A short-circuit current is differentiated from an overload by the fact that the current is flowing outside of the normal path. These currents are also usually much larger than an overload and can cause significant damage in the form of thermal, magnetic, and arcing damage. Time is critical in the interruption of short circuits from the system.
The low level or ground fault is a form of short-circuit. However, these faults are difficult to detect and correct since the currents are relatively small. These faults are best prevented rather than corrected.
A current interrupting protective device (fused switch or circuit breaker) that operates to clear a short circuit should be examined before being reclosed to make sure that it has not been damaged. The forces developed during large short circuits can bend metal parts or crack insulation if the device has been stressed to the limits of its interrupting capacity. While it may have operated successfully to clear the fault, it might have been rendered incapable of doing so again. That is why the practice of reclosing a circuit breaker or a fused switch to see if the fault has burned itself clear is so dangerous. The device should be replaced if any sign of distortion or any unusual discoloration is seen, and any smell or smoke coming from the device should be investigated.
