2.3 15 rules for electrical installations. Requirements and prices for laying cables in the ground. Laying cable lines in cable blocks, pipes and reinforced concrete trays
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 units, power lines, busbars 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 are not considered in this chapter of the Rules.
Requirements for the protection of electrical networks up to 1 kV, electric motors, capacitor units, electrothermal units, see respectively in Chapter. 3.1, 5.3, 5.6 and 7.5.
Relay protection devices for electrical installation elements not discussed in this and other chapters must be made in accordance with 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 remaining, undamaged part electrical system(electrical installations) using switches; if there is a fault (for example, a ground fault in networks with isolated neutral) does not directly disrupt the operation of the electrical system; relay protection is allowed to act only on the signal.
b) responding to dangerous, abnormal operating conditions of electrical system elements (for example, overload, increased voltage in the stator winding of a hydrogenerator); Depending on the operating mode and operating conditions of the electrical installation, relay protection must be carried out to act on the signal or to disconnect those elements, which 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 fuse links should be used if they:
can be selected with the required parameters ( rated voltage and current, rated shutdown current, etc.);
provide the required selectivity and sensitivity;
do not interfere with the use of automation (automatic restart - automatic reclosure, automatic restart - automatic transfer switch, etc.), required by the operating conditions of the electrical installation.
When using fuses or open fuse links, depending on the level of asymmetry in the open-phase mode and the nature of the supplied load, the need to install protection against open-phase mode at the receiving substation should be considered.
3.2.4. Relay protection devices must ensure the shortest possible short circuit disconnection time in order to maintain uninterrupted operation of the undamaged part of the system ( stable work electrical system and electrical installations of consumers, ensuring the possibility of restoration normal operation through the successful operation of automatic reclosure and automatic transfer, self-starting of electric motors, pulling into synchronism, etc.) and limiting the area and degree of damage to the element.
3.2.5. Relay protection acting on shutdown, as a rule, must ensure selectivity of action, so that if any element of the electrical installation is damaged, only this damaged element is turned off.
Non-selective action of protection is allowed (correctable by subsequent action of automatic reclosure or automatic reclosure):
a) to ensure, if necessary, acceleration of short circuit tripping (see 3.2.4);
b) when using simplified main electrical diagrams with separators in the circuits of lines or transformers, disconnecting the damaged element during a dead time.
3.2.6. Relay protection devices with time delays that ensure selectivity of action are allowed if: when disconnecting a short circuit with time delays, the requirements of 3.2.4 are met; protection acts as a backup (see 3.2.15).
3.2.7. Reliable operation of relay protection (operation when conditions for operation appear and non-operation in their absence) must be ensured by the use of devices that, in their parameters and design, correspond to the intended purpose, as well as by proper maintenance of these devices.
If necessary, special measures should be used to improve operational reliability, in particular circuit redundancy, continuous or periodic condition monitoring, etc. The likelihood of erroneous actions should also be taken into account service personnel by doing necessary operations with relay protection.
3.2.8. If there is relay protection with voltage circuits, the following devices should be provided:
automatically disabling protection when circuit breakers are turned off, fuses blown and other voltage circuit violations (if these violations can lead to false positive 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 under other conditions (for example, during a short circuit outside the protected area).
3.2.9. When installing high-speed relay protection on power lines with tubular arresters, it must be detuned from the operation of the arresters, for which:
the shortest response time of the relay protection before the signal to turn off should be greater 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 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 against the initial value of current or resistance during a short circuit in order to exclude failures of protection operation (due to the attenuation of short-circuit currents over time, as a result of the occurrence of swings, the appearance of an arc at the site of damage, etc.).
3.2.11. Protection in electrical networks 110 kV and above must have devices that block their action during swings or asynchronous movement, if such swings or asynchronous movement are possible in the specified networks, during which the protection may be triggered unnecessarily.
It is allowed to use similar devices for lines below 110 kV connecting power sources to each other (based on the likelihood of swings or asynchronous movement and possible consequences unnecessary shutdowns).
It is allowed to perform protection without blocking during swings, if the protection is adjusted against swings in time (protection time delay is about 1.5-2 s).
3.2.12. The action of relay protection must be recorded by indicating relays, trip indicators built into the relay, trip counters or other devices to the extent necessary for recording and analyzing the operation of the protection.
3.2.13. Devices that record the action of relay protection on shutdown should be installed so that the action of each protection is signaled, and in case of complex protection - its individual parts (different stages of protection, separate sets of protection against different types damage, etc.).
3.2.14. Each element of the electrical installation must be provided with basic protection designed to operate in the event of damage within the entire protected element with a time shorter than that of other protections installed on this element.
3.2.15. To operate in the event of failures of protections or switches of adjacent elements, backup protection designed to provide long-term backup action should be provided.
If the main protection of an element has absolute selectivity (for example, high-frequency protection, longitudinal and transverse differential protection), then backup protection must be installed on this element, performing the functions of not only long-range, but also short-range backup, i.e., operating in the event of failure of the main protection of 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 protection of a line of 110 kV and above has relative selectivity (for example, step protection with time delays), then:
separate backup protection may not be provided, provided that the long-range backup effect of the protection of adjacent elements during a short circuit on this line is ensured;
measures must be taken to ensure short-range backup if long-range backup during a short circuit on this line is not provided.
3.2.16. For a power transmission line of 35 kV and above, in order to increase the reliability of disconnecting a fault at the beginning of the line, a current cut-off without a time delay can be provided as additional protection, provided that the requirements of 3.2.26 are met.
3.2.17. If full provision of long-range redundancy is associated with a significant complication of protection or is technically impossible, the following is allowed:
1) do not reserve short-circuit disconnections behind transformers, on reacted lines, lines of 110 kV and higher in the presence of close-range backup, at the end of a long adjacent section of a 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 cascade action of protection;
3) provide for non-selective action of protection during a short circuit on adjacent elements (with long-range backup action) with the possibility of de-energizing substations in some cases; at the same time, it is necessary, if possible, to ensure that these non-selective shutdowns are corrected by the action of an automatic reclosure or automatic transfer system.
3.2.18. Backup devices in case of breaker failure (breaker failure protection) must be provided in electrical installations of 110-500 kV. It is allowed not to provide for breaker failure protection in electrical installations of 110-220 kV, subject to the following conditions:
1) the required sensitivity and acceptable disconnection times from long-range backup devices under stability conditions are ensured;
2) when backup protections are in effect, there is no loss additional elements due to tripping of switches not directly adjacent to the failed switch (for example, there are no sectional buses or branches with branches).
At power plants with generators that have direct cooling of the conductors of the stator windings, in order to prevent damage to the generators in the event of failures of 110-500 kV circuit breakers, a breaker failure protection system should be provided regardless of other conditions.
If one of the switches of the damaged element (line, transformer, buses) of the electrical installation fails, the breaker failure protection system must act to disconnect the switches adjacent to the failed one.
If the protection is connected to remote current transformers, then the breaker failure protection must also operate during a short circuit in the area between these current transformers and the circuit breaker.
It is allowed to use simplified breaker failure protection systems that operate during short circuits with failures of switches not on all elements (for example, only during short circuits on lines); at a voltage of 35-220 kV, in addition, it is allowed to use devices that act only to disconnect the busbar (sectional) switch.
If 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 in the form of a separate set, it should be implemented, 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 protections must, as a rule, be powered from different secondary windings of the current transformers.
The power supply for the main and backup protection of power lines of 220 kV and above should, as a rule, be carried out from different automatic direct current circuit breakers.
3.2.20. The sensitivity of the main types of relay protection should be assessed using a sensitivity coefficient determined by:
for protections that respond to quantities that increase under damage conditions - as the ratio of the calculated values of these quantities (for example, current or voltage) during a metallic short circuit within the protected area to the protection operation parameters;
for protections that respond to values that decrease under damage conditions - as the ratio of response parameters to the calculated values of these quantities (for example, voltage or resistance) for a metal short circuit within the protected area.
The calculated values of the quantities should be established based on the most unfavorable types of damage, but for the realistically possible operating mode of the electrical system.
3.2.21. When assessing the sensitivity of basic protections, it is necessary to proceed from the fact that the following minimum sensitivity coefficients must be ensured:
1. Maximum current protection with and without voltage start, directional and non-directional, as well as current single-stage directional and non-directional protection, included in the negative or zero sequence components:
for current and voltage organs - about 1.5;
for negative and zero sequence power direction elements - about 2.0 in power and about 1.5 in current and voltage;
For maximum current protection For transformers with the lowest voltage of 0.23-0.4 kV, the lowest sensitivity factor can be about 1.5.
2. Step current or current and voltage protection, directional and non-directional, included on full current and and voltage or zero sequence components:
for the current and voltage elements of the protection stage intended to operate during 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 reliably operating selective backup stage - about 1.3; if there is separate bus protection at the opposite end of the line, the corresponding sensitivity coefficients (about 1.5 and about 1.3) for the zero-sequence protection stage can be provided in cascade shutdown mode;
for zero and negative sequence power direction elements - about 2.0 in power and about 1.5 in current and voltage;
for a power direction organ switched on at full current and voltage, it is not standardized in terms of power and about 1.5 in terms of current.
3. Distance protection against multiphase short circuits:
for a starting element of any type and a remote control of the third stage - about 1.5;
for a remote control of the second stage, designed to operate during 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 specified organ, the current sensitivity should be about 1.3 (relative to the current of precise operation) if damaged at the same point.
4. Longitudinal differential protection of generators, transformers, lines and other elements, as well as full differential protection of busbars - about 2.0; for the current starting element of incomplete differential distance protection of generator voltage buses, the sensitivity should be about 2.0, and for the first stage of incomplete differential current protection of generator voltage buses, made in the form of a cutoff, the sensitivity should be about 1.5 (with a short circuit on the busbars).
For differential protection of generators and transformers, sensitivity should be checked during short circuit on the terminals. In this case, regardless of the values of the sensitivity coefficient for hydrogenerators and turbogenerators with direct cooling of the winding conductors, the protection response current should be taken less than rated current generator (see 3.2.36). For autotransformers and step-up transformers with a power of 63 MVA or more, the operating current excluding braking is recommended to be taken less than the rated one (for autotransformers - less than the current corresponding to the typical power). For other transformers with a capacity of 25 MVA or more, the operating current without taking into account braking is recommended to take no more than 1.5 times the rated current of the transformer.
It is allowed to reduce the sensitivity coefficient for differential protection of a transformer or generator-transformer unit to a value of about 1.5 in the following cases (in which ensuring a sensitivity coefficient of about 2.0 is associated with a significant complication of protection or is technically impossible):
in case of short circuit on the low voltage terminals of 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 disconnected).
For the mode of supplying voltage to damaged buses, by turning on one of the power elements, it is possible to reduce the sensitivity coefficient for differential protection of buses to a value of about 1.5.
The specified coefficient of 1.5 also applies to the differential protection of the transformer during a short circuit behind the reactor installed on the low voltage side of the transformer and included in the zone of its differential protection. If there are other protections that cover the reactor and meet the sensitivity requirements for a short circuit behind the reactor, the sensitivity of the differential protection of the transformer during a short circuit at this point may not be provided.
5. Transverse differential directional protection of parallel lines:
for current relays and voltage relays of the starting element of protection kits against phase-to-phase short circuits and ground faults - about 2.0 when the switches are on on both sides of the damaged line (at the point of equal sensitivity) and about 1.5 when the switch is off on the opposite side of the damaged line;
for the zero sequence power direction element - about 4.0 in power and about 2.0 in current and voltage with the switches on on both sides and about 2.0 in power and about 1.5 in current and voltage with the switch off on the opposite side ;
for a power direction organ switched on at full current and voltage, the power is not standardized, but the current is about 2.0 when the switches are on on both sides and about 1.5 when the switch is off on the opposite side.
for the negative or zero sequence power direction element that controls the shutdown circuit - about 3.0 for power, about 2.0 for current and voltage;
7. Differential-phase high-frequency protection:
for starting elements that control the shutdown circuit - about 2.0 for current and voltage, about 1.5 for resistance.
8. Current cut-offs without time delay, installed on generators with a power of up to 1 MW and transformers, with a short circuit at the place where the protection is installed - about 2.0.
9. Protection against ground faults on cable lines in networks with an isolated neutral (acting on a signal or on shutdown):
for protections reacting to fundamental frequency currents - about 1.25;
for protections reacting to currents of high frequencies - about 1.5.
10. Protection against ground faults on overhead lines in networks with an isolated neutral, acting on a signal or on a shutdown, is 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 an inductive power direction relay is checked only when it is turned on for the components of negative and zero sequence currents and voltages.
2. The sensitivity of the power direction relay, made according to the comparison circuit (absolute values or phases), is checked: when turned on at full current and voltage - by current; when switching on the components of currents and voltages, negative and zero sequences - in current and voltage.
3.2.23. For generators operating on busbars, the sensitivity of current protection against ground faults in the stator winding acting on tripping is determined by its operation current, which should be no more than 5 A. As an exception, it is allowed to increase the operation current to 5.5 A.
For generators operating in a block with a transformer, the sensitivity coefficient of protection against single-phase faults to the ground, covering the entire stator winding, must be at least 2.0; to protect the zero-sequence voltage, which does not cover the entire stator winding, the operating voltage should be no more than 15 V.
3.2.24. The sensitivity of protection on alternating operating current, carried out according to the circuit with de-shunting of the tripping electromagnets, should be checked taking into account the actual current error of the current transformers after de-shunting. In this case, the minimum value of the sensitivity coefficient of the shutdown electromagnets, determined for the condition of their reliable operation, should be approximately 20% greater than that accepted for the corresponding protections (see 3.2.21).
3.2.25. The lowest sensitivity coefficients for backup protection during a short circuit at the end of an adjacent element or the most distant of several consecutive elements, included in the reservation zone, must be (see also 3.2.17):
for current, voltage, resistance organs - 1.2;
for negative and zero sequence power direction elements - 1.4 for power and 1.2 for current and voltage;
for a power direction organ switched on at 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 backup (see 3.2.15), one should proceed from the sensitivity coefficients given in 3.2.21 for the corresponding protections.
3.2.26. For current cut-offs without time delay, installed on lines and performing functions additional protections, the sensitivity coefficient should be about 1.2 for a short circuit at the protection installation site in the most favorable sensitivity mode.
3.2.27. If the action of the protection of a subsequent element is possible due to a failure due to insufficient sensitivity of the protection of the previous element, then the sensitivities of these protections must be coordinated with each other.
It is allowed not to coordinate the stages of these protections, intended for long-range backup, if failure to disconnect the short circuit due to insufficient sensitivity of the protection of the subsequent element (for example, negative sequence protection of generators, autotransformers) can lead to serious consequences.
3.2.28. In networks with a solidly grounded neutral, based on the conditions of relay protection, such a mode of grounding of the neutrals of power transformers (i.e., the placement of transformers with a grounded neutral) must be selected in which the values of currents and voltages during ground faults ensure the operation of relay protection of network elements under all possible operating modes of the electrical system.
For step-up transformers and transformers with two- and three-way power supply (or significant feeding from synchronous electric motors or synchronous compensators) with incomplete winding insulation on the neutral output side, as a rule, the occurrence of an unacceptable operating mode for them with an isolated neutral on separated buses must be excluded or a section of the 110-220 kV network with an earth fault of one phase (see 3.2.63).
3.2.29. Current transformers intended to power the current circuits of short-circuit relay protection devices must meet the following requirements:
1. In order to prevent unnecessary protection operations during a 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 protection (for example, differential tire protection with braking), right action which, in case of increased errors, is ensured through special measures. The following requirements must be met:
for stepped protection - in case of a short circuit at the end of the coverage area, the stage is protected, and for directional stepped protection - also in case of an external short circuit;
for other protections - with external short circuit.
For differential current protections (busbars, transformers, generators, etc.), the total error must be taken into account, for other protections - the current error, and when the latter is turned on for the sum of the currents of two or more current transformers and in external short-circuit mode - the total error.
When calculating permissible loads For current transformers, it is allowed to take the total error as the initial value.
2. The current error of current transformers in order to prevent protection failures during a 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 - values permissible for the selected type of relay;
according to the conditions of the maximum permissible for power direction relays and directional resistance relays angular error - 50%.
3. Voltage at terminals secondary winding current transformers during a short circuit in the protected area should not exceed the value permissible for the relay protection device.
3.2.30. Current circuits of electrical measuring instruments (together with meters) and relay protection must 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 disrupted, the switching on 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 the secondary circuit of the intermediate current transformers open.
3.2.31. Relay protection direct action, both primary and secondary, and protection on alternating operating current is recommended to be used, if possible and leads to simplification and reduction in cost of the electrical installation.
3.2.32. As a rule, current transformers of the protected element should be used as a source of alternating operational current for short-circuit protection. It is also possible to use voltage transformers or auxiliary transformers.
Depending on the specific conditions, one of the following schemes should be used: with deshunting the switches tripping electromagnets, using power supplies, using chargers with a capacitor.
3.2.33. Relay protection devices that are taken out of service due to network conditions, action selectivity or other reasons must have special devices to remove them from work by operational personnel.
To support operational checks and tests, protection circuits should provide test blocks or test terminals where necessary.
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 on the bottom and a layer of fine earth that does not contain stones on top, construction waste and slag.
The entire length of the cables must be protected from mechanical damage by coating at voltages of 35 kV and above reinforced concrete slabs not less than 50 mm thick; at voltages below 35 kV - slabs or clay ordinary brick in one layer across the cable route; when digging a trench with an earth-moving 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 laid at a depth of 1-1.2 m, cables of 20 kV and below (except for city power supply 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 surfaces of streets, etc. are considered as places where digging 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 in trenches with no more than two cable lines to use signal plastic tapes instead of bricks that satisfy technical requirements, approved by the USSR Ministry of Energy. It is not allowed to use warning tapes at the intersections of cable lines with utility lines and above cable couplings at a distance of 2 m in each direction from the crossed utility line or coupling, 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 line owner, it is allowed to expand the scope of application 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 placing one cable in a trench, the tape must be laid along the axis of the cable; with a larger number of cables, the edges of the tape must protrude beyond the outer cables by at least 50 mm. When laying more than one tape across the width of a trench, adjacent tapes must be laid with an overlap of at least 50 mm wide.
When using signal tape, laying cables in a trench with a cable cushion, 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 electrical networks.
When laying cable lines directly in the ground, the cables must be laid in trenches and have a backfill on the bottom and a layer of fine earth on top that does not contain stones, construction waste and slag.
Cables along their entire length must be protected from mechanical damage by covering them at voltages 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 earth-moving 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 laid at a depth of 1-1.2 m, cables of 20 kV and below (except for city power supply 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 surfaces of streets, etc. are considered as places where digging is carried out in rare cases. For cable lines up to 20 kV, except for lines above 1 kV that supply power receivers of category I*, 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 warning tapes at the intersections of cable lines with utility lines and above cable couplings at a distance of 2 m in each direction from the crossed utility line or coupling, 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 line owner, it is allowed to expand the scope of application 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 placing one cable in a trench, the tape must be laid along the axis of the cable; with a larger number of cables, the edges of the tape must protrude beyond the outer cables by at least 50 mm. When laying more than one tape across the width of a trench, adjacent tapes must be laid with an overlap of at least 50 mm wide.
When using signal tape, laying cables in a trench with a cable cushion, 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 electrical networks.
2.3.84
The depth of cable lines from the planning mark must be no less than: lines up to 20 kV 0.7 m; 35 kV 1 m; when crossing streets and squares, regardless of voltage 1 m.
Oil-filled cable 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 entering lines into buildings, as well as where they intersect 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 across arable land must be done at a depth of at least 1 m, while the strip of land above the route can be occupied for crops.
2.3.85
The clear distance from a 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 basements and technical undergrounds of residential and public buildings, one should be guided by the SNiP of the Gosstroy of Russia.
2.3.86
When laying cable lines in parallel, the horizontal clear distance 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;
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4) 500 mm between oil-filled cables 110-220 kV and other cables; in this case, 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 operating organizations, taking into account local conditions, to reduce 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 control cables is not standardized.
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 a green area with shrub plantings, the specified distances can be reduced to 0.75 m.
2.3.88
When laying in parallel, the horizontal clear distance from cable lines with voltages 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) - not less than 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, to 0.5 m without special cable protection and to 0.25 m when laying cables in pipes. For oil-filled cable lines 110-220 kV in a convergence section with a length of no 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 , eliminating the possibility of mechanical damage. Parallel laying of cables above and below pipelines is not permitted.
2.3.89
When laying a cable line parallel to 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 throughout the entire area of proximity to the cable line must have such thermal insulation so that additional heating of the ground by the heat pipe in the place where the cables pass does not occur at any time of the year. 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 parallel to railways, the cables must, as a rule, be laid outside the road exclusion zone. Laying cables within the exclusion zone is allowed only in agreement with organizations of the Ministry of Railways, and 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 permissible to reduce the specified distances, while the cables throughout the approach area must be laid in blocks or pipes.
With electrified roads on DC blocks or pipes must be insulating (asbestos-cement, impregnated with tar or bitumen, etc.)*.
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2.3.91
When laying a cable line parallel to tram tracks, the distance from the cable to the axis of the tram track must be at least 2.75 m. In cramped conditions, this distance can be reduced, provided that the cables throughout the approach area will be laid in insulating blocks or pipes specified in 2.3.90.
2.3.92
When laying a cable line parallel to roads of categories I and II (see 2.5.145), 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 curb stone. Reducing the specified distance is allowed in each individual case in agreement with the relevant road departments.
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 grounded parts and grounding conductors of overhead line supports 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 grounding conductors of individual supports of overhead lines above 1 kV are allowed at least 2 m; in this case, 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 supports (current conductors) and overhead lines above 1 kV, if the grounding devices of these supports are connected to the grounding loop of the substations.
2.3.94
*. When cable lines cross other cables, they must be separated by a layer of earth at least 0.5 m thick; this distance in cramped conditions for cables up to 35 kV can be reduced to 0.15 m, provided that the cables are separated throughout the entire intersection area plus 1 m in each direction with slabs or pipes made of concrete or other equal strength material; in this case, communication cables should be located higher power cables.
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* Agreed with the USSR 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. This distance can be reduced to 0.25 m, provided that the cable is laid at the intersection plus at least 2 m in each direction in pipes.
When an oil-filled cable line crosses pipelines, the clear distance between them must be at least 1 m. For cramped conditions, it is permissible to take a distance of at least 0.25 m, but provided that the cables are placed in pipes or reinforced concrete trays with lid.
2.3.96
When cable lines up to 35 kV cross heat pipes, the distance between the cables and the ceiling of the heat pipe in the clear 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 outer cables must have such thermal insulation that the temperature of the ground does not increase 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 the cables to 0.5 m instead of 0.7 m (see 2.3.84); use of a cable insert with 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 replacement of cables can be carried out without production earthworks(for example, inserting pipe ends into chambers).
When an oil-filled cable line crosses a heat pipe, the distance between the cables and the ceiling of the heat pipe must be at least 1 m, and in cramped conditions - at least 0.5 m. In this case, the heat pipe at the intersection plus 3 m in each direction from the outermost cables must have such thermal insulation so that the ground temperature does not rise by more than 5°C at any time of the year.
2.3.97
When cable lines cross railways and highways, the 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 road surface.
When cable lines cross electrified and subject to direct current* railways, the blocks and pipes must be insulating (see 2.3.90). The intersection must be at a distance of at least 10 m from the arrows, crosses and points of connection of suction cables to the rails. The intersection of cables with the tracks of electrified rail transport should be made at an angle of 75-90° to the axis of the track.
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* Agreed with the Ministry of Railways.
The ends of blocks and pipes must be recessed 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 paths (for example, on slips, etc.), cables, as a rule, should be laid directly in the ground.
When the route of cable lines crosses a newly constructed non-electrified railway or highway, relocation of existing cable lines is not required. At the intersection, they should be laid in case of repair of cables in required quantity reserve blocks or pipes with tightly sealed ends.
In the case of a transition of a cable line into an overhead line, the cable must exit to the surface at a distance of at least 3.5 m from the base of the embankment or from the edge of the canvas.
2.3.98
When cable lines cross tram tracks, the cables must be laid in insulating blocks or pipes (see 2.3.90). The intersection must be carried out at a distance of at least 3 m from the switches, crosses and points of connection of suction cables to the rails.
2.3.99
When cable lines cross vehicle entrances to courtyards, garages, etc., cables must be laid in pipes. Cables at intersections of streams and ditches should be protected in the same way.
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 steeply inclined routes, installing cable couplings on them is not recommended. If it is necessary to install cable joints in such areas, horizontal platforms must be made underneath them.
To ensure the possibility of reinstalling the couplings in the event of their damage on the cable line, it is necessary to lay the cable on both sides of the couplings with a reserve.
2.3.101
If there are stray currents of dangerous quantities along the cable line route, it is necessary to:
1. Change the cable line route in order to bypass dangerous areas.
2. If it is impossible to change the route: provide measures to minimize the levels of stray currents; use cables with increased resistance to corrosion; carry out active protection of cables from the effects of electrocorrosion.
When laying cables in aggressive soils and areas with stray currents of unacceptable values, cathodic polarization must be used (installation of electrical drains, protectors, cathodic protection). For any methods of connecting electrical drainage devices, the norms for potential differences in the suction areas provided for #M12291 871001027SNiP 3.04.03-85 #S "Protection of building structures and structures from corrosion" of the State Construction Committee of Russia. It is not recommended to use cathodic protection with external current on cables laid in saline soils or saline bodies of water.
The need to protect cable lines from corrosion should be determined based on the combined data of electrical measurements and chemical analyzes of soil samples. Protection of cable lines from corrosion should not create conditions that are 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. If there are stray currents in the ground, it is necessary to install on cable lines checkpoints in places and at distances that make it possible to determine 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.
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 carried out by control cables. Cable lines more high voltage carried out on special projects. Additional requirements for cable lines are given in Chapters 7.3, 7.4 and 7.7.
2.3.2. A cable line is a line for transmitting electricity or its individual pulses, consisting of one or more parallel cables with connecting, locking and end couplings (terminals) and fasteners, and for oil-filled lines, in addition, with feeding devices and an oil pressure alarm system.
2.3.3. A cable structure is a structure specifically designed to house cables, cable couplings, as well as oil-feeding devices and other equipment designed to ensure the normal operation of oil-filled cable lines. Cable structures include: cable tunnels, channels, ducts, blocks, shafts, floors, double floors, cable overpasses, galleries, chambers, feeding points.
A cable tunnel is a closed structure (corridor) with supporting structures located in it for placing cables and cable couplings on them, with free passage along the entire length, allowing for cable laying, repairs and inspections of cable lines.
A cable channel is a channel that is closed and buried (partially or completely) in the ground, floor, ceiling, etc. a non-passable structure designed to accommodate cables, the installation, inspection and repair of which can only be carried out with the ceiling removed.
A cable shaft is a vertical cable structure (usually rectangular in cross-section), the height of which is several times greater than the side of the section, equipped with brackets or a ladder for people to move along it (through shafts) or a completely or partially removable wall (non-through shafts).
A cable floor is a part of a building bounded by a floor and a ceiling or covering, with a distance between the floor and the protruding parts of the ceiling or covering of at least 1.8 m.
A double floor is a cavity bounded by the walls of a room, the interfloor ceiling and the floor of a room with removable slabs (over all or part of the area).
A cable block is a cable structure with pipes (channels) for laying cables in them with associated wells.
A cable chamber is an underground cable structure that is closed with a blind removable concrete slab, intended for laying cable sleeves 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 overhead or ground-based open horizontal or inclined extended cable structure. Cable overpass can be passable or non-passage.
A cable gallery is an above-ground or above-ground, fully or partially closed (for example, without side walls) horizontal or inclined extended cable passage 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. An oil-filled cable line of low or high pressure is a line in which the long-term permissible excess pressure 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 low-pressure oil-filled cable line section is the section of the line between the stop couplings or the stop and end couplings.
2.3.8. A feeding point is an above-ground, above-ground or underground structure with feeding devices and equipment (power tanks, pressure tanks, feeding units, etc.).
2.3.9. A branching device is the part of a high pressure cable line between the end of a steel pipeline and the single-phase end couplings.
2.3.10. A feeding unit is an automatically operating device consisting of tanks, pumps, pipes, bypass valves, taps, an automation panel and other equipment designed to provide oil replenishment to a high-pressure cable line.
General requirements
2.3.11. The design and construction of cable lines must 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 installation method, cable designs, etc.
2.3.12. When choosing a cable line route, you should, if possible, avoid areas with soils that are aggressive to the metal sheaths of cables (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 must be installed in the size of the area above the cables:
for cable lines above 1 kV, 1 m on each side of the outer cables;
for cable lines up to 1 kV, 1 m on each side of the outer cables, and when cable lines pass in cities under sidewalks - 0.6 m towards buildings and 1 m towards the roadway.
For submarine cable lines up to and above 1 kV, in accordance with the specified rules, a security zone must 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 cable line route should be selected taking into account the lowest cable consumption, ensuring its safety under mechanical stress, providing protection from corrosion, vibration, overheating and from damage to adjacent 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 feed tanks on the line.
2.3.15. Cable lines must be constructed in such a way that during installation and operation the occurrence of dangerous mechanical stresses and damage in them is excluded, for which:
cables must be laid with a reserve length sufficient to compensate for possible soil displacements 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 secured at the end points, directly at the end seals, on both sides of bends and at connecting and locking couplings;
cables laid vertically along structures and walls must be secured in such a way that deformation of the shells is prevented and the connections of the cores in the couplings are not broken under the influence of the cables’ own weight;
structures on which unarmored cables are laid must be made 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 using elastic gaskets;
cables (including armored ones) located in places where mechanical damage is possible (movement of vehicles, machinery and cargo, accessibility to 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 near other cables in operation, measures must be taken to prevent damage to the latter;
cables must be laid at a distance from heated surfaces that prevents heating of the cables above the permissible level, and protection of the cables from the breakthrough of hot substances in the places where valves and flange connections are installed must 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 from corrosion” of the State Construction Committee of Russia.
2.3.17. The designs of underground cable structures must be calculated taking into account the mass of cables, soil, road surface and load from passing traffic.
2.3.18. Cable structures and structures on which cables are laid must be made of fireproof materials. It is prohibited to install any temporary devices in cable structures or 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 effect of solar radiation, as well as heat radiation from various types of heat sources. When laying cables at latitudes greater than 65°, protection from solar radiation is not required.
2.3.20. The radii of the internal bending curve of cables must have a multiple of at least those specified in the standards or technical specifications for the corresponding brands of cables in relation to their outer diameter.
2.3.21. The radii of the internal bending curve of the cable cores when performing cable terminations must have, in relation to the given diameter of the cores, a multiple of not less than those specified in the standards or technical specifications for the corresponding brands of cables.
2.3.22. Tensile forces when laying cables and pulling them in pipes are determined by the mechanical stresses permissible for cores and sheaths.
2.3.23. Each cable line must have its own number or name. If a 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 terminations, must be equipped with tags indicating the brand, voltage, cross-section, number or name of the line on the tags of the cables and terminations; on the coupling tags - coupling numbers and installation dates. Tags must be resistant to impact environment. On cables laid in cable structures, tags must be located along the length at least every 50 m.
2.3.24. Security zones of cable lines laid underground 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. Information signs must indicate the width of the security zones of cable lines and the telephone numbers of cable line owners.
Selection 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. If there are a larger number of cables, it is recommended to lay them in separate trenches with a distance between groups of cables of at least 0.5 m or in channels, tunnels, overpasses and galleries.
2. Laying cables in tunnels, along 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 very tight spaces along the route, at intersections with railway tracks and driveways, when there is a possibility of a metal spill, etc.
4. When choosing methods for laying cables across urban areas, initial capital costs and costs associated with maintenance and repair work, as well as the convenience and cost-effectiveness of maintaining structures, should be taken into account.
2.3.26. In the territories of power plants, cable lines must be laid in tunnels, ducts, channels, blocks, along overpasses and in galleries. Laying power cables in trenches is allowed only to remote auxiliary facilities (fuel depots, workshops) with a number of no more than six. In the territories of power plants with a total capacity of up to 25 MW, laying cables in trenches is also allowed.
2.3.27. In the territories industrial enterprises Cable lines must be laid in the ground (in trenches), tunnels, blocks, channels, along overpasses, in galleries and along the walls of buildings.
2.3.28. In the areas of substations and switchgears Cable lines must 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 impassable parts of streets (under sidewalks), along courtyards and technical strips in the form of lawns.
2.3.30. In streets and squares saturated with underground communications, it is recommended to lay 10 or more cable lines in a stream in collectors and cable tunnels. When crossing streets and squares with improved surfaces and 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 the active layer in dry, well-draining soils, in artificial embankments made of coarse dry imported soils, in trays on the surface of the ground, on overpasses. It is recommended to jointly lay cables with pipelines for heating, water supply, sewerage, etc. in special structures (collectors).
2.3.32. The implementation of different 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 (rock, pebble, gravel, crushed stone and coarse sand); heaving and subsidence soils are unsuitable for laying cable lines in them. Cables can be laid directly in the ground if the number of cables is no more than four. Due to soil, permafrost and climatic conditions, laying cables in pipes laid in the ground is prohibited. At intersections with other cable lines, roads and underground communications, cables should be protected with reinforced concrete slabs.
Laying cables near buildings is not permitted. 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 may be used in places where the active layer consists of non-heaving soils and has flat surface with a slope of no more than 0.2%, ensuring surface water flow. Cable ducts should be made of waterproof reinforced concrete and covered on the outside reliable waterproofing. The channels must be covered from above with reinforced concrete slabs. Channels can be made buried in the ground or without burial (on top of the ground). In the latter case, a cushion with a thickness of at least 0.5 m of dry soil must be made under the channel and near it.
2.3.33. Inside buildings, cable lines can be laid directly along building structures (open and in boxes or pipes), in channels, blocks, tunnels, pipes laid in floors and ceilings, as well as along 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 method of laying them is determined by the project.
Cable selection
2.3.35. For cable lines laid along routes passing through various soils and environmental conditions, the choice of cable designs and sections should be made according to the section with the most severe conditions, if the length of sections with more easy conditions does not exceed the construction length of the cable. With a significant length of individual sections of the route with different conditions gaskets for each of them should be selected according to the design and cable cross-sections.
2.3.36. For cable lines laid along routes with different cooling conditions, cable sections must be selected according to 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 underwater, to use cables of different sections, but no more than three, provided that the length of the shortest segment is at least 20 m (see also 2.3.70).
2.3.37. For cable lines laid in land or water, armored cables should be used predominantly. The metal sheaths of these cables must have an outer covering to protect them from chemical attack. Cables with other designs of external protective coatings (unarmoured) must have the necessary resistance to mechanical stress when laid 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 oil-filled high-pressure cable lines laid in the ground 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 should be used or protected from mechanical damage.
Outside cable structures, it is allowed to lay not armored cables at an inaccessible height (at least 2 m); at a lower height, laying unarmored cables is permitted provided they are protected from mechanical damage (ducts, angle steel, pipes, etc.).
For mixed installation (ground - cable structure or industrial premises), it is recommended to use the same grades of cables as for installation in the ground (see 2.3.37), but without flammable outer protective coverings.
2.3.40. When laying cable lines in cable structures, as well as in industrial premises, armored cables should not have protective coverings made of flammable materials on top of the armor, and unarmored cables on top of metal sheaths.
For open installation, it is not allowed to use power and control cables with flammable polyethylene insulation.
The metal sheaths of cables and the metal surfaces on which they are laid must be protected with a non-flammable anti-corrosion coating.
When laying in rooms with an aggressive environment, cables that are 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-flammable coating. At power plants, the use of cables with flammable polyethylene insulation is not allowed.
2.3.42. For cable lines laid in cable blocks and pipes, as a rule, unarmored cables in a reinforced lead 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 covering of cable yarn. For cable lines laid in pipes, the use of cables in a plastic or rubber sheath is allowed.
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 materials, etc.), as well as in areas dangerous due to the effects of electrocorrosion, cables with lead sheaths must be used and reinforced protective covers, types, or cables with aluminum sheaths and especially reinforced protective covers, types, (in a continuous moisture-resistant plastic hose).
2.3.44. Where cable lines cross swamps, cables must be selected taking into account geological conditions, as well as chemical and mechanical influences.
2.3.45. For installation in soils subject to displacement, cables with wire armor must be used or measures must be taken to eliminate the forces acting on the cable when the soil moves (soil reinforcement with sheet piling or pile rows, etc.).
2.3.46. 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 over railway bridges, as well as 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 repeated bending 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 construction length. For this purpose, the use of single-core cables is permitted.
In places where cable lines pass from shore to sea in the presence of strong sea surf, when laying cables 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 polyvinyl chloride sheath, as well as cables in an aluminum sheath without special waterproof coatings, are not allowed for installation in water.
When laying cable lines through small non-navigable and non-floating rivers with a width (including the floodplain) of no more than 100 m, with a stable bed and bottom, the use of cables with tape armor is allowed.
2.3.50. For oil-filled cable lines with a voltage of 110-220 kV, the type and design of 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 that permissible 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. For the specified conditions, cables with viscous impregnation may only be used with stop couplings placed along the route, in accordance with the permissible level differences for these cables according to GOST.
The difference in vertical elevations between the locking couplings of low-pressure oil-filled cable lines is determined by the corresponding technical specifications for the cable and the calculation of recharge under extreme thermal conditions.
2.3.52. In four-wire networks, four-core cables must be used. Laying neutral conductors separately from phase conductors is not permitted. 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 wire) in four-wire AC networks (lighting, power and mixed) with a solidly grounded neutral, with the exception of installations with an explosive atmosphere and installations in which, under normal operating conditions, the current in the neutral wire is more than 75% of the permissible long-term current of the phase wire.
The use of lead sheaths of three-core power cables for this purpose is allowed only in reconstructed city electrical networks of 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 compared to three-core cables 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 parallel-connected cables and safe touching of their shells, preventing heating of those in the immediate vicinity metal parts and securely fastening cables in insulating clips.
Feeding devices and oil pressure signaling of cable oil-filled lines
2.3.54. The oil-feeding 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-feeding system must be determined taking into account the consumption for feeding the cable. In addition, there must be a supply of oil for emergency repairs and for filling the longest section of the cable line with oil.
2.3.56. Feeding tanks for low pressure lines are recommended to be placed in enclosed spaces. It is recommended to place a small number of feed tanks (5-6) at open feeding points in light metal boxes on portals, supports, etc. (at ambient temperature not lower than minus 30 °C). Feed tanks must be equipped with oil pressure indicators and protected from direct exposure to solar radiation.
2.3.57. Feeding units for high-pressure lines must be located in enclosed spaces with a temperature not lower than +10 °C, and located as close as possible to the point of connection to the cable lines (see also 2.3.131). Several feeding units are connected to the line through an oil manifold.
2.3.58. When laying several high-pressure oil-filled cable lines in parallel, it is recommended that each line be topped up 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. It is recommended that the feeding units be provided with electricity from two independent power sources with a mandatory automatic transfer switch (ATS) device. Feeding units must be separated from one another by fireproof partitions with a fire resistance rating of at least 0.75 hours.
2.3.60. Each oil-filled cable line must have an oil pressure alarm system that ensures registration and transmission to duty personnel of signals about a decrease or increase in oil pressure above permissible limits.
2.3.61. At least two sensors must be installed on each section of the low-pressure oil-filled cable line, and on the high-pressure line - a sensor on each feeding unit. Alarms must be transferred 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 centers (electricity network, 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 of the feeding unit should not exceed the permissible limits.
Connections and terminations of cables
2.3.65. When connecting and terminating power cables, coupling designs should be used that correspond to their operating conditions 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 accordance with the established procedure.
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.
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Armored and unarmoured cables indoors and outdoors in places where mechanical damage is possible (movement of vehicles, cargo and mechanisms, accessibility for unqualified personnel) must be protected to a safe height, but not less than 2 m from the ground or floor level and at a depth of 0 .3 m in the ground. (SNiP 3.05.06-85 "Electrical devices" clause 3.63.)
PUE clause 2.3.15 cables (including armored ones) located in places where mechanical damage is possible (movement of vehicles, machinery and cargo, accessibility for unauthorized persons) d.b. protected in height by 2 m from the floor or ground level and by 0.3 m in the ground
2.1.52 . Open gasket unprotected insulated wires directly on the bases, on rollers, insulators, on cables and trays, the following should be done:
1. For voltages above 42 V in rooms without increased danger and for voltages up to 42 V in any rooms - at a height of at least 2 m from the floor or service area.
2. For voltages above 42 V in high-risk and especially dangerous areas - at a height of at least 2.5 m from the floor or service area.
These requirements do not apply to descents to switches, sockets, starting devices, panels, lamps installed on the wall.
In industrial premises, descents of unprotected wires to switches, sockets, devices, panels, etc. must be protected from mechanical influences to a height of at least 1.5 m from the floor or service area.
In domestic premises of industrial enterprises, in residential and public buildings These slopes may not be protected from mechanical influences.
In rooms accessible only to specially trained personnel, the height of openly laid unprotected insulated wires is not standardized.
GOST R 50571.5.52-2011 Low-voltage electrical installations. Part 5-52. Selection and installation of electrical equipment. Electrical wiring
522.6 Impacts (AG)
522.6.1 Electrical wiring shall be selected and installed to minimize damage from mechanical external influences such as shock, penetration foreign bodies or compression during installation, operation or maintenance.
522.6.2 In fixed installations where moderate severity (AG2) or high severity (AG3) impacts may occur, protection shall be provided:
- mechanical characteristics electrical wiring; or
- choosing its location; or
- by additional local or general mechanical protection; or
- a combination of the above methods.
Notes
1. For example, areas under the floor in forklift operating areas.
2. Additional mechanical protection can be achieved by using appropriate cable fittings (ducts, pipes).
522.6.3 Cable installed under the floor or above the ceiling shall be installed in such a way as to prevent damage from contact with the floor or ceiling and/or elements for their fixation.
522.6.4 The level of protection of electrical equipment shall be maintained after cables and conductors are connected.
522.8 Other mechanical influences (AJ)
522.8.1 Electrical wiring shall be selected and installed in such a way as to prevent damage to the sheath and insulation of cables or insulated conductors, as well as their connections, during installation and operation.
Usage silicone lubricants for tightening and installation of cables and wires in pipes, placement in cable and special cable boxes, cable trays and cable ladders is not allowed.
522.8.2 When hidden electrical wiring In building structures, pipes or special cable ducts must be completely installed for each circuit before tightening insulated wires or cables into them.
522.8.3 The bend radius of wires and cables must be such that they do not cause damage when tightened.
522.8.4 When laying wires and cables on supporting structures with supports, the distance between the supports must be such as to prevent damage to the wires and cables from their own weight.
Note - Electrodynamic forces arising when short circuits, should be taken into account for single-core cables with a cross-sectional area greater than 50 mm.
522.8.5 For locations where electrical wiring is subject to constant tension (for example, tensile force on vertical sections of the route from its own weight), the appropriate type of cable or conductor of the required cross-section and installation method should be selected in order to prevent damage to the conductors and cables from their own weight.
522.8.6 Electrical wiring that involves the tightening and pulling of wires or cables shall be provided with appropriate means of access to perform such an operation.
522.8.7 Electrical wiring in floors shall be adequately protected to prevent damage during normal use of the floor.
Electrical wiring that is rigidly fixed and embedded in walls must be located horizontally, vertically or parallel to the edges of the walls of the room.
522.8.8 Electrical wiring laid in building structures without fastening may be located along the shortest path. Electrical wiring in ceilings may be located along the shortest path.
522.8.9 Electrical wiring shall be installed to avoid the application of mechanical forces to conductors and connections.
522.8.10 Cables, pipes or special conduits installed in the ground shall be provided with protection from mechanical damage or shall be installed underground at a depth that minimizes the risk of such damage. Cables laid underground must be marked with cable covers or suitable warning tape. Pipes and special ducts laid underground must be identified accordingly.
Notes
1. Requirements for underground pipes are given in IEC 61386-24.
2. Mechanical protection can be achieved by using underground pipes in accordance with IEC 61386-24, or by using armored cables or other suitable methods such as slab covering.
522.8.11 Cable shelves and their outer enclosures shall not have sharp edges that could damage cables or insulated conductors.
522.8.12 Cables and conductors shall not be damaged by means of securing.
522.8.13 Cables, buses and others electrical conductors that pass through expansion joints must be selected and installed in such a way that their movement will not cause damage to the electrical equipment, for example the use of a flexible wire connection.
522.8.14 If electrical wiring passes through a partition, it must be protected from mechanical damage, for example, by a metal sheath or the use of armored cables, or by using a pipe or O-ring.
Note - Electrical wiring is not allowed to pass through the element. building structure, which is designed to carry a load when the integrity of the load-bearing element cannot be guaranteed after the load has been applied.
(1 ratings, on average: 5,00 out of 5) 
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