Open switchgear (OSD) - distribution
a device whose equipment is located outdoors. All
outdoor switchgear elements are placed on concrete or metal bases.
The distances between elements are selected according to the PUE. At voltages of 110 kV and above under devices that use oil for operation
(oil transformers, switches, reactors) oil receivers are created - recesses filled with gravel. This measure is aimed at reducing the likelihood of a fire and reducing damage during
accidents on such devices. Outdoor switchgear busbars can be made both in the form of rigid pipes and in the form flexible wires. Rigid pipes are mounted on racks using support insulators, and flexible pipes are suspended on portals using hanging insulators. The territory on which the outdoor switchgear is located must be fenced.
Advantages of outdoor switchgear:
Outdoor switchgear allows you to use arbitrarily large electric
devices, which, in fact, determines their use on high classes stress.
When producing outdoor switchgear, no extra construction costs are required
premises.
Open switchgears are more practical than closed switchgear in terms of modernization and expansion
Visual inspection of all outdoor switchgear devices
Disadvantages of outdoor switchgear:
Difficulty working with outdoor switchgear under adverse weather conditions.
The outdoor switchgear is much larger than the indoor switchgear.
As conductors for outdoor switchgear busbars and branches from them
stranded wires of grades A and AC are used, as well as rigid
tubular tires. At voltages of 220 kV and above, splitting is required
wires to reduce corona losses.
The length and width of the outdoor switchgear depends on the selected station layout, location
switches (single-row, double-row, etc.) and power lines. In addition, access roads for automobile or
railway transport. The outdoor switchgear must have a fence at least 2.4 m high. In the outdoor switchgear, live parts of devices, busbar conductors and
To avoid intersections, branches from busbars are placed on
different heights in two and three tiers. For flexible wires, busbars
placed in the second tier, and the branch wires in the third.
Minimum distance from the first tier conductors to the ground for 110 kV
3600 mm, 220 kV - 4500 mm. Minimum distance vertically between
wires of the first and second tiers, taking into account the sag of the wires for 110 kV - 1000 mm, for 220 kV - 2000 mm. The minimum distance between the wires of the second and third tiers for 110 kV is 1650 mm, for 220 kV - 3000 mm.
Minimum permissible insulating distances (in centimeters) in the clear
in the air of open installations between bare wires of different
phases, between live parts or insulation elements located
energized and grounded parts of structures:
Complete switchgear with gas insulation
(GIS)
Complete gas-insulated switchgear consists of cells whose space is filled with SF6 gas under pressure, connected in various circuits distribution devices according to technical design standards. GIS cells are made from standardized parts, which makes it possible to assemble cells for various purposes from the same elements. These include: poles of switches, disconnectors and grounding switches; measuring
current and voltage transformers; connecting and intermediate compartments; busbar sections; pole and distribution cabinets, pressure control system cabinets and voltage transformer cabinets. Each type of cell consists of three identical poles and control cabinets. Each pole of a linear, sectional or busbar connecting cell has a switch with a drive and its control elements, a disconnector with a remote electric drive, grounding switches with a manual drive,
current transformers and pole cabinets. Voltage transformer cells do not have switches or current transformers. Cells and their
The poles are connected by one or two single-pole or three-pole busbar systems.
Linear cells have terminals for connection to current conductors and
outgoing cables. The cells are connected to power cables using specially designed cable glands, and to overhead lines using gas-filled glands.
The safety and reliability of power supply depends on the switches,
protecting electrical networks from short circuits. Traditionally on
power plants and substations installed air circuit breakers
isolation. Depending on the rated voltage of the air
switch, the distance between live parts and ground may
be tens of meters, resulting in the installation of such a device
requires a lot of space. In contrast, the SF6 circuit breaker is very compact, and therefore the switchgear takes up a relatively small usable volume. The area of a substation with switchgear is ten times smaller than the area of a substation with air circuit breakers. The current conductor is an aluminum pipe in which the current-carrying busbar is installed, and is designed to connect individual cells and gas-insulated gas-insulated equipment of the substation. Also, current and voltage measuring transformers, voltage limiters (OSL), grounding switches and disconnectors are built into the switchgear cell.
Thus, the cell contains all the necessary equipment and
devices for transmission and distribution of electricity of various voltages. And all this is enclosed in a compact, reliable case. The cells are controlled in cabinets installed on the side walls.
The distribution cabinet contains all the equipment for remote electrical control, alarm and interlock circuits
elements of cells.
The use of switchgear can significantly reduce areas and volumes,
occupied by the switchgear and provide the possibility of easier expansion of switchgear compared to traditional switchgear. Other important advantages of GIS include:
Multifunctionality - busbars are combined in one housing,
switch, disconnectors with grounding disconnectors, current transformers, which significantly reduces the size and increases
reliability of outdoor switchgear;
Explosion and fire safety;
High reliability and resistance to environmental influences;
Possibility of installation in seismically active areas and areas with increased pollution;
Lack of electric and magnetic fields;
Safety and ease of use, ease of installation and dismantling.
Small dimensions
Resistance to pollution.
Cells, individual modules and elements allow switchgear switchgear to be configured according to various electrical circuits. The cells consist of three poles, cabinets and busbars. The cabinets contain equipment for alarm circuits, interlocks, remote electrical control, control of SF6 gas pressure and its supply to the cell, and power supply of drives with compressed air.
Cells on Rated voltage 110-220 kV have three-pole
or pole-pole control, and 500 kV cells - only pole-pole
control.
The cell pole includes:
Switching devices: switches, disconnectors, grounding switches;
Current and voltage measuring transformers;
Connecting elements: busbars, cable glands (“oil gas”), feedthroughs (“air-sulfur hexafluoride”), gas conductors and
The cost of switchgear is quite high compared to traditional types of switchgear, so it is used only in cases where its advantages are extremely necessary - this is during construction in cramped conditions, in urban environments to reduce noise levels and for architectural aesthetics, in places where it is technically impossible to place switchgear or closed switchgear, and in areas where the cost of land is very high, as well as in aggressive environments to protect live parts and increase the service life of equipment and in seismically active zones.
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Closed switchgear (SGD)
Closed switchgears and substations.
Closed switchgears are most often constructed up to 10 kV inclusive. If it is difficult to obtain the site necessary for placing an outdoor switchgear, when located at enterprises in cramped conditions, in areas with polluted air, which has a destructive effect on open live parts and reduces the insulating properties of porcelain, as well as in northern regions with very low temperatures and heavy snowfalls, they build ZRU 35 and 110 kV. In this case, the 110 kV closed switchgear is constructed using equipment intended for outdoor switchgear.
Closed reactor plants are located in one-, two-, or three-story buildings made of standardized prefabricated reinforced concrete structures. Closed 6 and 10 kV switchgear and substations are located in built-in, attached or free-standing buildings made of brick or precast reinforced concrete, built on foundations of reinforced concrete blocks.
Closed 35 and 110 kV switchgears are located in separate buildings made of precast reinforced concrete. The dimensions of the premises depend on the type of electrical equipment used, the layout of the main circuits, the filling pattern and the permissible dimensions of the width of corridors and passages in indoor switchgear, transformer chambers and switchboard rooms (Table 4). When laying out switchgear and substations, the current building standards and dimensions of typical precast concrete elements are taken into account: reinforced concrete slabs, beams, roofing and interfloor coverings.
When designing indoor switchgear and substations premises, the requirements of the electrical installation regulations are taken into account, the main ones of which are given below. The switchgear rooms are separated from other rooms by walls or partitions and ceilings. Switchgears above 1 and up to 1 kV are usually located separately. Depending on the length of the switchgear room, one (for a length of up to 7 m) or two exits (for a length of over 7 and up to 60 m) are installed, located at its ends (it is allowed to place exits from the switchgear at a distance of up to 7 m from its ends).
Doors from switchgear open in the direction of other rooms, outwards or towards switchgear with low voltage, and have self-locking locks that open with inside rooms without a key. The installation of thresholds in doors is not allowed.
Complete devices are most widely used during the installation of modern indoor switchgear and 6 and 10 kV substations. Complete switchgears are assembled from prefabricated one-way service chambers (KSO-272 and KSO-366) or cabinets KRU-2-6, KRU-2-10, KR-Yu/500, K-XII, K-XV. They are supplied according to custom designs with main circuit devices installed in chambers and cabinets, with protection, measurement, metering and alarm devices, with full busbar and secondary circuit wiring within the chambers.
Open switchgear (OSD)
Oil switch in outdoor switchgear
An open switchgear (OSD) is a switchgear whose equipment is located in the open air. All elements of the outdoor switchgear are placed on concrete or metal bases. The distances between elements are selected according to the PUE. At voltages of 110 kV and higher, oil receivers - gravel-filled recesses - are created under devices that use oil for operation (oil transformers, switches, reactors). This measure is aimed at reducing the likelihood of a fire and reducing damage in the event of an accident on such devices.
Outdoor switchgear busbars can be made both in the form of rigid pipes and in the form of flexible wires. Rigid pipes are mounted on racks using support insulators, and flexible pipes are suspended on portals using hanging insulators.
The territory on which the outdoor switchgear is located, in mandatory fenced off.
Advantages
§ Outdoor switchgear allows the use of arbitrarily large electrical devices, which, in fact, explains their use at high voltage classes.
§ Manufacturing outdoor switchgear does not require additional costs for the construction of premises.
§ Outdoor switchgear is more convenient than indoor switchgear in terms of expansion and modernization
§ Visual observation of all outdoor switchgear devices is possible
Flaws
§ Operation of outdoor switchgear is difficult in unfavorable conditions weather conditions In addition, the environment has a stronger impact on the outdoor switchgear elements, which leads to their early wear.
§ Outdoor switchgear takes up much more space than indoor switchgear.
Complete switchgear (KRU) - a switchgear assembled from standard unified blocks (so-called cells) high degree readiness, assembled in the factory. At voltages up to 35 kV, cells are manufactured in the form of cabinets connected by side walls in a common row. In such cabinets, elements with voltages up to 1 kV are made with wires in solid insulation, and elements from 1 to 35 kV are made with air-insulated conductors.
For voltages above 35 kV, air insulation is not applicable, therefore elements under high voltage are placed in sealed chambers filled with SF6 gas. Cells with SF6 chambers have complex design, externally similar to a network of pipelines. Gas-insulated switchgear is abbreviated as GIS.
Application area
Complete switchgears can be used for both internal and external outdoor installation(in this case they are called KRUN). Switchgear switchgear is widely used in cases where it is necessary compact placement distribution device. In particular, switchgear is used at power plants, city substations, and for powering facilities oil industry(oil pipelines, drilling rigs), in ship energy consumption diagrams.
A switchgear in which all devices are located in one compartment is called a one-way service chamber (SOC). As a rule, the KSO is truly one-way service, most often has open busbars, and there is no back wall.
Switchgear device 
As a rule, the switchgear cabinet is divided into 4 main compartments: 3 high-voltage - cable compartment (input or line), switch compartment and busbar compartment and 1 low-voltage - relay cabinet.
§ The relay compartment (3) contains low-voltage equipment: relay protection and automation devices, switches, circuit breakers. On the door of the relay compartment, as a rule, there are light-signal fittings, electricity metering and measurement devices, and cell control elements.
§ The switch compartment (4) contains a power switch or other high-voltage equipment (disconnect contacts, fuses, voltage transformers). Most often in switchgear, this equipment is placed on a withdrawable or retractable element.
§ In the busbar compartment (6) there are power busbars (8) connecting the cabinets of the switchgear section.
§ The input compartment (5) is used to accommodate cable termination, measuring current transformers (7), voltage transformers, surge arresters.
RU up to 1000V.
The main type of switchgear with voltages up to 1000 V are switchboards. With their help, they supply power to external loads and the substations’ own needs. Distribution boards varied in design and in the devices and devices installed in them. Panels are made up of panels or cabinets interconnected in quantities and combinations corresponding to the design scheme and the construction part of the panel room. The panel (or cabinet) is a completely finished element of the switchboard, and the switchboard as a whole is a complete electrical device.
The panel is a metal structure (frame with front panel), on which devices and devices for switching, measurement and protection are installed. Panel panels are connected by busbars and wiring secondary circuits, to which equipment mounted on panels is connected. They are divided into inlet, linear and sectional depending on the purpose of the devices installed on them, as well as end ones, the purpose of which is the protective and decorative covering of the sides of the outer panels of the shield. Panels of all series are based on a single frame made of bent steel sheets 2-3 mm thick with parts made of bent steel profiles for mounting devices and the same design: two front posts, an upper front sheet for measuring instruments, doors for servicing devices installed on the frame inside, two rear posts, transverse and longitudinal connections. The handles of the machine drives and switches are brought out onto the panel façade through rectangular holes.
Installation of panels begins with marking the installation location of the foundation frame, which must be installed in the first stage installation work. The passages between the wall and the shield, the symmetrical arrangement of the longitudinal and transverse axes of the shield to the switchboard room, the interface with cable ducts and openings, taking into account the level of the finished floor, are checked.
The panels are installed after completion of construction and finishing works on foundation frame, aligned in horizontal and vertical planes and temporarily secured. After installation, connecting the blocks or panels together and alignment, the shield is finally secured with bolts or welding. They install busbars and install devices that arrive in separate packaging.
The complex hierarchy of modern electrical networks includes a huge number of different electrical equipment, among which transformer substations act as a link that connects and redistributes electricity. They are located near or inside populated areas and provide comfortable conditions for human habitation.
IN rural areas You can still find designs of old pole substations operating in the open air, which receive 10 or 6 kV on the high side of the overhead line and give 0.4 to connected consumers.
Inside populated areas With multi-storey buildings For security purposes, cable lines hidden in the ground are more often used, and transformer equipment is located inside special buildings that are locked to prevent unauthorized entry.
The building of a similar transformer substation that converts a voltage of 10 kV to 0.4 is shown in the photograph.
External difference The dimensions of the shown substations, converting voltages of the same magnitude, indicate that they operate with different powers.
Such transformer substations (TS) receive electricity via high-voltage power lines of 10 kV (or 6) from remote switchgears.
A photograph of a power transformer located at ORU-110 and converting 110 kV electricity into 10 kV, transmitted via power lines to PS-10, is shown in the next photograph.
This transformer is already large in size and operates with capacities of up to 10 megawatts; it is located in an open, fenced area, which, by the design of the equipment, is clearly demarcated into two sides:
higher voltage 110;
lowest - 10 kV.
110 kV side overhead power line connects to another substation, which has even larger dimensions and converts huge energy flows.
The dimensions of only the input support of a single overhead power line make it possible to visually assess the significance of the electricity flows passed through it.
The above photographs indicate that transformer substations in the energy sector process electrical energy of various voltages and powers and are installed various designs, but have common features.
Composition of transformer substation equipment
Working conditions
Each substation is created for specific operating conditions with the location:
in the open air - open switchgears (OSD);
indoors - closed switchgear;
in metal cabinets built into special kits- KRU.
By configuration type electrical network transformer substations can be performed:
dead-end, when they are powered by one or two radially connected power lines that do not power other substations;
branch lines - they are connected to one (sometimes two) passing power lines using branches. Passing lines feed other substations;
pass-through - connected by entering power lines with two-way power supply using the “cut-in” method;
nodal - connected according to the principle of creating a node using at least three lines.
The configuration of the power supply network imposes conditions on the operating characteristics of the substation, including the configuration of protections to ensure safe operation.
Basic elements of PS
The equipment of any substation includes:
power transformer, which directly transforms electricity for its further distribution;
buses providing supply of incoming voltage and removal of loads;
power switching devices with current conductors, allowing the redistribution of electricity;
protection, automation, control, alarm, measurement systems;
input and auxiliary devices.
Power transformer
It is the main transforming element of electricity and is made in a three-phase design. Its design includes:
a housing made in the form of a sealed tank filled with oil;
laminated magnetic circuit;
winding side low voltage(NN);
windings of high voltage inputs (HV);
oil system;
switch of adjusting taps at the windings;
auxiliary devices and systems.
The structure of the power transformer and autotransformer is described in more detail.
Substation buses
In order for the transformer to work, it is necessary to supply the supply voltage to it and remove the converted voltage. This task is assigned to current-carrying parts, which are called busbars and busbars. They must reliably transmit electrical energy with minimal .
To do this, they are created from materials with improved conductive properties and an increased cross-section. Depending on the size of the PS, tires can be located outdoors or inside a closed structure.
The busbars and busbar are electrically separated from each other by the position of the power switch. Moreover, the busbar without any switching devices is directly connected to the transformer inputs. Its design should not create mechanical stress in porcelain and all other parts of the bushings.
For busbars, cables or plates are used, which are mounted on copper studs of transformer inputs through lugs or adapters.
In substations protected from atmospheric precipitation, the busbars are usually made of solid aluminum or, less commonly, copper strips. In the open air, multi-core wires of increased cross-section and strength, not covered with a layer of insulation, are often used for them.
However, in Lately There has been a transition to rigidly mounted bus systems. This allows you to save space on outdoor switchgear, metal of live parts and concrete.
Such designs are used at new substations under construction. They are based on samples that have been successfully operating for several decades in Western countries on equipment of 110, 330 and 500 kV.
A specific configuration is used for the busbar layout, which can use:
systems;
sections.
The term “bus system” means a set of power elements connecting all connections on the switchgear. At substations with two transformers of the same voltage, two bus systems are created, each of which is powered by its own source.
Extended bus system with large quantities connections can be divided into separate sections, which are called sections.
Power switching devices
During operation, transformer substations must be connected to voltage or taken out of operation for preventive maintenance or in the event of emergencies and malfunctions. For this purpose, switching devices are used, which are created in various designs and can:
1. turn off emergency currents of the maximum possible values;
2. switch only workloads;
3. provide a break in the visible area electrical diagram due to switching only when the voltage is removed from the equipment.
Switching devices capable of switching off emergency situations operate in automatic mode and are called “circuit breakers.” They are created with various load switching capabilities due to design features.
Based on the principle of using stored energy put into work actuator, they are divided into:
spring;
cargo;
pressure;
electromagnetic.
According to the methods of extinguishing the electric arc that occurs during shutdowns, they are classified into:
air;
SF6;
vacuum;
oil;
autogas;
electromagnetic;
autopneumatic.
To control exclusively operating modes, characterized only by nominal network parameters, “load switches” are created. The power of their contact system and the speed of operation allow successful switching in the normal state of the circuit. But they cannot be operated to eliminate short circuits.
When an electrical circuit breaks under load, it creates electric arc, which is eliminated by the design of the switch. In a de-energized circuit, simpler devices are used to isolate a certain section from the voltage:
1. disconnectors;
2. separators.
Mutual arrangement of switching devices and buses
Any transformer substation is created according to a specific electrical circuit, which provides reliable operation, ease of management combined with a minimum of commissioning and operating costs. For this purpose, to the transformer device different ways outgoing power lines are connected.
Most simple circuit involves connecting to the transformer transformer via power switch Q one section of busbars, from which all connections depart. To ensure conditions for safe repair of equipment, switches are separated on all sides by disconnectors.
If there are many connections on the substation, when 2 power transformers are used in the circuit, then sectioning can be used by using an additional switch, which is constantly in operation, and if a malfunction occurs in one of the sections, it breaks the circuit, leaving the section in operation where there is no breakdown .
The use in such a circuit of a bypass bus system formed by connecting additional switches and minor adjustments electrical circuits, allows you to transfer any connection to power from a bypass switch, and safely carry out repairs and maintenance of your own.
In its original state, everything is waste The existing power lines receive electricity from both transformers. To do this, busbar and sectional switches supply bus sections, and connections are evenly distributed over them through their switching devices.
The bypass power supply of each section is energized only in case of transfer of power supply through it to a connection whose switch is taken out for repair.
Whenever short circuit on one of the sections it is turned off by protection on all sides, and all the others with power lines connected to them remain in operation. Due to this scheme, during a short circuit at the outdoor switchgear, the minimum number of consumers from all workers is de-energized.
The given diagrams are shown as an example. There is a wide variety of them, which allows for the most optimal operation of transformer substation equipment.
Protection, automation, control systems
The operation of the transformer substation equipment occurs automatically under the remote supervision of operating personnel. Automatic safety devices are used to prevent serious damage within a complex, expensive system.
They have sensitive sensors that perceive the onset of emergency processes and, processing the information received, transmit it to protection.
Such sensors can work mechanical devices responsive to:
temperature increase;
the appearance of a flash of light;
a sharp increase in pressure inside a closed cell;
smoke generation;
the onset of gas formation within liquids or other signs.
However, the main burden of determining the onset of emergency modes is placed on electrical devices - measuring and.
They simulate with high accuracy the electrical processes occurring in the primary circuit of power equipment and transmit them to comparison bodies, which determine the moment when malfunctions occur.
The received signal from them is perceived by logical blocks that process the received information to transmit an executive command to the disconnecting devices of specific circuit breakers.
For small-sized transformer substations, located inside covered structures, protection can be located in a separate cell or cabinet.
At substations that convert voltages of 110 kV and above, placement of relay secondary circuits requires separate building with a lot of panels. They are equipped with control, automation and protection systems:
each transformer;
busbars;
tires;
outgoing lines;
fire extinguishing
Alarm systems operating in local and remote modes are connected to these devices to transmit reliable information to operational personnel about the ongoing switching in the electrical network. Most important information the position of critical equipment elements is transmitted via telesignaling channels.
Relay protections, used for many decades, are gradually being replaced by microprocessor-based small-sized modules that facilitate operation.
However, their widespread use is hampered by high costs and the lack of precise international standards for all manufacturers. After all, if a specific unit breaks down, the user has to contact a specific plant to replace the problem.
Switchgear (RU) is an electrical installation designed to receive and distribute electrical energy, containing electrical devices, buses and auxiliary devices. Electrical stations, step-down and step-up substations, usually have several switchgears of different voltages (HV switchgear, LV switchgear, LV switchgear).
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) busbars or wires strictly in accordance with the electrical diagram.
For the energy system, the reactor plant is a network node equipped with electrical devices and protective devices, serving to control the distribution of energy flows, disconnect damaged areas, 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, determined by the adopted circuit. All similar connections are made in the same way, so the switchgear is assembled from standard, seemingly standard, cells.
RU must meet certain requirements, the most important of which are: reliability of operation, convenience and safety of maintenance when minimum costs for construction, fire safety and economical operation, the possibility of expansion, maximum use of large-block prefabricated units.
Reliability of switchgear operation is ensured the right choice And correct installation electrical equipment (electrical devices, live parts and insulators), as well as good localization of accidents with electrical equipment if they occur. In addition, the reliability of the reactor plant largely depends on the quality of construction and electrical installation work.
RU are performed for all applicable voltages. By analogy with the 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 promising ultra-high voltage switchgear 1150 kV and higher.
According to their design, switchgears are divided into closed (internal), in which all electrical equipment is located inside the building, and open (external), in which all electrical equipment is located in the open air.
Rice. 2.1. GRU 6 – 10 kV with one bus system and group reactors (section along the generator and group reactor circuits) 1 - current transformer, 2 - bushing insulator, 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 duct, 10 – switchgear cells
Closed switchgear (SGD) - This is a distribution device located inside the building. They are usually built at a voltage of 3 – 20 kV. In high voltage installations, 35 - 220 kV, closed switchgears are built only with limited area under the switchgear, when 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 indoor switchgear should be convenient and safe. For safety, the minimum permissible distances from live parts to various elements ZRU
To avoid accidental touching, uninsulated live parts must be placed in chambers or fenced. The fence can be solid or mesh. In many indoor switchgears, mixed fencing is used - the drives of switches and disconnectors are mounted on the solid part of the fencing, and the mesh part of the fencing allows observation of the equipment. The height of such a fence must be at least 1.9 m, while the mesh must have holes measuring no more than 25x25 mm, and the fences must be locked.
From the premises of the switchgear, exits are provided to the outside or to rooms with fireproof walls and ceilings: one exit for 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 in 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.
The closed switchgear must ensure fire safety. When installing oil transformers in closed switchgear, measures are taken to collect and drain oil into the oil collection system. The closed switchgear provides for natural ventilation of transformer and reactor rooms, as well as emergency exhaust ventilation of service corridors open cells with oil-filled equipment.
Prefabricated switchgear (SRU) assembled from enlarged units (cabinets, panels, etc.), manufactured and equipped in 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. 110 kV indoor switchgear (section through an air circuit breaker cell)1 - VNV-110 kV circuit breaker, 2 - first busbar system, 3 - busbar disconnectors, 4 - second busbar system, 5 - bypass busbar system, 6 - bypass disconnector, 7 - coupling capacitor, 8 - line disconnector.
Complete switchgear (KRU) is a switchgear completely manufactured in factories, consisting of closed cabinets with built-in devices, measuring and protective devices and auxiliary devices; All switchgear elements are simply mounted on site. These switchgears best meet the requirements of the industrialization of energy construction, so they are currently becoming the most common form of switchgear design. The use of switchgear 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, and inert gases can be used as insulation between live parts in switchgear. Switchgear with oil and gas insulation can be manufactured for high voltages of 220 - 500 kV. Our industry produces switchgear of 3 - 35 kV with air insulation and 110 - 220 kV with SF6 insulation (in world practice up to 800 kV).Complete outdoor switchgears (KRUN) are designed for open installation.
outside premises. KRUN consist of metal cabinets with built-in devices, instruments, protection and control devices. KRUN are designed to operate at ambient temperatures from -40 to +35 °C and air humidity of no more than 80%. KRUN can have a stationary installation of the circuit breaker in a cabinet or a withdrawable trolley with a circuit breaker, similar to the switchgear indoor installation Cabinets KRZ-10 (Fig. 2.3) for outdoor installation 6 – 10 kV are intended for networks Agriculture
, industry and electrification of railway transport. KRZ-10 cabinets are designed for temperatures
environment
from +50 to -45°С.
Open switchgear (OSD)At the same time, at present, mixed-type switchgears are also widely constructed, partly as prefabricated and partly as complete ones.
All devices in outdoor switchgear are installed on low foundations (metal or reinforced concrete). Passages are made through the territory of the outdoor switchgear to enable mechanization of installation and repair of equipment. Busbars can be flexible stranded wires or rigid pipes. Flexible busbars are secured using suspension insulators on portals, and rigid busbars are secured using support insulators on reinforced concrete or metal racks.
The use of rigid busbars makes it possible to abandon portals and reduce the area of outdoor switchgear.
An oil receiver is provided under power transformers, oil reactors and tank switches of 110 kV and above, a layer of gravel at least 25 cm thick is laid, and the oil flows in emergency cases into underground oil collectors. Cables of operational circuits, control circuits, relay protection, automation and air ducts are laid in trays made of reinforced concrete structures without burying them in the soil or in metal trays suspended from outdoor switchgear structures.
The outdoor switchgear must be fenced.
Advantages of outdoor switchgear compared to indoor switchgear
1) smaller volume construction work; since only site preparation, road construction, foundation construction and installation of supports are necessary;
2) significant savings building materials(steel, concrete);
3) lower capital costs;
4) shorter construction time;
5) good visibility;
6) ease of expansion and ease of replacing equipment with others of smaller or larger dimensions, as well as the ability to quickly dismantle old and install new equipment.
7) less danger 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 switching disconnectors and monitoring devices is carried out in the air in any weather ( low temperatures, bad weather);
2) large area of the structure;
3) exposure of devices to sudden changes in ambient temperature, their vulnerability to pollution, dust, etc., which complicates their operation and forces the use of devices of a special design (for outdoor installation), which are more expensive.
The cost of indoor switchgear is usually 10–25% higher than the cost of the corresponding outdoor switchgear.
Currently, in most cases, outdoor switchgear is used of the so-called low type, in which all devices are located in the same horizontal plane and installed on special bases of a relatively small height; prefabricated busbars are mounted on supports that are also of relatively low height.
Distribution device (RU) refers to an electrical installation that serves to receive and distribute electricity and contains switching devices, busbars and connecting buses, auxiliary devices (compressor, battery, etc.), as well as protection devices, automation and measuring instruments.
Switchgear 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 a switchgear is located in the open air, it is called open (OSU): if it is located in a building, it is called closed (ZRU). A switchgear consisting of fully or partially closed 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 internal installation of switchgear, for external installation - KRUN.
Power center - a generator voltage switchgear or a secondary voltage switchgear of a step-down substation, to which the distribution networks of a given area are connected.
Switchgears (SD) are classified according to several criteria; below we present their types and design features.
Switchgears up to 1000 V
Switchgears up to 1000 V are made, as a rule, indoors in special cabinets (panelboards). Depending on the purpose, 220/380 V switchgears (voltage class 0.4 kV) can be designed to power consumers or exclusively for the electrical installation’s own needs.
Structurally switchgears 0.4 kV have protective devices ( circuit breakers, fuses), switches, switch-disconnectors and busbars connecting them, as well as terminal blocks for connecting cable lines consumers.
In addition to power circuits, a number of additional devices and auxiliary circuits, 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;
signaling and ground fault protection devices (for IT configuration networks);
automatic reserve input devices;
remote control circuits for switching devices with motor drives.
Low-voltage switchgears can also include DC switchboards that distribute DC current from converters, batteries for power supply of operational circuits of electrical equipment and relay protection and automation devices.
High voltage switchgears
Switchgears of voltage class above 1000 V can be designed both outdoors - open type (OSU), and indoors – closed type(ZRU).
Equipment is placed in closed switchgears in prefabricated chambers for one-way service of KSO either in complete switchgears type KRU.
Cameras of the KSO type are more preferable for rooms of limited area, since they can be installed close to the wall or to each other back walls. KSO chambers have several compartments closed with mesh fences or solid doors.
CSOs are equipped with various equipment, depending on their purpose. To power the outgoing lines, a high-voltage switch, 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 switch drive, as well as low-voltage circuits and protection devices implemented to protect and control this line.
Cameras of this type can be equipped with voltage transformers, arresters (overvoltage limiters), fuses.
Switchgear type KRU They are a cabinet divided into several compartments: current transformers and outgoing cables, busbars, a withdrawable part and a secondary circuits compartment.
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, a voltage transformer, arresters (arresters), and an auxiliary transformer.
The retractable element relative to the cabinet body can occupy a working, control (disconnected) or repair position. In the operating 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 retractable element is located outside the cabinet body and its main and auxiliary circuits are open. The force required to move the retractable element should not exceed 490 N (50 kgf). When the retractable 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 switchgear are made, as a rule, with busbars made of aluminum or its alloys; at high currents, the use of copper busbars is allowed, at rated currents up to 200 A - steel. Installation of auxiliary circuits is carried out insulated copper wire with a cross section of at least 1.5 square meters. mm, connection to meters - with a wire with a cross-section of 2.5 sq. mm, solder joints - at least 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 retractable element is carried out using plug connectors.
Switchgear cabinets, as well as grounding blades, 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 switchgear cabinets and its elements must withstand is regulated: detachable contacts of the main and auxiliary circuits, a retractable element, doors, and a grounding switch. The number of cycles of switching on and off the built-in component equipment (switches, disconnectors, etc.) is accepted in accordance with the PUE.
To ensure safety, switchgear cabinets are equipped with a number of interlocks. After rolling out the retractable element, all current-carrying parts of the main circuits that may be energized are covered with protective curtains. These curtains and barriers must not be removed or opened without the use of keys or special tools.
In stationary switchgear cabinets, it is possible to install stationary or inventory partitions to separate live parts of equipment. It is not allowed to use bolts, screws, or studs that act as fasteners for grounding. In grounding areas there must be an inscription “earth” or a grounding sign.
The type of switchgear cabinet is determined by the circuit diagram of the switchgear main circuit. The main electrical device that determines the design of the cabinet is the switch: low-oil, electromagnetic, vacuum and SF6 switches are used. Secondary circuit designs are extremely diverse and have not yet been completely unified.
Complete devices may have different design, for example, with gas insulation - GIS or intended for outdoor installation - KRUN, which 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 influences and moisture.
Switchgears, both closed and open types, are classified according to several criteria, depending on their design (scheme).
The first criterion is the method of performing partitioning. There are switchgears with busbar sections and busbar systems. Bus sections provide power to each individual consumer from one section, and bus systems allow one consumer to be switched between several sections. Bus sections are connected by sectional switches, and bus systems are connected by bus connectors. These switches allow sections (systems) to be powered from each other in the event of a loss of power in one of the sections (systems).
The second criterion is the presence of bypass devices– one or more bypass bus systems that allow equipment elements to be removed for repair without the need to de-energize consumers.
The third criterion is the equipment power supply circuit (for open switchgear). IN in this case There are two possible scheme options - radial and ring. The first scheme is simplified and provides for power supply to consumers through one switch and disconnectors from the busbars. In a ring circuit, each consumer is powered by two or three switches. Ring circuit more reliable and practical in terms of equipment maintenance and operation.