The positive leader discharge in the long air gap is the focus of research on the external insulation design of UHV AC and DC transmission projects. While the electric field of the positive continuous leader channel is the key physical parameter concerned in the prediction of the 50% breakdown voltage of the air gap. In this paper, a simulation model for the ionization process of the continuous positive leader channel is constructed, considering the non-equilibrium effect. Based on the current data of the positive leader discharge with a 3.0 m rod-plate gap, the non-equilibrium physical process is simulated. Compared with the model proposed by Gallimberti, the radius expansion process calculated by our model is more consistent with the experimental measurement results. The relationship between the reduced electric field in the leader channel and the gas temperature is obtained, and a method for estimating the electric field is constructed by combining the energy conservation equation.

leader discharge;;electric field;;non-LTE;;gas temperature;;computational model