Impulse studies on gaseous dielectrics

The ever increasing demand for electricity for industrial and public consumption and increased efficiency needed in higher voltage transmission, has brought about the need for better gaseous insulators. This thesis reports on investigations of the effect of lightning and switching overvoltages on some improved gaseous insulating mixtures on small scale simulations of practical systems. The dielectric strengths of all the gases/mixtures used in this work have been measured for highly nonuniform fields (point-plane geometry) to simulate nonuniform fields existing in the industrial application of dielectric gases. In the breakdown voltage as a function of pressure, there was a transition between direct-breakdown and corona-breakdown. It has been found that the electron ionization, attachment and slowing-down properties of dielectric gases/mixtures as a function of electron energy are very significant in designing gaseous insulators. Several binary and ternary gaseous systems (c-C₄F₈/SF₆,2-C₄F₈/SF₆c-C₄F₈/SF₆/N₂ and 2-C₄F₈/SF₆/N₂) have been tested and found to be superior in breakdown strength to SF₆.