Influence of sand granulometry on electrical characteristics, temperature and electron density during high-voltage fuse arc extinction

Emission spectroscopy and the recording of the electrical characteristics are used to study the influence of the granulometric composition of the arc-quenching material. Six adjacent intervals of grain size are studied: each of them is 50 µm wide, and the upper limit of the global interval is lower than 1000 µm. The final dimensions of the fulgurite are found to be proportional to the granulometry. Concerning the electrical parameters, two groups are pointed out : the extinction time constant, the dissipated energy and the value decrease with the granulometry, whereas the maximum value of the arc voltage increases with the granulometry. The rate of decrease of the temperature depends on the time interval observed: at the beginning of the arcing period, the decrease is fastest for the smallest granulometric parameters; and during the last part of the arcing period the trend is reversed. At the beginning of the arcing period, the electron number density increase varies between 10E19 and 10E20 cm-3.ms-1. When the electric current decreases, the electron number density decreases exponentially with a time constant value ranging from 0.40 ms to 0.25 ms