Comparative Study of Partial Discharge (PD) Signal Characteristics in Insulation Systems filled with Mineral and Ester Oil

The increasing environmental concerns have led to the use of ester oil as an insulating medium in transformers. Having been continuously subjected to electrical, thermal and mechanical stresses, an ester oil filled transformer may also exhibit Partial discharge (PD) phenomenon. It is thus necessary to investigate the suitability of existing PD analysis tools (mainly used for mineral oil filled transformers) for ester oil filled transformers. This paper extracts statistical parameters such as skewness, kurtosis and asymmetry from phase resolved PD (PRPD) diagrams constructed upon the PD signals obtained from ester oil filled insulation systems. It demonstrates that the extracted statistical parameters can be used as a fingerprint for classifying PD source in ester oil filled transformers.