Why Should The High-voltage Shield Be Positioned At The High-voltage End Of The Epoxy Resin Bushing?
High-voltage shielding is positioned at the high-voltage end of an epoxy resin sleeve to control localized electric field stress, preventing partial discharge and dielectric breakdown where potential gradients are highest. Placing the conductive or semi-conductive shield directly around the conductor entry point flattens the equipotential lines across the solid insulation, ensuring long-term operational stability in demanding electrical environments.
Structural Decomposition of the Shielding System
The interior geometry of an epoxy bushing relies on integrated stress control components to handle severe electrical loads.
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Embedded Deflector Cone: Integrated directly within the cast body to smooth out field concentrations.
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Conductor Interface: A smooth metallic connection preventing air voids near the high-voltage terminal.
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Ground Layer Transition: The external conductive boundary that routes leakage current safely away from the core.
Internal Field Control Mechanisms
Inside the epoxy resin bushing, high voltage creates steep potential gradients near the central conductor. The high-voltage shield acts as an equipotential electrode, shifting the field stress away from triple points—where metal, solid epoxy, and gas or oil meet.
Material Selection for High-Voltage Shielding
Selecting compatible materials prevents mechanical shear stresses during thermal cycling.
| Component Part | Recommended Material | Function |
|---|---|---|
| Primary Body | Cycloaliphatic Epoxy Compound | Solid insulation & mechanical strength |
| Internal Shield | Aluminum / Brass Alloy | Field shaping & potential grading |
| Semi-Conductive Layer | Carbon-Doped Polymer | Gradual stress transition |
Manufacturing Highlights and Process Precision
Vacuum pressure casting ensures void-free encapsulation of the shielding assembly. Microscopic air pockets inside the casting trigger internal partial discharge under high stress. Proper curing profiles keep the thermal expansion coefficients of the metal shield and surrounding casting aligned, preventing internal delamination over extended service periods.
Dimensional and Electrical Parameters
Design calculations require precise radial clearances to maintain field strength below critical breakdown limits:
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Insulation wall thickness matched to peak impulse voltages.
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Minimum curvature radius on shield edges to stop corona formation.
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Surface creepage distance calculated for specific pollution environments.
Performance Differences in High-Voltage Positioning
Positioning the shield directly at the high-voltage end rather than relying on ground-side grading alters field distribution across the structure. This configuration reduces peak stress at the flange area, minimizes internal dielectric losses, and extends component longevity under continuous stress.
