Investigation of performance characteristics of blended mineral oil and ester oil for transformer application

Abstract A transformer is one of the most important high voltage (HV) power apparatus in any electrical system. In transformers, liquid insulation, primarily mineral oil, is used in bulk. It acts as an insulation and cooling medium in the transformer. Therefore, it plays an important role in the safe and reliable operation of the transformer. It is understood from several studies that because of the shortage of petroleum oil and its non-environment-friendly nature, scientists, engineers, and researchers are concentrating their studies on synthetic oil, natural ester oil, so that they can replace mineral oil successfully. Studies related to the characterization of different types of natural ester oil are made for their superiority over mineral oil. However, very few studies have been conducted on different combinations of mineral oil (MO) with natural ester oil, such as coconut oil (CO) and rice bran oil (RO), as an alternative insulation. In this paper, a study has been made on different combinations of MO with CO and RO for their performance characteristic studies like breakdown voltage (BDV), flash point, DC resistivity, and tan delta on the lines of International Electrotechnical Commission (IEC) and American Society for Testing Materials (ASTM) standards. It is observed from the studies that different combinations of MO with CO and RO enhanced its BDV, which is the prime electrical property for studying the dielectric strength of any insulation. However, blended RO with MO has balanced properties in terms of dielectric strength, flash point, and DC resistivity compared to all other virgin oil and blended oils. It is also less toxic compared to the mineral oil. Therefore, blended rice bran oil with mineral oil may be considered an alternative to traditional mineral oil as it is cost-effective and less toxic. Therefore, it may be an efficient alternative to insulating oil for the transformer industries.