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2. Rigidité diélectrique d'un interface gaz–support avec contaminant métallique dans l'air sec et ses mélanges avec le SF6.
- Author
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Imano, Adolphe Moukengué
- Subjects
- *
ELECTRIC potential , *ELECTRODES , *GLOBAL warming , *GLOBAL temperature changes , *GREENHOUSE effect - Abstract
In this paper, we conduct a series of experiments aimed at analysing the dielectric properties of compressed dry air, and some SF6–air mixtures up to 700 kPa, under application of AC 50 Hz and lightning impulse (LI) 1.2 μs/50 μs voltage. The investigations were carried out by using a cylindrical spacer model with an adhering particle on the surface under homogenous field conditions. We measure the partial discharges (PD) propagation characteristics under LI voltage stress, as well as the PD inception voltage and the flashover voltage for the contaminated particle. We also investigate the surface charge accumulation on the spacer surface under contaminated particle conditions. The results of the experiments reveal the influence a conducting particle has on the determined flashover field strength, for SF6–air mixtures compared with pure, compressed dry air. This influence is discussed for different particle lengths, but also for three different particle positions in the gap. Pure dry air achieves a higher dielectric strength when the particle gets into contact with the high voltage electrode, under negative LI voltage stress. The same result is obtained for the SF6–air mixtures, when the particle is located in the middle of the gap, as floating electrode on the spacer surface. The reported results contribute to the improvement of the models of breakdown through the interface gas–solid isolator. The application of these models should offer the possibility for considering the use of dry air, or its mixtures with SF6 which, normally have a lower relative global warming potential than pure SF6.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
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3. Earth's Climate Response to a Changing Sun
- Author
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Katja Matthes, Thierry Dudok de Wit, Jean Lilensten, Collectif, Katja Matthes, Thierry Dudok de Wit, Jean Lilensten, and Collectif
- Subjects
- Climatic changes--Effect of solar activity on, Global temperature changes
- Abstract
For centuries, scientists have been fascinated by the role of the Sun in the Earth's climate system. Recent discoveries, outlined in this book, have gradually unveiled a complex picture, in which our variable Sun affects the climate variability via a number of subtle pathways, the implications of which are only now becoming clear. This handbook provides the scientifically curious, from undergraduate students to policy makers with a complete and accessible panorama of our present understanding of the Sun-climate connection. 61 experts from different communities have contributed to it, which reflects the highly multidisciplinary nature of this topic. The handbook is organised as a mosaic of short chapters, each of which addresses a specific aspect, and can be read independently. The reader will learn about the assumptions, the data, the models, and the unknowns behind each mechanism by which solar variability may impact climate variability. None of these mechanisms can adequately explain global warming observed since the 1950s. However, several of them do impact climate variability, in particular on a regional level.This handbook aims at addressing these issues in a factual way, and thereby challenge the reader to sharpen his/her critical thinking in a debate that is frequently distorted by unfounded claims.
- Published
- 2015
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