Subsea Power Cable Joint with Compression Ferrule
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Solution Overview
Problem
Subsea power cables require a joint that provides both electrical and mechanical connection without relying on external armouring, as external metallic armour is not feasible for direct electrical heating cables, and existing conductor joints lack sufficient mechanical tension strength for subsea applications.
Innovation Solution
A compression ferrule with multiple compression zones is used to connect conductor ends with internal tension elements, providing a mechanical and electrical connection by compressing the ferrule onto the conductors, which can include central tension elements made of steel or fibres, and filled with a filler material for enhanced strength and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductor joint is made by welding, then electrical connection is achieved, but mechanical tension strength is reduced compared to the unwelded conductor
Solution Approach 1:
The joint structure is segmented into distinct functional zones: compression zones for mechanical connection and electrical connection zones for electrical continuity. This segmentation allows each zone to optimize its specific function without compromising the other, resolving the contradiction between electrical connection reliability and mechanical tension strength.
Solution Approach 2:
Different local regions of the joint have different properties: compression zones with higher mechanical strength for tension bearing, and electrical connection zones with optimized electrical conductivity. This local differentiation allows the joint to simultaneously achieve both high mechanical tension strength and reliable electrical connection.
2Strength
If external metallic armour is used to provide mechanical strength, then mechanical tension properties are improved, but electrical conductivity is compromised for direct electrical heating cables
Solution Approach 1:
The mechanical strength function is extracted from the traditional external metallic armour and relocated to internal tension elements positioned within the conductor. This extraction allows the cable to maintain high mechanical tension properties while eliminating the external metallic armour that would interfere with direct electrical heating function.
Solution Approach 2:
Tension elements are nested within the conductor structure, with the conductor containing the tension elements. This nesting arrangement allows the tension elements to provide mechanical strength from within the conductor, eliminating the need for external metallic armour while maintaining both mechanical and electrical functionality.
3Ease of manufacture
If a joint is made with reduced mechanical properties, then ease of manufacture is improved, but suitability for subsea applications is worsened
Solution Approach 1:
The compression ferrule is pre-formed with predetermined compression zones and geometric features that guide the compression process. This preliminary preparation enables straightforward manufacturing and installation while ensuring the joint achieves the high mechanical properties required for subsea applications.
4Strength
If a compression ferrule with multiple compression zones is used, then mechanical tension strength is improved, but device complexity increases
Solution Approach 1:
The compression ferrule serves multiple functions simultaneously: it provides mechanical compression for tension strength, creates electrical connections through its compression zones, and guides the assembly process through its geometric features. This multi-functionality reduces the need for separate components, thereby managing complexity while achieving high mechanical strength.
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 solution enables a subsea power cable joint with high mechanical tension properties similar to the conductor, allowing for offshore and factory-based splicing and repair, while maintaining electrical conductivity without external armour, thus addressing the mechanical strength and conductivity requirements.
Implementation Method 1
the joint comprises a compression ferrule with a longitudinal aperture, wherein the compression ferrule comprises at least two compression zones that have been compressed respectively onto the first conductor end and the second conductor end
Implementation Method 2
a first conductor end comprising a first tension element is electrically and mechanically connected to a second conductor end with a second tension element
Data Source
Figure 1a~1b
Figure 2~3
Figure 4a~4b
AI summary
A power cable comprising a joint, wherein a first conductor end (33) comprising a first tension element (35) is electrically and mechanically connected to a second conductor end (33') with a second tension element (35'), wherein the joint comprises a compression ferrule (10) with a longitudinal aperture, wherein the compression ferrule comprises at least two compression zones (20) that have been compressed respectively onto the first conductor end (33) and the second conductor end (33') inserted into the aperture of the compression ferrule from opposite sides is disclosed.