Section 7
ELECTRICAL EQUIPMENT FOR SPECIAL INSTALLATIONS
Chapter 7.1
ELECTRICAL INSTALLATIONS OF RESIDENTIAL, PUBLIC, ADMINISTRATIVE AND DOMESTIC BUILDINGS
* The requirements of this chapter are interrelated. It should be borne in mind that partial compliance with a set of requirements for electrical installations of buildings can lead to a decrease in the level of electrical safety.
APPLICATION AREA. DEFINITIONS
7.1.1. This chapter of the Rules applies to electrical installations of: residential buildings listed in SNiP 2.08.01-89 “Residential Buildings”; public buildings listed in SNiP 2.08.02-89 "Public buildings and structures" (with the exception of buildings and premises listed in Chapter 7.2); administrative and residential buildings listed in SNiP 2.09.04-87 "Administrative and residential buildings"; Additional requirements may apply to electrical installations of unique and other special buildings not included in the above list.
The requirements of this chapter do not apply to special electrical installations in medical institutions, organizations and institutions of science and scientific services, to dispatch and communication systems, as well as to electrical installations, which by their nature should be classified as electrical installations of industrial enterprises (workshops, boiler rooms, thermal points, pumping stations, laundry factories, dry cleaning factories, etc.).
7.1.2. Electrical installations of buildings, in addition to the requirements of this chapter, must meet the requirements of the chapters of Section. 1-6 PUE to the extent that they are not changed by this chapter.
7.1.3. Input device (ID) is a set of structures, devices and devices installed at the input of the supply line into the building or its separate part.
The input device, which also includes devices and devices of outgoing lines, is called input distribution device (IDU).
7.1.4. The main distribution board (MSB) is a distribution board through which the entire building or its separate part is supplied with electricity. The role of the main switchboard can be performed by an ASU or a low voltage switchboard of a substation.
7.1.5. Distribution point (DP) is a device in which protection devices and switching devices (or only protection devices) are installed for individual electrical receivers or their groups (electric motors, group panels).
7.1.6. A group panel is a device in which protection devices and switching devices (or only protection devices) are installed for separate groups of lamps, plug sockets and stationary electrical receivers.
7.1.7. Apartment panel - a group panel installed in an apartment and designed to connect the network that supplies lamps, plug sockets and stationary electrical receivers of the apartment.
7.1.8. Floor distribution panel - a panel installed on the floors of residential buildings and intended to supply power to apartments or apartment panels.
7.1.9. Electrical switchboard room is a room accessible only to qualified service personnel, in which VU, ASU, main switchboard and other distribution devices are installed.
7.1.10. Supply network - a network from a substation switchgear or a branch from overhead power lines to the VU, ASU, main switchboard.
7.1.11. Distribution network - network from VU, ASU, main switchboard to distribution points and switchboards.
7.1.12. Group network - a network from panels and distribution points to lamps, plug sockets and other electrical receivers.
GENERAL REQUIREMENTS. ELECTRIC SUPPLY
7.1.13. Electrical receivers must be powered from a 380/220 V network with a TM-5 or TM-S-8 grounding system.
When reconstructing residential and public buildings with a network voltage of 220/127 V or 3 x 220 V, it is necessary to provide for switching the network to a voltage of 380/220 V with a TM-8 or TM-S-5 grounding system.
7.1.14. External power supply to buildings must meet the requirements of Chapter 1.2.
7.1.15. In dormitories of various institutions, in schools and other educational institutions, etc. the construction of built-in and attached substations is not allowed.
In residential buildings, in exceptional cases, it is allowed to place built-in and attached substations using dry-type transformers in agreement with state supervisory authorities, while sanitary requirements for limiting noise and vibration levels must be fully met in accordance with current standards.
The construction and placement of built-in, attached and free-standing substations must be carried out in accordance with the requirements of the chapters of Section. 4.
7.1.16. It is recommended that power and lighting electrical receivers be powered from the same transformers.
7.1.17. The location and layout of transformer substations must provide for the possibility of round-the-clock unhindered access to them for personnel of the energy supply organization.
7.1.18. Power supply for safety lighting and evacuation lighting must be carried out in accordance with the requirements of Chapter. 6.1 and 6.2, as well as SNiP 23-05-95 “Natural and artificial lighting”.
7.1.19. If there are elevators in the building, which are also intended for transporting fire departments, their power supply must be provided in accordance with the requirements of Chapter. 7.8.
7.1.20. Electrical networks of buildings must be designed to power advertising lighting, shop windows, facades, illumination, outdoor, fire-fighting devices, dispatch systems, local television networks, light indicators of fire hydrants, safety signs, bell and other alarms, light fencing lights, etc., in in accordance with the design specifications.
7.1.21. When supplying single-phase consumers of buildings from a multiphase distribution network, it is allowed for different groups of single-phase consumers to have common N and PE conductors (five-wire network) laid directly from the ASU; combining N and PE conductors (four-wire network with PEN conductor) is not allowed.
When supplying single-phase consumers from a multiphase supply network with branches from overhead lines, when the PEN conductor of the overhead line is common to groups of single-phase consumers powered from different phases, it is recommended to provide protective shutdown of consumers when the voltage exceeds the permissible limit, arising due to load asymmetry when PEN breaks conductor. The disconnection must be carried out at the entrance to the building, for example, by influencing the independent release of the input circuit breaker using a maximum voltage relay, and both the phase (L) and neutral working (N) conductors must be disconnected.
When choosing devices and devices installed at the input, preference, other things being equal, should be given to devices and devices that remain operational when the voltage exceeds the permissible voltage, arising due to load asymmetry when the PEN or N conductor breaks, while their switching and other performance specifications may not be met.
In all cases, it is prohibited to have switching contact and non-contact elements in circuits of PE and PEN conductors.
Connections that can be disassembled with a tool are allowed, as well as connectors specially designed for this purpose.
INPUT DEVICES, DISTRIBUTION BOARDS, DISTRIBUTION POINTS, GROUP BOARDS
7.1.22. A VU or ASU must be installed at the entrance to the building. One or more VU or ASU may be installed in a building.
If there are several economically separate consumers in a building, it is recommended that each of them install an independent VU or ASU.
The ASU is also allowed to supply power to consumers located in other buildings, provided that these consumers are functionally connected.
For branches from overhead lines with a rated current of up to 25 A, the VU or ASU may not be installed at the inputs to the building if the distance from the branch to the group panel, which in this case performs the functions of the VU, is no more than 3 m. This section of the network must be carried out with a flexible copper cable with with a conductor cross-section of at least 4 mm2, flame retardant, laid in a steel pipe, and the requirements for ensuring a reliable contact connection with the branch wires must be met.
For air input, surge suppressors must be installed.
7.1.23. Before entering buildings, it is not allowed to install additional cable boxes to separate the service scope of external supply networks and networks inside the building. Such separation must be carried out in the ASU or main switchboard.
7.1.24. VU, ASU, main switchboard must have protection devices on all inputs of supply lines and on all outgoing lines.
7.1.25. Control devices must be installed at the input of supply lines to the VU, ASU, and main switchboards. On outgoing lines, control devices can be installed either on each line, or be common to several lines.
A circuit breaker should be considered as a protection and control device.
7.1.26. Control devices, regardless of their presence at the beginning of the supply line, must be installed at the inputs of the supply lines in retail premises, utilities, administrative premises, etc., as well as in consumer premises that are administratively and economically isolated.
7.1.27. The floor panel must be installed at a distance of no more than 3 m along the length of the electrical wiring from the supply riser, taking into account the requirements of Chapter. 3.1.
7.1.28. VU, ASU, main switchboard, as a rule, should be installed in electrical switchboard rooms accessible only to maintenance personnel. In areas prone to flooding, they should be installed above the flood level.
VU, ASU, main switchboard can be located in rooms allocated in operational dry basements, provided that these rooms are accessible to maintenance personnel and are separated from other rooms by partitions with a fire resistance limit of at least 0.75 hours.
When placing VU, ASU, main switchboards, distribution points and group panels outside electrical switchboard rooms, they must be installed in places convenient and accessible for maintenance, in cabinets with a degree of shell protection of at least IP 31.
The distance from pipelines (water supply, heating, sewerage, internal drains), gas pipelines and gas meters to the installation site must be at least 1 m.
7.1.29. Electrical switchboard rooms, as well as VU, ASU, main switchboards, are not allowed to be located under toilets, bathrooms, showers, kitchens (except for apartment kitchens), sinks, washing and steam rooms of bathhouses and other rooms associated with wet technological processes, except in cases where Special measures have been taken for reliable waterproofing to prevent moisture from entering the premises where the switchgear is installed.
It is not recommended to lay pipelines (plumbing, heating) through electrical rooms.
Pipelines (plumbing, heating), ventilation and other ducts laid through electrical switchboard rooms should not have branches within the room (with the exception of a branch to the heating device of the switchboard room itself), as well as hatches, valves, flanges, valves, etc.
Laying gas and pipelines with flammable liquids, sewerage and internal drains through these premises is not permitted.
Doors to electrical rooms must open outward.
7.1.30. The premises in which ASUs and main switchboards are installed must have natural ventilation and electric lighting. The room temperature should not be lower than +5°C.
7.1.31. Electrical circuits within the VU, ASU, main switchboard, distribution points, group panels should be made with wires with copper conductors.
ELECTRICAL WIRING AND CABLE LINES
7.1.32. Internal wiring must be carried out taking into account the following:
1. Electrical installations of different organizations, separate administratively and economically, located in the same building, can be connected by branches to a common supply line or fed by separate lines from the ASU or main switchboard.
2. It is allowed to connect several risers to one line. On branches to each riser supplying apartments in residential buildings with more than 5 floors, a control device combined with a protection device should be installed.
3. In residential buildings, lamps in staircases, lobbies, halls, floor corridors and other indoor premises outside apartments must be powered via independent lines from the ASU or separate group panels powered from the ASU. Connecting these lamps to floor and apartment panels is not allowed.
4. For staircases and corridors with natural light, it is recommended to provide automatic control of electric lighting depending on the illumination created by natural light.
5. It is recommended to supply power to electrical installations of non-residential buildings using separate lines.
7.1.33. Supply networks from substations to VU, ASU, main switchboard must be protected from short-circuit currents.
7.1.34. In buildings, cables and wires with copper conductors* should be used.
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* Until 2001, according to the existing construction backlog, the use of wires and cables with aluminum conductors is allowed.
Supply and distribution networks, as a rule, must be made of cables and wires with aluminum conductors if their design cross-section is 16 mm2 or more.
The power supply of individual electrical receivers related to the engineering equipment of buildings (pumps, fans, heaters, air conditioning units, etc.) can be provided by wires or cables with aluminum conductors with a cross-section of at least 2.5 mm2.
In museums, art galleries, and exhibition spaces, it is permitted to use lighting busbar trunking systems with a degree of protection of IP20, in which the branch devices to the lamps have detachable contact connections located inside the busbar trunking box at the time of switching, and busbar trunking systems with a degree of protection of 1P44, in which the branching devices to the lamps are made with using plug connectors that ensure the branch circuit is broken until the plug is removed from the socket.
In these premises, lighting busbars must be powered from distribution points by independent lines.
In residential buildings, the cross-sections of copper conductors must correspond to the calculated values, but not be less than those indicated in Table 7.1.1.
7.1.35. In residential buildings, laying vertical sections of the distribution network inside apartments is not allowed.
It is prohibited to lay wires and cables from the floor panel in a common pipe, common box or channel that supply lines to different apartments.
Fire-retardant installation in a common pipe, common box or channel of building structures made of non-combustible materials, wires and cables of supply lines of apartments together with wires and cables of group lines of working lighting of staircases, floor corridors and other indoor premises is allowed.
Table 7.1.1. The smallest permissible cross-sections of cables and wires of electrical networks in residential buildings
7.1.36. In all buildings, group network lines laid from group, floor and apartment panels to general lighting fixtures, plug sockets and stationary electrical receivers must be three-wire (phase - L, neutral working - N and neutral protective - PE conductors).
Combining zero working and zero protective conductors of different group lines is not allowed.
The neutral working and neutral protective conductors are not allowed to be connected on panels under a common contact terminal.
Conductor cross-sections must meet the requirements of clause 7.1.45.
7.1.37. Electrical wiring in the premises should be replaced: hidden - in the channels of building structures, embedded pipes; open - in electrical skirting boards, boxes, etc.
In technical floors, undergrounds, unheated basements, attics, ventilation chambers, damp and especially damp rooms, it is recommended that electrical wiring be carried out openly.
In buildings with building structures made of non-combustible materials, permanent, monolithic installation of group networks is allowed in the grooves of walls, partitions, ceilings, under plaster, in the floor preparation layer or in the voids of building structures, carried out with cable or insulated wires in a protective sheath. The use of permanently embedded wiring in panels of walls, partitions and ceilings, made during their manufacture at construction industry factories or carried out in the mounting joints of panels during the installation of buildings, is not allowed.
7.1.38. Electrical networks laid behind impenetrable suspended ceilings and in partitions are considered as hidden electrical wiring and should be installed: behind ceilings and in the voids of partitions made of flammable materials in metal pipes with localization capabilities and in closed boxes; behind ceilings and in partitions made of non-combustible materials* - in pipes and ducts made of non-flammable materials, as well as flame retardant cables. In this case, it must be possible to replace wires and cables.
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* Suspended ceilings made of non-combustible materials mean those ceilings that are made of non-combustible materials, while other building structures located above suspended ceilings, including interfloor ceilings, are also made of non-combustible materials.
7.1.39. In rooms for cooking and eating, with the exception of apartment kitchens, open laying of cables is allowed. Open wiring of wires in these rooms is not allowed.
In apartment kitchens, the same types of electrical wiring can be used as in living rooms and corridors.
7.1.40. In saunas, bathrooms, toilets, showers, as a rule, hidden electrical wiring should be used. Open cable routing is allowed.
In saunas, bathrooms, toilets, showers, laying wires with metal sheaths, in metal pipes and metal sleeves is not allowed.
In saunas for zones 3 and 4 in accordance with GOST R 50571.12-96 "Electrical installations of buildings. Part 7. Requirements for special electrical installations. Section 703. Premises containing sauna heaters" electrical wiring with a permissible insulation temperature of 170 ° C must be used.
7.1.41. Electrical wiring in attics must be carried out in accordance with the requirements of Section. 2.
7.1.42. Through the basements and technical undergrounds of sections of the building, it is allowed to lay power cables with a voltage of up to 1 kV, supplying electrical receivers of other sections of the building. The specified cables are not considered as transit; laying transit cables through basements and technical undergrounds of buildings is prohibited.
7.1.43. Open laying of transit cables and wires through storerooms and warehouses is not permitted.
7.1.44. The lines supplying refrigeration units of trade and public catering enterprises must be laid from the ASU or main switchboard of these enterprises.
7.1.45. The selection of conductor cross-sections should be carried out in accordance with the requirements of the relevant chapters of the PUE.
Single-phase two- and three-wire lines, as well as three-phase four- and five-wire lines when supplying single-phase loads, must have a cross-section of zero working (N) conductors equal to the cross-section of phase conductors.
Three-phase four- and five-wire lines when supplying three-phase symmetrical loads must have a cross-section of zero working (N) conductors equal to the cross-section of phase conductors, if the phase conductors have a cross-section of up to 16 mm2 for copper and 25 mm2 for aluminum, and for large cross-sections - at least 50 % cross-section of phase conductors.
The cross-section of PEN conductors must be at least the cross-section of N conductors and at least 10 mm2 for copper and 16 mm2 for aluminum, regardless of the cross-section of the phase conductors.
The cross-section of PE conductors must be equal to the cross-section of phase conductors with a cross-section of the latter up to 16 mm2, 16 mm2 with a cross-section of phase conductors from 16 to 35 mm2 and 50% of the cross-section of phase conductors with larger cross-sections.
The cross-section of PE conductors not included in the cable must be at least 2.5 mm2 - if there is mechanical protection and 4 mm2 - if there is none.
INTERNAL ELECTRICAL EQUIPMENT
7.1.46. In food preparation rooms, except for apartment kitchens, lamps with incandescent lamps installed above workplaces (stoves, tables, etc.) must have protective glass underneath. Lamps with fluorescent lamps must have grilles or grids or lamp holders that prevent the lamps from falling out.
7.1.47. In bathrooms, showers and toilets, only electrical equipment should be used that is specifically designed for installation in the corresponding areas of these premises in accordance with GOST R 50571.11-96 "Electrical installations of buildings. Part 7. Requirements for special electrical installations. Section 701. Bathrooms and shower rooms", the following requirements must be met:
- electrical equipment must have a degree of protection against water not lower than:
in zone 0 - 1РХ7;
in zone 1 - 1РХ5;
in zone 2 - 1РХ4 (1РХ5 in public baths);
in zone 3 - 1РХ1 (1РХ5 in public baths);
- in zone 0, electrical appliances with voltages up to 12 V, intended for use in the bath, can be used, and the power source must be located outside this zone;
- in zone 1 only water heaters can be installed;
- in zone 2 water heaters and lamps of protection class 2 can be installed;
- in zones 0, 1 and 2, the installation of junction boxes, switchgear and control devices is not allowed.
In the bathrooms of apartments and hotel rooms, it is allowed to install plug sockets in zone 3 in accordance with GOST R 50571.11-96, connected to the network through isolation transformers or protected by a residual current device that responds to a differential current not exceeding 30 mA.
Any switches and sockets must be located at a distance of at least 0.6 m from the doorway of the shower stall.
7.1.49. In buildings with a three-wire network (see clause 7.1.36), plug sockets with a current of at least 10 A with a protective contact must be installed.
Plug sockets installed in apartments, living rooms in dormitories, as well as in rooms for children in child care institutions (kindergartens, nurseries, schools, etc.) must have a protective device that automatically closes the sockets of the socket when the plug is removed.
7.1.50. The minimum distance from switches, sockets and electrical installation elements to gas pipelines must be at least 0.5 m.
In rooms for children in children's institutions (kindergartens, nurseries, schools, etc.), switches should be installed at a height of 1.8 m from the floor.
7.1.52. In saunas, bathrooms, toilets, soap rooms, steam rooms, washing rooms, laundries, etc. installation of switchgear and control devices is not permitted.
In washbasin rooms and zones 1 and 2 (GOST R 50571.11-96) of bathrooms and shower rooms, it is allowed to install switches operated by a cord.
7.1.53. Switching devices for lighting networks in attics that have building structure elements (roofing, trusses, rafters, beams, etc.) made of flammable materials must be installed outside the attic.
7.1.54. Switches for work lamps, safety and evacuation lighting of premises intended for the presence of a large number of people (for example, retail premises of shops, canteens, hotel lobbies, etc.) must be accessible only to service personnel.
7.1.55. A lamp should be installed above each entrance to the building.
7.1.56. House license plates and fire hydrant signs installed on exterior walls of buildings must be illuminated. Electric light sources for license plates and hydrant indicators must be powered from the internal lighting network of the building, and fire hydrant indicators installed on external lighting poles must be powered from the external lighting network.
7.1.57. Fire safety devices and security alarms, regardless of the category of reliability of the building's power supply, must be powered from two inputs, and in their absence, by two lines from one input. Switching from one line to another should be automatic.
7.1.58. Electric motors, distribution points, separately installed switching devices and protective devices installed in the attic must have a degree of protection of at least IP44.
ELECTRICITY ACCOUNTING
7.1.59. In residential buildings, one single- or three-phase billing meter (with three-phase input) should be installed for each apartment.
7.1.60. Calculation meters in public buildings that house several electricity consumers must be provided for each consumer, isolated in administrative and economic terms (studio, shops, workshops, warehouses, housing maintenance offices, etc.).
7.1.61. In public buildings, estimated electricity meters must be installed on the ASU (main switchboard) at the points of balance demarcation with the energy supply organization. If there are built-in or attached transformer substations, the power of which is fully used by consumers of a given building, the calculated meters should be installed at the low-voltage terminals of power transformers on combined low-voltage switchboards, which are also the building’s ASU.
ASU and metering devices for different subscribers located in the same building may be installed in one common room. By agreement with the energy supplying organization, settlement meters can be installed at one of the consumers, from which the ASU supplies other consumers located in the building. At the same time, control meters should be installed at the inputs of the supply lines in the premises of these other consumers for settlements with the main subscriber.
7.1.62. Estimated meters for the general house load of residential buildings (lighting of staircases, building management offices, yard lighting, etc.) are recommended to be installed in ASU cabinets or on main switchboard panels.
When installing apartment panels in the hallways of apartments, meters, as a rule, should be installed on these panels; installation of meters on floor panels is allowed.
7.1.64. To safely replace a meter directly connected to the network, a switching device must be provided in front of each meter to remove voltage from all phases connected to the meter.
Disconnecting devices for removing voltage from settlement meters located in apartments must be located outside the apartment.
7.1.65. After the meter connected directly to the network, a protection device must be installed. If several lines equipped with protection devices extend after the meter, installation of a common protection device is not required.
7.1.67. Grounding and protective safety measures for electrical installations of buildings must be carried out in accordance with the requirements of Chapter. 1.7 and additional requirements given in this section.
7.1.68. In all rooms, it is necessary to connect the open conductive parts of general lighting lamps and stationary electrical receivers (electric stoves, boilers, household air conditioners, electric towels, etc.) to the neutral protective conductor.
7.1.69. In building premises, metal cases of single-phase portable electrical appliances and desktop office equipment of class I according to GOST 12.2.007.0-75 "SSBT. Electrical products. General safety requirements" must be connected to the protective conductors of a three-wire group line (see clause 7.1.36).
The metal frames of partitions, doors and frames used for laying cables must be connected to the protective conductors.
7.1.70. In rooms without increased danger, it is allowed to use pendant lamps that are not equipped with clamps for connecting protective conductors, provided that the hook for their suspension is insulated. The requirements of this paragraph do not cancel the requirements of paragraph 7.1.36 and are not the basis for making two-wire electrical wiring.
7.1.71. To protect group lines supplying plug sockets for portable electrical appliances, it is recommended to provide residual current devices (RCDs).
7.1.72. If the overcurrent protection device (circuit breaker, fuse) does not provide an automatic shutdown time of 0.4 s at a rated voltage of 220 V due to low values of short circuit currents and the installation (apartment) is not covered by a potential equalization system, the installation of an RCD is mandatory.
7.1.73. When installing an RCD, selectivity requirements must be consistently met. With two- and multi-stage circuits, the RCD located closer to the power source must have a setting and response time that is at least 3 times greater than that of the RCD located closer to the consumer.
7.1.74. In the coverage area of the RCD, the neutral working conductor should not have connections with grounded elements and the neutral protective conductor.
7.1.75. In all cases of use, the RCD must ensure reliable switching of load circuits, taking into account possible overloads.
It is not allowed to use RCDs in group lines that do not have overcurrent protection, without an additional device that provides this protection.
When using RCDs that do not have overcurrent protection, their design verification in overcurrent modes is necessary, taking into account the protective characteristics of the upstream device that provides overcurrent protection.
7.1.77. In residential buildings, it is not allowed to use RCDs that automatically disconnect the consumer from the network in the event of a loss or unacceptable drop in the network voltage. In this case, the RCD must remain operational for a period of at least 5 s when the voltage drops to 50% of the rated voltage.
7.1.78. In buildings, RCDs of type “A” can be used, which respond to both alternating and pulsating fault currents, or “AC”, which react only to alternating leakage currents.
The source of pulsating current is, for example, washing machines with speed controllers, adjustable light sources, televisions, VCRs, personal computers, etc.
7.1.79. In group networks feeding plug sockets, an RCD with a rated operating current of no more than 30 mA should be used.
It is allowed to connect several group lines to one RCD through separate circuit breakers (fuses).
Installation of RCDs in lines supplying stationary equipment and lamps, as well as in general lighting networks, is usually not required.
7.1.81. The installation of RCDs is prohibited for electrical receivers, the disconnection of which could lead to situations dangerous for consumers (disabling the fire alarm, etc.).
7.1.82. It is mandatory to install an RCD with a rated response current of no more than 30 mA for group lines supplying electrical outlets located outdoors and in particularly dangerous and high-risk areas, for example in zone 3 of bathrooms and shower rooms in apartments and hotel rooms.
7.1.83. The total leakage current of the network, taking into account the connected stationary and portable electrical receivers in normal operation, should not exceed 1/3 of the rated current of the RCD. In the absence of data, the leakage current of electrical receivers should be taken at the rate of 0.4 mA per 1 A of load current, and the network leakage current at the rate of 10 μA per 1 m of phase conductor length.
7.1.84. To increase the level of fire protection during short circuits to grounded parts, when the current value is insufficient to trigger the maximum current protection, at the entrance to an apartment, individual house, etc. It is recommended to install an RCD with a trip current of up to 300 mA.
7.1.85. For residential buildings, if the requirements of clause 7.1.83 are met, the functions of the RCD according to clauses. 7.1.79 and 7.1.84 can be performed by one device with an operating current of no more than 30 mA.
7.1.86. If the RCD is intended for protection against electric shock and fire or only for protection against fire, then it must disconnect both the phase and neutral working conductors; overcurrent protection in the neutral working conductor is not required.
7.1.87. At the entrance to the building, a potential equalization system must be installed by combining the following conductive parts:
- main (main) protective conductor;
- main (main) grounding conductor or main grounding clamp;
- steel pipes for communications between buildings and between buildings;
- metal parts of building structures, lightning protection, central heating, ventilation and air conditioning systems. Such conductive parts must be connected to each other at the entrance to the building.
7.1.88. All open conductive parts of stationary electrical installations, third-party conductive parts and neutral protective conductors of all electrical equipment (including plug sockets) must be connected to the additional potential equalization system.
For bathrooms and shower rooms, an additional potential equalization system is mandatory and must include, among other things, the connection of third-party conductive parts extending outside the premises. If there is no electrical equipment with neutral protective conductors connected to the potential equalization system, then the potential equalization system should be connected to the PE bus (clamp) at the input. Heating elements embedded in the floor must be covered with a grounded metal mesh or a grounded metal shell connected to a potential equalization system. As additional protection for heating elements, it is recommended to use an RCD with a current of up to 30 mA.
It is not allowed to use local potential equalization systems for saunas, baths and shower rooms.
Complain
Section 4. Switchgears and substations
Chapter 4.2. Switchgears and substations with voltage above 1 kV
Open distribution devices
4.2.45. In outdoor switchgear of 110 kV and above, passage must be provided for mobile installation and repair mechanisms and devices, as well as mobile laboratories.
4.2.46. The connection of flexible wires in spans must be made by crimping using connecting clamps, and connections in loops at supports, connecting branches in a span and connecting to hardware clamps - by crimping or welding. In this case, the connection of branches in the span is carried out, as a rule, without cutting the span wires.
Soldering and twisting of wires is not allowed.
Bolted connections are allowed only on device terminals and on branches to arresters, arresters, coupling capacitors and voltage transformers, as well as for temporary installations for which the use of permanent connections requires a large amount of work on rewiring busbars.
Garlands of insulators for hanging busbars in outdoor switchgear can be single-circuit. If a single-chain garland does not satisfy the conditions of mechanical loads, then a double-chain one should be used.
Dividing (mortise) garlands are not allowed, with the exception of garlands with the help of which high-frequency barriers are suspended.
The fastening of flexible bars and cables in tension and suspension clamps in terms of strength must comply with the requirements given in 2.115.
4.2.47. Connections of rigid busbars in spans should be made by welding, and connections of busbars of adjacent spans should be made using compensating devices attached to the busbars, usually by welding. It is allowed to connect compensating devices to spans using bolted connections.
Branches from rigid busbars can be made either flexible or rigid, and their connection to the spans should be carried out, as a rule, by welding. Connection using bolted connections is permitted only if justified.
4.2.48. Branches from outdoor switchgear busbars, as a rule, should be located below the busbars.
Suspension of a busbar in one span over two or more sections or busbar systems is not permitted.
4.2.49. Loads on tires and structures from wind and ice, as well as design air temperatures must be determined in accordance with the requirements of building codes and regulations. In this case, the deflection of rigid tires should not exceed 1/80 of the span length.
When determining loads on structures, the weight of a person with tools and installation equipment should be additionally taken into account when using:
- tension garlands of insulators - 2.0 kN;
- supporting garlands - 1.5 kN;
- support insulators - 1.0 kN.
The pull of descents to outdoor switchgear devices should not cause unacceptable mechanical stress and unacceptable proximity of wires under design climatic conditions.
4.2.50. The calculated mechanical forces transmitted during a short circuit by rigid busbars to the support insulators should be taken in accordance with the requirements of Chapter 1.4.
4.2.51. The mechanical safety factor for loads corresponding to 4.2.49 should be taken:
- for flexible tires - at least 3 in relation to their temporary breaking resistance;
- for suspended insulators - at least 4 in relation to the guaranteed minimum destructive load of the entire insulator (mechanical or electromechanical, depending on the requirements of the standards for the type of insulator used);
- for coupling reinforcement of flexible tires - at least 3 in relation to the minimum breaking load;
- for support insulators of rigid busbars - not less than 2.5 in relation to the guaranteed minimum destructive load of the insulator.
4.2.52. Supports for fastening outdoor switchgear busbars must be designed as intermediate or end supports in accordance with Chapter 2.5.
4.2.54. The shortest clear distances between bare current-carrying parts of different phases, from bare current-carrying parts to the ground, grounded structures and fences, as well as between bare current-carrying parts of different circuits should be taken according to Table 4.2.5 (Fig. 4.2.3-4.2.12) .
Table 4.2.5. The shortest clear distances from live parts to various elements of outdoor switchgear (substations) 10-750 kV, protected by arresters, and outdoor switchgear 220-750 kV, protected by surge suppressors 5, (in the denominator) (Fig. 4.2.3-4.2.12)
| Figure number | Name of distance | Designation | Insulation distance, mm, for rated voltage, kV |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 4.2.3 4.2.4 4.2.5 | From live parts, equipment and insulation under voltage, to extended grounded structures and to permanent internal fences with a height of at least 2 m, as well as to stationary inter-cell screens and fire partitions | 1800
| 2500
| 3750
| 5500
|
||||||
| From live parts, equipment elements and insulation under voltage, to grounded structures: apparatus head - support, wire - stand, traverse, wire - ring, rod | A 1 f-3 | 1600
| 2200
| 3300
| 5000
|
||||||
| 4.2.3 4.2.4 4.2.11 | Between live parts of different phases | A f-f | 2000
| 1800
| 4200
| 8000
|
|||||
| From live parts, equipment and insulation under voltage, to permanent internal barriers up to 1.6 m high and to transported equipment | 2550
| 3250
| 4500
| 6300
|
|||||||
| Between current-carrying parts of different circuits in different planes with the lower circuit maintained and the upper circuit not disconnected | 3000
| 4000
| 5000
| 7000
|
|||||||
| From unfenced live parts to the ground or to the roof of buildings with the greatest sag of wires | 4500
| 5000
| 6450
| 8200
|
|||||||
| Between live parts of different circuits in different planes, as well as between live parts of different circuits horizontally when servicing one circuit and an open other | 3600
| 4200
| 5200
| 7000
|
|||||||
| From live parts to the top edge of an external fence or to a building or structure | 3800
| 4500
| 5750
| 7500
|
|||||||
| From the contact and the disconnector blade in the open position to the busbar connected to the second contact | 2200
| 3100
| 4600
| 7500
|
|||||||
1 For insulation elements exposed to a distributed potential, the insulation distances should be taken taking into account the actual potential values at different points on the surface. In the absence of data on potential distribution, one should conditionally assume a rectilinear law of potential drop along the insulation from the full rated voltage (from the side of live parts) to zero (from the side of grounded parts).
2 The distance from live parts or insulation elements (on the side of live parts) that are energized to the dimensions of transformers transported along railway tracks can be taken less than size B, but not less than size A 1 f-3.
3 Distances A f-3, A 1 f-3 and A f-f for outdoor switchgear 220 kV and above, located at an altitude of more than 1000 m above sea level, must be increased in accordance with the requirements of state standards, and distances A f-f, B and D 1 must be checked under the terms of the corona restriction.
4 For a voltage of 750 kV, the table shows the distances A f-f between parallel wires more than 20 m long; distances A f-f, between screens, crossing wires, parallel wires up to 20 m long for a 750 kV outdoor switchgear with surge arresters are equal to 7000 mm, and for a 750 kV outdoor switchgear with surge arresters - 5500 mm.
5 Surge suppressors have a protective level for limiting switching overvoltages phase - ground 1.8 U f.
If in installations located in high mountains, the distances between phases increase compared to those given in Table 4.2.5 based on the results of corona testing, the distances to grounded parts must be increased accordingly.
Fig.4.2.3. The smallest clear distances with rigid busbars between live and grounded parts ( A f-3, A 1 f-3) and between live parts of different phases ( A f-f)
Fig.4.2.4. The smallest clear distances with flexible busbars between live and grounded parts and between live parts of different phases located in the same horizontal plane
4.2.55. The smallest clear distances with rigid buses (see Fig. 4.2.3.) between current-carrying and grounded parts A f-3 and between live parts of different phases A f-f should be taken according to Table 4.2.5, and for flexible ones (see Fig. 4.2.4) - should be determined as follows:
; 
; 
,
Where a = fsina; f- wire sag at a temperature of +15 °C, m; a = arc tan PIQ; Q- design load from the weight of the wire per 1 m of wire length, daN/m; P- calculated linear wind load on the wire, daN/m; in this case, the wind speed is taken equal to 60% of the value chosen when calculating building structures.
4.2.56. The smallest permissible clear distances between energized neighboring phases at the moment of their closest approach under the action of short-circuit currents must be no less than those given in Table 2.5.17, taken at the highest operating voltage.
In a flexible busbar made of several wires in a phase, in-phase spacers should be installed.
4.2.57. The shortest distances from live parts and insulators under voltage to permanent internal fences should be (Table 4.2.5, Fig. 4.2.5);
Fig.4.2.5. The shortest distances from live parts and live insulation elements to permanent internal fences
horizontally - no less than size B with a fence height of 1.6 m and not less than A f-3 with a fence height of 2.0 m. The second option is recommended for use in cramped conditions at the substation site;
vertically - no less than the size A f-3, measured in the plane of the fence from a point located at a height of 2.7 m from the ground.
4.2.58. Live parts (terminals, busbars, descents, etc.) may not have internal fences if they are located above the level of planning or ground communication structures at a height of at least the values corresponding to the size G according to Table 4.2.5 (Fig. 4.2.6.).
Fig.4.2.6. The shortest distances from unprotected live parts and from the lower edge of porcelain insulators to the ground
Unprotected current-carrying parts connecting the capacitor of high-frequency communication, telemechanics and protection devices with the filter must be located at a height of at least 2.5 m. It is recommended to install the filter at a height that allows repair (adjustment) of the filter without removing the voltage from the connection equipment.
Transformers and devices in which the lower edge of the porcelain (polymer material) insulators is located above the level of planning or ground communication structures at a height of at least 2.5 m are allowed not to be fenced (see Fig. 4.2.6). At a lower height, the equipment must have permanent fences that meet the requirements of 4.2.29, located from transformers and devices at distances not less than those given in 4.2.57. Instead of permanent fences, it is allowed to install canopies to prevent service personnel from touching insulation and live equipment elements.
4.2.59. The distances from unprotected live parts to the dimensions of machines, mechanisms and transported equipment must be at least B according to Table 4.2.5 (Fig. 4.2.7.).
Fig.4.2.7. The shortest distances from live parts to transported equipment
4.2.60. The distances between the nearest unprotected current-carrying parts of different circuits must be selected from the condition of safe servicing of one circuit while the second is not disconnected. When unprotected current-carrying parts of different circuits are located in different (parallel or perpendicular) planes, the vertical distances must be at least IN, and horizontally - the size D 1 according to table 4.2.5 (Fig. 4.2.8). For different voltages, dimensions IN And D 1 are accepted at a higher voltage.
Fig.4.2.8. The smallest distances between current-carrying parts of different circuits located in different planes with servicing of the lower circuit while the upper circuit is not disconnected
Fig.4.2.9. The smallest horizontal distances between live parts of different circuits with servicing one circuit while the other is not disconnected
Size IN determined from the condition of servicing the lower circuit with the upper one not disconnected, and the size D 1 - servicing one circuit while the other is not disconnected. If such maintenance is not provided, the distance between live parts of different circuits in different planes must be taken in accordance with 4.2.53; in this case, the possibility of the wires coming closer together under operating conditions (under the influence of wind, ice, temperature) must be taken into account.
4.2.61. The distances between live parts and the upper edge of the external fence must be at least D according to Table 4.2.5 (Fig. 4.2.10).
Fig.4.2.10. The shortest distances from live parts to the top edge of the outer fence
4.2.62. The distances from the moving contacts of the disconnectors in the off position to the grounded parts must be no less than the dimensions A f-3 and A 1 f-3; before busbar of its phase connected to the second contact - not less than the size AND; before busbar connection of other connections - not less than the size A f-f according to table 4.2.5 (Fig. 4.2.11).
Fig.4.2.11. The shortest distances from the moving contacts of disconnectors in the off position to grounded and live parts
4.2.63. The horizontal distances between live parts of the outdoor switchgear and buildings or structures (indoor switchgear, control panel room, transformer tower, etc.) must be at least D, and vertically with the greatest sagging of the wires - no less than the size G according to Table 4.2.5 (Fig. 4.2.12).
Fig.4.2.12. The shortest distances between live parts and buildings and structures
4.2.64. Laying overhead lighting lines, overhead communication lines and signaling circuits above and below live parts of the outdoor switchgear is not allowed.
4.2.65. Distances from hydrogen warehouses to outdoor switchgear, transformers, synchronous compensators must be at least 50 m; to overhead line supports - at least 1.5 times the height of the support; to PS buildings with the number of cylinders stored in the warehouse up to 500 pcs. - at least 20 m, over 500 pcs. - at least 25 m; to the external fence of the substation - at least 5.5 m.
4.2.66. Distances from openly installed electrical devices to substation water coolers must be no less than the values given in Table 4.2.6.
Table 4.2.6. The shortest distance from openly installed electrical devices to substation water coolers
For areas with estimated outside air temperatures below minus 36 °C, the distances given in Table 4.2.6 should be increased by 25%, and with temperatures above minus 20 °C - reduced by 25%. For reconstructed objects, the distances given in Table 4.2.6 can be reduced, but not more than by 25%.
4.2.67. The distances from the switchgear and substation equipment to the indoor switchgear buildings and other process buildings and structures, to the design bureau, control room, and control system are determined only by technological requirements and should not increase due to fire conditions.
4.2.68. Fire-fighting distances from oil-filled equipment with an oil mass in a piece of equipment of 60 kg or more to industrial buildings with room categories B1-B2, G and D, as well as to residential and public buildings must be no less than:
- 16 m - with fire resistance degrees of these buildings I and II;
- 20 m - for degree III;
- 24 m - for degrees IV and V.
When installing oil-filled transformers with an oil mass of 60 kg or more near the walls of industrial buildings with room categories G and D, electrically connected to equipment installed in these buildings, distances less than those specified are allowed. At the same time, at a distance from them of more than 10 m and outside the boundaries of areas wide B(Fig. 4.2.13) there are no special requirements for walls, windows and doors of buildings.
Fig.4.2.13. Requirements for open installation of oil-filled transformers in buildings with production categories G and D
At a distance of less than 10 m to transformers within areas wide B The following requirements must be met:
1) up to height D(up to the transformer input level) windows are not allowed;
2) at a distance G less than 5 m and fire resistance levels of buildings IV and V, the wall of the building must be made according to fire resistance degree I and rise above the roof made of combustible material by at least 0.7 m;
3) at a distance G less than 5 m and fire resistance levels of buildings I, II, III, as well as at a distance G 5 m or more without restrictions on fire resistance at a height of d before d + f non-opening windows filled with reinforced glass or glass blocks with frames made of fireproof material are allowed; higher d + f- windows opening into the building, with openings equipped on the outside with metal mesh with cells no larger than 25x25 mm;
4) at a distance G less than 5 m at a height of less d, and when G 5 m or more at any height, doors made of fireproof or fire-resistant materials with a fire resistance rating of at least 60 minutes are allowed;
5) ventilation intake openings in the wall of the building at a distance G less than 5 m are not allowed; exhaust openings with the emission of uncontaminated air within the specified limit are allowed at a height d;
6) at a distance G from 5 to 10 m ventilation openings in the enclosing structures of cable rooms on the side of transformers in an area wide B not allowed.
Dimensions shown in Fig. 4.2.13 a - d And A are accepted up to the most protruding parts of transformers at a height of no more than 1.9 m from the ground surface. With a unit power of transformers up to 1.6 MVA, distances V≥ 1.5 m; e ≥ 8 m; more than 1.6 MVA V≥ 2 m; e ≥ 10 m distance b accepted according to 4.2.217, distance G must be at least 0.8 m.
The requirements of this paragraph also apply to outdoor PTS.
4.2.69. To prevent the spread of oil and the spread of fire in the event of damage to oil-filled power transformers (reactors) with an amount of oil of more than 1 ton per unit, oil receivers, oil drains and oil collectors must be made in compliance with the following requirements:
1) the dimensions of the oil receiver must protrude beyond the dimensions of the transformer (reactor) by at least 0.6 m with an oil mass of up to 2 tons; 1 m with a weight from 2 to 10 tons; 1.5 m with a weight from 10 to 50 tons; 2 m with a mass of more than 50 tons. In this case, the dimensions of the oil receiver can be taken less by 0.5 m from the side of the wall or partition located from the transformer (reactor) at a distance of less than 2 m;
2) the volume of the oil receiver with oil drainage should be calculated to simultaneously receive 100% of the oil poured into the transformer (reactor).
The volume of the oil receiver without oil drainage should be calculated to receive 100% of the volume of oil poured into the transformer (reactor) and 80% of water from fire extinguishing agents based on irrigation of the areas of the oil receiver and the side surfaces of the transformer (reactor) with an intensity of 0.2 l/s m 2 ; within 30 minutes;
3) the arrangement of oil receivers and oil drains must prevent the flow of oil (water) from one oil receiver to another, the spreading of oil along cable and other underground structures, the spread of fire, clogging of the oil drain and its clogging with snow, ice, etc.;
4) oil receivers for transformers (reactors) with an oil volume of up to 20 tons can be made without oil drainage. Oil receivers without oil drainage must be of a recessed design and covered with a metal grate, on top of which a layer of clean gravel or washed granite crushed stone with a thickness of at least 0.25 m, or non-porous crushed stone of another type with particles from 30 to 70 mm must be poured. The level of the total oil volume in the oil receiver must be at least 50 mm below the grate.
Removal of oil and water from the oil receiver without draining the oil must be provided by mobile means. In this case, it is recommended to implement a simple device to check the absence of oil (water) in the oil receiver;
5) oil receivers with oil drainage can be made both recessed and non-recessed (the bottom is at the level of the surrounding layout). When making a recessed television receiver, the installation of side guards is not required if this ensures the volume of the oil receiver specified in paragraph 2.
Oil receivers with oil drainage can be designed:
- with the installation of a metal grate on the oil receiver, on top of which gravel or crushed stone is poured with a layer thickness of 0.25 m;
- without a metal grate with gravel poured onto the bottom of the oil receiver with a layer thickness of at least 0.25 m.
A non-buried oil receiver should be made in the form of side guards for oil-filled equipment. The height of side fences should be no more than 0.5 m above the level of the surrounding layout.
The bottom of the oil receiver (recessed and non-recessed) must have a slope of at least 0.005 towards the pit and be filled with cleanly washed granite (or other non-porous rock) gravel or crushed stone with a fraction of 30 to 70 mm. The thickness of the backfill must be at least 0.25 m.
The top level of gravel (crushed stone) must be at least 75 mm below the top edge of the side (when oil receivers are installed with side guards) or the level of the surrounding layout (when oil receivers are installed without side guards).
It is allowed not to fill the bottom of the oil receivers over the entire area with gravel. In this case, installation of fire arresters should be provided on oil drainage systems from transformers (reactors);
6) when installing oil-filled electrical equipment on the reinforced concrete floor of a building (structure), an oil drainage device is mandatory;
7) oil drains must ensure that oil and water used to extinguish a fire are removed from the oil receiver by automatic stationary devices and hydrants to a fire-safe distance from equipment and structures: 50% of the oil and the full amount of water must be removed in no more than 0.25 hours Oil drains can be made in the form of underground pipelines or open ditches and trays;
8) oil collectors must be of a closed type and must contain the full volume of oil from a single piece of equipment (transformers, reactors) containing the largest amount of oil, as well as 80% of the total (taking into account a 30-minute reserve) water consumption from fire extinguishing agents. Oil collectors must be equipped with an alarm for the presence of water with a signal output to the control panel. The internal surfaces of the oil receiver, oil receiver guard and oil collector must be protected with an oil-resistant coating.
4.2.70. At substations with transformers 110-150 kV with a unit power of 63 MVA or more and transformers 220 kV and above with a unit power of 40 MVA or more, as well as at substations with synchronous compensators for fire extinguishing, a fire-fighting water supply should be provided with power from the existing external network or from an independent water supply source. Instead of a fire-fighting water supply system, it is allowed to provide for water intake from ponds, reservoirs, rivers and other bodies of water located at a distance of up to 200 m from the substation using mobile fire fighting equipment.
At substations with 35-150 kV transformers with a unit power of less than 63 MVA and 220 kV transformers with a unit power of less than 40 MVA, fire-fighting water supply and a reservoir are not provided.
4.2.71. Switchgear and package transformer substations for external installation must be located on a planned site at a height of at least 0.2 m from the planning level with a service area located near the cabinets. In areas with a calculated snow cover height of 1.0 m and above and a duration of its occurrence of at least 1 month, it is recommended to install outdoor switchgear and package transformer substations at a height of at least 1 m.
The location of the device should ensure convenient rolling out and transportation of transformers and the withdrawable part of the cells.
×
The minimum insulation distances in the air for indoor switchgear with voltages from 3 to 220 kV, ensuring safety conditions and ease of maintenance, are established by the Electrical Regulations.
The minimum distances from current-carrying parts to grounded structures A f and also between current-carrying parts of opposite phases A f f are shown in Fig. 4 and table. 1. Minimum distances from live parts to solid and mesh fences have also been established (dimension B in Fig. 5 and Table 2).
Unfenced conductors belonging to various circuits located on both sides of the service corridor must be spaced from each other at a distance of at least dimension D in Fig. 5, and the distance from the contacts and blades of the disconnectors in the off position to the busbar of its phase connected to the second contact is not less than the size Zh. 
Rice. 4. Minimum distance between phases and between them and grounded parts of the switchgear
The smallest distance and spark plug from live parts to various elements of the switchgear
Figure number | Name of distances | Designations | Insulation distance, mm, for voltage, kV |
|||||||
From live parts to grounded structures and building parts | ||||||||||
Between conductors of different phases | ||||||||||
From live parts to solid fencing | ||||||||||
Or live parts up to mesh fences | ||||||||||
Between unfenced live parts of different circuits | ||||||||||
From unprotected live parts to the floor | ||||||||||
From unfenced outputs from the indoor switchgear to the ground when they do not enter the territory of the outdoor switchgear and in the absence of passage under the outputs | ||||||||||
Rice. 5. Minimum distances between live parts of different circuits and between them and mesh fences
Unprotected conductors belonging to different circuits and located at a height exceeding dimension D (Fig. 6) must be located from each other at a distance that ensures safe service in the presence of voltage in adjacent circuits. If the height of the conductors is below dimension D, they must be fenced. The height of the passage under the fence must be at least 1.9 m. Devices in which the lower edge of the porcelain insulators is located above the floor level at a height of 2.2 m or more are allowed not to be fenced. For overhead inputs into the closed switchgear that do not cross vehicle passages, the distance from the lowest point of the wire is a fence 1.6 m high. Fences can be solid, mesh or lattice.
Rice. 6. Minimum distance from wires to the ground
Live parts (terminals, busbars, descents, etc.) may not have internal fences if they are located above the planning level or the level of the structure on which people can walk (for example, cable duct slabs) at a height of at least size G (Table .2). Transformers and devices in which the lower edge of the porcelain is equal to the ground surface must be no less than size E (Fig. 6) indicated in table. 1. The distances from conductors to solid fences must be no less than dimension B in Fig. 7.
Open switchgears (OSDs) are made for voltages of 35 kV and higher, and, like switchgear switchgears, they are made in accordance with the requirements of the PUE. The territory of the outdoor switchgear and substation must be fenced with an external fence 1.8-2 m high. 
Rice. 7. Minimum distances from conductors to solid fences
Table 2.
The shortest distance from live parts to various elements of the outdoor switchgear (substation)
Name of distance | Designation | Insulation distance, mm, for rated voltage, kV |
|||||||
From live parts or elements | |||||||||
Between wires of different phases | |||||||||
From live parts or from energized equipment and insulation elements, to permanent internal fences 1.6 m high, to the dimensions of transported equipment | |||||||||
Between current-carrying parts of different circuits in different planes with the lower circuit being serviced and the upper circuit not disconnected | |||||||||
From unfenced live parts to the ground or to the roof of buildings with the greatest sagging of wires | |||||||||
Between live parts of different circuits in different planes, as well as between live parts of different circuits horizontally when servicing one circuit and the other not disconnected, from live parts to the outer edge of the outer fence, between live parts and buildings or structures | |||||||||
From the contact and the disconnector blade in the open position to the busbar connected to the second contact | |||||||||
When an outdoor switchgear is located on the territory of a substation, it must be fenced inside; it is located above the planning level or the level of the structure at a height of at least 2.5 m; it is allowed not to be fenced. The distance between adjacent transformers depends on their power and is allowed at least 1.25 m, and between a transformer and a fire-resistant building - at least 0.8 m. Windows and doors in the building wall must be located above the level of the transformer cover. The minimum distances in the air between current-carrying parts of opposite phases and from current-carrying parts to grounded structures A1 and Af3 (Fig. 8) for outdoor switchgear are set somewhat larger than the corresponding distances for indoor switchgear, taking into account unfavorable operating conditions (rain, snow, dust, etc.) (Table .2). 
Rice. 8. Minimum distances in outdoor switchgear between rigid live parts and from them to grounded structures
Rice. 9. Minimum distances in outdoor switchgear between wires and from them to grounded structures
The greatest distances from live parts to fences (Fig. 10), to the ground surface (Fig. 11), to transported equipment (Fig. 12) and others (Fig. 13-17) are also increased. During multiphase short circuits, flexible conductors of opposite phases deviate from their normal position, causing swings and the danger of unacceptable approaching and even clashing of conductors. Based on this, the distance between phases, as well as between wires and grounded structures, is established taking into account the greatest possible deviation a of flexible conductors during short circuit and wind (see Fig. 9).
Rice. 10. Minimum distances from live parts to permanent fences
To prevent the spread of oil and the spread of fire in the event of damage to oil-filled power transformers and tank switches of 110 kV and above, oil receivers, oil drains and oil collectors must be installed. 
Rice. 11. Minimum distances from unfenced wires to ground
The dimensions of the oil receiver must extend beyond the dimensions of a single oil-filled electrical equipment. The volume of the oil receiver must be designed to simultaneously receive 100% of the oil contained in the transformer housing. For tank switches, the oil receiver must be designed to receive 80% of the oil contained in one tank. Oil drains must ensure that oil and water used to extinguish a fire are removed from the oil receiver. They are made in the form of underground pipelines or open ditches and trays. Oil collectors must be designed for the full volume of oil of the individual equipment containing the largest amount of oil, and must be of a closed type.
Installation of complete outdoor switchgear (KRUN) and complete transformer substations (CTS) must meet the following requirements:
Switchgear and package transformer substations must be located on a planned site at a height of at least 0.2 m from the planning level with a device near the cabinets of the site for maintenance;
the location of the device must ensure the transportation of transformers and withdrawable parts of cells;
KRUN and KTP must, if necessary, have equipment cooling and heating devices. 
Rice. 12. Minimum distances from live parts to transported equipment 
Rice. 13. Minimum distances between conductors of different circuits in outdoor switchgear
In Fig. Figure 18 shows a section of a KRUN cabinet with an air inlet. The interior of the cabinet is divided by solid metal partitions into five compartments: busbars 3, upper detachable power contacts 11, current transformers and lower power contacts 9, retractable trolley 7, relay protection and measuring instruments 4. The air input is connected to bushings 1, to which inside The cabinet is connected to a rigid busbar connecting insulators 1 to current transformers 10 (on phases A and C) and the lower power contact 8 (on phase B); on phases A and C, the contacts are connected to current transformers 20. The upper power contacts 12 are connected to buses 2 busbar through bushings connecting electrically compartments 11 and 3. 
Rice. 18. KRUN cabinet with air inlets
In compartment 4 there is a folding sheet of devices 5. Plug connector 6 ensures the opening of low-voltage circuits when the trolley with a high-voltage switch is rolled out. The trolley can only be rolled out when the switch is turned off. After the trolley is rolled out (in Fig. 18 it is pulled out of the cabinet), special curtains automatically close the upper and lower openings for the passage of movable and main contacts. The use of KRUN allows the construction of 6 and 10 kV switchgear without a building, which significantly reduces the cost of construction and operation of electrical installations.
The most common electrical installations in urban electrical networks are a distribution point (DP) and a transformer substation (TS).
The figure below shows a complete circuit diagram of the RP, where one or more connections are supply (through which electricity is supplied from the power center), and the rest are distribution. The distribution point is a distribution device consisting of several sections of busbars 7, chambers for equipment I - XX, a control corridor and a room for installing protection devices, automation and telemechanics.
1 and 4 - linear and busbar disconnectors with grounding blades,
2 - current transformers, 3 - line switches,
5 — voltage transformer, 6 — PKT fuses,
7 - busbars, 8 - sectional switch,
9 - bus grounding disconnectors, 10 - ammeters,
11 - voltmeters, 12 - relays (V - time, T - current, U - index);
1—ХХ — camera numbers
Busbars are placed in the upper part of the distribution center horizontally at a distance of at least 500 mm from the ceiling. The distance between busbars of different phases must be at least 100 mm at a voltage of 6 kV and 130 mm at 10 kV. The busbars are attached to support insulators mounted on metal structures or concrete walls. The RP bus sections are separated by a sectional switch 8; each section has grounding disconnectors 9 for grounding when performing repair work.
Chambers in distribution centers, depending on the type of equipment installed in them, are divided into chambers of switches, measuring voltage transformers, arresters, grounding disconnectors
The picture shows RP scheme for twenty cameras, of which fourteen are for linear switches, two for a sectional switch, two for a voltage transformer and for busbar grounding disconnectors. The switch chambers contain line disconnectors 1 with grounding blades, current transformers 2, switches 3, busbar disconnectors 4 with grounding blades. In the voltage transformer chamber there is a voltage transformer 5 (one or more), a fuse 6 and busbar disconnectors with grounding blades, and grounding busbar disconnectors 9 are also installed.
To prevent erroneous operations with disconnectors, there is a lock in the switch chambers that allows the disconnectors to be turned off only when the switch is turned off. Typically a mechanical lever lock is used.
When the switch is turned on, the system of levers locks the locking plates of the disconnector drives; when the switch is turned off, the locking plates are lowered and release the locks of the disconnector drives. IN chambers with grounding disconnectors There is an additional mechanical interlock that does not allow the grounding switches to be turned on when the busbar or line disconnector is switched on and, conversely, the busbar or line switch is switched on when the grounding switches are switched on.
The RP control corridor is a room where drives for switches and disconnectors are installed. Its width for a single-row arrangement of cells must be at least 1500 mm and for a double-row arrangement - at least 2000 mm. If the length is more than 7 m, it must have two outlets.
IN distribution point There are also measuring instruments, protection and automation relays, a grounding device and a telemechanics device.
Minimum clear distance between the busbars of the secondary current supply*
|
The room in which the conductor is laid |
Distance, mm, depending on the type of current, frequency and voltage of the conductors |
||||||
|
Constant |
Variable |
||||||
|
above 10000 Hz |
|||||||
|
above 1 to 3 kV |
above 1.6 to 3 kV | ||||||
|
Dry, dust-free | |||||||
|
Dry dusty** | |||||||
*For tire heights up to 250 mm; at a higher height, the distance should be increased by 5-10 mm.
**Dust is non-conductive.
7.5.28. Sewerage of water cooling equipment, apparatus and other elements of electrothermal installations must be carried out taking into account the possibility of monitoring the condition of the cooling system.
It is recommended to install the following relays: pressure, jet and temperature (the last two - at the outlet of water from the elements cooled by it) with their operation on a signal. In cases where stopping the flow or overheating of the cooling water can lead to emergency damage, automatic shutdown of the installation must be ensured.
The water cooling system - open (from the water supply network or from the enterprise's recycling water supply network) or closed (double-circuit with heat exchangers), individual or group - must be selected taking into account the water quality requirements specified in the standards or technical specifications for electrothermal installation equipment. When choosing a system, one should proceed from the specific conditions of the water supply of the enterprise (workshop, building) and the most economically feasible option, determined by the minimum given costs.
Water-cooled elements of electrothermal installations with an open cooling system must be designed for a maximum water pressure of 0.6 MPa (6 kgf/cm) and a minimum of 0.2 MPa (2 kgf/cm) with water quality, as a rule, meeting the requirements of Table. 7.5.13, unless other standard values are given in the standards or technical specifications for the equipment.
Table 7.5.13
Characteristics of water for cooling elements of electrothermal installations
|
Index |
Type of water supply network |
|
|
Domestic drinking water supply |
Enterprise water supply network |
|
|
Hardness, mEq/l, not more than: | ||
|
carbonate | ||
|
suspended solids (turbidity) | ||
|
active chlorine | ||
|
Temperature, °C, no more | ||
In electrothermal installations that use water from the recycling water supply network to cool the elements, it is recommended to provide mechanical filters to reduce the content of suspended particles in the water.
When choosing an individual closed water cooling system, it is recommended to provide a secondary water circulation circuit without a backup pump, so that if the operating pump fails, water from the water supply network is used for the time required for an emergency shutdown of the equipment.
When using a group closed water cooling system, it is recommended to install one or two backup pumps with automatic switching on of the reserve.
7.5.29. When cooling elements of an electrothermal installation that may be energized with water through a flow or circulation system, insulating hoses (sleeves) must be provided to prevent the removal of potential through pipelines that is dangerous for operating personnel. If there is no fence, then the supply and drain ends of the hose must have grounded metal pipes to prevent personnel from touching them when the unit is turned on.
The length of insulating water cooling hoses connecting elements of different polarities must be no less than specified in the technical documentation of the equipment manufacturers; in the absence of such data, the length is recommended to be taken equal to: at a rated voltage of up to 1 kV, at least 1.5 m with an internal diameter of hoses up to 25 mm and 2.5 m with a diameter of 25 and up to 50 mm, with a rated voltage above 1 kV - 2 .5 and 4 m respectively.
The length of the hoses is not standardized if there is a gap between the hose and the waste pipe and the stream of water falls freely into the funnel.
7.5.30. Electrothermal installations, the equipment of which requires operational maintenance at a height of 2 m or more from the floor level of the room, must be equipped with working platforms, fenced with railings, with permanent stairs. The use of movable (for example, telescopic) ladders is not permitted. In an area where personnel may touch live parts of the equipment, platforms, fences and stairs must be made of non-combustible materials, the flooring of the working platform must be covered with a flame retardant dielectric material.
7.5.31. Pump-battery and oil-pressure installations of hydraulic drive systems of electrothermal equipment containing 60 kg of oil or more must be located in rooms where emergency oil removal is ensured.
7.5.32. Vessels used in electrothermal installations operating under pressure above 70 kPa (0.7 kgf/cm), devices using compressed gases, as well as compressor units must meet the requirements of current rules approved by the State Technical Supervision Authority of Russia.
7.5.33. Gases from the exhaust of preliminary vacuum pumps, as a rule, must be removed outside; the release of these gases into production and other similar premises is not recommended.
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