Mechanical Drop Out Fuse

A mechanical drop-out fuse is a device that protects power and electrical equipment. When a short circuit or overload occurs on the line, the fuse blows and cuts off the current, thereby protecting the circuit and equipment. It has the advantages of strong breaking capacity, easy replacement of fuse parts, safety and reliability.

Mechanical drop-out fuses are suitable for power systems with a frequency of 50HZ and a rated voltage of 35KV and below, and are installed on the high-voltage side of distribution transformers or main distribution lines.

The main function is where the protection performance requirements are not high. It can be used in conjunction with the isolating switch to replace the automatic air switch; it can also be used in conjunction with the load switch to replace the expensive circuit breaker. It also has short circuit protection, overload and isolation circuits. Simply put, when the current is greater than the set maximum current value, the fuse of the fuse is burned short, and the spring force and gravity will open the switch. During normal maintenance, the switch can be freely pulled closed and the fuse replaced.

The working principle of the drop-out fuse: The moving contacts at both ends of the fuse tube are fastened by the fuse (melt), and the upper moving contact is pushed into the "duckbill" protruding part. After the drop-out fuse is divided, the phosphor copper sheet, etc. The upper static contact is made to push the upper movable contact, so the fuse tube is firmly stuck in the "duckbill". When the short-circuit current blows through the fuse, an arc is generated. The steel paper tube lined with the fuse tube produces a large amount of gas under the action of the arc. Because the upper end of the fuse tube is sealed, the gas is ejected from the lower end, blowing out the arc. Because the fuse is blown, the upper and lower moving contacts of the fuse tube lose the fuse tightening force. Under the action of the fuse tube's own gravity and the upper and lower static contact springs, the fuse tube falls rapidly, causing the circuit to be disconnected. , remove the faulty section of line or faulty equipment. In the actual 10kV line system and the fuses on the distribution transformers cannot operate correctly, one of the reasons is that the electricians are of poor quality and have a weak sense of responsibility, and they do not maintain and repair drop-out fuses all year round; the second reason is that , the product quality of drop-out fuses is poor and cannot be flexibly pulled and closed. Two reasons reduce the functionality of drop-out fuses. In reality, there are often situations where there is a lack of fused pipe or melt, or copper wire, aluminum wire or even iron wire is used to replace the melt. The tripping rate of lines and the failure rate of distribution transformers remain high.

Drop-out fuse is the most commonly used short-circuit protection switch for 10kV distribution line branch lines and distribution transformers. The drop-out fuse is installed on the branch line of the 10kV distribution line, which can reduce the scope of power outage. Because it has an obvious disconnection point and functions as an isolating switch, it creates a safe working environment for the lines and equipment in the maintenance section. Installed on the distribution transformer, it can be used as the main protection of the distribution transformer.

The drop-out fuse is disconnected by the fuse wire in the fuse, so that the dynamic contacts above and below the fuse tube lose the tension of the fuse. Therefore, under the weight of the upper and lower static contact springs and itself, The fuse tube will fall down quickly, and the drop-out fuse will disconnect, thereby cutting off the faulty circuit or faulty equipment to protect them from short circuit or overload damage.

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