Using data from x-ray high speed imaging of arc lengthening under capacitor discharge

Although the fuse is one of oldest components of electrical engineering, its operating remains very complex because of the extreme rapidity of the phenomena and the fact that they take place in an opaque environment. Until now, engineers and researchers have only studied the fuse operation by indirect method, simulation or post mortem fuse state. But, a collaboration between mixed research units with the European Synchrotron for Research Facilities allowed filming the fuse operating by x-ray imaging. The method specification is to record the sequence with 5 million frames per second. The conductive material is thus observed to pass from a solid-liquid phase to an initiation of the plasma, thereby establishing the initial conditions of the arcing phase. The high speed films also permit to observe the lengthening of the arc in a few microseconds. The images can be synchronized with the voltage and the current, which makes it possible to return to the calculation of the electric field in function of time. Data analysis has been compared with simulation models and the separation of the curves prove the lack of knowledge of arc ignition phase due to the plasma which is out of its thermodynamic equilibrium.