High-Voltage Cable Fitting Axial Expansion Stress Relief
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Solution Overview
Problem
Existing high-voltage cable fittings with the outer cone design approach face challenges in achieving minimal interface pressure while maintaining a compact overall diameter, leading to potentially bulky designs and increased pressure requirements.
Innovation Solution
The design incorporates a rigid core insulator with a conical outer surface and an elastomeric stress relief element, where a rigid member applies additional axial expansion stress to the stress relief element, generating a second radial compression force, ensuring a total pressure greater than 0.1 MPa, thus maintaining interface quality with a smaller diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer cone design approach is used with a rigid core insulator and elastomeric stress relief element, then the cable fitting can provide stress relief and field grading, but the overall diameter becomes large and the interface pressure becomes difficult to maintain
Solution Approach 1:
The invention divides the stress relief element into multiple segments along its length, with different segments having different degrees of elasticity. The first portion (near the cable) has higher elasticity to provide initial stress relief, while the second portion (near the core insulator) has lower elasticity to maintain stable interface pressure. This segmentation allows the fitting to maintain reliable interface pressure without requiring a large overall diameter.
Solution Approach 2:
The stress relief element is designed with non-uniform local properties - the first portion has different elastic characteristics than the second portion. This local quality variation enables different functional zones: the more elastic first portion accommodates cable movement and provides initial stress relief, while the less elastic second portion maintains stable contact pressure at the interface with the core insulator, solving the contradiction between compact size and pressure maintenance.
2Manufacturing precision
If large pressure is exerted by the stress relief element to avoid voids at the interface, then the mating quality improves, but the overall diameter and bulkiness increase
Solution Approach 1:
By segmenting the stress relief element into portions with different elasticities, the invention achieves high interface mating quality through the controlled action of the second portion (with stable, lower elasticity) that maintains consistent contact pressure without requiring excessive overall size. The segmentation allows precise control of pressure distribution.
Solution Approach 2:
The invention changes the elasticity parameter along the length of the stress relief element, creating a gradient or stepwise variation in mechanical properties. This parameter change enables the interface region to have optimized elastic characteristics for high-quality mating, while other regions have different characteristics that prevent excessive bulkiness.
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 achieves reliable long-lasting pressure at the interface, enhancing the mating quality and reducing the overall diameter of the cable fitting, while effectively withstanding high electric fields.
Implementation Method 1
The stress relief element is pressed onto the rigid core insulator such that the stress relief element experiences circumferential expansion, generating in turn radial compression stress
Implementation Method 2
The pressure enhancing portion causes an additional axial expansion stress in a sleeve portion of the stress relief element... The additional axial expansion stress causes a second radial compression force
Data Source
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AI summary
A high-voltage cable fitting (30) with a rigid core insulator (1) that has a first conical outer surface (4) extending concentrically about a longitudinal axis (5). An elastomeric stress relief element (6) has a first conical inner surface (7) is designed for mating the first conical outer surface (4) at an interface (9). A rigid member (11) is provided for pressurizing the elastomeric stress relief element (6) at the interface (9). The stress relief element (6) is pressed onto the rigid core insulator (1). The rigid member (11) has at least one pressure enhancing portion (17) extending circumferential about the longitudinal axis (5) for causing an additional axial expansion stress (23) in a sleeve portion (19) of the stress relief element (6) extending along the first conical outer surface (4) of the core insulator (1) in an assembled state of the cable fitting (30).