Alternative Insulating Fluids - Interpretation of Test Results

In recent years, more and more transformers filled with esters have been put into operation. This is because people recognize the benefits of ester fluids in terms of their fire safety (high flash- and fire points) and environmental characteristics, judging from their biodegradability, their low CO2 footprint (only valid for natural ester) and their beneficial interactions with solid insulation, etc. Ester fluids have already found their way into various standards. For analysis and testing the same equipment and devices that are commonly used for mineral oil are used for ester liquid. The chemical- and physical behaviors of ester fluids compared to mineral oil are different. This must always be considered when interpreting test results stemming from ester fluids.