In　this　article,　a　novel　photovoltaic　(PV)　bypass　diode　fault　detection　algorithm　is　presented.　The　algorithm　consists　of　three　main　steps.　First,　the　threshold　voltage　of　the　current-voltage　(I-V)　curve　is　obtained　using　different　failure　bypass　diode　scenarios.　Second,　the　theoretical　prediction　for　the　faulty　regions　of　bypass　diodes　is　calculated　using　the　analysis　of　voltage　drop　in　the　I-V　curve　as　well　as　the　voltage　at　maximum　power　point.　Finally,　the　actual　I-V　curve　under　any　environmental　condition　is　measured　and　compared　with　theoretical　predictions.　The　proposed　algorithm　has　been　experimentally　evaluated　using　a　PV　string　that　comprises　three　series-connected　PV　modules,　and　subtotal　of　nine　bypass　diodes.　Various　experiments　have　been　conducted　under　diverse　bypass　diodes　failure　conditions.　The　achieved　detection　accuracy　is　always　greater　than　99.39%　and　99.74%　under　slow　and　fast　solar　irradiance　transition,　respectively.　©　2011-2012　IEEE.