P37.101: Transformer Life Management

EPRI Power Transformer Guidebook (The Copper Book) 2025 update: Each year, EPRI publishes updates to The Copper Book to keep members up to date with the latest research, technology developments, and transformer standards. The guidebook has been written with the utility engineer and field staff as the audience and covers the entire range of topics from specification to end-of-life assessment. In 2025, two valuable additions will be made: first, deeper guidance on dissolved gas analysis (DGA) sampling based on EPRI laboratory testing; second, a growing list of quick reference, single-page summaries of key topics.

Technical webinars on the Transformer Guidebook: Multiple technical webinars based on sections in the Transformer Guidebook are hosted each year. The webinar material is published for continued and convenient future access. Topics are selected to accelerate learning on key topics in the Transformer Guidebook (The Copper Book).

Transformer online monitoring technologies: Laboratory testing to help members in specification development: The results from the 2025 research provide valuable assistance in transformer monitor specification, interpretation, and adoption. A full 138-kV EPRI research substation was commissioned and energized to support this research. EPRI laboratory test results are executed against a well-defined test protocol for online DGA monitors, online bushing monitors, online partial discharge (PD) monitors, and online temperature monitors. This unique approach allows for rapid answers on high-impact decisions that are then applied fleetwide in a utility.

Alternative fluids for transformers for increased ratings, extended service life, and reduced environmental impact: This research in 2025 intends to explore the characteristics that define the end of life for an ester fluid. With several years of use, many chemical and physical properties of ester fluids can change significantly from the starting values. In many cases, the values of different ester properties can surpass the limits set for mineral-based oils. Even with such property changes, many users continue to use the ester fluids, not knowing how detrimental the changes in fluid could be to the operation and health of their transformer. Using accelerated aging systems, beneficial guidance could be obtained on what changes to chemical and physical properties (such as acid number, fire point, and viscosity) mean to system operation and health. The goals of the results are twofold: first, to help set limits for acceptable operation of ester fluids; second, to help users decide when to perform a course of action on an ester fluid such as maintenance, a fluid change, and/or change the loading on the transformer.

Membrane technologies for online, low-maintenance dryout of transformers: Through several years of research, EPRI has developed a novel membrane-based system that continuously removes water from transformer oil online. The system removes water without the need to use replaceable cartridges or remove diagnostic dissolved gases, all while using minimal moving parts. A goal of the research in 2025 is to explore further enhancement of the water extraction through methods such as oil precooling and/or multiplexing internal technologies, while keeping the system size within the current footprint. In addition, it is intended that the condition of some components used in field systems will be examined to potentially devise ways to increase the ruggedness and resilience of future systems or retrofits or allows field personnel to easily replace certain components. Field pilots in utility substations will continue to validate the technology to strive for systems that can be deployed for multiple years with minimal or no maintenance.

New oil markers to aid power transformer diagnostics: In 2025, it is planned that the stability and dynamics of some newly identified oil markers by EPRI, and others in the literature, be explored. It is known that new marker compounds are generated in the presence of oil and/or paper under different stresses (that is, overheating, PD, arcing). However, the longevity and interaction dynamics of the new markers with other components and chemicals inside a transformer are not known well—or sometimes not known at all. Data collected from a unique online marker detection system deployed by EPRI aim to provide insights into new marker dynamics in a working transformer. It is also intended that further exploration into new marker dynamics will be performed. The results will provide the industry with enhanced value from oil samples—allowing greater insights into transformer condition.