Surge Arrester Application in 765 kV Systems: Current Practices and Future Trends in the U.S. Transmission Grid

Delivering six times the capacity of lower-voltage alternatives, these "energy superhighways" reduce line losses and environmental impacts. Ten major 2025–2026 projects adding approximately 5,027 miles (8,090 km), nearly two times existing lines, highlight a shift toward renewable, decentralized, and digital grids bridged by 765 kV corridors. This paper establishes a technical framework for the specification and application of Metal-Oxide Surge Arresters

(MOSA) to protect critical EHV assets within this evolving landscape. The methodology combines a comparative analysis of IEEE C62.11 and IEC 60099-4 standards with electromagnetic transient and insulation coordination studies for EHV systems. Protective margins are determined by modeling the non-linear V-I characteristics of Metal-Oxide varistors across diverse substation scenarios. Analysis prioritizes Switching Overvoltages (SOV) and

Temporary Overvoltages (TOV), which dictate 765 kV energy-handling requirements and surpass lightning surge considerations. Optimized arrester selection ensures appropriate Basic

Insulation Levels (BIL) for transformers and reactors, yielding significant cost savings without compromising reliability. While IEEE and IEC standards generally align, their differing energy discharge classifications require careful reconciliation for long-distance EHV applications.

Finally, the paper advocates advanced monitoring and condition assessment strategies to ensure surge protection evolves alongside grid modernization