INTRODUCTION OF HIGH VOLTAGE FUSE

High-voltage fuses are generally used in small-capacity power grids with a voltage lower than 35kV. When an overload or short circuit occurs in the system, the melt is blown due to overheating, thereby cutting off the line and protecting the power grid and electrical equipment. Its working principle is the same as that of low-voltage fuses. The fuses are the same.
High-voltage fuses are divided into two types: current-limiting and drop-out. The meaning of current limiting is to limit the short-circuit current to reach the maximum value, thereby breaking the line at a certain value before the maximum value of the short-circuit current, and reducing the harm of the short-circuit current to the line and electrical equipment.

1. Introduction of drop fuse
The insulating pillar plays the role of installation, fixation and insulation, and the material is ceramic. The melting tube plays the role of insulation and arc extinguishing. The outer layer is made of phenolic paper tube or epoxy glass cloth tube, and the inner layer is made of gas-generating material such as steel paper tube or shellac paper tube. Both ends of the melting tube are upper and lower contacts. The melt passes through the melting tube, one end is fixed on the lower contact, the other end is tightened on the pressure plate that can rotate around the axis, and the pressure plate is pressed on the spring steel sheet to form the upper contact. The fusion tube is fixed between the metal support and the duckbill. When installing, make the fuse tube and the vertical line an angle of 30°. After the melt is fused, the pressure plate rotates clockwise around the shaft under the action of the spring, the upper contact slips off the tongue of the duckbill cover, and the fuse tube rotates counterclockwise around the shaft 3 by its own gravity, hangs upside down on the support, and is said to fall. After the melt is blown and an arc is generated,
The heat of the arc makes the material on the inner wall of the melting tube produce gas, the pressure in the tube rises, the gas is ejected outward at a high speed, and the arc is blown longitudinally, and the arc is extinguished when the current crosses zero.
After the fuse tube falls, remove the fuse tube with an insulating hook rod and replace it with a new melt. After the fault is eliminated, push the fuse tube to the closing position.
The fuse is simple in structure and inexpensive. The disadvantage is that the breaking current is small, and when the melt is blown, the flame and metal residue are sprayed from the fuse tube to both ends.

2. Introduction of current-limiting fuse
The silver-plated copper wire is used as a fuse and wound in parallel on the ceramic core to form the entire melt. The fuse is soldered with tin balls, which utilizes the metallurgical effect, which can improve the problem that the contact temperature rises too high when the overload current is low, and the tin The ball has little effect on breaking the short circuit, because the short circuit time is very short. The fuse is made of ceramic material and filled with quartz sand as filler. Both ends of the fuse tube are copper caps as contacts.
When the melt is under the action of the fault current, it first fuses, and the small gap is broken down to generate an arc, and then the gap is gradually enlarged and the breakdown process occurs, until the recovery voltage no longer causes the gap to break down and the line is cut off. Due to the strong dissociation effect of quartz sand, the short-circuit current is cut off or limited before reaching the peak value, so it is called a current-limiting fuse.
When the current limiting fuse cuts off the line, the arc is extinguished in the sealed fuse tube, and is widely used in indoor power distribution devices. Due to the current limiting effect, the requirements for the dynamic and thermal stability of the electrical appliances in the circuit are reduced