Large-Scale Tests for Identifying the Nonlinear, Temperature-Sensitive, and Frequency-Sensitive Bending Stiffness of the NordLink Cable

The NordLink project is a cooperation between Statnett, TenneT, and KfW to build a subsea High Voltage Direct Current (HVDC) system between Norway and Germany. The cables are produced by Nexans Norway and ABB. This paper presents the main results of 30 bending stiffness tests run on the NordLink cable using a novel, dynamic bending stiffness test rig developed by Nexans. It is concluded that there is a highly nonlinear bending moment vs. bending curvature relationship. Also, this relationship is most sensitive to the temperature and somewhat sensitive to the frequency of the cable oscillations. Within a realistic range of curvature amplitudes, temperatures, and frequencies, the bending stiffness varies from 12 to 124 kNm². These observations strongly suggest that the common industry practice of using a constant bending stiffness should be abandoned.