Armoured Power Cable with Sectioned Steel Wires for Hysteresis Loss
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Solution Overview
Problem
Existing high voltage AC power transmission cables, particularly submarine cables, face challenges due to magnetic hysteresis losses in ferromagnetic materials used for armouring, which can reduce current carrying capacity and increase heat generation, especially in environments with poor heat dissipation.
Innovation Solution
The cable design incorporates a first section with carbon steel armouring wires coated for corrosion resistance, a second section with austenitic steel wires that are non-magnetic and thus generate minimal heat, and a transition section at least 10 meters long where the carbon steel wires are individually welded to austenitic steel wires, allowing for a gradual change in heat generation along the cable length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ferromagnetic materials (carbon steel) are used for cable armouring, then mechanical strength and corrosion resistance are improved, but magnetic hysteresis losses increase causing excessive heat generation
Solution Approach 1:
The cable is divided into multiple sections along its length, with each section using different armouring materials appropriate for its specific operational environment. This allows optimization of each section independently - using ferromagnetic materials where mechanical strength is critical and non-ferromagnetic materials where heat generation must be minimized.
Solution Approach 2:
Different sections of the cable are assigned different material properties based on local requirements. The armouring material is selected locally - carbon steel in sections requiring high strength, austenitic steel in sections where magnetic losses are problematic - rather than using a uniform material throughout the entire cable length.
2Strength
If ferromagnetic materials are used for cable armouring, then mechanical protection is improved, but current carrying capacity is reduced due to heat generation
Solution Approach 1:
The cable route is segmented into sections with different thermal and mechanical requirements. By placing non-ferromagnetic armouring in sections with poor heat dissipation, the cable can maintain higher current loads without excessive temperature rise, thereby improving overall productivity.
Solution Approach 2:
The armouring material properties are optimized locally to match environmental conditions. In sections with limited heat dissipation capability, non-ferromagnetic materials are used to minimize heat generation and maintain current carrying capacity, while in sections with good cooling, ferromagnetic materials provide enhanced mechanical protection.
3Ease of manufacture
If uniform armouring material is used throughout the cable, then manufacturing simplicity is maintained, but adaptability to different environmental conditions is reduced
Solution Approach 1:
The cable is manufactured as distinct sections that can be produced using standardized processes for each material type, then assembled into a complete cable system. This segmentation allows each section to be optimized for its specific environment while maintaining manufacturing efficiency through modular production.
Solution Approach 2:
The armouring material is selected and applied locally based on the specific environmental conditions of each cable section. This allows the cable to adapt to varying environmental requirements along its route - such as different water depths, temperatures, and thermal dissipation capabilities - while still being manufactured using established processes.
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
This design effectively reduces heat generation in the cable by minimizing magnetic hysteresis losses, particularly in the second section with austenitic steel wires, thereby enhancing the current carrying capacity and operational efficiency of the cable, especially in challenging thermal environments.
Implementation Method 1
In an AC power cable, the magnetic field generated by the current flowing in the conductor/s induces losses in ferromagnetic materials, such as low to medium carbon steel used as armouring wires. The magnetic domains of the ferromagnetic material rotate with the magnetic field in alternate current cables. This rotation of magnetic domains in the material causes friction and heat. The heat produced by this friction is called magnetic hysteresis loss.
Implementation Method 2
The second metallic material has ferromagnetic properties substantially lower than those of the first metallic material. At least part of the plurality of parallel spiralling armouring wires in the second section comprise austenitic steel wires.
Data Source
Figure 1~4
AI summary
An electric power transmission cable comprises electric power conductors and a plurality of parallel spiralled armouring wires.The electric power transmission cable comprises along its length a first section (I), a second section (III) and a transition section (II). The transition section (II) is provided between the first section (I) and the second section (III). The plurality of parallel spiralled armouring wires in the first section (I) comprises or consists out of first armouring wires (121). The first armouring wires (121) are carbon steel wires comprising a metallic corrosion resistant coating. At least part of the plurality of parallel spiralling armouring wires in the second section (III) comprise austenitic steel wires (123). In the transition section (II), ends of first armouring wires (121) are individually welded to ends of austenitic steel wires (123) of the second section (III). The transition section (II) starts at the first weld (137) between a first armouring wire (121) and an austenitic steel wire (123). The transition section (II) ends at the last weld (130) between a first armouring wire (121) and an austenitic steel wire (123). The transition section (II) is at least 10 meter long.