IS 335 defines requirements for mineral insulating oil used in transformers and switchgear, including key quality parameters, test methods, and acceptance limits. It typically covers properties such as dielectric strength, moisture content, acidity, flash point, viscosity, density, and oxidation stability, plus guidance on uninhibited versus inhibited grades. Having a national standard helps procurement and quality control by ensuring oils from different suppliers meet a consistent baseline. The standard is maintained by the Bureau of Indian Standards and is commonly referenced in Indian utility tenders and laboratory reports.
.
