Hybrid Optimization of Grounding Grid Systems for UHV 1200 kV Transmission Lines

This paper presents a hybrid iterative optimization methodology for grounding grid systems in Ultra High Voltage (UHV) 1200 kV AC transmission corridors. The proposed approach combines rod addition, surface expansion, and depth increase strategies to achieve Z0/Z1 ratio compliance below 3.0 (IEEE C62.92) while maintaining Ground Potential Rise (GPR) under 50V (IEEE 80). Applied to a 1000 km, 8000 MW corridor, the algorithm converged in 26 iterations, reducing Z0/Z1 from 4.09 to 2.82 and GPR from 288V to 32V, with a final grounding resistance of 0.026 Ω.