Cable installation technology of the duct system in Japan

摘要

Since severe restrictions are put on the excavation of roads in Japan, the duct installation system, instead of direct burial installation system, is used for installing underground cables. Depending on the specifications to which roads are constructed, certain regulations in Japan forbid the excavation of a road for as long as 5 or 10 years. Also, road construction work is generally restricted to the period from 09:00 to 17:00, and roads must be opened for vehicular traffic during the night. Duct installation system, which functions very well against such regulations in contrast to direct burial installation system that requires a long-time occupation of a road, is generally preferred in Japan. Many technological developments and applications are made for this duct installation system, and at present, the system is used in 70% of all installation work for 66 kV class cables in Japan.rnIn this paper, various innovations implemented for the duct installation system, such as a technology for installing longer cables than before in Japan, are introduced. Furthermore, an economic advantage of duct installation system over direct burial installation system and other advantages in terms of environmental concerns and maintainability are also described.