Impulse Grounding Resistance Reduction Measures for Transmission Line Towers in Desert, Gobi, and Barren Land Regions

The high soil resistivity in desert, Gobi, and barren land regions limits the lightning current dissipation capability of conventional needle-type grounding electrodes, thereby increasing the lightning-related risk to transmission lines. To address this issue, a three-dimensional transient simulation model of a horizontal needle-type grounding electrode equipped with grounding modules was developed in COMSOL Multiphysics (version 6.2) based on electromagnetic field theory and the nonlinear ionization characteristics of soil. The effects of the number, spacing, and downward inclination angle of the needles, as well as the geometric dimensions of the grounding modules, on the impulse grounding resistance and current dissipation characteristics were systematically investigated. The simulation results indicate that the needle-tip effect and mutual shielding effect between adjacent needles are the primary factors governing current dissipation performance. Increasing the number and spacing of the needles improves the grounding performance. Among the discrete inclination angles investigated, intermediate inclination angles generally exhibited relatively low impulse grounding resistance; however, the differences among the inclination angles were small, and the inclination angle corresponding to the minimum impulse grounding resistance varied with the critical soil ionization field strength. Under the baseline conditions of a 10 kA impulse current and an initial soil resistivity of 1000 Ω·m, the resistance reduction provided by the grounding modules decreased from 15.34% for one bilateral needle unit to 12.62% for nine units. Increasing the needle spacing from 0.3 to 1.1 m reduced the impulse grounding resistance by 18.09% and 11.38% for the configurations with and without grounding modules, respectively. Increasing the module radius from 0 to 0.25 m produced a 29.03% reduction in impulse grounding resistance, although the incremental resistance-reduction benefit gradually diminished as the module dimensions increased. These findings provide a theoretical reference for optimizing transmission-line tower grounding systems in high-resistivity desert, Gobi, and barren land regions.