Composite fuse cutout is a electrical protection device for overhead line systems to prevent distribution transformers from being damaged by power surges. Fuse cutout insulators has a fuse link in series with the transformer feed cables. The link passes through a hinged tubular fuse holder in such a way that it secures the fuse holder in position on the cutout body. When the current exceeds a specified value for a period of time and fusing will melt by the heat generated by itself and separate under overcurrent conditions, the fuse holder will drop free under its own weight, pivot down on the hinge and hang vertically, giving a clear visual indication of its status. Most fuse cutout designs also incorporate a metal ring on the fuse holder, which allows maintenance and repair personnel to manually disconnect the fuse should they be required to work on the transformer. Cutout was widely used in high and low voltage power distribution systems and control systems, as well as electrical equipment, as short-circuit and over-current protectors, and are one of the most commonly used protection devices.