EXPERIMENTAL INVESTIGATION OF LIGHTNING ARC USING OPTICAL DIAGNOSTICS

摘要

The plasma associated with the lightning arc is expected to have high temperature and high pressure, but accurate data is missing for this category of electric discharges. The lack of understanding is principally with respect to the transient phase of current, which can reach thousands of amperes in a few microseconds. In this paper, we present the work realized on an experimental setup which simulates in the laboratory an arc column subjected to a normative lightning current waveform of 100 kA peak. This device has been instrumented by high speed cameras to assess the characteristic sizes of the arc channel and to characterize the shockwave generated by the arc expansion. Optical emission spectroscopy measurements are also used to estimate thermodynamic properties of the plasma. The light emitted from the arc is collected by an optical system composed of an optical fibre bundle, allowing simultaneous measurements at different points of the plasma. From radiative profiles measured around the transition of ionic lines of nitrogen, we estimated several plasma parameters including the temperature, electronic density and pressure at the first microseconds of the arc lifetime.