Dielectrometry measurements of effects of moisture and anti-static additive on transformer board

Abstract

Moisture in solid insulation has detrimental effects on transformer life. When the system is not in equilibrium laboratory measurements with multiple wavelength interdigital sensors using the imposed frequency-wavenumber (/spl omega/-k) dielectrometry technique have proved to be an effective way to measure complex permittivity distribution in solid insulation which is directly related to the moisture distribution. Measurements of oil-free and oil-impregnated pressboard using interdigital sensors with changes in ambient moisture concentration are presented. A comparison between existing moisture equilibrium curves for the oil-paper system and experimental results is given. Measurements are also performed for anti-static additive in oil and the dielectrometry effects are discussed.