Characterization of Electrical Stress of Natural Ester Under Impulse Empirical Analysis

Abstract

Transformer is an important component in power system. Lightning impulse will cause an overvoltage that will damage the transformer. Hence, transformer need an insulation that can protect it and withstand lightning impulse. Mineral oil (MO) was the most commonly used oil as liquid insulation. Although MO provide an excellent performance in transformer, it still gives bad impact due to it low flash point, fire point and not biodegradable. Virgin coconut oil (VCO) offer a great potential for replacing MO as an insulating in transformer due to it high flash point, high fire point and biodegradable. This project presents the examination of breakdown voltage of both oil at both polarity, with and without copper particle, and at thermal aging and before thermal aging. Test conducted under uniform field sphere-sphere with lightning impulse voltage. Breakdown test were conducted according to ASTM 3300 standard for lightning impulse by using rising method. For thermal aging process, oil sample being heated at 100 °C for 100 hours. BDV for negative polarity was higher compared with positive polarity. Influence of thermal aging and void contamination shows that there was reduction in BDV of oil sample. Result shows that, although BDV for VCO under all condition is lower compared with MO, but it is still comparable and acceptable.