Influence of interrupted current amplitude on the post-arc current and gap recovery after current zero-experiment and simulation

For commercial vacuum circuit interrupter valves with radial field contact, the post-arc current (PAC) waveform was measured after short circuit current interruption applying a transient recovery voltage (TRV) of about 15 kV/s (RRRV). Keeping the current decline di/dt at current zero constant, the power frequency (PF) current amplitude I/spl circ//sub PF/ was varied from 0.5 up to two times of the rated short circuit current. Significant influence of I/spl circ//sub PF/ on the gaps memory is shown in particular effecting the post-arc current duration which varies in a range between 2 and 8 /spl mu/s. Based on the existing physical models an interpretation of the results is given. It is shown that the memory effect influences the gap recovery time. The experimental results were further used to determine the parameters of the sheath growth model described by Andrews and Varey (1971). The initial ion density is fitted according to the current ramp di/dt before current zero (CZ) and according to the measured Q/sub PF/=/spl int/i/sub PF//spl times/dt during the arcing phase. The results of two different test procedures were applied in order to separate the effect of current ramp di/dt and Q/sub PF/=/spl int/i/sub PF//spl times/dt. The influence of both parameters and of the rate of rise of the recovery voltage du/dt (RRRV) on the sheath edge velocity could be demonstrated by simulation.