Switchgear
Switchgear is the combination of switching, protection and isolation devices, such as circuit breakers, disconnectors, earthing switches, fuses, protection relays and instrument transformers, assembled in metal enclosures to control, protect and isolate electrical equipment. It energizes and de-energizes circuits for operation and maintenance and automatically clears faults to limit damage and maintain supply to healthy sections. Low-voltage switchgear and controlgear assemblies are covered by IEC 61439, while medium- and high-voltage equipment falls under the IEC 62271 series, including IEC 62271-200 for AC metal-enclosed switchgear above 1 kV up to 52 kV. Insulation may be air (AIS) or gas (GIS). Selection parameters include rated voltage, rated normal current, short-time withstand current and duration, busbar arrangement, form of internal separation (LV), internal arc classification (IAC), IP rating and the protection and control scheme.
Examples
- 11 kV air-insulated switchgear lineup for a plant substation
- Gas-insulated ring main unit in a distribution network
- Low-voltage main switchboard with withdrawable air circuit breakers