Experimental study of HBC fuses working at short and medium pre-arcing times

Pre-arcing stage is the first working step in high breaking capacity (HBC) fuse operation and affects the following step, namely, the arcing step. We have performed realistic HBC fuse tests for short ( 10 ms) pre-arcing times by varying the phase angle of the electrical fault (defined as the phase angle of the fault current once the supplied voltage is applied to the fuse) in the range from 0° to 160°, for two values of the power factor (cos φ ∼ 0.9 and cos φ ∼ 0.1). Experimental values of the pre-arcing time and the arcing time (t are ) are given for t prearc /t MC ? 1 to ∼4.2, and discussed from the energetic point of view by taking into account the inductive source term. The adiabatic assumption classically used in the modelling is also examined. The influence of the pre-arcing step on the arcing step is analysed by means of the Joule integral, the energy dissipated in the fuse and the mass and length of the fulgurite.