Topographic Shielding for Medium Voltage Switchgears
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Solution Overview
Problem
Existing shielding elements for medium voltage switchgears with vacuum interrupters face challenges in effectively absorbing energy during arcing, particularly due to limitations in material thickness and complexity in production, which affect their interrupting capability and manufacturing efficiency.
Innovation Solution
The shielding element features a topographic surface structure with a surface area enhancement, achieved through abrasive particle blasting or crosswise arranged grooves (knurl-structures), which increases energy absorption without increasing material volume, allowing for efficient energy dissipation during arcing and easy manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the wall thickness of the shielding element is increased to provide enough bulk material for machining a profiled shielding, then the manufacturing complexity and material consumption increase, but the energy absorption capability is improved
Solution Approach 1:
The invention transitions from modifying the shielding in the volume dimension (increasing wall thickness) to modifying it in the surface dimension (adding topographic structures). By creating grooves, ridges, and other surface features on the inner surface of the shielding element, the effective surface area is multiplied without increasing the overall volume or wall thickness, thus resolving the contradiction between energy absorption and structural simplicity.
Solution Approach 2:
The invention creates a porous-like topographic structure on the inner surface of the shielding element through grooves, ridges, and other features. This increased surface area provides more sites for energy absorption during arcing events, effectively enhancing the shielding's energy handling capability without requiring additional bulk material or increasing wall thickness.
2Reliability
If profiled shielding is used to absorb more metal vapour during switching, then the interrupting capability is improved, but the manufacturing process becomes more complex requiring machining
Solution Approach 1:
The topographic surface structures (grooves, ridges, etc.) are pre-formed on the shielding element during the molding process itself, rather than requiring subsequent machining operations. This preliminary creation of the energy-absorbing surface features during manufacturing maintains production efficiency while achieving the desired interrupting capability enhancement.
3Loss of energy
If the surface area of the shielding element is increased through microstructuring, then the energy absorption is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The invention modifies the surface parameters of the shielding element by introducing topographic features (grooves, ridges, etc.) that multiply the effective surface area. These structural parameter changes are achieved through standard molding techniques rather than complex microstructuring processes, enhancing energy absorption while maintaining manufacturing simplicity.
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 surface structure design significantly enhances energy absorption during arcing, maintaining high performance and reproducibility in vacuum interrupters, while avoiding material sticking issues and reducing the risk of performance degradation, thus improving the overall energy handling capability and manufacturing simplicity.
Implementation Method 1
the topographic surface structure is a blasted surface treated by abrasive particle blasting
Implementation Method 2
the maximum possible energy absortion in case of occuring light arcing is achieved
Implementation Method 3
the topographic structure consists of crosswise arranged grooves, so called knurl-structures
Implementation Method 4
The knurling has a great surface multiplying factor, so that energy can be absorbed by a greater surface
Implementation Method 5
The copper or copper-chromium material wets the surface of the shielding material. That means the material stays at the surface with a good binding condition
Data Source
Figure 1
AI summary
The invention relates to a shielding element for the use in medium voltage switchgears with vacuum interrupters with at least two contacts, which are movable along a switching path between closed and open contact position, wherein the shielding element is positioned around the contact position region in the vacuum interrupter, wherein at least the inner surface of the shielding is applied with a topographic structure which is a rough or a structured surface, according to claim 1. In order to enhance the energy absorbance behavior of the at least the shielding, the implemented topographic structure is formed in such a way, that by given constant or approximately constant volume (Vi) of the shielding body, the surface ratio of the treated surface (S2) with implemented surface structure, and a untreated surface (S1) without topographic structure is greater than 1, so that this follows the condition V1 ~ V2 and S2/S1 >1.