| Summary: | The work reported in this thesis builds on research into electrical degradation of mica. The present work is concerned with the study of the deleterious mechanism of partial discharge (PD) induced surface and bulk disruption on mica. Many high voltage (HV) insulation systems incorporate composite materials containing mica as a matrix material. Mica, a naturally occurring mineral possesses attractive thermal, electrical, chemical and physical prope11ies, all highly desirable attributes for successful HV insulation. Investigation of electrical breakdown phenomena in dielectric media is unde11aken before proceeding to the mica - PD study which constitutes the major part of the work High grade Muscovite mica was selected for the experimental work; samples were exposed to four HV electrical stress regimes: AC point-plane, AC m1ificial voids, AC m1ificial vented voids and DC impulse with thermally stressed samples in an ambient air atmosphere. In addition the effect of electrode material and void environmental parameters were investigated. Following electrical stress application physical disruption was investigated using atomic force and scanning electron microscopy and chemically analysed using energy dispersive x-ray analysis. Changes in the structure of the samples were analysed in terms of the different gas breakdown mechanisms and variance in data generated from PD characteristics.
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