Abstract: 10kV and 35kV systems are usually ungrounded systems. Considering the threat to the safe and stable operation of equipment caused by single-phase grounding faults that cannot be eliminated for a long time, small current grounding line selection devices are usually equipped for line selection and tripping. At the same time, they cooperate with reclosing to achieve fault isolation and rapid recovery of power supply from instantaneous faults. Starting reclosing with small current grounding line selection devices belongs to external protection starting reclosing, The coordination between protections is very important. This article mainly analyzes a case of a small current grounding line selection device tripping and reclosing not operating, in order to further understand the problems and corresponding improvement measures of external protection starting reclosing, and provide some reference for on-site fault handling.