Insulation is one of the most important parts in the power transformer. Palm oil impregnated paper is investigated to replace the mineral oil impregnated paper due to the high viscosity of palm oil compared to the viscosity of the mineral oil. This paper discussed on ultrasonic radiation technique that was used to reduce the viscosity of the vegetable oil (palm oil) for transformer insulation application. The ultrasonic equipment produces 500W heating power, 240W ultrasonic power at a fixed frequency of 40 kHz. Ultrasonic radiation was applied on oil samples at 30 °C, 50 °C and 75 °C by using the sonicator water bath for several periods of time. The results show up to 42.6 % reduction from the original viscosity of palm oil and proved to have a long term effect on the viscosity of palm oil. The cavitation bubbles that occur in the sample during radiation is one of the mechanism in viscosity reduction.

Oil impregnated insulation paper plays an important role in a transformer as it insulates the windings from high voltage and current. Other than the type of paper used, the properties of oil such as viscosity, relative permittivity and dielectric loss play a major factor that contributes to the quality of the insulation paper. This paper discussed the sonication and esterification process on palm oil and treated waste vegetable oil and its’ effects on the performance of oil impregnated paper. Basically through these processes, viscosity of oils will reduce. However, the resultant permittivity and dielectric loss as well as its’ breakdown strength are rarely reported. Experiments were set to process (sonicates and esterify) the natural oils prior to the paper impregnation process. Results show that esterification is more effective than sonication process in reducing insulation oil viscosity, relative permittivity and dissipation factors as well as increasing the breakdown voltage of the oil impregnated paper. Palm oil methyl ester (POME) could serve as an excellent insulation oil which is very suitable as transformer oil as well as the impregnation medium for paper insulation.