The invention provides high-flash-point low-condensation-point
transformer oil. Narrow fraction naphthenic oil is taken as basic oil, and an
antioxidant, a condensation
depressant, a
photosensitizing agent and a
metal deactivator are added, wherein the narrow fraction naphthenic oil accounts for 97-98% of the
transformer oil in percentage by weight, the
antioxidant accounts for 0.5-1.0% of the
transformer oil in percentage by weight, the condensation
depressant accounts for 0.5-1.0% of the
transformer oil in percentage by weight, the
photosensitizing agent accounts for 0.1-0.5% of the
transformer oil in percentage by weight, and the
metal deactivator accounts for 0.1-0.5% of the
transformer oil in percentage by weight. The invention further provides a preparation method of the high-flash-point low-condensation-point transformer oil. The closed-cup
flash point of the transformer oil provided by the invention can be 195-220 DEG C, the
condensation point of the transformer
oil can be up to minus 55 DEG C, the security property of the transformer oil is greatly better than that of the conventional transformer oil, and the transformer oil is applicable to extremely cold areas because of the low
condensation point. The transformer oil is excellent in gassing performance, and no gas can be easily generated after the transformer oil is used.