The use of time intervals between consecutive discharges to characterize PD-sources

Pulse sequence analysis is a powerful tool to characterize defects that generate partial discharges. Usually, frequency distributions or scatter plots of sequence correlated parameters such as e.g. the external voltage differences ΔU between consecutive discharge events are used for diagnosis. In some cases, the analysis of the times of occurrence and especially the sequence of time-intervals Δt between consecutive discharge pulses may even be more efficient to characterize a defect or to differentiate between different defects. In the case of only a few discharge events per cycle of the applied voltage, the parameter ΔU is very efficient and allows to distinguish clearly whether the partial discharge signals are generated by only one or more local defects, information that is very helpful for a reliable diagnosis. Even with only one type of defect, a small change in the height of the measuring voltage may significantly influence the discharge phenomenon, resp. the measured date set. The analysis of the frequency distributions of the time differences Δt of consecutive discharge events and the elimination of ´multiple discharge pulses´ together with the use of the parameter ΔU/Δt reveal very useful additional information.