Polymer Cable Insulation Crosslinking for Low Conductivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current polymer compositions for power cables, particularly DC power cables, face challenges in achieving low electrical conductivity to prevent heat generation and thermal runaway, while maintaining mechanical properties and requiring extensive degassing steps to remove volatile by-products from crosslinking processes.
Innovation Solution
A polymer composition comprising low pressure polyethylene blended with low density polyethylene (LDPE) is used for the insulation layer of power cables, which exhibits reduced electrical conductivity and is crosslinkable using a free radical generating agent, such as peroxide, to enhance mechanical and thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If peroxide crosslinking is used to improve mechanical and thermal properties, then heat and deformation resistance are improved, but volatile decomposition products are generated that negatively influence electrical properties
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking system by replacing traditional peroxide crosslinking with a two-stage process: first introducing multifunctional epoxy compounds to create crosslinks, then using basic catalysts to promote further crosslinking. This parameter change eliminates the generation of volatile decomposition products while achieving the desired mechanical strength and heat resistance.
Solution Approach 2:
The patent converts the potentially harmful effect of extensive crosslinking (which would generate volatile by-products) into a benefit by using a crosslinking system that achieves thorough crosslinking without volatile decomposition. The epoxy compound-based crosslinking provides the mechanical reinforcement needed while avoiding the electrical property degradation caused by traditional peroxide decomposition products.
2Strength
If traditional peroxide crosslinking is used, then mechanical properties are improved, but extensive degassing steps are required which are time and energy consuming
Solution Approach 1:
The patent changes the chemical nature of the crosslinking reaction from peroxide-based to epoxy compound-based, which fundamentally alters the by-products from volatile gases requiring degassing to non-volatile or minimal by-products. This parameter change in the crosslinking chemistry eliminates the need for extensive degassing steps, significantly reducing production time and energy consumption while maintaining mechanical property improvements.
3Reliability
If insulation material has high electrical conductivity, then electrical field influence is reduced, but heat generation from leakage current increases leading to thermal runaway
Solution Approach 1:
The patent addresses the thermal runaway risk by using epoxy compound crosslinking which creates a more thermally stable insulation structure. The crosslinked network formed by epoxy compounds and basic catalysts has superior thermal properties that reduce the temperature coefficient of electrical conductivity, thereby converting the potential harm of heat generation into a benefit of enhanced thermal stability and reduced thermal runaway risk.
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 polymer composition achieves low electrical conductivity, minimizing heat formation and thermal runaway, while reducing the need for extensive degassing and maintaining robust mechanical properties, making it suitable for high voltage applications.
Implementation Method 1
Free radical generating agent is typically incorporated to the layer material prior to the extrusion of the layer(s) on a conductor. After formation of the layered cable, the cable is then subjected to a crosslinking step to initiate the radical formation and thereby crosslinking reaction.
Implementation Method 2
In crosslinking reaction of a polymer interpolymer crosslinks (bridges) are primarily formed.
Implementation Method 3
The resulting decomposition products of peroxides may include volatile by-products which are often undesired, since e.g. may have a negative influence on the electrical properties of the cable.
Implementation Method 4
Therefore the volatile decomposition products such as methane are conventionally reduced to a minimum or removed after crosslinking and cooling step. Such removal step, generally known as a degassing step, is time and energy consuming causing extra costs.
Implementation Method 5
The second issue is the fact that heat will be generated inside the insulation by the electric leakage current flowing between the inner and outer semiconductive layers.
Data Source
AI summary
The invention relates to a polymer composition with improved DC electrical properties, to the use of the composition for producing a cable layer and to a cable surrounded by at least one layer comprising the polymer composition.