A new black-box model of SF6 breaker for medium voltage applications

An electro-mechanical model of a SF6 circuit breaker for medium voltage applications, i.e. for voltages up to 36 kV and short circuit currents up 50 kA is presented. The model is developed by starting from the well known Schwarz-Advonin arc model with the addition of the mechanical effects on the arc geometry and of the “puffer”. The puffer can blow the arc during its full duration and mainly during current zero crossing to extinguish it. This action is carefully exploited by breaker designers and often is the key aspect to obtain arc extinction in high current conditions.