Resonant electric arcs in DC microgrids with low system impedance in the VLF-band
Various fault scenarios have been analyzed by running a number of differently combined 380 VDC microgrid tests. These tests represented a common grid topology with low system impedance at grid resonance points within the single- or lower double-digit kHz range. At serial arc faults, self-excited resonant modes of the arc plasma column have been observed. They lead to an increased arc column stability compared to non-resonant arcs with colored noise behavior. These characteristics require a special focus on pattern recognition methods for arc fault sensors along with extended suitability tests for mechanical and hybrid switchgear concerning the altered stability of switching arcs. The use of small-signal models for system components such as source and load converters as well as for arcs with regard to large-signal DC operating points and converter control modes is helpful in order to describe the reaction of the system in the event of a malfunction. This is essential for the development of suitable protective components and algorithms.