Partial Discharges Measurements in Epoxy-Mica Insulation under Different Frequency Stresses

摘要

The behaviour of Epoxy-Mica Insulators under different stresses was determined by the measurement of the loss factor, but the experiences have shown that this is not enough to make some conclusions concerning the long time behaviour of the insulation systems. Therefore further investigations were made on Epoxy-Mica insulation systems under AC stress of different frequencies including sensitive PD measurements during the electrical ageing process of stator bars for 10 kV machines. In the context of those experiments diverse time patterns were selected for the purpose of the observation of possible changes into the insulation. The PD behaviour as well as the derivated quantities were recorded in order to get sensible parameter for the evaluation of the ageing of the material. The results of these experiments show, that despite of the exposure to multiple electrical stresses the insulation capability is less affected by the electrical stress than by the thermal or mechanical stress. However the deterioration that caused by electrical stress could be used in order to determine the endurance of the insulation's capability.