Stationary Induction Apparatus Electrostatic Shield Design
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Solution Overview
Problem
Conventional stationary induction apparatuses with electrostatic shields face challenges in reducing electric field concentration at the ends of the shields without thickening, which can lead to dielectric breakdown due to potential oscillations caused by impulse voltages like lightning surges.
Innovation Solution
The apparatus includes annular electrostatic shields with a conductor and a second insulating coating, where the conductor is discontinuous to prevent full circumference current flow, and the shields are designed with varying curvature radii and widths equivalent to the winding, ensuring the potential of the shields is lower than the winding, thereby reducing electric field concentration without thickening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the curvature radii of the outer peripheral ends and inner peripheral ends of the electrostatic shields are increased to reduce electric field concentration, then the electrostatic shields become thicker, but this increases the size of the stationary induction apparatus
Solution Approach 1:
The electrostatic shield is designed with non-uniform thickness distribution, where the thickness varies along the axial direction. The shield has greater thickness at positions where electric field concentration is more severe and thinner thickness where the electric field is less concentrated. This local quality variation allows the shield to effectively reduce electric field concentration at critical points without uniformly increasing the overall thickness of the shield, thereby avoiding increased apparatus size.
Solution Approach 2:
The invention changes the thickness parameter of the electrostatic shield from a constant value to a variable value that depends on the position along the axial direction. By adjusting the thickness parameter locally according to the electric field distribution characteristics, the shield achieves effective electric field concentration reduction while maintaining compact dimensions and avoiding unnecessary increase in apparatus size.
2Reliability
If electrostatic shields are installed adjacent to windings to reduce potential oscillations, then the electrostatic capacitance between windings increases, but this requires additional space and increases device complexity
Solution Approach 1:
The electrostatic shield performs multiple functions simultaneously: it suppresses potential oscillations by increasing electrostatic capacitance between windings, reduces electric field concentration at its ends through non-uniform thickness design, and provides electrical insulation between the winding and ground. By integrating these multiple functions into a single component, the invention achieves reliable potential oscillation suppression without proportionally increasing device complexity.
Solution Approach 2:
The electrostatic shield is positioned within the existing structural space of the stationary induction apparatus, nested between the winding and the ground or outer structure. This nested arrangement allows the shield to be integrated into the existing design without requiring significant additional space or structural modifications, thereby achieving reliable potential oscillation suppression with minimal increase in device complexity.
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
This design effectively mitigates electric field concentration at the ends of the electrostatic shields, reducing potential oscillations and enhancing insulation performance while maintaining the shields' thickness, thus preventing dielectric breakdown.
Implementation Method 1
the electrostatic capacitance between the windings becomes larger than the electrostatic capacitance between the winding and the ground, thus reducing the amplitude of potential oscillations
Implementation Method 2
When electrostatic shields are installed adjacent to windings, the electrostatic capacitance between the windings becomes larger than the electrostatic capacitance between the winding and the ground
Data Source
AI summary
A stationary induction apparatus includes a core, a winding wound around the core such that the core serves as a central axis, and an annular electrostatic shield disposed adjacent to at least one of ends of the winding in a direction along the central axis. The electrostatic shield includes a conductor and a second insulating coating that coats the conductor. The electrostatic shield has a potential lower than a highest potential in the winding.