Development and Experimental Evaluation of 2 -10 kV LC DC Circuit Breaker Module

The article analyses design options for a practical 2-10 kV, 1-2 kA LC DC Circuit Breaker module. The impact of multiple series break points with the ultra-fast disconnector is explored in depth using analytical model and 5 kV, 4-break
hardware prototype. The experimental testing demonstrates that the arc voltage increases proportionally with each breaking point, and this increases current that can be internally commutated. Further analysis of the impact of delays between break points is presented. Modeling and testing with 4 different capacitors of 1-10 kV concludes that larger capacitances increase commutating current, but relationship is complex and non-linear. Parallel connection of breaking points is also analysed. Successful breaking of DC fault current is demonstrated on hardware for multiple cases including 930 A with 800 µF, 6.5 kV, capacitor using a 4- break disconnector. The tested DC CB is of mechanical type, which inserts a capacitor in series in a very short time of around 290 µs, and full contact separation is achieved 1.5 ms after the trip signal. It is recommended that the module design should primarily consider maximizing the number of break points in series.