Abstract
Recently, an unknown type of fracturing sometimes occurred to the plastic sheathed hard-drawn stranded copper conductor of the overhead cable that had been used for several years. The present paper describes the assumed cause and the confirmed mechanism of this fracturing. Copper wires in the conductor fractured, without necking down, into pieces of several centimeters in some cases. The cracking initiated at the wire surface on which the maximum tensile stress was applied. The wires were found to have been wet and immersed in corrosive rain water which penetrated into the strand through cable joints. It is likely that this type of fracturing of the conductor belongs to the stress corrosion cracking of copper wires. The hard-drawn copper strand experimentally subjected to the corrosive atmosphere of moist vapor of sulfuric acid under a tensile stress was found to fracture in the same manner as that of the strands practically used.
