Insulation condition assessment of transformer bushings by means of polarisation/depolarisation current analysis

This paper presents some practical experience of polarisation/depolarisation current (PDC) analysis on a number of condenser bushings having three different insulation designs-oil impregnated paper (OIP), synthetic resin bonded paper (SRBP) and resin impregnated paper (RIP). It suggests methods for performing successful on-site measurement. The document contains PDC measurement results and evaluation results of main insulation C1 for each type of bushing. It proves that the sensitivity in detecting insulation aging of the PDC technique is better than the conventional 50 Hz test.