Analysis of Phase Resolved Partial Discharge Patterns of Kraft Paper Insulation Impregnated in Transformer Mineral oil

Partial Discharge (PD) is referred as a small discharge that partially bridges the insulation over a s mall portion of its space. PD occurs because of small de fects in insulation such as void in solid and bubble in liquid Insulation. The power transformer uses both solid and liquid insulation in terms of Kraft paper for winding and oil for cooling vhich protects transformer for long life operation. The partial discharge defects in insulation need to be identified early in order to estimate and extend the life of transformer. In this paper partial discharge patterns of pigtail specimen (a model of transformer winding) is impregnated in liquid insulation (mineral oil) is discussed. The detection of PD in dielectric liquid required PD measuring system and Instrument with low background noise. A unique measuring setup was designed and calibrated as per IEC Standard. The high voltage stress is applied on the pigtail specimen continuously until specimen failure; simultaneously PD data are recorded with a ten second delay from one acquisition to another. The pulses appear like burst in liquid insulation are comprised of discrete variable high frequency pulses. These pulse burst occurrence is compared with the phase of the input wave and the acquired data is further investigated to study its behaviors.