Résumé
Non-destructive thermal techniques have been developed and extensively used during the last decades for space charge measurements in solid dielectrics. These methods are based on measuring and analyzing a transient capacitive current or voltage due to the redistribution of influence charges when a heat flow induced by an external thermal stimulus diffuses through the sample. If this principle is à priori useable on liquids, its application to such materials and appropriate interpretation of the measured signals require assessing and identifying the effects of thermal convection, which is likely to appear when heat diffuses in a liquid medium. This issue is addressed in the present work. Transient current responses of dielectric liquids with two different viscosities containing interface charges are computed numerically in the absence and in the presence of thermal convection when thermal stimuli of amplitudes up to 20 K are applied. The effects of the thermal convection are analyzed and guidelines for reducing them are proposed.