The influence of water content on thermal conductivity of paper used as transformer windings insulation

The article presents results of measurements of thermal conductivity of paper impregnated with oil, as a function of water content. The paper (cellulose), impregnated with oil (mineral), is commonly used as transformer windings insulation. Long time of operating increases water content in paper - transformer windings insulation. Water in transformer is mostly treated as negative factor. The measurements of thermal conductivity of the paper were made for water content in range of value from 0.5% to 4.8%. Thermal conductivity was measured for various values of temperature from 25 °C to 100 °C. On the basis of measured thermal conductivity, the influence of water content in paper on temperature in transformer was calculated.