Medium Voltage Cable Insulation Composition
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Solution Overview
Problem
Medium voltage cable insulation materials face challenges in achieving a balance between long-term heat aging resistance and water-tree resistance, as existing solutions often exhibit antagonism between sulfur-containing and amine-based molecules, and polyethylene glycol can be a pro-degradant, requiring additional stabilization.
Innovation Solution
A composition comprising an ethylene-based polymer, polyalkylene glycol, tertiary hindered amine stabilizer, sulfur-containing hindered phenol antioxidant, and peroxide, with an optional coagent, which together form a cure package for crosslinked polyethylene insulation, providing a commercially desirable balance of heat aging retardancy and water- and electrical-tree resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene glycol (PEG) is used to improve water-tree resistance, then water-tree retardancy is enhanced, but thermo-oxidative stability deteriorates due to PEG being a pro-degradant
Solution Approach 1:
The patent applies preliminary anti-action by incorporating stabilizers (hindered phenol antioxidants and hindered amine stabilizers) that counteract the pro-degradant effects of PEG before thermo-oxidative damage can occur. These stabilizers preemptively neutralize free radicals and prevent oxidation chains that would otherwise be initiated by PEG during long-term heat aging, thus resolving the contradiction between water-tree resistance and thermo-oxidative stability.
Solution Approach 2:
The patent uses stabilizers as intermediary substances that mediate between PEG and the polyethylene matrix. The hindered phenol and hindered amine stabilizers act as intermediaries that capture free radicals generated by PEG, preventing them from attacking the polymer chains. This intermediary action allows PEG to provide water-tree resistance while the stabilizers protect against thermo-oxidative degradation.
2Duration of action of stationary object
If sulfur-containing hindered phenol stabilizer is used to improve long-term heat aging resistance, then heat aging retardancy is enhanced, but water-tree and electrical-tree resistance deteriorates due to antagonism with amine-based molecules
Solution Approach 1:
The patent applies parameter changes by carefully controlling the ratio and concentration of sulfur-containing hindered phenol stabilizer to hindered amine stabilizer. By optimizing these parameters, the patent achieves a composition where both stabilizers work synergistically rather than antagonistically. The specific parameter ranges (0.1-5 wt% for hindered phenol, 0.05-2 wt% for hindered amine) are determined to minimize negative interactions while maximizing both heat aging and tree resistance.
Solution Approach 2:
The patent creates a composite stabilization system combining sulfur-containing hindered phenol stabilizer and hindered amine stabilizer in specific proportions. This composite approach allows the benefits of both stabilizer types to be realized simultaneously - the hindered phenol provides heat aging resistance while the hindered amine contributes to tree resistance, with their combined effect being greater than the sum of individual effects when properly formulated.
3Duration of action of stationary object
If peroxide-initiated crosslinking is used to improve long-term heat aging resistance, then heat aging retardancy is enhanced, but water-tree resistance may deteriorate due to increased crosslink density
Solution Approach 1:
The patent applies parameter changes by controlling the crosslinking degree through careful selection of peroxide concentration (0.1-3 wt%) and curing conditions. By optimizing these parameters, the patent achieves a balance where sufficient crosslinking provides heat aging resistance while avoiding excessive crosslink density that would harm water-tree resistance. The crosslinking level is tuned to maintain appropriate free volume and chain mobility for water tree suppression.
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 composition effectively enhances the long-term heat aging resistance and water-tree resistance of medium voltage cable insulation, maintaining mechanical properties and breakdown strength after aging, while minimizing interactions that hinder performance.
Implementation Method 1
thermo-oxidative damage during long term aging is another mode of failure of medium voltage cables. Retardancy of this unwanted phenomenon is typically achieved through a combination of peroxide-initiated crosslinking the ethylene-based polymer
Implementation Method 2
Retardancy of this unwanted phenomenon is typically achieved through a combination of peroxide-initiated crosslinking the ethylene-based polymer and the use of a sulphur containing hindered phenol stabilizer. Hindered amine stabilizers are known for their use as thermo-oxidative stabilizers
Data Source
AI summary
Compositions comprising: A. Ethylene-based polymer, e.g., LDPE; B. Polyalkylene glycol, e.g., PEG; C. Tertiary hindered amine stabilizer; D. Sulphur-containing hindered phenol antioxidant; E. Peroxide; and F. Optional coagent are useful in the preparation of TRXLPE insulation for medium voltage cable that exhibits a commercially desirable balance of long term heat aging retardancy and water-tree resistance.