A Comparison of the Optical Emission Spectra of Insulating Gases During Pulsed Discharge

The breakdown behavior of insulating gases above atmospheric pressures and electric fields approaching 1 MV/cm is studied using optical emission spectroscopy. Concern surrounding the environmental impacts of Sulfur Hexafluoride (SF6) has driven significant research into using more environmentally friendly insulating gases to replace SF6 for electrical distribution and pulsed power applications. One such gas is the perfluoronitrile Novec™ 4710 (C4F7N), which is capable of twice the DC holdoff voltage of SF6 at atmospheric pressure. Optical emission spectroscopy permits observation of the performance of a subject gas during electrical breakdown, offering the ability to identify decomposition products of the gas, as well as their internal energy distribution. In this work, the optical emission spectra of Novec™ 4710, and SF6 under pulsed electrical breakdown are presented and compared at above atmospheric pressures, and an overview of the apparatus used to acquire these spectra is provided. The effects of varying gas pressure and, thus, gap voltage are explored and observed; atomic decomposition products are compared to the available literature.