A study on electro-thermal-physical properties of mixed mineral oil and vegetable oil as an alternative for liquid insulation in power transformers

Abstract

ABSTRACT The power transformer plays a crucial role in the power system’s network for distributing power. The efficient operation of power transformers is mainly based on the efficient liquid insulation used for cooling purposes. Mineral Oil (MO) derived from petroleum is traditionally used for insulation in power transformers. However, its lower thermal degradation and thermal conductivity may influence the performance of the transformer. The non-degradable property and low flash and fire points also affect environmental safety. The aforementioned attributes encouraged researchers to propose an alternative transformer oil for power transformers. In literature, various studies have been carried out to analyze Vegetable Oil (VO) as an alternative to petroleum-based MO; However, due to high viscosity, acidity may affect the performance of the transformer. Hence, this article proposes mixed MO with VO as an alternative for liquid insulation in power transformers. This study uses different ratios of coconut oil, palm oil and sunflower oil for investigation with MO. The experimental results show that the electrical, thermal, and physical properties of mixed transformer oil are better than those of MO and VOs. The results show that a higher proposition of VO has shown better performance. The thermal conductivity of mixed VOs with MO has increased by 6–10% compared to the MO. Both flash and fire points of mixed VO with MO increased by 50–70% compared to MO. The load has been performed to analyze the efficiency and operating temperature of the transformer; results show that the mixed VO with MO combination has 32.3% higher efficiency and 16 ∘ C lower operating temperature compared to MO. Further, the various aging characteristics of the transformer oil are also discussed in this study.