Comparison of Electrical Properties of Moistured Pressboard Impregnated with New and Used Synthetic Ester

The paper compares the electrical properties of moistened electrotechnical pressboard impregnated with factory-new and used synthetic ester MIDEL 7131. The tangent of the loss angle as the basic electrical properties of the electrotechnical pressboard impregnated with new and used synthetic ester was tested for four different moisture contents ranging from 0.5% by weight up to 6% by weight. The selected moisture contents correspond to the initial moisture contents of the brand new transformer units and of the transformers that are eligible for replacement. Thanks to the research, it was found out what influence the liquid we impregnate with has on the electrical properties of the moist cellulose insulation.