Why Expulsion Euses are the Backbone of High Voltage Protection？

In the realm of high voltage electrical systems, ensuring robust protection against faults is paramount. Among the protective devices available, expulsion fuses are vital for maintaining system integrity and safety.

What are expulsion fuses?

Expulsion fuses are a type of protective device used in high voltage systems to interrupt fault currents. They operate by expelling the arc created during a fault through a gas-producing mechanism, typically involving boric acid.

This process effectively extinguishes the arc and isolates the faulty section of the circuit. Expulsion fuses are known for their reliability and cost-effectiveness, making them a popular choice in various applications, including utility poles, substations, and industrial plants.

How do high voltage fuse cutout work?

The high voltage fuse cutout 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, 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.

What is the rating of a expulsion fuse?

The rating of a expulsion fuse refers to its ability to handle specific voltage and current levels. These ratings are crucial for ensuring that the fuse can effectively interrupt fault currents without damaging the electrical system. Typically, expulsion fuses are available in various ratings to accommodate different applications. Commonly, they range from a few kV to several tens of kV, with current ratings designed to match the specific requirements of the electrical system they protect.

What are the technical requirements before installing a expulsion fuse?

Before installing a drop out fuse, several technical requirements must be met to ensure optimal performance and safety:

1、Site Assessment

Evaluate the installation site for environmental factors such as humidity, temperature, and exposure to contaminants. Ensure the site meets the necessary safety standards.

2、Correct Sizing

Select a fuse with the appropriate voltage and current ratings for the specific application. Using the wrong size can result in inadequate protection or unnecessary interruptions.

3、Secure Mounting

Ensure that the fuse holder is securely mounted to a stable structure. The holder should be easily accessible for maintenance and inspection.

4、Connection Integrity

Verify that all electrical connections are tight and secure to prevent loose connections, which could cause arcing or overheating.

5、Regular Inspections

Plan for periodic inspections of the fuse and its components to identify and address any signs of wear, damage, or environmental impact.

What is the difference between current limiting fuse and expulsion fuse?

1、Operation Mechanism

Expulsion Fuses: Use a gas-producing mechanism to extinguish the arc. They expel the arc and gases outside the fuse body.

current limiting fuses: Contain the arc within the fuse body and limit the current by creating a high-resistance path. They operate faster and can interrupt higher fault currents with minimal energy let-through.

2、Applications

Expulsion Fuses: Ideal for outdoor and high voltage applications where visual indication of a blown fuse is beneficial.

Current Limiting Fuses: Commonly used in medium and low voltage systems where limiting the fault current is crucial to protect sensitive equipment.

3、Noise and Exhaust

Expulsion Fuses: Produce noise and exhaust gases during operation, which can be managed with exhaust control devices.

Current Limiting Fuses: Contain the arc and do not produce significant noise or exhaust, making them suitable for indoor applications.

Understanding the role and specifications of expulsion expulsion fuses is essential for anyone involved in high voltage electrical systems. These fuses offer reliable protection and clear fault indication, making them indispensable in maintaining system integrity.

By selecting the appropriate fuse ratings and adhering to technical requirements, you can ensure optimal performance and safety for your electrical infrastructure.