P 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

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 is 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 the general requirements of this chapter.

General requirements

3.2.2. Electrical installations must be equipped with relay protection devices designed for:

a) automatic disconnection of the damaged element from the rest of the undamaged part of the electrical system (electrical installation) 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, fuses or open fuse links should be used instead of circuit breakers and relay protection 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 reclosure - automatic reclosure, automatic switching on of a reserve - 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 shutdown time in order to maintain uninterrupted operation of the undamaged part of the system (stable operation of the electrical system and electrical installations of consumers, ensuring the possibility of restoring normal operation through the successful operation of automatic reclosure and automatic transfer switches, self-starting of electric motors, synchronization, etc.) and restrictions on 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 circuits 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 when performing 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 operation of the 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 protection 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 point of damage and etc.).

3.2.11. Protections in electrical networks of 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 these networks, during which the protection may be triggered unnecessarily.

It is also possible to use similar devices for lines below 110 kV connecting power supplies (based on the likelihood of swings or asynchronous movement and the possible consequences of 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 of 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 protection is in effect, there is no loss of additional elements due to the disconnection 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 of transformers with low voltage 0.23-0.4 kV, the lowest sensitivity factor can be about 1.5.

2. Step protection of current or current and voltage, directional and non-directional, included for full currents and voltages or for 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 the rated current of the 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 ground faults 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 remote of several consecutive elements included in the redundancy zone should 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 a time delay, installed on lines and performing the functions of additional protection, the sensitivity coefficient should be about 1.2 for a short circuit at the place where the protection is installed 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 deaf grounded neutral This mode of neutral grounding should be selected based on the conditions of relay protection power transformers(i.e. placement of transformers with a grounded neutral), 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 a 110-220 kV network with a single phase ground fault (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 protection of tires with braking), the correct operation of 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 angular error for power direction relays and directional resistance relays - 50%.

3. The voltage at the terminals of the secondary winding of 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. Protection using direct action relays, 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, selectivity of action or for other reasons must have special devices for taking them out of service by operating personnel.

To support operational checks and tests, protection circuits should provide test blocks or test terminals where necessary.

Protection of turbogenerators operating directly on generator voltage busbars 1

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1 The requirements given in 3.2.34-3.2.50 can be followed for other generators.

3.2.34. For turbogenerators above 1 kV with a power of more than 1 MW, operating directly on the generator voltage busbars, relay protection devices must be provided against the following types of damage and disruptions to normal operation:

1) multiphase short circuits in the generator stator winding and at its terminals;

2) single-phase ground faults in the stator winding;

3) double ground faults, one of which occurred in the stator winding, and the second in the external network;

4) short circuits between turns of one phase in the stator winding (in the presence of parallel branches of the winding);

5) external short circuits;

6) overload with negative sequence currents (for generators with a capacity of more than 30 MW);

7) symmetrical overload of the stator winding;

8) overload of the rotor winding with excitation current (for generators with direct cooling of the winding conductors);

9) ground fault at the second point of the excitation circuit;

10) asynchronous mode with loss of excitation (in accordance with 3.2.49).

3.2.35. For turbogenerators above 1 kV with a power of 1 MW or less, operating directly on the generator voltage busbars, a relay protection device should be provided in accordance with 3.2.34, paragraphs 1-3, 5, 7.

For turbogenerators up to 1 kV with a power up to 1 MW, operating directly on the generator voltage busbars, protection is recommended to be carried out in accordance with 3.2.50.

3.2.36. To protect against multiphase faults in the stator winding of turbogenerators above 1 kV with a power of more than 1 MW, with individual phase terminals on the neutral side, longitudinal differential current protection must be provided (for an exception, see 3.2.27). The protection should act to turn off all generator switches, to extinguish the field, and also to stop the turbine.

In addition to the generator, the protection coverage area should include the connections of the generator with the busbars of the power plant (up to the circuit breaker).

Longitudinal differential current protection must be performed with an operating current of no more than 0.6 IN.

For generators with a power of up to 30 MW with indirect cooling, it is allowed to perform protection with an operating current of 1.3-1.4 IN.

Fault monitoring of current protection circuits should be provided when the protection operation current is more than IN.

Longitudinal differential current protection must be carried out with detuning from transient values ​​of unbalance currents (for example, relays with saturable current transformers).

Protection should be three-phase three-relay. For generators with a power of up to 30 MW, protection can be performed using two-phase, two-relay protection if there is protection against double ground faults.

3.2.37. To protect against multiphase faults in the stator winding of generators above 1 kV with a power of up to 1 MW, operating in parallel with other generators or the electric power system, a current cut-off without a time delay must be provided, installed from the generator terminals to the busbars. If the current cut-off does not satisfy the sensitivity requirements, it is allowed to install longitudinal differential current protection instead.

The use of current cut-off instead of differential protection is also allowed for generators of higher power that do not have phase terminals on the neutral side.

For single-operating generators above 1 kV with a power up to 1 MW, protection against external short-circuits should be used as protection against multi-phase faults in the stator winding (see 3.2.44). The protection should act to turn off all generator switches and extinguish its field.

3.2.38. To protect generators above 1 kV from single-phase ground faults in the stator winding with a natural capacitive ground fault current of 5 A or more (regardless of the presence or absence of compensation), current protection must be provided that responds to full current short circuit to ground or its components of higher harmonics. If necessary, to turn it on, zero-sequence current transformers can be installed directly at the generator terminals. The use of protection is also recommended for capacitive ground fault currents of less than 5 A. The protection must be adjusted against transient processes and act as in 3.2.36 or 3.2.37.

When the earth fault protection is not installed (since it is insensitive at a capacitive earth fault current of less than 5 A) or does not operate (for example, when compensating for capacitive current in a generator voltage network), the installed on the busbars and an insulation monitoring device acting on the signal.

3.2.39. When installing a zero-sequence current transformer on generators for protection against single-phase ground faults, current protection against double ground faults must be provided, connected to this current transformer.

To increase the reliability of operation when large values current, a relay with a saturable current transformer should be used. This protection shall be carried out without a time delay and shall act as the protection specified in 3.2.36 or 3.2.37.

3.2.40. To protect against short circuits between the turns of one phase, a single-system transverse differential current protection without time delay must be provided in the stator winding of a generator with parallel branches, acting as the protection specified in 3.2.36.

3.2.41. To protect generators with a power of more than 30 MW from currents caused by external asymmetrical short circuits, as well as from overload with negative sequence current, negative sequence current protection should be provided, operating on a trip with two time delays (see 3.2.45).

For generators with direct cooling of winding conductors, protection should be performed with a step or dependent time delay characteristic. In this case, the step and dependent characteristics at the second (higher) time delays should not be higher than the characteristics of permissible generator overloads with negative sequence current.

For generators with indirect cooling of winding conductors, protection should be performed with an independent time delay with an operating current not exceeding that permissible for the generator when a negative sequence current passes through it for 2 minutes; A shorter protection time delay should not exceed the permissible duration of a two-phase short circuit at the generator terminals.

Negative sequence current protection acting on tripping must be supplemented by a more sensitive element acting on a definite time delay signal. The operating current of this element should be no more than the permissible negative sequence current for a given type of generator.

3.2.42. To protect generators with a power of more than 30 MW from external symmetrical short circuits, maximum current protection with a minimum voltage start-up must be provided, performed by one current relay connected to the phase current, and one minimum voltage relay connected to the phase-to-phase voltage. The protection trip current should be about 1.3-1.5 IN, and the response voltage is about 0.5-0.6 Unom.

On generators with direct cooling of winding conductors, instead of the specified protection, single-relay distance protection can be installed.

3.2.43. To protect generators with a power of more than 1 MW to 30 MW from external short circuits, maximum current protection should be used with a combined voltage start, made with one minimum voltage relay connected to the phase-to-phase voltage, and one negative sequence voltage filter relay device, breaking the circuit of the minimum voltage relay .

The protection response current and the response voltage of the minimum voltage element should be taken equal to those specified in 3.2.42, the response voltage of the negative sequence voltage filter-relay device is 0.1-0.12 Unom.

3.2.44. For generators above 1 kV with a power up to 1 MW, maximum current protection must be used as protection against external short circuits, connected to the current transformers on the neutral side. The protection setting should be selected according to the load current with the necessary margin. It is also possible to use simplified minimum voltage protection (without a current relay).

3.2.45. Protection of generators with a power of more than 1 MW from currents caused by external short circuits must be carried out in compliance with following requirements:

1. The protection should be connected to current transformers installed at the generator terminals on the neutral side.

2. If there is sectioning of the generator voltage buses, protection should be performed with two time delays: with a shorter delay for turning off the corresponding sectional and bus-connecting switches, with a longer delay for turning off the generator breaker and field extinguishing.

3.2.46. On generators with direct cooling of the winding conductors, rotor overload protection must be provided when the generator is operating with both main and backup excitation. Protection should be performed with an independent or current-dependent time delay and responsive to an increase in voltage or current in the rotor winding. The protection should act to disconnect the generator circuit breaker and extinguish the field. The rotor should be unloaded with a shorter time delay from protection.

3.2.47. Protection of the generator from currents caused by symmetrical overload must be implemented in the form of overcurrent protection acting on a time-delayed signal and using the current of one stator phase.

For unloading and, if necessary, for automatic shutdown of the generator with direct cooling of the winding conductors during symmetrical overloads, it is allowed to use rotor protection, performed in accordance with 3.2.46 and responding to rotor overloads accompanying symmetrical overloads of turbogenerators.

3.2.48. Protection against ground faults at the second point of the excitation circuit of turbogenerators must be provided in one set for several (but not more than three) generators with similar parameters of the excitation circuits. The protection should be activated only when a ground fault occurs at one point of the excitation circuit, detected during periodic insulation monitoring (see Chapter 1.6). The protection must operate to trip the generator circuit breaker and field suppression on generators with direct cooling of the winding conductors and to signal or trip on generators with indirect cooling.

3.2.49. On turbogenerators with direct cooling of winding conductors, it is recommended to install protection devices against asynchronous mode with loss of excitation. Instead, it is permissible to provide for automatic detection of asynchronous mode only by the position of automatic field damping devices. When the specified protection devices operate or when the AGP is turned off, a signal about loss of excitation must be given on generators that allow asynchronous mode.

Generators that do not allow asynchronous mode, and in conditions of reactive power deficiency in the system, other generators that have lost excitation must be disconnected from the network when the specified devices (protection or automatic field suppression) are in operation.

3.2.50. Protection of generators up to 1 kV with a power of up to 1 MW with an ungrounded neutral from all types of damage and abnormal operating conditions should be carried out by installing a circuit breaker with overcurrent releases or a switch with overcurrent protection in a two-phase version at the terminals. If there are terminals on the neutral side, the specified protection should, if possible, be connected to current transformers installed on these terminals.

For these generators with a solidly grounded neutral, this protection must be provided in a three-phase version.

Protection of transformers (autotransformers) with high voltage windings of 3 kV and above and shunt reactors of 500 kV

3.2.51. For transformers1, relay protection devices must be provided against the following types of damage and abnormal operating conditions:

1) multiphase short circuits in windings and terminals;

2) single-phase ground faults in the winding and at the terminals connected to the network with a solidly grounded neutral;

3) turn short circuits in the windings;

4) currents in the windings caused by external short circuits;

5) currents in the windings caused by overload;

6) lowering the oil level;

7) partial breakdown of insulation of 500 kV bushings;

8) single-phase ground faults in 3-10 kV networks with an isolated neutral, if the transformer supplies a network in which disconnecting single-phase ground faults is necessary according to safety requirements (see 3.2.96).

3.2.52. For 500 kV shunt reactors, relay protection devices should be provided against the following types of damage and abnormal operating conditions:

1) single-phase and two-phase ground faults in windings and terminals;

2) turn short circuits in the windings;

3) lowering the oil level;

4) partial breakdown of the bushings insulation.

3.2.53. Gas protection against damage inside the casing, accompanied by the release of gas, and against a decrease in the oil level must be provided:

• for transformers with a capacity of 6.3 MVA and more;
• for shunt reactors with voltage 500 kV;
• for in-shop step-down transformers with a capacity of 630 kVA and more.

Gas protection can also be installed on transformers with a capacity of 1-4 MVA.

Gas protection should act on a signal in the event of weak gas formation and a decrease in the oil level and switch off in the event of intense gas formation and a further decrease in the oil level.

Protection against damage inside the transformer casing, accompanied by the release of gas, can also be achieved using a pressure switch.

Low oil level protection can also be implemented as a separate level relay in the transformer expander.

To protect the on-load tap-changer contactor device with an arc break in the oil, a separate gas relay and pressure relay should be provided.

To protect tap changers located in a separate tank, a separate gas relay should be provided.

It must be possible to transfer the action of the disconnecting element of the gas protection to a signal and to perform separate signaling from the signal and disconnecting elements of the gas relay (which differ in the nature of the signal).

It is allowed to perform gas protection with the action of the disconnecting element only on the signal:

• on transformers that are installed in areas prone to earthquakes;
• on intra-shop step-down transformers with a capacity of 2.5 MVA or less, which do not have switches on the high voltage side.

3.2.54. To protect against damage at the terminals, as well as against internal damage, the following must be provided:

1. Longitudinal differential current protection without time delay on transformers with a power of 6.3 MVA and more, on shunt reactors of 500 kV, as well as on transformers with a power of 4 MVA when the latter operate in parallel in order to selectively disconnect the damaged transformer.

Differential protection can be provided on transformers of lower power, but not less than 1 MVA, if:

• the current cut-off does not meet the sensitivity requirements, and the maximum current protection has a time delay of more than 0.5 s;
• The transformer is installed in an area prone to earthquakes.

2. Current cut-off without time delay, installed on the supply side and covering part of the transformer winding, if differential protection is not provided.

The specified protections must act to disconnect all transformer switches.

3.2.55. Longitudinal differential current protection should be carried out using special current relays, designed to protect against magnetizing current surges, transient and steady-state unbalance currents (for example, saturable current transformers, brake windings).

On transformers with a power of up to 25 MVA, it is allowed to perform protection with current relays, adjusted for the operating current against magnetizing current surges and transient values ​​of unbalance currents (differential cutoff), if the required sensitivity is ensured.

Longitudinal differential protection must be designed so that its coverage area includes the connections of the transformer with the busbars.

It is allowed to use current transformers built into the transformer for differential protection if there is protection that ensures disconnection (with the required speed) of short circuits in the connections of the transformer with the busbars.

If a reactor is installed in the low-voltage circuit of the transformer and the transformer protection does not provide the sensitivity requirements for a short circuit behind the reactor, it is allowed to install current transformers on the side of the low-voltage terminals of the transformer to protect the reactor.

3.2.56. The differential and gas protection of transformers, autotransformers and shunt reactors should not be assigned the functions of fire extinguishing installation start sensors. The fire extinguishing circuit of these elements must be started from a special fire detection device.

3.2.57. The 500 kV input insulation monitoring device (IMC) must be designed to act on a signal in the event of a partial breakdown of the input insulation, which does not require immediate shutdown, and to switch off when the input insulation is damaged (before a complete breakdown of the insulation occurs).

A blocking must be provided to prevent false triggering of the KIV device in the event of breaks in the circuits connecting the KIV to the terminals.

3.2.58. In cases where transformers (except intra-shop ones) are connected to lines without switches (for example, according to a line-transformer block diagram), one of the following measures must be provided to disconnect faults in the transformer:

1. Installation of a short circuit for an artificial short circuit to the ground of one phase (for a network with a solidly grounded neutral) or two phases between each other (for a network with an isolated neutral) and, if necessary, a separator that automatically turns off during a dead time period of the automatic reclosure line. The short contactor must be installed outside the differential protection zone of the transformer.

2. Installation of open fuse-links on the high-voltage side of the step-down transformer, performing the functions of a short circuiter and separator, in combination with automatic reclosure of the line.

3. Transmitting a tripping signal to the line switch (or switches); in this case, if necessary, a separator is installed; To reserve the transmission of the shutdown signal, it is possible to install a short circuiter.

When deciding whether to use the transmission of a shutdown signal instead of measures in paragraphs 1 and 2, the following should be taken into account:

• responsibility of the line and the permissibility of artificially creating a metal short circuit on it;
• transformer power and permissible time to eliminate damage in it;
• the distance of the substation from the supply end of the line and the ability of the circuit breaker to disconnect non-remote short circuits;
• the nature of the consumer in terms of the required speed of voltage restoration;
• probability of short circuit failures at low temperatures and ice.

4. Installation of fuses on the high voltage side of the step-down transformer.

Measures in paragraphs 1-4 may not be provided for line-transformer units if, with double-sided power supply, the transformer is protected by the general protection of the unit (high-frequency or longitudinal differential special purpose), as well as with a transformer power of 25 MVA or less with one-way power supply, if the supply line protection also provides protection for the transformer (fast line protection partially protects the transformer and backup line protection with a time of no more than 1 s protects the entire transformer); in this case, gas protection is performed with the action of the disconnecting element only on the signal.

In the case of applying measures in paragraphs 1 or 3, the following must be installed on the transformer:

• if there are built-in current transformers on the higher voltage side of the transformer (110 kV and above) - protection according to 3.2.53, 3.2.54, 3.2.59 and 3.2.60;
• in the absence of built-in current transformers - differential (in accordance with 3.2.54) or overcurrent protection, made using overhead or magnetic current transformers, and gas protection in accordance with 3.2.53.

Damage to the high voltage terminals of transformers can be eliminated by line protection.

In some cases, in the absence of built-in current transformers, the use of remote current transformers is allowed if the required protection characteristics are not provided when using overhead or magnetic current transformers.

To protect transformers with a higher voltage of 35 kV in the case of applying the measure in paragraph 1, remote current transformers must be provided; in this case, the feasibility of installing a short-circuiter and remote current transformers or a circuit breaker with built-in current transformers must be justified by a technical and economic calculation.

If open fuse-links are used (see paragraph 2), then to increase sensitivity, the action of gas protection can be carried out by mechanically performing an artificial short circuit on the inserts.

If the loads of substation transformers contain synchronous electric motors, then measures must be taken to prevent the separator from disconnecting (during a short circuit in one of the transformers) the current from the synchronous electric motors passing through other transformers.

3.2.59. On transformers with a power of 1 MV A or more, the following protection with shutdown action must be provided as protection against currents in the windings caused by external multiphase short circuits:

1. On step-up transformers with double-sided supply - negative sequence current protection against asymmetrical short-circuits and maximum current protection with minimal voltage inrush against symmetrical short-circuits or maximum current protection with combined voltage inrush (see 3.2.43).

2. On step-down transformers - maximum current protection with or without combined voltage starting; on powerful step-down transformers with double-sided power supply, it is possible to use negative sequence current protection against asymmetrical short-circuits and maximum current protection with minimal voltage inrush against symmetrical short-circuits.

When choosing the operating current of the maximum current protection, it is necessary to take into account possible overload currents when disconnecting parallel operating transformers and the self-starting current of electric motors powered from transformers.

On step-down autotransformers of 330 kV and above, distance protection should be provided for operation during external multi-phase short circuits in cases where this is required to ensure long-range backup or coordination of protection of adjacent voltages; in these cases, the specified protection can be installed on 220 kV autotransformers.

3.2.60. On transformers with a power of less than 1 MVA (step-up and step-down), as protection against currents caused by external multi-phase short circuits, maximum current protection must be provided for tripping.

3.2.61. Protection against currents caused by external multiphase short circuits should be installed:

1) on two-winding transformers - from the main power supply side;

2) on multi-winding transformers connected by three or more switches - on all sides of the transformer; it is allowed not to install protection on one side of the transformer, but to carry it out from the main power supply side, so that it turns off the switches with a shorter time delay on the side on which there is no protection;

3) on a step-down two-winding transformer feeding separately operating sections - on the supply side and on the side of each section;

4) when using overhead current transformers on the high voltage side - on the low voltage side on a two-winding transformer and on the low and medium voltage side on a three-winding transformer.

It is permissible to provide protection against currents caused by external multiphase short circuits only for redundancy of protection of adjacent elements and not to provide for action in the event of failure of the main transformer protections, if implementation of such an action leads to a significant complication of the protection.

When performing protection against currents caused by external multiphase short circuits, according to 3.2.59, clause 2, the need and possibility of supplementing it with a current cutoff, designed to disconnect short circuits on medium and low voltage buses with a shorter time delay (based on the level of currents) should also be considered short circuit, the presence of separate busbar protection, the possibility of coordination with the protection of outgoing elements).

3.2.62. If the protection of step-up transformers from currents caused by external multi-phase short circuits does not provide the required sensitivity and selectivity, then to protect the transformer it is possible to use a current relay for the corresponding protection of generators.

3.2.63. On step-up transformers with a power of 1 MVA or more, on transformers with two- and three-way power supply and on autotransformers, subject to the need to reserve the shutdown of ground faults on adjacent elements, and on autotransformers, in addition, to ensure selectivity of protection against ground faults On the ground of networks of different voltages, zero-sequence current protection against external ground faults must be provided, installed on the side of the winding connected to the network with large ground fault currents.

If there is a part of the transformers (from among those with incomplete winding insulation on the side of the neutral terminal) with an isolated neutral, it must be ensured that the unacceptable mode of the neutral of these transformers is prevented in accordance with 3.2.28. For this purpose, in cases where transformers with a grounded and isolated neutral, powered from low voltage sides, are installed at a power plant or substation, protection must be provided to ensure the disconnection of the transformer with an isolated neutral or its automatic grounding before disconnecting transformers with a grounded neutral operating at the same buses or network section.

3.2.64. On autotransformers (multi-winding transformers) with power supply from several sides, protection against currents caused by external short circuits must be directional, if this is required by selectivity conditions.

3.2.65. On autotransformers of 220-500 kV substations, generator-transformer units of 330-500 kV and communication autotransformers of 220-500 kV power plants, it must be possible to quickly accelerate protection against currents caused by external short-circuits, when the differential protection of busbars or busbars that provide shutdown are taken out of action damage on elements left without fast-acting protection with a time delay of about 0.5 s.

3.2.66. On step-down transformers and transformer-line units with a higher voltage of up to 35 kV and a star connection of the low-voltage winding with a grounded neutral, protection against single-phase ground faults in the low-voltage network should be provided by using:

1) maximum current protection against external short circuits, installed on the high voltage side, and, if required by sensitivity conditions, in a three-relay design;

2) circuit breakers or fuses at low voltage terminals;

3) special zero-sequence protection installed in the neutral wire of the transformer (if the protection sensitivity according to clauses 1 and 2 is insufficient).

For industrial electrical installations, if the assembly on the low voltage side with connection protection devices is located in close proximity to the transformer (up to 30 m) or the connection between the transformer and the assembly is made with three-phase cables, the protection according to clause 3 may not be used.

When applying protection according to clause 3, it is allowed not to coordinate it with the protection of elements extending from the assembly on the low voltage side.

For the line-transformer circuit, in the case of applying protection according to clause 3, it is allowed not to lay a special control cable to ensure the effect of this protection on the circuit breaker from the high voltage side and to carry it out with the effect on circuit breaker, installed on the low voltage side.

The requirements of this paragraph also apply to the protection of these transformers by fuses installed on the high voltage side.

3.2.67. On the low voltage side of step-down transformers with a higher voltage of 3-10 kV, feeding assemblies with connections protected by fuses, a main fuse or circuit breaker should be installed.

If the fuses on the low voltage connections and the fuses (or relay protection) on the high voltage side are maintained and operated by the same personnel (for example, only utility personnel or only customer personnel), then the main fuse or circuit breaker on the low voltage side of the transformer may not be installed.

3.2.68. Protection against single-phase earth faults according to 3.2.51, clause 8, must be carried out in accordance with 3.2.97.

3.2.69. On transformers with a power of 0.4 MVA or more, depending on the probability and value of a possible overload, maximum current protection against currents caused by overload affecting the signal should be provided.

For substations without constant personnel duty, it is allowed to provide for the effect of this protection on automatic unloading or shutdown (if it is impossible to eliminate the overload by other means).

3.2.70. If there is a separate additional transformer on the neutral side of the transformer to regulate the voltage under load, it is necessary to provide the following protection in addition to those specified in 3.2.51-3.2.57, 3.2.59, 3.2.63:

• gas protection of the additional transformer;
• maximum current protection with braking during external short circuits from damage in the primary winding of the additional transformer, except for cases when this winding is included in the coverage area of ​​the differential current protection of the circuits of the low voltage side of the autotransformer;
• differential protection, which covers the secondary winding of the additional transformer.

3.2.71. Protection of the linear additional transformer installed on the low voltage side of the autotransformer should be carried out:

• gas protection of the additional transformer itself and protection of the on-load tap-changer contactor device, which can be performed using a pressure relay or a separate gas relay;
• differential current protection of the low voltage side circuits of the autotransformer.

Protection of generator - transformer units

3.2.72. For generator-transformer units with generators with a power of more than 10 MW, relay protection devices must be provided against the following types of damage and abnormal operating conditions:

1) ground faults on the generator voltage side;

2) multiphase short circuits in the generator stator winding and at its terminals;

3) short circuits between turns of one phase in the stator winding of a turbogenerator (in accordance with 3.2.76);

4) multiphase short circuits in the windings and terminals of the transformer;

5) single-phase ground faults in the transformer winding and at its terminals connected to a network with large ground fault currents;

6) short circuits between turns in the windings of the transformer;

7) external short circuits;

8) generator overload with negative sequence currents (for units with generators with a capacity of more than 30 MW);

9) symmetrical overload of the generator stator winding and transformer windings;

10) overloading the generator rotor winding with excitation current (for turbogenerators with direct cooling of the winding conductors and for hydrogenerators);

11) increasing the voltage on the generator stator and unit transformer (for units with turbogenerators with a capacity of 160 MW or more and for all units with hydrogen generators);

12) ground faults at one point of the excitation circuit (in accordance with 3.2.85);

13) ground faults at the second point of the excitation circuit of a turbogenerator with a power of less than 160 MW;

14) asynchronous mode with loss of excitation1 (in accordance with 3.2.86);

1 To prevent asynchronous operation without loss of excitation, see Chap. 3.3.

15) lowering the oil level in the transformer tank;

16) partial breakdown of insulation of 500 kV transformer bushings.

3.2.73. Instructions for protecting generators and step-up transformers related to their separate operation are also valid for the case when they are combined into a generator-transformer unit (autotransformer), taking into account the requirements given in 3.2.74-3.2.90.

3.2.74. On units with generators with a capacity of more than 30 MW, as a rule, ground fault protection must be provided in the generator voltage circuit, covering the entire stator winding.

When the block generator power is 30 MW or less, devices that protect at least 85% of the stator winding should be used. The use of such devices is also allowed on units with turbogenerators with a power of 30 to 160 MW, if additional equipment must be included in the generator circuit to protect the entire stator winding.

Protection must be carried out with a shutdown action with a time delay of no more than 0.5 s on all units without branches on the generator voltage and with branches to auxiliary transformers. On units that have an electrical connection with the network for their own needs or consumers, powered by lines from branches between the generator and the transformer, if capacitive current earth faults of 5 A or more, tripping protection must be installed against earth faults in the generator stator winding and against double earth faults, as provided for generators operating on busbars (see 3.2.38 and 3.2. 39); If the capacitive ground fault current is less than 5 A, then ground fault protection can be performed in the same way as on units without generator voltage branches, but with an effect on the signal.

If there is a switch in the generator circuit, an additional ground fault alarm must be provided on the generator voltage side of the unit transformer.

3.2.75. On a unit with an indirectly cooled generator, consisting of one generator and one transformer, in the absence of a switch in the generator circuit, it is recommended to provide one common longitudinal differential protection of the unit. If there is a switch in the generator circuit, separate differential protection must be installed on the generator and transformer.

When using two transformers in a unit instead of one, as well as when operating two or more generators without switches in a unit with one transformer (enlarged unit), separate longitudinal differential protection must be provided for each generator and transformer with a capacity of 125 MVA or more. In the absence of built-in current transformers at the low voltage inputs of these transformers, it is permissible to use common differential protection for two transformers.

On a unit with a generator that has direct cooling of the winding conductors, separate longitudinal differential protection of the generator should be provided. In this case, if there is a switch in the generator circuit, then separate differential protection must be installed for the block transformer (or for each transformer if two or more transformers are operating in the generator block; if there are no built-in current transformers at the low voltage inputs of these transformers, the use of general differential protection is allowed for block transformers); If there is no circuit breaker to protect the unit's transformer, either separate differential protection or general longitudinal differential protection of the unit should be installed (for units consisting of one generator and one transformer, general differential protection of the unit is preferable).

On the higher voltage side, differential protection of the transformer (unit) can be switched on to current transformers built into the unit transformer. In this case, to protect the busbar, separate protection must be installed between the circuit breakers on the high voltage side and the transformer of the unit.

Separate differential protection of generators must be three-phase three-relay with an operating current similar to that specified in 3.2.36.

To reserve the specified differential protection on units with generators with a power of 160 MW or more, which have direct cooling of the winding conductors, backup differential protection should be provided, covering the generator and transformer of the unit along with the busbar on the high voltage side.

When using backup differential protection on units without a circuit breaker in the generator circuit, it is recommended to provide separate main differential protection for the generator and transformer.

If there is a switch in the generator circuit, backup differential protection must be performed with a time delay of 0.35-0.5 s.

3.2.76. On turbogenerators with two or three parallel branches of the stator winding, a single-system transverse differential protection against turn faults in one phase, operating without a time delay, must be provided.

3.2.77. On units with generators with a capacity of 160 MW or more with direct cooling of the winding conductors, negative sequence current protection with an integral dependent characteristic corresponding to the characteristic of permissible overloads of the protected generator with negative sequence currents must be provided. The protection should act to disconnect the generator circuit breaker, and in its absence, to disconnect the unit from the network. To back up the protection of elements adjacent to the units, the specified protection must have an element with an independent time delay, which acts to disconnect the unit from the network and has a two-stage action in accordance with 3.2.81.

On units with generators with a power of less than 160 MW, which have direct cooling of the winding conductors, as well as on units with hydrogenerators with a power of more than 30 MW, which have indirect cooling, negative sequence current protection should be performed with a step or dependent time delay. In this case, different protection stages may have one or more time delays (see 3.2.81, clause 4). The specified step or dependent time delay must be consistent with the characteristics of permissible generator overloads with negative sequence current (see 3.2.41).

On units with indirectly cooled turbogenerators with a capacity of more than 30 MW, protection must be carried out in accordance with 3.2.41.

In addition to shutdown protection, all units with turbogenerators with a capacity of more than 30 MW must be equipped with an overload alarm with negative sequence currents, performed in accordance with 3.2.41.

3.2.78. On units with generators with a capacity of more than 30 MW, protection against external symmetrical short circuits must be performed as specified in 3.2.42. In this case, for hydrogenerators, the protection response voltage should be taken to be about 0.6-0.7 nominal. On units with turbogenerators that have a backup exciter, the specified protection must be supplemented by a current relay connected to the current on the higher voltage side of the unit.

On units with generators with a capacity of 60 MW or more, it is recommended to use distance protection instead of the specified protection. On units with generators that have direct cooling of the winding conductors, instead of backup differential protection (see 3.2.75), it is allowed to install two-stage distance protection against phase-to-phase short circuits.

The first stage of this protection, which provides short-range backup, must be blocked during swings and operate as specified in 3.2.81, paragraph 3, with a time delay of no more than 1 s. The first stage must reliably enclose the transformer of the unit while ensuring selectivity with protection of adjacent elements. Redundancy of the first stage of generator protection is mandatory if the unit uses separate differential protection for the transformer and generator.

The second stage, providing long-range backup, must act as specified in 3.2.81, paragraph 2.

It is recommended to install two-stage distance protection in the presence of backup differential protection in order to increase the efficiency of long-range backup. Both stages of distance protection in this case must operate as specified in 3.2.81, paragraph 2.

3.2.79. Protection against external short circuits on units with generators with a capacity of 30 MW or less should be performed in accordance with 3.2.43. The protection response parameters on units with hydrogenerators should be taken in accordance with 3.2.42, 3.2.43 and 3.2.78.

3.2.80. On generator-transformer units with a switch in the generator circuit, in the absence of backup differential protection of the unit, maximum current protection must be provided on the side of the higher voltage of the unit, designed to back up the main protections of the unit transformer when operating with the generator turned off.

3.2.81. Backup protection of generator-transformer units must be carried out taking into account the following:

1. No protection is installed on the generator voltage side of the unit transformer, but generator protection is used.

2. In case of long-range backup, the protection should operate, as a rule, with two time delays: with the first - for dividing the circuit on the high voltage side of the block (for example, for disconnecting the busbar and section switches), with the second - for disconnecting the block from the network.

3. In case of short-term backup, the unit (generator) must be disconnected from the network, the generator field must be extinguished, and the unit must be stopped, if required by 3.2.89.

4. Individual stages or backup protection devices, depending on their purpose and the feasibility of use for long- and short-range backup, can have one, two or three time delays.

5. It is recommended to provide starting voltage protection devices according to 3.2.78 and 3.2.79 on the generator voltage side and on the network side.

6. For the main and backup protections of the unit, as a rule, separate output relays and operational direct current supply from different circuit breakers should be provided.

3.2.82. On units with turbogenerators, protection against symmetrical stator overloads should be carried out in the same way as on generators operating on busbars (see 3.2.47).

At hydroelectric power plants without constant duty of operating personnel, in addition to signaling symmetrical overloads, protection with an independent characteristic must be provided, operating with a longer time delay for shutting down the unit (generator) and a shorter time delay for unloading. Instead of the specified protection, appropriate devices can be used in the excitation control system.

3.2.83. On generators with a power of 160 MW or more with direct cooling of the winding conductors, protection against overload of the rotor winding with excitation current must be performed with an integral dependent time delay, which corresponds to the characteristics of permissible overloads of the generator with excitation current. This protection must operate to switch off.

If it is impossible to turn on protection for the rotor current (for example, with brushless excitation), it is permissible to use protection with an independent time delay that responds to an increase in voltage in the excitation circuit.

The protection must provide the ability to operate with a shorter time delay to reduce the excitation current. If there are overload limiting devices in the excitation regulator, the unloading action can be carried out simultaneously from these devices and from the rotor protection. It is also possible to use an overload limiting device in the AVR for unloading (with two time delays) and shutdown. In this case, protection with integral dependent time delay may not be installed.

On turbogenerators with a capacity of less than 160 MW with direct cooling of the winding conductors and on hydrogenerators with a capacity of more than 30 MW with indirect cooling, protection should be carried out in the same way as specified in 3.2.46.

If there are group excitation control devices on generators, it is recommended to implement protection with a dependent time delay.

When operating generators with a backup exciter, the rotor overload protection must remain operational. If it is impossible to use protection with a dependent time delay, it is allowed to provide protection with an independent time delay on the backup exciter.

3.2.84. On units with turbogenerators with a capacity of 160 MW or more, in order to prevent an increase in voltage during idle mode, overvoltage protection must be provided, which is automatically disabled when the generator is connected to the network. When the protection is in effect, the field extinguishing of the generator and exciter must be ensured.

On units with hydraulic generators, to prevent voltage increases during load shedding, overvoltage protection must be provided. The protection should act to turn off the unit (generator) and extinguish the generator field. The protection action is allowed to stop the unit.

3.2.85. Protection against ground faults at one point in the excitation circuit must be provided on hydrogenerators, on turbine generators with water-cooled rotor windings and on all turbogenerators with a power of 300 MW and above. On hydrogenerators, the protection should act on shutdown, and on turbogenerators - on a signal.

Ground fault protection at the second point of the excitation circuit of turbogenerators must be installed on units with a capacity of less than 160 MW in accordance with 3.2.48.

3.2.86. On units with turbogenerators with a capacity of 160 MW or more, which have direct cooling of the winding conductors, and with hydrogenerators, protection devices against asynchronous mode with loss of excitation should be provided.

These devices are also recommended for use on turbogenerators with a power of less than 160 MW with direct cooling of the winding conductors. On these turbogenerators, it is also allowed to provide for automatic detection of asynchronous mode only by the disabled position of automatic field damping devices (without using protection against asynchronous mode).

When switching to asynchronous mode a turbogenerator that has lost excitation, the above-mentioned protection or automatic field suppression devices must act on the signal about the loss of excitation and automatically switch the auxiliary load in the branch of the unit whose generator has lost excitation to a backup power source.

All hydrogenerators and turbogenerators that do not allow asynchronous operation, as well as other turbogenerators in conditions of a shortage of reactive power in the system when the specified devices are operating, must be disconnected from the network.

3.2.87. If there is a switch in the generator circuit with direct cooling of the winding conductors, redundancy should be provided in case of failure of this switch (for example, by using a breaker failure protection device).

3.2.88. Breaker levels of 110 kV and higher at power plants must be carried out taking into account the following:

1. To prevent unnecessary shutdown of several units by backup protection when a non-phase mode occurs on one of them as a result of failure of a circuit breaker with a phase-by-phase drive when it is turned off, at power plants with generators that have direct cooling of the winding conductors, an accelerated start of the breaker failure protection must be provided (for example, from the current protection of the zero sequence of the unit transformer on the network side with a large ground fault current).

2. For power plants where the generator-transformer units and lines have common switches (for example, when using a one-and-a-half circuit or a polygon circuit), it is necessary to provide a tele-shutdown device to disconnect the circuit breaker and prohibit automatic reclosure at the opposite end of the line when a breaker failure occurs in the event of its start from block protection. In addition, the effect of a breaker failure failure on stopping the high-frequency protection transmitter should be provided.

3.2.89. When acting to disconnect the generator stator and unit transformer protections from internal damage, as well as the generator rotor protections, the damaged element must be disconnected from the network, the generator and exciter field extinguished, the breaker failure failure must be started, and the process protections must be affected.

If disconnection from the protection leads to the de-energization of the auxiliary load connected by a branch to the unit, the protection must also act to disconnect the switches in the circuit of the operating auxiliary power supply in order to transfer them to power from a backup source using an automatic transfer switch.

Backup protection of the generator and transformer of the unit in case of external damage must operate in accordance with 3.2.81, clauses 2-4.

At thermal power plants with a block circuit in the thermal part, in cases of unit shutdown due to internal damage, a complete shutdown of the unit must be ensured. In case of external damage, as well as during the operation of protection in cases where the operation of the unit can be quickly restored, the unit must be switched to idle mode, if this mode is allowed by the thermal-mechanical equipment.

At hydroelectric power plants, in case of internal damage to the unit, in addition to shutting down the unit, the unit must be stopped. The action to stop the unit can also be carried out when the unit is turned off as a result of external damage.

3.2.90. On generator-transformer-line units, the main line protection and backup protection on the power system side must be performed in accordance with the requirements of this chapter on line protection, and on the unit side, the line backup functions must be performed by the unit's backup protections.

The protection of the unit must be carried out according to the above requirements.

The action of the unit protection to open the circuit breaker and start the breaker failure protection from the power system side must be transmitted using two mutually redundant tele-shutdown devices via a high-frequency channel or via communication wires. In addition, it is recommended to provide for the simultaneous action of the unit protection to stop the high-frequency protection transmitter.

On blocks with turbogenerators (with a block circuit in the thermal part), the action of the busbar protection (with a double bus system) or the action of the breaker failure protection (with a one-and-a-half circuit or a polygon circuit) must be transmitted from the power system to the opposite end of the line using a teleswitching device, respectively, to transfer the block to idle mode or to extinguish the generator field and stop the unit. In addition, it is recommended to use a tele-shutdown device to speed up the extinguishing of the generator field and to shut down auxiliary needs when there are backup protections on the part of the power system.

In the event of an open-phase disconnection of the circuit breaker from the network side with a large ground fault current, an accelerated start of the breaker failure protection must be carried out in the same way as provided for in 3.2.88, clause 1.

Protection of overhead and cable lines in networks with a voltage of 3-10 kV with an insulated neutral

3.2.91. For lines in 3-10 kV networks with an isolated neutral (including with a neutral grounded through an arc-extinguishing reactor), relay protection devices against multi-phase faults and single-phase ground faults must be provided.

3.2.92. Protection against multi-phase faults should be provided in a two-phase design and included in the same phases throughout the entire network of a given voltage to ensure that in most cases of double earth faults only one fault point is disconnected.

The protection should be one-, two- or three-relay depending on the requirements of sensitivity and reliability.

3.2.93. On single lines with one-way power supply from polyphase faults, as a rule, two-stage current protection should be installed, the first stage of which is made in the form of a current cut-off, and the second - in the form of maximum current protection with an independent or dependent time delay characteristic.

On unreacted cable lines with one-way power supply extending from the buses of power plants, current cut-offs must be performed without a time delay and their coverage area must be determined from the condition of disconnecting the short circuit, accompanied by a residual voltage on the buses of the specified power plants below 0.5-0.6 rated. To fulfill the specified condition, it is allowed to perform non-selective protection in combination with automatic reclosure or automatic transfer devices that correct fully or partially the non-selective action of protection. It is also possible to install the specified cutoffs on lines extending from substation buses and feeding large synchronous electric motors.

If on unreacted cable lines with one-way power supply coming from the buses of power plants, current cut-offs cannot be applied due to selectivity requirements, then to ensure speed it is allowed to provide protection according to 3.2.94, clause 2 or 3. The use of these protections is also allowed for working lines own needs of thermal power plants.

On reacted lines, the switches of which are not designed to disconnect a short circuit to the reactor, current cutoffs are not allowed.

3.2.94. On single lines with two-way power supply, with or without bypass connections, as well as on lines included in a ring network with one power point, it is recommended to apply the same protection as on single lines with one-way power supply (see 3.2.93), performing them, if necessary, directed.

In order to simplify protections and ensure their selective action, it is possible to use automatic division of the network into radial sections at the moment of damage, followed by automatic restoration.

If non-directional or directional current step protection does not provide the required speed and selectivity, the following protection may be provided:

1) distance protection in the simplest design;

2) transverse differential current protection (for dual cable lines);

3) longitudinal differential current protection for short sections of lines; if it is necessary to lay a special cable only for longitudinal differential protection, its length should be no more than 3 km.

For the protections specified in clauses 2 and 3, current protection should be provided as backup protection.

3.2.95. When protecting parallel lines of 3-10 kV, you should follow the instructions for parallel lines in 35 kV networks (see 3.2.104).

3.2.96. Protection against single-phase earth faults must be in the form of:

selective protection (establishing the damaged direction) acting on the signal;

selective protection (establishing the damaged direction), which acts to disconnect when necessary according to safety requirements; protection must be installed on power supply elements throughout the electrically connected network;

insulation monitoring devices; in this case, the search for the damaged element must be carried out with special devices; It is possible to find the damaged element by disconnecting the connections one by one.

3.2.97. Protection against single-phase earth faults must be performed, as a rule, using zero-sequence current transformers. The protection must first respond to established ground faults; It is also allowed to use devices that record short-term circuits, without ensuring repeatability.

Protection against single-phase earth faults, operating without a time delay according to safety requirements (see 3.2.96), should only disconnect the element supplying the damaged area; in this case, as a backup, protection must be provided in the form of zero-sequence protection with a time delay of about 0.5 s, which acts to disconnect the entire electrically connected network - a bus system (section) or a supply transformer.

An increase in the power frequency current specifically to ensure protection in a network with a neutral grounded through an arc suppression reactor (for example, by detuning the reactor) is, as a rule, not allowed.

Protection of overhead and cable lines in 20 and 35 kV networks with insulated neutral

3.2.98. For lines in 20 and 35 kV networks with an isolated neutral, relay protection devices must be provided against multiphase faults and single-phase ground faults.

3.2.99. Protection against multi-phase faults should be provided in a two-phase, two-relay design and included in the same phases throughout the entire network of a given voltage to ensure that in most cases of double ground faults, only one fault point is disconnected. In order to increase sensitivity to damage behind transformers with a star-delta winding connection, three-relay protection is allowed.

Protection against single-phase earth faults should be carried out, as a rule, with an effect on the signal. To implement protection, it is allowed to use an insulation monitoring device.

3.2.100. When choosing the type of main protection, the requirements for ensuring the stability of the power system and reliable operation of the consumer should be taken into account in the same way as this is taken into account for the protection of 110 kV lines (see 3.2.108).

3.2.101. On single lines with one-way power supply from multiphase faults, predominantly step current protection or step current and voltage protection should be installed, and if such protection does not meet the requirements of sensitivity or speed of fault shutdown (see 3.2.108), for example, in the head sections, remote step protection mainly with current starting. In the latter case, it is recommended to use current cut-off without a time delay as additional protection.

For lines consisting of several consecutive sections, for the purpose of simplification, the use of non-selective step current and voltage protection in combination with alternating automatic reclosure devices is allowed.

3.2.102. On single lines with power from two or more sides (the latter on lines with branches), both with and without bypass connections, as well as on lines included in a ring network with one power point, it is recommended to use the same protection , as on single lines with one-way power supply (see 3.2.101), making them directional if necessary, and remote ones - starting from a resistance relay. In this case, non-selective shutdown of adjacent elements is allowed during a short circuit in the “dead” voltage zone of the power direction relay, when the current cutoff used as additional protection (see 3.2.101) is not installed, for example, due to its insufficient sensitivity. Protection is installed, as a rule, only on those sides from which power can be supplied.

3.2.103. On short single lines with double-sided power supply, when required by the condition of speed of action, it is allowed to use longitudinal differential protection as the main one. In this case, the length of the cable laid specifically for this protection should not exceed 4 km. To monitor the serviceability of auxiliary protection wires, special devices should be provided. In addition to longitudinal differential protection, one of the protections in 3.2.102 must be used as a backup.

3.2.104. On parallel lines fed on two or more sides, and on the feeder end of parallel lines fed on one side, the same protection may be used as on the corresponding single lines (see 3.2.101 and 3.2.102).

To speed up fault shutdown, especially when using current step protections or step current and voltage protections, additional protection can be used on lines with double-sided power supply to control the direction of power in a parallel line. This protection can be implemented in the form of a separate transverse current directional protection or only in the form of an acceleration circuit of installed protections (overcurrent, distance) with control of the direction of power in the parallel line.

At the receiving end of two parallel single-ended feed lines, lateral directional differential protection should generally be used.

3.2.105. If the protection of 3.2.104 does not satisfy the speed requirements (see 3.2.108), and protection with control of the direction of power in a parallel line is not applicable or undesirable, as the main protection (when operating two parallel lines) on two parallel lines with double-sided supply and Transverse directional differential protection should be used at the feed end of two parallel lines with one-way feeding.

In this case, in the operating mode of one line, as well as as a backup when operating two lines, step protection according to 3.2.101 and 3.2.102 should be used. It is allowed to turn on this protection or its individual stages for the sum of the currents of both lines (for example, a reserve stage in order to increase its sensitivity to damage on adjacent elements). It is also allowed to use transverse differential directional protection in addition to step current protection to reduce the time of fault shutdown on the protected lines, if, according to the condition of speed of action (see 3.2.108), its installation is not necessary.

In some cases, on short parallel lines, the use of longitudinal differential protection is allowed (see 3.2.103).

Protection of overhead lines in networks with a voltage of 110-500 kV with an effectively grounded neutral

3.2.106. For lines in 110-500 kV networks with an effectively grounded neutral, relay protection devices against multiphase faults and ground faults must be provided.

3.2.107. Protections must be equipped with devices that block their action during swings, if swings or asynchronous movement are possible in the network, during which excessive protection operations are likely. It is allowed to perform protection without blocking devices if it is adjusted against swings in time (about 1.5-2 s).

3.2.108. For lines of 330 kV and above, protection must be provided as the main one, acting without delay during a short circuit at any point in the protected area.

For lines with a voltage of 110-220 kV, the question of the type of main protection, including the need to use protection that acts without delay during a short circuit at any point in the protected area, must be resolved primarily taking into account the requirement to maintain the stability of the power system. Moreover, if, according to calculations of the stability of the power system operation, other, more stringent requirements are not imposed, it can be accepted that the specified requirement, as a rule, is satisfied when three-phase short circuits, in which the residual voltage on the buses of power plants and substations is below 0.6-0, 7 Unom, turn off without delay. Lower residual stress value (0.6 Unom) can be allowed for 110 kV lines, less critical 220 kV lines (in highly branched networks where power to consumers is reliably provided from several sides), as well as for more critical 220 kV lines in cases where the short circuit in question does not lead to significant load shedding .

When choosing the type of protection installed on 110-220 kV lines, in addition to the requirement to maintain the stability of the power system, the following must be taken into account:

1. On lines of 110 kV and higher extending from the nuclear power plant, as well as on all elements of the adjacent network, on which, during multi-phase short circuits, the positive sequence residual voltage on the higher voltage side of the nuclear power plant units can decrease to more than 0.45 of the nominal value, redundancy of high-speed protections with a time delay not exceeding 1.5 s taking into account the action of the breaker failure.

2. Faults, the shutdown of which with a time delay can lead to disruption of the operation of critical consumers, must be switched off without a time delay (for example, faults in which the residual voltage on the buses of power plants and substations will be below 0.6 Unom, if turning them off with a time delay can lead to self-discharge due to a voltage avalanche, or damage with a residual voltage of 0.6 Unom and more, if turning them off with a time delay may lead to disruption of the technology).

3. If it is necessary to carry out high-speed automatic reclosure, a high-speed protection must be installed on the line, ensuring that the damaged line is disconnected without a time delay on both sides.

4. When disconnecting with a time delay of faults with currents several times higher than the rated current, unacceptable overheating of the conductors is possible.

It is allowed to use high-speed protection in complex networks and in the absence of the conditions stated above, if this is necessary to ensure selectivity.

3.2.109. When assessing the provision of stability requirements, based on the residual stress values ​​​​according to 3.2.108, it is necessary to be guided by the following:

1. For a single connection between power plants or power systems, the residual voltage specified in 3.2.108 must be checked on the buses of substations and power plants included in this connection, with a short circuit on the lines extending from these buses, except for the lines forming the connection; for a single connection containing part of the sections with parallel lines - also with a short circuit on each of these parallel lines.

2. If there are several connections between power plants or power systems, the value of the residual voltage specified in 3.2.108 must be checked on the buses of only those substations or power plants where these connections are connected, in case of a short circuit on the connections and on other lines powered from these buses, as well as on lines powered by communication substation buses.

3. The residual voltage must be checked during a short circuit at the end of the zone covered by the first stage of protection in the cascade fault tripping mode, i.e. after tripping the circuit breaker from the opposite end of the line by protection without a time delay.

3.2.110. On single lines with one-way power supply from polyphase faults, step current protection or step current and voltage protection should be installed. If such protections do not meet the requirements of sensitivity or speed of fault shutdown (see 3.2.108), for example, in the head sections, or if this is advisable based on the condition of coordinating the protection of adjacent sections with the protection of the section in question, stepwise distance protection should be provided. In the latter case, it is recommended to use current cut-off without a time delay as additional protection.

As a rule, step current directional or non-directional zero sequence protection should be provided against ground faults. Protection should be installed, as a rule, only on those sides from which power can be supplied.

For lines consisting of several consecutive sections, for the purpose of simplification, it is allowed to use non-selective stepwise current and voltage protection (against multiphase faults) and stepwise zero-sequence current protection (against ground faults) in combination with sequential reclosure devices.

3.2.111. On single lines with power from two or more sides (the latter on lines with branches), both with and without bypass connections, as well as on lines included in a ring network with one power point, there must be protection against multiphase short circuits distance protection is applied (mostly three-stage), used as a backup or primary (the latter - only on 110-220 kV lines).

As additional protection, it is recommended to use a current cut-off without a time delay. In some cases, it is allowed to use a current cutoff to act in the event of an erroneous connection to a three-phase short circuit at the place where the protection is installed, when the current cutoff performed for operation in other modes does not satisfy the sensitivity requirement (see 3.2.26).

As a rule, step current directional or non-directional zero sequence protection should be provided against ground faults.

3.2.112. As the main protection against multiphase faults at the receiving end of the head sections of a ring network with one power point, it is recommended to use single-stage current directional protection; on other single lines (mainly 110 kV), in some cases it is allowed to use step current protection or step current and voltage protection, making them directional if necessary. Protection should generally be installed only on those sides from which power can be supplied.

3.2.113. On parallel lines fed on two or more sides, and on the feeder end of parallel lines fed on one side, the same protection may be used as on the corresponding single lines (see 3.2.110 and 3.2.111).

To speed up the disconnection of ground faults, and in some cases, faults between phases on lines with double-sided power supply, it can be used additional protection with control of the direction of power in a parallel line. This protection can be implemented in the form of a separate transverse current protection (with the inclusion of a relay for zero-sequence current or phase currents) or only in the form of an acceleration circuit of installed protections (zero-sequence current, maximum current, distance, etc.) with direction control power in parallel lines.

In order to increase the sensitivity of zero-sequence protection, it is possible to provide for the removal of its individual stages from operation when the parallel line circuit breaker is disconnected.

Transverse directional differential protection should generally be provided at the receiving end of two parallel single-ended feed lines.

3.2.114. If the protection according to 3.2.113 does not meet the speed requirements (see 3.2.108), as the main protection (when operating two parallel lines) at the supply end of two parallel 110-220 kV lines with one-way supply and at two parallel 110 kV lines with With two-way power supply, transverse differential directional protection can be used mainly in distribution networks.

In this case, in the operating mode of one line, as well as as a backup when operating two lines, protection according to 3.2.110 and 3.2.111 is used. It is possible to turn on this protection or its individual stages for the sum of the currents of both lines (for example, the last stage of zero-sequence current protection) in order to increase its sensitivity to damage to adjacent elements.

It is allowed to use transverse differential directional protection in addition to step current protection of parallel 110 kV lines to reduce the fault shutdown time on the protected lines in cases where, according to speed conditions (see 3.2.108), its use is not mandatory.

3.2.115. If the protection according to 3.2.111-3.2.113 does not satisfy the speed requirement (see 3.2.108), high-frequency and longitudinal differential protection should be provided as the main protection of single and parallel lines with double-sided power supply.

For 110-220 kV lines, it is recommended to carry out basic protection using high-frequency blocking of distance and current directional zero-sequence protection, when this is appropriate due to sensitivity conditions (for example, on lines with branches) or simplification of protection.

If it is necessary to lay a special cable, the use of longitudinal differential protection must be justified by a technical and economic calculation.

To monitor the serviceability of auxiliary protection wires, special devices must be provided.

On 330-350 kV lines, in addition to high-frequency protection, the use of a device for transmitting a tripping or permissive high-frequency signal (to accelerate the action of step backup protection) should be provided, if this device is provided for other purposes. On 500 kV lines it is allowed to install the specified device specifically for relay protection.

It is allowed in cases where it is required by speed (see 3.2.108) or sensitivity (for example, on lines with branches), the use of transmission of a tripping signal to accelerate the action of step protection of 110-220 kV lines.

3.2.116. When performing basic protection according to 3.2.115, the following should be used as backup:

• against multiphase short circuits, as a rule, distance protection, mainly three-stage;
• against ground faults, step current directional or non-directional zero sequence protection.

In case of long-term deactivation of the main protection specified in 3.2.115, when this protection is installed according to the requirement of quickly disconnecting the fault (see 3.2.108), it is allowed to provide for non-selective acceleration of backup protection against faults between phases (for example, with control of the direct voltage value sequences).

3.2.117. The main protections, high-speed stages of backup protection against multiphase faults and the measuring elements of the automatic reclosure device for 330-350 kV lines must be of a special design that ensures their normal functioning (with the specified parameters) under conditions of intense transient electromagnetic processes and significant capacitive conductivity of the lines. For this purpose the following must be provided:

• in protection kits and OAPV measuring elements - measures limiting the influence of transient electromagnetic processes (for example, low-frequency filters);
• in differential-phase high-frequency protection installed on lines longer than 150 km, devices for compensating currents caused by the capacitive conductivity of the line.

When switching on high-speed protection for the sum of the currents of two or more current transformers, if it is impossible to meet the requirements of 3.2.29, it is recommended to take special measures to prevent unnecessary operation of the protection in the event of external damage (for example, hardening of the protection) or install a separate set of current transformers in the line circuit to power the protection .

In protections installed on 330-500 kV lines equipped with longitudinal capacitive compensation devices, measures must be taken to prevent excessive operation of the protection in the event of external damage caused by the influence of these devices. For example, negative sequence power direction relays or enable signal transmission may be used.

3.2.118. In the case of using OAPV, relay protection devices must be designed so that:

1) in case of ground faults of one phase, and in some cases also in case of faults between two phases, only one phase was disconnected (followed by its automatic reconnection);

2) in case of unsuccessful reconnection due to the damage specified in clause 1, one or three phases were disconnected, depending on whether a long-term, single-phase operation of the line was provided for or not;

3) for other types of damage, the protection acted to disconnect three phases.

Busbar protection, protection on bypass, busbar and sectional switches

3.2.119. For busbars of 110 kV and above power plants and substations, separate relay protection devices must be provided:

1) for two bus systems (double bus system, one-and-a-half scheme, etc.) and a single sectional bus system;

2) for a single non-sectional bus system, if disconnecting faults on the buses by the action of protection of the connected elements is unacceptable under conditions that are similar to those given in 3.2.108, or if there are branches on the lines supplying the buses in question.

3.2.120. For busbars of 35 kV power plants and substations, separate relay protection devices must be provided:

• according to the conditions given in 3.2.108;
• for two systems or sections of buses, if, when using protection installed on the bus connecting (sectional) switch to separate them, or protection installed on the elements that power these buses, the requirements for reliability of power supply to consumers are not met (taking into account the capabilities provided by automatic reclosure devices and AVR).

3.2.121. To protect the busbars of power plants and substations of 35 kV and above, as a rule, differential current protection without time delay should be provided, covering all elements that are connected to the bus system or section. Protection should be carried out using special current relays, tuned from transient and steady-state unbalance currents (for example, relays connected through saturable current transformers, relays with braking).

When connecting a transformer (autotransformer) of 330 kV and higher through more than one switch, it is recommended to provide differential current protection for the busbar.

3.2.122. For double busbar systems of power plants and substations of 35 kV and above with one circuit breaker per connected element, differential protection must be provided in a design for fixed distribution of elements.

In the protection of busbars of 110 kV and above, it should be possible to change the fixation when transferring the connection from one busbar system to another on the rows of terminals.

3.2.123. The differential protection specified in 3.2.121 and 3.2.122 must be carried out with a device that monitors the health of the secondary circuits of the current transformers involved, acting with a time delay to remove the protection from operation and to the signal.

3.2.124. For sectional buses of 6-10 kV power plants, two-stage incomplete differential protection must be provided, the first stage of which is made in the form of current cut-off for current and voltage or distance protection, and the second - in the form of maximum current protection. The protection should act to disconnect the power supply elements and the transformer for its own needs.

If the specified implementation of the second stage of protection does not provide the required sensitivity during a short circuit at the end of the fed reacted lines (the load on the generator voltage buses is large, the switches of the fed lines are installed behind the reactors), it should be performed in the form of separate sets of overcurrent protection with or without voltage start installed in reactor circuits; the effect of these kits on disconnecting the supply elements must be controlled additional device, triggered when a short circuit occurs. In this case, protection must be provided on the sectional switch (intended to eliminate damage between the reactor and the switch), which is put into operation when this switch is turned off. When allocating part of the power elements to backup system busbars must be provided with incomplete differential busbar protection in a design for a fixed distribution of elements.

If frequent operating modes with the division of power elements into different systems buses, it is allowed to provide separate distance protection installed on all power supply elements, except generators.

3.2.125. For sectional buses of 6-10 kV power plants with generators with a capacity of 12 MW or less, it is allowed not to provide special protection; in this case, the elimination of short circuits on the busbars should be carried out by the action of maximum current protection of generators.

3.2.126. Special relay protection devices for single sectionalized and double bus systems of 6-10 kV step-down substations, as a rule, should not be provided, and the elimination of short circuits on the buses should be carried out by the action of transformer protection against external short circuits and protection installed on the sectional or bus connecting switch. In order to increase the sensitivity and speed up the action of protecting the buses of powerful substations, it is allowed to use protection included for the sum of the currents of the supply elements. If there are reactors on lines extending from substation buses, it is possible to protect the buses in a similar way to the protection of power plant buses.

3.2.127. If there are current transformers built into the circuit breakers, for differential protection of the busbars and for the protection of connections extending from these busbars, current transformers must be used, located on different sides of the circuit breaker, so that faults in the circuit breaker are included in the coverage areas of these protections.

If the circuit breakers do not have built-in current transformers, then, in order to save money, remote current transformers should be provided only on one side of the circuit breaker and, if possible, installed so that the circuit breakers are within the coverage area of ​​the busbar differential protection. At the same time, in protecting a double bus system with a fixed distribution of elements, the use of two current transformer cores in the bus coupling circuit breaker circuit must be provided.

When using separate distance protections as busbar protection, the current transformers of these protections in the sectional switch circuit must be installed between the busbar section and the reactor.

3.2.128. Busbar protection should be carried out in such a way that when testing a damaged system or busbar section, selective shutdown of the system (section) is ensured without a time delay.

3.2.129. On a bypass switch of 110 kV and above, in the presence of a busbar (sectional) switch, protection must be provided (used when checking and repairing the protection, switch and current transformers of any of the elements connected to the busbars);

• three-stage distance protection and current cutoff against multiphase short circuits;
• four-stage current directional zero-sequence protection against ground fault.

In this case, protection must be provided on the bus connecting (sectional) switch (used to separate systems or sections of buses in the absence of a breaker failure failure or to remove it or protect buses from action, as well as to increase the efficiency of long-distance backup):

• two-stage current protection against multiphase short circuits;
• three-stage zero-sequence current protection against ground faults.

It is allowed to install more complex protections on the bus-connection (sectional) switch, if this is required to increase the efficiency of long-distance backup.

The bus-coupling (sectional) switch of 110 kV and higher, which is also intended to perform the function of a bypass switch, must be provided with the same protections as the bypass and bus-coupling (sectional) switches when they are designed separately.

The 3-35 kV bus-connection (sectional) switch must be provided with two-stage current protection against multi-phase short circuits.

3.2.130. A separate protection panel, designed specifically for use instead of the line protection being tested, should be provided for circuits electrical connections, in which there is no bypass switch (for example, a quadrangle, a 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.

Protection of synchronous compensators

3.2.131. Relay protection devices for synchronous compensators should be designed similarly to those provided for turbogenerators of the corresponding power with the following differences:

1. Protection against currents caused by symmetrical overload acting on the signal must be output during the starting period, if its operation is possible in this mode.

2. Minimum voltage protection should be provided for tripping the synchronous compensator circuit breaker. The protection response voltage should be taken equal to 0.1-0.2 Unom, time delay - about 10 s.

3. Protection must be provided that operates in the event of a short-term loss of power to the substation (for example, during a dead-time period of automatic reclosure of the supply line). The protection must be in the form of minimum frequency protection and act on tripping the synchronous compensator circuit breaker or on the AGP. It is possible to use protection made on other principles, for example, reacting to the speed of frequency reduction.

4. On synchronous compensators with a power of 50 Mvar or more, protection against loss of excitation (reduction of the excitation current below the permissible limit) should be provided with the effect of turning off the synchronous compensator or the signal. For synchronous compensators, which provide the possibility of switching to an operating mode with negative rotor current, this protection may not be used.

5. For a synchronous compensator operating in a block with a transformer, in the event of a ground fault in the stator winding, the protection installed on the low voltage side of the transformer must be provided.

If the ground fault current on the low voltage side of the transformer exceeds 5 A, it is permissible not to install an arc suppression reactor and perform protection with two time delays; with a shorter time delay, the synchronous compensator switch is turned off, and with a longer time, a signal is supplied.

For a ground fault current of up to 5 A, protection must be performed with one time delay and with an effect on the signal. For synchronous compensators with a power of 50 Mvar or more, the possibility of signal or shutdown protection must be provided.

3.2.132. At substations without constant personnel duty, protection against overload of the synchronous compensator must be carried out with an independent time delay and act with a shorter time delay on the signal and reduction of the excitation current, and with a larger time delay on turning off the synchronous compensator (if the prevention of long-term overloads is not ensured by automatic excitation control devices) .

3.2.133. Protection against ground faults in the excitation circuit of a synchronous compensator should be performed in the same way as for hydraulic generators (see 3.2.85).

To transfer electricity from the supplier to the consumer in Lately The most common method is to lay cables in the ground. The advantages of laying cables in the ground are certainly obvious - high reliability. But the downside in this case is the complexity of the repair, so all work must be carried out in accordance with the requirements of SNiP and taking into account the PUE.

Cable laying underground is carried out in compliance with the following steps:

1. Selecting a route location.
2. Preparing the trench.
3. Preparing for cable laying.
4. Cable selection.
5. Cabling.
6. Line protection. Laying signal tape.
7. Checking the line for current leakage.
8. Backfilling the line.

Each stage has its own specific requirements that must be complied with. Let's look at them in more detail.

Requirements when choosing a route location

At this stage, to begin with, the project for laying cables in the ground must be approved by the local administration. When choosing the location for laying the route, it is necessary to take into account a number of factors, such as the proximity of other communications, the intersection of parks and squares by the cable line, the presence of buildings and facilities for utility purposes along the cable line laying path, and be guided by the following provisions of the PUE and SNiP:

• PUE 2.3.85 The distance from a cable laid directly in the ground to the foundations of buildings and structures must be at least 0.6 m. Laying cable lines under the foundations of buildings and structures is prohibited.
• PUE 2.3.87 When laying cable lines in parks and squares, the distance from the cable to trees and bushes should be 2 m. In order to reduce the distance, it is necessary to obtain approval from the city green farms responsible for the plantings; the distance can be reduced to 0. 75m.
• PUE 2.3.88, 89 The distance from the cable laying line to the sewerage and water supply lines, as well as low and medium pressure gas pipelines is 1 m, and to the gas pipeline line high pressure not less than 2m.
• PUE clauses 2.3.94 and 2.3.95 If it is planned to intersect cable laying lines with other cable lines or oil or gas pipeline lines, then the thickness of the earth between the lines must be at least 0.5 m.
• PUE 2.3.97 Cable laying is carried out in blocks or pipes if the cable laying line is planned to intersect with road or railway tracks.

Requirements for preparing a trench

The planned cable laying depth depends on the power of the cable line, therefore V According to:

• PUE clause 2.3.84 cable lines up to 20 kV should be laid to a depth of 0.7 m, up to 35 kV - 1 m, with streets and squares - 1 m, regardless of voltage, oil-filled cable lines should be laid to a depth of 1.5 m. It is possible to reduce the depth of the route to 0.5 m and a length of 5 m to enter the cable into buildings or when crossing the line with other underground structures, if the cables themselves are protected from damage.

Requirements when preparing to lay cables

This stage of work requires the involvement of surveyors. And here the following requirements must be met:

• SNiP clause 3.66 states that you must first inspect the trench to identify places that could destroy the cable. This could be salt marshes, water, sharp objects (slag or construction waste). You also need to ensure that the cable does not pass closer than 2 m from the cesspools. If all requirements cannot be met, then the cable must be laid in an asbestos-cement pipe coated with a bitumen compound. To do this, the trench needs to be expanded.
• PUE 2.3.83 indicates that a sand cushion must be poured onto the bottom of the trench. The pillow should be compacted. In general, each layer of soil must be compacted when laying cables. If large or sharp inclusions accidentally get into the cushion, they can damage the cable during compaction.

Requirements when choosing a cable

Choice the right type cable, of course, has a huge impact on the lifespan of cable routes as a whole. Here you must be guided by the following requirement:

• PUE 2.3.37. For cable lines laid in the ground, armored cables must be used.

The cable is marked in the technical documents, which states that it is intended for installation in the ground. These cables are suitable for tunnels and fire-hazardous channels if there is no mechanical stress on the cable. In addition, the armored cable has protection in the form of steel braiding from rodents and mechanical influences. If there is a gasket electric cable in the ground, then for such a cable it is not necessary to protect it with an armored pipe. It is more expensive than other brands, but it is the only one suitable for laying in the ground.

As a rule, cables are laid in a trench from a drum and the following rules must be observed:

• SNiP clause 3.58 When laying a cable from a drum, the winches from which the drum is untwisted must be equipped with a special limiting device so that the cable lies with reserve and not under tension
• SNiP clause 3.59 The cable reserve should be 1-2%. Do not lay the cable in a snake or leave loops!
• PUE clause 2.3.100 Cable lines are connected to each other by couplings. The distance between the cable and the coupling should be 250mm.

Protection of lines is a prerequisite when laying an electrical cable in the ground, but even in this case there are some nuances:

• PUE clause 3.67 In places where cable lines enter buildings, the line itself is placed in an asbestos-cement sleeve, which should protrude 0.6 m from the wall in both directions.
• PUE clause 2.3.83 Throughout the entire length of the cable, the cable must be protected from damage by an asbestos-cement pipe or a brick structure laid across the position of the cable. This will help protect the cable from ground subsidence. You cannot protect the line with hollow or perforated bricks. If several cables are laid in a trench, then the distance between them should be: 100 mm between cables up to 10 kV, 250 mm between cables 20-35 kV, 500 mm between cables belonging to different organizations or oil-filled cables.
• SNiP clause 3.70. The cable laid in the trench must be covered with a layer of earth and mechanical protection or warning tape must be laid.
• PUE clause 2.3.83 The signal tape should not be laid directly on the cable. The vertical distance from the cable to the tape must be at least 250mm. If there are several cables in a line, then the tapes should be laid with an overlap of 5 cm. The width of the signal tape is 150 mm.
• PUE2.3.92 If the cable line crosses other communications, the warning tape must be laid at a distance of at least 2 m from the other communications.

Requirements for checking the line in case of current leakage.

• PUE clause 2.3.101 If the soil is dangerous, then it is necessary to apply leakage protection in areas with leaks: replace cable sections with samples resistant to electrical corrosion or change the route to bypass dangerous areas
• SNiP clause 2.3101 When laying a route in aggressive soils, cathodic polarization must be used (installation of protectors, electrical drains, cathodic protection).
• SNiP clause 3.70 After checking the line for current leakage is completed, the customer, together with electricians and representatives of the construction organization, draws up an act for hidden work. This is the main document according to which the road repairs will be carried out.

Requirements for backfilling a line

At this last stage the following is observed:

• SNiP clause 3.71 After testing the line with increased voltage, the trench must be completely backfilled.
• SNiP clause 3.72 In no case is it allowed to fill the trench with frozen soil, as well as soil that contains stones and metal.

Prices for laying cables in the ground

If work such as laying cables in the ground is planned, the price may vary depending on the conditions under which the installation takes place. When laying a cable line, it is necessary to draw up at least an approximate estimate of the upcoming work and costs of materials.

When laying cables in the ground, prices can vary greatly depending on the region in which the work is carried out, but the items for which estimates are drawn up will be approximately the same everywhere:

1. Opening a warrant for earthworks.
2. Soil development.
3. Laying cables in prepared trenches.
4. Pillow device.
5. Cutting seams in road surfaces.
6. Installation work on installation of end couplings.
7. Laying asbestos cement pipes.
8. Drilling holes for cable entry.
9. Cable entry into the building.
10. Arrangement of intersections of pipelines and gas pipelines.
11. Construction of compacted soil layers.
12. Backfilling of soil.
13. Calling an ISS representative to inspect the cable and trench.
14. Calling tracers to draw a line on control panel plans.

Chapter 2.3

Amended by decision of the Ministry of Fuel and Energy dated July 13, 1998 (paragraph 2.3.24)

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 of higher voltages are carried out according to special projects. Additional requirements for cable lines are given in Chapter. 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 closed and buried (partially or completely) impenetrable structure in the ground, floor, ceiling, etc., designed to accommodate cables, the installation, inspection and repair of which can only be done 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. The cable rack can be pass-through or non-pass-through.

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's 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/cm2) for low-pressure lead-sheathed cables;
- 0.0245-0.49 MPa (0.25-5.0 kgf/cm 2) for low pressure cables in an aluminum sheath;
- 1.08-1.57 MPa (11-16 kgf/cm 2) 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 outermost 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; It is prohibited to lay cable reserves in the form of rings (turns);
— 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 the ground;
— 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, while protection of the cables from the breakthrough of hot substances in 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 couplings, must be equipped with tags with the designation on the cable tags and end couplings brand, voltage, section, number or name of the line; on the tags couplings- coupling numbers and installation dates. Tags must be resistant to environmental influences. 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. (see Appendix "Requirements for information signs and their installation")

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 of 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 distribution facilities, 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, one should take into account the physical phenomena associated with the nature of permafrost: heaving soil, frost cracks, landslides, etc. Depending on local conditions, cables can be laid in the ground (in trenches) below the active layer, in active layer in dry, well-draining soils, in artificial embankments made of large-skeletal dry imported soils, in trays on the surface of the earth, 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 a flat surface with a slope of no more than 0.2%, ensuring surface water drainage. Cable ducts should be made of waterproof reinforced concrete and covered on the outside with 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 in different soils and environmental conditions, the choice of cable designs and sections should be made along the section with the most severe conditions, if the length of sections with easier conditions does not exceed the construction length of the cable. If there are significant lengths of individual sections of the route with different laying conditions, appropriate designs and cable sections should be selected for each of them.

2.3.36. For cable lines laid along routes with different cooling conditions, cable cross-sections should be selected along a section of the route with worse conditions cooling, 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 not more than three, provided that the length of the shortest section 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 production 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 unarmored 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 installation in soils containing substances that have a destructive effect on cable sheaths (salt marshes, swamps, bulk soil with slag and building material etc.), as well as in areas dangerous due to the effects of electrocorrosion, cables with lead sheaths and reinforced protective covers of types B l, B 2l or cables with aluminum shells and especially reinforced protective covers of types B v, B should be used n (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 impregnation must be used 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 networks alternating current(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 reliable fastening of cables in insulating clips.

FEEDING DEVICES AND OIL PRESSURE ALARM FOR CABLE OIL-FILLED LINES

2.3.54. The oil feeding system must provide reliable operation lines 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 feeding tanks (5-6) at open feeding points in light metal boxes on portals, supports, etc. (at an ambient temperature of at least 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 permanent staff on duty. 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 manifold 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 switchboard room with devices for automatic control of the feeding unit should not exceed permissible limits.

CABLE CONNECTIONS AND TERMINATIONS

2.3.65. When connecting and terminating power cables, coupling designs that comply with their operating and environmental conditions should be used. Connections and terminations on cable lines must be made in such a way 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 can withstand the test voltages for the cable line and comply with GOST requirements.

2.3.66. For cable lines up to 35 kV, end and connecting 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 couplings of low-pressure oil-filled cable lines, only brass or copper couplings should be used.

The length of sections and installation locations of locking couplings on low-pressure oil-filled cable lines are determined taking into account the replenishment of the lines with oil in normal and transient thermal conditions.

Stop and half-stop couplings on oil-filled cable lines must be placed in cable wells; When laying cables in the ground, it is recommended to place connecting couplings in chambers that are subject to subsequent backfilling with sifted earth or sand.

In areas with electrified transport (metropolitan, trams, railways) or with soils that are aggressive to the metal shells and couplings of cable lines, the couplings must be accessible for inspection.

2.3.68. On cable lines made with cables with normally impregnated paper insulation and cables impregnated with a non-drip compound, cable connections must be made using stop-transition couplings if the laying level of cables with normally impregnated insulation is higher than the laying level of cables impregnated with a non-drip compound (see also 2.3 .51).

2.3.69. On cable lines above 1 kV, made with flexible cables with rubber insulation in a rubber hose, cable connections must be made by hot vulcanization and coated with anti-damp varnish.

2.3.70. The number of couplings per 1 km of newly constructed cable lines should be no more than: for three-core cables 1-10 kV with a cross-section of up to 3x95 mm 2 4 pcs.; for three-core cables 1-10 kV with sections 3x120 - 3x240 mm 2 5 pcs.; for three-phase cables 20-35 kV 6 pcs.; for single-core cables 2 pcs.

For cable lines 110-220 kV, the number of connecting couplings is determined by the design.

The use of undersized cable sections for the construction of long cable lines is not permitted.

GROUNDING

measurement of resistance of conductors connecting to the ground and potential equalization (metal connection) (2p); measuring the resistance of grounding devices using a three-pole circuit (3p); measuring the resistance of grounding devices using a four-pole circuit (4p); measuring the resistance of multiple grounding devices without breaking the grounding circuit (using current clamps); measuring the resistance of grounding devices using the two-clamp method; measuring the resistance of lightning protection (lightning rods) using a four-pole circuit using the pulse method; AC current measurement (leakage current); measurement resistivity soil using the Wenner method with the ability to select the distance between the measuring electrodes; high noise immunity;

2.3.71. Cables with metal sheaths or armor, as well as cable structures on which cables are laid, must be grounded or neutralized in accordance with the requirements given in Chapter. 1.7.

2.3.72. When grounding or neutralizing the metal sheaths of power cables, the sheath and armor must be connected by a flexible copper wire between each other and with coupling bodies (end couplings, connecting couplings, etc.). On cables of 6 kV and above with aluminum sheaths, grounding of the sheath and armor must be carried out with separate conductors.

It is not required to use grounding or neutral protective conductors with a conductivity greater than the conductivity of the cable sheaths, however, the cross-section in all cases must be at least 6 mm.

The cross-sections of grounding conductors of control cables should be selected in accordance with the requirements of 1.7.76-1.7.78.

If an external end coupling and a set of arresters are installed on the structure support, then the armor, metal shell and coupling must be connected to the grounding device of the arresters. In this case, using only metallic cable sheaths as a grounding device is not allowed.

Overpasses and galleries must be equipped with lightning protection in accordance with RD 34.21.122-87 "Instructions for the installation of lightning protection of buildings and structures" of the USSR Ministry of Energy.

2.3.73. On oil-filled low-pressure cable lines, the end, connecting and locking couplings are grounded.

On cables with aluminum sheaths, feeders must be connected to the lines through insulating inserts, and the housings of the end couplings must be insulated from the aluminum sheaths of the cables. This requirement does not apply to cable lines with direct input into transformers.

When using armored cables for low-pressure oil-filled cable lines in each well, the cable armor on both sides of the coupling must be welded and grounded.

2.3.74. The steel pipeline of oil-filled high-pressure cable lines laid in the ground must be grounded in all wells and at the ends, and those laid in cable structures - at the ends and at intermediate points determined by calculations in the project.

If it is necessary to actively protect a steel pipeline from corrosion, its grounding is carried out in accordance with the requirements of this protection, and it must be possible to control electrical resistance anti-corrosion coating.

2.3.75. When a cable line transitions into an overhead line (OHL) and if there is no grounding device at the overhead line support, the cable couplings (mast) can be grounded by attaching the metal sheath of the cable, if the cable coupling at the other end of the cable is connected to a grounding device or the grounding resistance of the cable sheath complies with the requirements of Chapter. 1.7.

SPECIAL REQUIREMENTS FOR CABLE FACILITIES OF POWER PLANTS, SUBSTATIONS AND DISTRIBUTION DEVICES

2.3.76. The requirements given in 2.3.77-2.3.82 apply to cable facilities of thermal and hydroelectric power plants with a capacity of 25 MW or more, switchgears and substations with a voltage of 220-500 kV, as well as switchgears and substations of particular importance in the power system (see. also 2.3.113).

2.3.77. The main electrical connection diagram, the auxiliary diagram and the operating current diagram, equipment control and layout of the equipment and cable management of a power plant or substation must be carried out in such a way that in the event of fires in the cable management or outside it, disruptions to the operation of more than one unit of the power plant are excluded, simultaneous loss of mutually redundant connections of switchgears and substations, as well as failure of fire detection and extinguishing systems.

2.3.78. For the main cable flows of power plants, cable structures (floors, tunnels, shafts, etc.) must be provided, isolated from the process equipment and preventing access to the cables by unauthorized persons.

When placing cable flows at power plants, cable routes must be selected taking into account:

— preventing overheating of cables from heated surfaces of technological equipment;
- preventing damage to cables during dust exhausts (fires and explosions) through safety devices dust systems;
— preventing the laying of transit cables in hydraulic ash removal technological tunnels, chemical water treatment rooms, as well as in places where pipelines with chemically aggressive liquids are located.

2.3.79. Mutually redundant critical cable lines (power, operating current, communications, control, alarm systems, fire extinguishing systems, etc.) must be laid in such a way that during fires the possibility of simultaneous loss of mutually redundant cable lines is excluded. In areas of cable facilities where the occurrence of an accident threatens its further development, cable flows should be divided into groups isolated from one another. The distribution of cables into groups depends on local conditions.

2.3.80. Within one power unit, it is permitted to construct cable structures with a fire resistance limit of 0.25 hours. In this case, technological equipment that can serve as a source of fire (oil tanks, oil stations, etc.) must have fences with a fire resistance limit of at least 0.75 h, eliminating the possibility of cables catching fire in the event of a fire on this equipment.

Within one power unit of a power plant, it is permitted to lay cables outside special cable structures, provided that they are reliably protected from mechanical damage and dust, from sparks and fire during repairs of process equipment, and that normal temperature conditions for cable lines are ensured and their maintenance is convenient.

To provide access to cables when they are located at a height of 5 m or more, special platforms and passages must be constructed.

For single cables and small groups of cables (up to 20), operational platforms may not be constructed, but it must be possible to quickly replace and repair cables under operating conditions.

When laying cables within one power unit outside special cable structures, it should be ensured, if possible, that they are divided into separate groups running along different routes.

2.3.81. Cable floors and tunnels in which cables of various power units of a power plant are located, including cable floors and tunnels under block control panels, must be divided block by block and separated from other rooms, cable floors, tunnels, shafts, ducts and channels by fireproof partitions and ceilings with a fire resistance limit not less than 0.75 hours, including in places where cables pass.

In places where cables are supposed to pass through partitions and ceilings, in order to ensure the possibility of replacement and additional laying of cables, a partition made of fireproof, easily pierced material with a fire resistance rating of at least 0.75 hours must be provided.

In extended cable structures of thermal power plants, emergency exits must be provided, located, as a rule, at least every 50 m.

Cable facilities of power plants must be separated from outgoing network cable tunnels and collectors by fireproof partitions with a fire resistance rating of at least 0.75 hours.

2.3.82. The entry points of cables into the rooms of closed switchgears and into the rooms of control and protection panels of open switchgears must have partitions with a fire resistance rating of at least 0.75 hours.

The entry points of cables to the control panels of the power plant must be closed with partitions with a fire resistance rating of at least 0.75 hours.

Cable shafts must be separated from cable tunnels, floors and other cable structures by fireproof partitions with a fire resistance limit of at least 0.75 hours and have ceilings at the top and bottom. Extended shafts, when passing through ceilings, but at least after 20 m, must be divided into compartments by fireproof partitions with a fire resistance limit of at least 0.75 hours.

Walk-through cable shafts must have entrance doors and be equipped with ladders or special brackets.

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 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.

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* 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 a planted area, the distance from the cables to the tree trunks must, 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) - at least 1 m; to high pressure gas pipelines (more than 0.588 to 1.176 MPa) - at least 2 m; to heating pipes - 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 with outside ditch or the base of the embankment at a distance of at least 1 m from the edge or at least 1.5 m from the curb stone. Reducing the specified distance is allowed in each individual case in agreement with the relevant road 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 must be located above 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, a distance of at least 0.25 m is allowed, but provided that the cables are placed in pipes or reinforced concrete trays with a 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 cable replacement can be done without excavation work (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 standards for potential differences in the suction sections, provided for by SNiP 3.04.03-85 “Protection of building structures and structures from corrosion” of the State Construction Committee of Russia, must be observed. 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 control points on cable lines 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.

LAYING CABLE LINES IN CABLE BLOCKS, PIPES AND REINFORCED CONCRETE TRAYS

2.3.102. For the manufacture of cable blocks, as well as for laying cables in pipes, it is allowed to use steel, cast iron, asbestos-cement, concrete, ceramic and similar pipes. When choosing material for blocks and pipes, you should take into account the level of groundwater and its aggressiveness, as well as the presence of stray currents.

Oil-filled single-phase low-pressure cables must be laid only in asbestos-cement and other pipes made of non-magnetic material, and each phase must be laid in a separate pipe.

2.3.103. The permissible number of channels in blocks, the distances between them and their size must be taken in accordance with 1.3.20.

2.3.104. Each cable unit must have up to 15% redundant channels, but not less than one channel.

2.3.105. The depth of installation of cable blocks and pipes in the ground must be taken according to local conditions, but not be less than the distances given in 2.3.84, counting to the top cable. The depth of installation of cable blocks and pipes in closed areas and in the floors of industrial premises is not standardized.

2.3.106. Cable blocks must have a slope of at least 0.2% towards the wells. The same slope must be observed when laying pipes for cables.

2.3.107. When laying pipes for cable lines directly in the ground, the smallest clear distances between pipes and between them and other cables and structures should be taken as for cables laid without pipes (see 2.3.86).

When laying cable lines in pipes in the floor of a room, the distances between them are taken as for laying in the ground.

2.3.108. In places where the direction of the route of cable lines laid in blocks changes, and in places where cables and cable blocks pass into the ground, cable wells should be constructed to ensure convenient pulling of cables and their removal from the blocks. Such wells should also be constructed on straight sections of the route at a distance from one another determined by the maximum permissible tension of the cables. When the number of cables is up to 10 and the voltage is not higher than 35 kV, the transition of cables from blocks to the ground can be carried out without cable wells. In this case, the places where cables exit from the blocks must be sealed with waterproof material.

2.3.109. The transition of cable lines from blocks and pipes to buildings, tunnels, basements, etc. must be carried out by one of following methods: by directly inserting blocks and pipes into them, constructing wells or pits inside buildings or chambers near their outer walls.

Measures must be taken to prevent the penetration of water and small animals from trenches into buildings, tunnels, etc. through pipes or openings.

2.3.110. The channels of cable blocks, pipes, their outlets, as well as their connections must have a treated and cleaned surface to prevent mechanical damage to the cable sheaths during pulling. At cable exits from blocks to cable structures and chambers, measures must be taken to prevent damage to the sheaths from abrasion and cracking (use of elastic linings, compliance with the required bending radii, etc.).

2.3.111. If the groundwater level is high on the territory of the outdoor switchgear, preference should be given to above-ground methods of laying cables (in trays or boxes). Aboveground trays and slabs for their covering must be made of reinforced concrete. Trays must be laid on special concrete pads with a slope of at least 0.2% along the planned route in such a way as not to interfere with drainage storm water. If there are openings in the bottoms of the above-ground gutters that allow for the release of storm water, there is no need to create a slope.

When using cable trays for laying cables, passage through the territory of the outdoor switchgear and access to the equipment of machines and mechanisms necessary for performing repair and maintenance work must be ensured. For this purpose, crossings over the trays must be arranged using reinforced concrete slabs, taking into account the load from passing traffic, while maintaining the location of the trays at the same level. When using cable trays, laying cables under roads and crossings in pipes, channels and trenches located below the trays is not allowed.

The cable exit from the trays to the control and protection cabinets must be carried out in pipes that are not buried in the ground. Laying cable jumpers within one open switchgear cell is allowed in a trench, and in this case the use of pipes to protect cables when connecting them to control and relay protection cabinets is not recommended. Cables must be protected from mechanical damage by other means (using an angle, channel, etc.).

LAYING CABLE LINES IN CABLE STRUCTURES

2.3.112. Cable structures of all types must be carried out taking into account the possibility of additional laying of cables in the amount of 15% of the number of cables provided for by the project (replacement of cables during installation, additional laying in subsequent operation, etc.).

2.3.113. Cable floors, tunnels, galleries, overpasses and shafts must be separated from other rooms and adjacent cable structures by fireproof partitions and ceilings with a fire resistance limit of at least 0.75 hours. Extended tunnels must be divided by the same partitions into compartments no more than 150 m long, if available power and control cables and no more than 100 m in the presence of oil-filled cables. The area of ​​each double floor compartment should be no more than 600 m2.

Doors in cable structures and partitions with a fire resistance limit of 0.75 hours must have a fire resistance limit of at least 0.75 hours in electrical installations listed in 2.3.76, and 0.6 hours in other electrical installations.

Exits from cable structures must be provided outside or into premises with production facilities of categories D and D. The number and location of exits from cable structures must be determined based on local conditions, but there must be at least two. If the length of the cable structure is no more than 25 m, it is allowed to have one output.

Doors of cable structures must be self-closing, with sealed doorways. Exit doors from cable structures must open outward and must have locks that can be unlocked from cable structures without a key, and doors between compartments must open in the direction of the nearest exit and be equipped with devices that keep them in the closed position.

Walk-through cable racks with service bridges must have entrances with stairs. The distance between the entrances should be no more than 150 m. The distance from the end of the overpass to the entrance to it should not exceed 25 m.

Entrances must have doors that prevent free access to the overpasses for persons not involved in cable maintenance. Doors must have self-locking locks that can be opened without a key from the inside of the overpass.

The distance between the entrances to the cable gallery when laying cables no higher than 35 kV in it should be no more than 150 m, and when laying oil-filled cables - no more than 120 m.

External cable racks and galleries must have main load-bearing building structures (columns, beams) made of reinforced concrete with a fire resistance limit of at least 0.75 hours or rolled steel with a fire resistance limit of at least 0.25 hours.

Load-bearing structures of buildings and structures that can be dangerously deformed or reduce mechanical strength when groups (streams) of cables laid near these structures on external cable overpasses and galleries burn, must have protection that provides a fire resistance limit of the protected structures of at least 0.75 hours.

Cable galleries must be divided into fireproof sections fire partitions with a fire resistance rating of at least 0.75 hours. The length of the gallery compartments should be no more than 150 m when laying cables up to 35 kV and no more than 120 m when laying oil-filled cables. The above requirements do not apply to external cable galleries that are partially closed.

2.3.114. In tunnels and canals, measures must be taken to prevent process water and oil from entering them, and drainage of soil and storm water must also be ensured. The floors in them must have a slope of at least 0.5% towards the water collectors or storm drains. The passage from one tunnel compartment to another, when they are located at different levels, must be carried out using a ramp with an inclination angle of no higher than 15°. The construction of steps between tunnel compartments is prohibited.

In cable channels constructed outdoors and located above the groundwater level, an earthen bottom with a drainage bedding 10-15 cm thick of compacted gravel or sand is allowed.

Drainage mechanisms must be provided in tunnels; In this case, it is recommended to use automatic start-up depending on the water level. Starting devices and electric motors must be designed to allow them to operate in particularly damp places.

When crossing overpasses and walk-through galleries from one mark to another, a ramp must be made with a slope of no more than 15°. As an exception, staircases with a slope of 1:1 are allowed.

2.3.115. Cable ducts and double floors in switchgears and rooms must be covered with removable fireproof slabs. In electrical machinery and similar rooms, it is recommended to cover the channels with corrugated steel, and in control panel rooms with parquet floors - with wooden boards with parquet, protected from below with asbestos and asbestos with tin. The covering of ducts and double floors must be designed to allow the movement of related equipment over it.

2.3.116. Cable ducts outside buildings must be backfilled on top of removable slabs with a layer of earth at least 0.3 m thick. In fenced areas, backfilling of cable ducts with earth on top of removable slabs is not necessary. Weight separate slab overlap, removed manually, should not exceed 70 kg. The slabs must have a lifting device.

2.3.117. In areas where molten metal may be spilled, liquids containing high temperature or substances that have a destructive effect on the metal sheaths of cables, the construction of cable channels is not allowed. In these areas, it is also not allowed to install hatches in sewers and tunnels.

2.3.118. Underground tunnels outside buildings must have a layer of earth at least 0.5 m thick on top of the ceiling.

2.3.119. When laying cables and heat pipes together in buildings, additional heating of the air by the heat pipe at the location of the cables at any time of the year should not exceed 5°C, for which ventilation and thermal insulation on the pipes must be provided.

1. Control cables and communication cables should be placed only under or only above power cables; however, they should be separated by a partition. At intersections and branches, it is allowed to lay control cables and communication cables above and below power cables.
2. Control cables may be laid next to power cables up to 1 kV.
3. Power cables up to 1 kV are recommended to be laid over cables above 1 kV; however, they should be separated by a partition.
4. Various groups of cables: working and backup cables above 1 kV of generators, transformers, etc., supplying power receivers of category I, it is recommended to be laid at different horizontal levels and separated by partitions.
5. The dividing partitions specified in paragraphs 1, 3 and 4 must be fireproof with a fire resistance rating of at least 0.25 hours.

When using automatic fire extinguishing using air-mechanical foam or sprayed water, the partitions specified in clauses 1, 3 and 4 may not be installed.

On external cable overpasses and in external partially enclosed cable galleries, the installation of dividing partitions specified in clauses 1, 3 and 4 is not required. In this case, mutually redundant power cable lines (with the exception of lines to electrical receivers of special group I category) should be laid with a distance between them of at least 600 mm and are recommended to be located: on overpasses on both sides of the span supporting structure (beams, trusses); in the galleries on opposite sides of the aisle.

2.3.121. Oil-filled cables should, as a rule, be laid in separate cable structures. It is allowed to lay them together with other cables; in this case, oil-filled cables should be placed in the lower part of the cable structure and separated from other cables by horizontal partitions with a fire resistance limit of at least 0.75 hours. The same partitions should be used to separate oil-filled cable lines from one another.

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

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

2.3.123. In cable structures, the laying of control cables and power cables with a cross-section of 25 mm 2 or more, with the exception of unarmored cables with a lead sheath, should be carried out according to cable structures(consoles).

Control unarmored cables, power unarmored cables with a lead sheath and unarmored power cables of all designs with a cross-section of 16 mm 2 or less should be laid on trays or partitions (solid or non-solid).

It is allowed to lay cables along the bottom of the channel with a depth of no more than 0.9 m; in this case, the distance between a group of power cables above 1 kV and a group of control cables must be at least 100 mm, or these groups of cables must be separated by a fireproof partition with a fire resistance rating of at least 0.25 hours.

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

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

In cable structures, the height, width of passages and the distance between structures and cables must be no less than those given in table. 2.3.1. Compared to the distances given in the table, a local narrowing of passages up to 800 mm or a reduction in height to 1.5 m over a length of 1.0 m is allowed with a corresponding reduction in the vertical distance between cables for one-sided and two-sided structures.

Table 2.3.1. Shortest distance for cable structures

2.3.124. Laying of control cables is allowed in bundles on trays and in multilayers in metal boxes, subject to the following conditions:

1. Outside diameter the cable bundle should be no more than 100 mm.
2. The height of the layers in one box should not exceed 150 mm.
3. Only cables with the same type of sheaths should be laid in bundles and multilayers.
4. Fastening of cables in bundles, multilayered in boxes, cable bundles to trays should be done in such a way that deformation of the cable sheaths under the influence of its own weight and fastening devices is prevented.
5. For purposes fire safety Fire-barrier belts must be installed inside the boxes: in vertical sections - at a distance of no more than 20 m, as well as when passing through the ceiling; in horizontal sections - when passing through partitions.
6. In each direction of the cable route, a reserve capacity of at least 15% of the total capacity of the boxes should be provided.

Laying power cables in bundles and multi-layers is not allowed.

2.3.125*. In places saturated with underground communications, it is allowed to construct semi-through tunnels with a height reduced in comparison with that provided in the table. 2.3.1, but not less than 1.5 m, subject to the following requirements: the voltage of the cable lines must be no higher than 10 kV; the length of the tunnel should be no more than 100 m; the remaining distances must correspond to those given in the table. 2.3.1; There should be exits or hatches at the ends of the tunnel.

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* Agreed with the Central Committee of the Trade Union of Power Plant and Electrical Industry Workers.

2.3.126. Oil-filled low pressure cables must be secured to metal structures in such a way that the possibility of formation of closed magnetic circuits around the cables is excluded; the distance between fastening points should be no more than 1 m.

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

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

Mechanical supports and fastenings of branching devices on high-pressure lines must prevent swinging of branching pipes and the formation of closed magnetic circuits around them, and insulating gaskets must be provided in places where supports are fastened or touched.

2.3.127. The height of cable wells must be at least 1.8 m; The height of the chambers is not standardized. Cable wells for connecting, locking and semi-locking couplings must have dimensions that ensure installation of the couplings without tearing.

Coastal wells at underwater crossings must be sized to accommodate backup cables and feeders.

A pit must be installed in the floor of the well to collect groundwater and storm water; a drainage device must also be provided in accordance with the requirements given in 2.3.114.

Cable wells must be equipped with metal ladders.

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

2.3.128. Hatches for cable wells and tunnels must have a diameter of at least 650 mm and be closed with double metal covers, the bottom of which must have a device for closing with a lock that can be opened from the side of the tunnel without a key. Covers must have provisions for their removal. Indoors, the use of a second cover is not required.

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

2.3.130. End couplings on high-pressure oil-filled cable lines must be located in rooms with positive air temperatures or be equipped with automatic heating when the ambient temperature drops below +5°C.

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

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

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

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

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

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

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

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

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

The intersection of cable overpasses and galleries with by air lines power transmission lines, intra-factory railways and roads, fire passages, cable cars, overhead communication and radio lines and pipelines are recommended to be performed at an angle of at least 30°.

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

Location of overpasses and galleries in explosive areas- see chap. 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.

LAYING CABLE LINES IN PRODUCTION PREMISES

2.3.134. When laying cable lines in industrial premises, the following requirements must be met:

1. Cables must be accessible for repair, and if laid openly, they must be accessible for inspection.


Cables (including armored ones) located in places where machinery, equipment, cargo and vehicles are moved must be protected from damage in accordance with the requirements given in 2.3.15.

2. The clear distance between the cables must correspond to that given in table. 2.3.1.
3. The distance between parallel power cables and all kinds of pipelines, as a rule, should be at least 0.5 m, and between gas pipelines and pipelines with flammable liquids - at least 1 m. At shorter approach distances and at intersections, the cables must be protected from mechanical damage (metal pipes, casings, etc.) throughout the entire approach area plus 0.5 m on each side, and, if necessary, protected from overheating.

Cable crossings of passages must be carried out at a height of at least 1.8 m from the floor.

Parallel laying of cables above and below oil lines and pipelines with flammable liquid in a vertical plane is not allowed.

2.3.135. Laying of cables in the floor and interfloor ceilings should be done in channels or pipes; Tightly sealing cables in them is not allowed. The passage of cables through ceilings and internal walls can be carried out in pipes or openings; After laying cables, gaps in pipes and openings must be sealed with easily pierced fireproof material.

Laying cables in ventilation ducts is prohibited. It is allowed to cross these channels with single cables enclosed in steel pipes.

Open cable routing in staircases is not permitted.

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 movement of water at the crossing point, prevailing winds, profile and chemical composition bottom, chemical composition of water.

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.

LAYING CABLE LINES IN SPECIAL STRUCTURES

2.3.146. The laying of cable lines on stone, reinforced concrete and metal bridges must be carried out under the pedestrian part of the bridge in channels or in fireproof pipes separate for each cable; measures must be taken to prevent storm water from flowing through these pipes. On metal and reinforced concrete bridges and when approaching them, it is recommended to lay cables in asbestos-cement pipes. In places of transition from bridge structures to the ground, it is recommended to lay cables in asbestos-cement pipes.

All underground cables when passing over metal and reinforced concrete bridges must be electrically insulated from the metal parts of the bridge.

2.3.147. The laying of cable lines on wooden structures (bridges, piers, piers, etc.) must be carried out in steel pipes.

2.3.148. In places where cables pass through expansion joints of bridges and from bridge structures to abutments, measures must be taken to prevent the occurrence of mechanical forces in the cables.

2.3.149. Laying cable lines along dams, dikes, piers and moorings directly in an earthen trench is allowed if the earth layer is at least 1 m thick.

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 a planted area, the distance from the cables to the tree trunks must, 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) - at least 1 m; to high pressure gas pipelines (more than 0.588 to 1.176 MPa) - at least 2 m; to heating pipes - 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.

For electrified roads running on direct current, the 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 the 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 overhead line supports above 1 kV is 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 must be located above 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, a distance of at least 0.25 m is allowed, but provided that the cables are placed in pipes or reinforced concrete trays with a 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 cable replacement can be done without excavation work (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, reserve blocks or pipes with tightly sealed ends should be laid in the required quantity in case of cable repairs.

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 control points on cable lines 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.