High Breaking Capacity fuses are widely used in the electric energy distribution systems. The theoretical and experimental studies are carried out within the framework of a collaboration with four industrial companies (Alstom, Electricity of France, Ferraz Shawmut, Schneider Electric) named GEFMT. The experimental work is interested with the determination of the physical quantities within the arc plasma (temperature, electron density, pressure, electrical conductivity), the time variation of the characteristic electrical parameters for the prearcing and the arcing periods (current, voltage, I².t, energy), the burn-back velocity and the fulgurite properties.
Cross viewing of the fulgurite obtained after the fuse working.
The experimental fuses are designed taking into consideration the specifities of an industrial fuse. They are made of a silver fuse strip linked to the two electrods, and the filling material whose properties are carefully controlled (silica sand).
During the fuse working, the energy brought the fault current is dissipated in the fuse element and in the silica sand. The fusion and the vaporization of the two chemical species (silver and quartz) lead to the plasma forming. The plasma emoitted radiation is studied by means of monoatomic emission spectroscopy :
Evolution versus time of the fuse plasma radiation for the spectral range focussed on 400 nm
Si II (2) multiplet lines observed at the end of the fuse working.
Temperature versus time (deduced from the Si II (1) (3) lines).
Electron density versus time (deduced from the Si II (2) lines).
From the calculation of the composition for a Ag_SiO2 plasma, we can deduce :
Ag_SiO2 plasma composition for the temperature range [1000-5000] K.