Analysis of Positive and Negative Lightning Impulse Discharge Characteristics in Long Air Gaps

Lightning is a common cause of failure in high-voltage transmission lines. This paper uses physical models of positive and negative discharges to analyze the differences in discharge characteristics between rod–plane and conductor–tower gaps. It also explores the influence of different tower structures on the discharge process. The simulation results show that negative leaders develop in a stepped manner and progress rapidly, while positive leaders develop continuously and progress more slowly. Under the same lightning impulse voltage level, negative discharges exhibit higher breakdown voltages. The development speed of positive discharges is mainly influenced by the applied voltage, while negative discharges are less affected by the applied voltage. For the same gap distance, the 50% breakdown voltages in the conductor–tower model are significantly higher than those in the rod–plane model for both polarities. Additionally, under shorter gap conditions, negative discharges may not show distinct stepped characteristics. This study provides theoretical guidance and practical references for lightning protection design and engineering applications in high-voltage transmission lines.