Assessment of Neutralized Waste Cooking Oil as a Potential Transformer Dielectric Liquid

Abstract

When an oil-immersed transformer fails because of a short circuit, fire can occur because of the relatively low flash point of the mineral insulating oil. One of the ways to overcome this problem is to replace mineral insulating oil with vegetable-based insulating oils of higher flash points.This study explores the potential ofwaste cooking oil as a transformer dielectric liquid. The waste cooking oilused in this studyis a vegetable-basedoil with a high flash point.However, its acidity is above the permissible limit, which hinders its use intransformers. Therefore, the waste cooking oil was neutralized with caustic soda (normality: 1.0, 2.0, 3.0, 4.0, and 5.0N) at a temperature of 70°C and stirring speed of 400 rpm for 5 min.The physical, chemical,andelectrical properties of the neutralized waste cooking oil samples were determined. The results showed that the waste cooking oil neutralized with caustic soda (normality:2.0N) had the lowest acidity (0.2825mg KOH/g). The breakdown voltage and viscosity of this oil sample were 29kV and 40.92 mm2/s, respectively, which fulfilled the specifications ofthe IEEE C57.147standard. In addition, this oil sample had a flash point of 260°C, which fulfilled the requirement of the IEC 62770 standard. Based on these results, it can be concluded that the neutralized waste cooking oil sample (normality: 2.0 N) has potential as a transformer dielectric liquid.