Comparative Test Program Framework for Non-Sf₆ Switching Gases

Abstract

In recent years, significant achievements have been made with respect to the development of SF6-free gas insulated substations (GIS). In parallel, the interest in installing SF6-free GIS by utilities increased steadily and tenders for new substations or upgrades, which regularly also include alternative technologies. The excellent performance of SF6 was unequivocally accepted by all vendors and users so that the community became used to single technology solutions. This is no longer the case with alternative gas mixtures, and multiple technological solutions are available. However, from the present body of literature it is not possible to make a full and comparative evaluation of different alternative gas switchgear, i.e. circuit-breakers and disconnectors. Thus, the High-Voltage Laboratory of ETH Zürich started investigations and measurements of basic experiments that allow an unbiased comparison of properties of alternative gas mixtures relevant for switching. The two main purposes of these investigations are to define a set of measurements that allow an estimation and comparison of switching performance with different gas mixtures, independent of a specific interruption nozzle geometry, drive system, electrostatic design, and other design specific features, and to perform (some of) these measurements comparing pure SF6, with air, pure CO2, CO2/O2 mixture, and further specific gas mixtures that are currently proposed by manufacturers for SF6 replacement. The basic analysis behind the definition of measurements will be given in detail and the design principles of the chosen test devices and the derived test currents and diagnostics will be introduced. Test results themselves will not be given, rather they will be the subject of separate future publications.

Trifluoromethyl Fluorosulfonate (CF3OSO2F) and Trifluoromethoxy Sulfur Pentafluoride (CF3OSF5) – Two Gaseous Sulfur(VI) Compounds with Insulating Properties

“…À 10.5 °C. 19 F NMR (377 MHz, neat, external [D 6 ]acetone, 21 °C): δ (ppm) = 66.1 (m, 4F B , 2 J( 19 F B , 19 F A ) = 153.1 Hz, 4 J( 19 F B , 19 F CF ) = 10.0 Hz), 58.9 (m, 1F A , 2 J( 19 F A , 19 F B ) = 153.1 Hz, 4 J( 19 F A , 19 F CF ) = 1.4 Hz), À 59.5 (dquint, 3F, OCF 3 , 4 J( 19 F A , 19 F CF ) = 1.4 Hz, 4 J( 19 F B , 19…”

“…[3,18] In addition, they must be safe to use, harmless to the used infrastructure and facilitate a well-known industrial handling. [2,19] Furthermore, specific intrinsic and extrinsic properties are required, including basic chemical and physical properties like high dielectric strength (DS), low boiling point and suitable reactivity, including the formation of harmless by-products. [2,13,20] The required high dielectric strength depends on the ability to absorb free electrons and to form anions and thus on the compound-related electron affinity.…”

“…Accordingly, it is necessary for future dielectrics to be environmentally friendly by enabling a degradation of the compound in the atmosphere into harmless compounds [3,18] . In addition, they must be safe to use, harmless to the used infrastructure and facilitate a well‐known industrial handling [2,19] . Furthermore, specific intrinsic and extrinsic properties are required, including basic chemical and physical properties like high dielectric strength (DS), low boiling point and suitable reactivity, including the formation of harmless by‐products [2,13,20] .…”

Wear of the Arcing Contacts and Gas Under Free Burning Arc in SF$_{6}$ Alternatives

“…To answer some of these questions, the High Voltage Laboratory at ETH Zurich has launched a project with the aim of comparing available SF 6 gas alternatives. Planned research activities are shown in the publication by Franck et al [1].…”