Oxidation Characteristic Changes in Insulation Oil Depending upon Storage Environments and Oil Resources

Mineral oil has been widely used as an insulating oil for electrical transformers for a long time, but the necessity of employ- ing new insulation oil such as vegetable oil has been increased due to urgent needs for the biodegradability when it leaks and also for the thermal stability at a higher operation temperature. Although specific periods are required between the pro- duction and consumption, there are still short of the data to prove the insulation oils' storage stability depending upon various circumstances and their resources. Thus, this paper demonstrates the insulation oils' oxidation characteristics of both mineral and vegetable oils when each was exposed to different environments for 12 weeks. From this test, some properties including total acid number, water content and dielectric breakdown were changed under specific conditions and resources. Vegetable oils showed higher hydrophilicity and water saturation than those of mineral oils due to their molecular compositions. Under sunlight exposure condition, all insulation oils oxidized and changed their properties when exposing to the direct light, regard- less of the resource used.