Novel Method Using Transformer Moisture Equilibrium for Removal of Absorbed Moisture from Cellulose Paper Insulation in Power Transformers

Moisture's effect on the ageing of Kraft insulation paper is well established theory. The removal of moisture from transformer paper insulation is a time-consuming task. Although methods for initial vacuum drying are available, the same process is impractical in an aged transformer in service. This paper proposes a new methodology, the heating and cyclic filtering process (HCF) that uses the moisture equilibrium concept to estimate and reduce moisture in transformer winding cellulose paper. The dynamics of cellulosic moisture content in response to cyclic temperature variation, as well as their impact on insulation ageing, are also being investigated. The experimental results were compared to current conventional methodologies. This paper also establishes an empirical correlation between Tan Delta, Polarizing Index, and Breakdown Voltage and moisture level to predict insulation moisture level. The results of the experiment confirm that the HCF process, which avoids vacuumizing the tank, is highly compatible with aged transformers.