Abstract: This paper analyzes an overvoltage tripping event of switchgear caused by 10 kV grounding. Phase A of the 10 kV feeder line is connected to the ground, voltages of phases B and C increased, 15 board (capacitor No. 1) due to arc overvoltage, indoor insulation breakdown of the bus, and rapidly developed into a three-phase shortcircuit. Arcdrift caused the ablation of the back baffle of bus room and the lower baffle, serious heat in the switch cabinet contacts, resulting in insulation performance deterioration, and interphase short circuit in thr cabinet occurs quickly.