Switchgear (RU) called an electrical installation that serves to receive and distribute electricity and contains switching devices, prefabricated and connecting buses, auxiliary devices (compressor, battery, etc.), as well as protection devices, automation and measuring instruments.
Switchgears of electrical installations are designed to receive and distribute electricity of one voltage for further transmission to consumers, as well as to power equipment within the electrical installation.
If all or the main equipment of the switchgear is located outdoors, it is called open (ORU): if it is located in a building - closed (ZRU). A switchgear consisting of fully or partially enclosed cabinets and blocks with built-in devices, protection and automation devices, supplied assembled or fully prepared for assembly, is called complete and is designated for indoor installation of KRU, for outdoor - KRUN.
Power center - a generator voltage switchgear or a secondary voltage switchgear of a step-down substation, to which the distribution networks of the area are connected.
Switchgears (RU) are classified according to several criteria, below we give their types and design features.
Switchgears up to 1000 V
Distribution devices up to 1000 V are usually carried out indoors in special cabinets (shields). Depending on the purpose, 220/380 V switchgears (voltage class 0.4 kV) can be made to supply consumers or exclusively for the own needs of an electrical installation.
Structurally switchgears 0.4 kV have protective devices (automatic switches, fuses), knife switches, switch-disconnectors and busbars connecting them, as well as terminal blocks for connecting cable lines of consumers.
In addition to power circuits, a number of additional devices and auxiliary circuits can be installed in low-voltage switchboards, namely:
electricity meters and current transformers;
circuits for indicating and signaling the position of switching devices;
measuring instruments for monitoring voltage and current at various points of the switchgear;
alarm and ground fault protection devices (for IT configuration networks);
automatic transfer devices;
remote control circuits for switching devices with motor drives.
Low-voltage switchgears also include DC shields that distribute DC from converters, batteries to power the operational circuits of electrical equipment and relay protection and automation devices.
High voltage switchgears
Switchgears of voltage class above 1000 V can be designed as outdoors - open type (ORU), as well as indoors - closed type (ZRU).
In closed switchgear equipment is placed in prefabricated chambers of unilateral maintenance of KSO either in complete switchgears of KRU type.
Cameras of the KSO type are more preferable for rooms with a limited area, since they can be installed close to the wall or to each other with back walls. KSO chambers have several compartments closed with mesh fences or solid doors.
KSO are equipped with various equipment, depending on their purpose. To power the outgoing lines, a high-voltage circuit breaker, two disconnectors (on the busbar side and on the line side), current transformers are installed in the chamber, on the front side there are disconnector control levers, a circuit breaker drive, as well as low-voltage circuits and protection devices implemented to protect and control this line.
Chambers of this type can be equipped with voltage transformers, arresters (overvoltage limiters), fuses.
KRU switchgears are a cabinet divided into several compartments: current transformers and outgoing cable, busbars, withdrawable part and compartment of secondary circuits.
Each compartment is isolated from each other to ensure safety during maintenance and operation of switchgear cabinet equipment. The withdrawable part of the cabinet, depending on the purpose of the connection, can be equipped with a circuit breaker, voltage transformer, arresters (OPN), auxiliary transformer.
The retractable element relative to the cabinet body can occupy a working, control (uncoupled) or repair position. In the working position, the main and auxiliary circuits are closed, in the control position, the main circuits are open, and the auxiliary circuits are closed (in the disconnected position, the latter are open), in the repair position, the drawer is located outside the cabinet body and its main and auxiliary circuits are open. The force required to move the sliding element must not exceed 490 N (50 kG). When the sliding element is rolled out, the openings to the fixed detachable contacts of the main circuit are automatically closed with curtains.
The current-carrying parts of the switchgear are made, as a rule, with tires made of aluminum or its alloys; at high currents it is allowed to use copper tires, at rated currents up to 200 A - steel. Auxiliary circuits are mounted with insulated copper wire with a cross section of at least 1.5 sq. mm, connection to the meters - with a wire with a cross section of 2.5 sq. mm, soldered joints - not less than 0.5 sq. mm. Connections subject to bending and torsion are usually made with stranded wires.
Flexible connection of the auxiliary circuits of the stationary part of the switchgear with the withdrawable element is carried out using plug connectors.
Switchgear cabinets, as well as grounding knives, must meet the requirements for electrodynamic and thermal resistance to through short-circuit currents. To ensure the requirements for mechanical resistance, the number of cycles that the switchgear cabinets and its elements must withstand is regulated: detachable contacts of the main and auxiliary circuits, a withdrawable element, doors, and an earthing switch. The number of cycles of switching on and off the built-in accessory equipment (switches, disconnectors, etc.) is taken in accordance with the PUE.
To ensure safety, switchgear cabinets are equipped with a number of interlocks. After the sliding element is rolled out, all current-carrying parts of the main circuits that may be energized are closed with protective shutters. These curtains and guards must not be removed or opened without the aid of keys or special tools.
In stationary design switchgear cabinets, it is possible to install stationary or inventory partitions to separate live equipment parts. It is not allowed to use bolts, screws, studs that act as fasteners for grounding. In places of grounding there should be an inscription "earth" or a sign of grounding.
The type of the switchgear cabinet is determined by the diagram of the main circuit of the switchgear. The main electrical device that determines the design of the cabinet is a switch: low-oil, electromagnetic, vacuum and gas-insulated switches are used. Schemes of secondary circuits are extremely diverse and have not yet been completely unified.
Complete devices can have a different design, for example, with SF6 insulation - KRUE or intended for outdoor installation - KRUN that can be installed outdoors.
Open-type switchgears provide for the installation of electrical equipment on metal structures, on concrete foundations, without additional protection from external influences. Auxiliary circuits of outdoor switchgear equipment are mounted in special cabinets that are protected from mechanical stress and moisture.
Switchgears, both closed and open types, are classified according to several criteria, depending on their design (circuit).
The first criterion is how partitioning is performed. A distinction is made between switchgear with busbar sections and busbar systems. Bus sections provide power for each individual consumer from one section, and bus systems allow switching one consumer between several sections. Bus sections are connected by section switches, and bus systems are connected by bus connectors. These switches allow sections (systems) to be powered from each other in case of power loss in one of the sections (systems).
The second criterion is the presence of bypass devices- one or more bypass busbar systems, which allow items of equipment to be taken out for repair without the need to de-energize consumers.
The third criterion is the power supply circuit of the equipment (for open switchgear). In this case, two variants of the scheme are possible - radial and ring. The first scheme is simplified and provides power supply to consumers through one switch and disconnectors from busbars. With a ring circuit, each consumer is powered by two or three switches. The ring scheme is more reliable and practical in terms of maintenance and operation of equipment.
4.1.24. Switchgears installed in rooms accessible to uninstructed personnel must have live parts closed with solid fences.
In the case of using a switchgear with open current-carrying parts, it must be fenced. In this case, the fence must be mesh, solid or mixed with a height of at least 1.7 m. The distance from the mesh fence to non-insulated current-carrying parts of the device must be at least 0.7 m, and from solid - in accordance with 4.1.14. The width of the aisles is taken in accordance with the requirements given in 4.1.21.
4.1.25. The termination of wires and cables must be made so that it is inside the device.
4.1.26. Removable guards must be reinforced so that their removal is impossible without the use of a tool. Doors must be locked with a key.
4.1.27. Installation of complete switchgears and substations (KRU, KTP) must comply with the requirements given in Ch. 4.2 for KRU and PTS above 1 kV.
Outdoor switchgear installation
4.1.28. When installing switchgears outdoors, the following requirements must be observed:
1. The device must be located on a planned site at a height of at least 0.2 m from the planning level and must have a design that meets environmental conditions. In areas where snowdrifts of 1 m or more are observed, cabinets should be installed on elevated foundations.
2. Local heating must be provided in the cabinets to ensure the normal operation of devices, relays, measuring instruments and metering devices in accordance with the requirements of GOST.
Chapter 4.2
Switchgears and substations
Voltage above 1 kV
Scope, definitions
4.2.1. This chapter of the Rules applies to stationary switchgear and substations of alternating current with a voltage above 1 kV. The rules do not apply to special switchgears and substations regulated by special technical conditions, and to mobile electrical installations.
4.2.2. A switchgear is an electrical installation that serves to receive and distribute electricity and contains switching devices, prefabricated and connecting buses, auxiliary devices (compressor, battery, etc.), as well as protection devices, automation and measuring instruments.
An open switchgear (ORU) is a switchgear, all or the main equipment of which is located in the open air.
A closed switchgear (ZRU) is a switchgear, the equipment of which is located in the building.
4.2.3. A complete switchgear is a switchgear, consisting of fully or partially closed cabinets or blocks with built-in devices, protection and automation devices, supplied assembled or fully prepared for assembly.
A complete switchgear intended for indoor installation is abbreviated as KRU. A complete switchgear designed for outdoor installation is abbreviated as KRUN.
4.2.4. A substation is an electrical installation that serves to convert and distribute electricity and consists of transformers or other energy converters, switchgears, control devices and auxiliary structures.
Depending on the predominance of one or another function of substations, they are called transformer or converter.
4.2.5. An attached substation (attached switchgear) is a substation (RU) that is directly adjacent (adjacent) to the main building.
4.2.6. A built-in substation (built-in switchgear) is a closed substation (closed switchgear) inscribed (inscribed) in the contour of the main building.
4.2.7. An intrashop substation is a substation located inside the production building (open or in a separate closed room).
4.2.8. A complete transformer (converting) substation is a substation consisting of transformers (converters) and blocks (KRU or KRUN and other elements) supplied assembled or fully prepared for assembly. Complete transformer (converting) substations (KTP, KPP) or parts of them, installed indoors, refer to indoor installations, installed outdoors - to outdoor installations.
4.2.9. A pole (mast) transformer substation is an open transformer substation, all the equipment of which is installed on structures or on overhead line supports at a height that does not require substation fencing.
4.2.10. A distribution point (DP) is a switchgear designed to receive and distribute electricity at one voltage without conversion and transformation, which is not part of a substation.
4.2.11. A chamber is a room intended for the installation of devices and tires.
A closed chamber is a chamber that is closed on all sides and has solid (not mesh) doors.
A fenced chamber is a chamber that has openings protected in whole or in part by non-continuous (mesh or mixed) fences.
Mixed fences are fences made of nets and solid sheets.
An explosion chamber is a closed chamber designed to localize possible emergency consequences in case of damage to the devices installed in it and having an exit to the outside or into the explosive corridor.
4.2.12. A service corridor is a corridor along the chambers or switchgear cabinets intended for servicing devices and tires.
The explosive corridor is the corridor into which the doors of the explosive chambers open.
Switchgears of substations with a voltage of 35–110 kV, as
as a rule, are performed open (ORU). They must ensure the reliability of operation, safety and ease of maintenance of equipment with minimal construction costs. Transformers are installed in open switchgears, switching, protective and control devices are used in accordance with the scheme. Switches, disconnectors, current and voltage transformers, arresters can be used in outdoor switchgear. In order to reduce the cost of outdoor switchgear at most substations of enterprises, switches are replaced by short-circuiters and separators. All outdoor switchgear devices are located on low metal or reinforced concrete bases. Transformers are installed on concrete or asphalt sites, on foundations. The sites are prepared with a slope away from the closed switchgear (ZRU) for water drainage and covered with a layer of gravel or shell rock to ensure water filtration and vegetation prevention. Under transformers and devices with transformer oil, oil receivers are provided with a bottom slope towards the oil sump. A layer of gravel with a thickness of at least 25 cm is laid.
The area of the gravel cover must not be less than the area of the transformer or apparatus.
Bases for apparatuses and foundations for supporting structures rise above the level of gravel filling by at least 20 cm. The main building structures are U- or T-shaped metal or reinforced concrete supporting structures.
Substations are powered by double-circuit or two radial lines. Feed lines approach portals. Support structures for fastening current conductors rely on one-sided tension of the wires from wind and ice.
The busbar in the switchgear can be flexible from stranded wires or
rigid from tires of various sections and configurations. Flexible busbars are attached using suspension insulators, and rigid busbars are mounted on support insulators. When designing and constructing a substation, all equipment must
be located so that during the installation, maintenance and repair of equipment it was possible to use lifting mechanisms, the passage of vehicles was provided for the delivery of equipment and its removal, if necessary, for repair. At powerful substations, a closed platform for inspection and repair of transformers can be provided.
Lightning protection devices, lightning rods and arresters are installed in the outdoor switchgear. All substation equipment must be grounded.
Cables for control circuits and control of switching devices
are laid in trays along structural and supporting elements. outdoor switchgear
must have a fence.
In accordance with the requirements of the Electrical Installation Code, the distances between current-carrying
parts and from them to various devices are selected, as indicated in Table. 9.1.
Table 9.1
Rice. 9.3. Scheme of primary connections of a dead-end single-transformer substation KTP 35/10 kV with a capacity of 630 - 1000 kVA: Q1 -
Q3 - switches; QS, QS1 - QS6 - disconnectors; FU, FU1 - fuses; FV, FV2 - arresters; T - transformer; T1 -
auxiliary transformer; TA1 - TA3 - transformers
current; TV - voltage transformer
Transformers and devices are fenced if the height from the insulator to the planning level is less than 2.5 m. The fence can be mesh up to 2 m high or in the form of barriers 1.2 m high. The distance between the transformers depends on their power and must be at least 1.25 m, and between the transformer and the refractory wall of the ZRU building - at least 0.8 m.
On fig. 9.3 shows the diagram of the primary connections of a single-transformer packaged transformer substation KTP 35/10 kV with an outdoor switchgear and a closed outdoor switchgear (KRUN).
On fig. 9.4 - its design.
Switchgear (RU) - this is an electrical installation designed to receive and distribute electrical energy, containing electrical apparatus, tires and auxiliary devices. Power stations, step-down and step-up substations, usually have several switchgears of different voltages (RU VN, RU SN, RU NN).
Essentially, RU this is a constructive implementation of the adopted electrical circuit of the substation, i.e. arrangement of electrical devices indoors or outdoors with connections between them with bare (rarely insulated) tires or wires strictly in accordance with the electrical circuit.
For the energy system, the switchgear is a network node equipped with electrical devices and protective devices that serve to control the distribution of energy flows, disconnect damaged sections, and ensure reliable power supply to consumers.
Each switchgear consists of suitable and outgoing connections, which are interconnected by busbars, jumpers, ring and polygonal connections, with the placement of a different number of switches, disconnectors, reactors, instrument transformers and other electrical devices, due to the adopted scheme. All similar connections are made in the same way, so that the switchgear is assembled from standard, as it were, typical cells.
The switchgear must meet certain requirements, the most important of which are: reliability of operation, convenience and safety of maintenance with minimal construction costs, fire safety and operational efficiency, the possibility of expansion, the maximum use of large-block prefabricated units.
The reliability of the switchgear operation is ensured by the correct choice and correct installation of electrical equipment (electrical apparatus, current-carrying parts and insulators), as well as good localization of accidents with electrical equipment in case of their occurrence. In addition, the reliability of the operation of the switchgear to a greater extent depends on the quality of construction and electrical installation work.
Switchgears are made for all applied voltages. By analogy with devices, they are divided into switchgear up to 1000 kV, high voltage switchgear from 3 to 220 kV, ultra-high voltage switchgear: 330, 500, 750 kV and advanced ultra-high voltage switchgear of 1150 kV and above.
By design, switchgears are divided into closed (internal), in which all electrical equipment is located inside the building, and open (outdoor), in which all electrical equipment is located in the open air.
Rice. 2.1. GRU 6 - 10 kV with one busbar system and group reactors (section of the generator and group reactor circuits) 1 - current transformer, 2 - bushing, 3 - generator circuit breaker chamber, 4 - circuit breaker drive, 5 - busbar block, 6 - busbar disconnector block, 7 - busbar disconnector drive, 8 - double reactor chamber, 9 - busbar, 10 - KRU cells
Closed switchgear (ZRU) is a switchgear located inside the building. Usually they are built at a voltage of 3 - 20 kV. In high voltage installations, 35 - 220 kV, indoor switchgears are built only with a limited area under the switchgear, when they are located in close proximity to industrial enterprises that pollute the air with conductive dust or gases that destroy insulation and metal parts of electrical equipment, as well as near sea coasts and in areas with very low air temperatures (regions of the Far North).
Maintenance of ZRU should be convenient and safe. For safety, the minimum allowable distances from current-carrying parts to various elements of the switchgear are observed
Uninsulated current-carrying parts, in order to avoid accidental contact with them, must be placed in chambers or fenced. The fence can be solid or mesh. Many indoor switchgear use mixed fencing - the drives of switches and disconnectors are mounted on the solid part of the fencing, and the mesh part of the fencing allows you to monitor the equipment. The height of such a fence must be at least 1.9 m, while the nets must have holes no larger than 25 × 25 mm, and the fences must be locked.
From the switchgear premises, exits to the outside or to premises with fireproof walls and ceilings are provided: one exit with a switchgear length of up to 7 m; two exits at the ends with a length of 7÷60 m; with a length of more than 60 m - two exits at the ends and additional exits so that the distance from any point of the corridor to the exit does not exceed 30 m. The switchgear doors must open outward, have self-locking locks and open without a key from the switchgear side.
ZRU must ensure fire safety. When oil transformers are installed in switchgear, measures are provided for collecting and draining oil into the oil collecting system. The closed switchgear provides for natural ventilation of transformer and reactor rooms, as well as emergency exhaust of service corridors for open chambers with oil-filled equipment.
Prefabricated switchgear (SBRU) mounted from enlarged units (cabinets, panels, etc.) manufactured and completed at factories or workshops. In the SBRU, the building is constructed in the form of a box, without any partitions, of a hall type. The basis of the chambers is a steel frame, and the partitions between the chambers are made of asbestos-cement or gypsum boards.
Rice. 2.2. ZRU 110 kV of the hall type (section of the air circuit breaker cell)1 - VNV-110 kV circuit breaker, 2 - first bus system, 3 - bus disconnectors, 4 - second bus system, 5 - bypass bus system, 6 - bypass disconnector, 7 - coupling capacitor, 8 - line disconnector.
Complete switchgear (KRU) - this switchgear is completely manufactured in factories, consisting of closed cabinets with built-in devices, measuring and protective devices and auxiliary devices; in place, all elements of the switchgear are only mounted. These switchgears are the most suitable for the industrialization of power construction, so they are becoming the most common form of switchgear at present. The use of KRU allows you to speed up the installation of the switchgear. The switchgear is safe to maintain, since all live parts are covered with a metal casing. Air, oil, pyralene, solid insulation, inert gases can be used as insulation between current-carrying parts in switchgear. Switchgear with oil and gas insulation can be manufactured for high voltages of 220 - 500 kV. Our industry produces switchgear 3 - 35 kV with air insulation and 110 - 220 kV with SF6 insulation (in world practice up to 800 kV). Complete switchgears for outdoor installation (KRUN) are designed for open installation outsidepremises. KRUN consist of metal cabinets with devices, instruments, protection and control devices built into them. KRUN are designed for operation at ambient temperatures from -40 to +35 °С and air humidity not more than 80%. KRUN can have a stationary installation of a circuit breaker in a cabinet or a roll-out trolley with a circuit breaker, similar to indoor KRU.
Cabinets KRZ-10 (Fig. 2.3) for outdoor installation 6 - 10 kV are designed for networks of agriculture, industry and electrification of railway transport. Cases KRZ-10 are designed for ambient temperature from +50 to -45°С.
At the same time, mixed-type switchgears are also being widely constructed, partly as prefabricated and partly as complete.
Rice. 2. 4. Typical layout of outdoor switchgear 110 - 220 kV for a circuit with two working and bypass bus systems
1 - bypass SL, 2 - SSH disconnector, 3 - coupling capacitor, 4 - barrier, 5 - line disconnector, 6 - current transformer, 7 - air circuit breaker, 8 - second SL, 9 - keel-mounted busbar disconnectors, 10 - busbar disconnectors , 11 – the first SS.
Open switchgear (OSG)- This is a switchgear located in the open air. As a rule, switchgears in electrical installations with a voltage of 35 and above are built open. The simplest open substations of small power with a primary voltage of 10 (6) -35 kV are also widespread for the electrification of agricultural and suburban areas, industrial settlements and small towns.
All devices in the outdoor switchgear are made on low bases (metal or reinforced concrete). Across the territory of the outdoor switchgear, driveways are made for the possibility of mechanizing the installation and repair of equipment. Busbars can be flexible from stranded wires or from rigid pipes. Flexible busbars are mounted with suspension insulators on portals, and rigid busbars with support insulators on reinforced concrete or metal racks.
The use of a rigid busbar makes it possible to refuse portals and reduce the area of the outdoor switchgear.
Under power transformers, oil reactors and tank circuit breakers of 110 kV and above, an oil receiver is provided, a layer of gravel with a thickness of at least 25 cm is laid, and the oil drains into underground oil collectors in emergency cases. Cables for operational circuits, control circuits, relay protection, automation and air ducts are laid in trays made of reinforced concrete structures without being buried in the soil or in metal trays suspended from outdoor switchgear structures.
The switchgear must be fenced.
Advantages of outdoor switchgear compared to closed switchgear
1) a smaller volume of construction work; so only the preparation of the site, the construction of roads, the construction of foundations and the installation of supports are necessary;
2) significant savings in building materials (steel, concrete);
3) lower capital costs;
4) shorter construction time;
5) good visibility;
6) ease of expansion and ease of replacement of equipment with others with smaller or larger dimensions, as well as the ability to quickly dismantle old and install new equipment.
7) less risk of damage spreading due to large distances between devices of adjacent circuits;
Disadvantages of outdoor switchgear compared to indoor switchgear
1) less convenient maintenance, since the switching of the disconnectors and the observation of the devices are carried out in the air in any weather (low temperatures, bad weather);
2) a large area of the structure;
3) exposure of devices to a sharp change in ambient temperature, their exposure to pollution, dust, etc., which complicates their operation and forces the use of devices of a special design (for outdoor installation), more expensive.
The cost of ZRU is usually 10 - 25% higher than the cost of the corresponding outdoor switchgear.
At present, in most cases, outdoor switchgear of the so-called low type is used, in which all devices are located in the same horizontal plane and are installed on special bases of relatively low height; busbars are also fixed on supports of relatively small height.
Lecture No. 6 "Distribution devices and substations"
Requirements for buildings and structures of switchgears.
Doors and windows in the switchgear rooms must always be closed, and the openings in the partitions between the devices containing oil must be sealed. All openings in the places where the cable passes are sealed. To prevent the entry of animals and birds, all openings and openings in the outer walls of the premises are sealed or closed with meshes with a mesh size (1x1) cm. Current-carrying parts of ballasts and protection devices must be protected from accidental touches. In special rooms (electrical machines, switchboards, control stations, etc.), open installation of devices without protective covers is allowed. All switchgear (shields, assemblies, etc.) installed outside the outdoor switchgear enclosures and enclosed spaces must have locking devices that prevent non-electrotechnical personnel from accessing them. The electrical equipment of the switchgear of all types and voltages must satisfy the operating conditions, both under normal conditions and during short circuits, overvoltages and overloads. The insulation class of electrical equipment must correspond to the rated voltage of the network, and surge protection devices - to the insulation level of electrical equipment. When electrical equipment is located in an area with a polluted atmosphere, measures must be taken to ensure the reliability of the insulation:
Heating by induced current of structures located near current-carrying parts through which current flows and accessible for personnel to touch, should not exceed 50 ° C. The air temperature inside the indoor switchgear in the summer should not exceed 40°C. If it rises, measures must be taken to reduce the temperature of the equipment or cool the air. The air temperature in the compressor station room must be maintained within (10 ¸ 35) ° С; in the room of gas-insulated switchgears (hereinafter - KRUE) - within (1 ¸ 40) ° С. The temperature of the busbar connectors in the switchgear should be controlled according to the approved schedule. The distances from the current-carrying parts of the outdoor switchgear to trees, tall shrubs should be such that the possibility of overlapping is excluded. The floor covering in ZRU, KRU and KRUN should be such that there is no formation of cement dust. The premises intended for the installation of cells of a complete switchgear with SF6 insulation (hereinafter referred to as GIS), as well as for their revision before installation and repair, must be isolated from the street and other premises. Walls, floors and ceilings must be painted with dust-proof paint. Rooms must be cleaned by wet or vacuum cleaning. The premises must be equipped with supply and exhaust ventilation with air suction from below. Air supply ventilation must pass through filters that prevent dust from entering the room.
In this lecture, we will consider consumer substations with voltages from 0.4 to 220 kV. The room of the consumer's switchgear, adjacent to the premises belonging to third-party organizations, and having energized equipment, must be isolated from them. It must have a separate lockable exit. The switchgear equipment serviced by the Consumers and used by the power supply organization must be controlled on the basis of the instructions agreed by the Consumer and the power supply organization. Doors and windows in the switchgear rooms must always be closed, and the openings in the partitions between the devices containing oil must be sealed. All openings in the places where the cable passes are sealed. To prevent the entry of animals and birds, all openings and openings in the outer walls of the premises are sealed or closed with meshes with a mesh size (1x1) cm. Current-carrying parts of ballasts and protection devices must be protected from accidental touches. In special rooms (electrical machines, switchboards, control stations, etc.), open installation of devices without protective covers is allowed. All switchgear (shields, assemblies, etc.) installed outside the outdoor switchgear enclosures and enclosed spaces must have locking devices that prevent non-electrotechnical personnel from accessing them. The electrical equipment of the switchgear of all types and voltages must satisfy the operating conditions, both under normal conditions and during short circuits, overvoltages and overloads. The insulation class of electrical equipment must correspond to the rated voltage of the network, and surge protection devices - to the insulation level of electrical equipment. When electrical equipment is located in an area with a polluted atmosphere, measures must be taken to ensure the reliability of the insulation:
In open switchgears (hereinafter referred to as outdoor switchgear) - strengthening, washing, cleaning, coating with hydrophobic pastes;
In closed switchgears (hereinafter - ZRU) - protection against the ingress of dust and harmful gases;
In complete switchgears for outdoor installation - sealing of cabinets and treatment of insulation with hydrophobic pastes.
Heating by induced current of structures located near current-carrying parts through which current flows and accessible for personnel to touch, should not exceed 50 ° C. The air temperature inside the indoor switchgear in the summer should not exceed 40°C. If it rises, measures must be taken to reduce the temperature of the equipment or cool the air. The air temperature in the compressor station room must be maintained within (10 ¸ 35) ° С; in the room of gas-insulated switchgears (hereinafter - KRUE) - within (1 ¸ 40) ° С. The temperature of the busbar connectors in the switchgear should be controlled according to the approved schedule. The distances from the current-carrying parts of the outdoor switchgear to trees, tall shrubs should be such that the possibility of overlapping is excluded. The floor covering in ZRU, KRU and KRUN should be such that there is no formation of cement dust. The premises intended for the installation of cells of a complete switchgear with SF6 insulation (hereinafter referred to as GIS), as well as for their revision before installation and repair, must be isolated from the street and other premises. Walls, floor and ceiling must be painted with dustproof paint.
Cleaning of premises should be carried out by wet or vacuum method. The premises must be equipped with supply and exhaust ventilation with air suction from below. Air supply ventilation must pass through filters that prevent dust from entering the room.
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