Performance and Characteristics of a Small-Current DC Arc in a Short Air Gap

DC arc evolution is a complicated and rapid time-dependent process. To better demonstrate the mechanism of the dc arc without external interference factors, a test circuit was built for the entire process of arc generation, maintenance, and extinction. Two different adjustment models were adopted. The macroscopic performance and characteristics of the arc were analyzed. The discharging and extinguishing conditions were measured and compared to the results of a burning candle located under a rod-rod air gap. This paper shows that the dc arc's color changes from blue to purple and then yellow, finally forming a flame as the current increases. The macroscopic performance can be divided into eight periods in the first adjustment model, while only three periods are included in the second model. The arc discharging condition only depends on the applied high voltage, but the extinguishing condition may depend on either the limiting current or the drop-down voltage. Dynamic volt-ampere characteristics appear only if adjusted by the first model. The arc-root voltage is constant to 0.32 kV. The degradation of the ground electrode is far worse than that of the high-voltage electrode. This paper can be regarded as the first-step research for further studies on large-current dc arcs in arcing horns used in dc transmission grounding lines.