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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Section 2. Sewerage of electricity Cable lines up to 220 kV. Choice of laying methods
Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE) 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. 4. When choosing methods for laying cables across urban areas, the initial capital costs and costs associated with the production of maintenance and repair work, as well as the convenience and cost-effectiveness of maintaining structures, should be taken into account. 2.3.26. On the territories of power plants, cable lines should be laid in tunnels, ducts, channels, blocks, overpasses and in galleries. Laying power cables in trenches is allowed only to remote auxiliary facilities (fuel depots, workshops) with no more than six. In the territories of power plants with a total capacity of up to 25 MW, it is also allowed to lay cables in trenches. 2.3.27. On the territories of industrial enterprises, cable lines should be laid in the ground (in trenches), tunnels, blocks, channels, overpasses, in galleries and along the walls of buildings. 2.3.28. On the territories of substations and switchgears, cable lines should be laid in tunnels, ducts, channels, pipes, in the ground (in trenches), ground reinforced concrete trays, along overpasses and in galleries. 2.3.29. In cities and towns, single cable lines should, as a rule, be laid in the ground (in trenches) along the impassable part of the streets (under sidewalks), in yards and technical lanes in the form of lawns. 2.3.30. On streets and squares saturated with underground utilities, it is recommended to lay cable lines in the amount of 10 or more in a stream in collectors and cable tunnels. When crossing streets and squares with improved coatings and with heavy traffic, cable lines should be laid in blocks or pipes. 2.3.31. When constructing cable lines in permafrost areas, physical phenomena associated with the nature of permafrost should be taken into account: heaving soil, frost cracks, landslides, etc. Depending on local conditions, cables can be laid in the ground (in trenches) below the active layer, in in the active layer in dry, well-draining soils, in artificial embankments from large-skeletal dry imported soils, in trays on the surface of the earth, on overpasses. Joint laying of cables with heating pipelines, water supply, sewerage, etc. in special structures (collectors) is recommended. 2.3.32. The implementation of various types of cable laying in permafrost areas should be carried out taking into account the following: 1. For laying cables in earthen trenches, the most suitable soils are draining soils (rocky, pebble, gravel, crushed stone and coarse sand); heaving and subsidence soils are unsuitable for laying cable lines in them. It is allowed to lay cables directly in the ground with no more than four cables. Due to ground-frozen and climatic conditions, it is prohibited to lay cables in pipes laid in the ground. At intersections with other cable lines, roads and underground utilities, cables should be protected with reinforced concrete slabs. Laying cables near buildings is not allowed. The entry of cables from the trench into the building in the absence of a ventilated underground must be carried out above the zero mark. 2. 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. 2.3.33. Inside buildings, cable lines can be laid directly along building structures (openly and in boxes or pipes), in channels, blocks, tunnels, pipes laid in floors and ceilings, as well as on machine foundations, in shafts, cable floors and double floors. 2.3.34. Oil-filled cables can be laid (with any number of cables) in tunnels and galleries and in the ground (in trenches); the way they are laid is determined by the project.
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