An overcurrent protective device (OPD) safeguards wiring and equipment from thermal damage caused by overloads or short circuits. This category includes fuses, miniature circuit breakers, and large power breakers. They are coordinated in series so that the device closest to a fault operates first, isolating the problem while keeping the rest of the system energized.
The panelboard schedule requires an overcurrent protective device rated for 10 kA fault interruption.
Related terms
OPD
An abbreviation for overcurrent protective device, a component that breaks a circuit during excessive current flow.
Circuit breaker
A mechanical switching device capable of making, carrying and breaking currents under normal and fault conditions.
Fuse
A sacrificial protection device containing a conductive element that melts to safely break a circuit during an overcurrent event.
Selectivity
Arranging protection so only the device nearest a fault operates and the rest of the system stays in service.