Dielectric Losses Associated with Electric Field Induced Miotion in Insulating Oil

The results of an experimental investigation of the contribution of liquid motion to the dielectric loss in insulating oils are presented. It is shown that the onset of filamentary liquid motion is associated with a strong increase of dielectric loss. The threshold field for the increase in dielectric loss increases with the square root of the frequency of the applied voltage. It is shown that the threshold field agrees with the theoretical expression previously derived for instability created during one cycle as the result of strong charge injection.