Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Electrical Engineering


This paper treats with corona discharges at normal pressure and at room temperature in C_3 F_3 and air with the following electrode systems: ¾” diameter sphere to 1 ¾” diameter plane, point to 1 ¾” diameter plane, point to point, 1” diameter sphere to 1” square plane, superimposed on a 1 ¾” diameter plate, 3/4” square plane to ¾” square plane (crossed and uncrossed), and ½” square plane to 1 ¾” diameter plane. The main discussions are: breakdown strength of these gases, mechanism of breakdown, and field mapping with the electrode systems. For transformers and circuit breakers insulation is most important for designing purposes. For transformers, oil is used for cooling and insulating. For circuit breakers, oil or some gases can be used for the purpose of quenching the arc. For these purposes, if gases are used, they should have high dielectric strength, noninflammability, etc. this paper discusses the dielectric strength of two gases and the effect in breakdown kV with different electrode systems at various gap settings. Oscillographic patterns of corona bursts for various electrode systems for the two gases are shown. Field analysis is also studied as it gives the physical concept of the system when the initiations of breakdown are confined to a single region of field, such as coiledges, clamps, and other sharp-edged electrode systems. Corona discharges are the transitory, faintly luminous, and audible glows which can be observed in a discharge gap, near the sparking value. Breakdown value of the gas depends upon the dielectric strength of the gas. It also depends upon electrode configuration; that is, concentrations of the filed. C_3 F_8 has high dielectric strength; mainly, due to the electronegativity of the gas. Air has less, as it is a mixture of gases.

Library of Congress Subject Headings

Electric discharges through gases


Includes bibliographical references



Number of Pages



South Dakota State University