Investigation of dielectric properties of blended ester oils and dielectric fluids used in transformer at different temperatures

Abstract

The insulating oil is the most critical element of the transformers. For better performance of the transformers, the dielectric properties (AC Breakdown voltage (AC BDV), DC BDV, dielectric losses, and insulation resistance) should be in a considerable range. In the present scenario, mineral oils are used as dielectric insulation oil in the transformers, which is very hazardous to the environment as well as has a limited resource. In the present work, the dielectric behavior of blended ester oils (Natural and Synthetic) and mineral oil at different temperature levels have been investigated by using a 100 kV motorized AC/DC breakdown voltage test set and loss tangent, permittivity, and resistivity test set. The results revealed that the blend of coconut oil and synthetic oil (M4) gives better dielectric properties, i.e., AC BDV increases by about 51%, and DC BDV increases by 61% as compared to mineral oil. Thus, it is established that blended ester oils can be an alternative to traditionally used mineral oil.