Optimization of impregnation process for HV transformers
Optimization of the impregnation process of the high-density cellulosic materials for high-voltage power transformers
In high-voltage power transformers, paper and high-density wood impregnated oil have become prime insulants. For the full scale transformer, life of 40+ years is expected. Therefore, the proper level of the insulation quality must be assured. More specifically, paper and high-density wood elements must be fully impregnated with oil. That implies that gas bubbles and so partial discharges (PD) are not tolerable.
The impregnation process takes place under vacuum for 48 hours. The temperature is elevated to speed up the material penetration by the oil. After the impregnation, the post-impregnation period start to complete voids filling by the oil.
To optimize the manufacturing process of high-voltage high-power transformers, the post-impregnation period should be optimized in first place. For this, it is necessary to research and determine the parameters influencing the oil ingress into the cellulosic material. Further on, the modelling of the impregnation speed with respect to the influencing parameters such as temperature, pressure, material volume and shape of the material, is to be done. In the end, the possible decisions with respect to the shortening of the post-impregnation period are to be made.