HOW IS SAFE IS YOUR VACUUM CIRCUIT BREAKER?
WHAT IS VACUUM CIRCUIT BREAKER??
A vacuum circuit breaker uses vacuum as an arc extinction medium.?It is simply made of a fixed and moving conductors surrounded by a permanently sealed vacuum interrupter.?Because the voltage breakdown of vacuum is huge, i.e. about 10^12 Mv/m, it provides an excellent insulation and environmentally friendly characteristics. It is expected to replace SF6 circuit breakers for voltages up to 230 kV with almost no maintenance required.?However, it is very sensitive to the distance between the conductors and as such it can actually break if the distance is not optimized for worse case scenarios.?
Vacuum circuit breaker?
3D CAD model of the vacuum circuit breaker built inside SOLIDWORKS?
Electric field plots – high spot is noticed in the gap between the terminals?
Animation of the electric field versus the distance between the terminals?
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Voltage plot?
THE SAFETY FACTOR?
By borrowing from structural engineering, EMWorks’s low frequency popular package, EMS, introduced a safety factor that can be handy for designing vacuum circuit breakers.?The safety factor is calculated by taking the ratio of the electric field strength at the center of each tetrahedral element in the vacuum to the breakdown of vacuum, i.e.?10^12 Mv/m.?The safety factor distribution is then plotted on the entire mesh which clearly shows the smoky regions where the value exceeds 1.0, i.e. vacuum breaks down.?EMS is conveniently equipped with a parametric study feature which can readily be used to quickly vary the distance between the conductor for the worst case scenario voltage, i.e. the largest voltage, and determine if and when a breakdown occurs.
Iso plot of the Safety Factor - 1 mm gap?
Animation of the Safety Factor results versus the gap between the conductors?
?SUMMARY AND TAKEAWAYS?
The vacuum circuit breakdown is an excellent breaker which can handle voltages up to 230 kV.?However, it can fail if the distance between the conductors is too small.?To quickly test such failure, use EMS and its novel safety factor.?