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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Section 2. Sewerage of electricity Cable lines up to 220 kV. Laying cable lines in the ground
Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE) 2.3.83. When laying cable lines directly in the ground, the cables must be laid in trenches and have backfilling from below, and backfilling from above with a layer of fine earth that does not contain stones, construction debris and slag. Cables throughout their entire length must be protected from mechanical damage by coating at a voltage of 35 kV and above with reinforced concrete slabs with a thickness of at least 50 mm; at voltages below 35 kV - with slabs or ordinary clay bricks in one layer across the cable route; when digging a trench with an earthmoving mechanism with a cutter width of less than 250 mm, as well as for one cable - along the cable line route. The use of silicate, as well as clay hollow or perforated bricks is not allowed. When laying at a depth of 1-1,2 m, cables of 20 kV and below (except for city power cables) may not be protected from mechanical damage. Cables up to 1 kV should have such protection only in areas where mechanical damage is likely (for example, in places of frequent 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 in trenches with no more than two cable lines to use signal plastic tapes instead of bricks that meet the technical requirements approved by the USSR Ministry of Energy. It is not allowed to use 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. 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. * 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. 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 the USSR. 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; 4) 500 mm between 110-220 kV oil-filled cables and other cables; at the same time, low-pressure oil-filled cable lines are separated from one another and from other cables by reinforced concrete slabs placed on edge; in addition, the electromagnetic influence on communication cables should be calculated. It is allowed, if necessary, by agreement between the operating organizations, taking into account local conditions, a reduction in the distances specified in paragraphs. 2 and 3, up to 100 mm, and between power cables up to 10 kV and communication cables, except for cables with circuits sealed 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, installation of fireproof partitions, etc.). The distance between the control cables is not standardized. * Agreed with the Ministry of Communications. 2.3.87. When laying cable lines in the plantation zone, the distance from the cables to the tree trunks should, as a rule, be at least 2 m. It is allowed, in agreement with the organization in charge of the green spaces, to reduce this distance, provided that the cables are laid in pipes laid by digging . When laying cables within the green zone with shrub plantings, the indicated distances can be reduced to 0,75 m. 2.3.88. With parallel laying, the horizontal distance in the light from cable lines with voltage up to 35 kV and oil-filled cable lines to pipelines, water supply, sewerage and drainage must be at least 1 m; to gas pipelines of low (0,0049 MPa), medium (0,294 MPa) and high pressure (more than 0,294 to 0,588 MPa) - at least 1 m; to high pressure gas pipelines (more than 0,588 to 1,176 MPa) - at least 2 m; to heat pipelines - see 2.3.89. In cramped conditions, it is allowed to reduce the specified distances for cable lines to 35 kV, with the exception of distances to pipelines with flammable liquids and gases, up to 0,5 m without special cable protection and up to 0,25 m when laying cables in pipes. For oil-filled cable lines 110-220 kV in the approach section no longer than 50 m, it is allowed to reduce the horizontal distance in the light to pipelines, with the exception of pipelines with flammable liquids and gases, up 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 by the heat pipe at the place where the cables pass at any time of the year does not exceed 10º C for cable lines up to 10 kV and 5º 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.) *. * Agreed with the Ministry of Railways. 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 2.5.146), the cables must be laid on the outside of the ditch or the bottom of the embankment at a distance of at least 1 m from the edge or at least 1,5 m from the curb stone. Reducing the specified distance is allowed in each individual case in agreement with the relevant road administrations. 2.3.93. When laying a cable line in parallel with an overhead line of 110 kV and above, the distance from the cable to the vertical plane passing through the outermost wire of the line must be at least 10 m. The clear distance from the cable line to grounded parts and ground electrodes of overhead lines above 1 kV must be at least 5 m at voltages up to 35 kV, 10 m at voltages of 110 kV and above. In cramped conditions, the distance from cable lines to underground parts and ground electrodes of individual overhead lines above 1 kV is allowed at least 2 m; at the same time, the distance from the cable to the vertical plane passing through the overhead line wire is not standardized. The clear distance from the cable line to the overhead line support up to 1 kV must be at least 1 m, and when laying the cable in the approach area in an insulating pipe, 0,5 m. In the territories of power plants and substations in cramped conditions, it is allowed to lay cable lines at distances of at least 0,5 m from the underground part of overhead communication towers (current conductors) and overhead lines above 1 kV, if the grounding devices of these towers are connected to the substation ground loop. 2.3.94. * When cable lines cross other cables, they must be separated by a layer of earth with a thickness of at least 0,5 m; this distance in cramped conditions for cables up to 35 kV can be reduced to 0,15 m, provided that the cables are separated along the entire intersection plus up to 1 m in each direction by slabs or pipes made of concrete or other equal strength material; the communication cables must be located above the power cables. * Agreed with the Ministry of Communications. 2.3.95. When cable lines cross pipelines, including oil and gas pipelines, the distance between the cables and the pipeline must be at least 0,5 m. 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 1 m. For cramped conditions, it is allowed to take a distance of at least 0,25 m, but subject to the placement of cables in pipes or reinforced concrete trays with lids. 2.3.96. When crossing cable lines up to 35 kV heat pipelines, the distance between the cables and the overlap of the heat pipeline in the light must be at least 0,5 m, and in cramped conditions - at least 0,25 m. In this case, the heat pipeline at the intersection plus 2 m in each direction from the outermost cables must have such thermal insulation that the ground temperature does not rise by more than 10 ºС in relation to the highest summer temperature and by 15 ºС in relation to the lowest winter temperature. In cases where these conditions cannot be met, one of the following measures is allowed: deepening of cables to 0,5 m instead of 0,7 m (see 2.3.84.); use of a cable insert of a larger cross section; laying cables under the heat pipeline in pipes at a distance of at least 0,5 m from it, while the pipes must be laid in such a way that the cables can be replaced without excavation (for example, inserting pipe ends into chambers). When crossing a cable oil-filled line of a heat pipe, the distance between the cables and the overlap of the heat pipe must be at least 1 m, and in cramped conditions - at least 0,5 m. thermal insulation so that the temperature of the earth does not rise by more than 3ºС at any time of the year. 2.3.97. When cable lines cross railways and roads, cables must be laid in tunnels, blocks or pipes across the entire width of the exclusion zone at a depth of at least 1 m from the roadbed and at least 0,5 m from the bottom of drainage ditches. In the absence of an exclusion zone, the specified laying conditions must be met only at the intersection plus 2 m on both sides of the roadbed. When cable lines cross electrified and subject to 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 75-90º to the axis of the track. 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. * Agreed with the Ministry of Railways. 2.3.98. When cable lines cross tram tracks, cables must be laid in insulating blocks or pipes (see 2.3.90). The crossing must be carried out at a distance of at least 3 m from the switches, crosses and places where suction cables are attached to the rails. 2.3.99. When cable lines cross entrances for vehicles to yards, garages, etc., cables should be laid in pipes. In the same way, cables should be protected at the intersection of streams and ditches. 2.3.100. When installing cable boxes on cable lines, the clear distance between the cable box body and the nearest cable must be at least 250 mm. When laying cable lines on steep routes, the installation of cable boxes on them is not recommended. If it is necessary to install cable boxes in such sections, horizontal platforms must be made under them. To ensure the possibility of remounting the couplings in case of their damage on the cable line, it is required to lay the cable on both sides of the couplings with a margin. 2.3.101. If there are stray currents of dangerous values along the cable line route, it is necessary: 1. Change the route of the cable line in order to avoid dangerous areas. 2. If it is impossible to change the route: provide for measures to minimize the levels of stray currents; use cables with increased resistance to corrosion; to carry out active protection of cables from the effects of electrocorrosion. When laying cables in aggressive soils and areas with the presence of stray currents of unacceptable values, cathodic polarization should be used (installation of electrical drains, protectors, cathodic protection). For any method of connecting electrical drainage devices, the norms of potential differences in the suction sections, provided for by SNiP 3.04.03-85 "Protection of building structures and structures against corrosion" of the Gosstroy of Russia, must be observed. It is not recommended to use cathodic protection with external current on cables laid in saline soils or saline water bodies. The need to protect cable lines from corrosion should be determined 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.
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