Switchgears are used in electric power systems with the purpose to control, protect and isolate electric equipment. In distribution nets, switchgears are located both on the high voltage side and the low voltage side of power transformers.
Switchgears used today for medium voltages are usually gas insulated switchgears, where the insulating gas is sulfur hexafluoride (SF6). The use of SF6 allows for a compact design of the switchgear since SF6 has excellent arc extinguishing, electrical insulating as well as thermal dissipating properties.
Despite the many advantages of SF6, alternatives thereto have recently been introduced due to the high global warming potential (GWP) of SF6.
WO2014154292 A1 discloses a SF6 free switch assembly and switchgear where a vacuum breaker is mounted to a single electrically conductive housing.
U.S. Pat. No. 8,232,496 B2 and U.S. Pat. No. 7,767,917 B2 disclose puffer type load break switches. In the disconnected position, separate field controllers electrically screen moving and stationary contact sets. These switches have thermoplastic enclosures for the actuator mechanisms and are primarily intended for use with SF6 as dielectric insulating medium.
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