Front-Accessible Current Transformer Bushing for Switchgear
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Solution Overview
Problem
In medium voltage switchgear with narrow width, current transformers mounted at the rear of the circuit breaker compartment are difficult to access for maintenance due to limited space, necessitating a solution for accessing them from the front.
Innovation Solution
A bushing structure with a hollow primary contact extending through the rear wall of the circuit breaker compartment, allowing current transformers to be mounted on the external portion and accessed from the front for maintenance, using a fastener structure that decouples from the busbar for removal and reinstallation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If current transformers are mounted at the rear of the circuit breaker compartment, then the switchgear width can be reduced, but the accessibility of current transformers for maintenance deteriorates
Solution Approach 1:
The current transformer assembly is segmented into a modular unit that includes the current transformer, bushing, and fastening structure. This modular segmentation allows the assembly to be removed and accessed from the front of the circuit breaker compartment, resolving the accessibility issue while maintaining the compact rear mounting configuration that reduces switchgear width.
Solution Approach 2:
A removable fastening structure acts as an intermediary between the current transformer assembly and the circuit breaker compartment. This fastening structure includes a mounting plate and fasteners that securely attach the assembly to the rear wall, yet allow for easy removal and front-side access, thus mediating between the compact rear mounting requirement and the maintenance accessibility requirement.
2Ease of operation
If current transformers are mounted inside the circuit breaker compartment, then accessibility for maintenance is improved, but the switchgear width increases
Solution Approach 1:
The current transformer assembly is positioned in a third dimension - mounted on the rear wall surface rather than inside the compartment volume or extending outward. This dimensional placement on the rear wall surface allows front-side accessibility through the compartment while maintaining compact switchgear width, as the assembly utilizes the wall surface area rather than consuming internal or external space.
3Area of stationary object
If current transformers are mounted externally at the rear, then switchgear width is reduced, but the complexity of maintenance procedures increases
Solution Approach 1:
The fastening structure is pre-configured with mounting plates and fasteners that are ready for quick attachment and detachment. This preliminary preparation of the fastening mechanism allows maintenance personnel to rapidly remove and reinstall the current transformer assembly without complex procedures, reducing maintenance complexity despite the external rear mounting configuration that reduces switchgear width.
Data Source
AI summary
A switchgear includes a circuit breaker housing defining a circuit breaker compartment. A bushing has first and second portions and extends through an opening in a rear wall of the housing so that the first portion is disposed in the circuit breaker compartment and the second portion is disposed beyond the exterior of the rear wall and external of the circuit breaker compartment. The bushing has a hollow primary contact. A current transformer is mounted on the second portion of the bushing. A fastener structure has a portion that extends through the hollow primary contact. The fastener structure couples the primary contact to a busbar in a removable manner. When the fastener structure is decoupled from the primary contact, the bushing and the at least one current transform can be accessed from the front of the housing and moved through the opening in the rear wall, for maintenance.