Post-arc Dielectric Recovery Characteristics of Free-burning Ultrahigh-Pressure Nitrogen Arc

This work contributes to the fundamental understanding of post-arc dielectric recovery characteristics of free-burning nitrogen arcs as a function of gas filling pressure. Arc peak current of 425 A at a frequency of 925 Hz is used throughout the experiment. The arc burns freely between two fixed electrodes without any forced gas flow. Three different filling pressures are investigated: 1 bar (atmospheric pressure), 20 bar, and 40 bar, the latter being in the supercritical region. To investigate the effect of inter- electrode gap on the recovery process, two different gap distances are used: 20 mm and 50 mm. A 10 kV high voltage pulse with a rate of rise of 150 V/µs is applied across the electrodes after current zero. To evaluate the recovery process, the time between current zero and the start of the pulse is varied from 10 µs to 10 ms. Experimental results show that the dielectric recovery performance improves with the filling pressure even in the absence of a forced gas flow. The breakdown strength is observed to recover faster for a longer electrode gap.