Searching for PD-based indexes able to infer the location of internal defects in insulation

The aim of this paper is to derive PD-based indexes and criteria that are able to indicate whether an internal defect, a cavity, is located close to the HV electrode, to the ground electrode, or in the bulk of the insulation. For this purpose, several measurement sessions were carried out on laboratory samples whose geometry was suitably designed (CIGRE type I and type II cell). In addition, measurements were performed on a capacitive insulator, having known location defects. The measurements results and their evaluation are described in the paper. It is shown that indexes useful for PD source location can be extracted from PD phase distributions.