Читать книгу Alternative Liquid Dielectrics for High Voltage Transformer Insulation Systems - Группа авторов - Страница 47

The water content in any dielectric liquid affects the performance of the apparatus containing it. The water holding limit of VO is much higher than that of MO, which is an added advantage in case of NEOs. It also absorbs the moisture present in solid insulation as compared with MO, thus keeping the paper dry and slows down its degradation process in the long run. Natural ester fluids undergo hydrolysis at higher temperatures, consuming the available water from kraft paper and improving its aging characteristics. The water saturation limit of MO is approximately 60 mg/kg [57] whereas vegetable ester oil has 1000 mg/kg [58]. When the moisture content is increased, the dielectric strength of the liquid insulation decreases. When the MO ages, the moisture transfers to the solid insulation like kraft paper and pressboard and degrades its dielectric properties, and thereby decreasing the performance and efficiency of the power transformer. During the operating conditions of a transformer, temperature of the oil increases and the paper then releases water to the transformer oil by undergoing oxidation reaction. This further augments the neutralization value and degrades the oil quality.