Selection of Robust Parameters for the Identification of Defects Supporting Partial Discharges in Solid Insulation Systems

The paper presents the results of investigations having the purpose of selecting parameters derived from partial discharge acquisitions for an accurate identification of defects in solid insulation systems. Partial discharge measurements are performed on Roebel bars with artificial defects, using different test setups and voltage levels. A wide range of parameters derived from partial-discharge height or phase distributions are analyzed to assess their ability to identify defects under different test conditions. To be selected for identification purposes, their values should vary in distinct ranges, each associated with a specific defect. These intervals must remain almost constant, changing the test conditions. If properly organized, parameters related to the shape of phase-resolved partial discharge patterns, the ratio of positive and negative discharge amplitudes, and the shape factor of the two-parameter Weibull function are suitable for identifying different PD sources.