Self-healing of aluminium metallized polypropylene films: a spectroscopic investigation

Metallized capacitors, under high DC voltage, suffer inhibited discharges named self-healing. Previous works have shown that the Joule effect due to the current pulse locally vaporized the metal and after some delay, i.e. a given vaporized area, the arc extinguishes. The duration of this phenomenon strongly diminishes with an increase of the applied interlayer pressure. The strong influence of this mechanical pressure might be explained by the generation of a plasma of high density that needs severe energetic condition to remain conductive. Spectroscopic analysis of the light emitted in the range 300-900 nm, by a confined or not confined self-healing, is presented in this paper. In particular, the shape of aluminium lines was shown to be strongly dependent on the mechanical pressure applied on the film. The physical parameters (temperature, density) of the plasma are deduced from a detailed studies of these emission lines. It is demonstrated the plasma density increases strongly (up to a factor of 150) with the mechanical pressure applied on the film.