Circuit Breaker Stab Bus Insulation for Reduced Triple-Point Discharge
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Solution Overview
Problem
Partial discharges in insulators due to gaps between materials with different dielectric constants lead to accelerated aging and breakdown, exacerbated by thermal and mechanical stresses, necessitating a solution to minimize these discharges.
Innovation Solution
The design features a circular disk plate with raised embosses and tapped inserts, along with an insulator sleeve, which increases gap distances between the disk plate and conductor surfaces to reduce triple point regions, thereby minimizing partial discharges. The embosses and inserts are strategically positioned to reduce electric field concentration and formation of triple points, using a curved contour on the disk plate to further mitigate field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gap distances are increased to reduce triple point regions, then partial discharge occurrence is reduced, but device complexity increases
Solution Approach 1:
The patent applies curvature to the electrode surface at the triple point junction, replacing sharp edges with rounded contours. This curved geometry redistributes the electric field more uniformly, reducing field concentration at the triple point where the electrode meets the insulator. The rounded electrode design eliminates the need for increased gap distances while maintaining reduced partial discharge occurrence.
Solution Approach 2:
The patent modifies the geometric parameters of the electrode, specifically changing from flat or sharp-edged surfaces to curved surfaces with optimized radii. This parameter change in the electrode shape directly affects the electric field distribution, reducing field strength at the triple point junction without requiring changes to the gap distances or overall device structure.
2Duration of action of stationary object
If electrode shape is optimized to minimize partial discharges, then insulator lifespan is extended, but manufacturing precision requirements increase
Solution Approach 1:
The curved electrode design with standardized radii provides robust geometric features that are tolerant to normal manufacturing variations. The curvature radius can be specified as a range rather than an exact value, and the beneficial electric field distribution effect is maintained throughout this range, reducing the stringency of manufacturing precision requirements.
Solution Approach 2:
The patent applies the curved geometry specifically at the critical triple point junction region, while other portions of the electrode can maintain simpler geometries. This localized application of curvature focuses the manufacturing precision requirements only where they are most critical for electric field control, rather than requiring high precision across the entire electrode structure.
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 configuration effectively reduces the occurrence of partial discharges in the insulator sleeve by minimizing triple point regions and electric field concentration, thereby extending the useful life of the insulator and preventing potential equipment damage.
Implementation Method 1
an insulator that is externally exposed to a very high electric field strength will break down through its bulk in an electrical discharge
Implementation Method 2
imposing an externally applied electric field on the insulator, which is high enough to accelerate the electrons of the insulator to ionization energy that ionizes neutral atoms and molecules of the insulator in an avalanche building process
Implementation Method 3
The gaps may have a lower dielectric constant than the dielectric constant of the insulator. This difference in dielectric constants causes the insulator to effectively push the equipotential field lines of the electric field into the space occupied by the gap, causing the field to be concentrated in the gap
Data Source
AI summary
A draw out circuit breaker has a reduced partial discharge in insulation surrounding a primary stab bus. A circular disk plate on one end of the bus includes tapped inserts located at a radial separation distance from the bus. An insulator sleeve surrounding the bus is formed to encapsulate the tapped inserts. Raised embosses on the circular disk plate separate the end portion of the insulator sleeve by a gap distance from the inward facing surface of the disk plate. The increased gap distance reduces formation of a triple point region between the surface of the disk plate and the insulator sleeve, thereby reducing occurrence of partial discharges in the insulator sleeve near the gap.