This invention is related to an electric insulating oil and preparation method, which have low
pour point and excellent
hydrogen absorbency even if not using the pour inhibitor that can worsen the electric performance, and prevent the insulative damage caused by the upward floating when the
moisture content mixed inside the
transformer is frozen, such that the
flash point is higher and the fatalness of occurring fire is lower. And this invention has no causticity to the
copper because of without having the
sulfur and has excellent electric performance, so that the practicality is excellent. The electric insulating oil is characterized that: the
pour point is not greater than 45 below zero; the kenematic
viscosity (40 degrees centigrade) is 6mm (2) to 10 mm (2); the
flash point (PM) is not smaller than 135 degrees centigrade; the density (20 degrees centigrade) is not greater than 0.895kg / L; the
aniline point is 63 to 90 degrees centigrade; the
sulfur content is less than 3 weight ppm; the
nitrogen content is not greater than 3 weight ppm; the basic
nitrogen content is not greater than 1 weight ppm; the aromatic series content is not smaller than 5 weight%; and the
antioxidant of 0.05 weight% to 0.5 weight% is contained.