Features of the Siemens vacuum switching technology

Constant dielectric

  • The hermetically closed vacuum interrupters are insensitive to environmental influences

  • Switching processes in the vacuum do not produce any decomposition products as this is the case with SF6 circuit-breakers


Constant contact resistance

  • As there is no oxidation in the vacuum, the contact surfaces remain metallically pure

  • The very small contact resistance prevails throughout the entire service life

  • Separate main and arcing contacts, such as required for SF6 circuit-breakers, are not necessary


Suitable for all switching duties

  • Small chopping currents

  • Free of restrikes

  • Breaking of highest normal and short-circuit currents


Economic advantages

  • Vacuum interrupters are maintenance-free

  • Modern vacuum circuit-breakers are maintenance-free up to 10,000 operating cycles


High reliability of vacuum circuit-breakers

  • Low number of moving parts inside the arcing chamber

  • Extremely high mean-time-to-failure (MTTF) values of the vacuum interrupters


Minimum use of plastic material in vacuum circuit-breakers

  • Air is the main insulator

  • Avoidance of creepage paths and partial discharges


Safety first

  • In the extremely unlikely case of loss of vacuum, an arc develops, but there is no explosion as the current is interrupted inside a ceramic-metal housing


Vacuum switching technology established on the market

The exceptional economic and technological aspects of the vacuum quenching principle have made the vacuum circuit-breaker the device that is mostly used worldwide for voltage ratings from 1 kV to 52 kV. Siemens offers a wide range of vacuum circuit-breakers for generator switching.

Over 40 years of experience in vacuum switching technology

With comprehensive simulations, preliminary studies, state-of-the-art development technologies, and modern manufacturing processes, Siemens sustainably maintains its leading position in the field of vacuum circuit-breakers. In particular, Siemens has perfected its vacuum circuit-breakers for generator switching applications, where they are subjected to high thermal and mechanical stress. Application of the proven vacuum switch­ing technology is thus possible with ever increasing ratings.
Characteristics:

  • Special contact material for minimum contact wear

  • Specifically developed contact system

  • Optimized design for efficient cooling

  • Post insulator construction for highest mechanical stability

  • Safe breaking operations by controlling long arcing times even in case of missing zero crossings

  • Transient recovery voltages with high rates-of-rise, typical for generators, are controlled without additional capacitor circuits