Non-crosslinked Polyolefin Cable Insulation for Space Charge Dissipation
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Solution Overview
Problem
Medium and high voltage power cables experience degradation due to the accumulation of space charge and water treeing, leading to electrical breakdown, particularly in humid environments and strong electric fields, which threatens the reliability of power transmission networks.
Innovation Solution
An electrical cable with a non-crosslinked polymeric layer made of a graft polymer material, comprising a polyolefin and a grafting compound with an epoxy group, is used to enhance breakdown resistance and dissipate space charges, preventing water tree growth without crosslinking the polymer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crosslinking is used to improve water tree resistance, then breakdown resistance improves, but manufacturing complexity and cost increase
Solution Approach 1:
The invention changes the chemical structure parameter of the polymer by introducing epoxy groups at controlled concentrations (0.1-10 mmol/kg) without crosslinking. This parameter change modifies the polymer's interaction with water and space charges, achieving improved breakdown resistance through compositional modification rather than structural crosslinking.
Solution Approach 2:
The invention uses simple, inexpensive epoxy compounds that can be easily incorporated during extrusion without requiring complex crosslinking equipment or processes. The epoxy groups provide the necessary functionality at low concentrations, making the solution economically advantageous compared to crosslinking technologies.
2Reliability
If crosslinking is used to improve water tree resistance, then manufacturing cost increases, but ease of manufacture decreases
Solution Approach 1:
The invention merges the water tree resistance function directly into the base polyolefin material by incorporating epoxy groups during the extrusion process. This eliminates the need for separate crosslinking treatment steps, combining material preparation and functional enhancement into a single manufacturing operation.
Solution Approach 2:
The epoxy groups inherently provide water tree resistance without requiring external activation or additional processing steps. The functional groups work autonomously within the polymer matrix to prevent water tree initiation and propagation, eliminating the need for separate treatment processes.
3Reliability
If crosslinking is used to improve breakdown resistance, then reliability improves, but recyclability worsens
Solution Approach 1:
The invention achieves improved breakdown resistance through controlled incorporation of epoxy groups (0.1-10 mmol/kg) rather than crosslinking. This parameter change maintains the thermoplastic nature of the polyolefin, allowing the material to retain its recyclability while achieving the desired electrical performance.
Solution Approach 2:
The use of simple epoxy compounds in low concentrations provides the necessary functional improvement without fundamentally altering the polymer's recyclability. The material remains compatible with existing recycling processes for polyolefins, unlike crosslinked materials that form irreversible networks.
4Productivity
If epoxy groups are opened during grafting, then grafting efficiency improves, but water tree retarding capability decreases
Solution Approach 1:
The invention performs preliminary grafting of epoxy groups onto the polyolefin chain without opening the epoxy rings. This preliminary action introduces the functional groups in their intact form, preserving their water tree retarding capability while achieving sufficient grafting to provide the desired electrical performance.
Solution Approach 2:
The invention changes the grafting approach from opening epoxy groups to incorporating them in their intact form. This parameter change in the grafting methodology preserves the beneficial properties of the epoxy groups while achieving the necessary level of incorporation for water tree resistance.
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 non-crosslinked layer significantly improves the electrical breakdown resistance and water tree retardation in high voltage cables, maintaining reliability and ease of manufacturing and recycling, while avoiding costly crosslinking processes.
Implementation Method 1
the said compound intended to be grafted is a grafting compound comprising at least one epoxy group and a single reactive function capable of being grafted onto the polyolefin... the grafting compound is used in the present invention as a water tree retardant... the ability to dissipate the space charges which accumulate in particular in the high voltage cables under direct current
Implementation Method 2
Thanks to the invention, the non-crosslinked layer makes it possible to significantly limit the water trees due to the presence of the grafting compounds grafted along the macromolecular chain of the polyolefin
Data Source
Figure 1
AI summary
The invention relates to an electric cable (1) comprising an elongate electrical conductor (2) surrounded by a non-cross-linked layer of a grafted polymer material that is obtained from a polymer composition comprising: at least one polyolefin and a compound intended to be grafted to the polyolefin. The cable is characterised in that the compound to be grafted is a grafting compound comprising at least one epoxy group and a single reactive function which can be grafted to the polyolefin.