The impulse strength of fully-impregnated-paper dielectrics as used in high-voltage cables

An investigation into the impulse strengths of model cables and cable-impregnating oils and compounds is described. In particular, the effects of the density, air impermeability and thickness of the paper and the dielectric thickness and temperature of the impregnant have been studied. Special papers possessing a combination of properties designed to give a high impulse strength have been incorporated in an experimental oil-filled cable and the improvements obtained closely approach those indicated by measurements on model cables. An impulse breakdown mechanism in a fully-impregnated-paper cable dielectric is suggested whereby the impulse strength, although it may be varied by changing the properties of the paper, is shown to be primarily dependent on the impulse strength of the impregnant.