Copper-Electrode Voltage Falls and Electric Fields of a 540 VDC Free Burning Arc in Air: Dependence on Pressure and the Application to the More Electric Aircraft Issue

With the increase in DC voltage levels in aircraft electrical networks up to 540 VDC, it is essential to improve the understanding and characterization of fault arcs. This article focuses on the characterization of opening electric arcs in air, between 100 and 1000 hPa, through static electrical quantities, namely the electric field and anode and cathode voltage falls. These quantities are determined from measurements of the arc voltage as a function of the inter-electrode distance, which is assumed to be equal to the arc length for arcs shorter than 10 mm. The experiments are performed with copper electrodes, under a 540 VDC power supply and currents of about 50 A. Two regions are identified in the voltage signals: a first region at short inter-electrode distances, typically below 1 mm, and a second region at larger distances. In the first region, no clear pressure-dependent trend is observed, whereas a distinct evolution with pressure is identified in the second region. A multi-camera setup provides complementary views of the arc structure and of the copper vapor distribution, which also appears to vary with pressure.