Primary Stab Bus Insulation Structure for Reduced Partial Discharge
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Solution Overview
Problem
Partial discharges in insulation due to gaps and differences in dielectric constants between insulating materials and air pockets, leading to accelerated ageing and potential breakdown of insulators.
Innovation Solution
An optimized shape and positioning of an electrode at a triple point junction with an insulator, featuring a circular disk plate with raised embosses and tapped inserts, which increase gap distances between the insulator and conductor surfaces to reduce the formation of triple point regions and minimize partial discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the insulator is placed close to the conductor to reduce space, then the device compactness is improved, but triple point regions form causing partial discharges that degrade the insulator
Solution Approach 1:
A cylindrical protrusion extends from the conductor into the insulator, creating an intermediary structure that eliminates triple point regions. This protrusion acts as a mediator between the conductor and insulator, allowing close placement while preventing partial discharges by ensuring the insulator surface is everywhere in substantial contact with the conductor surface or the protrusion surface.
Solution Approach 2:
The insulator is designed with varying gap distances - minimal gap distances in regions where the insulator contacts the conductor directly, and increased gap distances in regions where the insulator contacts the cylindrical protrusion. This local variation optimizes both compactness and reliability by placing the insulator close to the conductor where safe, and maintaining larger distances where triple points would form.
2Length of stationary object
If the gap distance between insulator and conductor is reduced to minimize space, then the device size is decreased, but partial discharge occurrence increases due to triple point formation
Solution Approach 1:
The cylindrical protrusion serves as an intermediary structure that extends into the insulator, allowing the insulator to be positioned with minimal gap distances while preventing triple point formation. The protrusion ensures that wherever the insulator surface is close to the conductor, it is in substantial contact, eliminating the conditions for partial discharge.
Solution Approach 2:
The solution moves from considering only the radial gap distance to incorporating the axial dimension with the cylindrical protrusion extending into the insulator. This dimensional change allows minimal radial gaps while using the axial extension to prevent triple points, effectively reducing the overall space while eliminating harmful partial discharges.
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 effectively reduces the occurrence of partial discharges in the insulator sleeve by minimizing the formation of triple point regions, thereby extending the useful life of the insulator and preventing potential equipment damage.
Implementation Method 1
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.
Implementation Method 2
This concentrated field will cause the portion of the insulator adjacent to the gap to undergo an electrical discharge.
Implementation Method 3
The tapped inserts have a rounded head portion mounted on a shaft portion that extends beyond the shaft portion forming a step to reduce a concentration of electric field in the first gap area between the disk plate surface and the insulator sleeve.
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.