Degradation of HV generator insulation under mechanical, electrical and thermal stresses

The results of aging experiments under combined electrical, mechanical (vibration), and thermal stresses on epoxy-bonded mica insulation are presented. Actual 11-kV machine coils designed for use in 1 MW rotating machines are used as the specimens. Both diagnostic and destructive tests were carried out to assess the amount of aging. It was observed that the incremental loss tangent and partial discharge energy per cycle increased monotonically with time of aging and that the dielectric strength fell monolithically, thus indicating a high degree of correlation between these properties.<
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