Crosslinked Cable Insulation Reducing Methane By-products
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Solution Overview
Problem
Medium and high voltage energy cables face issues with the accumulation of methane by-products during crosslinking, which can lead to explosiveness and electrical breakdown, and existing solutions do not adequately limit these by-products while maintaining satisfactory thermomechanical properties.
Innovation Solution
The use of a crosslinkable composition comprising a polyolefin and an organic peroxide, with a co-crosslinking agent having multiple unsaturations, such as vinyl functions, to reduce the amount of organic peroxide used, thereby minimizing methane production and maintaining optimal thermomechanical properties like hot creep.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If organic peroxide is used as crosslinking agent, then crosslinking speed and thermomechanical properties are improved, but methane by-products are generated causing explosiveness and electrical breakdown risks
Solution Approach 1:
The patent changes the chemical composition parameters by introducing a co-crosslinking agent with multiple unsaturations (at least two vinyl functions) to modify the crosslinking reaction mechanism. This allows reduction of organic peroxide content while maintaining crosslinking effectiveness, thereby reducing methane by-product generation without sacrificing crosslinking speed or thermomechanical properties
Solution Approach 2:
The patent uses a composite crosslinking system combining organic peroxide with a co-crosslinking agent containing multiple vinyl functions. This composite approach enables the peroxide to initiate crosslinking while the co-crosslinking agent provides additional crosslinking sites, reducing reliance on peroxide decomposition and thus reducing harmful methane by-products while maintaining crosslinking performance
2Object-generated harmful factors
If quantity of organic peroxide is reduced to limit methane by-products, then methane accumulation is decreased, but thermomechanical properties and crosslinking effectiveness deteriorate
Solution Approach 1:
The patent modifies the crosslinking composition by introducing a co-crosslinking agent with at least two unsaturations (vinyl functions). This chemical parameter change enables the system to achieve adequate crosslinking density with reduced peroxide content, maintaining thermomechanical properties while limiting methane by-product generation
Solution Approach 2:
The co-crosslinking agent acts as an intermediary substance that facilitates crosslinking without relying solely on peroxide decomposition. It provides alternative crosslinking pathways through its multiple vinyl functions, enabling reduced peroxide usage while maintaining crosslinking effectiveness and thermomechanical performance
3Object-generated harmful factors
If thermal treatment is applied to accelerate methane diffusion, then methane evacuation is improved, but cable length and manufacturing cost increase
Solution Approach 1:
The patent applies preliminary action by incorporating the co-crosslinking agent into the composition before crosslinking. This preventive measure reduces methane generation at the source during crosslinking, eliminating the need for subsequent thermal treatment to accelerate methane evacuation, thereby saving time and reducing manufacturing costs
Solution Approach 2:
The patent converts the potentially harmful methane generation issue into a benefit by using the co-crosslinking agent's multiple vinyl functions to provide alternative crosslinking pathways. This reduces reliance on peroxide decomposition, transforming the harmful methane production into a controlled process that generates fewer by-products while maintaining crosslinking effectiveness
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 approach significantly reduces the quantity of crosslinking by-products like methane, while ensuring excellent thermomechanical properties, including a maximum hot elongation under stress of up to 100%, and enhances the resistance to electrical breakdown and water trees in high voltage cables.
Implementation Method 1
During the crosslinking of said compositions, this type of peroxide decomposes and forms crosslinking by-products such as in particular methane
Implementation Method 2
The at least two unsaturations are more particularly reactive functions of the carbon-carbon double bond type, which are capable on the one hand of being grafted to the polyolefin, and on the other hand of participating in the crosslinking of the polyolefin (i.e. the formation of the three-dimensional network of the crosslinked polyolefin)
Implementation Method 3
The thermomechanical properties for the crosslinked layer according to the invention can advantageously result in a maximum hot elongation under stress according to standard NF EN 60811-2-1 of at most 100%
Data Source
Figure 1
AI summary
The present invention relates to an electrical cable (1) comprising an electrical conductor (2), a first semiconducting layer (3) surrounding the electrical conductor (2), a second electrically insulating layer (4) surrounding the first layer (3), and a third semiconducting layer (5) surrounding the second layer (4), at least one of these three layers (3, 4, 5) being a crosslinked layer obtained from a crosslinkable composition comprising at least one polyolefin and an organic peroxide as a crosslinking agent, characterized in that the composition further comprises a crosslinking co-agent comprising at least two unsaturations, one of these two unsaturations being a vinyl function.