Influence de la nature et de l'état de conditionnement de l'électrode plane sur la décomposition de SF6 soumis à des décharges couronne de polarité négative

Abstract

L'influence du type du métal constituant l'électrode plane (aluminium, cuivre, acier inoxydable) sur la décomposition de SF6 (PSF6=300 kPa) sec (pas d'eau ajoutée ; ≃ 200 ppmv H2O) ou humide (2000 ppmv H2O) soumis à des décharges couronne (géométrie pointe-plan; tension continue de polarité négative ; $\bar{I}=25~\mu$A ; 0 < Q ≤10 C) a été mise en évidence en dosant les quantités des principaux sous-produits gazeux, SOF2, “SOF4+SO2F2”, S2F10, formés. Cette influence est d'autant plus nette que la valeur de la charge transportée et que le taux d'humidité du SF6 sont élevés. L'utilisation d'une électrode en aluminium favorise la formation du “SOF4 + SO2F2” et du S2F10, celle d'une électrode en acier inoxydable favorise par contre celle du SOF2. Les différences de composition de la phase gazeuse observées au cours d'un essai et selon le métal sont quasi totalement dues à la passivation de l'électrode plane en cours d'essai. L'utilisation d'électrodes vieillies entraîne une diminution de la formation de SOF2 mais augmente par contre celle du S2F10

Production of S₂F₁₀, S₂OF₁₀, and S₂O₂F₁₀ from Spark and Negative-Corona Discharges in SF₆ and SF₆/O₂ Gas Mixtures

“…12. Spark yields (energy rates-of-production) of S2OF10 in units of 10-11mol/J versus percent O2 concentration in SF6 at a total pressure of 100kPa and for a discharge dissipation energy Piemontesi and coworkers(15) is also consistent with results obtained by Belarbi and coworkers (13,14) and Sauers and coworkers. (16) A decrease in S2F10 yields with increasing H2O content was also observed for spark discharges.…”

“…Despite the fact that the linearity assumption cannot always be justified, (18) the production rates for these compounds are found to be in agreement with previously published results. (18,22,23) The relative insensitivity of the SOF2 and SO2F2 production rates to O2 content in SF6 is also consistent with earlier observations (18,22,13) and model predictions. (3) The compounds SOF2 and SO2F2, together with SOF4, are known to be the most abundant stable SF6 oxidation byproducts from corona discharges.…”

“…The failure to see significant S2OF10 formation in negative corona suggests that the density of SF5O radicals must be sufficiently low to rule out S2O2F10 formation by the process The removal of SF5 by processes (11)(12)(13)(14) undoubtedly contributes to the decline of S2F10 yield with increasing O2 concentration in both types of discharges.…”

“…In the present work, the dependences of S2F10 production from point-plane negative-glow corona discharges in SF6 on pressure, current, and electrode surface conditions were experimentally investigated and the results are compared with measured (12)(13)(14) and predicted(4) rates for S2F10 production from corona that have been reported previously. The production rates for S2F10, S2OF10, and S2O2F10 from both negative-glow corona and spark discharges were also measured for SF6/O2 mixtures containing up to 10% by volume of O2, and the results are compared with previous experimental results.…”

Decomposition of high-pressure (400 kPa) SF6and SF6/N2(10:90) mixtures submitted to negative or 50 Hz ac corona discharges in the presence of water vapour and/or oxygen

“…Moreover, a peak occurs in the production of (SF 4 +SOF 2 + SO 2 ) followed by its disappearance at high charge. It should be noted that this particular pattern of production occurred each time we used an aluminium or copper plane electrode [8,9,22] and was correlated to the increase in its passivation during the run [26] affecting the stability of SOF 2 in the cell during the discharge. With 0.3 and 0.5% water added to the mixture, the range of transported charge we were able to study was not large enough to determine the charge for which production of these compounds peaked.…”