To analyze the reason why the 10 kV potential transformer (PT) frequently fused, taking a 110 kV transformer substation for example, it summarizes the theories firstly. Then, simulation of a power system model is performed according to the actual parameters of this substation using the ATP / EMTP simulation software. It concludes that the transient inrush current caused by ground capacitor discharge is a direct reason for frequent fault of the 10 kV PT. Also, the unbalanced distribution of the inrush current caused by different excitation characteristics of PTs, is an important reason for its fuse. Based on this case, it proposes several improvements such as installing resonance eliminator in the neutral points of PT, or switching to 4PT wiring. The simulation shows great improvement on limiting the transient inrush current of a single PT. But when several PTs are paralleled, the condition of each PT should be accounted in order to eliminate any possibility of PT being fused by overcurrent.