PUE 7 Chapter 22: Conductors with voltage up to 35 kV (221-2240)

2.5.229

On overhead lines with wooden supports that are not protected by cables, on the supports that limit the crossing spans, protective devices must be installed on both intersecting overhead lines. The distances between the wires of intersecting overhead lines must be no less than those given in Table 2.5.24.

On the supports of overhead lines of 35 kV and below, when crossing them with overhead lines of 750 kV and below, it is allowed to use IP. At the same time, automatic restart must be provided for 35 kV overhead lines. Spark gaps on single-post and A-shaped supports with wooden traverses are made in the form of one grounding descent and end with bands at a distance of 75 cm (along the tree) from the point of attachment of the lower insulator. On U- and AP-shaped supports, grounding slopes are laid along two pillars of the supports to the traverse.

On overhead lines with wooden supports not protected by cables, when crossing them with a 750 kV overhead line, metal parts for fastening wires (hooks, pins, heads) must be grounded on supports limiting the span of the intersection, and the number of hanging insulators in the garlands must correspond to the insulation for metal supports In this case, protective devices must be installed on the supports of 35-220 kV overhead lines.

If the distance from the intersection to the nearest supports of intersecting overhead lines is more than 40 m, it is allowed not to install protective devices, and grounding of wire fastening parts on the supports of overhead lines of 35 kV and above is not required.

Installation of protective devices on intersection supports is not required:

for overhead lines with metal and reinforced concrete supports;

for overhead lines with wooden supports at a distance between the wires of intersecting overhead lines, not less than: 9 m - at a voltage of 750 kV; 7 m - at voltage 330-500 kV; 6 m - at voltage 150-220 kV; 5 m - at voltage 35-110 kV; 4 m - at voltages up to 20 kV.

The resistance of grounding devices of wooden supports with protective devices must be taken in accordance with Table 2.5.19.

UNDERWATER CABLE LINES

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

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

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

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

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

When laying oil-filled cable lines of 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 underwater cable lines must 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 speed not exceeding 1 m/s, the distance between the individual phases (without special phase fastenings to each other) is recommended to be at least 0.5 m, and the distance between the extreme cables of parallel lines - at least 5 m.

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

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

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

2.3.141. On banks without improved embankments, a reserve of at least 10 m in length for river installations and 30 m for sea installations must be provided at the location of the underwater cable crossing, which is laid in a figure eight pattern. On improved embankments, cables must be laid in pipes. As a rule, cable wells should be installed at the point where cables exit. The upper end of the pipe must go into the coastal well, and the lower end must be at a depth of at least 1 m from the lowest water level. In coastal areas, pipes must be firmly sealed.

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

2.3.143. Crossing cables with each other under water is prohibited.

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

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

4.2.134

Open switchgear and substations of 20-750 kV must be protected from direct lightning strikes. Protection against direct lightning strikes is not required for 20 and 35 kV substations with transformers with a unit capacity of 1.6 MVA or less, regardless of the number of such transformers and the number of thunderstorm hours per year, for all outdoor switchgear of 20 and 35 kV substation in areas with thunderstorm hours per year are no more than 20, as well as for outdoor switchgear and substation 220 kV and below at sites with an equivalent earth resistivity during the thunderstorm season of more than 2000 Ohm m with the number of thunderstorm hours per year not more than 20.

Buildings of closed switchgear and substations should be protected from direct lightning strikes in areas with more than 20 thunderstorm hours per year.

The protection of closed switchgear and substation buildings with metal roof coverings should be carried out by grounding these coverings. If there is a reinforced concrete roof and continuous electrical connection of its individual elements, protection is carried out by grounding its reinforcement.

The protection of closed switchgear and substation buildings, the roof of which does not have metal or reinforced concrete coverings with continuous electrical connection of its individual elements, should be carried out with rod lightning rods, or by laying a lightning protection mesh directly on the roof of the buildings.

When installing rod lightning rods on a protected building, at least two down conductors must be laid from each lightning rod on opposite sides of the building.

The lightning protection mesh must be made of steel wire with a diameter of 6-8 mm and laid on the roof directly or under a layer of non-combustible insulation or waterproofing. The grid should have cells with an area of ​​no more than 150 m (for example, a cell 12x12 m). The mesh nodes must be connected by welding. Down conductors connecting the lightning protection grid to the grounding device must be laid at least every 25 m around the perimeter of the building.

Metal and reinforced concrete (if there is at least part of the unstressed reinforcement) building structures should be used as down conductors. In this case, a continuous electrical connection from the lightning rod to the ground electrode must be ensured. Metal elements of the building (pipes, ventilation devices, etc.) should be connected to a metal roof or lightning protection mesh.

When calculating the number of reverse overlaps on a support, one should take into account the increase in the inductance of the support in proportion to the ratio of the distance along the down conductor from the support to the grounding to the distance from the grounding to the top of the support.

When entering into closed switchgears and substations of overhead lines through bushings located at a distance of less than 10 m from current conductors and other associated live parts, these inputs must be protected by RF or appropriate surge arresters. When connecting to the substation grounding mains at a distance of less than 15 m from power transformers, the conditions of 4.2.136 must be met.

For electrolysis buildings located on the territory of the substation, premises for storing hydrogen cylinders and installations with hydrogen receivers, the lightning protection mesh must have cells with an area of ​​no more than 36 m (for example, 6x6 m).

Protection of buildings and structures, including explosive and fire hazardous ones, as well as pipes located on the territory of power plants, is carried out in accordance with technical documentation approved in the prescribed manner.

2.5.131

When passing overhead lines of 110 kV and higher in areas with clayey, loamy, sandy loam and similar soils with a resistivity of 1000 Ohm m, reinforcement of reinforced concrete foundations, supports and stepsons should be used as natural grounding conductors without additional installation or in combination with laying artificial grounding conductors. In soils with higher resistivity, the natural conductivity of reinforced concrete foundations should not be taken into account, and the required resistance value of the grounding device should be ensured only by the use of artificial ground electrodes.

The required resistance of grounding devices of 35 kV overhead line supports must be ensured by the use of artificial grounding conductors, and the natural conductivity of foundations, underground parts of supports and stepsons (attachments) should not be taken into account in calculations.

3.4.3

In power plants and substations, control cables with semi-solid aluminum conductors should be used for secondary circuits. Control cables with copper conductors should only be used in secondary circuits:

1) power plants with generators with a capacity of more than 100 MW; at the same time, at power plants for secondary switching and lighting of chemical water treatment facilities, wastewater treatment, utility and auxiliary structures, mechanical workshops and start-up boiler houses, control cables with aluminum conductors should be used;

2) switchgear and substations with a higher voltage of 330 kV and above, as well as switchyards and substations included in intersystem transit power transmission lines;

3) differential protection of busbars and failure redundancy devices for 110-220 kV circuit breakers, as well as system emergency control equipment;

4) technological protection of thermal power plants;

5) with an operating voltage not higher than 60 V with a diameter of cable cores and wires up to 1 mm (see also 3.4.4);

6) power plants and substations located in explosive zones of classes BI and B-Ia.

In industrial plants, control cables with aluminum-copper or semi-solid aluminum conductors should be used for secondary circuits. Control cables with copper conductors should be used only in secondary circuits located in explosive zones of classes BI and B-Ia, in secondary circuits of mechanisms in blast furnace and converter shops, the main line of crimping and continuous high-performance rolling mills, electrical receivers of special group I category, as well as in secondary circuits with an operating voltage not higher than 60 V with a diameter of cable cores and wires up to 1 mm (see also 3.4.4).

Current conductors with voltage above 1 kV

2.2.28. In production premises, the use of conductors of design 1P41 and higher is allowed; the conductors must be located from the floor level or service area at a height of at least 2.5 m.

In industrial premises visited only by qualified service personnel (for example, in technical floors of buildings, etc.), the installation height of IP41 and higher conductors is not standardized.

In electrical premises, the use of conductors of any design is allowed. The installation height from the floor level or service platform for conductors of design below IP41 is not less than 2.5 m; IP41 and higher - not standardized.

2.2.29. Conductors of all designs can be used outdoors (see also 2.2.5 and 2.2.13).

2.2.30. When placing current conductors in tunnels and galleries, the requirements of 4.2.82 must be met, as well as the following requirements:

1. The width of service corridors for current conductors that do not have a sheath (IP00) must be at least: 1 m for a one-sided arrangement and 1.2 m for a double-sided arrangement. With a conductor length of more than 150 m, the width of the service corridor for both one-way and two-way equipment maintenance must be increased compared to the given one by at least 0.2 m.

2. The height of the fencing of current conductors that do not have a shell from the floor level must be at least 1.7 m.

3. At the beginning and at the end of the current conductor, as well as at intermediate points, stationary grounding blades or devices for connecting portable grounding should be provided. The number of portable grounding installation sites must be selected so that the voltage induced from adjacent conductors during a short circuit between two adjacent grounding installation points does not exceed 250 V.

2.2.31. In tunnels and galleries where current conductors are located, lighting must be provided in accordance with the requirements of Section. 6. Lighting of tunnels and galleries should be powered from two sources with alternating connections of lamps to both sources.

Where unsheathed conductors (IP00) are laid, lighting fixtures must be installed in such a way that they can be safely maintained. In this case, lighting wiring in tunnels and galleries must be shielded (cables with a metal sheath, electrical wiring in steel pipes, etc.).

2.2.32. When constructing tunnels and galleries for conductors, the following requirements must be met:

1. Structures must be made of fireproof materials. Load-bearing building structures made of reinforced concrete must have a fire resistance limit of at least 0.75 hours, and of rolled steel - at least 0.25 hours.

2. Ventilation must be such that the temperature difference between incoming and outgoing air at rated load does not exceed 15°C. Ventilation openings should be covered with blinds or nets and protected by canopies.

3. The interior of tunnels and galleries should not be crossed by any pipelines.

4. Tunnels and conductor galleries must be equipped with communication devices. Communication equipment and its installation locations must be determined during a specific design.

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

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

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

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

3.2.130

A separate protection panel, designed specifically for use instead of the line protection being tested, should be provided for electrical connection diagrams that do not have a bypass switch (for example, a quad, one and a half circuit, etc.); such a separate protection panel should be provided for 220 kV lines that do not have separate main protection; for lines 330-500 kV.

It is allowed to provide a separate protection panel for 110 kV lines that do not have separate main protection, with “bridge” electrical connection diagrams with switches in the line circuits and “polygon”, if, when checking the line protection, the damage on it is eliminated in accordance with the requirements by simpler means technically impossible.

Input devices, distribution boards, distribution points, group boards

7.1.22. A VU or ASU must be installed at the entrance to the building. One or more VU or ASU may be installed in a building.

If there are several economically separate consumers in a building, it is recommended that each of them install an independent VU or ASU.

The ASU is also allowed to supply power to consumers located in other buildings, provided that these consumers are functionally connected.

For branches from overhead lines with a rated current of up to 25 A, the VU or ASU may not be installed at the inputs to the building if the distance from the branch to the group panel, which in this case performs the functions of the VU, is no more than 3 m. This section of the network must be carried out with a flexible copper cable with with a conductor cross-section of at least 4 mm2, flame retardant, laid in a steel pipe, and the requirements for ensuring a reliable contact connection with the branch wires must be met.

For air input, surge suppressors must be installed.

7.1.23. Before entering buildings, it is not allowed to install additional cable boxes to separate the service scope of external supply networks and networks inside the building. Such separation must be carried out in the ASU or main switchboard.

7.1.24. VU, ASU, main switchboard must have protection devices on all inputs of supply lines and on all outgoing lines.

7.1.25. Control devices must be installed at the input of supply lines to the VU, ASU, and main switchboards. On outgoing lines, control devices can be installed either on each line, or be common to several lines.

A circuit breaker should be considered as a protection and control device.

7.1.26. Control devices, regardless of their presence at the beginning of the supply line, must be installed at the inputs of the supply lines in retail premises, utilities, administrative premises, etc., as well as in consumer premises that are administratively and economically isolated.

7.1.27. The floor panel must be installed at a distance of no more than 3 m along the length of the electrical wiring from the supply riser, taking into account the requirements of Chapter. 3.1.

7.1.28. VU, ASU, main switchboard, as a rule, should be installed in electrical switchboard rooms accessible only to maintenance personnel. In areas prone to flooding, they should be installed above the flood level.

VU, ASU, main switchboard can be located in rooms allocated in operational dry basements, provided that these rooms are accessible to maintenance personnel and are separated from other rooms by partitions with a fire resistance limit of at least 0.75 hours.

When placing VU, ASU, main switchboards, distribution points and group panels outside electrical switchboard rooms, they must be installed in places convenient and accessible for maintenance, in cabinets with an enclosure protection degree of at least IP31.

The distance from pipelines (water supply, heating, sewerage, internal drains), gas pipelines and gas meters to the installation site must be at least 1 m.

7.1.29. Electrical switchboard rooms, as well as VU, ASU, main switchboards, are not allowed to be located under toilets, bathrooms, showers, kitchens (except for apartment kitchens), sinks, washing and steam rooms of bathhouses and other rooms associated with wet technological processes, except in cases where Special measures have been taken for reliable waterproofing to prevent moisture from entering the premises where the switchgear is installed.

It is not recommended to lay pipelines (plumbing, heating) through electrical rooms.

Pipelines (plumbing, heating), ventilation and other ducts laid through electrical switchboard rooms should not have branches within the room (with the exception of a branch to the heating device of the switchboard room itself), as well as hatches, valves, flanges, valves, etc.

Laying gas and pipelines with flammable liquids, sewerage and internal drains through these premises is not permitted.

Doors to electrical rooms must open outward.

7.1.30. The premises in which ASUs and main switchboards are installed must have natural ventilation and electric lighting. The room temperature should not be lower than +5 oC.

7.1.31. Electrical circuits within the VU, ASU, main switchboard, distribution points, group panels should be made with wires with copper conductors.

2.5.238

When crossing an overhead line with an underground communication cable and a power supply (or with an underground cable insert), the following requirements must be met:

1) the angle of intersection of overhead lines up to 500 kV with LS and LPV is not standardized, the angle of intersection of 750 kV overhead lines with LS and LPV should be as close as possible to 90°, but not less than 45°;

2) the distance from underground cables LS and LPV to the nearest ground electrode of an overhead line support with voltage up to 35 kV or its underground metal or reinforced concrete part must be at least:

in populated areas - 3 m;

in uninhabited areas - the distances given in Table 2.5.26.

Table 2.5.26 Shortest distances from underground cables LS (LPV) to the nearest ground electrode of the overhead line support and its underground part

The distance from underground LAN and LPV cables to the underground part of an ungrounded wooden support of an overhead line with voltage up to 35 kV must be at least:

in populated areas - 2 m; in cramped conditions, the specified distance can be reduced to 1 m, provided that the cable is laid in a polyethylene pipe at a length on both sides of the support of at least 3 m;

in uninhabited areas: 5 m - with an equivalent earth resistivity of up to 100 Ohm m; 10 m - with an equivalent earth resistivity from 100 to 500 Ohm m; 15 m - with an equivalent earth resistivity from 500 to 1000 Ohm m; 25 m - with an equivalent earth resistivity of more than 1000 Ohm m;

3) the distance from the underground cables of LAN and LPV to the nearest ground electrode of the overhead line support of 110 kV and above and its underground part must be no less than the values ​​​​given in Table 2.5.26;

4) when laying an underground cable (cable insert) in steel pipes, or when covering it with a channel, an angle, or when laying it in a polyethylene pipe, closed on both sides from the ingress of earth, at a length equal to the distance between the overhead line wires plus 10 m with on each side from the outermost wires for overhead lines up to 500 kV and 15 m for overhead lines 750 kV, it is allowed to reduce the distances indicated in Table 2.5.26 to 5 m for overhead lines up to 500 kV and up to 10 m for 750 kV.

In this case, the metal covers of the cable should be connected to a pipe or other metal protective elements. This requirement does not apply to optical cables and cables with an external insulating hose, including those with a metal sheath. The metal covers of the cable insert must be grounded at the ends. When reducing the distances between the cable and the overhead line supports specified in Table 2.5.26, in addition to the given protection measures, it is necessary to install additional protection against lightning strikes by lining the supports with cables in accordance with the requirements of regulatory documentation for the protection of cables from lightning strikes;

5) instead of using a channel, angle or steel pipe, when constructing a new overhead line, it is allowed to use two steel cables with a cross-section of 70 mm, laid symmetrically at a distance of no more than 0.5 m from the cable and at a depth of 0.4 m. The cables must be extended on both sides at an angle of 45° to the route towards the overhead line support and grounded to a resistance of no more than 30 Ohms. The relationship between the length of the cable outlet and the grounding resistance must correspond to the values ​​and given in Table 2.5.27;

Table 2.5.27 Resistance of grounding conductors when protecting LAN and LPV cables at the intersection with overhead lines

Electrical Installation Rules (ELI) 7th edition. Chapter 1.3.

Section 1. General rules Chapter 1.3.
Selection of conductors based on heating, economic current density and corona conditions Scope of application 1.3.1.
This chapter of the Rules applies to the selection of cross-sections of electrical conductors (bare and insulated wires, cables and buses) for heating, economic current density and corona conditions. If the cross-section of the conductor determined according to these conditions is less than the cross-section required by other conditions (thermal and electrodynamic resistance to short-circuit currents, voltage losses and deviations, mechanical strength, overload protection), then the largest cross-section required by these conditions should be accepted.

Selection of heating conductor cross-sections

1.3.2.

Conductors for any purpose must meet the requirements for maximum permissible heating, taking into account not only normal, but also post-emergency conditions, as well as conditions during repairs and possible uneven distribution of currents between lines, bus sections, etc. When checking for heating, a half-hour maximum is accepted current, the largest of the average half-hour currents of a given network element.

1.3.3.

For intermittent and short-term operating modes of electrical receivers (with a total cycle duration of up to 10 minutes and an operating period of no more than 4 minutes), the current reduced to the long-term mode should be taken as the calculated current for checking the cross-section of heating conductors. Wherein:

1. for copper conductors with a cross-section of up to 6 mm2, and for aluminum conductors up to 10 mm2, the current is taken as for installations with long-term operation;
2. for copper conductors with a cross-section of more than 6 mm2, and for aluminum conductors with a cross-section of more than 10 mm2, the current is determined by multiplying the permissible long-term current by a factor of 0.875 / √ T
   PV, where
   T
   PV is the duration of the operating period expressed in relative units (on duration in relation to the cycle duration).

1.3.4.

For a short-term operating mode with a switching duration of no more than 4 minutes and breaks between switching on sufficient to cool the conductors to ambient temperature, the maximum permissible currents should be determined according to the standards of the short-term operating mode (see 1.3.3). When the duration of switching on is more than 4 minutes, as well as during breaks of insufficient duration between switching on, the maximum permissible currents should be determined as for installations with a long operating mode.

1.3.5.

For cables with voltages up to 10 kV with impregnated paper insulation that carry less than rated loads, a short-term overload indicated in table may be allowed. 1.3.1.

1.3.6.

For the period of liquidation of the post-emergency regime, an overload of up to 10% is allowed for cables with polyethylene insulation, and for cables with polyvinyl chloride insulation up to 15% of the rated load during maximum loads lasting no more than 6 hours per day for 5 days, if the load during the remaining periods of time of these days does not exceed the nominal.

During the period of liquidation of the post-emergency regime, overloads are allowed for 5 days for cables with voltages up to 10 kV with paper insulation. within the limits specified in table. 1.3.2.

Table 1.3.1. Permissible short-term overload for cables with voltages up to 10 kV with impregnated paper insulation

Table 1.3.2. Permissible overload for the period of post-emergency liquidation for cables with voltage up to 10 kV with paper insulation

For cable lines that have been in operation for more than 15 years, overloads should be reduced by 10%.

Overloading cable lines with a voltage of 20-35 kV is not allowed.

1.3.7.

The requirements for normal loads and post-accident overloads apply to cables and the connecting and termination couplings and terminations installed on them.

1.3.8.

Zero working conductors in a four-wire three-phase current system must have a conductivity of at least 50% of the conductivity of the phase conductors; if necessary, it should be increased to 100% of the conductivity of the phase conductors.

1.3.9.

When determining permissible long-term currents for cables, bare and insulated wires and busbars, as well as for rigid and flexible conductors laid in an environment whose temperature differs significantly from that given in 1.3.12-1.3.15 and 1.3.22. the coefficients given in table should be applied. 1.3.3.

Table 1.3.3. Correction factors for currents for cables, bare and insulated wires and busbars depending on ground and air temperatures

Permissible long-term currents for wires, cords and cables with rubber or plastic insulation
1.3.10.
Permissible long-term currents for wires with rubber or polyvinyl chloride insulation, cords with rubber insulation and cables with rubber or plastic insulation in lead, polyvinyl chloride and rubber sheaths are given in Table.
1.3.4-1.3.11. They are accepted for temperatures: cores + 65, ambient air + 25 and ground + 15°C.
When determining the number of wires laid in one pipe (or cores of a stranded conductor), the neutral working conductor of a four-wire three-phase current system

, as well as
grounding and neutral protective conductors into account .
The data contained in the table. 1.3.4 and 1.3.5 should be applied regardless of the number of pipes and the location of their installation (in the air, floors, foundations).

Permissible long-term currents for wires and cables laid in boxes, as well as in trays in bundles, must be accepted: for wires - according to table. 1.3.4 and 1.3.5 as for wires laid in pipes, for cables - according to table. 1.3.6-1.3.8 as for cables laid in the air.

If the number of simultaneously loaded wires is more than four, laid in pipes, boxes, and also in trays in bundles, the currents for the wires should be taken according to the table. 1.3.4 and 1.3.5 as for wires laid openly (in the air), with the introduction of reduction factors of 0.68 for 5 and 6; 0.63 for 7-9 and 0.6 for 10-12 conductors.

For secondary circuit wires, reduction factors are not introduced.

Table 1.3.4. Permissible continuous current for wires and cords with rubber and polyvinyl chloride insulation with copper conductors

Table 1.3.5. Permissible continuous current for rubber and polyvinyl chloride insulated wires with aluminum conductors

Table 1.3.6. Permissible continuous current for wires with copper conductors with rubber insulation in metal protective sheaths and cables with copper conductors with rubber insulation in lead, polyvinyl chloride, nayrite or rubber sheaths, armored and unarmored

* Currents apply to wires and cables both with and without a neutral core.
Table 1.3.7. Permissible continuous current for cables with aluminum conductors with rubber or plastic insulation in lead, polyvinyl chloride and rubber sheaths, armored and unarmored

* Note.
Permissible continuous currents for four-core cables with plastic insulation for voltages up to 1 kV can be selected according to table. 1.3.7, as for three-core cables, but with a coefficient of 0.92. Table 1.3.8. Permissible continuous current for portable light and medium-sized hose cords, portable heavy-duty hose cables, mine flexible hose cables, spotlight cables and portable wires with copper cores and

* Currents refer to cords, wires and cables with and without a neutral core
Table 1.3.9. Permissible continuous current for portable hose cables with copper conductors and rubber insulation for peat enterprises

* Currents refer to cables with and without a neutral core.
Table 1.3.10. Permissible continuous current for hose cables with copper conductors and rubber insulation for mobile electrical receivers in

* Currents refer to cables with and without a neutral core.
Table 1.3.11. Permissible continuous current for wires with copper conductors with rubber insulation for electrified transport 1.3 and 4 kV

Table 1.3.12. Reduction factor for wires and cables laid in boxes

1.3.11.

Permissible long-term currents for wires laid in trays, when laid single-row (not in bundles), should be taken as for wires laid in the air.

Permissible long-term currents for wires and cables laid in boxes should be taken according to table. 1.3.4-1.3.7 as for single wires and cables laid openly (in the air), using the reduction factors indicated in table. 1.3.12.

When choosing reduction factors, control and reserve wires and cables are not taken into account.

Permissible long-term currents for cables with impregnated paper insulation
1.3.12.
Permissible continuous currents for cables with voltages up to 35 kV with insulation made of impregnated cable paper in a lead, aluminum or polyvinyl chloride sheath are accepted in accordance with the permissible temperatures of the cable cores:

1.3.13.

For cables laid in the ground, permissible long-term currents are given in table. 1.3.13, 1.3.16, 1.3.19-1.3.22. They are taken on the basis of laying no more than one cable in a trench at a depth of 0.7-1.0 m at a ground temperature of + 15 ° C and a ground resistivity of 120 cm•K/W

Table 1.3.13. Permissible long-term current for cables with copper conductors with paper impregnated with oil rosin and non-drip insulation in a lead sheath, laid in the ground

Table 1.3.14. Permissible continuous current for cables with copper conductors with paper impregnated with oil rosin and non-drip insulation in a lead sheath, laid in water

Table 1.3.15. Permissible continuous current for cables with copper conductors with paper impregnated with oil rosin and non-drip insulation in a lead sheath, laid in the air

Table 1.3.16. Permissible continuous current for cables with aluminum conductors with paper impregnated with oil rosin and non-drip insulation in a lead or aluminum sheath, laid in the ground

Table 1.3.17. Permissible continuous current for cables with aluminum conductors with paper impregnated with oil rosin and non-drip insulation in a lead sheath, laid in water

Table 1.3.18. Permissible continuous current for cables with aluminum conductors with paper impregnated with oil rosin and non-drip insulation in a lead or aluminum sheath, laid in the air

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2.5.122

The fastening of cables on all supports of 220-750 kV overhead lines must be done using insulators, shunted by IP with a size of at least 40 mm.

On each anchor section up to 10 km long, the cables must be grounded at one point by installing special jumpers on the anchor support. For longer anchor spans, the number of grounding points in the span is selected so that at the highest value of the longitudinal electromotive force induced in the cable during a short circuit (short circuit) on the overhead line, breakdown of the IP does not occur.

It is recommended to use glass suspension insulators to insulate the cable.

On the approaches of 220-330 kV overhead lines to substations at a length of 1-3 km and on the approaches of 500-750 kV overhead lines on a length of 3-5 km, if the cables are not used for capacitive selection, ice melting or communication, they should be grounded at each support ( see also 2.5.192).

On overhead lines of 150 kV and below, if melting of ice or organization of high-frequency communication channels on the cable is not provided, insulated fastening of the cable should be performed only on metal and reinforced concrete anchor supports.

In areas of overhead lines with non-insulated cable fastening and a short-circuit current to ground exceeding 15 kA, as well as on approaches to substations, the grounding of the cable must be carried out with the installation of a jumper that bypasses the clamp.

When using cables to install high-frequency communication channels, they are isolated from supports along the entire length of high-frequency communication channels and grounded at substations and amplification points through high-frequency barriers.

The number of insulators in the supporting cable fastening must be at least two and determined by the conditions for ensuring the required reliability of high-frequency communication channels. The number of insulators in the tension cable fastening should be doubled compared to the number of insulators in the supporting cable fastening.

The insulators on which the cable is suspended must be bridged by a spark gap. The size of the individual entrepreneur is selected as small as possible according to the following conditions:

1) the discharge voltage of the IP must be at least 20% lower than the discharge voltage of the insulating cable fastening;

2) The power supply should not overlap during a single-phase short circuit to ground on other supports;

3) when the power supply is interrupted by lightning discharges, the arc of the accompanying power frequency current should self-extinguish.

On 500-750 kV overhead lines, to improve the conditions for self-extinguishing the arc of the accompanying power frequency current and reduce electricity losses, it is recommended to use crossing cables.

If melting of ice is provided on overhead line cables, then insulated fastening of the cables is carried out along the entire melting area. At one point in the melting section, the cables are grounded using special jumpers. Rope insulators are shunted by power supply, which must be minimal, withstand the melting voltage and have a discharge voltage less than the discharge voltage of the cable garland. The size of the power supply must ensure self-extinguishing of the arc of the accompanying power frequency current when it is blocked during a short circuit or lightning discharges.

2.5.284

Distances when crossing, approaching and paralleling with overhead and ground pipelines and cable cars must be no less than those given in Table 2.5.39*.

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* The relative location of pipelines, their buildings, structures and outdoor installations and overhead lines included in the pipelines is determined by departmental standards.

Vertical distances in normal operation of overhead lines must be taken no less than the values ​​given in Table 2.5.39:

at the highest air temperature, without taking into account heating of the wires by electric current, the distances should be taken as for overhead lines of 500 kV and below;

at air temperature according to 2.5.17 without taking into account the heating of the wire by electric current at the maximum permissible values ​​of the intensity of the electric and magnetic components of the electromagnetic field - for a 750 kV overhead line;

at the calculated linear ice load according to 2.5.55 and air temperature during ice conditions - according to 2.5.51.

In emergency mode, distances are checked for overhead lines with wires with a cross-sectional area of ​​the aluminum part of less than 185 mm at an average annual temperature, without ice and wind; For overhead lines with wires with a cross-sectional area of ​​the aluminum part of 185 mm or more, checking when a wire breaks is not required.

The route of an overhead line with a voltage of 110 kV and higher, when running in parallel with the technical corridors of above-ground and above-ground main oil pipelines and petroleum product pipelines, should, as a rule, pass on terrain with relief marks higher than the marks of the technical corridors of main oil pipelines and petroleum product pipelines. In the regions of Western Siberia and the Far North*, when running parallel overhead lines of 110 kV and higher with technical corridors of above-ground and above-ground main gas pipelines, oil pipelines, oil product pipelines and ammonia pipelines, the distance from the axis of the overhead line to the outermost pipeline must be at least 1000 m.

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* Hereinafter, the regions of Western Siberia include the oil and gas producing regions of the Tyumen and Tomsk regions and the Yamalo-Nenets and Khanty-Mansiysk districts and the regions of the Far North - the territory included in this concept by the Resolution of the Council of Ministers of the USSR dated 10.10.67.

7.1.88

All open conductive parts of stationary electrical installations, third-party conductive parts and neutral protective conductors of all electrical equipment (including plug sockets) must be connected to the additional potential equalization system.

For bathrooms and shower rooms, an additional potential equalization system is mandatory and must include, among other things, the connection of third-party conductive parts extending outside the premises. If there is no electrical equipment with neutral protective conductors connected to the potential equalization system, then the potential equalization system should be connected to the PE bus (clamp) at the input. Heating elements embedded in the floor must be covered with a grounded metal mesh or a grounded metal shell connected to a potential equalization system. As additional protection for heating elements, it is recommended to use an RCD with a current of up to 30 mA.

It is not allowed to use local potential equalization systems for saunas, baths and shower rooms.

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7.3.135

In electrical installations up to 1 kV with a solidly grounded neutral, grounding of electrical equipment must be carried out:

a) in power networks in explosive zones of any class - a separate residential cable or wire;

b) in lighting networks in explosive zones of any class, except for class BI, - in the area from the luminaire to the nearest branch box - with a separate conductor connected to the neutral working conductor in the branch box;

c) in lighting networks in an explosive zone of class BI - with a separate conductor laid from the luminaire to the nearest group panel;

d) on the network section from the switchgear and transformer substations located outside the explosive zone to the switchboard, assembly, distribution point, etc., also located outside the explosive zone, from which power is supplied to electrical receivers located in explosive zones of any class, is allowed as For the neutral protective conductor, use the aluminum sheath of the power cables.