This results in a small rise in impedance which
is insufficient to give arc extinction, so the fuse is unable to interrupt the fault current.
The smallest value of fault current that a high-voltage fuse can safely interrupt is
known as the ‘minimum breaking current’ and the value of this is usually supplied by
the fuse-link manufacturer on request. Fuses that are subject to this low overcurrent
limitation are classed as ‘back-up fuses’ or in the USA as ‘partial range fuses’.