Encapsulated Field Grading Members for Cable Joint Stress Control
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Solution Overview
Problem
Existing field grading devices in power distribution systems fail to effectively regulate electric fields at cable joints and terminations, leading to potential electrical breakdown of insulators due to high stress, particularly in high voltage applications.
Innovation Solution
A composite field grading member with a conductive network encapsulated within an insulating body, featuring varying density and conductivity, is integrated into cable joints and terminations to uniformly distribute and reduce peak electric field intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the cable shield is removed at joints and terminations for mechanical connection, then ease of connection is improved, but electric field stress on the insulator increases leading to potential electrical breakdown
Solution Approach 1:
A field grading member is introduced as an intermediary component between the cable conductor and the insulator at joints and terminations where the shield is removed. This field grading member comprises a conductive body encapsulated within an insulating body, where the conductive body regulates the electric field and the insulating body provides mechanical protection and electrical insulation. This intermediary structure enables both mechanical connection ease and insulator reliability by controlling the electric field stress distribution.
2Reliability
If traditional field grading devices are used to limit electric stress, then insulator reliability is improved, but device complexity increases
Solution Approach 1:
The field grading member merges the field grading function and the insulation function into a single integrated component. The conductive body encapsulated within the insulating body combines electric field regulation capability with mechanical protection and electrical insulation in one structure, eliminating the need for separate field grading devices and reducing overall device complexity while maintaining insulator reliability.
3Reliability
If the conductive body has high conductivity to regulate electric field, then electric field distribution is improved, but electrical stress on the insulating body increases
Solution Approach 1:
The field grading member employs local quality by having the conductive body strategically positioned within the insulating body at locations where electric field stress is highest. The conductive body's high conductivity is localized to where it is most needed for field regulation, while the insulating body provides localized protection and stress distribution. This spatial differentiation of properties optimizes both electric field distribution and insulating body strength.
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 solution effectively limits electrical stress on insulators, allowing for smaller or higher voltage-rated cables by uniformly distributing electric fields, reducing the risk of breakdown and enhancing insulation durability.
Implementation Method 1
The conductive body is arranged to regulate an electric field within an underlying insulator from current flowing through a conductor
Implementation Method 2
The conductive body encapsulated within the electrically insulating body has reduced conductivity relative to a conductive body not encapsulated within the electrically insulating body
Implementation Method 3
a conductive body encapsulated within an electrically insulating body
Data Source
Figure 1
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AI summary
A field grading member includes an insulating body (130) extending along a regulation axis and a conductive body (132). The conductive body (132) is encapsulated within the insulating body (130) and defines a conductive network therein to regulate an electric field within an underlying insulator from current flowing through a conductor along the regulation axis. Cables and methods of regulating electric field within cables are also described.