An Experimental Investigation on the Synthetic Ester Circulation for Drying Cellulose Insulation in Distribution Transformers

Abstract

Water can cause damage to power transformers by accelerating aging processes, reducing the dielectric margin, decreasing the partial-discharge inception voltage, and increasing the risk of unexpected failures. Modern electrical companies utilize a variety of drying techniques but sometimes do not comprehend them, making drying less effective. To address these challenges, this study proposes the application of synthetic ester to dry distribution transformers because water dissolves better in the ester than other dielectric liquids. An improved laboratory model of transformer insulation was used for the investigation. This model dried the ester using a molecular filter and carefully selected adsorbed weight. Pressboard strip water content before and after drying was analyzed to determine the drying efficacy of the cellulose insulation. The water content was measured using the Karl-Fischer titration method. The investigation proved that the drying procedure worked. At an ester moisture level of 105-120 ppm and an insulation system temperature of 70°C, samples dried for 5 days showed above 1% water loss. The experimental investigation demonstrated the high efficiency of the proposed drying method for distribution transformers.