A study of the partial discharge mechanism during the aging of epoxy/mica insulation

The influence of multistress aging of an epoxy/mica insulation system on the partial discharge (PD) parameters is discussed. The thermal stress influences the PD mechanism and accelerates the degrading processes in the insulation. A decrease of the PD pulse magnitude and an increase of the number of small ones is observed. It means a transition of partial discharges to a high repetition form. Such a transition is illustrated and analysed by 3D phase resolved PD patterns. This synergistic effect of temperature appears already in the initial stage of the PD action. The mechanism of PD stability is also reported.