Drop fuse and pull load drop fuse are outdoor high-voltage protection appliances. It is installed on the high-voltage side of distribution transformer or on the branch line of distribution line. It is used as short-circuit, overload protection and opening and closing load current of transformer and line. The drop fuse is composed of an insulating support 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 arc suppression tube in the inner layer and a phenolic paper tube or epoxy glass cloth tube in the outer layer. The pull load drop fuse enhances the elastic auxiliary contact and arc extinguishing cover to open and close the load current.

During normal operation of drop fuse, the fuse tube forms a closed position after tensioning with the help of fuse. When the system breaks down, the fuse will fuse rapidly and form an arc when the fault current is. The arc suppression tube is heated by the arc and decomposes a large amount of gas. A high pressure is formed in the embassy and longitudinal blowing is formed along the pipeline. The arc is quickly elongated and extinguished. After the fuse is fused, the lower moving contact loses tension and turns down two times. Lock the machine, release the fuse tube, and the fuse tube falls to form an obvious breaking position. When the load needs to be pulled, use the insulating rod to pull the moving contact. At this time, the active and static contacts are still in contact. Continue to pull the contact with the insulating rod, and the auxiliary contact is also separated. An arc is generated between the auxiliary contacts. The arc is elongated in the slit of the arc extinguishing cover. At the same time, the arc extinguishing cover generates gas, which extinguishes the arc when the current crosses zero.

The outdoor drop out fuse is applicable to the power system with voltage and frequency of 35kV and below 50Hz. It is used as overload and short-circuit protection for transmission lines and power transformers. It is only used for opening and closing the rated load current, and the mechanical life is ≥ 2000 times.

• Applicable to the upper limit of 40°C and the lower limit of -30°C.
• The altitude shall not exceed 1000m, and the wind speed shall not be greater than 35m / s.
• The fuse is not applicable to the following places:
• 3.1 places with fuel or explosion hazards.
• 3.2 places with violent vibration or impact.
• 3.3 areas with different electrochemical gases and serious air pollution and smoke.

The fuse is composed of a base and an arc suppression device. The lower end of the arc extinguishing tube is equipped with a possible rotating spring support to always keep the fuse in a tense state, so as to ensure the self-locking of the arc extinguishing tube at the closing position. In the overload or short circuit between the line and the transformer, the fuse is blown and the fuse is quickly pulled out of the arc extinguishing tube. The arc extinguishing tube is designed as a step-by-step exhaust type to solve the contradiction between breaking large and small current on the same fuse.