<P> Transformer oil or insulating oil is an oil that is stable at high temperatures and has excellent electrical insulating properties . It is used in oil - filled transformers, some types of high - voltage capacitors, fluorescent lamp ballasts, and some types of high - voltage switches and circuit breakers . Its functions are to insulate, suppress corona discharge and arcing, and to serve as a coolant . </P> <P> Transformer oil is most often based on mineral oil, but alternative formulations with better engineering or environmental properties are growing in popularity . </P> <P> Transformer oil's primary functions are to insulate and cool a transformer . It must therefore have high dielectric strength, thermal conductivity, and chemical stability, and must keep these properties when held at high temperatures for extended periods . Typical specifications are: flash point 140 ° C or greater, pour point − 30 ° C or lower, dielectric breakdown voltage 28 kV (RMS) or greater . </P> <P> To improve cooling of large power transformers, the oil - filled tank may have external radiators through which the oil circulates by natural convection. Power transformers with capacities of thousands of kVA may also have cooling fans, oil pumps, and even oil - to - water heat exchangers . </P>

What is the flash point of transformer oil