A　new　fault　location　principle　using　one　terminal　voltage　and　current　data　for　EHV　transmission　lines　is　described　in　this　paper,　which　is　based　on　distributed　parameter　line　model,　breaking　through　the　traditional　single-ended　fault　location　ideas.　The　voltage　profile　along　the　healthy　line　could　be　calculated　using　single-ended　voltage　and　current　data;　however,　the　voltage　profile　behind　the　fault　point　is　not　true　for　a　faulted　line.　Even　though,　notice　the　fact　that　the　norm　value　of　derivative　function　of　the　＂fictitious　profile＂　to　distance　is　minimum　at　fault　point,　based　on　which　the　fault　location　function　is　constructed.　The　numerical　algorithm　is　also　described;　this　principle　is　proved　by　EMTP　simulations　to　be　immune　to　fault　resistance,　fault　types,　and　fault　inception　angle.　Theoretically,　the　accuracy　of　the　principle　is　proportional　to　the　sampling　rate　of　the　locator.