Dielectric Strength Compatibility for Coconut Oil as a Transformer Insulating Oil

Abstract

Petroleum-based mineral oil is being used dominantly as transformer oil for more than a century for its excellent dielectric properties. Taking into account the source is derived from nonrenewable energy, efforts have been made to find a comparable substitution of conventional mineral oil. In this paper, a comparison is being made for the dielectric strength of two different types of coconut oil i.e. Virgin and RBD grade with that of conventional mineral insulating oil based on the experimental results. In dielectric strength, AC and Impulse breakdown voltage tests were carried out along with moisture contrent and dielectric dissipation factor of the samples. From the results, it was seen that Virgin and RBD grade coconut oil is having an AC breakdown voltage of 48.7 kV and 51.5 kV, which is 25% and 32% higher than that of mineral oil 38.9 kV. Further the results of 50% impulse breakdown voltage show that Virgin and RBD grade coconut oils are having a slightly higher breakdown value of 148.6 kV and 147.7 kV respectively, than mineral oil which is 140.8 kV. For tan delta tests, RBD grade coconut oil is having the lowest value of dissipation factor 0.011718, which is 77% lower than mineral oil 0.050459 and that of virgin coconut oil is 0.044075, which is 13% lower than mineral oil. Overall, it was found that the dielectric strength of coconut oils is better than mineral oil and has positive potential for replacing it.