Abstract: When lightning happens, lightning current enters grounding systems through the tower, which will cause ground potential rises. In order to study the effect of transient over voltage and its effect on wind turbines and other power equipments more effectively, a grounding transient circuit model is built based on the idea of field circuit method, and the rise of ground potential caused by lightning is simulated in this paper. The calculation result shows that inductance effect of grounding is more obvious than that of resistor due to high frequency of lightning current, which increases the grounding potential of grounding network. In addition, transient over voltage will destroy the insulating layer of the transmission, communication, and control cable, and over voltage will also cause partial discharge.