Characteristics of acid value in vegetable insulating oil during thermal aging

Acid value is an important indicator used to evaluate the quality of insulating oil. The paper presents the characteristics of acid value in vegetable insulating oil during thermal aging. The individual experiments of hydrolysis and oxidation of vegetable oil were conducted for furthermore analysis to the origin of acidic products in vegetable oil. The quality requirement of acid value which is suitable for vegetable oil was also proposed. The experimental results show that the acidic products in aged vegetable oil mainly come from the hydrolysis of vegetable oil. It is suggested that we must pay enough attention when the acidity of vegetable insulating oil reaches to 2.4 mg KOH/g, because it means the moisture accumulation in insulating paper is already reach 2%.