Pue edition 7e p 1.5 11. Fig. 1.7.4

For color and digital designation of individual insulated or non-insulated conductors, colors and numbers must be used in accordance with GOST R 50462 “Identification of conductors by colors or digital designations”.

Protective grounding conductors in all electrical installations, as well as neutral protective conductors in electrical installations with voltages up to 1 kV with a solidly grounded neutral, incl. tires must have a letter designation P.E. and color designation by alternating longitudinal or transverse stripes of the same width (for tires from 15 to 100 mm) of yellow and green.

Zero working (neutral) conductors are designated by the letter N and blue color. Combined neutral protective and neutral working conductors must have a letter designation PEN and color designation: blue along the entire length and yellow-green stripes at the ends.

1.1.30

The alphanumeric and color designations of tires of the same name in each electrical installation must be the same.

Tires must be marked:

1) with alternating three-phase current: phase buses A - yellow, phases B - green, phase C - red flowers;

2) with alternating single-phase current bus B , connected to the end of the power source winding, - in red, bus A , connected to the beginning of the power source winding, is yellow.

Single-phase current buses, if they are a branch from the buses of a three-phase system, are designated as the corresponding three-phase current buses;

3) at constant current: positive bus ( + ) - in red, negative ( - ) - blue and zero working M- blue color.

The color coding must be carried out along the entire length of the tires if it is also provided for more intensive cooling or anti-corrosion protection.

It is allowed to carry out a color designation not along the entire length of the busbars, only a color or only an alphanumeric designation, or a color in combination with an alphanumeric designation at the points where the busbars are connected. If non-insulated busbars are not accessible for inspection during the period when they are energized, then they may not be marked. At the same time, the level of safety and visibility when servicing the electrical installation should not be reduced.

1.1.31

When busbars are located “flat” or “edge-on” in switchgears (except for complete prefabricated single-sided service cells (KSO) and complete switchgears (SGD) 6-10 kV, as well as factory-made panels 0.4-0.69 kV) The following conditions must be met:

1. In switchgears with a voltage of 6-220 kV with three-phase alternating current, prefabricated and bypass busbars, as well as all types of sectional busbars, should be located:

a) in a horizontal position:

one below the other: from top to bottom A-B-C ;

one after the other, obliquely or in a triangle: the most distant tire A , average - B C ;

b) with a vertical arrangement (in one plane or in a triangle):

from left to right A-B-C or the most distant bus A , average - B , closest to the service corridor - C ;

c) branches from busbars, if you look at the busbars from the service corridor (if there are three corridors - from the central one):

A-B-C ;

with a vertical arrangement (in one plane or in a triangle): from top to bottom A-B-C .

2. In five- and four-wire three-phase alternating current circuits in electrical installations with voltages up to 1 kV, the arrangement of busbars should be as follows:

when positioned horizontally:

one below the other: from top to bottom A-B-C-N-PE(PEN) ;

one after another: the most distant bus A , then phases B-C-N , closest to the service corridor - PE(PEN) ;

when positioned vertically: from left to right A-B-C-N-PE(PEN) or the most distant bus A , then phases B-C-N , closest to the service corridor - PE(PEN) ;

branches from busbars, if you look at the busbars from the service corridor:

when positioned horizontally: from left to right A-B-C-N-PE(PEN) ;

in a vertical position: A-B-C-N-PE(PEN) top down.

3. With direct current, the buses should be located:

busbars with vertical arrangement: top M , average (-) , lower (+) ;

busbars with horizontal arrangement:

most remote M , average (-) and the nearest (+) , if you look at the tires from the service corridor;

branches from busbars: left busbar M , average (-) , right (+) , if you look at the tires from the service corridor.

In some cases, deviations from the requirements given in paragraphs 1-3 are allowed if their implementation is associated with a significant complication of electrical installations (for example, it necessitates the installation of special supports near the substation for the transposition of overhead power line wires - overhead lines) or if the substation uses two or more than a stage of transformation.

1.1.32

Electrical installations, according to electrical safety conditions, are divided into electrical installations with voltage up to 1 kV and electrical installations with voltage above 1 kV (according to the effective voltage value).

The safety of operating personnel and unauthorized persons must be ensured by implementing the protective measures provided for in Chapter 1.7, as well as the following measures:

maintaining appropriate distances to live parts or by closing or fencing live parts;

use of device locking and fencing devices to prevent erroneous operations and access to live parts;

use of warning alarms, signs and posters;

the use of devices to reduce the strength of electric and magnetic fields to acceptable values;

the use of protective equipment and devices, including for protection from the effects of electric and magnetic fields in electrical installations in which their intensity exceeds permissible standards.

1.1.33

In electrical premises with installations with voltages up to 1 kV, the use of non-insulated and insulated live parts without contact protection is allowed, if, according to local conditions, such protection is not necessary for any other purposes (for example, for protection from mechanical influences). In this case, parts accessible to touch must be located so that normal maintenance does not involve the danger of touching them.

1.1.34

In residential, public and other premises, devices for fencing and closing live parts must be solid; in areas accessible only to qualified personnel, these devices can be solid, mesh or perforated.

Fencing and closing devices must be made in such a way that they can only be removed or opened using keys or tools.

1.1.35

All enclosing and closing devices must have the required (depending on local conditions) mechanical strength. At voltages above 1 kV, the thickness of metal enclosing and closing devices must be at least 1 mm.

1.1.36

To protect service personnel from electric shock, electric arc, etc. all electrical installations must be equipped with protective equipment, as well as first aid equipment in accordance with the current rules for the use and testing of protective equipment used in electrical installations.

1.1.37

Fire and explosion safety of electrical installations must be ensured by meeting the requirements given in the relevant chapters of these Rules.

Upon commissioning, electrical installations must be equipped with fire-fighting equipment and equipment in accordance with current regulations.

1.1.38

Newly constructed and reconstructed electrical installations and electrical equipment installed in them must be subjected to acceptance tests.

1.1.39

Newly constructed and reconstructed electrical installations are put into commercial operation only after they have been accepted in accordance with the current regulations.

Comprehensive information on this issue:

QUESTION: The network organization, in agreement with the energy sales service of one of the districts of the Primorsky Territory, refused to register the electric energy meter TsE 6803VM 220V1-7.5A 3f 4pr. M R31 date of issue 06/02/2013, established 07/16/2014 requiring re-verification, referring to Chapter 1.5 of the PUE clause 1.5.13.

7th edition.

According to the form, clause 2.2, clause 2.3, the meter meets the requirements of GOST R 52320-2005, GOST R 52322-2005 and the inspection interval is 16 years. Our explanation that the requirement of the PUE according to clause 1.1.1 is advisory in nature, and the form required for them turned out to be unconvincing.

Please clarify the legality of the network organization’s demands for re-verification and the refusal to register the electric energy meter.

Design and installation company

ANSWER:

Federal Service for Environmental, Technological and Nuclear Supervision

The Office of State Energy Supervision of the Federal Service for Environmental, Technological and Nuclear Supervision has considered your appeal and informs you.

In accordance with clause 1.5.13 of the Rules for the Construction of Electrical Installations, Sixth Edition (hereinafter - PUE), newly installed three-phase meters must have state verification seals not older than 12 months, and on single-phase meters - not older than 2 years.

In accordance with Part 5 of Art. 13 of the Law, the procedure for conducting verification of measuring instruments, requirements for the verification mark and the content of the verification certificate are established by the federal executive body exercising the functions of developing state policy and legal regulation in the field of ensuring the uniformity of measurements.

If there are discrepancies in the content of the requirements of the PUE and the Federal Law, then it is necessary to be guided by the requirements of the Federal Law.

At the same time, we inform you that in accordance with Part 3 of Art. 8 of the Federal Law of May 2, 2006 No. 59-FZ “On the procedure for considering appeals from citizens of the Russian Federation” Your letter has been sent to the Federal Agency for Technical Regulation and Metrology, whose competence includes the issue specified in the appeal.

Federal Agency for Technical Regulation and Metrology:

The Federal Agency for Technical Regulation and Metrology (hereinafter referred to as Gosstandart), as appropriate, has considered your request dated August 13, 2014 No. 96 and reports the following.

When determining the procedure for verifying electricity meters, it is necessary to use the verification methodology for this type of device, which regulates the interval between verifications, and Rules PR 50.2.006-94 “GSP. The procedure for verification of measuring instruments”, which were approved by Decree of the State Standard of Russia dated July 18, 1994 No. 125 and registered by order of the Ministry of Justice of Russia dated July 21, 1994 under No. 640, changes No. 1 to these Rules were made by order of the State Standard of Russia dated November 26, 2001. No. 476 (registered with the Ministry of Justice of Russia on January 15, 2002, No. 3157).

According to Part 5 of Article 13 of the Federal Law of the Russian Federation of June 26, 2008 No. 102-FZ “On Ensuring the Uniformity of Measurements”: “The procedure for verification of measuring instruments, requirements for the verification mark and the content of the verification certificate are established by the federal executive body exercising the functions of development of state policy and legal regulation in the field of ensuring uniformity of measurements.”

The listed functions are assigned to Gosstandart (formerly Gosstandart). Consequently, the main legal document in determining the procedure for verification of all measuring instruments is Rules PR 50.2.006-94.

It should be noted that Rules PR 50.2.006-94 provide for extraordinary verification. In accordance with clause 2.14. “An extraordinary verification of measuring instruments in operation is carried out when:

Damage to the verification mark, seals bearing verification marks or in case of loss of the verification certificate;

Commissioning of measuring instruments after long-term storage (more than one verification interval);

Re-adjustment or tuning, known or suspected shock to the measuring instrument, or unsatisfactory operation of the instrument.”

As for the Rules for the Construction of Electrical Installations (PUE), they were approved by order of the Ministry of Energy of the Russian Federation dated July 8, 2002 No. 204. In clause 1.5.13. The specified Rules establish requirements according to which: “Each installed settlement meter must have seals with the state verifier’s mark on the screws securing the meter casing, and on the clamping cover - a seal from the energy supplying organization.

Newly installed three-phase meters must have state verification seals that are no more than 12 months old, and single-phase meters must have state verification seals that are no more than 2 years old.”

However, there is no information about the registration of these Rules with the Russian Ministry of Justice. Consequently, the Electrical Installation Rules are a departmental document.

Also, you should pay attention to the fact that Part 3 of Article 12 of Federal Law No. 102-FZ “On Ensuring the Uniformity of Measurements” contains a provision on the basis of which: “During the validity period of the certificate of approval of the type of measuring instruments, the interval between verifications of measuring instruments can only be changed by the federal executive body performing the functions of providing public services and managing state property in the field of ensuring the uniformity of measurements.”

Based on the foregoing, we can conclude that the requirements established in clause 1.5.13 of the PUE are not mandatory for use by organizations not subordinate to the Ministry of Energy of Russia, and also contradict the current rules on metrology PR 50.2.006-94 and part 3 of article 12 the mentioned Federal Law “On Ensuring the Uniformity of Measurements”.

RULES FOR ELECTRICAL INSTALLATIONS

Seventh edition

Section 1

GENERAL RULES

Chapter 1.7

GROUNDING AND ELECTRICAL SAFETY MEASURES

Chapter 1.7 of the Sixth Edition of the Electrical Installation Rules becomes invalid as of January 1, 2003.

"Rules for the construction of electrical installations" (PUE) of the 7th edition, due to the long period of processing, were issued and put into effect in separate sections and chapters as work on their revision, coordination and approval was completed.

The PUE requirements are mandatory for all organizations, regardless of ownership and organizational and legal forms, as well as for individuals engaged in entrepreneurial activities without forming a legal entity.

Application area. Terms and Definitions

Application area. Terms and Definitions

1.7.1. This chapter of the Rules applies to all electrical installations of alternating and direct current with voltages up to 1 kV and above and contains general requirements for their grounding and protection of people and animals from electric shock both in normal operation of the electrical installation and in the event of insulation damage.

Additional requirements are given in the relevant chapters of the PUE.

1.7.2. Electrical installations with regard to electrical safety measures are divided into:

electrical installations with voltages above 1 kV in networks with a solidly grounded or effectively grounded neutral (see 1.2.16);

electrical installations with voltages above 1 kV in networks with an isolated or grounded neutral through an arc suppression reactor or resistor;

electrical installations with voltage up to 1 kV in networks with a solidly grounded neutral;

electrical installations with voltage up to 1 kV in networks with an insulated neutral.

1.7.3. For electrical installations with voltage up to 1 kV, the following designations are accepted:

system - a system in which the neutral of the power source is solidly grounded, and the open conductive parts of the electrical installation are connected to the solidly grounded neutral of the source through neutral protective conductors;

system - a system in which the neutral protective and neutral working conductors are combined in one conductor along its entire length (Fig. 1.7.1);

Fig.1.7.1. TN-C AC and DC system. Zero protective and zero working conductors are combined in one conductor

Fig.1.7.1. AC () and direct () current system. The neutral protective and neutral working conductors are combined in one conductor: 1 - grounding electrode of the neutral (midpoint) of the power source; 2 - exposed conductive parts; 3 - DC power supply

system - a system in which the neutral protective and neutral working conductors are separated along its entire length (Fig. 1.7.2);

Fig.1.7.2. TN-S AC and DC system. Zero protective and zero working conductors are separated

Fig.1.7.2. AC () and direct () current system. The neutral protective and neutral working conductors are separated:

1 - neutral grounding switch of the alternating current source; 1-1 - grounding switch for the DC source output; 1-2 - ground electrode of the middle point of the DC source; 2 - exposed conductive parts; 3 - power supply

system - a system in which the functions of the neutral protective and neutral working conductors are combined in one conductor in some part of it, starting from the power source (Fig. 1.7.3);

Fig.1.7.3. System TN-C-S AC and DC. Zero protective and zero working conductors are combined in one

Fig.1.7.3. AC () and direct () current system.

The neutral protective and neutral working conductors are combined in one conductor in part of the system: 1 - neutral grounding switch of the alternating current source; 1-1 - grounding switch for the DC source output; 1-2 - ground electrode of the middle point of the DC source; 2 - exposed conductive parts; 3 - power supply

system - a system in which the neutral of the power source is isolated from the ground or grounded through instruments or devices with high resistance, and the open conductive parts of the electrical installation are grounded (Fig. 1.7.4);

Fig.1.7.4. AC and DC IT system. Exposed conductive parts of the electrical installation are grounded. The neutral of the power supply is isolated from ground or grounded through a high resistance

Fig.1.7.4. AC () and direct () current system.
Exposed conductive parts of the electrical installation are grounded. The neutral of the power supply is isolated from ground or grounded through a large resistance: 1 - grounding resistance of the neutral of the power source (if available); 2 - grounding conductor; 3 - exposed conductive parts; 4 - grounding device of the electrical installation; 5 - power supply

system - a system in which the neutral of the power source is solidly grounded, and the open conductive parts of the electrical installation are grounded using a grounding device that is electrically independent of the solidly grounded neutral of the source (Fig. 1.7.5).

Fig.1.7.5. AC and DC TT system. Exposed conductive parts of the electrical installation are grounded using a ground that is electrically independent of the neutral ground electrode.

Fig.1.7.5. AC () and direct () current system. The exposed conductive parts of the electrical installation are grounded using a ground that is electrically independent of the neutral ground electrode:
1 - neutral grounding switch of the alternating current source; 1-1 - grounding switch for the DC source output; 1-2 - ground electrode of the middle point of the DC source; 2 - exposed conductive parts; 3 - grounding conductor of open conductive parts of the electrical installation; 4 - power supply

The first letter is the state of the neutral of the power source relative to ground:

- grounded neutral;

- isolated neutral.

The second letter is the state of exposed conductive parts relative to ground:

- exposed conductive parts are grounded, regardless of the relation to the ground of the neutral of the power source or any point of the supply network;

- open conductive parts are connected to the solidly grounded neutral of the power source.

Subsequent (after) letters - combination in one conductor or separation of the functions of the zero working and zero protective conductors:

- zero working () and zero protective () conductors are separated;

- the functions of the neutral protective and neutral working conductors are combined in one conductor (-conductor);

- - zero working (neutral) conductor;

- - protective conductor (grounding conductor, neutral protective conductor, protective conductor of the potential equalization system);

-- combined zero protective and zero working conductors.

1.7.4. An electrical network with an effectively grounded neutral is a three-phase electrical network with a voltage above 1 kV, in which the earth fault coefficient does not exceed 1.4.

The earth fault coefficient in a three-phase electrical network is the ratio of the potential difference between the undamaged phase and the earth at the point of earth fault of the other or two other phases to the potential difference between the phase and the earth at this point before the fault.

1.7.5. Solidly grounded neutral - the neutral of a transformer or generator connected directly to the grounding device. The output of a single-phase alternating current source or the pole of a direct current source in two-wire networks, as well as the midpoint in three-wire DC networks, can also be solidly grounded.

1.7.6. Isolated neutral - the neutral of a transformer or generator, not connected to a grounding device or connected to it through a high resistance of signaling, measuring, protection and other similar devices.

1.7.7. Conductive part - the part that can conduct electric current.

1.7.8. Current-carrying part is a conductive part of an electrical installation that is under operating voltage during its operation, including the neutral working conductor (but not the -conductor).

1.7.9. An exposed conductive part is a conductive part of an electrical installation that is accessible to touch, not normally energized, but which may become energized if the main insulation is damaged.

1.7.10. Third-party conductive part - a conductive part that is not part of the electrical installation.

1.7.11. Direct touch - electrical contact of people or animals with live parts that are energized.

1.7.12. Indirect touch - electrical contact of people or animals with exposed conductive parts that become energized when the insulation is damaged.

1.7.13. Protection against direct contact - protection to prevent contact with live parts.

1.7.14. Protection against indirect contact - protection against electric shock when touching exposed conductive parts that become live when the insulation is damaged.

The term insulation failure should be understood as a single insulation failure.

1.7.15. Ground electrode - a conductive part or a set of interconnected conductive parts that are in electrical contact with the ground directly or through an intermediate conductive medium.

1.7.16. An artificial grounding conductor is a grounding conductor specially made for grounding purposes.

1.7.17. Natural grounding - a third-party conductive part that is in electrical contact with the ground directly or through an intermediate conducting medium, used for grounding purposes.

1.7.18. Grounding conductor - a conductor connecting the grounded part (point) to the ground electrode.

1.7.19. Grounding device - a combination of ground electrode and grounding conductors.

1.7.20. Zero potential zone (relative ground) is a part of the earth located outside the zone of influence of any ground electrode, the electrical potential of which is assumed to be zero.

1.7.21. Spreading zone (local ground) - the ground zone between the ground electrode and the zero potential zone.

The term ground used in the chapter should be understood as the ground in the spreading zone.

1.7.22. Ground fault - accidental electrical contact between live parts and the ground.

1.7.23. The voltage on the grounding device is the voltage that occurs when current flows from the ground electrode into the ground between the point of current input into the ground electrode and the zero potential zone.

1.7.24. Touch voltage is the voltage between two conductive parts or between a conductive part and the ground when simultaneously touched by a person or animal.

Expected touch voltage is the voltage between simultaneously accessible conductive parts when a person or animal does not touch them.

1.7.25. Step voltage is the voltage between two points on the surface of the earth, at a distance of 1 m from one another, which is taken to be equal to the length of a person’s step.

1.7.26. The resistance of the grounding device is the ratio of the voltage on the grounding device to the current flowing from the grounding device into the ground.

1.7.27. Equivalent resistivity of earth with a heterogeneous structure is the specific electrical resistance of earth with a homogeneous structure, in which the resistance of the grounding device has the same value as in earth with a heterogeneous structure.

The term resistivity, used in the chapter for earth with a heterogeneous structure, should be understood as equivalent resistivity.

1.7.28. Grounding is an intentional electrical connection of any point in the network, electrical installation or equipment with a grounding device.

1.7.29. Protective grounding is grounding performed for electrical safety purposes.

1.7.30. Working (functional) grounding - grounding of a point or points of live parts of an electrical installation, performed to ensure the operation of the electrical installation (not for electrical safety purposes).

1.7.31. Protective grounding in electrical installations with voltages up to 1 kV is a deliberate connection of open conductive parts with a solidly grounded neutral of a generator or transformer in three-phase current networks, with a solidly grounded output of a single-phase current source, with a grounded source point in direct current networks, performed for electrical safety purposes.

1.7.32. Potential equalization is the electrical connection of conductive parts to achieve equality of their potentials.

Protective potential equalization is potential equalization performed for electrical safety purposes.

The term potential equalization used in the chapter should be understood as protective potential equalization.

1.7.33. Potential equalization - reducing the potential difference (step voltage) on the surface of the earth or floor with the help of protective conductors laid in the ground, in the floor or on their surface and connected to a grounding device, or by using special earth coatings.

1.7.34. Protective () conductor - a conductor intended for electrical safety purposes.

Protective grounding conductor - a protective conductor designed for protective grounding.

Protective potential equalization conductor - a protective conductor designed for protective potential equalization.

Neutral protective conductor is a protective conductor in electrical installations up to 1 kV, intended for connecting open conductive parts to the solidly grounded neutral of the power source.

1.7.35. Zero working (neutral) conductor () - a conductor in electrical installations up to 1 kV, intended for powering electrical receivers and connected to a solidly grounded neutral of a generator or transformer in three-phase current networks, with a solidly grounded output of a single-phase current source, with a solidly grounded source point in DC networks.

1.7.36. Combined neutral protective and zero working () conductors - conductors in electrical installations with voltage up to 1 kV, combining the functions of zero protective and zero working conductors.

1.7.37. The main grounding bus is a bus that is part of the grounding device of an electrical installation up to 1 kV and is intended for connecting several conductors for the purpose of grounding and potential equalization.

1.7.38. Protective automatic power off - automatic opening of the circuit of one or more phase conductors (and, if required, the neutral working conductor), performed for electrical safety purposes.

The term automatic power off used in this chapter should be understood as protective automatic power off.

1.7.39. Basic insulation is the insulation of live parts, including protection from direct contact.

1.7.40. Additional insulation is independent insulation in electrical installations with voltages up to 1 kV, performed in addition to the main insulation for protection against indirect contact.

1.7.41. Double insulation - insulation in electrical installations with voltage up to 1 kV, consisting of basic and additional insulation.

1.7.42. Reinforced insulation - insulation in electrical installations with voltages up to 1 kV, providing a degree of protection against electric shock equivalent to double insulation.

1.7.43. Ultra-low (low) voltage (ELV) - voltage not exceeding 50 V AC and 120 V DC.

1.7.44. Isolation transformer - a transformer whose primary winding is separated from the secondary windings by means of protective electrical separation of circuits.

1.7.45. Safety isolation transformer is an isolation transformer designed to supply circuits with ultra-low voltage.

1.7.46. Protective screen is a conductive screen designed to separate an electrical circuit and/or conductors from live parts of other circuits.

1.7.47. Protective electrical separation of circuits - separation of one electrical circuit from other circuits in electrical installations with voltage up to 1 kV using:

double insulation;

main insulation and protective screen;

reinforced insulation.

1.7.48. Non-conducting (insulating) rooms, zones, sites - rooms, zones, sites in which (in which) protection from indirect contact is provided by high resistance of the floor and walls and in which there are no grounded conductive parts.

General requirements

1.7.49. Live parts of the electrical installation should not be accessible to accidental touch, and open and third-party conductive parts accessible to touch should not be under voltage that poses a risk of electric shock both during normal operation of the electrical installation and in the event of insulation damage.

1.7.50. To protect against electric shock in normal operation, the following protective measures against direct contact must be applied, individually or in combination:

basic insulation of live parts;

fencing and shells;

installation of barriers;

placement out of reach;

use of ultra-low (low) voltage.

For additional protection from direct contact in electrical installations with voltages up to 1 kV, subject to the requirements of other chapters of the Electrical Installation Code, residual current devices (RCDs) with a rated residual current of no more than 30 mA should be used.

1.7.51. To protect against electric shock in the event of insulation failure, the following protective measures for indirect contact must be applied individually or in combination:

protective grounding;

automatic power off;

equalization of potentials;

potential equalization;

double or reinforced insulation;

ultra-low (low) voltage;

protective electrical separation of circuits;

insulating (non-conductive) rooms, zones, areas.

1.7.52. Measures to protect against electric shock must be provided in the electrical installation or part thereof, or applied to individual electrical receivers and can be implemented during the manufacture of electrical equipment, or during the installation of the electrical installation, or in both cases.

The use of two or more protective measures in an electrical installation should not have a mutual influence that reduces the effectiveness of each of them.

1.7.53. Protection against indirect contact should be carried out in all cases if the voltage in the electrical installation exceeds 50 V AC and 120 V DC.

In areas with increased danger, particularly dangerous and in outdoor installations, protection against indirect contact may be required at lower voltages, for example, 25 V AC and 60 V DC or 12 V AC and 30 V DC, subject to the requirements of the relevant chapters of the Electrical Code.

Protection against direct contact is not required if the electrical equipment is located in the area of ​​the potential equalization system and the highest operating voltage does not exceed 25 V AC or 60 V DC in non-hazardous areas and 6 V AC or 15 V DC in all cases.

Note. Here and throughout the chapter, AC voltage means the rms value of the AC voltage; DC voltage - direct or rectified current voltage with a ripple content of no more than 10% of the rms value.

1.7.54. For grounding electrical installations, artificial and natural grounding conductors can be used. If, when using natural grounding conductors, the resistance of the grounding devices or the touch voltage has an acceptable value, and the normalized voltage values ​​on the grounding device and the permissible current densities in natural grounding conductors are ensured, the implementation of artificial grounding conductors in electrical installations up to 1 kV is not necessary. The use of natural grounding conductors as elements of grounding devices should not lead to their damage when short-circuit currents flow through them or to disruption of the operation of the devices with which they are connected.

1.7.55. For grounding in electrical installations of different purposes and voltages that are geographically close, one should, as a rule, use one common grounding device.

A grounding device used for grounding electrical installations of the same or different purposes and voltages must meet all the requirements for the grounding of these electrical installations: protecting people from electric shock when the insulation is damaged, operating conditions of networks, protecting electrical equipment from overvoltage, etc. during the entire period of operation.

First of all, the requirements for protective grounding must be met.

Grounding devices for protective grounding of electrical installations of buildings and structures and lightning protection of categories 2 and 3 of these buildings and structures, as a rule, should be common.

When installing a separate (independent) grounding system for working grounding under the operating conditions of information or other equipment sensitive to interference, special measures must be taken to protect against electric shock, preventing simultaneous contact with parts that may be exposed to a dangerous potential difference if the insulation is damaged.

To combine grounding devices of different electrical installations into one common grounding device, natural and artificial grounding conductors can be used. Their number must be at least two.

1.7.56. The required values ​​of touch voltage and resistance of grounding devices when ground fault currents and leakage currents flow from them must be ensured under the most unfavorable conditions at any time of the year.

When determining the resistance of grounding devices, artificial and natural grounding conductors must be taken into account.

When determining the resistivity of the earth, its seasonal value corresponding to the most unfavorable conditions should be taken as the calculated one.

Grounding devices must be mechanically strong, thermally and dynamically resistant to ground fault currents.

1.7.57. Electrical installations with voltages up to 1 kV in residential, public and industrial buildings and outdoor installations should, as a rule, receive power from a source with a solidly grounded neutral using the system.

To protect against electric shock due to indirect contact in such electrical installations, automatic power shutdown must be performed in accordance with 1.7.78-1.7.79.

Requirements for the selection of systems for specific electrical installations are given in the relevant chapters of the Rules.

1.7.58. Power supply of electrical installations with voltage up to 1 kV AC from a source with an isolated neutral using the system should be carried out, as a rule, if the power supply is not interrupted during the first fault to ground or to open conductive parts associated with the potential equalization system. In such electrical installations, to protect against indirect contact during the first ground fault, protective grounding must be performed in combination with network insulation monitoring or an RCD with a rated residual current of no more than 30 mA must be used. In case of a double ground fault, automatic power supply must be switched off in accordance with 1.7.81.

1.7.59. Power supply of electrical installations with voltage up to 1 kV from a source with a solidly grounded neutral and with grounding of exposed conductive parts using a ground electrode not connected to the neutral (system) is allowed only in cases where electrical safety conditions in the system cannot be ensured. To protect against indirect contact in such electrical installations, the power must be automatically turned off with the mandatory use of an RCD. In this case, the following condition must be met:

Where is the tripping current of the protective device;

- the total resistance of the grounding conductor and the grounding conductor, when using an RCD to protect several electrical receivers - the grounding conductor of the most distant electrical receiver.

1.7.60. When using protective automatic power off, a basic potential equalization system must be installed in accordance with 1.7.82, and, if necessary, an additional potential equalization system in accordance with 1.7.83.

1.7.61. When using the system, it is recommended to re-ground the - and - conductors at the entrance to the electrical installations of buildings, as well as in other accessible places. For re-grounding, natural grounding should be used first. The resistance of the re-grounding electrode is not standardized.

Inside large and multi-storey buildings, a similar function is performed by potential equalization by connecting the neutral protective conductor to the main ground bus.

Re-grounding of electrical installations with voltages up to 1 kV, receiving power via overhead lines, must be carried out in accordance with 1.7.102-1.7.103.

1.7.62. If the time of automatic power off does not satisfy the conditions 1.7.78-1.7.79 for the system and 1.7.81 for the system, then protection against indirect contact for individual parts of the electrical installation or individual electrical receivers can be performed using double or reinforced insulation (class II electrical equipment), ultra-low voltage (electrical equipment of class III), electrical separation of circuits of insulating (non-conducting) rooms, zones, sites.

1.7.63. A system with a voltage of up to 1 kV, connected through a transformer to a network with a voltage above 1 kV, must be protected by a breakdown fuse from the danger arising from damage to the insulation between the high and low voltage windings of the transformer. A blow-down fuse must be installed in the neutral or phase on the low voltage side of each transformer.

1.7.64. In electrical installations with voltages above 1 kV with an insulated neutral, protective grounding of exposed conductive parts must be performed to protect against electric shock.

Such electrical installations must be capable of quickly detecting earth faults. Ground fault protection must be installed with a tripping effect throughout the electrically connected network in cases where this is necessary for safety reasons (for lines supplying mobile substations and machinery, peat mining, etc.).

1.7.65. In electrical installations with voltages above 1 kV with an effectively grounded neutral, protective grounding of exposed conductive parts must be performed to protect against electric shock.

1.7.66. Protective grounding in the system and protective grounding in the system of electrical equipment installed on overhead line supports (power and instrument transformers, disconnectors, fuses, capacitors and other devices) must be carried out in compliance with the requirements given in the relevant chapters of the PUE, as well as in this chapter.

The resistance of the grounding device of the overhead line support on which the electrical equipment is installed must comply with the requirements of Chapters 2.4 and 2.5.

Precautions against direct contact

1.7.67. Basic insulation of live parts must cover the live parts and withstand all possible impacts to which it may be subjected during its operation. Removal of insulation should only be possible by destroying it. Paint and varnish coatings are not insulation that protects against electric shock, except in cases specifically specified in the technical specifications for specific products. When performing insulation during installation, it must be tested in accordance with the requirements of Chapter 1.8.

In cases where basic insulation is provided by an air gap, protection from direct contact with live parts or approaching them at a dangerous distance, including in electrical installations with voltages above 1 kV, must be provided by means of shells, fences, barriers or placement out of reach.

1.7.68. Fences and shells in electrical installations with voltages up to 1 kV must have a degree of protection of at least IP 2X, except in cases where large clearances are necessary for the normal operation of electrical equipment.

Guards and shells must be securely fastened and have sufficient mechanical strength.

Entering the fence or opening the shell should be possible only with the help of a special key or tool, or after removing the voltage from live parts. If these conditions cannot be met, intermediate barriers with a degree of protection of at least IP 2X must be installed, the removal of which must also be possible only with the help of a special key or tool.

1.7.69. Barriers are designed to protect against accidental touching of live parts in electrical installations with voltages up to 1 kV or approaching them at a dangerous distance in electrical installations with voltages above 1 kV, but do not exclude intentional touching and approaching live parts when bypassing the barrier. Removal of barriers does not require the use of a wrench or tool, but they must be secured so that they cannot be removed inadvertently. Barriers must be made of insulating material.

1.7.70. Placement out of reach for protection from direct contact with live parts in electrical installations with voltages up to 1 kV or approaching them at a dangerous distance in electrical installations with voltages above 1 kV can be used if it is impossible to carry out the measures specified in 1.7.68-1.7.69, or their insufficiency. In this case, the distance between conductive parts accessible to simultaneous touch in electrical installations with voltages up to 1 kV must be at least 2.5 m. Within the reach zone there should be no parts that have different potentials and are accessible to simultaneous touch.

In the vertical direction, the reach zone in electrical installations with voltages up to 1 kV should be 2.5 m from the surface on which people are located (Fig. 1.7.6).

The indicated dimensions do not take into account the use of auxiliary equipment (for example, tools, ladders, long objects).

Fig.1.7.6. Reach zone in electrical installations up to 1 kV

Fig.1.7.6. Reach zone in electrical installations up to 1 kV:

A surface on which a person can stand;
- surface base;
- the boundary of the reach zone of live parts by the hand of a person located on the surface;
0.75; 1.25; 2.50 m - distance from the edge of the surface to the boundary of the reach zone

1.7.71. Installation of barriers and placement out of reach is only permitted in areas accessible to qualified personnel.

1.7.72. In electrical rooms of electrical installations with voltages up to 1 kV, protection from direct contact is not required if the following conditions are simultaneously met:

these rooms are clearly marked and can only be accessed with a key;

it is possible to freely exit the premises without a key, even if it is locked from the outside;

The minimum dimensions of service passages correspond to Chapter 4.1.

Measures to protect against direct and indirect contact

1.7.73. Extra-low (low) voltage (ELV) in electrical installations with voltages up to 1 kV can be used to protect against electric shock from direct and/or indirect contact in combination with protective electrical separation of circuits or in combination with automatic power off.

In both cases, a safe isolation transformer should be used as a power source for ELV circuits in accordance with GOST 30030 “Isolation transformers and safe isolation transformers” or another ELV source that provides an equivalent degree of safety.

Current-carrying parts of ELV circuits must be electrically separated from other circuits so as to provide electrical separation equivalent to that between the primary and secondary windings of an isolation transformer.

ELV circuit conductors, as a rule, should be laid separately from higher voltage conductors and protective conductors, either separated from them by a grounded metal shield (sheath), or enclosed in a non-metallic sheath in addition to the main insulation.

Plugs and sockets of plug connectors in ELV circuits should not allow connection to sockets and plugs of other voltages.

Plug sockets must be without protective contact.

For ELV values ​​above 25 V AC or 60 V DC, protection against direct contact must also be provided by guards or enclosures or insulation corresponding to a test voltage of 500 V AC for 1 min.

1.7.74. When using ELV in combination with electrical separation of circuits, exposed conductive parts must not be intentionally connected to the grounding system, protective conductors or exposed conductive parts of other circuits and to third-party conductive parts, unless the connection of third-party conductive parts to electrical equipment is necessary and the voltage on these parts cannot exceed the value of SNN.

ELV in combination with electrical separation of circuits should be used when, with the help of ELV, it is necessary to provide protection against electric shock in case of insulation damage not only in the ELV circuit, but also in case of insulation damage in other circuits, for example, in the circuit feeding the source.

When using ELV in combination with automatic power off, one of the terminals of the ELV source and its housing must be connected to the protective conductor of the circuit feeding the source.

1.7.75. In cases where the electrical installation uses electrical equipment with the highest operating (functional) voltage not exceeding 50 V AC or 120 V DC, such voltage can be used as a measure of protection against direct and indirect contact, if the requirements of 1.7.73 are met. -1.7.74.

Protective measures for indirect contact

1.7.76. The requirements for protection from indirect contact apply to:

1) housings of electrical machines, transformers, devices, lamps, etc.;

2) drives of electrical devices;

3) frames of distribution boards, control panels, panels and cabinets, as well as removable or opening parts, if the latter are equipped with electrical equipment with a voltage higher than 50 V AC or 120 V DC (in cases provided for by the relevant chapters of the PUE - higher than 25 V AC or 60 V VDC);

4) metal structures of switchgears, cable structures, cable couplings, shells and armor of control and power cables, sheaths of wires, sleeves and pipes of electrical wiring, shells and supporting structures of busbars (conductors), trays, boxes, strings, cables and strips on which reinforced cables and wires (except for strings, cables and strips along which cables with a neutralized or grounded metal sheath or armor are laid), as well as other metal structures on which electrical equipment is installed;

5) metal shells and armor of control and power cables and wires for voltages not exceeding those specified in 1.7.53, laid on common metal structures, including in common pipes, boxes, trays, etc., with cables and wires on higher voltages;

6) metal cases of mobile and portable electrical receivers;

7) electrical equipment installed on moving parts of machines, machines and mechanisms.

When automatic power shutdown is used as a protective measure, the specified exposed conductive parts must be connected to the solidly grounded neutral of the power source in the system and grounded in systems and.

1.7.77. It is not necessary to intentionally connect to the source neutral in the system and ground in systems and:

1) housings of electrical equipment and devices installed on metal bases: structures, switchgears, switchboards, cabinets, frames of machines, machines and mechanisms connected to the neutral of the power source or grounded, while ensuring reliable electrical contact of these housings with the bases;

2) structures listed in 1.7.76, while ensuring reliable electrical contact between these structures and the electrical equipment installed on them, connected to the protective conductor;

3) removable or opening parts of the metal frames of switchgear chambers, cabinets, fences, etc., if electrical equipment is not installed on the removable (opening) parts or if the voltage of the installed electrical equipment does not exceed the values ​​​​specified in 1.7.53;

4) reinforcement of insulators of overhead power lines and fasteners attached to it;

5) open conductive parts of electrical equipment with double insulation;

6) metal staples, fasteners, sections of pipes for mechanical protection of cables in places where they pass through walls and ceilings and other similar parts of electrical wiring with an area of ​​up to 100 cm, including broach and branch boxes of hidden electrical wiring.

1.7.78. When performing automatic power off in electrical installations with voltages up to 1 kV, all exposed conductive parts must be connected to a solidly grounded neutral of the power source, if the system is used, and grounded if the system or is used. In this case, the characteristics of the protective devices and the parameters of the protective conductors must be coordinated to ensure the normalized time for disconnecting the damaged circuit by the protective switching device in accordance with the rated phase voltage of the supply network.

In electrical installations in which automatic power off is used as a protective measure, potential equalization must be performed.

To automatically turn off the power, protective switching devices that respond to overcurrents or differential current can be used.

1.7.79. In the system, the automatic power shutdown time should not exceed the values ​​​​specified in Table 1.7.1.

Table 1.7.1

The longest permissible protective shutdown time for the system

Rated phase voltage, V	Shutdown time, s
More than 380

The given shutdown time values ​​are considered sufficient to ensure electrical safety, including in group circuits powering mobile and portable electrical receivers and hand-held power tools of class 1.

In circuits feeding distribution, group, floor and other switchboards and shields, the shutdown time should not exceed 5 s.

Disconnection time values ​​greater than those specified in Table 1.7.1 are allowed, but not more than 5 s in circuits that supply only stationary electrical receivers from distribution boards or panels if one of the following conditions is met:

1) the total resistance of the protective conductor between the main grounding bus and the distribution board or panel does not exceed the value, Ohm:

Where is the total resistance of the phase-zero circuit, Ohm;

- rated phase voltage of the circuit, V;

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electrical installations above 1 kV in networks with an effectively grounded neutral (with large ground fault currents);

electrical installations above 1 kV in networks with an isolated neutral (with low ground fault currents);

electrical installations up to 1 kV with a solidly grounded neutral;

electrical installations up to 1 kV with insulated neutral.

1.7.3. An electrical network with an effectively grounded neutral is a three-phase electrical network above 1 kV, in which the earth fault coefficient does not exceed 1.4.

The earth fault coefficient in a three-phase electrical network is the ratio of the potential difference between the undamaged phase and the earth at the point of earth fault of the other or two other phases to the potential difference between the phase and the earth at this point before the fault.

1.7.4. A solidly grounded neutral is the neutral of a transformer or generator, connected to a grounding device directly or through low resistance (for example, through current transformers).

1.7.5. An isolated neutral is the neutral of a transformer or generator that is not connected to a grounding device or is connected to it through signaling, measuring, protection devices, grounding arc suppression reactors and similar devices that have high resistance.

1.7.6. Grounding of any part of an electrical installation or other installation is the intentional electrical connection of this part to a grounding device.

1.7.7. Protective grounding is the grounding of parts of an electrical installation to ensure electrical safety.

1.7.8. Working grounding is the grounding of any point of live parts of an electrical installation, which is necessary to ensure the operation of the electrical installation.

1.7.9. Grounding in electrical installations with voltages up to 1 kV is the intentional connection of parts of an electrical installation that are not normally energized with a solidly grounded neutral of a generator or transformer in three-phase current networks, with a solidly grounded output of a single-phase current source, with a solidly grounded midpoint of the source in DC networks.

1.7.10. An earth fault is an accidental connection of live parts of an electrical installation with structural parts not insulated from the ground, or directly with the ground. A short-circuit to the frame is an accidental connection of energized parts of an electrical installation with their structural parts that are not normally energized.

1.7.11. A grounding device is a combination of a grounding conductor and grounding conductors.

1.7.12. A grounding electrode is a conductor (electrode) or a set of metallic interconnected conductors (electrodes) that are in contact with the ground.

1.7.13. An artificial ground electrode is a ground electrode designed specifically for grounding purposes.

1.7.14. A natural grounding electrode is the electrically conductive parts of communications, buildings and structures for industrial or other purposes that are in contact with the ground and are used for grounding purposes.

1.7.15. A grounding or grounding main is called a grounding or neutral protective conductor with two or more branches, respectively.

1.7.16. A grounding conductor is a conductor that connects the grounded parts to the ground electrode.

1.7.17. A protective conductor (PE) in electrical installations is a conductor used to protect people and animals from electric shock. In electrical installations up to 1 kV, the protective conductor connected to the solidly grounded neutral of the generator or transformer is called the neutral protective conductor.

1.7.18. The neutral working conductor (N) in electrical installations up to 1 kV is the conductor used to power electrical receivers, connected to a solidly grounded neutral of a generator or transformer in three-phase current networks, to a solidly grounded terminal of a single-phase current source, to a solidly grounded source point in three-wire DC networks.

A combined neutral protective and neutral working conductor (PEN) in electrical installations up to 1 kV is a conductor that combines the functions of a neutral protective and neutral working conductor.

In electrical installations up to 1 kV with a solidly grounded neutral, the neutral working conductor can serve as a neutral protective conductor.

1.7.19. The spreading zone is the area of ​​the earth within which a noticeable potential gradient occurs when current flows from the ground electrode.

1.7.20. The zero potential zone is the area of ​​the ground outside the spreading zone.

1.7.21. The voltage on the grounding device is the voltage that occurs when current flows from the ground electrode into the ground between the point of current input into the grounding device and the zero potential zone.

1.7.22. The voltage relative to ground during a short circuit to the housing is the voltage between this housing and the zero potential zone.

1.7.23. Touch voltage is the voltage between two points of a ground fault current circuit (to the body) when a person simultaneously touches them.

1.7.24. Step voltage is the voltage between two points on the ground, caused by the spreading of a fault current to the ground, when a person's feet simultaneously touch them.

1.7.25. Ground fault current is the current flowing into the ground through the fault.

1.7.26. The resistance of the grounding device is the ratio of the voltage on the grounding device to the current flowing from the grounding device into the ground.

1.7.27. The equivalent resistivity of an earth with a heterogeneous structure is the resistivity of an earth with a homogeneous structure in which the resistance of the grounding device has the same value as in an earth with a heterogeneous structure.

The term “resistivity” used in these Rules for earth with a heterogeneous structure should be understood as “equivalent resistivity”.

1.7.28. Protective shutdown in electrical installations up to 1 kV is the automatic shutdown of all phases (poles) of a network section, providing safe combinations of current and its passage time for humans in the event of a short circuit to the housing or a decrease in the insulation level below a certain value.

1.7.29. Double insulation of an electrical receiver is a combination of working and protective (additional) insulation, in which parts of the electrical receiver that are accessible to touch do not acquire dangerous voltage if only the working or only the protective (additional) insulation is damaged.

1.7.30. Low voltage is a rated voltage of no more than 42 V between phases and in relation to ground, used in electrical installations to ensure electrical safety.

1.7.31. An isolation transformer is a transformer designed to separate the network supplying an electrical receiver from the primary electrical network, as well as from the grounding or grounding network.

GENERAL REQUIREMENTS

1.7.32. To protect people from electric shock when the insulation is damaged, at least one of the following protective measures must be applied: grounding, grounding, protective shutdown, isolation transformer, low voltage, double insulation, potential equalization.

1.7.33. Grounding or grounding of electrical installations should be performed:

1) at a voltage of 380 V and above alternating current and 440 V and above direct current - in all electrical installations (see also 1.7.44 and 1.7.48);

2) at rated voltages above 42 V, but below 380 V AC and above 110 V, but below 440 V DC - only in areas with increased danger, especially dangerous ones and in outdoor installations.

Grounding or grounding of electrical installations is not required at rated voltages up to 42 V AC and up to 110 V DC in all cases, except those specified in 1.7.46, clause 6, and in Chapter. 7.3 and 7.6.

1.7.34. Grounding or grounding of electrical equipment installed on overhead line supports (power and instrument transformers, disconnectors, fuses, capacitors and other devices) must be carried out in compliance with the requirements given in the relevant chapters of the PUE, as well as in this chapter.

The resistance of the grounding device of the overhead line support on which the electrical equipment is installed must meet the requirements:

1) 1.7.57-1.7.59 - in electrical installations above 1 kV network with an isolated neutral;

2) 1.7.62 - in electrical installations up to 1 kV with a solidly grounded neutral;

3) 1.7.65 - in electrical installations up to 1 kV with an insulated neutral;

4) 2.5.76 - in networks 110 kV and above.

In three-phase networks up to 1 kV with a solidly grounded neutral and in single-phase networks with a grounded output of a single-phase current source, electrical equipment installed on an overhead line support must be grounded (see 1.7.63).

1.7.35. To ground electrical installations, natural grounding conductors must first be used. If the resistance of the grounding devices or the touch voltage has acceptable values, and the normalized voltage values ​​on the grounding device are also ensured, then artificial grounding electrodes should be used only if it is necessary to reduce the density of currents flowing through natural grounding electrodes or flowing from them.

1.7.36. For grounding electrical installations for various purposes and different voltages, geographically close to one another, it is recommended to use one common grounding device.

To combine the grounding devices of various electrical installations into one common grounding device, all available natural, especially long, grounding conductors should be used.

A grounding device used for grounding electrical installations of the same or different purposes and voltages must meet all the requirements for grounding these electrical installations: protecting people from electric shock when insulation is damaged, operating conditions of networks, protecting electrical equipment from overvoltage, etc.

1.7.37. The resistance of grounding devices and touch voltage required by this chapter must be ensured under the most unfavorable conditions.

The resistivity of the earth should be determined, taking as the calculated value corresponding to the season of the year when the resistance of the grounding device or the touch voltage takes on the highest values.

1.7.38. Electrical installations up to 1 kV AC can be with a solidly grounded or insulated neutral, DC electrical installations - with a solidly grounded or isolated midpoint, and electrical installations with single-phase current sources - with one solidly grounded or with both isolated terminals.

In four-wire three-phase current networks and three-wire direct current networks, solid grounding of the neutral or midpoint of the current sources is mandatory (see also 1.7.105).

1.7.39. In electrical installations up to 1 kV with a solidly grounded neutral or a solidly grounded output of a single-phase current source, as well as with a solidly grounded midpoint in three-wire DC networks, grounding must be performed. The use of grounding of electrical receiver housings in such electrical installations without grounding them is not allowed.

1.7.40. Electrical installations up to 1 kV AC with an isolated neutral or isolated output of a single-phase current source, as well as DC electrical installations with an isolated midpoint should be used with increased safety requirements (for mobile installations, peat mines, mines). For such electrical installations, grounding in combination with network insulation monitoring or protective disconnection must be carried out as a protective measure.

1.7.41. Electrical installations above 1 kV with an insulated neutral must be grounded.

In such electrical installations, it must be possible to quickly detect ground faults (see 1.6.12). Ground fault protection must be installed with a shutdown action (across the entire electrically connected network) in cases where this is necessary for safety reasons (for lines supplying mobile substations and machinery, peat mining, etc.).

1.7.42. Protective shutdown is recommended to be used as a primary or additional protective measure if safety cannot be ensured by a grounding or grounding device, or if a grounding or grounding device causes difficulties due to implementation conditions or for economic reasons. Protective shutdown must be carried out by devices (apparatuses) that meet special technical conditions regarding reliability of operation.

1.7.43. A three-phase network up to 1 kV with an insulated neutral or a single-phase network up to 1 kV with an insulated output, connected through a transformer to a network above 1 kV, must be protected by a breakdown fuse from the danger arising from damage to the insulation between the high and low voltage windings of the transformer. A blow-down fuse must be installed in the neutral or phase on the low voltage side of each transformer. In this case, monitoring of the integrity of the blow-out fuse must be provided.

1.7.44. In electrical installations up to 1 kV in places where isolation or step-down transformers are used as a protective measure, the secondary voltage of the transformers should be: for isolation transformers - no more than 380 V, for step-down transformers - no more than 42 V.

When using these transformers, the following must be followed:

1) isolation transformers must meet special technical conditions regarding increased design reliability and increased test voltages;

2) the isolation transformer is allowed to power only one electrical receiver with a rated current of a fuse link or circuit breaker release on the primary side of no more than 15 A;

3) grounding of the secondary winding of the isolation transformer is not allowed. The transformer housing, depending on the neutral mode of the network supplying the primary winding, must be grounded or neutralized. Grounding of the housing of the electrical receiver connected to such a transformer is not required;

4) step-down transformers with a secondary voltage of 42 V and below can be used as isolation transformers if they meet the requirements given in paragraphs 1 and 2 of this paragraph. If the step-down transformers are not isolating, then, depending on the neutral mode of the network supplying the primary winding, the transformer body, as well as one of the terminals (one of the phases) or the neutral (midpoint) of the secondary winding, should be grounded or grounded.

1.7.45. If it is impossible to carry out grounding, grounding and protective shutdown that meet the requirements of this chapter, or if this poses significant difficulties for technological reasons, servicing electrical equipment from insulating platforms is allowed.

Insulating pads must be made in such a way that touching dangerous ungrounded (non-grounded) parts can only be done from the pads. In this case, the possibility of simultaneous contact with electrical equipment and parts of other equipment and parts of the building must be excluded.

PARTS TO BE GROUNDED OR GROUNDED 1.7.46. Parts subject to grounding or grounding in accordance with 1.7.33 include:

1) housings of electrical machines, transformers, apparatus, lamps, etc. (see also 1.7.44);

2) drives of electrical devices;

3) secondary windings of instrument transformers (see also 3.4.23 and 3.4.24);

4) frames of distribution boards, control panels, panels and cabinets, as well as removable or opening parts, if the latter are equipped with electrical equipment with a voltage higher than 42 V AC or more than 110 V DC;

5) metal structures of switchgears, metal cable structures, metal cable couplings, metal shells and armor of control and power cables, metal shells of wires, metal hoses and electrical wiring pipes, casings and support structures of busbars, trays, boxes, strings, cables and steel strips on which cables and wires are secured (except for strings, cables and strips along which cables with a grounded or neutralized metal sheath or armor are laid), as well as other metal structures on which electrical equipment is installed;

6) metal shells and armor of control and power cables and wires with voltages up to 42 V AC and up to 110 V DC, laid on common metal structures, including in common pipes, boxes, trays, etc. Together with cables and wires, the metal sheaths and armor of which are subject to grounding or grounding;

7) metal cases of mobile and portable electrical receivers;

8) electrical equipment located on moving parts of machines, machines and mechanisms.

1.7.47. In order to equalize potentials in those rooms and outdoor installations in which grounding or grounding is used, building and industrial structures, permanently laid pipelines for all purposes, metal casings of technological equipment, crane and railway tracks, etc. must be connected to the grounding network or zeroing. In this case, natural contacts in the joints are sufficient.

1.7.48. It is not necessary to intentionally ground or neutralize:

1) housings of electrical equipment, devices and electrical installation structures installed on grounded (neutralized) metal structures, switchgears, on switchboards, cabinets, shields, frames of machines, machines and mechanisms, provided that reliable electrical contact is ensured with grounded or neutralized bases (exception - see chapter 7.3);

2) structures listed in 1.7.46, clause 5, provided there is reliable electrical contact between these structures and grounded or neutralized electrical equipment installed on them. At the same time, these structures cannot be used for grounding or neutralizing other electrical equipment installed on them;

3) fittings for insulators of all types, guys, brackets and lighting fixtures when installing them on wooden supports of overhead lines or on wooden structures of open substations, unless this is required by the conditions of protection against atmospheric surges.

When laying a cable with a metallic grounded sheath or a bare grounding conductor on a wooden support, the listed parts located on this support must be grounded or neutralized;

4) removable or opening parts of the metal frames of switchgear chambers, cabinets, fences, etc., if electrical equipment is not installed on the removable (opening) parts or if the voltage of the installed electrical equipment does not exceed 42 V AC or 110 V DC (exception - see chapter 7.3);

5) housings of electrical receivers with double insulation;

6) metal staples, fasteners, sections of pipes for mechanical protection of cables in places where they pass through walls and ceilings and other similar parts, including traction and branch boxes up to 100 cm² in size, electrical wiring carried out by cables or insulated wires laid along walls and ceilings and other building elements.

ELECTRICAL INSTALLATIONS WITH VOLTAGES ABOVE 1 kV NETWORKS WITH AN EFFECTIVELY GROUNDED NEUTRAL

1.7.49. Grounding devices of electrical installations above 1 kV network with an effectively grounded neutral should be made in compliance with the requirements either for their resistance (see 1.7.51) or for touch voltage (see 1.7.52), as well as in compliance with the requirements for design (see . 1.7.53 and 1.7.54) and to limit the voltage on the grounding device (see 1.7.50). Requirements 1.7.49 - 1.7.54 do not apply to grounding devices of overhead line supports.

1.7.50. The voltage on the grounding device when the ground fault current flows from it should not exceed 10 kV. Voltages above 10 kV are allowed on grounding devices from which potentials cannot be carried outside the buildings and external fences of the electrical installation. When voltages on the grounding device are more than 5 kV and up to 10 kV, measures must be taken to protect the insulation of outgoing communication and telemechanics cables and to prevent the removal of dangerous potentials outside the electrical installation.

1.7.51. The grounding device, which is carried out in compliance with the requirements for its resistance, must have a resistance of no more than 0.5 Ohms at any time of the year, including the resistance of natural grounding electrodes.

In order to equalize the electrical potential and ensure the connection of electrical equipment to the ground electrode in the territory occupied by the equipment, longitudinal and transverse horizontal ground electrodes should be laid and connected to each other into a grounding grid.

Longitudinal grounding conductors must be laid along the axes of electrical equipment on the service side at a depth of 0.5-0.7 m from the ground surface and at a distance of 0.8-1.0 m from foundations or equipment bases. It is allowed to increase the distances from foundations or equipment bases to 1.5 m with the installation of one grounding conductor for two rows of equipment, if the service sides are facing one another, and the distance between the foundations or bases of two rows does not exceed 3.0 m.

Transverse grounding conductors should be laid in convenient places between equipment at a depth of 0.5-0.7 m from the ground surface. It is recommended to take the distance between them increasing from the periphery to the center of the grounding grid. In this case, the first and subsequent distances, starting from the periphery, should not exceed 4.0, respectively; 5.0; 6.0; 7.5; 9.0; 11.0; 13.5; 16.0 and 20.0 m. The dimensions of the grounding grid cells adjacent to the points where the neutrals of power transformers and short-circuiters are connected to the grounding device should not exceed 6x6 m².

Horizontal grounding conductors should be laid along the edge of the territory occupied by the grounding device, so that together they form a closed loop.

If the contour of the grounding device is located within the external fence of the electrical installation, then at the entrances and entrances to its territory the potential should be equalized by installing two vertical grounding electrodes at the external horizontal grounding electrode opposite the entrances and entrances. Vertical grounding conductors should be 3-5 m long, and the distance between them should be equal to the width of the entrance or entrance.

1.7.52. The grounding device, which is carried out in compliance with the requirements for touch voltage, must provide at any time of the year when a ground fault current flows from it, touch voltage values ​​do not exceed the standardized ones. The resistance of the grounding device is determined by the permissible voltage on the grounding device and the ground fault current.

When determining the value of the permissible touch voltage, the sum of the protection action time and the total time of switching off the circuit breaker should be taken as the estimated exposure time. In this case, the determination of permissible values ​​of touch voltages at workplaces where, during operational switching, short-circuits may occur on structures accessible to touch by the personnel performing the switching, the duration of the backup protection should be taken, and for the rest of the territory - the main protection.

The placement of longitudinal and transverse horizontal grounding conductors should be determined by the requirements for limiting touch voltages to standardized values ​​and the convenience of connecting the grounded equipment. The distance between longitudinal and transverse horizontal artificial grounding conductors should not exceed 30 m, and the depth of their placement in the ground should be at least 0.3 m. At workplaces, it is allowed to lay grounding conductors at a shallower depth if the need for this is confirmed by calculations, and the implementation itself does not reduce ease of maintenance of electrical installations and service life of grounding conductors. To reduce touch stress at workplaces, in justified cases, a layer of crushed stone 0.1-0.2 m thick can be added.

1.7.53. When making a grounding device in compliance with the requirements for its resistance or touch voltage, in addition to the requirements of 1.7.51 and 1.7.52, the following should be done:

grounding conductors connecting equipment or structures to the ground electrode should be laid in the ground at a depth of at least 0.3 m;

near the locations of grounded neutrals of power transformers and short-circuiters, lay longitudinal and transverse horizontal grounding conductors (in four directions).

When the grounding device extends beyond the fence of the electrical installation, horizontal grounding conductors located outside the territory of the electrical installation should be laid at a depth of at least 1 m. The external contour of the grounding device in this case is recommended to be made in the form of a polygon with obtuse or rounded corners.

1.7.54. It is not recommended to connect the external fence of electrical installations to a grounding device. If overhead lines of 110 kV and higher depart from the electrical installation, then the fence should be grounded using vertical grounding electrodes 2-3 m long, installed at the fence posts along its entire perimeter every 20-50 m. Installation of such grounding electrodes is not required for a fence with metal posts and with those posts made of reinforced concrete, the reinforcement of which is electrically connected to the metal links of the fence.

To exclude electrical connection between the external fence and the grounding device, the distance from the fence to the elements of the grounding device located along it on the internal, external or both sides must be at least 2 m. Horizontal grounding conductors, pipes and cables with a metal sheath extending beyond the fence and other metal communications must be laid in the middle between the fence posts at a depth of at least 0.5 m. In places where the external fence adjoins buildings and structures, as well as in places where internal metal fences adjoin the external fence, brick or wooden inserts not longer than less than 1 m.

Electrical receivers up to 1 kV, which are powered directly from step-down transformers located on the territory of the electrical installation, should not be installed on the external fence. When placing electrical receivers on an external fence, they should be powered through isolation transformers. These transformers are not allowed to be installed on a fence. The line connecting the secondary winding of the isolation transformer with the power receiver located on the fence must be insulated from the ground to the calculated voltage value on the grounding device.

If it is impossible to carry out at least one of the indicated measures, then the metal parts of the fence should be connected to a grounding device and potential equalization should be performed so that the touch voltage on the outer and inner sides of the fence does not exceed permissible values. When making a grounding device according to the permissible resistance, for this purpose a horizontal grounding conductor must be laid on the outside of the fence at a distance of 1 m from it and at a depth of 1 m. This ground electrode should be connected to the grounding device at least at four points.

1.7.55. If the grounding device of an industrial or other electrical installation is connected to the ground electrode of an electrical installation above 1 kV with an effectively grounded neutral cable with a metal sheath or armor or through other metal connections, then in order to equalize the potentials around such an electrical installation or around the building in which it is located, it is necessary to comply with one of following conditions:

1) laying in the ground at a depth of 1 m and at a distance of 1 m from the foundation of the building or from the perimeter of the territory occupied by the equipment, a grounding conductor connected to metal structures for construction and industrial purposes and a grounding network (grounding), and at the entrances and entrances to the building - laying conductors at a distance of 1 and 2 m from the ground electrode at a depth of 1 and 1.5 m, respectively, and connecting these conductors to the ground electrode;

2) the use of reinforced concrete foundations as grounding conductors in accordance with 1.7.35 and 1.7.70, if this ensures an acceptable level of potential equalization. Providing conditions for potential equalization using reinforced concrete foundations used as grounding conductors is determined based on the requirements of special directive documents.

The conditions specified in clauses 1 and 2 are not required if there are asphalt blind areas around the buildings, including at entrances and driveways. If there is no blind area at any entrance (entrance), potential equalization must be performed at this entrance (entrance) by laying two conductors, as indicated in clause 1, or the condition in clause 2 must be met. In all cases, the following must be met: requirements 1.7.56.

1.7.56. To avoid potential carryover, power supply to electrical receivers located outside the grounding devices of electrical installations above 1 kV of a network with an effectively grounded neutral, from windings up to 1 kV with a grounded neutral of transformers located within the contour of the grounding device, is not allowed. If necessary, such power receivers can be powered from a transformer with an isolated neutral on the side up to 1 kV via a cable line made with a cable without a metal sheath and without armor, or via an overhead line. Such power receivers can also be powered through an isolation transformer. The isolating transformer and the line from its secondary winding to the power receiver, if it passes through the territory occupied by the grounding device of the electrical installation, must be insulated from the ground to the calculated voltage value on the grounding device. If it is impossible to fulfill the specified conditions in the territory occupied by such electrical receivers, potential equalization must be performed.

ELECTRICAL INSTALLATIONS WITH VOLTAGES ABOVE 1 kV NETWORKS WITH AN ISOLATED NEUTRAL

1.7.57. In electrical installations above 1 kV network with an isolated neutral, the resistance of the grounding device R, Ohm, when the calculated ground fault current passes at any time of the year, taking into account the resistance of natural grounding conductors, there should be no more than:

when using a grounding device simultaneously for electrical installations with voltage up to 1 kV

R=125/I, but not more than 10 Ohms.

Where I- calculated ground fault current, A.

In this case, the requirements for grounding (grounding) electrical installations up to 1 kV must also be met;

when using a grounding device only for electrical installations above 1 kV

R = 250 / I, but not more than 10 Ohms.

1.7.58. The following is accepted as the calculated current:

1) in networks without capacitive current compensation - full ground fault current;

2) in networks with capacitive current compensation;

for grounding devices to which compensating devices are connected - a current equal to 125% of the rated current of these devices;

for grounding devices to which compensating devices are not connected - the residual ground fault current passing in a given network when the most powerful of the compensating devices or the most branched section of the network is disconnected.

The calculated current can be taken as the melting current of fuses or the operating current of relay protection against single-phase ground faults or phase-to-phase faults, if in the latter case the protection ensures shutdown of ground faults. In this case, the ground fault current must be at least one and a half times the operating current of the relay protection or three times the rated current of the fuses.

The calculated ground fault current must be determined for that of the network circuits possible in operation for which this current has the greatest value.

1.7.59. In open electrical installations above 1 kV networks with an isolated neutral, a closed horizontal grounding conductor (circuit) must be laid around the area occupied by the equipment at a depth of at least 0.5 m, to which the grounded equipment is connected. If the resistance of the grounding device is higher than 10 Ohms (in accordance with 1.7.69 for earth with a resistivity of more than 500 Ohm m), then horizontal grounding conductors should be additionally laid along the rows of equipment on the service side at a depth of 0.5 m and at a distance of 0.8 -1.0 m from foundations or equipment bases.

ELECTRICAL INSTALLATIONS WITH VOLTAGE UP TO 1 kV WITH A SOLIDLY GROUNDED NEUTRAL

1.7.60. The neutral of the generator, transformer on the side up to 1 kV must be connected to the grounding electrode using a grounding conductor. The cross-section of the grounding conductor must be no less than that indicated in the table. 1.7.1.

The use of the neutral working conductor coming from the neutral of the generator or transformer to the switchboard as a grounding conductor is not allowed.

The specified ground electrode must be located in close proximity to the generator or transformer. In some cases, for example, in intra-shop substations, the ground electrode may be constructed directly next to the wall of the building.

1.7.61. The output of the neutral working conductor from the neutral of a generator or transformer to the switchboard must be carried out: when outputting phases by buses - a busbar on insulators, when outputting phases by cable (wire) - a residential cable (wire). In cables with an aluminum sheath, it is allowed to use the sheath as the neutral working conductor instead of the fourth core.

The conductivity of the neutral working conductor coming from the neutral of the generator or transformer must be at least 50% of the conductivity of the phase output.

1.7.62. The resistance of the grounding device to which the neutrals of generators or transformers or the terminals of a single-phase current source are connected, at any time of the year should be no more than 2, 4 and 8 Ohms, respectively, at line voltages of 660, 380 and 220 V of a three-phase current source or 380, 220 and 127 In a single-phase current source. This resistance must be ensured taking into account the use of natural grounding conductors, as well as grounding conductors for repeated grounding of the neutral wire of an overhead line up to 1 kV with a number of outgoing lines of at least two. In this case, the resistance of the grounding conductor located in close proximity to the neutral of the generator or transformer or the output of a single-phase current source should be no more than: 15, 30 and 60 Ohms, respectively, at line voltages of 660, 380 and 220 V of a three-phase current source or 380, 220 and 127 In a single-phase current source.

If the specific resistance of the earth is more than 100 Ohm m, it is allowed to increase the above norms by 0.01 times, but not more than tenfold.

1.7.63. On an overhead line, grounding must be done with a neutral working wire laid on the same supports as the phase wires.

At the ends of overhead lines (or branches from them) with a length of more than 200 m, as well as at the inputs from overhead lines to electrical installations that are subject to grounding, the neutral working wire must be re-grounded. In this case, first of all, natural grounding devices should be used, for example, underground parts of supports (see 1.7.70), as well as grounding devices designed for protection against lightning overvoltages (see 2.4.26).

The specified repeated groundings are performed if more frequent groundings are not required under the conditions of protection against lightning surges.

Repeated grounding of the neutral wire in DC networks must be carried out using separate artificial grounding conductors, which should not have metal connections to underground pipelines. Grounding devices on DC overhead lines designed to protect against lightning surges (see 2.4.26) are recommended to be used for re-grounding the neutral working wire.

Grounding conductors for repeated grounding of the neutral wire must be selected from the condition of long-term current flow of at least 25 A. In terms of mechanical strength, these conductors must have dimensions no less than those given in table. 1.7.1.

1.7.64. The total resistance to spreading of grounding conductors (including natural ones) of all repeated groundings of the neutral working wire of each overhead line at any time of the year should be no more than 5, 10 and 20 Ohms, respectively, at line voltages of 660, 380 and 220 V of a three-phase current source or 380, 220 and 127 V single-phase current source. In this case, the spreading resistance of the grounding conductor of each of the repeated groundings should be no more than 15, 30 and 60 Ohms, respectively, at the same voltages.

If the specific resistance of the earth is more than 100 Ohm m, it is allowed to increase the specified standards by 0.01 times, but not more than tenfold.

ELECTRICAL INSTALLATIONS WITH VOLTAGE up to 1 kV WITH AN INSULATED NEUTRAL

1.7.65. The resistance of the grounding device used to ground electrical equipment must be no more than 4 ohms.

When the power of generators and transformers is 100 kVA or less, grounding devices can have a resistance of no more than 10 Ohms. If generators or transformers operate in parallel, then a resistance of 10 Ohms is allowed with their total power not exceeding 100 kVA.

1.7.66. Grounding devices of electrical installations with voltages above 1 kV with an effectively grounded neutral in areas with high earth resistivity, including in permafrost areas, are recommended to comply with the requirements for touch voltage (see 1.7.52).

In rocky structures, it is allowed to lay horizontal grounding conductors at a shallower depth than required by 1.7.52 - 1.7.54, but not less than 0.15 m. In addition, it is allowed not to install the vertical grounding conductors required by 1.7.51 at entrances and entrances.

1.7.67. When constructing artificial grounding systems in areas with high earth resistivity, the following measures are recommended:

1) installation of vertical grounding conductors of increased length, if the resistivity of the earth decreases with depth, and there are no natural deep grounding conductors (for example, wells with metal casing pipes);

2) installation of remote grounding electrodes, if there are places with lower earth resistivity near (up to 2 km) from the electrical installation;

3) laying moist clay soil in trenches around horizontal grounding conductors in rocky structures, followed by compaction and backfilling with crushed stone to the top of the trench;

4) the use of artificial soil treatment in order to reduce its resistivity, if other methods cannot be used or do not give the required effect.

1.7.68. In permafrost areas, in addition to the recommendations given in 1.7.67, you should:

1) place grounding conductors in non-freezing reservoirs and thawed zones;

2) use well casing pipes; 3) in addition to deep grounding conductors, use extended grounding conductors at a depth of about 0.5 m, designed to operate in the summer when the surface layer of the earth thaws;

4) create artificial thawed zones by covering the soil above the ground electrode with a layer of peat or other heat-insulating material for the winter period and opening them for the summer period.

1.7.69. In electrical installations above 1 kV, as well as in electrical installations up to 1 kV with an isolated neutral for the ground with a resistivity of more than 500 Ohm m, if the measures provided for in 1.7.66-1.7.68 do not allow obtaining grounding conductors acceptable for economic reasons, it is allowed to increase The resistance values ​​of grounding devices required by this chapter are 0.002 times, where is the equivalent earth resistivity, Ohm m. In this case, the increase in the resistance of grounding devices required by this chapter should be no more than tenfold.

EARTHING LEADERS

1.7.70. It is recommended to use the following as natural grounding conductors: 1) water supply and other metal pipelines laid in the ground, with the exception of pipelines of flammable liquids, flammable or explosive gases and mixtures;

2) well casings;

3) metal and reinforced concrete structures of buildings and structures in contact with the ground;

4) metal shunts of hydraulic structures, water conduits, gates, etc.;

5) lead sheaths of cables laid in the ground. Aluminum cable sheaths are not allowed to be used as natural grounding conductors.

If cable sheaths serve as the only grounding conductors, then in the calculation of grounding devices they must be taken into account when there are at least two cables;

6) grounding conductors of overhead line supports connected to the grounding device of the electrical installation using an overhead line lightning protection cable, if the cable is not isolated from the overhead line supports;

7) neutral wires of overhead lines up to 1 kV with repeated grounding switches for at least two overhead lines;

8) rail tracks of main non-electrified railways and access roads if there is a deliberate arrangement of jumpers between the rails.

1.7.71. Grounding electrodes must be connected to the grounding mains by at least two conductors connected to the grounding electrode in different places. This requirement does not apply to overhead line supports, re-grounding of the neutral wire and metal cable sheaths.

1.7.72. For artificial grounding conductors, steel should be used.

Artificial grounding conductors should not be painted.

The smallest dimensions of steel artificial grounding conductors are given below:

The cross-section of horizontal grounding conductors for electrical installations with voltages above 1 kV is selected according to thermal resistance (based on the permissible heating temperature of 400 °C).

Grounding electrodes should not be located (used) in places where the ground is dried out by the heat of pipelines, etc.

Trenches for horizontal grounding conductors must be filled with homogeneous soil that does not contain crushed stone and construction waste.

If there is a risk of corrosion of grounding conductors, one of the following measures must be taken:

increasing the cross-section of grounding conductors taking into account their estimated service life;

use of galvanized grounding conductors;

use of electrical protection.

As artificial grounding conductors, it is allowed to use grounding conductors made of electrically conductive concrete.

GROUNDING AND ZERO PROTECTIVE CONDUCTORS

1.7.73. As neutral protective conductors, neutral working conductors should be used first (see also 1.7.82).

The following can be used as grounding and neutral protective conductors (for exceptions, see Chapter 7.3):

1) conductors specially provided for this purpose;

2) metal structures of buildings (trusses, columns, etc.);

3) reinforcement of reinforced concrete building structures and foundations;

4) metal structures for industrial purposes (crane tracks, switchgear frames, galleries, platforms, elevator shafts, elevators, elevators, channel frames, etc.);

5) steel pipes for electrical wiring;

6) aluminum cable sheaths;

7) metal casings and supporting structures of busbars, metal boxes and trays of electrical installations;

8) metal stationary openly laid pipelines for all purposes, except for pipelines of flammable and explosive substances and mixtures, sewerage and central heating.

Given in paragraphs. 2-8 conductors, structures and other elements can serve as the only grounding or neutral protective conductors if their conductivity meets the requirements of this chapter and if continuity of the electrical circuit is ensured throughout use.

Grounding and neutral protective conductors must be protected from corrosion.

1.7.74. The use of metal sheaths of tubular wires, supporting cables for cable wiring, metal sheaths of insulating tubes, metal hoses, as well as armor and lead sheaths of wires and cables as grounding or neutral protective conductors is prohibited. The use of lead cable sheaths for these purposes is permitted only in reconstructed city electrical networks of 220/127 and 380/220 V.

In indoor and outdoor installations that require grounding or grounding, these elements must be grounded or grounded and have reliable connections throughout. Metal couplings and boxes must be connected to armor and to metal shells by soldering or bolting.

1.7.75. Grounding or grounding lines and branches from them in enclosed spaces and in outdoor installations must be accessible for inspection and have cross-sections no less than those given in 1.7.76 - 1.7.79.

The requirement for accessibility for inspection does not apply to neutral conductors and cable sheaths, to reinforcement of reinforced concrete structures, as well as to grounding and neutral protective conductors laid in pipes and boxes, as well as directly in the body of building structures (embedded).

Branches from mains to electrical receivers up to 1 kV can be laid hidden directly in the wall, under a clean floor, etc., protecting them from exposure to aggressive environments. Such branches should not have connections.

In outdoor installations, grounding and neutral protective conductors may be laid in the ground, in the floor or along the edge of platforms, foundations of technological installations, etc.

The use of uninsulated aluminum conductors for laying in the ground as grounding or neutral protective conductors is not allowed.

1.7.76. Grounding and neutral protective conductors in electrical installations up to 1 kV must have dimensions no less than those given in table. 1.7.1 (see also 1.7.96 and 1.7.104).

The cross-sections (diameters) of the neutral protective and neutral working conductors of overhead lines must be selected in accordance with the requirements of Chapter. 2.4.

Table 1.7.1. Smallest dimensions of grounding and neutral protective conductors

Name	Copper	Aluminum	Steel
			in buildings	in outdoor installations	in the ground
Bare conductors:
cross-section, mm²	4	6	-	-	-
diameter, mm	-	-	5	6	10
Insulated wires:
cross-section, mm²	1,5*	2,5	-	-	-
* When laying wires in pipes, the cross-section of neutral protective conductors can be used equal to 1 mm² if the phase conductors have the same cross-section.
Grounding and neutral conductors of cables and stranded wires in a common protective sheath with phase conductors: cross-section, mm²	1	2,5	-	-	-
Angle steel: flange thickness, mm	-	-	2	2,5	4
Strip steel:
cross-section, mm²	-	-	24	48	48
thickness, mm	-	-	3	4	4
Water and gas pipes (steel): wall thickness, mm	-	-	2,5	2,5	3,5
Thin-walled pipes (steel): wall thickness, mm	-	-	1,5	2,5	Not allowed

1.7.77. In electrical installations above 1 kV with an effectively grounded neutral, the cross-sections of the grounding conductors must be selected such that when the highest single-phase short-circuit current flows through them, the temperature of the grounding conductors does not exceed 400°C (short-term heating corresponding to the duration of the main protection and the full time of switching off the circuit breaker).

1.7.78. In electrical installations up to 1 kV and above with an insulated neutral, the conductivity of the grounding conductors must be at least 1/3 of the conductivity of the phase conductors, and the cross-section should be no less than those given in the table. 1.7.1 (see also 1.7.96 and 1.7.104). The use of copper conductors with a cross-section of more than 25 mm², aluminum - 35 mm², steel - 120 mm² is not required. In industrial premises with such electrical lines, grounding from steel strip must have a cross-section of at least 100 mm². It is permissible to use round steel of the same section.

1.7.79. In electrical installations up to 1 kV with a solidly grounded neutral, in order to ensure automatic shutdown of the emergency section, the conductivity of the phase and neutral protective conductors must be selected such that in the event of a short circuit to the housing or to the neutral protective conductor, a short-circuit current will occur that exceeds at least:

3 times the rated current of the fuse element of the nearest fuse;

3 times the rated current of an unregulated release or the current setting of an adjustable release of a circuit breaker having a characteristic inversely dependent on the current.

When protecting networks with automatic circuit breakers that have only an electromagnetic release (cut-off), the conductivity of the specified conductors must ensure a current not lower than the instantaneous current setting, multiplied by a factor taking into account the spread (according to factory data), and by a safety factor of 1.1. In the absence of factory data, for circuit breakers with a rated current of up to 100 A, the short circuit current multiplicity relative to the setting should be taken to be at least 1.4, and for circuit breakers with a rated current of more than 100 A - at least 1.25.

The total conductivity of the neutral protective conductor in all cases must be at least 50% of the conductivity of the phase conductor.

If the requirements of this paragraph are not met with respect to the value of the fault current to the body or to the neutral protective conductor, then disconnection during these short circuits must be ensured using special protections.

1.7.80. In electrical installations up to 1 kV with a solidly grounded neutral, in order to meet the requirements given in 1.7.79, it is recommended to lay neutral protective conductors together or in close proximity to the phase conductors.

1.7.81. Neutral working conductors must be designed for long-term flow of operating current.

It is recommended to use conductors with insulation equivalent to the insulation of phase conductors as neutral working conductors. Such insulation is mandatory for both neutral working and neutral protective conductors in those places where the use of bare conductors can lead to the formation of electrical pairs or damage to the insulation of phase conductors as a result of sparking between the bare neutral conductor and the shell or structure (for example, when laying wires in pipes, boxes, trays). Such insulation is not required if casings and support structures of complete busbar trunkings and busbars of complete distribution devices (boards, distribution points, assemblies, etc.), as well as aluminum or lead cable sheaths are used as neutral working and neutral protective conductors (see. 1.7.74 and 2.3.52).

In industrial premises with a normal environment, it is allowed to use the metal structures, pipes, casings and support structures of busbars specified in 1.7.73 as neutral working conductors to power single-phase low-power electrical receivers, for example: in networks up to 42 V; when switching on single coils of magnetic starters or contactors to phase voltage; when switching on phase voltage of electric lighting and control and alarm circuits on taps.

1.7.82. It is not allowed to use neutral working conductors going to portable single-phase and direct current electrical receivers as neutral protective conductors. To ground such electrical receivers, a separate third conductor must be used, connected in the plug-in connector of the branch box, in the panel, shield, assembly, etc. to the neutral working or neutral protective conductor (see also 6.1.20).

1.7.83. There should be no disconnecting devices or fuses in the circuit of grounding and neutral protective conductors.

In the circuit of neutral working conductors, if they simultaneously serve for grounding purposes, it is allowed to use switches that, simultaneously with disconnecting the neutral working conductors, disconnect all live wires (see also 1.7.84).

Single-pole switches should be installed in the phase conductors, and not in the neutral working conductor.

1.7.84. Neutral protective conductors of lines are not allowed to be used to neutralize electrical equipment powered by other lines.

It is allowed to use neutral working conductors of lighting lines to ground electrical equipment powered by other lines, if all of these lines are powered from one transformer, their conductivity satisfies the requirements of this chapter and the possibility of disconnecting the neutral working conductors during operation of other lines is excluded. In such cases, switches that disconnect neutral working conductors together with phase conductors should not be used.

1.7.85. In dry rooms, without an aggressive environment, grounding and neutral protective conductors can be laid directly along the walls.

In damp, damp and especially damp rooms and in rooms with an aggressive environment, grounding and neutral protective conductors should be laid at a distance from the walls of at least 10 mm.

1.7.86. Grounding and neutral protective conductors must be protected from chemical influences. At the places where these conductors cross with cables, pipelines, railway tracks, at the places where they enter buildings and in other places where mechanical damage to the grounding and neutral protective conductors is possible, these conductors must be protected.

1.7.87. The laying of grounding and neutral protective conductors in places of passage through walls and ceilings should, as a rule, be carried out with their direct termination. In these places, conductors should not have connections or branches.

1.7.88. Identification signs must be provided at the points where grounding conductors enter buildings.

1.7.89. The use of specially laid grounding or neutral protective conductors for other purposes is not permitted.

CONNECTIONS AND CONNECTIONS OF GROUNDING AND ZERO PROTECTIVE CONDUCTORS

1.7.90. Connections of grounding and neutral protective conductors to each other must ensure reliable contact and be performed by welding.

It is allowed to make connections of grounding and neutral protective conductors in indoor and outdoor installations without aggressive environments in other ways that meet the requirements of GOST 10434-82 "Contact electrical connections. General technical requirements" for the 2nd class of connections. In this case, measures must be taken against loosening and corrosion of contact connections. Connections of grounding and neutral protective conductors of electrical wiring and overhead lines can be made using the same methods as phase conductors.

Connections of grounding and neutral protective conductors must be accessible for inspection.

1.7.91. Steel electrical wiring pipes, boxes, trays and other structures used as grounding or neutral protective conductors must have connections that meet the requirements of GOST 10434-82 for class 2 connections. Reliable contact of steel pipes with the housings of electrical equipment into which the pipes are inserted, and with connecting (branch) metal boxes must also be ensured.

1.7.92. Places and methods of connecting grounding conductors with extended natural grounding conductors (for example, pipelines) must be selected such that when disconnecting the grounding conductors for repair work, the calculated value of the resistance of the grounding device is ensured. Water meters, valves, etc. must have bypass conductors to ensure continuity of the grounding circuit.

1.7.93. The connection of grounding and neutral protective conductors to parts of equipment to be grounded or neutralized must be performed by welding or bolting. The connection must be accessible for inspection. For bolted connections, measures must be taken to prevent loosening and corrosion of the contact connection.

Grounding or grounding of equipment that is subject to frequent dismantling or installed on moving parts or parts subject to shock or vibration must be performed with flexible grounding or neutral protective conductors.

1.7.94. Each part of the electrical installation that is subject to grounding or grounding must be connected to the grounding or grounding network using a separate branch. The sequential connection of grounded or neutralized parts of an electrical installation into the grounding or neutral protective conductor is not allowed.

PORTABLE ELECTRICAL CONDITIONS

1.7.95. Portable electrical receivers should be powered from a mains voltage not exceeding 380/220 V.

Depending on the category of the premises in terms of the level of danger of electric shock to people (see Chapter 1.1), portable electrical receivers can be powered either directly from the network, or through isolation or step-down transformers (see 1.7.44).

Metal cases of portable electrical receivers above 42 V AC and above 110 V DC in high-risk areas, especially dangerous ones and in outdoor installations must be grounded or neutralized, with the exception of electrical receivers with double insulation or powered by isolation transformers.

1.7.96. Grounding or grounding of portable electrical receivers must be carried out by a special conductor (the third - for single-phase and direct current electrical receivers, the fourth - for three-phase current electrical receivers), located in the same shell with the phase conductors of the portable wire and connected to the housing of the electrical receiver and to a special contact of the plug of the plug-in connector (see 1.7.97). The cross-section of this core must be equal to the cross-section of the phase conductors. The use of a neutral working conductor for this purpose, including one located in a common shell, is not permitted.

Due to the fact that GOST for some brands of cables provides for a reduced cross-section of the fourth core, the use of such cables for three-phase portable power receivers is permitted until the corresponding change in GOST.

The cores of wires and cables used for grounding or grounding portable electrical receivers must be copper, flexible, with a cross-section of at least 1.5 mm² for portable electrical receivers in industrial installations and at least 0.75 mm² for household portable electrical receivers.

1.7.97. Portable electrical receivers of testing and experimental installations, the movement of which is not intended during their operation, may be grounded using stationary or separate portable grounding conductors. In this case, stationary grounding conductors must meet the requirements of 1.7.73 - 1.7.89, and portable grounding conductors must be flexible, copper, with a cross-section not less than the cross-section of the phase conductors, but not less than that specified in 1.7.96.

In plug-in connectors of portable electrical receivers, extension wires and cables, conductors must be connected to the socket from the power source side, and to the plug - from the electrical receivers side.

Plug-in connectors must have special contacts to which grounding and neutral protective conductors are connected.

When switched on, the connection between these contacts must be established before the contacts of the phase conductors come into contact. The order of disconnecting contacts when disconnecting should be reversed.

The design of plug-in connectors must be such that it is possible to connect the contacts of phase conductors with grounding (grounding) contacts.

If the body of the plug-in connector is made of metal, it must be electrically connected to the grounding (grounding) contact.

1.7.98. The grounding and neutral protective conductors of portable wires and cables must have a distinctive feature.