Submarine Power Cable Moisture Buffer Zone for Flexible Joints
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Solution Overview
Problem
Existing submarine power cable systems face issues with fatigue-related failures in radial water barriers, particularly in dynamic cables, and the use of prefabricated joints is not suitable for wet applications due to moisture sensitivity, limiting repair options.
Innovation Solution
A submarine power cable system comprising a wet design power cable section with a helically laid metal screen layer and a static power cable section acting as a moisture buffer zone, connected via a flexible joint, which includes a metallic radial water-blocking sheath to prevent longitudinal water ingress and facilitate connection to subsea components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a radial water barrier is used in dynamic power cables, then moisture protection is improved, but fatigue-related failures occur due to radial water barrier degradation
Solution Approach 1:
The patent removes the radial water barrier from dynamic power cables, extracting the problematic component that causes fatigue failures. The dynamic cable section is designed as a wet insulation system without hermetic sealing, eliminating the radial barrier that degrades under fatigue conditions while accepting controlled moisture presence through the water-blocking layer.
Solution Approach 2:
The patent applies different moisture protection strategies to different cable sections: the dynamic cable section uses a water-blocking layer that allows controlled moisture presence, while the static cable section uses hermetic sealing with radial water barriers. This local differentiation optimizes each section for its specific operational conditions.
2Ease of repair
If prefabricated joints are used in static power cables, then repairability is improved, but moisture sensitivity increases making them unsuitable for wet applications
Solution Approach 1:
The patent introduces a water-blocking layer as an intermediary between the dynamic wet cable section and the static dry cable section with prefabricated joints. This intermediate moisture buffer zone protects the moisture-sensitive prefabricated joints from direct exposure to water while allowing the dynamic section to operate in wet conditions.
Solution Approach 2:
The cable system is segmented into distinct wet and dry sections with clear functional boundaries. The dynamic cable section operates as a wet system with flexible joints, while the static cable section uses dry hermetic sealing with prefabricated joints, allowing each segment to be optimized for its specific requirements.
3Object-affected harmful factors
If a hermetically sealed radial water barrier is used in static power cables, then moisture protection is improved, but the consequence of failure is limited only to the dynamic cable section
Solution Approach 1:
The patent converts the potential harm of moisture ingress in the dynamic cable section into a benefit by designing the water-blocking layer to allow controlled moisture presence. This approach accepts that the dynamic section may contain moisture but prevents it from affecting the static section, turning a potential failure mode into a design feature that isolates failures to specific sections.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system allows for easy connection and repair of wet design power cables to subsea components by acting as a moisture buffer, reducing moisture ingress and enabling the use of flexible joints, thus enhancing reliability and repairability.
Implementation Method 1
a metallic radial water-blocking sheath arranged around the second insulation system section
Implementation Method 2
the static power cable section comprising a second conductor section connected to the first conductor section and a second insulation system section connected to the first insulation system section by means of a flexible joint
Data Source
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AI summary
A submarine power cable system comprising: a wet design power cable section (1a) comprising a first conductor section, a first insulation system section arranged around the first conductor section, and a screen layer formed by one or more of helically laid elongated metal elements arranged around the first insulation system section, and a static power cable section (1b), which is a moisture buffer zone, comprising a second conductor section connected to the first conductor section and a second insulation system section connected to the first insulation system section by means of a flexible joint (1c), the static power cable section (1b) further comprising a metallic radial water-blocking sheath arranged around the second insulation system section, wherein the metallic radial water-blocking sheath is electrically connected to the screen layer, and wherein, from the flexible joint (1c) to a far end of the static power cable section (1b) the submarine power cable system has an axial length in a range of 1-1000 m, the far end being arranged to be connected to or being connected to a subsea electric component.