Lightning strokes are the main cause for the trip fault of transmission line with a rated voltage of 110 kV and above. The counterattack trip and the shielding failure trip were thought to be the two kinds of fault type caused by lightning strokes. According to the development process of the two fault types, a few effective lightning protection methods are proposed. However, there is no relative report about the case that the ground wire and the conductor are stricken simultaneously. Therefore, no specific protection method is presented. In this paper, the possibility of the both stroke is analyzed, according the the mechanism of lightning stroke and the characteristics of lightning strokes. Then, a series of simulation test were designed and carried out. The observation results recorded by high-speed camera indicate that the downward leader could strike grounded wire and conductor simultaneously. At last, based on the intelligent monitoring system of transmission line, the traveling wave current of a lightning stroke was recorded. And after comparing the current with the simulation results by ATP/EMTP, the stroke was thought to be a both stroke. The photos in the fault point indicate that there are discharge points both on the grounded wire and conductor. And this field data clarified that the trip fault was caused by both stroke. A new lightning stroke fault was presented and verified in this paper, this report will supply important reference for lightning protection of transmission line.
