Abderrahmane Beroual

TL;DR: In this article, the authors present a critical review of the current understanding of streamer propagation in dielectric liquids in order to help define the direction of future research, and they show that the molecular structure has a significant effect on streamers propagation.

TL;DR: In this paper, the authors present computer simulation data for the effective permittivity (in the quasistatic limit) of a system composed of discrete inhomogeneities, embedded in a three-dimensional homogeneous matrix of permittivities.

TL;DR: In this article, the dielectric strength, electrostatic charging tendency (ECT), ageing stability, gassing tendency, heat transfer efficiency and stray gassing issue of mineral and silicone oils, synthetic and natural esters are analyzed and discussed.

Abstract: A new set-up, using a video camera, allowing easy and economical access to the velocity distribution of streamers is presented. Our study focuses on the behavior of negative streamers in a variety of liquids, either pure or containing ionic or non-ionic additives, in point-plane geometry. The propagation velocity distribution has always a more or less marked minimum, whatever the polarity and the shape of the streamer (bush-like or filamentary). Such a velocity distribution is similar to that of the field on a growing conducting sphere. There is generally a very close correlation between the shape and the velocity: the higher the velocity the more filamentary the streamer. This is still the case even when in the same liquid we have either subsonic or supersonic velocity. It is shown that the positive transient currents are also in favor of the model of the conducting sphere and not of a unique conducting filament even though there is evidence that the streamer is filamentary. Some of the theoretical models of streamer propagation already proposed are appraised, in particular that of Devins et al. which is thought to be the most accurate in describing experimental results. As concerns the initiation phase, the time lag until the appearance nce of the streamer dec, reases sharply when voltage is increased. This time lag also depends on space charge phenomena. Initiation voltages are always higher with positive polarity than for negative polarity for a series of tested simple or industrial liquids.

TL;DR: In this paper, the authors present an overview of the key research advances made in recent years in the quest to find eco-friendly gases to replace SF6 gas used in electrical gas insulated substations and equipment.