Ethylene-MPEGMA Copolymer Insulation for Water Tree Retardance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Water trees in insulation layers of medium- to extra-high voltage power cables cause electrical trees, leading to cable failure, and existing solutions for inhibiting water trees are not effective in all cases, particularly with high molecular weight polyethylene glycol (PEG) as a water tree retardant (WTR).
Innovation Solution
A crosslinkable composition comprising a reactor copolymer of ethylene and methoxy polyethylene glycol methacrylate (co-E-MPEGMA) is used, which provides water tree retardant properties even in non-mobile forms, and when blended with low density polyethylene (LDPE), exhibits synergistic scorch-resistance at extrusion conditions, improving cable insulation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high molecular weight polyethylene glycol (PEG) is used as a water tree retardant, then water tree inhibition is improved, but mobility to reach stress regions deteriorates
Solution Approach 1:
The patent changes the molecular weight parameter of PEG from high (20,000 g/mol) to low (2,000 g/mol or less), which fundamentally alters both its mobility and water tree inhibition mechanism. The lower molecular weight enables sufficient mobility while maintaining effectiveness through a different protective mechanism.
Solution Approach 2:
The patent employs low molecular weight PEG that can be replenished or replaced more easily compared to high molecular weight PEG. This shorter-lived additive approach allows for periodic restoration of water tree resistance without requiring permanent, immobile high molecular weight structures.
2Reliability
If polar copolymers such as ethylene butyl acrylate (EBA) are incorporated to inhibit water trees, then water tree resistance is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts the essential water tree inhibition function from complex polar copolymer systems and isolates it to a single, simple component: low molecular weight PEG. This simplifies the composition while maintaining the critical protective function against water trees.
Solution Approach 2:
The patent uses a homogeneous system consisting of only PEG as the water tree retardant, eliminating the need for complex copolymer blends. This single-component approach simplifies manufacturing and composition control while achieving effective water tree inhibition.
3Reliability
If PEG is used as water tree retardant, then water tree growth is inhibited, but scorch resistance at extrusion conditions deteriorates
Solution Approach 1:
The patent merges PEG (for water tree retardancy) with LDPE (for structural integrity and scorch resistance) in a blended composition. This combination allows the system to benefit from both components: PEG provides water tree protection while LDPE maintains thermal stability and resistance to premature crosslinking during extrusion.
Solution Approach 2:
The patent creates a composite material system combining PEG and LDPE, where each component contributes its superior properties. The composite structure enables simultaneous achievement of water tree inhibition and scorch resistance, which neither component could provide alone in the required performance levels.
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 co-E-MPEGMA composition effectively inhibits water tree growth and enhances scorch-resistance, leading to improved performance in medium- to extra-high voltage cable insulation, particularly when used in Direct Peroxide Injection processes, with specific benefits seen in blends containing 0.5 wt% methoxy polyethylene glycol methacrylate.
Implementation Method 1
peroxide crosslinked low density polyethylene, LDPE
Implementation Method 2
reactor copolymer of ethylene and methoxy polyethylene glycol methacrylate (co-E-MPEGMA)
Implementation Method 3
the PEG is mobile enough to move to the region of highest stress and fill the tree tips
Implementation Method 4
exhibits synergistic scorch-resistance at extrusion conditions
Data Source
Figure 1~2
AI summary
The copolymerization of ethylene (E) and methoxy polyethylene glycol methacrylate (MPEGMA) produces the copolymer co-E-MPEGMA. These copolymers are distinct from polyethylene, e.g., low density polyethylene (LDPE) grafted with MPEGMA, i.e., g-E-MPEGMA, and are useful in the preparation of insulation sheaths for medium, high and extra-high voltage cables. Such cables exhibit good water tree retardance.