Thermoplastic Insulating Layer with Boron Nitride for High-Voltage Cables
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Solution Overview
Problem
Existing electric cables with thermoplastic polypropylene insulating layers face challenges in thermal conductivity, leading to limited current ratings and potential electric leaks due to low thermal conductivity, especially in high-voltage applications, and the addition of boron nitride to enhance conductivity impairs dielectric resistance and increases viscosity, making extrusion difficult.
Innovation Solution
Incorporating up to 20 wt% boron nitride with a particle size distribution of D50 equal to or lower than 15 µm into the thermoplastic polymeric material for the insulating layer, which improves thermal conductivity without compromising dielectric features, allowing for stable electrical resistivity and enhanced dielectric breakdown strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If boron nitride is added to enhance thermal conductivity, then thermal conductivity is improved, but dielectric resistance decreases
Solution Approach 1:
The patent changes the particle size parameter of boron nitride to D50 ≤ 15 µm and controls the content to 5-20 wt%, which optimizes the balance between thermal conductivity enhancement and dielectric resistance maintenance. This parameter optimization allows the insulating layer to achieve improved heat dissipation while preserving adequate electrical insulation properties for high-voltage cable operation.
Solution Approach 2:
The patent creates a composite material system combining thermoplastic polymeric material with boron nitride filler particles. This composite structure leverages the high thermal conductivity of boron nitride while the polymeric matrix provides the dielectric insulation, achieving a synergistic effect that resolves the contradiction between thermal management and electrical insulation requirements.
2Temperature
If boron nitride is added to enhance thermal conductivity, then thermal conductivity is improved, but viscosity increases making extrusion difficult
Solution Approach 1:
The patent optimizes the boron nitride particle size parameter (D50 ≤ 15 µm) and content parameter (5-20 wt%) to achieve a balance between thermal conductivity enhancement and extrusion processability. The controlled particle size distribution prevents excessive viscosity increase while maintaining adequate filler content for thermal performance, enabling successful extrusion manufacturing.
3Ease of manufacture
If thermoplastic polypropylene is used for insulating layer, then ease of manufacture is improved, but thermal conductivity is low limiting current rating
Solution Approach 1:
The patent transforms pure thermoplastic polypropylene into a composite material by incorporating boron nitride filler particles. This composite approach maintains the ease of manufacture and processing advantages of thermoplastic materials while introducing high thermal conductivity through the boron nitride network, thereby resolving the contradiction between manufacturability and thermal performance.
Solution Approach 2:
The patent modifies the thermal conductivity parameter of the polypropylene insulating layer by adding boron nitride filler, changing it from low (pure polymer) to enhanced (composite material). This parameter transformation allows the material to meet thermal management requirements for higher current ratings while preserving the processing advantages of thermoplastic extrusion.
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
This solution enables the cable to operate at high voltages like 600 kV without electric leaks or thermal instability, maintaining suitable dielectric properties and workability during extrusion processes.
Implementation Method 1
boron nitride (chemical formula BN) has an unusual combination of properties in that it is useful as an electrical insulator, and yet it is an excellent conductor of heat
Implementation Method 2
the dielectric constant of BN (ε = 4.0÷4.4 at 1 MHz) is the double of those of the thermoplastic polymers employed as insulation materials
Implementation Method 3
resistive currents may pass through the insulating layer and generate heat that is poorly dissipated by the polypropylene insulating material because of the low thermal conductivity thereof
Data Source
Figure 1
AI summary
An electric cable for high-voltage applications is disclosed which comprises a core surrounded by an electrically insulating layer made of a composition based on a thermoplastic polymeric material charged with boron nitride powder in an amount up to 20 wt% with respect to the weight of the insulating composition, the boron nitride powder having a particle size distribution D50 up to 15 μm. Such a cable has improved thermal conductivity property as well as good dielectric resistance and workability in particular through extrusion processes.