Conductive-Head Bushing Sealing for Thermal Stress Relief
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Solution Overview
Problem
Existing high-voltage bushing designs face issues with thermal shrinkage-induced mechanical stresses and compromised gas/liquid tightness due to resin expansion or contraction with temperature changes, leading to potential cracks and leaks.
Innovation Solution
A bushing design without a winding tube, featuring an electrically insulating condenser core with a conductive head that seals the first end, allowing the condenser core to expand and contract freely, and maintaining electrical potential with the conductor and field-grading layers, preventing flash-overs and ensuring gas tightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the condenser core resin is hardened at high temperature, then the initial gas/liquid tightness is improved, but thermal shrinkage generates mechanical stresses leading to cracks
Solution Approach 1:
A flexible sealing element (O-ring or elastomeric material) is introduced as an intermediary between the condenser core and the winding tube/flange. This sealing element compensates for dimensional changes and stress concentrations, preventing crack formation while maintaining gas/liquid tightness across temperature variations.
Solution Approach 2:
The sealing solution changes the physical parameters of the sealing interface by using elastomeric materials with high flexibility and temperature resistance. These materials can deform to accommodate thermal expansion/contraction of the condenser core without generating harmful stresses, thus resolving the contradiction between initial tightness and crack resistance.
2Strength
If the condenser core resin is hardened at low temperature, then mechanical stresses are reduced, but gas/liquid tightness is compromised at high temperatures
Solution Approach 1:
The flexible sealing element acts as a mediator that maintains gas/liquid tightness at high temperatures without requiring the condenser core resin to withstand high thermal stresses. The sealing element compensates for dimensional changes, ensuring continued sealing performance regardless of the resin's hardening temperature.
3Reliability
If a winding tube is used to provide gas/liquid tightness, then sealing is improved, but mechanical stresses and crack risk increase
Solution Approach 1:
The flexible sealing element (O-ring or elastomeric material) serves as an intermediary sealing mechanism that replaces the rigid winding tube sealing approach. This intermediary component provides gas/liquid tightness through elastic deformation rather than rigid constraint, eliminating the stress concentration and crack risk associated with the winding tube design.
Solution Approach 2:
The sealing solution employs flexible elastomeric materials (such as O-rings or thin film seals) that can deform to accommodate thermal and mechanical stresses. These flexible sealing elements maintain gas/liquid tightness without transmitting harmful stresses to the condenser core, resolving the contradiction between sealing performance and crack resistance.
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 reduces mechanical stresses, prevents crack formation, and maintains gas tightness across varying temperatures, enhancing the reliability and durability of the bushing.
Implementation Method 1
the thermal shrinkage of the resin generates mechanical stresses which are particularly concentrated at the lower end of the winding tube P4
Implementation Method 2
when the bushing operates in high ambient temperature or in an overload condition, the winding tube P4 can reach a temperature higher than the resin hardening temperature. Then the resin expands more than the tube and a gap can open between the tube and the condenser core P5
Data Source
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AI summary
The present disclosure relates to a bushing (1) comprising an electrical conductor (2) comprising a terminal (3) at a first end of the bushing. The bushing also comprises an electrically insulating condenser core (5) arranged around the conductor and defining a central longitudinal through-hole (9) through which the conductor extends. The bushing also comprises a plurality of concentric field-grading layers (6) arranged in the condenser core, comprising an inner field-grading layer (6a) and an outer field-grading layer (6b). The bushing also comprises an electrically conductive head (4) electrically connected with the conductor passing there through, forming a gas-tight cap of the first end of the bushing outside of the condenser core, sealingly engaging a circumferential lateral outer surface of the condenser core and sealingly engaging the conductor. The bushing also comprises an electrically conductive connection (11) between the inner field-grading layer and the head.