Abstract: The power collection line in wind farm presents the operation form of multi-branch and multi-power supply access. After a single-phase grounding fault occurs on the line, the wind generators on different branches will automatically input different control strategies according to the different voltage drop they feel, which will result in different branch current output. So the traditional method based on impedance principle was invalid. This paper cleverly used the fact that the high voltage side of the step-up transformer in branch adopts triangle connection, without zero sequence current through, and put forward a novel fault location method based on the successive search of fault section. And the logarithm arc model was introduced to describe arc grounding of fault point, which achieves high ranging accuracy. The effectiveness of the algorithm is verified by simulation and actual recorded data. Arc length can also be calculated out in algorithm, which lays a foundation for the subsequent fault type identification.