Estimation of the plasma’s particle densities during the arcing period of a high-voltage fuse

We report in this paper the results of the estimated number densities for the plasma species during the arcing period in a model sand-filled high-voltage fuse. The model fuse was energized at 6 kV, using synthetic test circuit, and a prospective current of 1.25 kA, 50 Hz, was passed through it. The arcing period has been investigated using spectroscopic means. The fuse arc is supposed to be composed of O I, O II, Si I, Si II and Si III particles. Using the estimated values of electron density and temperature, and assuming the plasma to be in Local Thermodynamic Equilibrium (LTE), Saha´s and Brunner equations are applied to determine the particle densities of ionized and neutral particles in the plasma. The model high-breaking capacity high-voltage fuse, under the given testing conditions, shows that its arc remains highly ionised throughout the arcing period.