High-field conduction and interfacial phenomena in a thin dielectric liquid layer

The author reports experimental work on the AC conduction phenomena of a thin dielectric liquid (capacitor impregnant) layer at high electric field for several interfacial situations. The features revealed by these experiments show a strong dependence of the liquid electric losses (at a frequency of 50 Hz) according to whether the liquid is in contact with a metallic or a polymer interface. An attempt is made to elucidate these measurements in terms of the existing theories of ionic conduction in non-polar liquids: it turns out that charge-carrier injection in the neighbourhood of the interface is the dominant contribution of the high-field liquid conductivity. A theoretical evaluation based on the unipolar injection model is given in agreement with the experimental results obtained in the different configurations