Submarine Cable Insulation Extrusion Without a Metallic Water Barrier
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Solution Overview
Problem
Submarine power cables with dry designs face issues of water-treeing due to impurities in the insulation layer under high electric fields, leading to potential insulation breakdown, especially in high voltage applications, and existing ultraclean polymeric materials do not fully prevent this issue.
Innovation Solution
Manufacture wet or semi-wet submarine power cables using ultraclean polymer materials in a controlled environment (clean room class 8) and extrude an insulation system without a metallic water barrier, ensuring minimal contamination and reducing water-treeing risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a radial metallic water barrier is used to hermetically seal the insulation system, then protection against water ingress is improved, but device complexity and material usage increase
Solution Approach 1:
The patent removes the metallic water barrier component entirely from the cable design. Instead of using lead or aluminum sheathing, the insulation system is designed to inherently resist water treeing through controlled purity of the insulation layer and optimized crosslinking, eliminating the need for the metallic barrier and simplifying the overall device structure.
Solution Approach 2:
The patent changes the purity parameter of the insulation layer to extremely low levels of impurities (less than 10 particles per square meter with diameter greater than 1 micrometer). This parameter change allows the insulation to withstand water exposure without treeing, replacing the need for metallic protection barriers.
2Manufacturing precision
If ultraclean polymeric insulation materials are used, then purity of insulation layer is improved, but water-treeing resistance at high voltage levels is not sufficiently improved
Solution Approach 1:
The patent implements preliminary actions during manufacturing by establishing controlled clean room environments (ISO class 7 or 8) and using filtered air supplies during the extrusion process. This preliminary control of the manufacturing environment ensures the insulation layer achieves the required purity levels before the cable is put into service, preventing future water treeing issues.
Solution Approach 2:
The patent uses crosslinked polyethylene (XLPE) as the insulation material, which provides superior electrical and mechanical properties compared to non-crosslinked materials. The crosslinking process creates a three-dimensional network structure that enhances resistance to water treeing and degradation, working in combination with the controlled purity to achieve the required reliability.
3Ease of manufacture
If the insulation layer contains impurities, then ease of manufacture is improved, but susceptibility to water-treeing increases
Solution Approach 1:
The patent creates an inert clean room environment during manufacturing with controlled particle concentrations and filtered air supplies. This inert atmosphere prevents contamination of the insulation layer during extrusion, allowing the production of extremely pure insulation without requiring complex post-manufacturing purification processes, thus maintaining ease of manufacture while achieving low impurity levels.
Data Source
AI summary
A method of manufacturing a wet or semi-wet design high voltage or extra high voltage submarine power cable, the method including: a) supplying polymer materials to an extruder from a material handling room, the material handling room fulfilling clean room class 8 or cleaner according to ISO-14644-1: 2015, and b) extruding an insulation system, including an insulation layer, around a conductor in the extruder using the polymer material, the extruder fulfilling the requirements of clean room class 8 or cleaner according to ISO-14644-1: 2015.