Measuring　the　current　in　high-voltage　direct　current　(HVDC)　systems　is　always　regarded　as　a　challenging　task.　For　transmission　systems,　dc　current　transformers　or　sensors　are　only　available　in　substations　and　converter　stations.　In　order　to　provide　more　flexibility　and　convenience,　this　paper　proposes　a　contactless　dc　current　sensor,　which　can　be　easily　placed　on-site　in　the　environment　of　HVDC　overhead　transmission　lines.　The　proposed　method　significantly　improves　the　convenience　and　safety　of　the　HVDC　current　measurement.　Using　a　magnetic-field　sensor　array,　the　proposed　current　algorithm　can　optimally　calculate　the　overhead-line　currents　with　partially　known　overhead-line　geometry.　The　simulation　results　in　this　paper　demonstrate　that　the　proposed　method　can　accurately　calculate　the　HVDC　current.　Moreover,　the　proposed　method　is　validated　by　a　reduced-scale　HVDC　overhead　transmission　line.　©　2001-2012　IEEE.