HF Characterization of Low Current DC Arcs at Alterable Conditions

Abstract:
In the last few years, different concepts to detect arc faults in photovoltaic systems were developed but by now only few detectors are available on the market. The common ground of those detectors is the search for high frequency (HF) fluctuations in the PV string current generated by the arc. Among the manufacturers the observed frequencies and algorithmic approaches differ largely, since the arc generates a broadband noise and usable frequency ranges are mainly restricted by the used hardware and the HF noise characteristics. Up to now, most of the published results do not overview the real spectral density of the fluctuating arc current or voltage, especially in the typical PV low current range. To close that gap, measurements were made with copper electrodes to describe the spectral power density of low current arcs at different current levels and arc lengths. In addition, it is shown that an arc can be described as a voltage noise source.