Electrical Bushing Joint With Compressible Thermal Stress Buffer

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Solution Overview

Problem

Existing electrical bushings experience premature failure due to mechanical stress caused by differing thermal expansion coefficients of materials in the core and flange, particularly in outdoor applications with large temperature fluctuations.

Innovation Solution

Incorporating a compressible material within the joint between the flange and core to absorb thermal expansion, using a locking compound to secure the flange to the core, allowing the compressible material to compress or expand in response to thermal changes, thereby reducing mechanical stress on the locking compound.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a locking compound is used to fixate the core and flange, then the joint strength is improved, but the reliability deteriorates due to thermal expansion stress

Engineering Contradiction:
Improvejoint strengthVSAvoidjoint reliability
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

A compressible material is introduced as an intermediary element between the core and flange, filling the joint volume alongside the locking compound. This compressible material acts as a mediator that absorbs thermal expansion stresses through compression and expansion, preventing these stresses from being transmitted to the locking compound and thereby maintaining joint reliability under temperature variations.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The compressible material provides variable volume capability to the joint, allowing the joint volume to change in response to thermal expansion. This parameter change (volume adjustment) enables the joint to accommodate differential thermal expansion between the core and flange without generating excessive mechanical stress on the locking compound.

Inventive Principle:
Principle #35Parameter changes

2Adaptability or versatility

If the bushing is designed for outdoor applications, then the adaptability is improved, but the reliability deteriorates due to temperature fluctuations

Engineering Contradiction:
Improveapplication rangeVSAvoidjoint reliability
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The compressible material is specifically designed to exploit thermal expansion principles, expanding when the joint volume increases due to temperature changes and compressing when the joint volume decreases. This direct application of thermal expansion theory allows the bushing to reliably operate in outdoor environments with large temperature fluctuations by accommodating the thermal movement of the core and flange.

Inventive Principle:
Principle #37Thermal expansion

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

Enhances the temperature tolerance and mechanical stability of the bushing, enabling operation over a wider temperature range and allowing the use of higher-toughness materials, reducing the risk of joint failure.

Implementation Method 1

the volume of the joint may change during operation of the bushing on account of different thermal expansion coefficients of materials for the flange and the core

Methodology Applied
Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the compressible material is configured to compress or expand in response to a change in the volume of the joint

Methodology Applied
Scientific EffectCompression: Compression

Data Source

PatentEP3979267B1Electrical bushing and method of producing an electrical bushing
Publication Date: 2025.08.27 HITACHI ENERGY LTD
  • EP3979267B1 patent drawingFigure 1
  • EP3979267B1 patent drawingFigure 2
  • EP3979267B1 patent drawingFigure 3

AI summary

An electrical bushing (1) is specified, the bushing comprising a flange (3) with a lower part (31) and an upper part (32) affixed to one another and further comprising a core (2) surrounded by the flange, wherein the flange is affixed to the core by a locking compound (45) disposed in a volume of a joint (10) between the flange and the core, and wherein the volume of the joint further comprises a compressible material (4), the compressible material being configured to compress or expand in response to a change in the volume of the joint. Furthermore, a method of producing an electrical bushing (1) is specified.