| 摘要 |
PURPOSE:To improve a lightning-proof property and strength of an electric cable, and prevent the fusion breaking by a thunderbolt, by stranding plural lightning-proof strands consisting of a steel core material and a covering material made of aluminum or an aluminum alloy around a main cable as an electric wire or an earth wire and eccentrically placing the core material inside the covering material for at least one strand among them. CONSTITUTION:An electric cable is composed of an overhead earth-wire 1 containing an optical fiber of the outside diameter 5mm and one strand 2 and five strands 2a stranded around the overhead earth-wire 1. The strands 2, 2a are made nearly to be a sector in the cross sections and stranded together to form the outside diameter of 10.5mm and cover around a pipe 5. The strands 2, 2a are composed of respective steel core materials 6, 6a and covering materials 7, 7a made of aluminum or an aluminum alloy which are formed by covering the core materials 6, 6a around. A portion which is the large circular side of the strand 2 in the covering material 7 is of 2.5mm in the thickness and of 5.5mm in the maximum width and made thicker than that of the other strands 2a, accordingly its outer edge is protruded like a fin, and the core material 6 is placed in a deflected position from the center of the strand 2 to the small circular side. With this constitution, the protrusion of the covering material 7 functions as a fusion loss allowance against a thunderbolt. |
