The cable is considered to have passed the test if no breakdown occurred, there were no sliding discharges or surges of the leakage current or its increase after it reached a steady value.

4. Power frequency high voltage test. It is allowed to carry out for 110-220 kV lines instead of testing with rectified current; test voltage value: for lines 110 kV-220 kV (130 kV relative to ground); for lines 220 kV-500 kV (288 kV relative to ground). The duration of application of the normalized test voltage is 5 minutes.

5. Determination of the active resistance of the cores. Produced for lines 35 kV and above. Active resistance of cable line cores to direct current, reduced to 1 mm cross-section, 1 m length and temperature +20°C, should be no more than 0.0179 Ohm for a copper conductor and no more than 0.0294 Ohm for an aluminum conductor.

6. Determination of the electrical working capacitance of the cores. Produced for lines 35 kV and above. The measured capacity, reduced to specific values, should not differ from the factory test results by more than 5%.

7. Measurement of current distribution along single-core cables. The unevenness in the distribution of currents on the cables should not be more than 10%.

8. Checking protection against stray currents. The operation of the installed cathodic protection is checked.

9. Test for the presence of undissolved air (impregnation test). Produced for oil-filled cable lines 110-220 kV. The content of undissolved air in the oil should be no more than 0.1%.

10. Testing of feeding units and automatic heating of end couplings. Produced for oil-filled cable lines 110-220 kV.

Table 1.8.43. Limit values ​​for cable line oil quality indicators

11. Monitoring the condition of the anti-corrosion coating. Produced for steel pipelines of oil-filled cable lines 110-220 kV.

12. Checking oil characteristics. Produced for oil-filled cable lines 110-220 kV. Sampling should be done from all elements of the line. Samples of S-220 grade oil taken after 3 days. after filling, must meet the requirements of table. 1.8.43.

Samples of MH-3 oil, taken from low and high pressure lines 5 days after filling, must meet the requirements of Table. 1.8.43.

13. Ground resistance measurement. Produced on lines of all voltages for terminations, and on lines 110-220 kV, in addition, for metal structures of cable wells and make-up points.

OVERHEAD POWER LINES

VOLTAGE ABOVE 1 kV

1.8.38. Overhead power lines are tested to the extent provided for in this paragraph.

1. Checking insulators. Produced in accordance with 1.8.32.

2. Checking wire connections. This should be done by external inspection and measuring the voltage drop or resistance. Crimped wire connections are rejected if:

the steel core is located asymmetrically;

geometric dimensions (length and diameter of the pressed part) do not meet the requirements of the installation instructions for connecting clamps of this type;

there are cracks, signs of significant corrosion and mechanical damage on the surface of the connector or clamp;

The voltage drop or resistance on the connection section (connector) is more than 1.2 times higher than the voltage drop or resistance on the wire section of the same length (the test is carried out selectively on 5-10% of connectors);

the curvature of the pressed connector exceeds 3% of its length, the steel core of the pressed connector is located asymmetrically.

Welded joints are rejected if:

there was a burnout of the outer wire or a welding violation was detected when the connected wires were bent;

the shrinkage cavity at the welding site has a depth of more than 1/3 of the diameter of the wire, and for steel-aluminum wires with a cross-section of 150-600 mm- more than 6 mm;

The voltage drop or resistance is more than 1.2 times the voltage drop or resistance across a section of wire of the same length.

3. Measurement of grounding resistance of supports, their guy wires and cables. Manufactured in accordance with 1.8.36.

Page: 13

Ticket number 3

Laying cable lines.

PUE Cable lines with voltage up to 220 kV

2.3.1. This Chapter 1 of the Rules applies to cable power lines up to 220 kV, as well as lines carried out by control cables. Cable lines of higher voltages are carried out according to special projects. Additional requirements for cable lines are given in Chapter. 7.3, 7.4 and 7.7.

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 in one trench. If there are a larger number of cables, it is recommended to lay them in separate trenches with a distance between groups of cables of at least 0.5 m or in channels, tunnels, overpasses and galleries.

2. Laying cables in tunnels, along 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 very tight spaces along the route, at intersections with railway tracks and driveways, when there is a possibility of a metal spill, etc.

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

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

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

2.3.28. In the areas of substations and distribution facilities, cable lines must 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 impassable parts of streets (under sidewalks), along courtyards and technical strips in the form of lawns.

2.3.30. In streets and squares saturated with underground communications, it is recommended to lay 10 or more cable lines in a stream in collectors and cable tunnels. When crossing streets and squares with improved surfaces and heavy traffic, cable lines should be laid in blocks or pipes.

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

2.3.32. The implementation of different 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 (rock, pebble, gravel, crushed stone and coarse sand); heaving and subsidence soils are unsuitable for laying cable lines in them. Cables can be laid directly in the ground if the number of cables is no more than four. Due to soil, permafrost and climatic conditions, laying cables in pipes laid in the ground is prohibited. At intersections with other cable lines, roads and underground communications, cables should be protected with reinforced concrete slabs.

Laying cables near buildings is not permitted. 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 may be used in places where the active layer consists of non-heaving soils and has a flat surface with a slope of no more than 0.2%, ensuring surface water drainage. Cable ducts should be made of waterproof reinforced concrete and covered on the outside with reliable waterproofing. The channels must be covered from above with reinforced concrete slabs. Channels can be made buried in the ground or without burial (on top of the ground). In the latter case, a cushion with a thickness of at least 0.5 m of dry soil must be made under the channel and near it.

2.3.33. Inside buildings, cable lines can be laid directly along building structures (open and in boxes or pipes), in channels, blocks, tunnels, pipes laid in floors and ceilings, as well as along machine foundations, in shafts, 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 method of laying them is determined by the project.

2.3.65. When connecting and terminating power cables, coupling designs that comply with their operating and environmental conditions should be used. Connections and terminations on cable lines must be made in such a way 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 can withstand the test voltages for the cable line and comply with GOST requirements.

2.3.66. For cable lines up to 35 kV, end and connecting couplings must be used in accordance with the current technical documentation for couplings, approved in accordance with the established procedure.

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

The length of sections and installation locations of locking couplings on low-pressure oil-filled cable lines are determined taking into account the replenishment of the lines with oil in normal and transient thermal conditions.

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

In areas with electrified transport (metropolitan, trams, railways) or with soils that are aggressive to the metal shells and couplings of cable lines, the couplings must be accessible for inspection.

2.3.68. On cable lines made with cables with normally impregnated paper insulation and cables impregnated with a non-drip compound, cable connections must be made using stop-transition couplings if the laying level of cables with normally impregnated insulation is higher than the laying level of cables impregnated with a non-drip compound (see also 2.3 .51).

2.3.69. On cable lines above 1 kV, made with flexible cables with rubber insulation in a rubber hose, cable connections must be made by hot vulcanization and 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 3 x 95 mm 2 4 pcs.; for three-core cables 1-10 kV with sections 3 x 120 - 3 x 240 mm 2 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 connecting couplings is determined by the design.

The use of undersized cable sections for the construction of long cable lines is not permitted.

2.3.3. A cable structure is a structure specifically designed to house cables, cable couplings, as well as oil-feeding devices and other equipment designed to ensure the normal operation of oil-filled cable lines. Cable structures include: cable tunnels, channels, ducts, blocks, shafts, floors, double floors, cable overpasses, galleries, chambers, feeding points.

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

A cable channel is a channel that is closed and buried (partially or completely) in the ground, floor, ceiling, etc. a non-passable structure designed to accommodate cables, the installation, inspection and repair of which can only be carried out with the ceiling removed.

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

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

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

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

A cable chamber is an underground cable structure, covered with a blind removable concrete slab, intended for laying cable couplings 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 overhead or ground-based open horizontal or inclined extended cable structure. The cable rack can be pass-through or non-pass-through.

A cable gallery is an above-ground or above-ground, fully or partially closed (for example, without side walls) horizontal or inclined extended cable passage structure.

2.3.4. It's called a box - see. 2.1.10 .

2.3.5. It's called a tray - see. 2.1.11 .

2.3.6. An oil-filled cable line of low or high pressure is a line in which the long-term permissible excess pressure is:

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

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

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

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

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

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

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

GENERAL REQUIREMENTS

2.3.12. When choosing a cable line route, you should, if possible, avoid areas with soils that are aggressive to the metal sheaths of cables (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 must be installed 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 outer cables, and when cable lines pass in cities under sidewalks - 0.6 m towards buildings and 1 m towards the roadway.

For submarine cable lines up to and above 1 kV, in accordance with the specified rules, a security zone must 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 cable line route should be selected taking into account the lowest cable consumption, ensuring its safety under mechanical stress, providing protection from corrosion, vibration, overheating and from 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 feed tanks on the line.

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

Cables must be laid with a reserve length sufficient to compensate for possible soil displacements and temperature deformations of the cables themselves and the structures along which they are laid; It is prohibited to lay cable reserves in the form of rings (turns);

Cables laid horizontally along structures, walls, ceilings, etc. must be rigidly secured at the end points, directly at the end seals, on both sides of bends and at connecting and locking couplings;

Cables laid vertically along structures and walls must be secured in such a way that deformation of the shells is prevented and the connections of the cores in the couplings are not broken under the influence of the cables’ own weight;

The structures on which unarmored cables are laid must be made in such a way that the possibility of mechanical damage to the cable sheaths is excluded; in places of rigid fastening, the sheaths of these cables must be protected from mechanical damage and corrosion using elastic gaskets;

Cables (including armored ones) located in places where mechanical damage is possible (movement of vehicles, machinery and cargo, accessibility to 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 close to other cables in use, measures must be taken to prevent damage to the latter;

Cables must be laid at a distance from heated surfaces that prevents heating of the cables above the permissible level, and protection of the cables from the breakthrough of hot substances at the installation sites of valves and flange connections must be provided.

2.3.16. Protection of cable lines from stray currents and soil corrosion must meet the requirements of these Rules and SNiP 3.04.03-85“Protection of building structures and structures from corrosion” of the State Committee for Construction of Russia.

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