Field Grading Composite for Nonlinear Electric Stress Control
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Solution Overview
Problem
Existing field grading devices in electrical power distribution systems, such as stress-cones and cylindrical grading elements, while effective, have limitations in efficiently managing electric fields and reducing electrical stress on insulators, particularly in high voltage applications.
Innovation Solution
A field grading member comprising a polymeric matrix with particulate filler bodies that include a semiconductor core, an oxide mixed layer, and a conducting oxide layer, which provides an electrical percolation path triggered by the strength of the electric field, thereby effectively regulating the electric field and reducing stress on insulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional field grading devices (stress-cones, cylindrical grading elements) are used, then electric field distribution is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the electrical parameter characteristics by using semiconductor particles with field-dependent conductivity. The conductivity of the semiconductor particles varies with the electric field strength, automatically adjusting the field distribution without complex geometric structures. This resolves the contradiction by achieving reliable field grading through material parameter changes rather than complex device design.
Solution Approach 2:
The patent employs composite materials consisting of semiconductor particles embedded in an insulating matrix. This composite structure combines the insulating properties of the matrix with the field-dependent conductive properties of the semiconductor particles, creating a material that inherently provides field grading functionality without requiring complex device architectures.
2Reliability
If higher filler fraction is used to improve field grading performance, then electric stress limitation is improved, but manufacturing complexity and material cost increase
Solution Approach 1:
The patent utilizes the inherent parameter change of semiconductor materials where conductivity increases with electric field strength. This non-linear response allows effective field grading at lower filler fractions because the semiconductor particles become more conductive in high-field regions, automatically directing current through pathways that provide stress limitation without requiring high filler concentrations.
Solution Approach 2:
The semiconductor particles provide self-service field grading by automatically adjusting their conductivity based on the local electric field strength. In high-stress regions, the particles become more conductive and provide current pathways that limit stress concentration, while in low-stress regions they remain less conductive. This self-adjusting behavior achieves effective field grading without requiring complex manufacturing processes or high filler fractions.
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 proposed field grading member achieves high non-linearity in resistivity as a function of electric field magnitude, effectively limiting electric stress even at high voltages with a relatively low filler fraction, thus enhancing the reliability and safety of electrical power distribution systems.
Implementation Method 1
a conducting oxide layer deposited on the oxide mixed layer to provide an electrical percolation path through the polymeric matrix triggered by strength of an electric field extending through the field grading member
Implementation Method 2
The particulate bodies of the particulate filler include a core formed from a semiconductor material, an oxide mixed layer deposited on the core, and a conducting oxide layer deposited on the oxide mixed layer to provide an electrical percolation path through the polymeric matrix triggered by strength of an electric field
Data Source
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Figure 3
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AI summary
A field grading composite body includes a polymeric matrix (108) and a particulate filler (110) distributed within the polymeric matrix (108). Particles of the particulate filler (110) include a core (114) formed from a semiconductor material, an oxide mixed layer (116) deposited on the core (114), and conducting oxide layer (118). The conducting oxide layer (118) deposited on the oxide mixed layer (116) to provide an electrical percolation path through the polymeric matrix (108) triggered by strength of an electric field extending through the field composite body. Conductors and methods of making field grading composite bodies for conductors are also described.