Partial discharge measurement for the investigation of solid insulation ageing [in electric machines]

The paper deals with the use of partial discharge (PD) measurements for the investigation of solid insulation ageing caused by voltage and temperature stress. Different insulating materials such as insulating foils, insulated wires, insulating tapes and flexible insulating sleeving used in manufacturing of electrical machines were tested. Partial discharge data collected during a certain recording time have been accumulated. Comparisons between degradation caused by voltage stress, degradation caused by thermal stress and degradation due to both factors are given and discussed.