How Confident are we With Polarisation Based Diagnostics for Transformer Condition Assessment

Preventative diagnosis of transformers has become an important issue in recent times in order to improve the reliability of electric power systems. A number of diagnostic techniques such as Return Voltage (RV), Polarization/Depolarisation Current (PDC) and Dielectric Dissipation Factor (tan .) measurements at low frequency are currently available for practicing engineers. This paper outlines the summary of these techniques and a case study with all these measurements. Then the difficulties with the interpretation techniques are highlighted along with the recommendation of an expert system previously developed by the first author of this paper.

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