Development of DC Deep Water Submarine Cable (Single Core Type of Water Depth 1500m)

Considering optimization of the laying route for submarine power cables off the coast of Japan, there are many deep-water areas over depth of 1000m. In Japan, submarine power cables have been installed at a depth of about 300m as maximum, however, there is no track record beyond that level. The laying depth is deeper, the laying tension is larger. Therefore, as a result of discussion on the cable structure and material suitable for the laying in deep water, the aluminum conductor with keystone structure was applied for reducing the cable weight since the laying tension is proportional to the product of depth and weight. In this study, the prototype submarine cables of DC 500kV class (transmission capability of 1 GW) equipped with the double steel wire armour were manufactured, then mechanical and electrical properties were evaluated in accordance with CIGRE TB 496 and TB 623. As a result, the cables of our design, on which the tensile bending test had been carried out in advance, passed the high-voltage 30 days load cycle test followed by the lightning impulse test without any defect.