Recent Trends in Development of High Voltage Circuit Breakers with SF6 Alternative Gases

The available knowledge of state-of-the-art of SF6 alternative gases in switching applications was collected and evaluated in an initiative of the Current Zero Club together with CIGRE. The present contribution summarizes the main results of this activity and will also include the latest trends. The main properties and switching performance of new gases are compared to SF6. The most promising new gases are at the moment perfluoroketones and perfluoronitriles. Due to the high boiling point of these gases, in HV applications mixtures with CO2 are used. For MV insulation perfluoroketones are mixed with air, but also other combinations might be possible. The dielectric and switching performance of the mixtures, with mixing ratios that allow sufficiently low operating temperatures, is reported to be only slightly below SF6. Minor design changes or de-rating of switchgear are therefore necessary. Differences between the gas mixtures are mainly in the boiling point and the GWP

Fluoreszenzspektroskopische Bestimmung der Flußdichte von zerstäubtem Titan bei reinen und oxidierten Oberflächen

Laser-induced fluorescence (LIF) spectroscopy is customary used for the determination of the flux of ion-sputtered wall material. One of the key problems of this method is, that the fluorescenoe light emitted by the atoms is proportional only to the population density of that electronic state which is excited by the laser radiation. To obtain from the density of groundstate atoms the flux density $\varnothing = n_{1} \vec{v}$ the mean velocity $\vec{v}$ of the atoms has to be determined and to obtain the total flux density, the population of all of the electronic states has to be measured and to be summed up. We haue performed these measurements for titanium sputtered by a 1 keV argon ion beam under perpendicular incidence. lt the tarnet surface is free of adsorbates, the sputtered atoms are neutral and almost exclusively in the groundstate multiplett. This follows from a comparison of the absolute flux density ofthe groundstate obtained from a spectroscopic calibration of the fluorescence signals with the flux of target material obtained from the sputtering of a thin layer of titanium with known thickness. The turn flux measurements agree within $\pm$ 12 %. The systematic error is estimated to be ± 50 This estimate takes the real pulse shape and the spatial and spectral profile of the laser light into account and is supported by a numerical calculation. lf the surface is covered by oxygen, the Ar sputtering yield is reduced by a Factor of 5 - 7. The contribution of the atoms in the groundstate multiplett becomes as small as 8 .5 % of the total density. The low-lying metastable states and the titanium ions contribute up to 33 % and 12 %, respectively. The yield of Ti-Ions is small co€ipared to those values quotedin the literature. This discrepancy is explained by a partial reflection of- the Ti--ions at a positive space Charge potential in front of the target which is produced by the Ar-Iran beam itself due to its high flux density. About 50 % of the total flux of sputtered atoms is detected spectroscopically. We conclude that the other 50 % are ejected as molecules e. g. as TiO. In many cases it is not known if thesurface is clean or oxidized. This might impede the determination of the total flux significantly. However, it is possible by simple criterie to distinguish an oxidized from a clean surface. The population temperature of the finestructure levels of the groundstate e. g. is 1400 K instead of 700 K and alD of Ti I to that of the groundstate increases from 5 x 10$^{-3}$ for a clean surface to nearly 1 for a completelyoxidized surface. In order to supplement these results, we haue extended our investigat.ions to oblique incidence of the Ar-ion beam, todifferent target materials like Fe and Al and to different ions like helium and deuterium. The main conclusion is that in Bach rase only a minority of the sputtered atoms is in the groundstate, if the surface is oxidized. In contrast to this the Ti-atoms sputtered from a nitrogen or hydrogen covered surface are ejected mainly in the groundstate. The widths of the velocity distributions depend an theparticular gas and correlate with the binding energy of the ad sorbate. The principles developed herein haue been applied to thedetection of aluminium in the fusion plasma device Elmo-Bumpy-Torus in Dak Ridge (USA . The velocity distribution of the neutral Al-atoms has been measured and clearly shows that sputtering is the mein release rnechanism. The measured Al-flux-densities near the wall are in accord with those obtained from surface probes

Forma y función

Haga frío o calor, tiempo tormentoso o apacible, los interruptores de vacío han de resistir todo tipo de condiciones ambientales, tanto en interiores como a la intemperie. Las partículas de suciedad y polvo que se acumulan en el exterior de los mismos también son un peligro, ya que reducen el nivel de tensión soportado. Las corrientes de cortocircuitos y sobretensiones eléctricas, los golpes y vibraciones mecánicas se suman al "abuso" que han de sufrir estos dispositivos. ¿Cómo puede un fabricante satisfacer los requisitos de los clientes, que desean un dispositivo resistente a la degradación y que funcione correctamente incluso en condiciones extremas? La respuesta de ABB aplica una técnica innovadora consistente en encapsular el interruptor en resina epoxídica para formar un polo completo. Estos polos encapsulados, que no requieren mantenimiento durante toda su vida útil, son modulares y de diseño compacto y robusto. La técnica de encapsulado permite incluir también dispositivos de detección y medida, además de simplificar el manejo y la instalación del dispositivo. Nunca un interruptor de vacío ha estado protegido de un modo tan completo como en un polo encapsulado

Characteristics of a high current ion source operated with lithium

A low pressure arc ion source has been tested for operation with lithium. Currents up to 120 mA could be extracted through a multiple aperture extraction system at energies of 30 keV. The ion beam was neutralized up to 70 % in a charge exchange cell filled with lithium vapour. The beam divergence ranged from 20 to 25 mrad full angle deduced from the spatial distribution of the collision induced Li I resonance line. Current densities from 2 to 3 mA/cm 2 at a distance of 1.9 m from the source were measured either by laser induced fluorescence or with a Faraday cup