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In order to solve the safety problem about person and equipment caused by the dispersed current during the transmission tower being lightning struck, it is necessary to study the characteristics of the dispersed current. In this paper, the dispersed current model of the tower grounding device is established in COMSOL. The distribution of the dispersed current around the tower is discussed, and the location of the test points is determined according to the simulation. Then the field experiment platform based on the lightning current generator and the dispersed current measurement system is established to measure the dispersed current. The influence of the grounding device structure on the dispersed current characteristics is discussed with the experimental data and simulation analysis. The results show that the field experiment platform can accurately measure the current density in the ground and the simulation results are consistent with the measured data. Therefore, the simulation model can be used in further study of the dispersed current situation around the grounding device. Far from the grounding electrode 4–5m, the current density decreased about 50%, 7–8m decreased by about 75%. The current density near the ground device decreases with the extension of the horizontal ground electrode, and the closer the distance to the grounding device is, the more obvious the trend is.

There are complicated climate and geographical environment in the Three Georges Area. Besides, there are frequently lightning activities in this area. Therefore, the lightning protection performance of transmission line is very weak. In order to improve power supply stable and reliable, it is very important to improve the evaluation and rebuilding levels of lightning protection for transmission lines. This paper researches on the lightning protection of 220kV typical transmission line based on differentiation technology and strategy of lightning protection. In detail, analyzing the differences of lightning activities, terrains and topographic features, line's structures and insulation configurations, lightning risk can be evaluated. Then, differentiation scheme of lightning protection can be proposed based on evaluation result.