Harvesting　energy　from　the　insulated　shield　wire　with　tuning　is　expected　to　be　a　possible　solution　to　the　problem　of　high　power　supply　for　online　monitoring　devices　on　high-voltage　overhead　transmission　lines.　However,　the　tuning　reactor　used　to　harvest　energy　in　insulated　ground　wire　has　a　small　inductance　adjustment　range,　which　is　difficult　to　adapt　to　the　fluctuation　of　equivalent　parameters　caused　by　external　conditions.　In　order　to　improve　the　load　adaptability　of　the　energy　harvesting　system　and　the　harvested　power　of　the　energy　harvesting　system,　this　paper　studies　a　magnetic　control　reactor　with　self-excited　function,　which　can　actively　adjust　the　reactor　inductance　according　to　the　fluctuation　of　the　equivalent　parameters　of　the　energy　harvesting　circuit.　Firstly,　based　on　the　multi-conductor　system　model　and　the　Thevenin　theorem,　the　topological　structure　and　equivalent　model　of　ground　wire　tuning　energy　are　established.　Secondly,　taking　the　energy　collection　section　of　220　kV　high-voltage　overhead　transmission　line　as　an　example,　the　variation　range　of　equivalent　parameters　is　considered　when　the　line　is　affected　by　extreme　weather　conditions　such　as　icing　jump　and　wind　deviation,　and　the　body　structure　of　the　line　is　changed,　so　as　to　determine　the　adjustment　range　of　the　inductance　value　of　the　tuning　reactor　for　reactor　parameter　design.　Finally,　the　field-circuit　coupling　transient　simulation　is　carried　out　by　ANSYS　Maxwell　to　obtain　the　maximum　harvested　power　and　the　voltage　across　the　reactor　under　different　conditions.　The　simulation　results　show　that　the　proposed　magnetically　controlled　reactor　can　obtain　energy　as　much　as　possible　from　the　insulated　ground　wire　when　the　equivalent　parameters　of　the　high　voltage　overhead　transmission　line　and　the　load　change,　and　effectively　limit　the　voltage　within　the　allowable　value　of　30　kV　insulation　level.　©　2022　IEEE.