A Comparative Study of Blended Ester and Mineral Oil with Variances in Refining Processes

Abstract

Transformer oil, made from petroleum, is used all around the world. Due to a lack of petroleum resources, non-biodegradability, and low fire safety, ester-based oil has emerged as the preferred option. Esters are more expensive than mineral oils, and they have lower oxidation stability. A proper blending of ester and mineral oil can be used to alter these parameters. The insulating property of mineral oil is heavily influenced by the source, chemical composition, and refining method. As a result, research into the performance of blended oils of ester and mineral oils with varied characteristics has become necessary. The physicochemical and electrical properties of a mixture of an ester and mineral oils from various refining sources were compared in this study. The experimental study included measurements of tan delta and resistivity at various oil temperatures. Acidity, interfacial tension, pour point, viscosity, oxidation stability, and other characteristics of the oil samples were investigated further. The IEC 60422, IEC 60247, and IEC 61125 guidelines were used to characterize the oil samples for these parameters. The results were compared to mineral oil, which is widely used as an insulating liquid. This study examined the workability of a transformer containing an ester and mineral oil mixture. Based on the comparable results achieved through these experiments, it was found that the presence of ester improved the oxidation stability of blended liquid insulators, irrespective of the quality of MOs.