The medium-voltage controllable fuse provides arc flash protection with a plug-in retrofit to existing medium-voltage fuses. The system is designed to mitigate the arc-flash hazard on the low-voltage side of a medium-voltage transformer. The fuse provides normal short-circuit and overload protection while having the capability to open on command. The fuse was developed in response to OSHA Code 29 CFR-1910 Subpart S, requiring employers to identify and analyze arc-flash hazards and provide adequate personal protective equipment.