Integrated Bushing Structure for Compact Switchgear Design
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Solution Overview
Problem
Conventional medium voltage switchgears face increased design and assembly complexity due to separate compartments for current transformers and primary contacts, which necessitate longer bushing lengths at higher currents, thereby increasing switchgear depth and width.
Innovation Solution
A bushing structure that combines the functionality of a primary contact, current transformer primary conductor, and post insulator, featuring a barrel portion with undulations for increased creepage distance and integrated metallic shields to reduce switchgear dimensions, with current transformers mounted on the bushing structure within the bus/cable compartment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current transformers are mounted in a separate circuit breaker compartment from primary contacts, then functional separation is achieved, but design and assembly complexity increases
Solution Approach 1:
The patent combines the primary contact bushing and current transformer into a single integrated assembly. The bushing structure includes an insulating body with a primary contact extending through it, and the current transformer is mounted directly on the bushing, eliminating the need for separate mounting in different compartments. This merging reduces design and assembly complexity while maintaining functional separation through the wall between compartments.
2Reliability
If bushing length is increased to maintain sufficient creepage distance at higher current ranges, then electrical insulation is improved, but switchgear depth increases
Solution Approach 1:
The patent addresses the creepage distance requirement by adding peripheral undulations to the bushing surface. These undulations increase the creepage path length along the surface without increasing the overall axial length of the bushing. This dimensional approach allows maintaining sufficient creepage distance for high current applications while keeping the switchgear depth compact.
3Reliability
If bushing length is increased to maintain sufficient creepage distance, then electrical insulation is improved, but overall switchgear width increases
Solution Approach 1:
The peripheral undulations on the bushing surface provide increased creepage distance without expanding the radial or axial dimensions of the bushing. By utilizing the surface topology rather than increasing overall size, the patent maintains electrical insulation requirements while keeping the switchgear width compact.
4Area of stationary object
If current transformers are relocated to the bus/cable compartment on the bushing structure, then switchgear depth and width are reduced, but mounting complexity increases
Solution Approach 1:
The current transformer is integrated with the bushing structure through a unified mounting arrangement. The bushing serves as both the insulating support for the primary contact and the mounting base for the current transformer. This combined structure simplifies mounting by eliminating separate mounting brackets or supports, reducing overall switchgear dimensions while maintaining installation simplicity.
Data Source
AI summary
A bushing structure for a switchgear includes a mounting portion constructed and arranged to mount the bushing structure. A barrel portion extends from the mounting portion and is coaxial there-with. The barrel portion includes a plurality of undulations in a peripheral surface thereof to increase creepage distance. A primary contact is disposed within and extends a length of the barrel portion. The primary contact has a first end constructed and arranged to be contacted by a movable contact of the switchgear and a second end constructed and arranged to be connected with a busbar.