Video

Switchgear equipment up to 1000V. Distribution devices: types, design features. Distribution boards, points, cabinets

Each power station or substation has a switchgear whose purpose is to receive electrical energy from a generator or transformer and transmit it to consumers. Instruments and devices installed in the switchgear allow you to turn on and off individual consumers or their groups, take into account the energy they consume, measure power, current, voltage, frequency, etc. Switchgears contain damage protection devices on outgoing lines.

Distribution devices can be of a closed type, when all elements of the electrical connection circuit - switches, disconnectors, instrument transformers, instruments, etc. - are located indoors, and open type, located outdoors. Switchgears for voltages of 35 kV and higher are usually constructed of an open type. In this case, measuring instruments and relay protection equipment are installed in special cabinets. Complete switchgears (KRU, KRUN) are widely used at stations and substations.

In low-voltage switchgears, frame-type distribution boards with one-way and two-way service are used. The distribution board is completed from separate panels - input, linear, sectional and end - of various designs.

Figure 14.9 shows a sketch and diagram of a linear panel of a ShchOB type shield. The panel consists of a frame on which BPV blocks (fuse-switch block), BV (block with knives instead of switches having a double circuit break) and measuring instruments are mounted. The frame is vertically divided into five compartments. Busbars and instruments are located in the middle compartment, blocks are located above and below it, only instruments are located in the upper compartment, and line terminations are located in the lower compartment. The compartment covers are removable. This allows installation, inspection and repair from the front side of the shield.

For low-power power plants (from 35 to 150 kV-A), the industry produces standard control panels of the ShchUP type. Next in the shield designation is a number indicating the power of the generator for which the shield is intended. Such a switchboard is equipped with all the necessary instruments and apparatus for controlling the generator, monitoring its operation and distributing energy between consumers. Figure 14.10 shows a diagram of a switchboard of the SHUP-35R type (with manual voltage regulation) for controlling a generator with a power of 35 kV A. The SHUP-60R and SHUP-125 switchboards are made according to a similar diagram.

The generator with the exciter is connected to the corresponding terminals of the shield - C, C2, C3 and Ya, Sh, YaSh. Energy from the generator is supplied through an A3100 type circuit breaker to consumer feeders No. 1, 2 and 3, which are switched on and off by circuit breakers 1 of the same type, equipped with built-in thermal overload protection. Automatic 2 is, in addition, equipped with an electromagnetic release for protection against short circuits. The voltage is manually regulated by rheostat 8, which is connected to the exciter excitation winding circuit. The current in each phase is measured by ammeters 6 connected through current transformers 5, the voltage between any two phases by a voltmeter 3 with a switch, and the frequency by a frequency meter 7. To obtain the phase voltage, two clamps with a ground symbol are provided at the bottom of the shield. The control panel type SHUP-125R is additionally equipped with an energy meter of the SA4 brand.

Practical work

Design and operation of switchgears up to 1000 V.

Goal of the work: familiarization with the design and maintenance of switchgear up to 1000 V.

RU up to 1000Vare designed for redistribution of electricity at electrical substations (TP, RP, RTP 6-10/0.4 kV) from the power transformer to outgoing lines, and are also installed for control and protection against overloads.

RU up to 1000 V contain:

Switching devices;

Prefabricated and connecting busbars;

Auxiliary devices (combined, etc.)

Protection devices, automation and measuring devices.

Traditionally, 0.4 kV switchgears are located in close proximity to power sources (power step-down transformers), from which they receive power and distribute it among consumers. The main installation sites for RU-04 kV are administrative, residential and industrial buildings and structures, transformer substations (TS) and distribution points (DP).

Main functions of the switchgear RU - 0.4:

reception and distribution of electricity;

protection of outgoing lines from overloads and short circuits;

electricity metering;

measurement of parameters of incoming and outgoing lines.

Design of 0.4 kV switchgears

The design of the 04 kV switchgear includes the following elements:

1. Introductory panels. They are designed to provide input from a power transformer (busbar or cable), protect busbars and the transformer from short-circuit currents. and overloads, indication of voltage presence, operation of the automatic transfer switch circuit, organization of commercial electricity metering.

2. Distribution panels. Designed to protect the outgoing electrical line from short-circuit currents. and overloads, implementation of operational switching and organization of commercial accounting.

3. Sectional panels. They are used for sectioning different busbar systems of one switchgear 04 kV and operating automatic transfer switches in automatic mode.

4. Auxiliary panels. They are used to monitor and control the operation of capacitor banks, lighting systems and the own needs of the electrical installation.

The material for the manufacture of RU-0.4 kV enclosures is sheet metal coated with paint and varnish, which determines its following advantages:

high mechanical strength and electrical conductivity;

resistance to temperature changes over a wide range;

long service life;

reliability and ease of maintenance.

All RU-0.4 kV panels have a terminal for fastening busbars and grounding wires, which is a mandatory requirement of the electrical installation rules (PUE). All switchgear panels are equipped with a locking device, which prevents unauthorized access to exposed live parts.

Advantages of switchgear - 0.4 kV

Among the advantages of working with RU-04 kV, the following points should be highlighted:

the ability to implement protection against electrical network overload, short circuits to ground and phase-to-phase faults;

installation of commercial metering units that can be easily sealed;

control of electrical energy parameters (currents, voltage, power) on inputs and output lines;

sectioning in order to increase the reliability of power supply, automatic transfer switch operation;

sound and light alarm about the operation of protection devices;

protection of busbars using input circuit breakers;

the possibility of creating an automated process control system based on RU-04 kV;

implementation of operational switching in the shortest possible time;

high reliability of power supply to consumers of any category.

Maintenance and work with RU-04 kV is possible both from one and from both sides, depending on the type of panels. Depending on the type of protection (IP), RU-04 kV may have varying degrees of exposure to external factors (dirt, moisture, dust and others). Also, 0.4 kV switchgears can differ in the type of climatic design, which makes it possible to operate a variety of panel models both in countries with a tropical climate and in the far north.

RU up to 1000V are performed in the form:

Control station panels;

Distribution and line boards;

Remotes;

Cabinets;

Bus terminals;

Assemblies, etc. installed indoors or outdoors.

Switchboards, input devices, consoles, panels and other distribution devices of modern designs are complete complete devices for receiving and distributing electricity, controlling and protecting against overloads and short circuits. They contain switching and protective devices, measuring instruments, automation equipment (in some cases) and auxiliary devices. When using complete devices, labor costs for installation are significantly reduced and the performance of networks is improved.

Shields are divided into:

distribution,

management,

relay,

signaling and control.

They are metal structures made up of separate panels, control panels or cabinets on which the instruments and devices provided for by the project are located, as well as busbars and secondary circuit wiring for connecting the installed equipment.

Distribution boards are designed for receiving and distributing electricity in networks with voltages up to 1000 V and, depending on the design, are divided into single- and double-sided service, panel and cabinet.

Industrial

distribution board Indoor distribution board

Input distribution panel Open distribution panel

Distribution board Panel distribution board

Cabinet distribution board

One-way service boards (SSC) are produced in several types and are manufactured inopen Andclosed performances.

The first panels are assembled from panels and installed in special electrical rooms, the second ones are made from cabinets with seals and are placed directly in the workshops.

Single-sided service panels are made up of standard panels - linear, input and sectional.

Linear panels are used to connect electricity consumers to the busbars, input panels are used to connect busbar and cable inputs, sectional panels are used to section (isolate) busbars for rated connection currents. The sides of the outer panels of the shield are covered with end panels with a protective and decorative door.

Panels of all types have a single frame made of bent steel sheets 2–3 mm thick, on which protective and switching protective devices and measuring instruments are installed. All parts for attaching devices are also made from bent steel profiles. The busbar is carried out using flat aluminum busbars on insulators. Busbars are placed at the top of the panel. The main standard panels are produced with a width of 800, a height of 2160 (without a removable cornice - 1950) and a depth of 550 mm.

Switches and fuses on linear panels are mounted on a common plate: the lower posts of the switch are combined with the upper fuse posts, which reduces the height of the plate. These plates with devices up to 400 A are installed in two rows. The drive handles are placed on the panel posts on both sides of the doorway, and the machine handles are brought out to the facade through rectangular holes in the panel door.

At present, ShchO-70 switchboards are still widely used (Fig. 29, a, b), the panels and cabinets of which can have different designs, allowing the implementation of switchgears provided for by the design. Both panels and ShchO-70 cabinets have overall dimensions of 2200Х600Х (800--1100) mm and a maximum connection current of 2000 A.

The following are installed in the ShchO-70 panel:

automatic switches series VA,

disconnectors

current transformers

fuses type PN-2;

Input distribution devices (IDUs) are designed for receiving and distributing electricity and protecting outgoing lines in three-phase 380/220 V networks with a solidly grounded neutral.

The most common devices are VRU-70, the panels and cabinets of which can have different designs that allow you to assemble the switchgear provided by the project.

Input distribution devices (IDU)

Group distribution panels for lighting are complete devices for switching and protecting lighting networks.

Lighting shield

Batch switches or magnetic starters are installed in the lighting circuits. To account for energy, electric energy meters of type C02 or CA4 are used, turning them on through a current transformer.

They produce shields for residential buildings and general purposes, intended for industrial and civil buildings. Panels for residential buildings (storey, apartment and combined) are manufactured in various modifications.

Control, relay, alarm and monitoring panels

Closetmanagement smoke removal

Closetrelay Closetalarm and control

Maintenance of switchgear equipment up to 1000 V.

The following scope of maintenance work is performed on cable lines:

a) cable lines (CL) for external and internal installation up to 1000V;

inspection and cleaning of cable channels, routes, openly laid cables,

inspection and cleaning of end funnels and couplings;

checking grounding and eliminating detected defects;

restoration of damaged or lost markings;

determination of cable heating temperature and monitoring of cable sheath corrosion;

carrying out established measurements and tests of cable networks;

b) internal power networks of the switchgear up to 1000 V, made of wires of various brands and sections, lighting networks and secondary circuits, grounding networks and grounding devices;

checking the strength of connecting points, mechanical protection, especially at the points of exit from pipes, inputs into devices and terminal boards, passages through walls and ceilings;

checking contact connections, checking fastening along the entire length and individual sections of the network;

restoration of damaged or lost markings,

checking the condition of inscriptions and warning posters;

checking insulation with a megohmmeter,

checking the compliance of fuses and fuses with rated currents and replacing them if necessary;

Carrying out specified measurements and tests.

For electrical devices and complete devices of low voltage (up to 1000 V) (switches and switches, automatic air circuit breakers, magnetic starters, contactors, switches and batch switches, buttons and control stations, distribution points, lighting panels, electric lighting fixtures).

The following scope of maintenance work is carried out:

checking the compliance of devices with operating conditions and load,

cleaning of devices,

checking the serviceability of the electrical wiring and grounding networks connected to the devices,

external and internal inspection of devices,

tightening fasteners,

cleaning contacts from dirt and deposits,

checking the serviceability of casings, handles, locks, handles and other fittings;

checking the oil level and temperature, absence of leaks and adding oil (if necessary);

checking the heating of resistance elements and contacts in all ballasts,

the presence of appropriate inscriptions on shields, panels and devices;

checking the presence of heating elements and thermal relays and their compliance with the rated current of the pantograph;

checking the presence and serviceability of the mechanical interlock,

regulation of the simultaneity of turning on and off the blades of switches and switches,

replacement of fuses and fuse links;

checking the operation of signaling devices and the integrity of seals on relays and other devices;

checking the availability of reserve elements and spare parts for maintenance and repair.

After completion of maintenance, adjustment and testing of electrical equipment and devices of consumer electrical installations is carried out in accordance with the “Scope and standards for testing electrical equipment” RD 34.45-51.300 - 97.

Current repairs of switchgears with voltages up to 1000 V are carried out at least once a year on open transformer substations and after 18 months on closed transformer substations. At the same time, the condition of the end seals is monitored, dust and dirt are removed, as well as insulators are replaced, tires are repaired, contact connections and other mechanical components are tightened, light and sound signaling circuits are repaired, and measurements and tests established by standards are carried out.

Major repairs of switchgears with voltages up to 1000 V are carried out at least once every 3 years.

The order of practical work:

Study the design and maintenance of 0.4 kV switchgear

Draw up a report on the work, answer control questions.

Control questions

SWITCH GEARS UP TO 1000 V

Switchgears up to 1000 V are installed indoors and outdoors. They are made in the form of distribution, control and relay panels and consoles, cell-type installations, cabinets, bus terminals and assemblies. Indoor switchgears are located in industrial and various-purpose premises. For outdoor installation, prefabricated reinforced concrete elements are used as foundations, placed on planned sites at a height of 0.2 m. In areas where snow drifts are possible, the supporting platforms for the switchgear are raised to 1 m or more.
The switchgear electrical equipment has lower or upper current leads. Depending on the design solution and design, floor-mounted low-voltage switchgear with bottom current supply is installed: on the floor with current supply in pipes or with a cable duct at the back, on the ceiling, on the floor with a cable duct in the front, above the cable duct (Fig. 16). For switchgear with top current supply, niches and openings are arranged in the walls and ceilings of the premises.

Rice. 16. Methods for installing shields in switchgear up to 1000 V:
a - on the floor with current supply in pipes; b - on the floor with a cable channel at the back; e - on the ceiling; g - on the floor with a cable channel in front; d - above the cable channel

The electrical equipment of the reactor plant is fastened to embedded parts embedded in the building foundations. Various mounting options are shown in Fig. 17. The distances between embedded parts are determined by the design features of electrical equipment. For example, embedded parts made of steel plates are installed along the facade of the boards every 1-2 m, two rows of parts of one board are placed at a distance equal to its depth. The embedded parts in the switchgear room are placed taking into account certain distances to the walls and between the panels, caused by the need to create passages provided for by the PUE.

Rice. 17. Embedded parts for fastening electrical equipment:
a - location plan; b - fastening the embedded part E-2 to the building foundation; e - location of holes for anchor bolts; I—embedded part; 2 — floor grout; 3 - floor, ceiling and precast reinforced concrete; 4 - niche

Large-block shields of protected design, which do not have frame bases, are installed on channels No. 6.5, laid in the base along the cabinet assembly. Panels made from Shch070 and RTZO panels are installed on frames. Cabinets installed on stands are secured to embedded parts made of steel plates. Floor distribution points PR 9300 are attached to embedded elements embedded flush with the finished floor. To install wall points, embedded structures are fixed to the walls. It is allowed to fasten the electrical equipment of the switchgear with anchor bolts installed in the sockets left during execution and filled with cement mortar after installation of the panels and cabinets. The use of metal platforms for placing electrical equipment of the switchgear does not require embedded parts, since cabinets and panels are fixed by welding directly to the platforms.

Panels with dimensions of no more than 2400 mm in height, no less than 550 mm in depth and a weight of more than 1600 kg and cabinet assemblies with a height of less than 2200 mm, a depth of more than 1100 mm and a weight of no less than 1200 kg can be installed directly on a clean floor without fastening to embedded elements.
The conditions and procedure for accepting switchgear premises up to 1000 V for installation are similar to the conditions and procedure discussed in paragraph 2.
During the period of the main construction work, before the completion of clean floors and finishing in the switchgear room, the personnel of the production preparation groups, in accordance with the project, carry out control markings, determine the compliance of the placement of embedded parts with each other and in relation to parts of the building. At the same time, it is taken into account that the location of the embedded parts determines compliance with the standards for the minimum dimensions of passages in electrical rooms after installation of electrical equipment on them.

Table 6. Permissible distances when placing electrical equipment of the reactor plant

They also check the compliance of the dimensions of doorways for delivery of assembled panels assembled into blocks at the manufacturer or in workshops.
The permissible distances from the most protruding unfenced uninsulated live parts (for example, disconnected knife switches) located at an accessible height (less than 2.2 m) are given in Table. 6. Non-insulated live parts located at distances less than those indicated in the table. 6, are fenced with mesh solid or combined structures 1.7 m high.
In the same way, electrical equipment of a switchgear with unprotected live parts is protected when placed in production premises accessible to uninstructed personnel. The design of such a fence depends on local conditions and may have removable panels that can be secured and removed with the mandatory use of tools (for example, wrenches). The fence doors are locked with a key. The distance from the mesh fence to the non-insulated current-carrying parts of the switchgear is at least 0.7, and from solid parts - at least 0.05 m. The width of passages is taken in the same dimensions as for electrical rooms.
When accepting the switchgear room for installation, its dimensions, the presence and dimensions of permanent or temporary installation openings are checked, as well as the possibility of delivering blocks up to 4 m long, the presence and binding of embedded parts, and the possibility of current supply.
The dimensions of the room are checked in the same way as described in § 2. The possibility of delivering electrical equipment assemblies to the switchgear room is assessed taking into account the required dimensions (Table 7) and the location of the installation openings.

Table 7. Minimum dimensions of installation openings in switchgear rooms

When checking the embedded parts embedded in the building foundations of the switchgear, the distances are controlled: between the embedded parts of one panel, between the embedded parts and the walls of the room, between the embedded parts of different panels when placing electrical equipment in multiple rows; between embedded parts in the aisles of the same row (Fig. 18). The measured distances between embedded parts along the façade of switchgear panels, depending on the size of the electrical equipment, are compared with the data given in Table. 8.

Rice. 18. Controlled dimensions in switchgear up to 1000 V:
a - RU plan; b - c - options for placing embedded parts; 1 — embedded part E-2

Table 8. Distances when installing embedded parts in the switchgear room

The location of the embedded parts in relation to the floor is controlled by level. The reliability of fastening the parts to the building base is checked with light blows of a hammer.
The placement of embedded parts for fastening the electrical equipment of the reactor plant is directly related to the arrangement of holes for current supply, made in accordance with the design. With the lower current supply, the connections of the pipes in the plane of the base of each cabinet or each panel, the width and length of the openings (holes) along the panels and their connection in relation to the embedded parts, the possibility of securing pipes for the passage of cables in the openings (to the reinforcement left in the ceiling, or round steel grid with a diameter of 8 mm with cells 130X130 mm) and the dimensions of the pits for connecting cables laid in the cable channel.

In this case, the axes of the outermost embedded parts coincide with the side edges of the shields. When installing one-way service panels leaning against a wall, the row of embedded parts closest to it should be located at a distance of 100 mm. Other distances between embedded parts associated with the construction of service passages are assessed taking into account the requirements of the PUE listed above.
The requirements for other structural elements of the switchgear premises are similar to the requirements discussed in § 2.
In recent years, to accommodate switchgear up to 1000 V, industrial panel electrical rooms (IPEP) and volumetric control stations (OPC), manufactured by the plants of the Ministry of Montazhspetsstroy, have been used. The long time spent by builders on the construction of electrical rooms can be significantly reduced when using IPEP (Fig. 19) and OPU (Fig. 20).

Rice. 19. Industrial panel electrical room:
1 — frame fastening design; 2 — frame frame; 3 - blank wall panel; 4— crossbar; 5 - blind roofing panel; 6 — panel with an opening; 7—support frame; 8 — panel with door block; 9 - panel with window block

Rice. 20. Volume control station:
1 - support with cable shaft; 2— bridge for maintenance; 3 - window opening; 4 - end section; 5 - frame; 6 - intermediate section; 7 - roof panel; 8 - wall panel; 9 - door; 10 - frame

IPEP premises have the following internal dimensions: height 3540, width 3180, 4020, 5110 and 6100 m, length 2400 or more in increments of 1200 mm. IPEPs are supplied complete, but disassembled. The frame of the room is made of U-shaped frames and is connected into a rigid structure by longitudinal crossbars installed at the top and bottom. Wall and ceiling panels enhance rigidity. The main panels have various designs: solid, with a door, a glazed window, an opening for electrical (busbar ducts, boxes and trays with cables and wires) and plumbing communications. Floor panels can be blank or have openings for communications to exit. When configuring the switchgear, doors, windows and openings can be located anywhere, which is very convenient for premises for various purposes. Installation openings can be formed by several panels installed after the electrical equipment.

Distribution device (RU) They call 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 distribution device or a secondary voltage distribution device 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 consumer cable lines.

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;

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 also include DC switchboards that distribute DC current from converters, batteries for powering 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 with their back walls facing each other. KSO cameras 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), and 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 it is permissible to use copper busbars, at rated currents up to 200 A - steel busbars. Installation of auxiliary circuits is carried out with 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 can have different designs, for example, with SF6 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 this case, two scheme options are possible - 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. The ring circuit is more reliable and practical in terms of equipment maintenance and operation.

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Topic: Switchgears up to 1000 V and their operation.

Switchboards, input devices, consoles, shields and other distribution devices of modern designs are complete complete devices for receiving and distributing electricity, controlling and protecting against overloads and short circuits. They contain switching and protective devices, measuring instruments, automation equipment (in some cases) and auxiliary devices. When using complete devices, labor costs for installation are significantly reduced and the performance of networks is improved.

Boards are divided into distribution, control, relay, alarm and control. They are metal structures made up of separate panels, control panels or cabinets on which the instruments and devices provided for by the project are located, as well as busbars and secondary circuit wiring for connecting the installed equipment. Let's look at some types of shields.

Distribution boards are designed for receiving and distributing electricity in networks with voltages up to 1000 V and, depending on the design, are divided into single- and double-sided service, panel and cabinet.

Single-sided service distribution boards (lean-to type) are designed for installation directly next to the walls of the electrical room and for service from the front side. All drives and control handles are located on the façade, and for inspection, maintenance and repair there is a single-leaf door on the back side of the panel. Compared to other shield designs, leaning shields require less area and are more economical.

Single-sided service panels (SSC) are produced in several types and are manufactured in open and closed versions. The first panels are assembled from panels and installed in special electrical rooms, the second ones are made from cabinets with seals and are placed directly in the workshops. Single-sided service panels are made up of standard panels - linear, input and sectional. Linear panels are used to connect electricity consumers to the busbars, input panels are used to connect busbar and cable inputs, sectional panels are used to section (isolate) busbars for rated connection currents. The sides of the outer panels of the shield are covered with end panels with a protective and decorative door.

Panels of all types have a single frame made of bent steel sheets 2-3 mm thick, on which protective and switching protective devices and measuring instruments are installed. All parts for attaching devices are also made from bent steel profiles. The busbar is carried out using flat aluminum busbars on insulators. Busbars are placed at the top of the panel. The main standard panels are produced with a width of 800, a height of 2160 (without a removable cornice - 1950) and a depth of 550 mm.

At present, ShchO-70 switchboards are still widely used (Fig. 1, a, b), the panels and cabinets of which can have different designs, allowing the implementation of switchgears provided for by the design. Both panels and ShchO-70 cabinets have overall dimensions of 2200Х600Х (800-1100) mm and a maximum connection current of 2000 A.

Fig.80. Panels ShchO-70 (a - for four connections, b - input with AVM-20) and PRS (c):

1, 3 - switches with fuses, 2 - current transformer, 4 - traverses with insulators, 5 - switch, 6 - signal lamp, 7 - cornice, 8 - AVM switch

Double-sided (or free-standing) distribution boards are more convenient to use, but require more space. Shields made from PRS panels are widely used (Fig. 1, c). These boards are not protected from above and from behind, therefore they are intended for installation in electrical rooms. PRS panels are similar in height, depth and appearance to control and protection panels, which makes it easier to assemble them together at substations and in machine rooms. They are produced in widths of 600 and 800, height of 2400 and depth of 550 mm.

Standard PRS panels are used to assemble distribution boards for double-sided service with voltages up to 1000 V. The designation of panels, for example PRS-1-15, is deciphered as follows: free-standing distribution, busbar stability 1, panel diagram number 15. Maintenance, repair and connection of devices is carried out from the rear side panels, with the exception of panels with automatic machines that have a single-leaf door. In panels with devices with rated currents of 600 and 1000 A and circuit breakers with 400 A, busbar assemblies are provided for connecting several cables.

Fig.2. Linear cabinet series ШД

Distribution boards for double-sided service are also equipped with standard PD panels and SD cabinets. These panels are more economical in terms of material consumption and are more convenient to manufacture and maintain. PD panels, open at the top and rear, are installed in electrical rooms, and SD cabinets (Fig. 2), closed at the top and rear, are installed in production rooms. Panels made from PD panels and SD cabinets are a complete device, fully connected and configured according to the required circuits. These panels and cabinets can be used to assemble switchgear for package transformer substations. The busbars are located in the upper part for the convenience of directly connecting the side terminals from the transformers to them. Outgoing line protection devices are placed on the facade along the height of the panels in three rows.

According to their purpose, PD panels and SD cabinets are divided into linear, input and sectional. The height of all panels and cabinets is 2200, depth 550, width 600, 800 and 1000 mm. The panels are equipped with fuse blocks - BPV switch, BV switch and circuit breakers for rated connection currents from 100 to 2000 A. ATS relay equipment is placed in the input and sectional panels in a closed cabinet. The fuse-switch unit (Fig. 3, a, b) is a three-phase switching and protective device for rated currents up to 1000 A with a double circuit break, made together with the drive in the form of one device - BPV and BV.

In BPV blocks, switching on and off is carried out by fuse holders PN-2, mounted in the lever drive so that when the latter moves, the cartridges are given a linear movement. In the BV block, instead of fuse holders, copper knives are installed. The body of the unit is made of thin sheet steel and consists of a façade frame 1 with a door, two sidewalls and a plate 6 for installing insulators 5 with racks 4 of fuses 2. The drive is located on the body.

Fig.3. Fuse block - switch series BPV:

a - front view, b - side view; 1 - facade frame with door, 2 - fuses, 3 - drive handle, 4 - contact stand, 5 - insulator, 6 - plate

The units for installation in drawers and cabinets are equipped with a lock that prevents the door from opening when the door is on and from being turned on when the door is open. A locking device release is also provided, allowing fuses to be turned on and off for inspection and testing with the door open.

Input distribution devices (IDUs) are designed for receiving and distributing electricity and protecting outgoing lines in three-phase 380/220 V networks with a solidly grounded neutral. The most common devices are VRU-70, the panels and cabinets of which can have different designs that allow you to assemble the switchgear provided by the project.

Input distribution devices are made in the form of single- and double-sided service panels, as well as cabinet type. The configuration of the ASU series is carried out in different ways, for example, in one of the series there are three types of input and 28 types of distribution cabinets.

A typical entrance cabinet is a metal structure (overall dimensions 1700X800X500 mm), on the frame of which a frame with equipment is mounted. In a typical distribution cabinet (in the upper part in a separate compartment) metering equipment, switching devices and lighting control are located. Wires and cables are entered from below, and output is carried out both from below and from above through the upper removable cover. At the base on which the ASU is installed, cable channels or pits are made. The bottom frames of each panel have four holes for fastening with bolts, pins, etc. The panels are also connected to each other with bolts. After installation, alignment and final fastening of the panels and the device as a whole, the panel housings are grounded by connecting the neutral conductors of the supply cables to the neutral bus, common to all panels.

Input distribution devices VRU-70, the overall dimensions of which are 2000X 500X (450 ~ 1100) mm, have some features. They do not have top or back closures. VRU-70 panels (Fig. 4) are installed in electrical rooms against the wall, and for installation in a production room they are equipped with a lockable front door and rear wall.

Rice. 6. VRU-70 panel with two switches: 1 - PB switch, 2 - PN-2 fuse, 3 - current transformer, 4 - counter, 5 - test panel

Rice. 4. Floor shield

Distribution boards, points, cabinets

Group distribution panels for lighting are complete devices for switching and protecting lighting networks. They produce shields for residential buildings and general purposes, intended for industrial and civil buildings. Panels for residential buildings (storey, apartment and combined) are manufactured in various modifications.

The floor panel (Fig. 5) is made in the form of a frame with a chassis and a door. The chassis is equipped with protective and switching devices and clamps with connections made within the panel. Apartment panels have meters and devices for protecting group lines of the apartment network, if they are not located on the floor panels.

For electrical installations of industrial enterprises and public buildings they produce: group panels of the SU-9400 series (Fig. 6, a), points S-9500 and distribution points PR-9000 (Fig. 6, b) with one- and three-pole installation machines in a protected design , lighting panels of the OP, OSCH and OSCHV series in a protected design with automatic circuit breakers for 6 and 12 groups, panels of the UOSCHV series for 6 and 12 single-phase groups, designed for receiving and distributing electricity and protecting against overloads and short-circuit currents. lines of lighting networks 380/220 V with a solidly grounded neutral.

The shield is a steel box, inside of which the equipment is mounted on a removable chassis.

switchgear operation panel

Fig.6. Panel with installation machines SU-9400 (o) and power distribution point PR-9000 (b)

The handles of the machine guns are located on the front of the panel and closed with a door. There is a bolt on the side wall of the housing for connection to the grounding network. The top and bottom covers are removable. To enter a cable or pipe, remove the cover and press holes in it.

Power distribution cabinets SP and ShRS are used to distribute electricity and protect circuits from overloads and short circuits. One or two switches or a switch with fuses are provided at the cabinet input, and fuses are provided at the outgoing lines.

Operation of switchgear equipment

Inspections of switchgears (RU) are carried out with the following frequency: at facilities with permanent personnel duty - at least once a day and at least once a month in the dark to identify discharges and corona; at sites without permanent staff duty - at least once a month. Additional inspections are carried out in unfavorable weather (fog, heavy wet snow, ice). Objects in areas of intense pollution should also be inspected additionally.

During inspections of the reactor plant, the following is checked: the oil level, its temperature and the absence of leaks in oil-filled equipment; condition of the contact connections of the busbar; insulation condition (dirty, presence of cracks, chips, traces of dew); compliance of the position indicators of switching devices with their actual position; condition of openly laid conductors of the grounding device; operation of equipment heating devices in the cold season. Availability of fire extinguishing equipment, portable grounding and other protective equipment, and a first aid kit.

When inspecting closed switchgears, they additionally check: the condition of the premises, heating, ventilation, lighting, the condition of the roof or interfloor ceilings, the presence and serviceability of doors and locks. In SF6 reactor plants, the humidity and pressure of SF6 gas in the equipment and the concentration of SF6 gas in the room of closed switchgears are additionally checked. Defects and malfunctions noticed during inspections must be eliminated during the next repair; emergency defects must be eliminated as soon as possible.

Contamination of the surface of insulators of switchgear equipment poses the greatest danger during drizzling rain, fog or dew, when the contaminating layer becomes conductive. This can lead to discharges on the surface of the insulators and their overlap. Therefore, it is important to promptly clean the switchgear insulation from contamination and treat the insulators with hydrophobic pastes that have water-repellent properties. All rubbing parts of the mechanisms of switching devices and their drives must be periodically lubricated. Lubricants that work effectively at low temperatures are used. Electric heating devices for drives of switching devices, control cabinets, relay protection and automation must operate, as a rule, in automatic on and off mode. When operating switchgears, the following preventive measurements and tests, common to all equipment, are performed:

1. Measuring the resistance of the main insulation of equipment (insulation of primary circuits) with a 2500 megohmmeter.

Measuring the insulation resistance of secondary circuits with a 1000 V megohmmeter; this resistance must be at least 1 MOhm; The insulation test of secondary circuits is carried out with a voltage of 1 kV for 1 minute. Thermal imaging control of switchgear equipment.

Repair of reactor plant equipment is carried out as necessary, taking into account the results of inspections and preventive tests.

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