Cable Insulation Composition Balancing Additive Retention and Dissipation
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Solution Overview
Problem
Crosslinked polyethylene insulation for medium voltage, high voltage, and extra-high voltage cables faces challenges with additive solubility issues, leading to additive sweat-out and exudation, which cause manufacturing difficulties and increased dissipation factor due to the presence of polar comonomers.
Innovation Solution
A composition comprising 97.5 wt% ethylene-based copolymer with 0.1 wt% vinyl acetate comonomer, 0.050 wt% to 0.150 wt% antioxidant, 0.5 wt% to 1.75 wt% organic peroxide, and optional co-agent or tree retardant, with a total comonomer content of 0.1 wt% to 0.2 wt%, achieving a dissipation factor of 0% to 0.100% at 120°C and 23 kV/mm electrical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polar comonomers are added to increase additive solubility, then additive acceptance is improved, but dissipation factor increases
Solution Approach 1:
The patent changes the chemical parameters of the comonomer from traditional polar comonomers (like acrylic acid or vinyl acetate with high polarity) to a specific polar comonomer with optimized polarity characteristics. This parameter change allows achieving adequate additive solubility while minimizing the increase in dissipation factor, thus resolving the contradiction between additive acceptance and energy loss.
Solution Approach 2:
The patent uses a composite approach by combining the polyethylene base resin with a specifically selected polar comonomer in controlled amounts, creating a composite material system where the comonomer provides necessary additive solubility without excessively increasing polarity-related energy losses. This composite material strategy balances both requirements.
2Reliability
If polar comonomers are added to improve additive solubility, then additives are retained without sweat-out, but manufacturing challenges increase
Solution Approach 1:
By optimizing the polarity parameter of the comonomer and its concentration in the resin, the patent achieves a balance where additives are sufficiently retained without causing excessive sweat-out, while also maintaining manageable manufacturing characteristics. The specific comonomer selection provides adequate polarity for retention without the negative manufacturing effects of high polarity.
3Reliability
If polar comonomers are used to increase additive solubility, then additive acceptance improves, but electrical losses increase
Solution Approach 1:
The patent applies parameter changes by selecting a polar comonomer with optimized polarity characteristics that provide sufficient additive solubility while minimizing dielectric losses. The comonomer's chemical structure is chosen to balance polarity (for solubility) against electrical loss characteristics, directly addressing the contradiction between additive solubility and electrical efficiency.
Data Source
AI summary
A composition comprises a) at least one ethylene-based copolymer comprising units derived from ethylene and from greater than 0 wt% to less than or equal to 3.5 wt%, based on the total weight of the ethylene-based copolymer, of units derived from at least one polar comonomer; b) at least one antioxidant; c) an organic peroxide; d) optionally, at least one co-agent; and e) optionally, at least one water tree retardant or electrical tree retardant. The composition comprises from 0 wt% to less than 1 wt%, based on the total weight of the composition, of olefin-based polymers other than the ethylene-based copolymer. The composition has a dissipation factor of from 0% to less than or equal to 0.1% at a temperature of 120°C and an electrical stress of 6 kV/mm. The composition is suitable for use as an insulation layer in cables.