Bridging Characteristics of Moist Cellulosic Particles in Flowing Transformer Oil

The presence of cellulose impurities in transformer oil can compromise the insulation performance of transformers. Cellulose impurities, characterized by molecular structures containing significant amounts of hemicellulose and hydroxyl groups, tend to adsorb considerable moisture. The bridging behavior of particles in transformer oil is influenced by oil flow. Presently, the bridging characteristics of moisture-laden cellulose particles in flowing transformer oil are not well-defined. In this study, utilizing the established transformer oil circulation device and oil observation system for particles, we conducted research on the bridging characteristics of particles with varying moisture content and different electric field intensities in flowing transformer oil. The features of small bridges in flowing oil were extracted, and the influence of cellulose moisture content on the bridging in oil was elucidated from a force perspective. The results indicate that as cellulose moisture content increases, the electrical conductivity of particles rises, resulting in an increased dielectrophoretic force. Consequently, higher cellulose moisture content makes particles more likely to converge towards regions of higher electric field intensity, specifically the center of the electrodes. The center width of bridges increases, and the leakage current flowing through the electrode gap rises due to elevated cellulose moisture content.