Submarine Power Cable Copper Sheath Welding Seam Integrity
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Solution Overview
Problem
High voltage power cables face challenges in withstanding water penetration under high pressure conditions at deep underwater depths due to defects in the welding seam of the copper barrier, which can lead to electrical breakdown.
Innovation Solution
A protective strip coated with a metal or metal alloy having a melting temperature between 90°C and 250°C is applied under the welding seam of the copper barrier, which melts and binds during the heating process, sealing defects and protecting the polymeric layers from heat and vapor damage, ensuring the welding seam's integrity at extreme depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding is performed to create the copper barrier, then the barrier integrity is improved, but heat and vapor can damage the polymeric layers of the cable core
Solution Approach 1:
The protective strip acts as an intermediary layer positioned between the welding operation and the polymeric insulation layers. This intermediate barrier absorbs and redirects heat away from the sensitive polymeric materials, preventing thermal damage while still allowing the welding process to create an integrity-tight copper barrier.
Solution Approach 2:
The protective strip is placed in advance of the welding operation to cushion the polymeric layers against the harmful effects of welding heat and vapor. This preparatory protective measure ensures that the polymeric insulation is already shielded before the thermal stress of welding is applied, preventing damage to the cable core structure.
2Stress or pressure
If the welding seam is made robust to prevent water penetration at great depths, then the pressure resistance is improved, but the complexity of ensuring defect-free welding increases
Solution Approach 1:
The protective strip is a simple, inexpensive, single-use component that is applied during manufacturing and serves its protective function throughout the cable's operational life. This disposable element provides robust pressure resistance at the welding seam without requiring complex welding procedures or expensive quality control systems, as the strip itself prevents defect formation.
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 effectively prevents water penetration and protects the cable's polymeric layers, ensuring the power cable can withstand pressures at depths of up to 2000 meters by sealing defects and maintaining the integrity of the welding seam.
Implementation Method 1
heating the protective strip and the copper barrier at a temperature higher than the melting temperature of the coating of the strip so that the coating fuses in the welding seam
Implementation Method 2
the coating fuses in the welding seam
Data Source
Figure 1
Figure 2
Figure 3a~3c
AI summary
Process for manufacturing a power cable (100) comprising: providing a power cable core (110) comprising an electric conductor (115) and having an outer diameter; providing a copper foil (300) having a width such that, after folding of the copper foil (300) to provide a copper sheath (120) around each power cable core (110), the copper sheath (120) has an inner diameter from 5 to 15 mm greater than the power cable core outer diameter; providing a protective strip (130) over the power cable core (110) in a position substantially matching a welding die (550a), the protective strip (130) having a radially inner and outer surface and being made of copper with a coating, at least on the radially outer surface, made of a metal or a metal alloy having a melting temperature comprised between 90 °C and 250°C; folding the copper foil (300) around the power cable core (110) so as to bring two longitudinal copper foil rims (310) to contact one to the other; welding the two contacted longitudinal copper foil rims (310) with a welding die (550a) thus obtaining a copper sheath (120) in form of a tube with a welding seam (125) and having a diameter; reducing the diameter of the copper sheath (120) to put it into direct contact with the power cable core (110) and the protective strip (130); heating the protective strip (130) and the copper sheath (120) at a temperature higher than the melting temperature of the coating of the strip (130) so that the coating fuses in the welding seam (125); extruding a polymeric sheath (140) around the copper sheath (120).