Comparative Evaluation of Grounding Configurations for a 275-kV Standalone Lattice Tower Subjected to Lightning Transients Using EMTP

The influence of grounding arrangements on the lightning transient response of a 275 kV standalone lattice tower is studied by EMTP. This study evaluates the performance of a mesh-grid grounding system (MGGS) under severe lightning transient conditions. A single Tower No. 310 on the Lahat-Lubuk Linggau line is modelled using an observed soil resistivity of 116.3 Ω · m. The following three grounding schemes are considered: Natural grounding with two vertical rods, MGGS1 which is Natural grounding plus the mesh-grid grounding system, and MGGS2 which is MGGS1 plus a number of jumper conductors from the tower legs to the grid center node. A peak value of 30 kA 1.2/50 μ s lightning impulse current is applied at the tower top. The 30 kA current is chosen since it is the largest recorded lightning current at Tower T. 310 in the 2025 Vaisala exposure report for the Lahat-Lubuk Linggau power line and it is hence considered as a representative extreme case. Peak current and peak voltage values were extracted within the first 5 μ s of the transient response, while 50 μ s is used as the observation limit of the waveform. The results show that the tower-foot voltage was reduced from 882.9 kV in the Natural configuration to 41.2 kV in MGGS1 and 16.8 kV in MGGS2. Again, MGGS2 yields the least oscillation and undershoot on the tower leg. The results demonstrate that tower-foot potential rise can be suppressed and the lightning performance can be enhanced by MGGS and more m strength is obtained for MGGS2.