Behavior Characteristics of Cellulose Particles in Insulating Oil Gaps Under a DC Electric Filed

During the long-term operation of converter transformers, the aging and decomposition of oil-paper insulation lead to the presence of cellulose particles in transformer oil, which affects the safe operation of the equipment. The motion characteristics of cellulose particles in short oil gaps and long oil gaps under a dc electric field are studied. The forces acting on a single particle, the aggregation characteristics of multiple particles, and the conditions for particle chain breakage are calculated and analyzed. An experimental platform is constructed to validate the conclusions. The results show that cellulose particles in transformer oil are subjected to the combined action of various forces under a dc electric field. Under the influence of the dipole force, multiple cellulose particles attract each other and form particle chains along the direction of the electric field. Changes in internal forces within the particle chain can cause the chain to break. The movement of particles in oil is closely related to the adsorption time of particle chains on the electrode surface and their movement time within the oil gap, which is affected by the resistivity, particle size, charge quantity, and external electric field intensity of the particles. In the experiments, particles form cellulose bridges in short oil gaps, while in long oil gaps, they move freely in transformer oil in the form of particle chains.