High-voltage fuses are the most commonly used short-circuit protection switches for 10kV distribution line branch lines and distribution transformers. It has the characteristics of economy, convenient operation and strong adaptability to outdoor environment. It is widely used on the primary side of 10kV distribution lines and distribution transformers as protection and equipment input and cutting operations. Installed on the branch line of 10kV power distribution line, can reduce the scope of power outage, because it has obvious disconnection points, has the function of isolating switch, creates a safe working environment for repairing lines and equipment, and increases the sense of safety of maintenance personnel . Installed on distribution transformers can be used as the main protection of distribution transformers, so it has been popularized in 10kV distribution lines and distribution transformers. Fuses can be divided into indoor and outdoor types.
(1) Indoor high voltage fuse:
The indoor fuse is a sealed tube fuse filled with quartz sand filler. When the melt is fused by overload current or short-circuit current, the metal vapor and free gas after arcing are subjected to high temperature and high pressure, sprayed into the gap between the quartz sand, and contact with the surface of the quartz sand to cool and solidify, reducing the evaporation of the melt The free gas and metal vapor caused the current to cross zero naturally, forcing the arc to extinguish. When the fuse is blown, the wire of the fuse spring is also broken at the same time, and the spring tube pops out. The indoor high-voltage tubular fuse has the characteristics of strong arc extinguishing ability, large breaking capacity, no free gas discharge when breaking the circuit, and intercepting overvoltage. It can be completely blown before the short-circuit current reaches the impact value, so this fuse has a current limiting function.
(2) Outdoor high-voltage fuse:
Outdoor fuses are used to protect 10kV power transformers and power lines. It is composed of a fixed support part, a movable fuse tube and a fuse, and the fixed support part is porcelain or composite insulator. Its working principle is: thread the fuse into the fuse tube, tighten both ends, so that the fuse is located above the middle of the fuse tube. Due to the tension of the fuse, the upper movable contact tilts upward perpendicular to the fuse tube, and the upper movable contact is pushed into the upper static contact with an insulating pull rod to form a closed state (closed state) and maintain this state. When the protected circuit fails and the fuse is blown by the fault current, an arc is formed. The arc extinguishing tube decomposes a large amount of gas under the high temperature action of the arc, so that the pressure in the tube increases sharply, and the gas is sprayed out at a high speed to form a powerful arc longitudinal blowing, so that the arc is quickly stretched and extinguished. At the same time, as the fuse is blown, the pulling force of the fuse disappears and the locking mechanism is released. Under the action of the elasticity and dead weight of the upper static contact, the fuse tube turns around the lower axis to form an obvious disconnection distance. Cut off the circuit, cut off the faulty line or faulty equipment.
