By Mel Wright

Never trust that "new oil" means that the fluid, as delivered, meets specifications. Test and verify!

This is not the typical water in oil discussion about limits, percent saturations and so on. The goal of this article is to give transformer maintenance personnel some points to ponder when dealing with both dissolved and free water in mineral oil transformers. I'll present some real-world experiences and discuss some visual aids or experiments to better understand the gross interactions of water in mineral oil dielectric fluids.   

Transformer manufactures and the producers of mineral oil dielectric fluids go to great efforts to ensure their products are as free of water as possible. There are many tests performed to validate that both the transformer and the fluid meets ASTM, IEEE and IEC specifications. The question becomes: How does water get into transformers compromising both the fluid and the cellulose insulation? Let's review some real-world examples.

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This article was originally published in the March 2020 issue of the Transformer Oils & Fluids: Development of Transformer Fluids Over the Last Century magazine.

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