AbstractNatural esters usually show higher dielectric losses, a higher conductivity and higher viscosity. It has become clear that more research is required to ascertain the long-term safe operation of transformers where natural ester is used. This paper made comparative experimental analysis of the cellulosic particles accumulation and its effect on the electric field distribution in natural ester and mineral oil under AC electric field. When the AC voltage was applied on the oil with cellulose particles, it is worth noting that in mineral oil, the particles were concentrated at the end of the spherical positive and negative electrodes, while in the natural ester, the particles are concentrated in the sphere of the positive and negative electrodes. The adsorption of fiber particles decreases the field intensity near the spherical electrode, however, increases the field strength in the middle region of the electrode. Besides, in the case of particles adsorbed on the electrode surface, the maximum electric...