Simulation and Structure Optimization of Grounding Circuit Model for Power Transmission Line Tower

The lightning current dispersion process through the steel bar inside the concrete pile foundation of the transmission line tower is impeded by the high concrete resistivity. In order to improve the current dispersion performance of the pile foundation, this paper proposes a method to place flexible graphite grounding electrode along the shaft wall of the tower foundation and verified its feasibility. Both single-pile and four-pile foundations are applied to build vertical grounding models of transmission line tower with three different grounding structures, respectively, including flexible graphite grounding line, flexible graphite grounding fabric and combined graphite electrode. The effect of three grounding structures on the current dispersion and resistance reduction is studied by finite-element method. Simulation results indicate that by applying the above three grounding structures on the vertical pile foundation can significantly improve the current density distribution of the excavated pile foundation and reduce the grounding resistance. When the grounding resistance is 200 Omega . m, the resistance reduction efficiencies of the above three methods can reach 48.56%, 53.86% and 54.53%, respectively. Considering the limited construction area, this paper compares the foundation that is placed combined graphite grounding electrode with square-ray grounding grid, and it can be seen that by placing vertical grounding electrode can save the land area of 295.99 m(2). This paper can provide reference for the design of excavation pile foundation grounding structure under limited construction area.