High-impedance transformers have been widely used for their advantages of limiting short-circuit current. The inrush current problem of the high-voltage built-in high-impedance transformer (T-Hin) will be more prominent than the traditional transformer. In recent years, there have been many misoperations of the backup protection of the transformer and its adjacent equipment. From the perspective of the winding structure, the correspondence between the magnetic flux distribution and the parameters of the transformer equivalent circuit is clarified. According to the analytical expression of zero-mode inrush current and the difference of the leakage inductance parameters of several transformers, it is pointed out that the T-Hin inrush current amplitude is larger and attenuation is slower, which is verified by simulation. The causes of protection misoperation caused by zero-mode inrush current are obtained. And the future improvement of simulation and experimental platforms, and the direction of deepening research are prospected. This work is supported by National Key Research and Development Program of China (No. 2016YFB0900600) and Science and Technology Project of Guangdong Power Grid Co., Ltd. (No. GDKJXM20162461).