Determining routes for the analysis of partial discharge signals derived from the field

This paper discusses the experience of the National Electric Energy Testing Research and Applications Center (NEETRAC) with condition assessment of medium voltage power distribution cable systems using Partial Discharge (PD) measurements. Specifically, the main goal is to address the issue of selection of the appropriate PD diagnostic features. A large number of features for which a physical basis can be described are selected for analysis. The features are investigated using data obtained from field and laboratory tests. The investigation shows that two traditional diagnostic features are not enough to classify samples that are prone to fail in a four-year time window. Subsequently, cluster variable analysis is performed for a considerable number of PD diagnostic features. The analysis enables significant feature elimination and reveals that at least seven different types of PD diagnostic features are needed to achieve an acceptable level of dissimilarity between features. Future work, conclusions and remarks are also discussed.