Moisture dynamics during pressboard drying

Factory drying of transformer insulation is performed to remove excess moisture from the insulation, which delays ageing and helps in sizing the core-coil assembly before oil impregnation. The rate of drying and cycle time depends on the nature and thickness of the material, temperature and pressure level within the drying chamber, as well as airflow and relative humidity of air, thus making it difficult to obtain universal methodologies for all insulation materials. This paper attempts to explore moisture dynamics of insulation stack (pressboard) that shows significant involvement in height reduction. The article studies the possibility of shorter drying cycle, and the influence that nature and thickness of the material might have on it