Migration and Bridging Characteristics of Cellulose Impurities in Oil-Paper Insulation

For oil-immersed power equipment, the accumulation of cellulose impurities in oil-paper insulation poses a significant problem. To address this issue, this study investigates the migration and bridging characteristics of cellulose impurities in oil-paper insulation under dc voltage. A kinetic analysis model is developed to simulate the impurity trajectories and quantitative analysis of speed, offset distance, and other parameters of cellulose impurities. The results indicate the motion cycle of cellulose impurity under the slightly uneven dc electric field consists of lifting, upward, and downward stages, with a maximum speed of over 102 mm/s and maximum acceleration of over 102 m/s2. During the lifting stage, particle velocity grows quickly and then slows, while during the downward stage velocity increases sharply to a maximum and then gradually decreases. The horizontal offset distance decreases with increased motion cycles. The cellulose impurities departed from the sphere electrode and the insulating paper surface migrate in opposite directions along their respective trajectories. As they gradually approach each other, these impurities undergo collisions and exchange charges, and eventually form a heap-like bridge. Results of this study can guide the development of better insulation materials for high-voltage electrical equipment and aid in the removal of impurities.