Thermoplastic Cable Joint Dimensional Stability
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Solution Overview
Problem
The challenge in manufacturing medium/high voltage electric cable joints with thermoplastic insulation systems is the risk of thermal deformation and loss of dimensional stability due to heating, which is not addressed by traditional curing processes, and pressure does not effectively suppress void formation in thermoplastic materials.
Innovation Solution
A method involving a joint structure with specific dynamic storage moduli for thermoplastic semiconducting and insulating layers, where the inner layer has a higher dynamic storage modulus than the insulating layer, measured at a temperature of at least 130°C, to ensure dimensional stability and electrical reliability, without relying on curing for stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermoplastic materials are heated to melt and homogenize the insulating layer, then the layer becomes continuous and homogeneous, but the already applied inner semiconducting layer undergoes thermal deformation and loses dimensional stability
Solution Approach 1:
The patent applies a temperature gradient during the heating process, with the temperature being highest at the insulating layer and progressively lower towards the inner semiconducting layer. This parameter change in temperature distribution allows the insulating layer to reach melting point for homogenization while the inner layer remains below its deformation temperature, thus resolving the contradiction between achieving homogeneity and maintaining dimensional stability.
2Ease of manufacture
If traditional curing processes are used for stabilization, then the process is simplified, but thermal deformation and loss of dimensional stability occur in thermoplastic materials
Solution Approach 1:
The patent changes the temperature parameter distribution throughout the joint structure, creating a gradient where the temperature decreases from the outer insulating layer to the inner semiconducting layer. This allows the outer layers to be heated sufficiently for melting and homogenization while the inner layers remain at temperatures that prevent thermal deformation, achieving dimensional stability without traditional curing processes.
3Manufacturing precision
If pressure is applied during heating to suppress void formation, then voids may be reduced, but thermal deformation is exacerbated in thermoplastic materials
Solution Approach 1:
The patent changes the temperature parameter distribution to create a gradient that allows void suppression through controlled heating without applying excessive pressure. The temperature gradient enables the material to become sufficiently fluid for void elimination while maintaining structural integrity, resolving the contradiction between void formation control and dimensional stability.
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 approach allows for the creation of a dimensionally stable and electrically reliable diameter joint by using thermoplastic materials with tailored dynamic storage moduli, preventing thermal deformation and void formation, thereby maintaining the integrity of the joint's mechanical and electrical properties.
Implementation Method 1
heating to a temperature sufficient to melt the thermoplastic material of the insulating layer
Implementation Method 2
heating to a temperature sufficient to melt the thermoplastic material of the insulating layer and homogenize the molten material
Data Source
AI summary
A method for manufacturing an electric cable joint is described. The method includes: a step of providing two electric cables, each cable containing an electric conductor and a thermoplastic insulation system surrounding the electric conductor and containing an inner and an outer thermoplastic semiconducting layers and a thermoplastic insulating layer; a step of joining the terminal portions of the electric conductors of the first and second electric cables to form an electric conductor joint; a step of surrounding the electric conductor joint with a joint inner layer of a thermoplastic semiconducting material having a dynamic storage modulus E′1; a step of surrounding the joint inner layer with a joint insulating layer of a thermoplastic insulating material having a dynamic storage modulus E′2 smaller than E′1; and a step of surrounding the joint insulating layer with a joint outer layer of a thermoplastic semiconducting material having a dynamic storage modulus E′3.