Abstract: To study the secondary arc extinction time and ensure the success of the single phase automatic reclosing, the secondary arc parameters are theoretically analyzed, and an arc model is built to simulate the transmission line fault after the single phase grounding by use of the electromagnetic transient simulation software PSCAD/EMTDC. The Jin dongnan Nanyang Jingmen UHV(Ultra High Voltage) AC transmission lines item is used as an example. Factors influencing the secondary arc current are analyzed, such as line arrangement, conductor transposition, transmission capacity, line structure and so on. Simulation results are consistent with the theoretical analysis. The conclusions can offer references to the under construction UHV projects.