Rubber Particles Motion in Mineral Oil Under AC Voltage by Schlieren Imaging and Numerical Simulation

Transformer oil is inevitably contaminated with impurity particles during actual transformer operations. The motion of these impurity particles in transformer oil poses a potential threat to the insulation performance. While many studies have researched the motion of fibers, metals, and carbon particles causing breakdown in transformer oil, research on rubber particles remains unexplored. Due to aging, rubber components in transformers partially detach and suspend in the transformer oil in the form of particles. This study establishes the breakdown test platform for the mineral oil under ac voltage. Using the high-speed camera and Schlieren imaging method, the motion characteristics of rubber particles in the mineral oil and their impact on mineral oil breakdown are investigated. Meanwhile, through fluid-electric field coupling simulation, the motion characteristics of rubber particles from individual motion to collective behavior are analyzed. The results indicate that the particles outside the electrode gap presented different movement trends, determined by their initial spatial location and size, whereas rubber particles inside the electrode gap begin to reciprocate and aggregate into walls, raising the breakdown probability. This study is helpful for a better understanding of the impact of impurity particles on the insulation performance of transformers.