What industry standards specify mineral oil requirements for transformer use?

Mineral transformer oil requirements are defined by international and regional standards that cover dielectric strength, moisture limits, acidity, oxidation stability, and contamination controls. Common frameworks include IEC standards used widely in utility grids and ASTM based specifications often used in North America. These standards define test methods and acceptance criteria for new oil, in service oil, and reclaimed oil. Utilities typically add their own procurement specifications to address inhibitor type, corrosive sulfur limits, and performance under local operating conditions.