Conductive Corona Shielding Paper for High-Voltage Machines
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Solution Overview
Problem
High-voltage electrical machines face premature aging and potential failure due to intense electrical discharges, which degrade the outer corona shielding and lead to ground faults, as existing corona shielding materials fail to maintain optimal electrical resistance and conductivity, especially in the radial direction.
Innovation Solution
A corona shielding paper with planar and globular particles coated with conductive metal oxides, reinforced with organic or inorganic fibers, and integrated into a woven fabric to create anisotropic conductivity, providing resistance to partial discharges and improved mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If corona shielding papers containing carbon black and graphite are used, then conductivity is provided, but the material fails to maintain optimal electrical resistance and is completely incinerated by partial discharges over time
Solution Approach 1:
The patent changes the material parameters by using magnesium oxide particles with a specific particle size distribution (D10: 0.5-2 μm, D50: 3-6 μm, D90: 8-15 μm) and coating them with conductive metal oxides. This parameter optimization allows the material to maintain stable electrical resistance (10^-3 to 10^3 Ω·cm) while resisting partial discharge incineration, thereby extending service life.
Solution Approach 2:
The patent creates a composite material system consisting of magnesium oxide core particles coated with conductive metal oxide layers (such as zinc oxide, tin oxide, or indium oxide). This composite structure combines the partial discharge resistance of magnesium oxide with the conductivity of metal oxide coatings, solving both the reliability and harmful factors issues simultaneously.
2Reliability
If the resistance in the outer corona shielding is set too low, then conductivity is improved, but the laminated cores may be electrically shorted leading to high-current arcs
Solution Approach 1:
The patent optimizes the conductivity parameters by controlling the coating thickness and metal oxide composition on the particle surfaces. The conductive coating is applied in controlled amounts to achieve the target resistance range, preventing both electrical shorts and spark erosion while maintaining stable resistance characteristics under electrical loading.
3Reliability
If the resistance in the outer corona shielding is set too high, then electrical short prevention is improved, but high-voltage spark erosion occurs
Solution Approach 1:
The patent fine-tunes the resistance parameter within the optimal range (10^-3 to 10^3 Ω·cm) by adjusting the conductive coating characteristics. This optimized parameter setting ensures sufficient conductivity to prevent spark erosion while maintaining high enough resistance to prevent electrical shorts, eliminating the trade-off between these two harmful effects.
4Ease of manufacture
If conventional corona shielding materials are used, then basic conductivity is provided, but intense electrical field intensities cause complete incineration over time
Solution Approach 1:
The patent employs a composite material architecture where magnesium oxide particles serve as the base material providing partial discharge resistance, while conductive metal oxide coatings provide the necessary conductivity. This composite structure maintains ease of manufacture through conventional coating processes while dramatically improving resistance to partial discharge incineration.
Solution Approach 2:
The patent optimizes the particle size distribution parameters (D10: 0.5-2 μm, D50: 3-6 μm, D90: 8-15 μm) and coating characteristics to achieve the desired balance between conductivity and partial discharge resistance. These parameter optimizations enable the material to withstand intense electrical field intensities without complete incineration.
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 extends the service life of electrical machines by maintaining optimal electrical resistance and conductivity, reducing partial discharge activity and preventing premature aging, while allowing for adjustable conductivity settings to prevent electrical shorts and spark erosion.
Implementation Method 1
planar and electrically conductively coated particles
Implementation Method 2
particles have a core that is resistant to partial discharges and a coating that is resistant to partial discharges
Data Source
AI summary
A corona shielding paper for use in a corona shielding system for an electric machine, e.g. a high-voltage machine, may be produced by compacting partial discharge-resistant, planar, conductive particles but can include both reinforcement fibers and a woven fabric.