Shell Transformer Tank Cincture for Arc-Fault Overpressure
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Solution Overview
Problem
Shell-type transformers and reactors are prone to tank rupture due to internal arc faults, which cause overpressure and mechanical stress, leading to potential oil spills and fires, as existing solutions like pressure relief devices and C-shaped clamps are insufficient in providing adequate protection against high tensile stress.
Innovation Solution
A tank design featuring a reinforcing cincture that surrounds the perimetric joining line between the lower and upper tank portions, forming a sealed chamber to enhance the ultimate tensile strength of the joint and displace stress to more absorbent regions, thereby preventing oil spills and fire risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a simple welded joint is used between lower and upper tank portions, then the manufacturing process is simple and cost-effective, but the joint lacks flexibility and ultimate tensile strength, making it prone to breaking under overpressure from internal arc faults
Solution Approach 1:
The patent applies a reinforcing cincture specifically at the perimetric joining line between lower and upper tank portions, where the stress concentration occurs during internal arc faults. This localized reinforcement provides enhanced ultimate tensile strength exactly where needed, rather than strengthening the entire tank structure uniformly. The cincture creates a sealed chamber that encloses the vulnerable weld joint, allowing it to withstand overpressure without breaking while maintaining simplicity elsewhere in the tank design.
2Reliability
If the tank is made more rigid to prevent deformation, then structural stability is improved, but the tank becomes less able to accommodate overpressure without breaking when subject to high tensile stress from internal arcs
Solution Approach 1:
The patent divides the tank into lower and upper portions joined by a perimetric joining line, and introduces a reinforcing cincture that creates a sealed chamber enclosing this joint. This segmentation allows the vulnerable weld joint to be isolated within the sealed chamber, where it can deform slightly to accommodate overpressure without causing catastrophic failure. The cincture itself acts as a flexible reinforcement that can stretch and deform under stress while maintaining the overall structural integrity of the tank.
3Reliability
If pressure relief devices are installed to release overpressure, then the risk of tank rupture is reduced, but these devices may not be sufficient to prevent rupture in shell-type transformers under high tensile stress from internal arcs
Solution Approach 1:
The patent implements a sealed chamber created by the reinforcing cincture that encloses the perimetric joining line between lower and upper tank portions. This sealed chamber acts as a protective barrier that confines the insulating liquid in case the weld joint fails under extreme overpressure from internal arc faults. By providing this additional containment layer beforehand, the system prevents oil spills and fire risks even when the primary weld joint breaks, eliminating the need for pressure relief devices that might release harmful oil into the environment.
Data Source
AI summary
A tank for a liquid-filled shell transformer or shell reactor is disclosed. It comprises a lower tank portion with a bottom plate and side walls, and an upper tank portion with side walls. The upper and lower tank portions are joined together along a substantially horizontal perimetric joining line and define an internal space for housing an active part of the shell transformer or shell reactor and an insulating liquid. The tank further comprises a reinforcing cincture surrounding and joined to the side walls of the lower tank portion and the upper side walls of the upper tank portion and forming a sealed chamber enclosing the perimetric joining line between the lower tank portion and the upper tank portion. A shell transformer or reactor provided with such a tank is also disclosed, as well as a method for assembling a shell transformer or reactor.