Hideki Kamiyama, Satoshi Hiratsuka, Nozomu Fukuda, Toru Kojima, Shoji Aotani, Osamu Asayama, Koichi Hanada, Masanao Miyashita
The Osaki Thermal Power Line, which traverses Japan's Inland Sea area, is one of the world's largest overhead power transmission lines having two water crossings. To assure adequate over-water clearance for these crossings, a 690-mm2 internally corrosion-proofed KTACSR/EST conductor has been developed, combining high strength and corrosion resistance. It is one of the world's largest conductors providing both high strength and large current-carrying capacity. Cross-wire dampers were also developed to suppress the aeolian vibration that can occur on long spans, together with dead-end clamps for high-strength conductors. Systems for the supervision of helicopter stringing and for over-water supervision were also developed to assure the smooth progress of the conductor stringing work. New aluminum come-alongs were also developed to replace the steel type used previously, reducing mass by approximately 40% and improving stringing efficiency. The stringing method adopted was the semi-prefabrication method, in which the length of conductor to be cut is determined on the basis of measurements of sag made after temporary tensioning.
The overhead water crossings were strung using the conductor, accessories and stringing method described here, and the work was successfully completed in October, 1997.