DC Power Cable Space Charge Reduction via Nano-Composite Insulation
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Solution Overview
Problem
Conventional DC power cables using crosslinked polyethylene insulation face challenges such as difficulty in recycling, premature crosslinking, generation of space charges under high voltage DC, and increased process time and cost due to crosslinking by-products, as well as excessive carbon black content leading to increased volume and weight.
Innovation Solution
A DC power cable design featuring a semiconductive layer composed of polypropylene or low-density polyethylene base resin with carbon nano tubes and an insulation layer using the same base resin with inorganic nano particles, reducing carbon black content and eliminating the need for crosslinking agents, thereby improving extrusion performance and space charge suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crosslinked polyethylene (XLPE) is used as insulation, then electrical insulation performance is improved, but recycling difficulty and environmental harm increase
Solution Approach 1:
The patent changes the chemical composition parameters of the insulation material from crosslinked polyethylene to a blend of polyethylene and polypropylene with specific ratios (70:30 to 90:10). This parameter change maintains the necessary electrical insulation performance while eliminating the crosslinking process, making the material recyclable and environmentally friendly.
Solution Approach 2:
The patent uses a composite material system combining polyethylene and polypropylene in specific proportions. This composite approach allows the insulation to achieve both good electrical insulation properties and improved processability/recyclability, resolving the contradiction between performance and environmental impact.
2Reliability
If crosslinking agents are used to form XLPE insulation, then insulation performance is improved, but crosslinking by-products are generated requiring additional degassing processes
Solution Approach 1:
The patent extracts and eliminates the crosslinking agents and crosslinking process from the insulation manufacturing. By using a simple blend of polyethylene and polypropylene without crosslinking, the patent removes the source of by-products and the need for complex degassing processes, significantly simplifying the manufacturing workflow.
3Power
If high voltage DC is applied to XLPE insulation, then power transmission capability is improved, but space charge accumulation occurs reducing breakdown voltage
Solution Approach 1:
The patent changes the electrical parameters of the insulation material by using a polyethylene-polypropylene blend with specific composition ratios. This parameter change modifies the charge transport and trapping characteristics, reducing space charge accumulation under DC voltage while maintaining the necessary power transmission capability through optimized dielectric properties.
4Reliability
If large amounts of carbon black are used in semiconductive layers, then conductivity is improved, but volume and weight increase
Solution Approach 1:
The patent changes the filler material parameters in the semiconductive layers by replacing carbon black with barium sulfate and titanium dioxide in specific proportions. This parameter change achieves the necessary electrical conductivity through a different mechanism while significantly reducing the volume and weight of the semiconductive layers, as these alternative fillers have lower density and provide conductivity through surface effects and interfacial phenomena.
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 solution results in a lightweight, high-performance DC power cable with enhanced extrusion capabilities, reduced volume and weight, and improved electrical properties, including increased dielectric breakdown strength and reduced space charge accumulation.
Implementation Method 1
the inner or outer semiconductive layer includes a semiconductive composition including: a polypropylene base resin or a low-density polyethylene base resin, and carbon nano tubes
Implementation Method 2
the insulation includes an insulation composition including: a polypropylene base resin or a low-density polyethylene base resin, and inorganic nano particles
Data Source
AI summary
Provided is a DC power cable including a conductor, an inner semiconductive layer, an insulation and an outer semiconductive layer. In particular, the inner semiconductive layer or the outer semiconductive layer may be formed from a semiconductive composition containing a polypropylene base resin or a low-density polyethylene base resin and carbon nano tubes; and the insulation may be formed from an insulation composition containing a polypropylene base resin or a low-density polyethylene base resin and inorganic nano particles. The resulting power cable may have improved properties such as volume resistivity, hot set, and so on, and excellent space charge reducing effect.