A　topology　analysis　method　of　transformer　insulation　is　proposed,　which　considers　free　relaxation　process.　This　method　introduces　free　relaxation　factor　βi　from　microscopic　dynamics,　based　on　the　return　voltage　line　relaxation　parameter　information.　The　branch　lines　of　different　dielectric　relaxation　response　information　is　obtained,　and　the　topological　structure　of　transformer　insulation　is　determined.　At　the　same　time,　the　relationship　between　more　than　30　sets　of　transformer　insulation　relaxation　parameters　and　condition　assessment　are　studied.　The　results　show　that　number　of　relaxation　mechanism　number　N,　average　time　constant　and　free　relaxation　factor　βi　can　reflect　insulation　status.　As　the　aging　degree　of　transformer　oil-paper　insulation　increasing,　the　number　of　relaxation　mechanism　N　and　the　free　relaxation　factor　βi　are　increasing,　on　the　contrary,　the　average　time　constant　is　decreasing.　In　addition,　free　relaxation　factor　has　a　different　scale　in　the　deterioration　of　oil　and　paper,　which　can　provide　a　new　idea　for　transformer　insulation　aging　evaluation.　©　2017,　Science　Press.　All　right　reserved.