What is drop out fuse?
Drop out fuses and load drop out fuses are outdoor high-voltage protective devices. They are installed on the high-voltage side of distribution transformers or branch lines of distribution lines, used for short-circuit and overload protection as well as load current switching for transformers and lines.
The drop-out fuse consists of an insulating base, a fixed contact, a moving contact, and a fuse tube. The fixed contact is installed at both ends of the insulating support, and the moving contact is installed at both ends of the fuse tube. The fuse tube is composed of an inner arc extinguishing tube and an outer layer of phenolic paper tube or epoxy glass cloth tube. The load-drop-out fuse incorporates a spring-loaded auxiliary contact and an arc-extinguishing hood to enable the switching of load currents.
Working principle of drop out fuse
The drop-out fuse operates normally with the fuse tube closing position formed by the tension of the fuse wire. When a fault occurs in the system, the fault current rapidly melts the fuse wire, forming an electric arc. The arc-extinguishing tube is heated by the arc, releasing a large amount of gas, which creates high pressure inside the tube and forms a longitudinal blowout along the tube. The electric arc is rapidly elongated and extinguished. After the fuse wire melts, the lower moving contact loses tension and flips down, releasing the fuse tube from the lock, and causing the fuse tube to drop and form a clear open position.
When disconnecting the load, the insulated rod is used to pull the moving contact. At this point, the moving and static contacts are still in contact. Continuing to pull the moving contact with the insulated rod, the auxiliary contact rapidly separates, generating an electric arc between the auxiliary contacts. The electric arc is elongated in the arc extinguishing cover slot, while the arc extinguishing cover generates gas. When the current reaches zero, the electric arc is extinguished.
Technique data of drop out fuse
NDRW12 Series Drop-out Fuse 10-15KV
Rated Voltage:10-15KV
Rated Current:100A,200A
Breaking Current:8/10 kA
Power-frequency Withstand Voltage (kV): 40kV
Dimensions (cm) : 42×37×13.5
NDRW12 Series Drop-out Fuse 15-24KV
Rated Voltage:15-24KV
Rated Current:100A,200A
Breaking Current:10/12 kA
Power-frequency Withstand Voltage (kV): 45kV
Dimensions (cm) : 52×37×13.5
NDRW12 Series Drop-out Fuse 24-27KV
Rated Voltage:24-27KV
Rated Current:100A,200A
Breaking Current:10/12 kA
Power-frequency Withstand Voltage (kV): 45kV
Dimensions (cm) : 52×38×17
NDRW12 Series Drop-out Fuse 33-36KV
Rated Voltage:33-36KV
Rated Current:100A,200A
Breaking Current:10/12 kA
Power-frequency Withstand Voltage (kV): 45kV
Dimensions (cm) : 62×38×17
The application of drop out fuse
1、Protection of Transformers
Transformers are vital for adjusting voltage levels between high-voltage transmission lines and lower-voltage distribution lines. drop-out fuse cutout protect these transformers from currents exceeding their capacity, which can cause overheating and failure.
2、Line Protection
drop-out fuse cutouts safeguard distribution lines from overcurrents caused by faults like line-to-ground contacts or short circuits, ensuring a stable and reliable power supply.
3、Equipment Safety
Beyond transformers and lines, drop-out fuse cutouts are integral to protecting a variety of electrical equipment from overcurrent damage, thus ensuring longevity and reducing maintenance costs.
Precautions for drop out fuse cutout
1、Proper Sizing and Selection: Ensure correct sizing to match the system’s operating current and specific equipment protection needs.
2、Regular Inspections: Periodic checks for wear, damage, or contamination to maintain system integrity.
3、Safe Handling Practices: Only qualified personnel should handle high voltage fuses, using proper safety equipment and procedures.
4、Environmental Considerations: Installations should account for local conditions like temperature extremes and moisture to ensure reliable operation.
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