Research on the reignition condition for DC arc forcing interruption

The characteristics of arc quench time, overvoltage and reignition condition in forcing interrupt 270V DC system with vacuum switch was investigated in this paper. The experiment focused on the Magnitude of the interruption current in DC vacuum arc, variation rate of the current and voltage at zero passage (di/dt, dv/dt), and their influence in the reignition was analyzed. The di/dt was influenced by the parameters in forcing circuit, while the dv/dt not only influenced by the frequency modulation circuits but also the parameters in forcing circuit. The overvoltage contains two type of different frequency waveform, and depended on the precharged voltage and inductance. In the experiment, three types of reignition situation were found, and the reignition was undiscovered under 450A even with the dv/dt at 2000V/us. With the current increase from 540A to 1600A, the dv/dt at reignition decreased, and the time between peak voltage and reignition point decreased too, from 850ns to 50ns. While in the test, the reignition became very easy above 2100A. Finally the test gap and frequency-modulation of TRV was also researched. Large gap (3mm) and low TRV will be useful to prevent the arc reignition.