On the gassing of dielectric liquids

Abstract

The physico-chemical processes involved in the gassing of dielectric liquids are studied with a uniform field test cell containing a disc-shaped gaseous bubble. When a constant AC voltage is applied to the cell, there is a time-evolution of discharges which depends on the nature of the liquid, the gas, and of the operating procedure. For gas absorbing liquids it is possible to define and derive a gas absorbing coefficient G as the ratio of molecules absorbed by the gas per unit time to the number of electrons involved in the discharge per unit time. The proposed method allows a quantitative measurement of G to be made, and a comparison of different liquids. The influence of various parameters such as temperature, liquid viscosity, gas bubble thickness is studied and discussed. As expected, voltage amplitude and frequency have no influence upon G. Possible mechanisms of gassing are considered, and a tentative classification of liquids is proposed.