Arc Control in Fuse Detection for Transformer Protection
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Solution Overview
Problem
Current transformer protection systems using micro-fuses face issues with electric arcs during overload detection, leading to potential explosions and limitations in power usage due to the inability to effectively extinguish arcs and maintain coordination between high and low voltage fuses.
Innovation Solution
A transformer protection system with a micro-fuse contained in an oil-tight enclosure and a striker wire outside, utilizing two electrodes and a varistor or resistive wire in series to maintain and control the electric arc outside the enclosure, ensuring it lasts for the duration of high-voltage fuse melting, thus preventing arc return to the fuse cartridge and optimizing fuse coordination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If micro-fuses are used for overload detection in transformer protection systems, then detection precision is improved, but the electric arc generated during detection cannot be extinguished, leading to potential explosions and reduced reliability
Solution Approach 1:
The harmful electric arc is extracted from the fuse cartridge enclosure by providing a dedicated arc control path through the striker wire and electrodes outside the enclosure. The micro-fuse remains inside the oil-tight enclosure for precise detection, while the arc is directed outside to be controlled and extinguished, separating the detection function from the arc extinction function.
Solution Approach 2:
The striker wire and electrodes act as intermediary elements between the micro-fuse and the external environment. When the micro-fuse melts, it initiates an arc that is transferred to the striker wire, which then transfers it to the electrodes for controlled extinction. This intermediary mechanism allows the micro-fuse to detect overloads precisely while the intermediary structures handle the dangerous arc extinction.
2Adaptability or versatility
If micro-fuses are used for overload detection, then detection capability is improved, but the fuse cartridge may explode due to uncontrolled arcs, increasing harmful factors
Solution Approach 1:
The harmful electric arc is converted into a beneficial signaling mechanism. Instead of allowing the arc to explode the fuse cartridge, the arc is directed through the striker wire to trigger the striker, which then activates the short-circuiting device to disconnect the transformer. The arc's energy is thus converted from a destructive force into a useful protection signal.
Solution Approach 2:
The striker wire and electrodes serve as intermediary structures that intercept and control the arc before it can damage the fuse cartridge. The striker wire is positioned to receive the arc from the melted micro-fuse, and the electrodes provide a controlled path for arc extinction, preventing the arc from returning to the enclosure and causing explosions.
3Power
If high voltage fuses are used with larger power ratings, then power distribution capability is improved, but the coordination between high and low voltage fuses deteriorates, reducing measurement precision
Solution Approach 1:
The protection system is segmented into two distinct functions: the micro-fuse inside the oil-tight enclosure handles precise overload detection for coordination with low-voltage fuses, while the high-voltage fuse handles main protection and power interruption. This segmentation allows each component to be optimized for its specific function, maintaining precise coordination even in high-power applications.
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 solution effectively controls energetic electric arcs, prevents fuse cartridge explosions, and enhances fuse coordination, allowing for higher power transformers with smaller high voltage fuses and increased low voltage power distribution, reducing costs and improving system reliability.
Implementation Method 1
When a fault current appears on any of the phases, the micro-fuse wire 4 of the detection device associated with the phase melts and an electric arc appears
Implementation Method 2
means for maintaining and limiting in amplitude, for a given period, outside the enclosure and close to the micro-fuse, an electric arc which forms after the micro-fuse and the striker wire have melted
Data Source
Figure 1
Figure 2~4a
Figure 4b~5
AI summary
The device has varistor (VR) connected in series between two electrodes (E1, E2), and an oil proof enclosure (3) including a micro-fuse (4) and a fuse cartridge (1) with fusion in sand or in air. The electrodes and the varistor maintain and limit an electric arc in amplitude for a given duration outside the enclosure and near the micro-fuse, where the arc is formed after the melting of the micro-fuse and a striker wire (2) due to an overload current in the micro-fuse. An independent claim is also included for a transformer protection system comprising a fuse detection device.