Aggregation Characteristics of Cellulose Particles of Different Sizes in Transformer Oil Under DC Electric Field

Under dc electric field, the migration and accumulation of cellulose particles in transformer oil will affect the oil insulation strength, thus threatening the normal operation of the converter transformer. In this work, a cellulose particle behavior observation platform is constructed, and the behavioral characteristics of cellulose particles of different particle sizes in transformer oil are analyzed through experimental and theoretical comparisons. The results show that the particle chains formed by large-sized cellulose particles extend relatively faster on the electrode surface, with relatively longer length and sparser distribution, making it easier to form stable cellulose bridges within the oil gap. Correspondingly, small-sized cellulose particles are difficult to form stable cellulose bridges in the oil gap. The increase in cellulose particle concentration has limited impact on the length of particle chains, thus it remains challenging for small particles with higher concentrations to form bridges. The external field force primarily influences the movement of particles between the electrodes, while the interparticle force mainly impacts the aggregation effect of the particles. Dipole interactions dominate in the formation of particle chains and are relatively stronger between ellipsoidal particles.