Microbubble Detection in Transformer Oil by Means of Compressive Digital Holography

Power transformers are crucial parts of electrical power distribution systems. In wet type transformers, the temperature is regulated by using organic oil. Over time, the oil and materials inside the transformer can degrade, creating small, microscopic particles. Together with the increase of moisture, such particles can be hazardous as they can reduce the operational life of the transformer due to the decrease of dielectric strength of the insulator. The existence of microbubbles in transformer oil caused by moisture vaporization is a sign of degrading transformers. Thus, detecting and quantifying microbubbles is essential to prevent potential damage and ensure reliable transformer operation. In this study, compressive digital holography is utilized to capture the digital hologram of microbubble suspended in transformer oil. Then, by reconstructing the object using a compressive sensing approach, the localization of microbubble inside transformer oil can be determined. Compared to conventional digital holography, compressive holography yields better image reconstruction due to removal of background noise. The experiment conducted ex-situ demonstrates the potential of this technique in detecting microbubbles in transformer oil, thus offering a promising solution for enhancing transformer reliability and safety.