Experimental characterization of creeping discharges over solid/gas and solid/gas mixture interfaces under lightning impulse voltage
Résumé
The solid/gas insulating structures are present in various high voltage applications. The use of such structures enables to improve the dielectric strength of high voltage components and systems. And as any insulation, these structures are exposed to different stresses and particularly to the discharge phenomena. The propagation of discharges at the solid/gas interface can lead to the failure of the system. Thus, the knowledge of the initiation conditions of these discharges and the parameters characterizing their propagation up to flashover is of a great interest for the design and the dimensioning of high voltage apparatus and systems. This enables indeed an adequate choice of the kind and dimensions of the constituents of insulating structure. This paper deals with the experimental characterization of discharges propagating over solid insulators immersed in a gas or a gas mixture, under lightning impulse voltages (1,2/50 μs), using a point-plane electrode arrangement. It consists especially in the analyze of the morphology of discharges, their final lengths as well as the associated currents versus the amplitude and polarity of the voltage, the type and pressure of the gas (gas mixture), and the dimensions and type of insulator. Different kinds of insulators (glass, bakelite, Teflon ...), gases (N2, SF6, CO2) and gas mixtures of these gases are considered.