Secondary Arc Current During DC Auto Reclosing in Multisectional AC/DC Hybrid Lines

In this paper, a contribution to the analysis of electromagnetic ac to dc interactions in complex ac/dc hybrid overhead lines was made. For accurate calculation of such coupling, standard transformations like the symmetrical components cannot be used. Therefore, a method based on adjusted modal decomposition was presented, which allows analysis of untransposed and partly transposed configurations in arbitrary switching states. The method was applied to the case of dc fault clearing using single-pole auto reclosing (dc SPAR), where parallel ac circuits could induce a secondary arc in the dc line. The magnitude of the secondary arc current was examined, which allows evaluating the necessary dead time of the dc SPAR. The influence of parameters like line configuration, load flow, and fault location was discussed. After that, a realistic study case hybrid line was analyzed. In particular, the comparison to secondary arcs in ac lines and the behavior as a function of fault location in the context of changing ac systems and line configurations along the hybrid dc corridor provide new insights into a relevant phenomenon.