What is the flash point of transformer oil and why is it critical?

Flash point is the temperature at which oil vapors can ignite in air under standardized test conditions. It matters because higher flash point generally means lower fire risk during overheating events, arcing, or external flames. Utilities use flash point as part of fire safety evaluation, especially in indoor substations, urban pad mounts, and locations near critical infrastructure. Oils such as natural esters and some silicones typically have higher fire points than mineral oil, which can support reduced fire separation distances in some designs, though engineering assessment is still required.