Over 40 Years of Ester Dielectric Liquids for High-Voltage Transformers: A Retrospective on Evolution, Performance, and Future Prospects (An Extended report of the Hans Tropper Memorial Lecture 2025)

This article reviews more than four decades of experience with ester-based insulating liquids in high-voltage power transformers, highlighting major milestones, performance advantages, technical challenges, and the evolving role of esters in enabling safer, more efficient, and environmentally sustainable power systems.