Distribution Transformer Bushing Assembly for Leak-Tight Disk Sealing
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Solution Overview
Problem
The attachment of a metal annular disk to the insulating material in electrical bushings for distribution transformers is problematic, as it must prevent the escape of transformer liquid while ensuring a mechanically sound connection.
Innovation Solution
The bushing assembly features a metal annular disk welded to the housing, with first and second tubular bushing portions made of cast epoxy resin surrounding the conductor, and a threaded connection between them, along with O-rings to prevent liquid leakage, and a design that allows the disk to be a separate component from the bushing portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the metal annular disk is attached to the insulating material by casting as an integral component, then the mechanical connection is strong, but the manufacturing complexity increases and the disk cannot be easily replaced
Solution Approach 1:
The bushing assembly is divided into separate components: the metal annular disk, the cast epoxy insulating material, and the conductor. The disk is attached to the insulating material through a standardized recess and flange connection rather than being cast as an integral component, allowing independent manufacturing and assembly of each part.
Solution Approach 2:
The insulating material is cast with a pre-formed recess and flange structure that is designed to receive and secure the metal annular disk. This preliminary preparation of the casting mold ensures proper alignment and mechanical connection without requiring complex post-assembly operations.
2Ease of manufacture
If the metal annular disk is made as a separate component, then the assembly is easier to manufacture and maintain, but the sealing reliability against transformer liquid escape becomes problematic
Solution Approach 1:
A sealing mechanism is introduced as an intermediary element between the metal annular disk and the insulating material. The flange of the disk engages with the recess in the insulating material to create a sealing interface that prevents transformer liquid from escaping along the annular connection while maintaining component separability.
Solution Approach 2:
The sealing interface utilizes the flexible deformation capability of the insulating material's recess and the disk's flange to create an effective seal. The materials are selected to allow slight deformation that ensures tight contact and prevents liquid leakage while maintaining the ability to assemble and disassemble the components.
3Strength
If the bushing portions are cast as a single integral piece, then the structural integrity is high, but the adaptability to different conductor sizes and the ease of assembly are reduced
Solution Approach 1:
The insulating bushing is divided into multiple portions that can be assembled around the conductor. This segmentation allows the bushing to accommodate different conductor sizes and types while maintaining structural integrity through the combined assembly. Each portion can be independently manufactured and then assembled to form the complete insulating structure.
Solution Approach 2:
The modular bushing design creates a universal assembly that can adapt to various conductor configurations. The standardized connection interfaces and scalable portion design allow the same basic bushing structure to serve multiple applications with different electrical and mechanical requirements.
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 design ensures a secure mechanical connection and effective seal, preventing transformer liquid leakage while allowing the bushing to be easily assembled and preventing rotation of the conductor.
Implementation Method 1
The first bushing portion is cast on the elongate conductor so that an interior surface thereof forms an integral bond with an exterior surface of the elongate conductor
Implementation Method 2
at least one sealing O-ring preventing passage of the transformer liquid from the interior of the housing past the abutment surfaces to the exterior
Implementation Method 3
the metal disk having an exposed outer rim portion arranged for welded attachment to an edge of the aperture in the housing
Data Source
AI summary
An electrical bushing for a transformer housing includes an elongate conductor with a metal annular disk for welded attachment to an edge of an aperture in the housing with an insulating bushing between the conductor and the disk. The insulating bushing includes first and second tubular bushing portions each formed of a cast epoxy resin and each surrounding a portion of the elongate conductor. the first bushing portion is cast on the elongate conductor with an integral bond therewith. The second bushing portion can slide along the exterior surface of the elongate conductor and is threaded onto a male portion of the first bushing portion. The first and second bushing portions have annular abutment surfaces clamping the annular disk therebetween and typically three sealing O-rings are provided at the junction to prevent passage of the transformer liquid from the interior.