Abstract
We T.E.C. have commenced to develop the O.F. cable in April, 1977. Now we have finished the Type-Test and produced in full-operation of 154KV 1x600mm$^{2}$ and 154KV 1x1200mm$^{2}$ O.F. cables. Especially we have completed pulling and splicing of the 24.82kms O.F. cable in KaeBong-OuRyu Route, and now it is operating well. This has important meaning that Extra High Voltage Under Ground Transmission Line has constructed by domastic engineers for the first time in Korea. Thank to arrange and publish it, and hope it can be helpful to the related.