Operating Mechanism Of Drop-out Fuses In Outdoor Power Distribution Systems

In power distribution lines, a device called "drop out type fuse" is used on the primary side of high-voltage overhead lines and transformers to facilitate rapid disconnection in the event of abnormal current. The structure of the dropout fuse of transformer mainly includes an insulating support, upper and lower contact systems, and a fuse tube.

Under normal power supply conditions, the fuse wire, under tension, firmly embeds the fuse tube into the contact structure, thus keeping the circuit closed. In the event of a short circuit or overload, the fuse wire melts rapidly. The electric arc generated inside the fuse tube heats and decomposes the medium inside the arc-extinguishing tube. High-temperature gas is ejected along the pipe, longitudinally blowing away the arc and extinguishing it. After the fuse wire melts, the upper and lower contacts lose their tension constraint. Under the action of gravity and springs, the fuse tube quickly falls, forming a clear break point, and the circuit is disconnected.

This design is relatively simple in construction, suitable for outdoor environments, and has good compatibility with power distribution lines and transformers. Especially in 10kV distribution networks, the expulsion drop out fuse is widely used, both for branch lines and transformer power supply circuits.