Key technology for the construction and inspection of long-distance underwater tunnel for 1000 kV gas-insulated transmission line

With the rapid development of urbanization and industrialization, electric power consumption continues to increase on a worldwide basis. Traditional overhead transmission lines cannot satisfy the requirements for modernization of power distribution systems. Cable tunnels with ultra-high-voltage and complex network have become the trend of urban power transmission lines for their advantages in flexibility, expandability, and convenient maintenance. Although cable tunnels have good adaptability in power transmission, their application is severely restricted by construction and inspection technologies. Especially for long-distance cross-river tunnels installed with 1000 kV equipment, there is still a lack of reliable solutions to deal with complex challenges encountered during the construction and inspection of ultra-high-voltage cable tunnels. In the present study, complexity features of the first underwater gas-insulated transmission line for 1000 kV power in the world, Sutong GIL Yangtze River Crossing Cable Tunnel, have been analyzed. Engineering challenges encountered during the construction and inspection of long-distance cable tunnel have been discussed. Key technologies including embankment deformation control, gas explosion prevention, synchronous transportation organization, dust-free equipment installation, and robot intelligent inspection have been developed. The application of these technologies has enabled the safe and efficient construction and inspection of a high-quality cross-river cable tunnel.