Power Cable Joint Insulation Taper for Dielectric Strength
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Solution Overview
Problem
Conventional power cable joints experience breakdowns due to weak dielectric strength at material interfaces, particularly where the electric field crosses the insulation layer and semiconducting layers at angles far from perpendicular, leading to increased dielectric stress.
Innovation Solution
A method of making power cable joints by mechanically processing the insulation system to create tapering insulation layers with controlled inclinations relative to the longitudinal axis, ensuring the electric field crosses the interfaces closer to perpendicular, thereby enhancing dielectric strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the insulation layer is processed with a frustoconical portion (single inclination), then the manufacturing process is simple, but the dielectric strength at the interface is reduced because the electric field crosses the interface at an angle far from perpendicular
Solution Approach 1:
The insulation layer is divided into multiple portions (first portion with first inclination, second portion with second inclination, and third portion with third inclination). Each portion has a different inclination angle, allowing the electric field to cross the interface at angles closer to perpendicular at different locations, thereby improving dielectric strength while maintaining manufacturing feasibility.
Solution Approach 2:
Different portions of the insulation layer are given different local geometries (different inclination angles). The first portion has a first inclination, the second portion has a second inclination, and the third portion has a third inclination. This local variation in geometry optimizes the electric field distribution at each interface location, improving overall dielectric strength.
2Reliability
If the insulation layer is processed to create multiple portions with different inclinations, then the dielectric strength at the interface is improved, but the manufacturing complexity increases
Solution Approach 1:
The insulation layer is segmented into three distinct portions, each with a specific inclination angle. This segmentation allows for optimized electric field distribution while maintaining a systematic manufacturing approach where each portion can be processed in a controlled manner.
Solution Approach 2:
The transition between different inclination portions is made smooth and continuous rather than abrupt. The outer surface of the insulation layer features smooth transitions between the first, second, and third portions, which reduces stress concentration and simplifies the manufacturing process by avoiding sharp edges or discontinuities.
Data Source
Figure 1~2
AI summary
A method of making a joint (3) of a power cable (1), comprising: a) providing two cable sections (1a, 1b) to be jointed, each cable section (1a, 1b) comprising a conductor (5a, 5b) having a conductor end, and an insulation system including an inner semiconducting layer (7) arranged around the conductor (5a, 5b), an insulation layer (9) arranged radially outside the inner semiconducting layer (7), and an outer semiconducting layer (11) arranged radially outside the insulation layer (9), b) mechanically processing the insulation system of each cable section (1a, 1b) by gradually increasing a radius of the insulation layer (9) in an axial direction away from the conductor end of the cable section (1a, 1b), to obtain a tapering insulation layer section that tapers towards the conductor end, wherein the processing is performed such that an outer surface of a radially innermost portion (9.1) of the tapering insulation layer section, interfacing the inner semiconducting layer (7), obtains a first inclination relative to a longitudinal axis of the cable section (1a, 1b), and that an outer surface of an intermediate portion (9.2) of the tapering insulation layer section obtains a second inclination which is larger than the first inclination, wherein the outer surface of the radially innermost portion (9.1) transitions smoothly to the outer surface of the intermediate portion (9.2), and c) making a joint insulation system (13), after the conductors of the two cable sections (1a, 1b) have been electrically connected to each other by means of a conductor joint (5c), the joint insulation system (13) connecting to the inner semiconducting layer (7) of each cable section (1a, 1b), to the tapering insulation layer section of each cable section (1a, 1b), and to the outer semiconducting layer (11) of each cable section (1a, 1b).