Some precautions for the field users of PDC measurement for transformer insulation condition assessment

The need for economic, reliable and effective delivery of electric power has lead to the search for new, efficient and effective methods for diagnosing the insulation of the HV equipments in the industries all over the world. One of the methods currently being investigated as a potential non-destructive diagnostic tool for condition monitoring of the oil-paper insulation of power transformers is the Polarisation and Depolarisation Current (PDC) measurement. This paper starts with a theoretical and physical description of the PDC technique. Several practical aspects of the technique have been discussed in the paper along with corresponding experimental and field test results. These physical considerations can be used as 'precautions' for the potential field users of the PDC technique for insulation condition assessment of transformers.