A fuse is connected in series in a power line. During normal operation, the buttoned fuse wire is mounted on the upper contact of the fuse tube and is pressed down by a pressure relief cap with a pressure plate. The fuse tail wire is pulled out through the fuse tube, twisting the ejector plate against the current and pressing it close to the nozzle, connecting with the lower contact. Under the torque of the ejector plate, the fuse wire remains taut and the moving joint is locked. When the fuse is in the closed position, the downward force of the upper stationary contact and the outward pushing force of the spring plate make the contact of the entire fuse more reliable.
When a fault occurs in the power system, the fault current quickly melts the fuse wire, generating an electric arc inside the fuse tube. The fuse tube generates a large amount of gas under the action of the arc. When the gas pressure exceeds a given value, the pressure relief cap opens along with the button, reducing the pressure inside the fuse tube. When the current crosses zero, a strong deionization effect is generated, extinguishing the arc. When the gas pressure does not exceed the given value, the pressure relief plate does not activate. When the current crosses zero, the strong deionized gas generated is ejected from the lower nozzle, and the ejector plate quickly pulls out the fuse tail wire, extinguishing the arc. After the fuse melts, the movable joint releases, and the fuse tube, under the pressure of the lower spring of the upper stationary contact and the effect of its own weight, falls rapidly, cutting off the circuit and forming a clear disconnection gap.