Nowadays partial medium voltage distribution networks adopt single-phase power supply lines in order to improve the economics of grid operation. However

the propagation process of traveling wave is complicated if the single-phase-to-ground fault occurs

which affects the accuracy of the fault location. This paper proposes a novel method which considers the propagation mechanism of traveling wave produced by single-phase-to-ground fault

including phase-mode transformation

the transfer velocity of different mode

and the propagation characteristic at boundary. Whether the fault position is at the single-phase power supply line or at the three-phase power supply line can be identified and the fault distance can be calculated based on the time difference of the arrival surge between the aerial mode and zero mode components. EMTP/ATP simulation verifies the reliability and accuracy of the method.