In the neutral ungrounded distribution network, the single-phase grounding fault and its disappearance can easily lead to potential transformer (PT) ferroresonance or low-frequency nonlinear oscillation. They can resulting in frequent PT fuses blown, affecting the safety of the power system. To study the basic rules and influence factors of PT fuses faults in actual substation, the paper analyzes 35 fuses and PT faults in a power supply company within one year. One certain recorded data before and after one fuses blown fault is analyzed, being compared with the simulation waveform of the fault to finds out the cause of the PT fuses blown fault. At last, based on the verified simulation model, the measures to effectively eliminate the fault is find out. The research indicates that the reason for the PT fuses blown fault studied in this paper is the power frequency ferroresonance excited by the single phase grounding fault. The proposed suppression measure is a resonance eliminator with optimized parameters based on the actual working environment, and the method achieves a good result.