The high rupturing capacity (HRC) fuse has excellent current and energy limiting characteristics and is capable of reliable operation at high prospective rms symmetrical current fault levels (typically 80 kA at 400 V and 40 kA at 11 kV).
Fuses are available in ratings up to 1250 A at low voltages and, say, 100 A at 11kV, and normally packaged in cartridge format. The fuse operates very rapidly under short circuit fault conditions to disconnect the fault within the first
half cycle and therefore limit the prospective peak current.
The fuse element traditionally consists of a silver element. Recent research and development by some manufacturers has allowed copper to be used when problems of increased pre-arcing I2t, less pronounced eutectic alloying (‘M’)
effect and surface oxidation are overcome. In some cases the performance of the copper element fuses actually surpasses that of the silver types.
The silver or copper strip element is perforated or waisted at intervals to reduce power consumption and improve the tolerance to overloads .
The fuse operation consists of a melting and an arcing process. Under high fault currents the narrow sections heat up and melt. Arcing occurs across
the gaps until the arc voltage is so high that the current is forced to zero and the fuse link ruptures. The operation of a typical 100 A HRC-rated fuse under short circuit conditions .
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