Shell Transformer Tank Structure for Internal Arc Overpressure
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Solution Overview
Problem
Existing solutions for shell-type transformers and reactors are inadequate in preventing tank rupture during internal arc faults, particularly due to insufficient flexibility and mechanical strength, leading to potential oil spills and fire hazards.
Innovation Solution
A tank design comprising an outer tank portion surrounding an inner tank portion with a deformable structure to absorb arc energy, reinforced by a cincture that forms a sealed chamber around the joints to contain insulating liquid and prevent spills.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tank is made strong and rigid to withstand short-circuit loads, then the tank can resume normal operation after short circuit, but the tank becomes less flexible and more prone to breaking under internal arc overpressure
Solution Approach 1:
The tank is divided into multiple segments: a rigid inner tank portion that withstands short-circuit loads and a more flexible outer tank portion that absorbs arc energy through deformation. This segmentation allows each part to have optimized mechanical properties for its specific function, resolving the contradiction between strength and flexibility.
Solution Approach 2:
Different regions of the tank are given different mechanical properties. The inner tank portion has high strength and stiffness for withstanding electromagnetic forces during short circuits, while the outer tank portion has lower strength and higher ductility for absorbing arc energy through plastic deformation. This local differentiation resolves the contradiction by applying appropriate material properties to specific locations.
2Reliability
If the tank is made flexible to absorb arc energy, then the tank can deform without breaking, but the tank cannot withstand high mechanical loads during short circuit operation
Solution Approach 1:
The tank structure is segmented into an inner portion that handles mechanical loads and an outer portion that handles arc energy absorption. The inner tank portion maintains high stiffness to resist electromagnetic forces during short circuits, while the outer tank portion is designed with lower stiffness to deform plastically under arc overpressure, thus resolving the contradiction between load-bearing capacity and energy absorption.
Solution Approach 2:
The tank employs asymmetric structural design where the inner tank portion has thicker walls and higher structural integrity for withstanding compressive and tensile forces during short circuits, while the outer tank portion has thinner walls and lower structural resistance to allow controlled deformation during arc events. This asymmetric design optimizes each region for its specific functional requirement.
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
The design effectively reduces the risk of tank rupture and oil spills by allowing the outer tank to deform, maintaining structural integrity during normal operation and absorbing arc energy, while containing the insulating liquid within the sealed chamber.
Implementation Method 1
the outer tank portion being designed with enough flexibility to absorb the internal arc energy by deforming outwards, without reaching rupture
Implementation Method 2
the outer tank portion provides a protection of the inner tank portion, and the increase in the inner volume caused by the deformation also reduces the overpressure inside the tank
Implementation Method 3
The insulating fluid surrounding the active part of the transformer or reactor may then vaporize and create an expanding gas bubble, causing an overpressure
Data Source
AI summary
A tank for a liquid-filled shell transformer or shell reactor is provided. The tank includes: a lower tank portion, and an upper tank portion comprising an inner tank portion with inner sidewalls and an outer tank portion with outer sidewalls arranged radially outwardly with respect to the inner sidewalls. The lower tank portion and the inner tank portion are joined together along a substantially horizontal first perimetric joining line and defining an internal space. A space is formed between the inner sidewalls and the outer sidewalls, such space being in fluid communication with the internal space. The outer and the inner tank portions are joined together along a substantially horizontal second perimetric joining line. The tank further includes a tank cover configured to be joined to an upper end of the outer sidewalls. A method for assembling and an adjustable pad are also provided.