Section 2. Sewerage of electricity

Cable lines up to 220 kV. Laying cable lines in cable structures

Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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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 150 m in the presence of oil-filled cables. The area of ​​each compartment of a double floor should be no more than 100 m600.

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 supporting building structures (columns, beams) made of reinforced concrete with a fire resistance of at least 0,75 hours or of rolled steel with a fire resistance of at least 0,25 hours.

The supporting structures of buildings and structures that can dangerously deform or reduce the mechanical strength during combustion of groups (streams) of cables laid near these structures on external cable racks and galleries must have protection that ensures the fire resistance of the protected structures is at least 0,75 hours.

Cable galleries should be divided into compartments by fireproof fireproof partitions with a fire resistance limit of at least 0,75 hours. The length of the gallery compartments should be no more than 150 m when laying cables up to 35 kV in them and no more than 120 m when laying oil-filled cables. For external cable galleries, partially closed, these requirements do not apply.

2.3.114. In tunnels and channels, measures must be taken to prevent the ingress of process water and oil into them, and soil and storm water must be drained. The floors in them must have a slope of at least 0,5% towards water collectors or storm sewers. The passage from one section of the tunnel to another, when they are located at different levels, must be carried out using a ramp with an elevation angle of not more than 15º. 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 15º 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, high-temperature liquids or substances that destroy the metal sheaths of cables can be spilled, 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 ºС, for which ventilation and thermal insulation on the pipes should be provided.

2.3.120. In cable structures, cables are recommended to be laid in full construction lengths, and the placement of cables in structures should be carried out in accordance with the following:

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

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

3. Power cables up to 1 kV are recommended to be laid over cables above 1 kV; however, they should be separated by a partition.

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

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

2.3.121. Oil-filled cables should be laid, as a rule, in separate cable structures. It is allowed to lay them together with other cables; at the same time, oil-filled cables should be placed in the lower part of the cable structure and separated from other cables by horizontal partitions with a fire resistance limit of at least 0,75 hours. Oil-filled cable lines should be separated from one another with the same partitions.

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

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

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

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

It is allowed to lay cables along the bottom of the channel at a depth of not more than 0,9 m; in this case, the distance between a group of power cables above 1 kV and a group of control cables must be at least 100 mm, or these groups of cables must be separated by a fireproof partition with a fire resistance of at least 0,25 hours.

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

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

In cable structures, the height, width of passages and the distance between structures and cables must be at least those given in Table. 2.3.1. Compared with the distances given in the table, local narrowing of the passages up to 800 mm or a decrease in height up to 1,5 m over a length of 1,0 m is allowed with a corresponding decrease in the vertical distance between the cables with one-sided and two-sided arrangement of structures.

Table 2.3.1. Minimum distance for cable installations

* The 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. In bundles and multilayers, only cables with the same type of sheaths should be laid.

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

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

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

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

2.3.125. * In places saturated with underground utilities, it is allowed to 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. Oil-filled low-pressure cables must be fastened to metal structures in such a way that the possibility of the formation of closed magnetic circuits around the cables is excluded; the distance between the attachment points should be no more than 1 m.

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

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

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

2.3.127. The height of cable wells must be at least 1,8 m; chamber height is not standardized. Cable wells for connecting, locking and semi-locking couplings must have dimensions that ensure the installation of couplings without breaking.

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

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

Cable wells must be equipped with metal ladders.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The smallest height of the cable overpass and gallery in the impassable part of the territory of an industrial enterprise should be taken into account the possibility of laying the lower row of cables at a level of at least 2,5 m from the planning ground level.

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

See other articles Section Rules for the installation of electrical installations (PUE).

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