Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Electrical Engineering


Gaseous insulation is at least as old as air itself. In the early days of the electrical industry air was depended upon extensively as an insulating medium. Air, in fact, is not too bad as an insulator and today it is still used for this purpose. Air is noninflammable, nonexplosive, plentiful and it has good dielectric characteristics. Over the years, however, there was a need for insulating mediums which had higher dielectric strength than air. Solid and liquid insulating mediums gained wide use because of the higher dielectric strengths. However, solid and liquid insulating mediums possessed some undesirable characteristics. Solids were heavy and bulky, and sometimes interfered with mechanical motion. At times, they also blocked the necessary heat dissipation from a device and readily transmitted noise. Some liquids created a fire hazard or large pressure surges on arcing. They too were heavy and good transmitters of noise. Gaseous insulation really began to make its mark as a useful insulating medium with the development of apparatus that had more stringent operating gradients. The need to insulate higher voltages with lighter and more compact equipment helped to encourage the use of gaseous insulation. Since there was a need for gaseous insulation, other gases were used in the place of air. Hydrogen was one such gas. It, of course, had the distinct disadvantage of being flammable as well as explosive. Nitrogen was another gas. It was a stable and inert gas, but its dielectric strength was slightly lower than that of air. Other gases such as neon, argon, xenon, helium, and krypton were used where spectral emission features were important. Recently, new gases have come into use as gaseous insulating mediums. These gases are the so-called electronegative gases. These gases have this name as a result of their apparent capacity to capture free electrons. Their molecules seem to have an affinity for free electrons and thus form heavy negative ions which are relatively immobile. Since free electrons are important in the formation of an arc, these gases have the property to prevent these arcs from occurring by capturing the necessary free electrons needed for the formation of the arc.

Library of Congress Subject Headings

Electronic discharges through gases


South Dakota State University Theses



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South Dakota State University