Trefoil Submarine DC Cable Layout for Simpler Offshore Installation
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Solution Overview
Problem
The installation of dynamic submarine DC power cables requires multiple sets of bend stiffeners, buoyancy modules, and I-tubes, making it cumbersome and crowded, and static DC submarine power cables need separate trenches, complicating the process compared to AC power cable installations.
Innovation Solution
A submarine DC power cable with three stranded cores, including two DC power cores and a dummy element core, forming a trefoil configuration, which simplifies installation by requiring only a single set of buoyancy modules, bend stiffeners, and I-tubes, and a single trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two individual dynamic DC submarine power cables are used for each electric pole, then DC power transmission is achieved, but installation becomes lengthy and the water column becomes crowded with multiple cables and accessories
Solution Approach 1:
The patent merges two separate DC power cables into a single three-core cable structure where two cores carry DC power and the third core is a dummy element. This combining approach reduces the number of separate cables, bend stiffeners, buoyancy modules, and I-tubes from two sets to one set, thereby simplifying installation and reducing water column crowding while maintaining full DC power transmission capability
Solution Approach 2:
The three-core cable structure serves multiple functions: it transmits DC power through two cores while the third dummy core enables the cable to adopt a trefoil configuration that provides mechanical stability and symmetry. This multi-functional design allows a single cable to replace what would traditionally require two separate cables plus additional structural components
2Reliability
If static DC submarine power cables are jointed with dynamic DC submarine power cables, then DC power transmission is achieved, but installation becomes even more cumbersome requiring separate trenches
Solution Approach 1:
The patent combines the functions of static and dynamic cable sections into a single continuous three-core cable structure. By maintaining the trefoil configuration throughout, the cable can be installed in a single trench rather than requiring separate trenches for static and dynamic sections, greatly simplifying the installation process while maintaining DC power transmission capability
3Adaptability or versatility
If an optical fibre cable is added to the dynamic DC submarine power cable, then communication capability is achieved, but a separate set of accessories and an additional I-tube are required at the platform
Solution Approach 1:
The patent embeds the optical fibre cable within the third dummy core of the three-core structure. This nesting approach allows the communication function to be integrated into the existing cable structure without requiring additional I-tubes or separate accessory sets at the platform, as the optical fibre shares the same structural framework as the power transmission cores
Data Source
Figure 1~2
Figure 3
AI summary
A submarine DC power cable (1) comprising: three stranded cores (3a, 3b, 3c), wherein a first core (3a) and a second core (3b) of the three cores (3a, 3b, 3c) are DC power cores, each comprising a conductor (4), and an insulation system (5) arranged around the conductor (4), and wherein a third core (3c) of the three cores (3a, 3b, 3c) is a dummy element having the same outer diameter as the first and the second cores (3a, 3b), or the outer diameter of the third core (3c) deviates at most ±10% from the outer diameter of any of the first and the second cores (3a, 3b), and wherein the third core (3c) in cross-section has a structure that is circular symmetric and which differs from a cross-sectional structure of the first and the second cores (3a, 3b).