An analysis of improved gaseous insulating mixtures in practical systems

As transmission line voltages continue to go up, the need of better gaseous insulators has become more and more imminent. This research investigates the dielectric strengths of some improved gaseous insulating mixtures in small scale simulations of practical systems. Concentric cylinder geometries are used in this research to simulate underground transmission pipe lines. Knowledge of fundamental low-energy (mostly ≤ 10eV) electron-molecule interactions is being applied to the design of new improved gaseous dielectrics. It has been found that the electron attachment and slowing-down properties of dielectric gases/mixtures as a function of electron energy are very significant in designing gaseous insulators. Several binary gaseous systems (2-C₄F₆/N₂, c-C₄F_{8/N2, 2-C4F8/N2) have been tested and found to be superior to the breakdown strengths of SF6 mixtures. The properties of these practical systems such as the effects of surface roughness of electrodes, particle contaminants and electrode materials are also investigated.}