Switchgear refers to an amalgamation of electrical switching devices whose function is to switch, control, meter, regulate, isolate, and protect electrical circuits and equipment. Some of the products encompassed within the switchgear include switches, circuit breakers, switch fuse units, contractors, H.R.C. fuses, offload isolators, and earth leakage circuit breakers (E.L.C. Bs). These devices are assembled in a logical manner to form the switchgear. The switchgear may be used to clear faults downstream as well as de-energize equipment so that work can be done. This equipment has direct linkage reliability of the supply of electricity.
Components of Switchgear
Switchgear comprises protecting and switching devices that include fuses, switches, circuit breakers, isolators, control panels, relays, current transformers, potential transformers, control panels, and other associated equipment.
Some of the equipment is designed to operate under abnormal and normal conditions. Some of the equipment is also designed only to serve the role of switching; hence cannot sense faults. Switchgear facilitates switching generators, distributors, transmission lines as well as other electrical equipment on or off.
In the event of failure on any part of the system such as a short circuit, heavy current flows through the equipment, thus posing a potential threat to the equipment as well as causing interruption of service. When this happens, the switchgear will detect the existing fault before disconnecting the unhealthy section from the rest of the system.
Evolution of the Switchgear
The switchgear is mainly used to interrupt and switch currents under abnormal or normal operating conditions. The simplest form of switchgear that you can find is the tumbler switch that is not only used in controlling and protecting lights but other equipment in the office or at home as well. In the case of circuits that have a higher rating, a high rupturing capacity (H.R.C.) fuse and a switch may be used to protect and control the circuit. Even then, switchgear may not be profitable in high voltage systems of up to 33kV because of two reasons:
In advanced power systems, the equipment and lines carry high current and operate at high voltage; thus, the occurrence of a short circuit can lead to massive damage. As such, the heavy currents are interrupted by heavy fault currents.
Essential Features of Switch
Here are some of the critical features of switchgear:
Classification of Switchgear
Switchgears are classified according to the voltage level. Thus, there are three main categories of switchgear as follows:
Switchgear and Protection
Fuses that can be rewired and low voltage switches are used to close and open the electrical circuit manually in the home where the electrical fuse protects the household’s electrical circuit from short circuit faults as well as over current.
Consequently, electrical circuits that include high voltage electrical power systems require protective devices and switching. However, in extra-high-voltage and high voltage systems, the protective and switching schemes can get too complicated for the high fault current interruption securely and safely.
Additionally, from a commercial viewpoint, electrical power systems require measuring, regulating, and control arrangement. This entire system is collectively referred to as the switchgear and protection of the power system. Thus, electrical switchgear has developed in various forms.
Switchgear protection plays an essential role within the modern network of the power system from generation to transmission and distribution. The device that is used to switch or interrupt the flow of current in the switchgear protection system is referred to as a circuit breaker that may also be operated manually. The circuit breaker senses faulty conditions in the system through protection relay where the relay is actuated by a faulty signal from the voltage transformer or current transformer.
Apart from the power system network, switchgear may also be required in industrial projects, industrial works, commercial and domestic buildings.
LV Switchgear
Low voltage switchgear refers to electrical switchgear that is rated to 1kv. Thus, the term LV switchgear collectively refers to H.R.C. fuses, low voltage circuit breakers, offload electrical isolators, switches, earth leakage circuit breakers, molded case circuit breakers (MCCB) and miniature circuit breakers (M.C.B.). That is, all accessories that are required in protecting the LV system. The LV switchgear is mainly used in the LV distribution board. The system is made up of the following parts:
The Basic Functions of LV Switchgear
The role of the LV switchgear includes the following:
Working of LV Switchgear
How to inspect, test and measure LV switchgear
Here are some general inspection and maintenance timelines for low voltage switchgear:
For testing and maintenance of low voltage switchgear, the following timelines must be observed:
MV Switchgear
A switchgear system that is capable of handling between 3kv and 36kv is referred to as Medium Voltage Switchgear. These come in many types, such as metal-enclosed outdoor type, metal-enclosed indoor type, as well as an outdoor type without metal enclosure, among others.
The mode of interruption of this switchgear can be S.F., oil, and vacuum with the main requirement of the medium power network being interrupting current whenever there is a fault condition regardless of the type of C.B. that is used by the MV switchgear system.
The Functions of MV Switchgear
Medium voltage switchgear should be able to perform the following functions:
Ultimately, all the functions mentioned must be undertaken with a high degree of reliability and safety.
Working of MV Switchgear
How to inspect, test and measure MV switchgear
Different components that make up the MV switchgear need to be inspected as part of the routine maintenance. Usually, the inspection and maintenance take place after a defined period as follows:
Testing and Maintenance
In terms of testing and maintenance, the acceptable durations after which the system should be subjected to testing and maintenance is as follows:
Busbar Systems
Restoration
Importance of Routine Checks and Regular Maintenance of Switchgear
When switchgear is installed in an environment that is air-conditioned, well ventilated, and clean, it does not need much maintenance. However, significant inspections are necessary when the plant is shut down. Inspections usually include:-
A lot of concentration must go into checking protective devices, contact distances of the vacuum bottles, and the oil levels within the circuit breaker to ensure that they are all in line with the specifications of the manufacturer.
Even then, exemptions may be given to the switchgear that operate frequently and whose maintenance is dependent on the overall hours of operation. Additionally, care must be taken to ensure that the MV switchgear insulation and the contractual circuits are in place. The gas-insulated switchgear is another exemption that should be maintained according to the specifications of the manufacturer. Consequently, extensive maintenance should be supervised by the manufacturer. If the switchgear is aged, conditional assessment needs to be done to determine if the devices can operate further.
Where LV/MV switchgear applications are used
Switchgears may be used in different areas that include the following:
Overall, electric energy is a vital part of life. Therefore, electricity distribution must be done in a manner that is secure and safe. Security levels can be maintained at the different distribution units as well as substations through the installation of safety mechanisms and devices. Although numerous mechanisms can help safeguard electrical connections in industrial and residential areas, the use of switchgear is recommended because of its features and functions.
D&F Liquidators has been serving the electrical construction materials needs for more than 30 years. It is an international clearinghouse, with 180,000 square facility located in Hayward, California. It keeps an extensive inventory of electrical connectors, conduit fitting, circuit breakers, junction boxes, wire cable, safety switches etc. It procures its electrical materials supplies from top-notch companies across the globe. The Company also keeps an extensive inventory of electrical explosion proof products and modern electrical lighting solutions. As it buys materials in bulk, D&F is in a unique position to offer a competitive pricing structure. Besides, it is able to meet the most discerning demands and ship material on the same day.
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