Why is the boiling point of transformer oil important?

Transformer oil is designed to operate far below its boiling point, but boiling point still matters as a safety margin indicator under abnormal thermal stress. If localized hot spots approach temperatures where lighter fractions volatilize, gas bubbles can form and reduce dielectric strength, increasing partial discharge risk. A higher effective boiling range also supports stable cooling performance, reduces vapor formation in faults, and improves reliability of pressure and gas based monitoring in sealed or conservator systems.