Switching Arc Characteristics at Load Currents in Air and a Fluoroketone–Air Mixture

Phasing out SF6 in high-voltage equipment has been set as a goal due to its high global warming potential, 25 200 times that of CO2. Alternative gases and technologies are being looked into. One of these alternative dielectric gases is a mixture of technical air and the fluoroketone C5F10O. The advantage of the fluoroketone mixture is its low global warming potential and high dielectric withstand voltage. In load break switches, understanding interactions between the gas and the arc occurring during current interruption is key to developing alternative solutions. In this article, we investigated the arc voltage and arc diameter in both air and air mixed with 7.5% fluoroketone at 1.3 bar for both free burning and quartz constricted arcs at three different current levels, namely, 300-, 600-, and 900-A rms, in order to form a base of comparison for further investigations of these gases. It was found that the arc voltages and, thus, cooling do not differ between the gases during the high-current phase, but is better in quartz constricted arc around the current zero crossing. The arc radius was experimentally determined to be different in different gases for the free burning configuration, which is not in accordance with the calculated values using the Lowke model. The addition of fluoroketone was found to increase the interruption performance due to it having a better dielectric recovery than air.