Solid by-products of a CF3I–CO2 insulating gas mixtures on electrodes after lightning impulse breakdown

Abstract

This paper investigates the solid by-products of CF3 I–CO2 gas mixtures and their proposed use as an alternative insulation medium in gas insulated switchgear and lines. The deposited by-products of a 30%–70% CF3I–CO2 gas mixture are experimentally investigated using stainless steel, aluminium and copper contacts whilst a standard 50 kV lightning impulse is used to cause electrical breakdown in the gas mixture. Following breakdown, the accumulated by-products over the electrodes surface were examined using an imaging microscope and scanning electron microscope. This paper discusses the results of microscope analysis on the surface of the electrodes and explores the effects that the detected by-products could have on high voltage CF3I–CO2 gas insulated equipment.