Detecting Deterioration Stages in Epoxy Resins Specimens under Partial Discharge Process

This paper presents a novel analysis tool based on partial discharge (PD) pulses waveform to determinate deterioration process as the fault evolves carbonizing the insulating medium in epoxy resin specimens. The PD pulses were acquired in the laboratory under controlled conditions; specially designed specimens were tested with a tip-flat electrode configuration immersed in a thermostable polymer (epoxy resin). Then, in the processing step, all acquired PD pulses were characterized with the Shannon entropy, and its variations along the deterioration process were studied. It was observed that the dispersion of this quantity increases with the deterioration of the medium, which allowed identifying different deterioration stages. The evolution of the deterioration has a correlation with the appearance of a greater number of pulses, whose entropy values diverge from average value (close to 2). These new pulses were analyzed using signal processing tools. It was found that there are important differences in the spectral content of each family, in the time-scale characteristics and in the energy distribution of the same frequency bands corresponding to each pulses family. In this work, the deterioration of epoxy resin specimens was characterized throughout the modifications observed in the characteristics of PD pulses during the entire failure process. It could be verified that there is information about the deterioration of the medium contained in the characteristics of the analyzed pulses.