Engineering Physics Annotation << Back Temperature Field of Solid Cellulose Insulation of a Power Transformer With SF6 Oil Bubbling Khismatullin A.S. The formation of a temperature field in solid cellulose insulation of a power oil transformer winding is investigated under changing conditions of external heat exchange at the boundary with transformer oil. The effect of SF6 gas bubbling is described through the effective heat transfer coefficient on the outer surface of the cylindrical insulating layer. An axisymmetric thermophysical model is formulated that takes into account the thermal conductivity of impregnated cellulose, linear heat generation in the conductor and convective heat transfer into a two-phase oil-gas medium. An analytical solution is obtained for the stationary heat conductivity problem with a boundary condition of the third kind, allowing for a separate assessment of the contribution of the thermal resistance of the solid dielectric and the resistance of external heat transfer. It is shown that an in-crease in the heat transfer coefficient during SF6 gas bubbling leads to a decrease in the temperature of the hottest region of the insulation and a decrease in the thermal inertia of the system. The calculated results are compared with test data from a scale model of the transformer. The temperature difference does not exceed 2°C for the main bubbling modes. A range of gas flow rates has been established that achieves the greatest thermophysical effect without excessively increasing bubbling. The obtained dependencies can be used to assess the thermal state of solid insulation and select rational cooling modes under overload conditions of a power oil transformer. Keywords: transformer oil, SF6 gas, dielectric, temperature field, cellulose insulation, bubbling, heat transfer coefficient. DOI: 10.25791/infizik.7.2026.1564 Pp. 14-20.