This　paper　presents　a　novel　time-domain　fault　location　algorithm　for　parallel　transmission　lines　using　two　terminal　currents.　Parallel　transmission　lines　with　faults　can　be　decoupled　into　the　common　component　net　and　differential　component　net.　Since　the　differential　component　net　is　only　composed　of　the　parallel　lines　and　its　terminal　voltages　equal　zero,　the　proposed　algorithm　is　based　on　the　fact　that　the　difference　between　voltage　distributions,　calculated　from　two　terminal　currents,　is　the　smallest　at　fault　point.　To　be　practical,　unsynchronized　data　＇　and　the-transient　transferring　ability　of　the　current　transformer　are　taken　into　consideration.　The　algorithm　needs　a　very　short　data　window,　and　any　segment　of　current　data　can　be　used　to　locate　faults.　The　proposed　algorithm　is　verified　successfully　using　the　simulation　data　generated　by　the　frequency-dependent　line　model　of　the　Alternative　Transients　Program　and　the　field　recording　data　provided　by　traveling-wave　fault　locators.　Locating　results　show　the　satisfactory　accuracy　of　the　algorithm　for　various　fault　types,　fault　distances,　and　fault　resistances.