Bubble Migration and Accumulation in Oil-Paper Insulation: Interfacial Forces Modeling

• Published in: IEEE transactions on dielectrics and electrical insulation Vol. 31; no. 5; pp. 2425 - 2432
• Main Authors: Sun, Yuhan, Zhang, Qiaogen, Wu, Zhicheng, Guo, Chong, Wang, Shaoqi, Tan, Shitianyi
• Format: Journal Article
• Language: English
• Published: IEEE 01.10.2024
• Subjects: Bubble; Drag; Force; Friction; Insulation; interfacial force; Mathematical models; Microscopy; migration and accumulation; oil-paper insulation; Oils
• ISSN: 1070-9878; 1558-4135
• DOI: 10.1109/TDEI.2024.3356447

Bubbles in oil-paper insulation migrate and may finally accumulate, posing enormous insulation risks. Accurate simulation of bubble migration and accumulation is of vital importance. The cross-scale nature of micrometer-millimeter bubble movement in meter-scale oil-paper insulation structures makes macroscopic simulation methods often ignore the microscopic details of bubbles, which makes calculation accuracy hard to guarantee. In this study, bubble dynamics in oil-paper insulation are analyzed by the Euler-Lagrange approach, in which the distributed interaction on the bubble interface is simplified to lumped interfacial forces. The lumped bubble-oil drag force and bubble-paper friction are standardized measured, and effectively modeled combining the microscopic behaviors of bubbles. The accuracy of the Euler-Lagrange method with modeled interfacial forces is finally verified by experiment. Results show that the deformation of a steady-rising bubble in oil intensifies as bubble size increases, which has an enhanced effect on the drag force. The bubble-paper contact state and paper friction are affected by bubble-paper contact pressure and bubble motion inertia. The bubble slides in close contact with the paper when contact pressure dominates while sliding without contact when bubble inertia dominates. Both the drag force and paper friction are effectively modeled considering these bubble microscopic behaviors. The agreement between simulation results and experimental results of bubble trajectories and accumulation behaviors in a horizontal oil channel is satisfactory, verifying the accuracy of the simulation method with modeled interfacial forces. This method can be further coupled with multifield simulation realizing the precise bubble distribution analysis in oil-immersed power equipment.