A review of sulfur-hexafluoride reduction by dielectric coatings and alternative gases

Despite its technological superiority, there is a strong commitment to reduce the application of sulfur-hexafluoride due to its exceptionally high global warming potential. Its application was banned from all industries except the electric power industry, where no alternative with equivalent properties has been found. However, there are applications where it is possible to reduce its application. In case of gas insulated substations and lines, there are less critical factors then in case of switchgear, as only the good dielectric breakdown properties are required instead of the arc quenching capability. Two methods are reviewed in this article, which aim to reduce or eliminate the application of SF
₆
in gas insulated busbars and lines. The first method is the application of dielectric coatings on the surface of the high voltage or on the ground and high voltage electrodes. The solid layer forms a composite insulation system with the gaseous dielectric. It is assumed that these layers increase the breakdown voltage of the arrangement. The level of increment in case of various coating materials and application problems are reviewed. The second method is the application of alternative gases with or without mixing them with SF
₆
. The type of gases, mixtures and their performance are analyzed and presented in this article.