Series Arc Faults in a Megawatt-Level DC Microgrid

This paper presents a characterization of series arc faults based on experimental results obtained from a megawatt-level dc microgrid system. Series arc faults have garnered considerable attention because they can cause fires in photovoltaic systems and are not detected or isolated by legacy protection technology. Unlike the lower-power arc faults commonly reported in the photovoltaic literature, high-power series arc faults exhibit distinct behavior. Specifically, the elevated temperatures resulting from higher current levels increase plasma conductivity. At short air gaps, this conductive plasma remains stable, behaving as a linear series impedance; however, as the air gap widens, the arc becomes increasingly unstable, becoming nonlinear due to elevated pressures and thermally driven convection. The unstable nature of high-power arcs, combined with the significant circuit inductance introduced by large conductors, strongly influences the arc’s voltage and current characteristics. Furthermore, the stable plasma observed at shorter air gaps lacks the high-frequency components typically present in low-power dc arcs, rendering conventional detection methods ineffective. The proposed series arc fault model demonstrates strong agreement with the experimental results and supports the development of advanced protection schemes tailored for high-power dc microgrids.