Broad band optical absorption measurements in a low voltage circuit breaker

In order to investigate a low voltage circuit breaker (LVCB), a technique of broad band optical absorption spectroscopy (BB-OAS) was implemented, using an auxiliary radiation source developed in our laboratory. The use of a tunable laser as an auxiliary source is not suitable in this case because the medium inside a LVCB is transient and nonreproducible. BB-OAS allows diagnosis of zones of hot gas where emission in the visible light range is missing or very weak. In fact, it leads to the knowledge of the atomic or molecular spectral absorption coefficient of the medium, which is related to the concentration of the particles taking part in the absorption. When the absorption medium is an electric arc, its emission is added to the transmitted light of the auxiliary source. Thanks to a sophisticated optical system, the spectral transmission coefficient of the arc is successfully determined. Assuming local thermodynamic equilibrium, electron temperature and total particle concentration of several metallic atoms, coming from contacts and splitters, were deduced