Optimal design of tower footing device with combined vertical and horizontal grounding electrodes under lightning

•The practical effects of driven rods on reducing the impulse impedance of the tower footing device are compared.•The non-metal driven rod takes the best effect while the metal driven rod takes the worst in the testing condition.•We analyzed the regularity of the optimal design of the tower footing device by numerical simulation.•The shorter the leg length and the higher the soil resistivity, the more likely to install the driven rod at the terminal.•With soil resistivity increasing or total length decreasing, optimal structure shall consist of fewer and longer electrodes.

The property of tower footing device under lightning is an important issue for lightning protection. This paper focuses on analyzing on the optimal design of the tower footing device under lightning. Firstly, the practical effects of three kinds of common applied driven rods under lightning are researched by field testing. It is concluded that in the testing condition, the non-metal driven rod takes the best effect while the metal driven rod takes the worst. Moreover, the optimal installation position of the driven rods and the optimal structure of the horizontal electrodes are analyzed by numerical simulation, respectively. Both of them are heavily affected by soil resistivity and size scale of the tower footing. In order to solve the two practical problems, quantitative optimal criterions are put forward, which can be referred to while determining the optimal design of the tower footing device under impulse. That is very meaningful for engineering application.