The dielectric breakdown strength of transformer oil based magnetic fluids: effect of magnetic field strength and exposure time

• Published in: Journal of materials science. Materials in electronics Vol. 33; no. 21; pp. 17113 - 17124
• Main Authors: Jadav, Mudra, Upadhyay, R. V., Parekh, Kinnari
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.07.2022; Springer Nature B.V
• Subjects: Bubbles; Characterization and Evaluation of Materials; Chemistry and Materials Science; Dielectric breakdown; Dielectric strength; Exposure; Field strength; Magnetic fields; Magnetic fluids; Manganese zinc ferrites; Materials Science; Nanoparticles; Optical and Electronic Materials; Transformers; Zinc ferrites
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-022-08587-x

Dielectric breakdown of transformer oil (T-oil) and T-oil based magnetic fluid containing Mn–Zn ferrite nanoparticles is investigated in the absence and presence of magnetic fields. The influence of the time of exposure to the magnetic field on the breakdown voltage of the magnetic fluid Mn–Zn is reported for the first time. Visual evidence of bubble formation due to elevated electrical stress on the T-oil is captured to understand the BDV mechanism in the T-oil. The displacement of bubbles in relation to time is studied. This confirms the formation of bubbles and the propagation of the streamer as the mechanism responsible for the dielectric breakdown in T-oil. The T-oil based magnetic fluid containing Mn–Zn ferrite nanoparticles (1.003 vol.%) showed a 40% increase in the BDV value in comparison with pure T-oil. The increase in BDV of magnetic fluid is explained using the concept of nanoparticles acting as electron scavengers and modifying the breakdown process significantly as compared to that of T-oil. A rise in BDV over exposure time is observed at a given magnetic field. The maximum BDV enhancement in the presence of a magnetic field (20.1 mT and 20 min exposure time) is 78% when compared to pure T-oil. Improving BDV by adding magnetic nanoparticles can allow this oil to be used in higher power transformers.