The German firm said while millions of vacuum interrupter units are used in medium voltage switchgear worldwide, until now they have come up against their limits in the high voltage sector above 72.5 kilovolts (kV).

With the latest technology, a vacuum interrupter unit works on the processes of switching and arc extinguishing activities.

The company said technically processed and purified air with a mixing ratio of 80% nitrogen to 20% oxygen offers the insulation for the current-carrying conductors inside the housing of the metal-encapsulated, gas-insulated switchgear (GIS).

According to Siemens, the new outdoor circuit breaker 3AV1 and new switchgear 8VN1 Blue GIS with vacuum switching technology and clean-air insulation are expected to be launched in the market in 2018.

Its older circuit-breakers and switchgear systems using sulfur hexafluoride SF6 have been further developed into the new switchgear system.

Siemens says that the expansion of its switchgear and vacuum switching technology help in meeting climate neutrality requirements.

Siemens Energy Management Division, business unit high voltage products CEO Karlheinz Kronen said "With this technology, we are expanding our high voltage portfolio and offering our customers an alternative solution without SF6 for higher voltage levels as well.

“The use of technical switching and insulating gases with high global warming potential can be reduced or even avoided completely in many application areas with the help of vacuum switching technology."

With the new technology, when the contacts are opened, a switching arc burns in metal-vapour plasma between the contacts inside the vacuum extinction chamber. The metal vapour condenses back onto the contacts after the arc gets extinguished.

Using technical insulated gases which should be able to insulate live parts as well as extinguish arcs can be completely avoided by using vacuum switching technology.

By combining vacuum interrupter for 145kV for arc extinction and dry air as high voltage insulating medium can offer an additional alternative to sulfur hexafluoride to supplement the present insulating and arc extinction technology.

Siemens exhibited this new technology at Cigre in Paris this year.

Image: With this technology, Siemens expands its high voltage portfolio and offers an alternative solution without SF6 for higher voltage levels as well. Photo: Courtesy of Siemens AG.