Characterization of ageing in insulation systems by loss current

Research Project, 2014 – 2016

Ageing in insulation systems is traditionally studied in accelerated time-to-breakdown experiments. Correctly performed, such experiments yield an expected lifetime but very few details. In the cases where partial discharges are the primary cause of ageing, partial discharge (PD)detection has been tried as an alternative. This method gives, however, often surprising results - the discharges decrease initially and are then stable at a low level until shortly before the breakdown. PD detection does therefore not give a clear picture of the ageing process. A probable reason is that the deteriorating charge displacements not always are fast as required for PD detection. In this part project it is therefore intended to study the loss current that includes contributions both from fast and slow charge displacements. The technique is based on methods for dielectric response and has been tried earlier with interesting results in a few cases but need to be generalized and formalized.