Abstract: Based on a certain wind farm, this paper introduces the zero sequence network and fault characteristics of the collector line during a small resistance grounding fault in the wind farm. Analyzed an accident where the grounding transformer in the station tripped due to a phase to phase short circuit on the low-voltage side of the fan box transformer, ultimately leading to the burning of the box transformer. Rectification measures were proposed for the cause of the accident, and the setting calculations of the zero sequence protection of the transmission line and the zero sequence protection of the grounding transformer were optimized. The effectiveness and correct range coordination were verified through simulation.