COMBINED STRESS DEGRADATION OF THERMAL DEGRADATION AND SURFACE DEGRADATION DUE TO DISCHARGE OF EPOXY MICACEOUS INSULATIONS.

The combined effects of thermal degradation of the epoxy micaceous insulation and surface degradation due to discharge is studied. It is established that the phenomena of thermal degradation and surface degradation due to discharge are dominated by the erosion degradation of the insulation and the relationship of the weight loss rate of the epoxy micaceous insulation plates to temperature and to partial discharge current I(dis) are examined. From the results it is also established that there is a relationship betweeen the logarithmic weight loss rate of epoxy micaceous plate and the reciprocal of absolute temperature that can be approximately plotted as a straight line bent near the temperature T// epsilon where the relative permittivity epsilon //r of the insulation begins to increase rapidly with temperature.