Definition of Drop-out Fuses
A drop-out fuse is a high-voltage, outdoor overcurrent protection device - commonly referred to in the industry as a "link" (or "cutout") - primarily used for short-circuit and overload protection on 10kV distribution lines and transformers. When a circuit fault occurs, the fuse element melts, causing the fuse tube to drop automatically. This creates a visible break in the circuit, interrupts the fault current, and ensures the safe operation of the power system.
Structural Composition of Drop-out Fuses
1. Fuse Tube: The outer layer consists of a phenolic paper tube or an epoxy-glass cloth tube. The interior is lined with gas-generating materials - such as vulcanized fiber (steel paper) or shellac-impregnated mulberry paper - which produce gas to extinguish the electric arc when the fuse element melts.
2. Fuse Element: Typically made of copper, silver, or a silver-copper alloy, the element features a variable cross-section design (a spiral structure for overload protection and an M-shaped "burst" notch for short-circuit protection). Once the element melts, it triggers the release of the fuse tube, causing it to drop.
3. Contact System: Comprising upper and lower stationary contacts (the upper one often featuring a "duckbill" shape) and corresponding moving contacts, the system is held in the closed position by spring pressure. When the fuse element melts, the contacts are released.
4. Insulator: Made of high-strength electrical porcelain or silicone rubber, the insulator supports the fuse tube and provides necessary electrical insulation.
5. Arc-Extinguishing Device: The inner wall of the fuse tube is coated with an arc-extinguishing agent. This, combined with a specialized vent design (such as an angled exhaust port), accelerates the extinction of the electric arc.