In Situ Capacitive Dielectric Sensing for Real-Time Condition Monitoring of Eco-Friendly Vegetable-Oil-Based Nanofluid-Insulated Power Transformers

Transformer insulating liquids need to be assessed to determine the reliability and life of power systems. Traditional diagnostic methods, i.e., Dissolved Gas Analysis (DGA) and tan delta measurements, give correct results, but are expensive, time-consuming, and entail having laboratory-based facilities. This paper presents a cheap method of capacitive sensing for real-time dielectric characterization of nanofluid-based insulating oils in an AD7150 capacitance-to-digital converter. The nanoparticles were prepared through the sol–gel technique and were dispersed in various base oils: blended oil, flax oil, and mustard oil to create nanofluid samples. The measurements of the Capacitance were performed in an oil test configuration in an IEC 60247 and ASTM D150 standard to gain repeatability and accuracy. Experimental findings indicate that various insulating liquids have different ranges of capacitance, with blended oil being the most stable (2.660–2.700 pF), followed by flaxseed oil (1.100–1.180 pF) and mustard oil (2.200–2.500 pF). Statistical data prove that blended oil is the most stable in terms of dielectric performance, whereas mustard oil is quite sensitive to moisture pollution. Analytical validation using electrode geometry creates a strong relationship between capacitance measured and effective dielectric permittivity. Also, economic analysis shows that the intended sensing approach will cut down equipment costs and operating costs by two to three orders of magnitude compared to traditional approaches. The proposed system is an easy, fast, and cheap way of dielectric monitoring and moisture in transformer insulating liquids, and it has high potential to monitor the condition of power systems in real time and for predictive maintenance.