An Efficient Procedure to Identify and Quantify New Molecules for Insulating Gas Mixtures

Abstract

Author(s):Franck, Christian M.; Dahl, Dominik A.; Rabie, M.; Haefliger, P.; Koch, M. Publication Date: 2014 Permanent Link:https://doi.org/10.3929/ethz-a-010881816 Originally published in:Contributions to plasma physics 54(1), http://doi.org/10.1002/ctpp.201300030 Rights / License:In Copyright -Non-Commercial Use Permitted This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH LibraryThis is the pre-peer reviewed version of the following article: In this contribution, a new procedure to systematically identify and quantify novel molecular gases with low global warming potential for application in high voltage insulation as gas mixtures is presented. The attention is focused on highly efficient procedures to be able to scan a large number of candidate gases. To identify new molecules, we derived an empirical correlation between the electric strength of a gas and certain molecular properties, like polarizability or dipole moment, which can be calculated by means of density functional theory. The swarm parameters of these pre-selected molecules in mixtures with buffer gases is then quantified, using a newly set-up Pulsed Townsend experiment. The setup operates with a high degree of automation to enable systematic evaluation of gas mixtures not to miss possible synergistic effects. Key element of this PT setup is a new photocathode that works with a high quantum efficiency and long lifetime even when exposed to reactive species during the measurements. Moreover, for an automated operation it is important to know precisely in which range the experiment can be operated, i.e. for example to know up to which electron density space charge effects can be neglected. Finally, the measured swarm parameters need to be translated into breakdown voltage strengths of different electrode arrangements and different applied voltage wave shapes. For this, a model of the the streamer to leader transition in SF6 will be applied to general strong electronegative gases in future studies.

Computational screening of new high voltage insulation gases with low global warming potential

“…Instead, they may be used as one component in a gas mixture. By this, the ES of a gas such as nitrogen might be significantly increased already by adding only small percentages of a strongly electron-attaching substance [34]. We note that the GWP is a quantity that is uncoupled from the initial gas release of electrical equipment.…”

Detailed precision and accuracy analysis of swarm parameters from a pulsed Townsend experiment

“…As the electric field could be influenced by space charge or excited species, it is important to check the laser intensity [44] and repetition rate. To ensure that prior pulses do not influence the following, the repetition rate was increased to its maximum of 40 Hz (requirement to operate the laser at stable power).…”

Electron attachment properties of c-C4F8O in different environments

“…Electron swarm parameters such as the effective ionization rate, the electron drift velocity and the electron diffusion coefficient are useful for modeling low temperature plasmas in general [4,5], and in particular for modelling non-thermal gas discharges and assessing the performance of an electronegative gas for high voltage insulation [6,7]. It is common practice to calculate the effective ionization rate by solving the electron Boltzmann equation [8], or by means of Monte-Carlo simulations [9,10].…”