Electrical switchgear is a centralized collection of circuit breakers, fuses, and switches (circuit protection devices)that protects, control, and isolates electrical equipment in an industrial electrical box. Metal structures support the circuit protection devices. A switchgear line-up or assembly is a combination of one or more of these structures.
Switchgear can be found in a variety of places, including electric utility transmission and distribution systems, as well as medium to large commercial and industrial buildings. IEEE defines electrical switchgear standards in North America, while IEC defines them in Europe and other parts of the world.
In this article, we take a detailed look into the definition of MV switch gears, types of medium voltage switchgear, and their application. Let’s get started.
From 3 KV to 36 KV switchgear system is designated as medium voltage switchgear or MV switchgear. This switchgear is of numerous varieties. They may be metal-enclosed indoor type switchgear, metal-enclosed outdoor type switchgear, outdoor type switchgear without metal enclosure, from enclosure manufacturers.
The switchgear’s interruption medium could be insulating oil, SF6 gas, or vacuum. Regardless of the type of CB provided by the electrical switchgear manufacturer system, the basic requirement of the power network is to interrupt current during a fault state. It could, however, work in other situations.
Circuit protection devices distribute power to different areas of a facility as well as the electrical loads inside those areas. They also protect people and equipment throughout the facility by restricting the amount of current flowing through the system to safe limits.
Gas-insulated switchgear (GIS) has a sealed enclosure(s) filled with insulating gas sulfur hexafluoride (SF6) or a mixture of SF6 and other recently released insulating gases. The gas-filled sealed container allows for a low-profile, compact installation. When compared to identical air-insulated switchgear, the use of gas as an insulating medium allows for a greater distance between interruptions.
Circuit breakers, power fuses, and fusible switches, as well as control and metering equipment, are all contained in metal-enclosed switchgear. These devices can be installed in common compartments without the need for separate barriers or compartmentalization that metal-clad switchgear requires. Metal-enclosed switchgear is used in a variety of commercial and industrial settings with incoming electrical service above 480V/600V.
Pad-mounted switchgear is designed for underground distribution systems with a voltage range of 5 to 38 kV that must be operated above ground. Pad-mounted switchgear is appropriate for utility distribution, feeder sectionalizing, and circuit protection applications due to its outside rated, low profile, and a tamper-resistant design. Air, SF6 gas, fluid, solid-dielectric-in-air technology, and solid materials can all be used as insulation.
IEEE C37.74 defines vault or subsurface switchgear. Vault or subterranean switchgear is designed for 15 to 38 kV electrical distribution systems that require the switch and its accessories to be operational from inside a vault or below-grade site. These areas may be dry or prone to water intrusion.
Vacuum interrupters are used to protect loads and isolate faults in vault or subsurface switchgear that allows the user to activate the switch from above ground manually or with the use of relays. SF6 gas, solid-dielectric-in-air technology, and solid solids are all examples of insulation methods.
An electric arc furnace must be turned off and on regularly. The current to be switched might range from 0 to 8 times the furnace’s rated current. For this frequent activity, a standard SF6 circuit breaker, air circuit breaker, or oil circuit breaker is not cost-effective. For this frequent high current circuit breaker activity, a standard vacuum circuit breaker is the best option.
A single-phase railway track system is another application of medium voltage switchgear. The circuit breaker in a railway traction system’s principal role is to interrupt a short circuit on the overhead catenary system, which happens frequently and is temporary.
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