FROM SPECIFICATION TO INSTALLATION: 345 KV NATURAL ESTER GSU TRANSFORMERS
This month’s Featured Technical Paper is from the Proceedings of the 2026 International Conference of Doble Clients. The paper is titled: From Specification to Installation: 345 KV Natural Ester GSU Transformers.
Abstract
The Bureau of Reclamation recently completed a major transformer replacement project at one of its facilities (Site 2), involving three banks of 345 kV, 375 MVA and one bank of 230 kV, 375 MVA transformers. The 345 kV units, filled with natural ester insulating fluid for improved fire safety, environmental protection, and longer insulation life, were the world's highest BIL-tested (1175 kV) ester-filled transformers at their time of manufacture. This paper presents the rationale for selecting ester fluid at this site and details the development and refinement of the technical specifications required to manage new transformer designs due to differing insulating fluid. It outlines lifecycle adjustments, including tailored dielectric designs, stringent manufacturing processes, and material compatibility. Furthermore, it details key insights gained during installation, overcoming logistical hurdles like long-term nitrogen preservation and impacts on ancillary systems. Finally, the paper compares factory and field test results and highlights online dissolved gas analysis (DGA) data collected during early operation. This paper demonstrates that ester fluids can be safely and reliably implemented into the high-voltage bulk electric system.
Doble Service Agreement Clients
This and other technical papers and presentations are available in the MyDoble Resource Center - one of the many benefits available to you as a Doble Service Agreement Client. To get to the MyDoble Resource Center login click here. Not a member? Follow the sign-up process.