Study on the Lightning Withstand Ability of Transmission Line Considering Surge Corona

In order to improve the lightning calculating accuracy of transmission lines, the impact of surge corona is considered in this paper with the software of Electromagnetic Transient Program (EMTP) and a new improved corona model is proposed. The model is based on the concept of corona´s radius. The region between the transmission lines which are under lightning and the ground is divided into corona region and no corona region. The analysis of lightning transient process shows that the influence of the corona is so great that the corona´s impact should be taken into account to determine the insulation level. Besides, the effect of the power frequency voltage and the velocity changes are also studied. The simulation results show that considering the power frequency voltage and the smaller velocity due to the surge corona, the voltage of the top of tower is much higher than ignoring them, so these factors should be integrated when determine the insulation coordination for the transmission lines.