Polyolefin Cable Insulation for DC Power Stability
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Solution Overview
Problem
High voltage DC power cables face challenges with space charge buildup and electrical conductivity, leading to potential dielectric failure and thermal runaway, which existing polymer compositions fail to adequately address, especially due to the influence of compressor lubricants in high pressure polymerization processes.
Innovation Solution
A polymer composition for DC power cables is developed using a high pressure process with a compressor lubricant comprising mineral oil, which reduces electrical conductivity and minimizes space charge buildup, thereby enhancing the cable's electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymer compositions are used in DC power cables, then the cable can be manufactured with standard materials, but space charge buildup occurs leading to dielectric failure and thermal runaway
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer by incorporating specific additives (0.1-5.0 wt% of electron trap compounds such as metal oxides or organic compounds) into the polyolefin matrix. This parameter modification alters the electrical properties of the insulation material, enabling it to trap space charges and prevent their harmful accumulation, thereby resolving the contradiction between reliability and space charge effects.
2Reliability
If polymer composition is optimized for low electrical conductivity, then thermal runaway is prevented, but manufacturing complexity increases due to specific process requirements
Solution Approach 1:
The patent incorporates the electron trap compounds and other additives into the polymer composition during the initial polymerization or compounding stage, before cable manufacturing. This preliminary action ensures that the thermal stability properties are built into the material itself, eliminating the need for complex post-processing steps or specialized manufacturing equipment, thus maintaining ease of manufacture while achieving thermal stability.
3Ease of manufacture
If compressor lubricant traces are present from high pressure polymerization, then the polymerization process is simplified, but electrical properties deteriorate due to increased conductivity
Solution Approach 1:
The patent acknowledges that traces of compressor lubricant from high pressure polymerization are difficult to eliminate completely. Instead of trying to remove them, the invention converts this potential harm into a benefit by formulating a polymer composition with specific electron trap compounds that can effectively manage the lubricant residues. The additive system is designed to work in conjunction with the lubricant traces, trapping the charges they generate and preventing conductivity issues, thus maintaining process simplicity while ensuring electrical reliability.
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 significantly reduced electrical conductivity and improved space charge properties, making it suitable for high voltage DC power cables, reducing the risk of dielectric failure and thermal runaway.
Implementation Method 1
a hydrophobic polyether polyol of PAG type wherein at least 50% of its molecules comprise no more than a single hydroxyl functionality... reduce dielectrical losses
Implementation Method 2
the electric field in a DC cable is much more complex and depends on the conduction, trapping and build-up of electric charges, so called space charges, inside the insulation
Data Source
AI summary
The invention relates to a polymer composition with improved DC electrical properties, to a method for producing the polymer composition and to a cable surrounded by at least one layer comprising the polymer composition.