Editing Switchgear (section)

{{Use dmy dates|date=July 2023}}
{{Short description|Control gear of an electric power system}}
[[Image:High-voltage switchgear 01.jpg|thumb|[[High-voltage switchgear]]]]
[[Image:IndustrialSwitchgear.JPG|thumb|A section of a large switchgear panel.]]
[[Image:Tram switchgear.JPG|thumb|Tram switchgear]]
[[Image:Hybrid switchgear.jpg|thumb|This circuit breaker uses both SF<sub>6</sub> and air as insulation.]]

In an [[electric power system]], a '''switchgear''' is composed of electrical disconnect switches, [[fuse (electrical)|fuse]]s or [[circuit breaker]]s used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear [[fault (power engineering)|fault]]s downstream. This type of equipment is directly linked to the reliability of the [[electricity]] supply.

The earliest central power stations used simple open [[knife switch]]es, mounted on insulating panels of [[marble]] or [[asbestos]]. Power levels and voltages rapidly escalated, making opening manually operated switches too dangerous for anything other than [[Galvanic isolation|isolation]] of a de-energized circuit. Oil-filled switchgear equipment allows arc energy to be contained and safely controlled. By the early 20th century, a switchgear line-up would be a metal-enclosed structure with electrically operated switching elements using oil circuit breakers. Today, oil-filled equipment has largely been replaced by air-blast, vacuum, or [[sulfur hexafluoride|SF<sub>6</sub>]] equipment, allowing large currents and power levels to be safely controlled by automatic equipment.

[[High-voltage switchgear]] was invented at the end of the 19th century for operating [[Electric motor|motors]] and other electric machines.<ref>[http://v3.espacenet.com/origdoc?DB=EPODOC&IDX=GB189320069&F=0&QPN=GB189320069 British Pattern GB 20069 ''Improvements in Apparatus for Controlling the Application or Use of Electric Currents of High Tension and Great Quantity'' in 1893], on espacenet.com</ref> The technology has been improved over time and can now be used with voltages up to 1,100&nbsp;kV.<ref name="1100kV">Lin Jiming et al., ''Transient characteristics of 1 100 kV circuit-breakers'', ''International Symposium on International Standards for Ultra High Voltage'', Beijing, Juillet 2007.</ref>

Typically, switchgear in [[Electrical substation|substations]] is located on both the high- and low-voltage sides of large power [[transformer]]s. The switchgear on the low-voltage side of the transformers may be located in a building, with medium-voltage circuit breakers for distribution circuits, along with metering, control, and protection equipment. For industrial applications, a [[transformer]] and switchgear line-up may be combined in one housing, called a unitized [[electrical substation|substation]] (USS). According to the latest research by Visiongain, a market research company, the worldwide switchgear market is expected to achieve $152.5 billion by 2029 at a CAGR of 5.9%. Growing investment in renewable energy and enhanced demand for safe and secure electrical distribution systems are expected to generate the increase.<ref>{{Cite web|url=https://www.visiongain.com/the-worldwide-switchgear-market-is-expected-to-achieve-152-5bn-by-2029-says-visiongain-report/|title="The worldwide switchgear market is expected to achieve $152.5bn by 2029", says Visiongain report|date=2019-09-05|website=Visiongain|language=en-US|access-date=2019-09-06}}</ref>