Electrical Bushing Barrier Layer for Foil-Edge Field Enhancement
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Solution Overview
Problem
High voltage bushings face dielectric failure due to weak electrical and mechanical interfaces between conductive foil edges and insulating materials, leading to disruptive discharges, which existing technologies do not adequately address.
Innovation Solution
A barrier layer with a dielectric strength greater than 150 kV/mm, made of materials like polyimide (Kapton, Apical, Upilex), is applied to the edge regions of conductive foils to suppress discharge initiation, maintaining the bushing's physical properties and reducing field enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If thin conductive layers are employed in high voltage bushing structure, then field distribution is improved, but field enhancement at edges occurs
Solution Approach 1:
The patent applies a barrier layer specifically at the edge regions of conductive foils where field enhancement occurs, rather than uniformly across the entire structure. This localized treatment addresses the specific problem area while maintaining the overall field distribution benefits of the thin conductive layers.
Solution Approach 2:
The barrier layer acts as an intermediary element between the conductive foil edge and the surrounding dielectric material. It mediates the electric field distribution at the critical edge region, preventing the harmful field enhancement while allowing the conductive layer to maintain its field-grading function in the bulk region.
2Object-affected harmful factors
If field grading material is applied at foil edges, then electric field is graded, but interface weakness between foil and insulating material persists
Solution Approach 1:
The barrier layer is constructed from composite materials with specific dielectric properties that provide both electrical field grading capability and mechanical adhesion to the conductive foil. This composite structure addresses both the electrical stress concentration and the mechanical interface weakness simultaneously.
Solution Approach 2:
The barrier layer is applied in advance at the foil edges to prevent discharge initiation before it can occur. It acts as a preventive measure that cushions against the harmful effects of field enhancement and protects the weak interface from electrical breakdown.
3Reliability
If double layer foils with insulating layer are used, then partial corona discharges are improved, but device complexity increases
Solution Approach 1:
Instead of using complex double layer foils throughout the entire bushing structure, the patent segments the protective function by applying a separate barrier layer only at the critical edge regions. This segmentation approach provides the necessary protection against corona discharges while avoiding the complexity of modifying the entire foil structure.
Solution Approach 2:
The patent applies partial action by protecting only the critical edge regions where discharge initiation is most likely, rather than applying complex double layer construction to the entire bushing. This partial protection approach achieves sufficient reliability while minimizing structural complexity.
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 barrier layer effectively prevents discharge inception, enhances dielectric strength, and reduces material costs and weight, while improving thermal performance and reliability by homogenizing the electric field and excluding triple points of high dielectric permittivity.
Implementation Method 1
the barrier layer has a dielectric strength greater than the dielectric strength of the dielectric bushing main body and greater than 150 kV/mm
Implementation Method 2
the employment of thin conductive layers in a high voltage bushing structure leads to a significant field enhancement near the edges of the layers
Data Source
AI summary
Electrical bushing for medium and high voltage comprising a dielectric bushing main body a conductor extending through the bushing main body and being electrically insulated by the bushing main body, at least a conductive foil concentrically arranged around the conductor along at least a part of its length, and a barrier layer at least partially covering an edge region of said conductive foil, wherein the barrier layer has a dielectric strength greater than the dielectric strength of the dielectric bushing main body and greater than 150 kV/mm.