Dynamic characters research of air arc at low current in long gap

The short-circuit arc in distribution network and secondary arc in transmission line caused by single-phase earthing fault burn in free air, so it is difficult to test and simulate the self-extinction behavior of air arc at low current in long gap for its serious non-linearity. The method is adopted to measure and analyze the physical characters of this arc by laboratory tests in the paper. The waveforms of voltage and current aere recorded in different circuits associated with arc at low current. And arcs' developing films are taken by high-speed imaging system during arcing process. Based on test data, arcs' physical characteristics are presented to obtain arc time-variable characters. The form mechanism and the transitional trace of arc waveforms such as voltage and current are discussed with arc theory and physics doctrine. Arc resistance and dynamic u-i curve are obtained to explore the dependency on arc parameters and their variable trend. Finally arc self-extinction criterion is proposed to compute arc durations under the different conditions, which are corresponded with test results. All the analysis has validated arc testing method and conclusions, providing the reference to investigating the self-extinction behavior and modeling for arc.