Control panel and switchgear assemblies

Where are these assemblies used?

Control and switchboards are found in power plants, transformer stations, distribution substations, commercial and institutional buildings, factories and industrial establishments, refineries, paper mills, metal smelters. and any other place where electrical energy is used or electrical energy distributed in any number of zones.c

There are a few common types of assemblies that cover almost any application. A broad classification based on the location of switchgear assemblies is whether the equipment is installed indoors or outdoors.

Another classification for indoor equipment is standard ventilation for indoors, interior with drip guard, for interior in sprinkler areas, for interior in hazardous areas, sheltered arc (type a, b or c) and for indoor use in a corrosive environment. Outdoor gear can also be classified according to whether or not it has an island (types entered) with or without a work area.

Another method of classifying the switchgear is to determine whether it is a bottom or top entry , the power and control cables enter from the bottom or the top of the gear.

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Switchgear devices

The switchgear may contain as switching / interrupting device (s): a circuit breaker (cb), a switch / fuse combination, a contactor / fuse combination (for switching the motor), for low voltage assemblies (lv) : a switch or circuit breaker in series with a contactor (for switching the motor).

Some setups only come as unfolded construction, others as ripped. If special requirements for the material are necessary, the special property can be used as the criterion for defining the gear. For example, if a dust-tight enclosure is required due to the presence of dust (fine or thick) in the atmosphere, this equipment is designated as dust-tight.

switchgear assemblies
switchgear assemblies

For switching assemblies, the heat generated in view of the high flowing current, a dust-proof enclosure is almost impossible, which is why a dust-proof seal is used. The main standards governing the design, manufacture and testing of these assemblies are: CSA , ANSI , IEC , EEMAC , NEMA .

Alignments of switching assemblies and motor control centers (starters) can be classified according to their voltage classes. The lv equipment is rated in the range of 120/208 V single phase or three phase to 750 V AC. Average voltages are 2400 / 4160V to 44KV. The housings of all low voltage constructions are made of metal. Some constructions include bulkheads and barriers for safer operation in addition to the standard construction.

For medium voltage switchgear, the two types of construction, metal sheath and closed metal , are common. In this section, the main components of switchgear assemblies, motor starters and associated auxiliary accessories will be indicated.

Major components

Low voltage switchgear assemblies

The main components are:

  • Molded case (MCB) or power (magnetic air) circuit breakers (withdrawable or fixed) with or without integrated protection device against overcurrents (thermomagnetic,
  • Solid state or microprocessor based) with or without zone lockout provision
  • Cradle (only for withdrawable versions)
  • Fixed potential and control transformers
  • Current transformers
  • Interframe and rear barriers
  • Main bus bars, passageways, bus risers and cable lugs (compression or mechanical)
  • Protection fuses for circuit breaker control circuits, instrument compartments
  • Circuit breaker accessories, circuit breaker lifting devices (built into gear)
  • Fuse switches or not
  • Auxiliary protection and monitoring relays
  • Metering devices (ammeters, voltmeters, water meters, wattmeters and DMP digital metering boxes)
  • Control switches and indicator lights

Medium voltage switchgear

The main components are:

  • Withdrawable circuit breakers ( oil, air, SF6, vacuum )
  • Switching device ( load break or disconnection ) with or without fuses ( current limiting or power expulsion type ) with or without fuse / actuator indicator
  • Instrument transformers
  • Capacitor Trigger Device
  • Relays
  • Meters and instruments
  • Main bus
  • Controls and indicators, jumpers, cable lugs, cable holders and potholes
  • Barriers and shutters
  • Instrument compartments
  • Circuit breaker testers and accessories

Low voltage motor control centers

For LV motor control centers, the components are:

  • Combined starters
  • Instrument transformers
  • Motor protection devices
  • Main bus, cable entry compartments, vertical bus, control cables
  • Push buttons, indicator lights
  • Circuit breaker or switch handle
  • Mounting plates
  • PLC programmable controllers (processor module, I / O, network interface and other associated modules)

Medium voltage starters

For MV starters, the main components are:

  • Contactors ( vacuum and air )
  • Fuse control transformer
  • Overload protection
  • Current transformers
  • Instrument compartments
  • Meters
  • Auxiliary relays
  • Timers
  • Control devices
  • Multifunction motor protection relay
  • Indicator lights
  • Power fuses
  • Surge arresters

Types of switching cells

There are a few distinct types of switch cabinets and are listed below:

  • Entrance ( main ) of cabins
  • Transformers
  • Bus tie ( sectionalization )
  • Checking the generator exciter
  • Neutral generator cells
  • Induction motor control cell
  • Synchronous motor switching board
  • Potential transformer cabins ( used in conjunction with an isolated phase bus in power plants ).

Other visible or attached components Power transformers, low voltage / medium voltage bus ducts, or cable ducts connected to switching lines to form a subunit or not.

If the transformers are tightly coupled and installed indoors, dry type transformers are used. If they are located outside and connected to the switchgear by an unseparated bus or cable conduit, or by a groove (with O / D switchgear), they are of the oil type.

Another type of transformer that can be found inside is the resin cast coil type.

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