Overview

This webinar presents highlights from CIGRE Technical Brochure 856, a collaborative study on the dielectric performance of insulating liquids used in power transformers.

For over a century, dielectric liquids—primarily mineral oils—have been essential in transformer insulation systems. Today, a wider range of liquids with diverse molecular structures is in use, each with unique dielectric properties. This session explores how these liquids perform under various conditions and how they influence insulation design and testing.

• Types and characteristics of commonly used insulating liquids
• Principles of transformer insulation design
• Mechanisms of breakdown in liquids: initiation vs. propagation
• Physical models explaining breakdown behavior
• Review of IEC test methods for dielectric liquids
• Design rules and how new findings impact engineering practices

Features

Highlights

Attendees will learn how to:
● Typical field stresses in power transformers.
● Latest results from research on dielectric liquids
● Differences between liquid performance for different insulating liquids
● Background for design review

Speakers

Lars E. Lundgaard (IEEE senior member) received his master’s degree in electrical engineering in 1976 at the Norwegian Institute of Technology. He is working as a Chief Scientist at SINTEF E nergy Research, where his main interests are in electric insulation systems. He is an active member in CIGRE in the fields of materials and transformers, and has written about 70 journal
and 100 conference papers.

The study is a joint work done within CIGRE, with representatives from academia, transformer manufacturers, liquid suppliers, and utilities. CIGRE is an international organization for sharing and developing information related to transmission and distribution of electric energy.