Modeling of corona under positive lightning surges

•The proposed model can consider the main microcosmic evens in corona discharge.•The ionization process is treated as successive generations of electron avalanches.•A simplified method is given for computing the electric field in ionization zone.

A novel corona model for predicting the corona characteristics under positive lightning surges is proposed. The ionization process is described by a series of successive generations of electron avalanches. A simplified method is presented for computing the electric field in the ionization zone. With a discrete treatment for the ionization process in time and space, the proposed model computes the total charge of corona from the applied surge voltage and so the q–u curves can be obtained. A laboratory measurement of q–u curves is also made by a coaxial cylindrical electrode to check the validity of the proposed model.