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Contribution à l'étude des phénomènes de préclaquage dans les diélectriques liquides -Modèles de génération et de propagation des streamers,

Abstract : This work deals with the pre-breakdown and breakdown phenomena in the liquid dielectrics. It is shown that the initiation of streamers, in a point-plane electrode arrangement, is preceded by the generation of a gaseous phase (bubble) at the point electrode. This bubble results of a current pulse injection into the liquid when the applied voltage reaches a threshold value Us. This latter increases quasi-linearly with the pressure. The addition of a certain concentration of an electronic scavenger compound increases Us ; this indicates that the electronic processes are also present. The analysis of the bubble dynamics shows that two types of deformation of the liquid-bubble interface can occur: (i) an expansion or an implosion and (ii) alternative movements of expansion and/or implosion. According to the disturbance mode of the interface, different types of streamers can be initiated. The dielectric strength of liquid increases when adding a given optimal concentration of electronic scavenger compounds (Iodobenzene or carbon tetrachloride) and/or increasing the pressure. Therefore, while acting on the initiation voltage of streamers, one can improve the dielectric strength of liquid even though the streamer velocity is increased. By increasing the pressure, one can also increase dielectric strength of a liquid. A modeling of streamers by an equivalent electrical network enables to determine the structure of streamers as well as their physical characteristics: currents, electrical charges, power and energy injected, electric fields and potentials at their heads, velocity and mobility of charge carriers within the streamer, local viscosity and temperature. Keywords: Dielectric liquids, pre-breakdown and breakdown, bubble dynamics, streamers, initiation and propagation, dielectric strength, additives and pressure, modeling.
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Submitted on : Thursday, May 3, 2007 - 5:28:53 PM
Last modification on : Tuesday, March 30, 2021 - 4:20:04 PM
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  • HAL Id : tel-00144567, version 1


Thomas Aka-Ngnui. Contribution à l'étude des phénomènes de préclaquage dans les diélectriques liquides -Modèles de génération et de propagation des streamers,. Autre. Ecole Centrale de Lyon, 2000. Français. ⟨tel-00144567⟩



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