A phase B grounding fault occurred on the Nabanqing I line at the 110kv Namucuo substation in a certain power grid, causing the distance protection of zone I on the Nabanqing II line at the same substation to operate incorrectly. Theoretical analysis indicated that the maloperation was likely due to two-point grounding in the voltage transformer (VT) secondary circuit. To further verify this, a detailed electromagnetic transient simulation model was developed using PSCAD. The simulation results confirmed that the distance protection maloperation was indeed triggered by two-point grounding in the VT secondary circuit. This study, based on an actual power grid event, provides valuable insights for analyzing similar incidents and offers practical guidance for preventing such occurrences in power systems.