DefinitionAn oil - filled cable is defined as a cable where low - viscosity oil is maintained under pressure, either within the cable sheath itself or in a containing pipe. Under all conditions of varying loads, the oil in the cable fills the voids in the oil - impregnated paper. Historically, mineral oils were commonly used, but more recently, alkylates such as linear decyl benzene and branched nonyl benzene have gained popularity. This is due to their low viscosity and their ability to absorb