Corona Shielding System with Anisotropic Conductivity
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Solution Overview
Problem
High electrical field intensities in electrical machines lead to partial discharges, causing premature aging and potential failure of the outer corona shielding system, which is critical for insulation and voltage management, as existing systems struggle to maintain optimal resistance and conductivity ratios.
Innovation Solution
A corona shielding system comprising a polymeric matrix with a mixture of planar and spherical particles resistant to partial discharges, where the particles are electrically conductive and coated with metal oxides, allowing for adjustable anisotropic conductivity and resistance, enhancing the system's stability and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer corona shielding uses conventional carbon black and graphite tapes or lacquers, then it provides basic electrical conductivity, but high electrical field intensities cause partial discharges that completely incinerate the shielding over time, leading to premature aging and ground faults
Solution Approach 1:
The patent applies composite materials by combining carbon black particles with graphite particles in a polymeric matrix. This composite filler system provides enhanced resistance to partial discharges compared to conventional single-material corona shields. The carbon black and graphite work synergistically to maintain electrical conductivity while resisting incineration from partial discharge activity, thereby extending service life and improving reliability.
Solution Approach 2:
The patent changes the material parameters of the corona shielding by specifying a polymeric matrix containing both carbon black and graphite fillers. This parameter change transforms the shielding from conventional organic-only materials to a composite system with superior resistance to partial discharges. The specific composition parameters (carbon black with graphite) are selected to achieve optimal balance between conductivity and partial discharge resistance.
2Reliability
If the outer corona shielding has low square resistance, then it conducts electricity well, but the laminated cores may be electrically shorted, causing high induced circulating currents and high-current arcs
Solution Approach 1:
The patent changes the electrical resistance parameter of the corona shielding by using a composite filler system of carbon black and graphite in a polymeric matrix. This allows precise control of the square resistance to an optimal range that provides sufficient conductivity to prevent charge accumulation while being high enough to prevent electrical shorting of the laminated cores. The composite material enables fine-tuning of this critical parameter.
Solution Approach 2:
The patent applies local quality by creating a corona shielding with spatially varying properties through the composite filler distribution. The carbon black and graphite particles are distributed throughout the polymeric matrix to provide localized conductivity where needed while maintaining areas of higher resistance to prevent core shorting. This non-uniform but controlled property distribution optimizes both conductivity and protection functions.
3Reliability
If the outer corona shielding has high square resistance, then it prevents electrical shorting, but high-voltage spark erosion occurs
Solution Approach 1:
The patent changes the resistance parameter to an optimal intermediate value using the carbon black-graphite composite filler system. This parameter optimization ensures the corona shielding has sufficient resistance to prevent electrical shorting of the laminated cores while maintaining low enough resistance to prevent high-voltage spark erosion. The composite material provides a balanced electrical property that simultaneously addresses both extremes.
Solution Approach 2:
The patent uses composite materials (carbon black with graphite in polymeric matrix) to achieve a balance between resistance and conductivity that single materials cannot provide. The composite system provides sufficient electrical resistance to prevent core shorting while maintaining adequate conductivity to dissipate charges and prevent spark erosion. This material composition resolves the contradiction between protection and conductivity.
4Ease of manufacture
If the interface between the outer corona shielding and main insulation is produced with conventional methods, then manufacturing is straightforward, but pores cannot be completely eliminated, causing high partial discharge activity that incinerates the shielding
Solution Approach 1:
The patent applies composite materials at the interface between the corona shielding and main insulation. The carbon black-graphite composite filler system in the polymeric matrix provides self-healing properties that compensate for interface pores. The conductive composite material can bridge small voids and defects at the interface, reducing partial discharge activity that would otherwise incinerate the shielding, while still allowing for practical manufacturing methods.
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 provides a stable and reproducible corona shielding system with improved conductivity in the radial direction, reducing the risk of overheating and extending the service life of electrical machines by maintaining optimal electrical resistance and conductivity ratios.
Implementation Method 1
the filler comprising both planar and spherical particles that are resistant to partial discharges and electrically conductive
Implementation Method 2
establish an anisotropy that displays increased conductivity in the radial direction, that is to say from the current-carrying conductor to the laminated core
Data Source
AI summary
A corona shielding system for an electric machine, for example a high-voltage machine, such as a generator, for generating electrical energy, an electric motor or else other electric operating means having a relatively high rated voltage, such as transformers, bushings, cables, etc, is disclosed. The corona shielding system may include a filler mixture including both planar and spherical particles. Therefore, the electrical conductivity, which is good in the presence of only planar particles in two spatial directions but is very poor in the third, can be adjusted anisotropically in a targeted manner.