Ignition of an electrical arc in a capillary: arc parameters in the initial period

Fuse-to-varistor current commutation offers considerable promise for easier and cheaper high fault current interruption in distribution systems. Commutation relies on the fast generation of high voltages by the fuse. The fuse arc ignition period has been examined, with an emphasis on expulsion fuses. In the paper, relationships between the energy of the fuse arc ignition, the arc pressure and the peak voltage are presented and compared with experimental data. It is demonstrated that the actual arc length, energy and pressure are all proportional to each other. The arc length was approximately determined using streak records available in the literature. During the ignition period it was found that the sum of the length of individual arcs increased as a function of the time squared. It was also established that the pressure rise in capillary confinements is due to vaporisation of the fuse element rather than the walls of the enclosure