Following intensive R&D, Siemens exhibits high voltage interrupters and gas-insulated switchgear using vacuum technology and so-called clean-air technology up to a voltage of 145 kV for the first time ever at this year's Cigré in Paris. The launch of the new outdoor circuit-breaker 3AV1 and 8VN1 Blue GIS is scheduled in 2018.
The Council on Large Electric Systems (Cigré), founded 1921, this week gathered more than 3 500 experts in Paris to exchange knowledge, share best practices and join forces for the ‘Power System of Today and Tomorrow.’so
Exhibiting at the event, Siemens is showcasing a vacuum interrupter unit that performs switching and arc extinguishing activities. Clean air – processed and purified air with an 80:20 ratio of nitrogen and oxygen – provides the insulation for the current-carrying conductors inside the housing of the metal-encapsulated GIS.
Dry air used for insulation
With vacuum switching technology, when the contacts are opened the switching arc burns in a metal-vapour plasma between the contacts inside the vacuum extinction chamber. The metal vapour condenses back onto the contacts after the arc is extinguished.
No decomposition products occur and the arc does not affect the surrounding insulation. This means that natural insulating gases such as dry air (clean air), nitrogen or carbon dioxide that only have poor arc extinction properties, if any at all, can be used for high-voltage insulation of current-carrying conductors.
“The combination of vacuum interrupter units up to 145 kV for arc extinction and clean air as high voltage insulating medium offers an additional alternative to sulphur hexafluoride (SF6) to supplement the existing insulating and arc extinction technology, explained Karlheinz Kronen, CEO of high voltage products, part of Siemens Energy Management.
Vacuum switching up to 145 kV
Siemens has used vacuum switching technology for more than 40 years in its medium voltage switchgear as well as in high-voltage circuit-breakers up to 72.5 kV.
With the new circuit-breakers and switchgear, Siemens is extending the use of vacuum switching technology up to a rated voltage of 145 kV, a rated short-circuit breaking current up to 40 kilo-amperes (kA), a rated current of up to 3150 A and operating temperatures from -55°C up to +55°C.
Siemens' Energy Management division offers utilities an industrial power producers and solutions for the transmission and distribution of electricity; its nearly 53,000 employees earned approximately €11.9 billion in sales and €570 million in profit in the last fiscal year, ending September 30, 2015.