| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an optical-fiber composite overhead ground wire which can rapidly and nondestructively detect pinholes, corrosion holes, cracks or the like generated in its metal tube, and to provide a maintenance method for detecting pinholes, corrosion holes, cracks or the like generated in a metal tube used for the optical-fiber composite overhead ground wire. SOLUTION: With the optical-fiber composite overhead ground wire with one or more layers of metal wires 5 stranded around an outer periphery of a metal tube 4 housed in an optical fiber 2, helium gas at a metal tube internal pressure of 2 kgf/cm<2> or higher is sealed in the metal tube; and when a pinhole, a corrosion hole, a crack or the like is generated at the metal tube for the optical-fiber composite overhead ground wire, the maintenance method detects internal pressure change in the metal tube and/or location of leak of helium gas sealed in the metal tube with a sensor which reacts with the gas.</p> |
