Assessment of temperature influence on partial discharges in epoxy/mica insulation

The influence of temperature in epoxy/mica insulation system on the partial discharge (PD) parameters was examined. Particularly, the changes of 3D PD patterns were observed when the temperature rose to 135/spl deg/C. Possible causes of these changes are discussed taking into account different kinds of PD sources. The thermal stress influences the PD mechanism and accelerates the degrading process in insulation. This synergistic effect appears already in the initial stage of PD action. The increase of PD pulse magnitude and the PD number is observed. The resulting transition of PD patterns is analyzed.