P 2.3 86 poes of the sixth edition. Requirements and prices for cable laying in the ground. Feeding devices and oil pressure signaling of cable oil-filled lines

CABLE LINES WITH VOLTAGE UP TO 220 kV

Scope, definitions

2.3.1. This chapter of the Rules applies to cable power lines up to 220 kV, as well as lines performed by control cables. cable lines more high voltage carried out on 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 the transmission of electricity or its individual impulses, consisting of one or more parallel cables with connecting, locking and end sleeves (terminals) and fasteners, and for oil-filled lines, in addition, with make-up devices and an oil pressure alarm system.

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

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

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

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

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

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

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

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

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

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

2.3.4. It is called a box - see 2.1.10.

2.3.5. It is called a tray - see 2.1.11.

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

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

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

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

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

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

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

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

General requirements

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

cables should be laid at a distance from heated surfaces that prevents cables from heating above the permissible level, while protection of cables from hot substances in the places where valves and flange connections are installed should 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 against corrosion" of the State Construction Committee of Russia.

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

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

2.3.19. Open laying of cable lines should be carried out taking into account the direct action of solar radiation, as well as heat radiation from various kinds heat sources. When laying cables on geographical latitude over 65° solar protection is not required.

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

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

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

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

2.3.24. Protective zones of cable lines laid in the ground in undeveloped areas must be marked with information signs.

Information signs should be installed at least every 500 m, as well as in places where the direction of cable lines changes. The information signs should indicate the width of the security zones of cable lines and the telephone numbers of cable line owners.

Choice of laying methods

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

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

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

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

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

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

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

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

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

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

2.3.31. When constructing cable lines in permafrost areas, physical phenomena associated with the nature of permafrost should be taken into account: heaving soil, frost cracks, landslides, etc. Depending on the 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 from large-skeletal dry imported soils, in trays on the surface of the earth, on overpasses. Joint laying of cables with heating pipelines, water supply, sewerage, etc. is recommended. in special facilities (collectors).

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

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

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

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

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

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

Cable selection

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

2.3.53. For cable lines up to 35 kV, it is allowed to use single-core cables if this leads to significant savings in copper or aluminum in comparison with three-core ones, or if it is not possible to use a cable of the required 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 cables connected in parallel and safe contact with their sheaths, to exclude heating of metal parts located in the immediate vicinity and to securely fasten the cables in insulating clips.

Feeding devices and oil pressure signaling of cable oil-filled lines

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

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

2.3.56. Feed tanks of low pressure lines are recommended to be placed indoors. A small number of feed tanks (5-6) per open points power supplies are recommended to be placed in light metal boxes on portals, supports, etc. (at ambient temperature not lower than minus 30 °С). Make-up tanks must be equipped with oil pressure gauges and protected from direct sunlight.

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

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

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

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

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

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

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

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

Connections and cable terminations

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

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

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

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

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

An error has occurred

The payment was not completed due to a technical error, funds from your account
were not written off. Try to wait a few minutes and repeat the payment again.

Application area

3.2.1. This chapter of the Rules applies to relay protection devices for elements of the electrical part of power systems, industrial and other electrical installations above 1 kV; generators, transformers (autotransformers), generator-transformer blocks, power lines, tires and synchronous compensators.

Protection of all electrical installations above 500 kV, cable lines above 35 kV, as well as electrical installations of nuclear power plants and direct current transmissions, is not considered in this chapter of the Rules.

Requirements for the protection of electrical networks up to 1 kV, electric motors, capacitor units, electrothermal installations, see, respectively, in Ch. 3.1, 5.3, 5.6 and 7.5.

Relay protection devices for electrical installations that are not considered in this and other chapters must be carried out in accordance with the general requirements of this chapter.

General requirements

3.2.2. Electrical installations must be equipped with relay protection devices designed for:

a) automatic shutdown damaged element from the rest, undamaged part of the electrical system (electrical installation) using switches; if the damage (for example, earth fault in networks with isolated neutral) does not directly disrupt the operation of the electrical system, the relay protection is allowed to act only on the signal.

b) response to dangerous, abnormal modes of operation of the elements of the electrical system (for example, overload, voltage increase in the stator winding of the hydro generator); Depending on the operating mode and operating conditions of the electrical installation, relay protection must be performed with an effect on the signal or on the shutdown of those elements that, if left in operation, can lead to damage.

3.2.3. In order to reduce the cost of electrical installations, instead of circuit breakers and relay protection, fuses or open fuses should be used if they:

can be selected with the required parameters (rated voltage and current, rated breaking current, etc.);

provide the required selectivity and sensitivity;

do not interfere with the use of automation (automatic reclosing - AR, automatic switching on of the reserve - ATS, etc.) required by the operating conditions of the electrical installation.

When using fuses or open fuses, depending on the level of unbalance in open-phase mode and the nature of the supplied load, it is necessary to consider the need to install protection against open-phase mode at the receiving substation.

3.2.4. Relay protection devices should provide the shortest possible short circuit disconnection time in order to maintain uninterrupted operation of the undamaged part of the system (stable operation of the electrical system and electrical installations of consumers, ensuring the possibility of restoring normal operation through the successful operation of automatic reclosure and automatic transfer, self-starting of electric motors, retraction into synchronism, etc.) and restrictions on the area and degree of damage to the element.
3.2.5. Relay protection acting on shutdown, as a rule, must provide selectivity of action, so that if any element of the electrical installation is damaged, only this damaged element is switched off.

A non-selective protection action is allowed (corrected by a subsequent AR or ATS action):

a) to ensure, if necessary, the acceleration of the tripping of the short circuit (see 3.2.4);

b) when using simplified main electrical circuits with separators in the circuits of lines or transformers that disconnect the damaged element during a dead time.

3.2.6. Relay protection devices with time delays that ensure the selectivity of the action are allowed to be performed if: when a short circuit is disconnected with time delays, the requirements of 3.2.4 are met; protection acts as a backup (see 3.2.15).

3.2.7. Reliability of functioning of relay protection (triggering when conditions for triggering and non-operating in their absence) must be ensured by the use of devices that, in terms of their parameters and design, correspond to their intended purpose, as well as by proper maintenance of these devices.

If necessary, special measures should be used to improve the reliability of operation, in particular circuit redundancy, continuous or periodic monitoring of the state, etc. The probability of erroneous actions should also be taken into account. service personnel when performing the necessary operations with relay protection.

3.2.8. In the presence of relay protection having voltage circuits, devices should be provided:

automatically deactivating the protection in case of disconnection of circuit breakers, blown fuses and other violations of the voltage circuits (if these violations can lead to false operation of the protection in normal mode), as well as signaling violations of these circuits;

signaling violations of voltage circuits, if these violations do not lead to false operation of the protection under normal conditions, but can lead to excessive operation in other conditions (for example, during a short circuit outside the protected zone).

3.2.9. When installing high-speed relay protection on power lines with tubular arresters, it must be provided for detuning it from the operation of arresters, for which:

the shortest response time of the relay protection before the signal to turn off should be more than the time of a single operation of the arresters, namely about 0.06-0.08 s;

starting protection elements, triggered by a current pulse of the arresters, should have the shortest possible return time (about 0.01 s from the moment the pulse disappears).

3.2.10. For relay protections with time delays, in each specific case, it is necessary to consider the feasibility of providing protection from the initial value of current or resistance during a short circuit in order to exclude failures of protection operation (due to attenuation of short circuit currents in time, as a result of oscillations, the appearance of an arc at the fault site and etc.).

3.2.11. Protections in electrical networks of 110 kV and above must have devices that block their action during swings or asynchronous running, if such swings or asynchronous running are possible in these networks, in which the protections can operate unnecessarily.

It is allowed to use similar devices for lines below 110 kV, interconnecting power sources (based on the likelihood of oscillations or asynchronous running and possible consequences unnecessary shutdowns).

It is allowed to perform protection without blocking during swings, if the protection against swings is adjusted in time (protection time delay is about 1.5-2 s).

3.2.12. The action of relay protection should be recorded by indicator relays, operation indicators built into the relay, operation counters or other devices to the extent necessary to account for and analyze the operation of protections.

3.2.13. Devices that record the action of relay protection for shutdown should be installed so that the operation of each protection is signaled, and in case of complex protection, its individual parts (different levels of protection, separate sets of protection against different types of damage, etc.).

3.2.14. On each of the elements of the electrical installation, the main protection should be provided, designed to operate in case of damage within the entire protected element with a time shorter than that of other protections installed on this element.

3.2.15. For action in case of failure of protections or switches of adjacent elements, back-up protection should be provided, designed to provide long-range back-up action.

If the main protection of the element has absolute selectivity (for example, high-frequency protection, longitudinal and transverse differential protection), then a backup protection must be installed on this element, which performs the functions of not only long-range, but also short-range redundancy, i.e., acting in case of failure of the main protection this element or removing it from work. For example, if differential-phase protection is used as the main protection against short circuits between phases, then three-stage distance protection can be used as a backup.

If the main line protection of 110 kV and above has relative selectivity (for example, step protection with time delays), then:

it is allowed not to provide a separate backup protection, provided that the long-range backup action of the protection of adjacent elements in case of a short circuit on this line is provided;

measures should be provided to ensure short-range redundancy if long-range redundancy in case of a short circuit on this line is not provided.

3.2.16. For power transmission lines of 35 kV and above, in order to increase the reliability of fault disconnection at the beginning of the line, current cutoff without time delay can be provided as additional protection, provided that the requirements of 3.2.26 are met.

3.2.17. If the full provision of long-range redundancy is associated with a significant complication of protection or is technically impossible, it is allowed:

1) do not reserve short-circuit disconnections behind transformers, on reacted lines, lines of 110 kV and above in the presence of near redundancy, at the end of a long adjacent section of the 6-35 kV line;

2) have long-range redundancy only for the most common types of damage, without taking into account rare operating modes and taking into account the cascading action of protection;

3) provide for non-selective action of protection in case of short circuit on adjacent elements (with long-range backup action) with the possibility of de-energizing in some cases substations; at the same time, it should be possible to ensure that these non-selective trips are corrected by the action of automatic reclosure or automatic reclosure.

3.2.18. Redundancy devices in case of failure of circuit breakers (RPF) should be provided in electrical installations of 110-500 kV. It is allowed not to provide for breaker failure in electrical installations of 110-220 kV, subject to the following conditions:

1) the required sensitivity and allowable disconnection times from long-range backup devices are provided;

2) under the action of backup protections, there is no loss additional elements due to tripping of circuit breakers that are not directly adjacent to the failed circuit breaker (for example, there are no sectioned busbars, branch lines).

At power plants with generators having direct cooling of stator winding conductors, in order to prevent damage to generators in the event of failures of 110-500 kV circuit breakers, breaker failure should be provided, regardless of other conditions.

In case of failure of one of the switches of the damaged element (line, transformer, busbars) of the electrical installation, the breaker failure must act to turn off the switches adjacent to the failed one.

If the protections are connected to remote current transformers, then the breaker failure should also operate in the event of a short circuit in the zone between these current transformers and the circuit breaker.

It is allowed to use simplified breakers that operate in case of short circuit with circuit breaker failures not on all elements (for example, only in case of short circuit on lines); at a voltage of 35-220 kV, in addition, it is allowed to use devices that act only to turn off the bus-connecting (sectional) switch.

When the effectiveness of long-range redundancy is insufficient, the need to increase the reliability of short-range redundancy in addition to breaker failure should be considered.

3.2.19. When performing backup protection as a separate set, it should be carried out, as a rule, in such a way that it is possible to separately check or repair the main or backup protection while the element is operating. In this case, the main and backup protection should be powered, as a rule, from different secondary windings of current transformers.

The power supply of the main and backup protections of power transmission lines of 220 kV and above should be carried out, as a rule, from different automatic circuit breakers of the operational direct current.

3.2.20. The assessment of the sensitivity of the main types of relay protection should be carried out using a sensitivity coefficient determined by:

for protections that respond to values that increase under damage conditions - as a ratio of the calculated values of these values (for example, current or voltage) in case of a metal short circuit within the protected zone to the protection operation parameters;

for protections responding to values that decrease under damage conditions, as the ratio of the operation parameters to the calculated values of these values (for example, voltage or resistance) with a metal short circuit within the protected zone.

The calculated values of the quantities should be established based on the most unfavorable types of damage, but for a realistically possible mode of operation of the electrical system.

3.2.21. When assessing the sensitivity of the main protections, it is necessary to proceed from the fact that the following minimum coefficients of their sensitivity should be provided:

1. Overcurrent protections with and without voltage start, directional and non-directional, as well as current single-stage directional and non-directional protections, included in the negative or zero sequence components:

for current and voltage organs - about 1.5;

for reverse and zero sequence power direction organs - about 2.0 in terms of power and about 1.5 in terms of current and voltage;

For the maximum current protection of transformers with a low voltage of 0.23-0.4 kV, the smallest sensitivity coefficient can be about 1.5.

2. Step current or current and voltage protection, directional and non-directional, connected to full currents and voltages or zero sequence components:

for current and voltage organs, the protection stage designed to operate in case of short circuit at the end of the protected section, without taking into account the backup action - about 1.5, and in the presence of a reliably operating selective reserve stage - about 1.3; if there is a separate busbar protection at the opposite end of the line, the corresponding sensitivity factors (about 1.5 and about 1.3) for the zero sequence protection stage can be provided in the cascade trip mode;

for power direction organs of zero and reverse sequence - about 2.0 in terms of power and about 1.5 in terms of current and voltage;

for a power direction organ switched on for full current and voltage, it is not standardized in terms of power and about 1.5 in terms of current.

3. Remote protection against multi-phase short circuits:

for a launching body of any type and a remote body of the third stage - about 1.5;

for a remote control of the second stage, designed to operate in case of a short circuit at the end of the protected section, without taking into account the backup action - about 1.5, and in the presence of a third stage of protection - about 1.25; for the indicated organ, the current sensitivity should be about 1.3 (with respect to the current precise work) when damaged at the same point.

4. Longitudinal differential protection of generators, transformers, lines and other elements, as well as full differential protection of tires - about 2.0; for the current starting body of the incomplete differential distance protection of the generator voltage buses, the sensitivity should be about 2.0, and for the first stage of the incomplete differential current protection of the generator voltage buses, made in the form of a cut-off, it should be about 1.5 (with a short circuit on the tires).

For differential protection of generators and transformers, the sensitivity should be checked for short circuits at the terminals. In this case, regardless of the values of the sensitivity factor for hydro generators and turbo generators with direct cooling of the winding conductors, the protection operation current should be taken less than the rated current of the generator (see 3.2.36). For autotransformers and step-up transformers with a capacity of 63 MVA and more, it is recommended to take the operation current without braking less than the nominal one (for autotransformers - less than the current corresponding to the typical power). For other transformers with a capacity of 25 MVA and more, the operation current, excluding braking, is recommended to take no more than 1.5 of the rated current of the transformer.

It is allowed to reduce the sensitivity factor for the differential protection of a transformer or a generator-transformer unit to a value of about 1.5 in the following cases (in which providing a sensitivity factor of about 2.0 is associated with a significant complication of protection or is technically impossible):

with a short circuit on the outputs low voltage step-down transformers with a power of less than 80 MVA (determined taking into account voltage regulation);

in the mode of switching on the transformer under voltage, as well as for short-term modes of its operation (for example, when one of the supply sides is turned off).

For the mode of supplying voltage to damaged tires by turning on one of the supply elements, it is allowed to reduce the sensitivity coefficient for the differential protection of tires to a value of about 1.5.

The specified coefficient of 1.5 also applies to the differential protection of the transformer in case of a short circuit after the reactor, installed on the low voltage side of the transformer and entering the zone of its differential protection. In the presence of other protections covering the reactor and meeting the requirements for sensitivity in case of short circuit after the reactor, the sensitivity of the differential protection of the transformer in case of short circuit at this point may not be provided.

5. Transverse differential directional protection of parallel lines:

for the current relay and voltage relay of the starting body of the protection kits against phase-to-phase short circuits and earth faults - about 2.0 with the switches on on both sides of the damaged line (at the point of the same sensitivity) and about 1.5 with the switch off on the opposite side of the damaged line;

for a zero-sequence power directional control - about 4.0 in terms of power and about 2.0 in terms of current and voltage with the switches on on both sides and about 2.0 in terms of power and about 1.5 in terms of current and voltage with the switch off on the opposite side ;

for the power direction body, switched on to full current and voltage, it is not standardized in terms of power, but in terms of current - about 2.0 with the switches on on both sides and about 1.5 with the switch off on the opposite side.

for the reverse or zero sequence power direction control, which controls the trip circuit, - about 3.0 in terms of power, about 2.0 in terms of current and voltage;

7. Differential-phase high-frequency protection:

for starting bodies that control the trip circuit - about 2.0 for current and voltage, about 1.5 for resistance.

8. Current cutoffs without time delay, installed on generators with a power of up to 1 MW and transformers, with a short circuit at the place of protection installation - about 2.0.

9. Protection against earth faults on cable lines in networks with isolated neutral (acting on a signal or on shutdown):

for protections that respond to fundamental frequency currents - about 1.25;

for protections that respond to high-frequency currents - about 1.5.

10. Protection against earth faults on overhead lines in networks with an isolated neutral, acting on a signal or on a shutdown - about 1.5.

3.2.22. When determining the sensitivity factors specified in 3.2.21, paragraphs 1, 2. 5 and 7, the following must be taken into account:

1. The power sensitivity of the inductive power direction relay is checked only when it is turned on for the components of currents and voltages of the reverse and zero sequences.

2. The sensitivity of the power direction relay, made according to the comparison circuit (absolute values or phases), is checked: when turned on for full current and voltage - by current; when connected to the components of currents and voltages of the reverse and zero sequences - by current and voltage.

3.2.23. For generators operating on busbars, the sensitivity of the current protection against earth faults in the stator winding, acting to trip, is determined by its trip current, which should not exceed 5 A. An increase in trip current up to 5.5 A is allowed as an exception.

For generators operating in a block with a transformer, the sensitivity factor of protection against single-phase earth faults, covering the entire stator winding, must be at least 2.0; for zero-sequence voltage protection that does not cover the entire stator winding, the response voltage must be no more than 15 V.

3.2.24. The sensitivity of protections on alternating operating current, performed according to the scheme with deshunting of tripping electromagnets, should be checked taking into account the actual current error of current transformers after deshunting. In this case, the minimum value of the sensitivity coefficient of the tripping electromagnets, determined for the condition of their reliable operation, should be approximately 20% higher than that accepted for the corresponding protections (see 3.2.21).

3.2.25. The smallest sensitivity factors for back-up protection in case of a fault at the end of an adjacent element or the most distant of several consecutive elements included in the redundancy zone should be (see also 3.2.17):

for organs of current, voltage, resistance - 1.2;

for power direction organs of reverse and zero sequences - 1.4 in terms of power and 1.2 in terms of current and voltage;

for a power direction body switched on for full current and voltage, it is not standardized in terms of power and 1.2 in terms of current.

When assessing the sensitivity of backup protection stages that provide short-range redundancy (see 3.2.15), one should proceed from the sensitivity factors given in 3.2.21 for the corresponding protections.

3.2.26. For current cutoffs without time delay, installed on the lines and performing the functions of additional protection, the sensitivity coefficient should be about 1.2 for short circuit at the place of protection installation in the most favorable mode according to the sensitivity condition.

3.2.27. If the action of the protection of the next element is possible due to a failure due to insufficient sensitivity of the protection of the previous element, then the sensitivity of these protections must be coordinated with each other.

It is allowed not to coordinate the stages of these protections, intended for long-range redundancy, if the failure to disconnect the short circuit due to insufficient sensitivity of the protection of the subsequent element (for example, the protection of the negative sequence of generators, autotransformers) can lead to serious consequences.

3.2.28. In networks with a solidly grounded neutral, such a neutral grounding mode should be selected based on the conditions of relay protection power transformers(i.e., the placement of transformers with a grounded neutral), at which the values of currents and voltages during earth faults ensure the operation of the relay protection of network elements at all possible modes operation of the electrical system.

For step-up transformers and transformers with two- and three-sided power supply (or significant feeding from synchronous electric motors or synchronous compensators) with incomplete winding insulation on the side of the neutral terminal, as a rule, the occurrence of an unacceptable operation mode for them with an isolated neutral on dedicated buses should be excluded or a section of a 110-220 kV network with an earth fault of one phase (see 3.2.63).

3.2.29. Current transformers designed to power the current circuits of short-circuit relay protection devices must meet the following requirements:

1. In order to prevent unnecessary operation of protection during short circuit outside the protected area, the error (total or current) of current transformers, as a rule, should not exceed 10%. Higher errors are allowed when using protections (for example, differential protection of tires with braking), the correct operation of which, with increased errors, is ensured with the help of special measures. These requirements must be met:

for step protections - in case of a short circuit at the end of the coverage area of the protection stage, and for directional step protections - also with an external short circuit;

for other protections - with an external short circuit.

For differential current protections (tires, transformers, generators, etc.), the total error must be taken into account, for the remaining protections - the current error, and when the latter are turned on for the sum of the currents of two or more current transformers and in the external short circuit mode - the total error.

When calculating the allowable loads on current transformers, it is allowed to take the total error as the initial one.

2. The current error of current transformers in order to prevent protection failures in case of short circuit at the beginning of the protected zone should not exceed:

according to the conditions of increased vibration of the contacts of the power direction relay or current relay - the values \u200b\u200ballowed for the selected type of relay;

according to the conditions of the maximum allowable for the power direction relay and directional resistance relays, the angular error is 50%.

3. Voltage at the terminals secondary winding current transformers in case of short circuit in the protected area should not exceed the value allowed for the RPA device.

3.2.30. The current circuits of electrical measuring instruments (together with meters) and relay protection should be connected, as a rule, to different windings of current transformers.

It is allowed to connect them to one winding of current transformers, provided that the requirements of 1.5.18 and 3.2.29 are met. At the same time, in the protection circuits, which, according to the principle of operation, may not work correctly if the current circuits are disturbed, the inclusion of electrical measuring instruments is allowed only through intermediate current transformers and provided that the current transformers meet the requirements of 3.2.29 with an open secondary circuit of the intermediate current transformers.

3.2.31. Protection using direct acting relays, both primary and secondary, and protection on alternating operating current is recommended to be used, if possible, and leads to a simplification and reduction in the cost of the electrical installation.

3.2.32. As a source of alternating current for protection against short circuits, as a rule, current transformers of the protected element should be used. It is also allowed to use voltage transformers or auxiliary transformers.

Depending on the specific conditions, one of the following schemes must be applied: with deshunting of the circuit breaker opening electromagnets, using power supplies, using chargers with a capacitor.

3.2.33. Relay protection devices that are taken out of operation due to the conditions of the network mode, selectivity of action, or for other reasons, must have special devices to take them out of work by operational personnel.

To ensure operational checks and tests, protection circuits should provide, where necessary, test blocks or test clamps.

When laying cable lines directly in the ground, the cables must be laid in trenches and have a backfill at the bottom, and a backfill with a layer of fine earth that does not contain stones, construction debris and slag on top.

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

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

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

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

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

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

2.3.84

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

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

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

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

2.3.85

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

2.3.86

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

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

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

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

________________

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

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

The distance between the control cables is not standardized.

2.3.87

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

When laying cables within the green zone with bush plantings these distances can be reduced to 0.75 m.

2.3.88

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

In cramped conditions, it is allowed to reduce the specified distances for cable lines to 35 kV, with the exception of distances to pipelines with flammable liquids and gases, up to 0.5 m without special protection cables and up to 0.25 m when laying cables in pipes. For oil-filled cable lines 110-220 kV in the approach section with a length of not 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 excluding the possibility of mechanical damage. Parallel laying of cables above and below pipelines is not allowed.

2.3.89

When laying a cable line in parallel with a heat 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 in the entire area of approach to the cable line must have such thermal insulation that additional heating of the earth by the heat pipe at the place where the cables pass at any time of the year is not exceeded 10°C for cable lines up to 10 kV and 5°C - for lines 20-220 kV.

2.3.90

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

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

__________________

2.3.91

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

2.3.92

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

2.3.93

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

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

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

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

2.3.94

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

___________________

* Agreed with the Ministry of Communications of the USSR.

2.3.95

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

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

2.3.96

When cable lines intersect heat pipes up to 35 kV, the distance between the cables and the overlap of the heat pipe in the light 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 extreme cables must have such thermal insulation that the temperature of the earth does not rise by more than 10 ° C in relation to the highest summer temperature and by 15 ° C in relation to the lowest winter temperature.

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

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

2.3.97

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

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

________________

* Agreed with the Ministry of Railways.

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

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

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

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

2.3.98

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

2.3.99

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

2.3.100

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

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

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

2.3.101

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

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

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

When laying cables in aggressive soils and areas with the presence of stray currents of unacceptable values, cathodic polarization should be used (installation of electrical drains, protectors, cathodic protection). For any method of connecting electrical drainage devices, the norms of potential differences in the suction sections provided for #M12291 871001027SNiP 3.04.03-85 #S "Protection of building structures and structures against corrosion" Gosstroy of Russia. It is not recommended to use cathodic protection with external current on cables laid in saline soils or saline water bodies.

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

To control potentials on cable lines, it is allowed to use the places where cables exit to transformer substations, distribution points, etc.

Amended by the decision of the Ministry of Fuel and Energy of 13.07.98 (paragraph 2.3.24)

Scope, definitions

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

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

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

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

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

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

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

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

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

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

2.3.4. It is called a box - see 2.1.10.

2.3.5. It is called a tray - see 2.1.11.

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

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

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

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

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

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

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

General requirements

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

2.3.23. Each cable line must have its own number or name. If the cable line consists of several parallel cables, then each of them must have the same number with the addition of the letters A, B, C, etc. Openly laid cables, as well as all cable boxes, must be tagged with the designation on the cable tags and end couplings of the brand, voltage, section, number or name of the line; on the tags of the couplings - the number of the coupling and the date of installation. Labels must be 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. Protective zones of cable lines laid in the ground in undeveloped areas must be marked with information signs. Information signs should be installed at least every 500 m, as well as in places where the direction of cable lines changes. The information signs should indicate the width of the security zones of cable lines and the telephone numbers of cable line owners. (see Appendix "Requirements for information signs and their installation")

Choice of laying methods

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

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

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

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

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

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

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

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

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

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

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

Cable selection

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The difference in vertical marks between the locking sleeves of low-pressure oil-filled cable lines is determined by the corresponding specifications on the cable and calculation of make-up at limiting thermal conditions.

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

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

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

Feeding devices and oil pressure signaling of cable oil-filled lines

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

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

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

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

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

Connections and cable terminations

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

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

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

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

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

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

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

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

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

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

grounding

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

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

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

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

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

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

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

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

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

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

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

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

Special requirements for cable management of power plants, substations and switchgears

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

2.3.77. Main wiring diagram, auxiliary circuit and control current circuit, equipment control and equipment layout and cable industry power plants or substations must be designed in such a way that in the event of fires in the cable industry or outside it, disruptions in the operation of more than one unit of the power plant, simultaneous loss of mutually redundant connections of switchgear and substations, as well as failure of fire detection and extinguishing systems, are excluded.

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

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

preventing overheating of cables from heated surfaces of process equipment;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Laying cable lines in the ground

2.3.83. When laying cable lines directly in the ground, the cables must be laid in trenches and have a backfill at the bottom, and a backfill with a layer of fine earth that does not contain stones, construction debris and slag on top.

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

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

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

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

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

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

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

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

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

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

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

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

________________

The distance between the control cables is not standardized.

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

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

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

In cramped conditions, it is allowed to reduce the specified distances for cable lines to 35 kV, with the exception of distances to pipelines with flammable liquids and gases, up to 0.5 m without special cable protection and up to 0.25 m when laying cables in pipes. For oil-filled cable lines 110-220 kV in the approach section with a length of not 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 excluding the possibility of mechanical damage. Parallel laying of cables above and below pipelines is not allowed.

2.3.89. When laying a cable line in parallel with a heat 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 in the entire area of approach to the cable line must have such thermal insulation that additional heating of the earth by the heat pipe at the place where the cables pass at any time of the year is not exceeded 10°C for cable lines up to 10 kV and 5°C - for lines 20-220 kV.

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

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

__________________

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

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

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

The clear distance from the cable line to 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.

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

___________________

* Agreed with the Ministry of Communications of the USSR.

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

2.3.96. When cable lines intersect heat pipes up to 35 kV, the distance between the cables and the overlap of the heat pipe in the light 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 extreme cables must have such thermal insulation that the temperature of the earth does not rise by more than 10 ° C in relation to the highest summer temperature and by 15 ° C in relation to the lowest winter temperature.

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

________________

* Agreed with the Ministry of Railways.

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

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

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

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

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

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

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

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

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

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

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

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

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 a material for blocks and pipes, one should take into account the level of groundwater and their aggressiveness, as well as the presence of stray currents.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Laying cable lines in cable structures

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

2.3.123. In cable structures, the laying of control cables and power cables with a cross section of 25 mm² or more, with the exception of unarmored cables with a lead sheath, should be carried out along cable structures (consoles).

Control unarmoured cables, unarmoured power cables with a lead sheath and unarmoured power cables of all designs with a cross section of 16 mm² or less should be laid along trays or partitions (solid or non-solid).

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

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

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

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

Table 2.3.1. Minimum distance for cable installations

Distance	Smallest dimensions, mm, when laying
Distance	in tunnels, galleries, cable floors and overpasses	in cable ducts and double floors
clear height	1800	Not limited, but not more than 1200 mm
Horizontally in the light between structures with their two-sided arrangement (passage width)	1000	300 at a depth of up to 0.6 m; 450 at a depth of more than 0.6 to 0.9 m; 600 at a depth of more than 0.9 m
Horizontally clear from the structure to the wall with one-sided arrangement (passage width)	900	Same
Vertically between horizontal structures*:
for power cables with voltage:
up to 10 kV	200	150
20-35 kV	250	200
110 kV and above	300**	250
for control cables and communication cables, as well as power sections up to 3x25 mm² with voltage up to 1 kV	100
Between supporting structures (cantilevers) along the length of the structure	800-1000
Vertically and horizontally in the clear between single power cables up to 35 kV***	Not less than cable diameter
Horizontally between control and communication cables***	Not standardized
Horizontally in the light between cables with a voltage of 110 kV and above	100	Not less than cable diameter
* The useful length of the console should not exceed 500 mm on straight sections of the track. When cables are arranged in a 250 mm triangle. * Including for cables laid in cable shafts.

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

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

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

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

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

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

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

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

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

___________________

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

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

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

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

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

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

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

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

Cable wells must be equipped with metal ladders.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

construction	Normalized distance	Smallest dimensions, m
When parallel following, horizontally
Buildings and structures with blank walls	From the construction of the overpass and gallery to the wall of the building and structure	Not standardized
Buildings and structures with walls with openings	Same	2
In-plant non-electrified Railway	From the design of the overpass and gallery to the dimension of the approach of buildings	1 m for galleries and overpasses; 3 m for impassable flyovers
Intra-plant road and fire lanes	From flyover and gallery construction to curbstone, outer edge or road ditch sole	2
cable car	From the design of the overpass and gallery to the gauge of the rolling stock	1
Above ground pipeline		0,5
		See 2.5.114
When crossing, vertically
Intra-factory non-electrified railway	From the bottom mark of the overpass and gallery to the rail head	5,6
Intra-factory electrified railway	From the bottom mark of the overpass and gallery:
	up to the rail head	7,1
	to the highest wire or carrier cable of the contact network	3
Internal factory road (fire road)	From the bottom mark of the overpass and gallery to the canvas highway(fire lane)	4,5
Above ground pipeline	From the construction of the overpass and gallery to the nearest parts of the pipeline	0,5
Overhead power line	From the design of the overpass and gallery to the wires	See 2.5.113
Air communication and radio communication line	Same	1,5

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

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

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

Laying cable lines in industrial 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 openly laid cables for inspection.

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

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

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

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

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

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

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

Open cable routing stairwells not allowed.

Underwater cable laying

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

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

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

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

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

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

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

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

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

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

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

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

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

2.3.143. Crossing of cables under water is prohibited.

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

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

Laying cable lines in special facilities

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

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

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

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

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

SCOPE, DEFINITIONS

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

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

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

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

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

2.3.4. It is called a box - see 2.1.10.

2.3.5. It is called a tray - see 2.1.11.

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

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

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

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

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

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

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

GENERAL REQUIREMENTS